Option Explicit
'Niezbędne informacje:
'A/ Jednostki:
' - entalpia, h kJ/kg
' - entropia, s kJ/kgK
' - temperatura, t C
' - ciśnienie, p bar
'
'B/ Funkcje:
' - entalpia w funkcji ciśnienia i temperatury: h_pT(p,T)
' - entropia w funkcji ciśnienia i temperatury: s_pT(p,T)
' - stopień suchości pary w funkcji ciśnienia i entropii: x_ps(p,s)
' - entalpia w funkcji ciśnienia i entropii: h_ps(p,s)
' - entalpia pary nasyconej suchej w funkcji ciśnienia: hV_p(p)
' - entalpia wody nasyconej w funkcji temperatury: hL_t(t)
' - entalpia wody nasyconej w funkcji ciśnienia: hL_p(p)



'***********************************************************************************************************
'* Water and steam properties according to IAPWS IF-97                                                     *
'* By Magnus Holmgren, www.x-eng.com                                                                       *
'* The steam tables are free and provided as is.                                                           *
'* We take no responsibilities for any errors in the code or damage thereby.                               *
'* You are free to use, modify and distribute the code as long as authorship is properly acknowledged.     *
'* Please notify me at magnus@x-eng.com if the code is used in commercial applications                     *
'***********************************************************************************************************'
'
' The code is also avalibale for matlab at www.x-eng.com
'
'*Contents.
'*1 Calling functions
'*1.1
'*1.2 Temperature (T)
'*1.3 Pressure (p)
'*1.4 Enthalpy (h)
'*1.5 Specific Volume (v)
'*1.6 Density (rho)
'*1.7 Specific entropy (s)
'*1.8 Specific internal energy (u)
'*1.9 Specific isobaric heat capacity (Cp)
'*1.10 Specific isochoric heat capacity (Cv)
'*1.11 Speed of sound
'*1.12 Viscosity
'*1.13 Prandtl
'*1.14 Kappa
'*1.15 Surface tension
'*1.16 Heat conductivity
'*1.17 Vapour fraction
'*1.18 Vapour Volume Fraction
'
'*2 IAPWS IF 97 Calling functions
'*2.1 Functions for region 1
'*2.2 Functions for region 2
'*2.3 Functions for region 3
'*2.4 Functions for region 4
'*2.5 Functions for region 5
'
'*3 Region Selection
'*3.1 Regions as a function of pT
'*3.2 Regions as a function of ph
'*3.3 Regions as a function of ps
'*3.4 Regions as a function of hs
'*3.5 Regions as a function of p and rho
'
'4 Region Borders
'4.1 Boundary between region 1 and 3.
'4.2 Region 3. pSat_h and pSat_s
'4.3 Region boundary 1to3 and 3to2 as a functions of s
'
'5 Transport properties
'5.1 Viscosity (IAPWS formulation 1985)
'5.2 Thermal Conductivity (IAPWS formulation 1985)
'5.3 Surface Tension
'
'6 Units


'***********************************************************************************************************
'*1 Calling functions                                                                                      *
'***********************************************************************************************************

'***********************************************************************************************************
'*1.1


'***********************************************************************************************************
'*1.2 Temperature
Function Tsat_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p >= 0.000611657 And p <= 22.06395 + 0.001 Then '0.001 Added to enable the tripple point.
   Tsat_p = fromSIunit_T(T4_p(p))
 Else
   Tsat_p = CVErr(xlErrValue)
 End If
End Function
Function Tsat_s(ByVal s As Double) As Double
 s = toSIunit_s(s)
 If s > -0.0001545495919 And s < 9.155759395 Then
   Tsat_s = fromSIunit_T(T4_p(p4_s(s)))
 Else
   Tsat_s = CVErr(xlErrValue)
 End If
End Function

Function T_ph(ByVal p As Double, ByVal h As Double) As Double
 p = toSIunit_p(p)
 h = toSIunit_h(h)
 Select Case region_ph(p, h)
 Case 1
   T_ph = fromSIunit_T(T1_ph(p, h))
 Case 2
   T_ph = fromSIunit_T(T2_ph(p, h))
 Case 3
   T_ph = fromSIunit_T(T3_ph(p, h))
 Case 4
   T_ph = fromSIunit_T(T4_p(p))
 Case 5
   T_ph = fromSIunit_T(T5_ph(p, h))
 Case Else
  T_ph = CVErr(xlErrValue)
 End Select
End Function
Function T_ps(ByVal p As Double, ByVal s As Double) As Double
 p = toSIunit_p(p)
 s = toSIunit_s(s)
 Select Case region_ps(p, s)
 Case 1
   T_ps = fromSIunit_T(T1_ps(p, s))
 Case 2
   T_ps = fromSIunit_T(T2_ps(p, s))
 Case 3
   T_ps = fromSIunit_T(T3_ps(p, s))
 Case 4
   T_ps = fromSIunit_T(T4_p(p))
 Case 5
   T_ps = fromSIunit_T(T5_ps(p, s))
 Case Else
  T_ps = CVErr(xlErrValue)
 End Select
End Function
Function T_hs(ByVal h As Double, ByVal s As Double) As Double
 h = toSIunit_h(h)
 s = toSIunit_s(s)
 Select Case Region_hs(h, s)
 Case 1
   T_hs = fromSIunit_T(T1_ph(p1_hs(h, s), h))
 Case 2
   T_hs = fromSIunit_T(T2_ph(p2_hs(h, s), h))
 Case 3
   T_hs = fromSIunit_T(T3_ph(p3_hs(h, s), h))
 Case 4
   T_hs = fromSIunit_T(T4_hs(h, s))
 Case 5
   T_hs = CVErr(xlErrValue) 'Functions of hs is not implemented in region 5
 Case Else
   T_hs = CVErr(xlErrValue)
 End Select
End Function
'***********************************************************************************************************
'*1.3 Pressure (p)
Function psat_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t <= 647.096 And t > 273.15 Then
   psat_T = fromSIunit_p(p4_T(t))
 Else
   psat_T = CVErr(xlErrValue)
 End If
End Function
Function psat_s(ByVal s As Double) As Double
 s = toSIunit_s(s)
 If s > -0.0001545495919 And s < 9.155759395 Then
   psat_s = fromSIunit_p(p4_s(s))
 Else
   psat_s = CVErr(xlErrValue)
 End If
End Function
Function p_hs(ByVal h As Double, ByVal s As Double) As Double
 h = toSIunit_h(h)
 s = toSIunit_s(s)
 Select Case Region_hs(h, s)
 Case 1
   p_hs = fromSIunit_p(p1_hs(h, s))
 Case 2
   p_hs = fromSIunit_p(p2_hs(h, s))
 Case 3
   p_hs = fromSIunit_p(p3_hs(h, s))
 Case 4
   p_hs = fromSIunit_p(p4_T(T4_hs(h, s)))
 Case 5
   p_hs = CVErr(xlErrValue) 'Functions of hs is not implemented in region 5
 Case Else
  p_hs = CVErr(xlErrValue)
 End Select
End Function
Function p_hrho(ByVal h As Double, ByVal rho As Double) As Double
'*Not valid for water or sumpercritical since water rho does not change very much with p.
'*Uses iteration to find p.
  Dim High_Bound As Double
  Dim Low_Bound As Double
  Dim p As Double
  Dim rhos As Double
  High_Bound = fromSIunit_p(100)
  Low_Bound = fromSIunit_p(0.000611657)
  p = fromSIunit_p(10)
  rhos = 1 / v_ph(p, h)
  Do While Abs(rho - rhos) > 0.0000001
    rhos = 1 / v_ph(p, h)
    If rhos >= rho Then
      High_Bound = p
    Else
      Low_Bound = p
    End If
    p = (Low_Bound + High_Bound) / 2
    Loop
    p_hrho = p
End Function


'***********************************************************************************************************
'*1.4 Enthalpy (h)
Function hV_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
   hV_p = fromSIunit_h(h4V_p(p))
 Else
   hV_p = CVErr(xlErrValue)
 End If
End Function
Function hL_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
   hL_p = fromSIunit_h(h4L_p(p))
 Else
   hL_p = CVErr(xlErrValue)
 End If
End Function
Function hV_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  hV_T = fromSIunit_h(h4V_p(p4_T(t)))
 Else
  hV_T = CVErr(xlErrValue)
 End If
End Function
Function hL_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  hL_T = fromSIunit_h(h4L_p(p4_T(t)))
Else
  hL_T = CVErr(xlErrValue)
 End If
End Function

Function h_pT(ByVal p As Double, ByVal t As Double) As Double
 p = toSIunit_p(p)
 t = toSIunit_T(t)
 Select Case region_pT(p, t)
 Case 1
   h_pT = fromSIunit_h(h1_pT(p, t))
 Case 2
   h_pT = fromSIunit_h(h2_pT(p, t))
 Case 3
   h_pT = fromSIunit_h(h3_pT(p, t))
 Case 4
   h_pT = CVErr(xlErrValue)
 Case 5
   h_pT = fromSIunit_h(h5_pT(p, t))
 Case Else
  h_pT = CVErr(xlErrValue)
 End Select
End Function
Function h_ps(ByVal p As Double, ByVal s As Double) As Double
 Dim xs As Double
 p = toSIunit_p(p)
 s = toSIunit_s(s)
 Select Case region_ps(p, s)
 Case 1
   h_ps = fromSIunit_h(h1_pT(p, T1_ps(p, s)))
 Case 2
   h_ps = fromSIunit_h(h2_pT(p, T2_ps(p, s)))
 Case 3
   h_ps = fromSIunit_h(h3_rhoT(1 / v3_ps(p, s), T3_ps(p, s)))
 Case 4
   xs = x4_ps(p, s)
   h_ps = fromSIunit_h(xs * h4V_p(p) + (1 - xs) * h4L_p(p))
 Case 5
   h_ps = fromSIunit_h(h5_pT(p, T5_ps(p, s)))
 Case Else
  h_ps = CVErr(xlErrValue)
 End Select
End Function
Function h_px(ByVal p As Double, ByVal x As Double) As Double
 Dim hL As Double
 Dim hV As Double
 p = toSIunit_p(p)
 x = toSIunit_x(x)
 If x > 1 Or x < 0 Or p >= 22.064 Then
   h_px = CVErr(xlErrValue)
   Exit Function
 End If
 hL = h4L_p(p)
 hV = h4V_p(p)
 h_px = fromSIunit_h(hL + x * (hV - hL))
End Function
Function h_Tx(ByVal t As Double, ByVal x As Double) As Double
 Dim hL As Double
 Dim hV As Double
 Dim p As Double
 t = toSIunit_T(t)
 x = toSIunit_x(x)
 If x > 1 Or x < 0 Or t >= 647.096 Then
   h_Tx = CVErr(xlErrValue)
   Exit Function
 End If
 p = p4_T(t)
 hL = h4L_p(p)
 hV = h4V_p(p)
 h_Tx = fromSIunit_h(hL + x * (hV - hL))
End Function
Function h_prho(ByVal p As Double, ByVal rho As Double) As Double
  Dim hL, hV, vL, vV, x As Double
  p = toSIunit_p(p)
  rho = 1 / toSIunit_v(1 / rho)
  Select Case Region_prho(p, rho)
  Case 1
    h_prho = fromSIunit_h(h1_pT(p, T1_prho(p, rho)))
  Case 2
    h_prho = fromSIunit_h(h2_pT(p, T2_prho(p, rho)))
  Case 3
    h_prho = fromSIunit_h(h3_rhoT(rho, T3_prho(p, rho)))
  Case 4
   If p < 16.529 Then
     vV = v2_pT(p, T4_p(p))
     vL = v1_pT(p, T4_p(p))
   Else
     vV = v3_ph(p, h4V_p(p))
     vL = v3_ph(p, h4L_p(p))
    End If
    hV = h4V_p(p)
    hL = h4L_p(p)
  x = (1 / rho - vL) / (vV - vL)
  h_prho = fromSIunit_h((1 - x) * hL + x * hV)
 Case 5
   h_prho = fromSIunit_h(h5_pT(p, T5_prho(p, rho)))
 Case Else
   h_prho = CVErr(xlErrValue)
 End Select
End Function


'***********************************************************************************************************
'*1.5 Specific Volume (v)
Function vV_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   vV_p = fromSIunit_v(v2_pT(p, T4_p(p)))
  Else
   vV_p = fromSIunit_v(v3_ph(p, h4V_p(p)))
  End If
 Else
   vV_p = CVErr(xlErrValue)
 End If
End Function
Function vL_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   vL_p = fromSIunit_v(v1_pT(p, T4_p(p)))
  Else
   vL_p = fromSIunit_v(v3_ph(p, h4L_p(p)))
  End If
 Else
   vL_p = CVErr(xlErrValue)
 End If
End Function
Function vV_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   vV_T = fromSIunit_v(v2_pT(p4_T(t), t))
  Else
   vV_T = fromSIunit_v(v3_ph(p4_T(t), h4V_p(p4_T(t))))
  End If
 Else
   vV_T = CVErr(xlErrValue)
 End If
End Function
Function vL_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   vL_T = fromSIunit_v(v1_pT(p4_T(t), t))
  Else
   vL_T = fromSIunit_v(v3_ph(p4_T(t), h4L_p(p4_T(t))))
  End If
 Else
   vL_T = CVErr(xlErrValue)
 End If
End Function
Function v_pT(ByVal p As Double, ByVal t As Double) As Double
 p = toSIunit_p(p)
 t = toSIunit_T(t)
 Select Case region_pT(p, t)
 Case 1
   v_pT = fromSIunit_v(v1_pT(p, t))
 Case 2
   v_pT = fromSIunit_v(v2_pT(p, t))
 Case 3
   v_pT = fromSIunit_v(v3_ph(p, h3_pT(p, t)))
 Case 4
   v_pT = CVErr(xlErrValue)
 Case 5
   v_pT = fromSIunit_v(v5_pT(p, t))
 Case Else
  v_pT = CVErr(xlErrValue)
 End Select
End Function

Function v_ph(ByVal p As Double, ByVal h As Double) As Double
 Dim xs As Double
 Dim v4V As Double
 Dim v4L As Double
 p = toSIunit_p(p)
 h = toSIunit_h(h)
 Select Case region_ph(p, h)
 Case 1
   v_ph = fromSIunit_v(v1_pT(p, T1_ph(p, h)))
 Case 2
   v_ph = fromSIunit_v(v2_pT(p, T2_ph(p, h)))
 Case 3
   v_ph = fromSIunit_v(v3_ph(p, h))
 Case 4
   xs = x4_ph(p, h)
   If p < 16.529 Then
     v4V = v2_pT(p, T4_p(p))
     v4L = v1_pT(p, T4_p(p))
   Else
     v4V = v3_ph(p, h4V_p(p))
     v4L = v3_ph(p, h4L_p(p))
    End If
    v_ph = fromSIunit_v((xs * v4V + (1 - xs) * v4L))
 Case 5
   v_ph = fromSIunit_v(v5_pT(p, T5_ph(p, h)))
 Case Else
  v_ph = CVErr(xlErrValue)
 End Select
End Function
Function v_ps(ByVal p As Double, ByVal s As Double) As Double
 Dim xs As Double
 Dim v4V As Double
 Dim v4L As Double
 p = toSIunit_p(p)
 s = toSIunit_s(s)
 Select Case region_ps(p, s)
 Case 1
   v_ps = fromSIunit_v(v1_pT(p, T1_ps(p, s)))
 Case 2
   v_ps = fromSIunit_v(v2_pT(p, T2_ps(p, s)))
 Case 3
   v_ps = fromSIunit_v(v3_ps(p, s))
 Case 4
   xs = x4_ps(p, s)
   If p < 16.529 Then
     v4V = v2_pT(p, T4_p(p))
     v4L = v1_pT(p, T4_p(p))
   Else
     v4V = v3_ph(p, h4V_p(p))
     v4L = v3_ph(p, h4L_p(p))
    End If
    v_ps = fromSIunit_v((xs * v4V + (1 - xs) * v4L))
 Case 5
   v_ps = fromSIunit_v(v5_pT(p, T5_ps(p, s)))
 Case Else
   v_ps = CVErr(xlErrValue)
 End Select
End Function

'***********************************************************************************************************
'*1.6 Density (rho)
' Density is calculated as 1/v
Function rhoV_p(ByVal p As Double) As Double
  rhoV_p = 1 / vV_p(p)
End Function
Function rhoL_p(ByVal p As Double) As Double
  rhoL_p = 1 / vL_p(p)
End Function
Function rhoL_T(ByVal t As Double) As Double
  rhoL_T = 1 / vL_T(t)
End Function
Function rhoV_T(ByVal t As Double) As Double
  rhoV_T = 1 / vV_T(t)
End Function
Function rho_pT(ByVal p As Double, ByVal t As Double) As Double
  rho_pT = 1 / v_pT(p, t)
End Function
Function rho_ph(ByVal p As Double, ByVal h As Double) As Double
  rho_ph = 1 / v_ph(p, h)
End Function
Function rho_ps(ByVal p As Double, ByVal s As Double) As Double
  rho_ps = 1 / v_ps(p, s)
End Function

'***********************************************************************************************************
'*1.7 Specific entropy (s)
Function sV_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   sV_p = fromSIunit_s(s2_pT(p, T4_p(p)))
  Else
   sV_p = fromSIunit_s(s3_rhoT(1 / (v3_ph(p, h4V_p(p))), T4_p(p)))
  End If
 Else
   sV_p = CVErr(xlErrValue)
 End If
End Function
Function sL_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   sL_p = fromSIunit_s(s1_pT(p, T4_p(p)))
  Else
   sL_p = fromSIunit_s(s3_rhoT(1 / (v3_ph(p, h4L_p(p))), T4_p(p)))
  End If
 Else
   sL_p = CVErr(xlErrValue)
 End If
End Function
Function sV_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   sV_T = fromSIunit_s(s2_pT(p4_T(t), t))
  Else
   sV_T = fromSIunit_s(s3_rhoT(1 / (v3_ph(p4_T(t), h4V_p(p4_T(t)))), t))
  End If
 Else
   sV_T = CVErr(xlErrValue)
 End If
End Function
Function sL_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   sL_T = fromSIunit_s(s1_pT(p4_T(t), t))
  Else
   sL_T = fromSIunit_s(s3_rhoT(1 / (v3_ph(p4_T(t), h4L_p(p4_T(t)))), t))
  End If
 Else
   sL_T = CVErr(xlErrValue)
 End If
End Function
Function s_pT(ByVal p As Double, ByVal t As Double) As Double
 p = toSIunit_p(p)
 t = toSIunit_T(t)
 Select Case region_pT(p, t)
 Case 1
   s_pT = fromSIunit_s(s1_pT(p, t))
 Case 2
   s_pT = fromSIunit_s(s2_pT(p, t))
 Case 3
   s_pT = fromSIunit_s(s3_rhoT(1 / v3_ph(p, h3_pT(p, t)), t))
 Case 4
   s_pT = CVErr(xlErrValue)
 Case 5
   s_pT = fromSIunit_s(s5_pT(p, t))
 Case Else
  s_pT = CVErr(xlErrValue)
 End Select
End Function
Function s_ph(ByVal p As Double, ByVal h As Double) As Double
 Dim Ts As Double
 Dim xs As Double
 Dim s4V As Double
 Dim s4L As Double
 Dim v4V As Double
 Dim v4L As Double
 p = toSIunit_p(p)
 h = toSIunit_h(h)
 Select Case region_ph(p, h)
 Case 1
   s_ph = fromSIunit_s(s1_pT(p, T1_ph(p, h)))
 Case 2
   s_ph = fromSIunit_s(s2_pT(p, T2_ph(p, h)))
 Case 3
   s_ph = fromSIunit_s(s3_rhoT(1 / v3_ph(p, h), T3_ph(p, h)))
 Case 4
   Ts = T4_p(p)
   xs = x4_ph(p, h)
   If p < 16.529 Then
     s4V = s2_pT(p, Ts)
     s4L = s1_pT(p, Ts)
   Else
     v4V = v3_ph(p, h4V_p(p))
     s4V = s3_rhoT(1 / v4V, Ts)
     v4L = v3_ph(p, h4L_p(p))
     s4L = s3_rhoT(1 / v4L, Ts)
    End If
   s_ph = fromSIunit_s((xs * s4V + (1 - xs) * s4L))
 Case 5
   s_ph = fromSIunit_s(s5_pT(p, T5_ph(p, h)))
 Case Else
  s_ph = CVErr(xlErrValue)
 End Select
End Function
'***********************************************************************************************************
'*1.8 Specific internal energy (u)
Function uV_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   uV_p = fromSIunit_u(u2_pT(p, T4_p(p)))
  Else
   uV_p = fromSIunit_u(u3_rhoT(1 / (v3_ph(p, h4V_p(p))), T4_p(p)))
  End If
 Else
   uV_p = CVErr(xlErrValue)
 End If
End Function
Function uL_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   uL_p = fromSIunit_u(u1_pT(p, T4_p(p)))
  Else
   uL_p = fromSIunit_u(u3_rhoT(1 / (v3_ph(p, h4L_p(p))), T4_p(p)))
  End If
 Else
   uL_p = CVErr(xlErrValue)
 End If
End Function
Function uV_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   uV_T = fromSIunit_u(u2_pT(p4_T(t), t))
  Else
   uV_T = fromSIunit_u(u3_rhoT(1 / (v3_ph(p4_T(t), h4V_p(p4_T(t)))), t))
  End If
 Else
   uV_T = CVErr(xlErrValue)
 End If
End Function
Function uL_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   uL_T = fromSIunit_u(u1_pT(p4_T(t), t))
  Else
   uL_T = fromSIunit_u(u3_rhoT(1 / (v3_ph(p4_T(t), h4L_p(p4_T(t)))), t))
  End If
 Else
   uL_T = CVErr(xlErrValue)
 End If
End Function
Function u_pT(ByVal p As Double, ByVal t As Double) As Double
 p = toSIunit_p(p)
 t = toSIunit_T(t)
 Select Case region_pT(p, t)
 Case 1
   u_pT = fromSIunit_u(u1_pT(p, t))
 Case 2
   u_pT = fromSIunit_u(u2_pT(p, t))
 Case 3
   u_pT = fromSIunit_u(u3_rhoT(1 / v3_ph(p, h3_pT(p, t)), t))
 Case 4
   u_pT = CVErr(xlErrValue)
 Case 5
   u_pT = fromSIunit_u(u5_pT(p, t))
 Case Else
  u_pT = CVErr(xlErrValue)
 End Select
End Function
Function u_ph(ByVal p As Double, ByVal h As Double) As Double
 Dim Ts As Double
 Dim xs As Double
 Dim u4v As Double
 Dim u4L As Double
 Dim v4V As Double
 Dim v4L As Double
 p = toSIunit_p(p)
 h = toSIunit_h(h)
 Select Case region_ph(p, h)
 Case 1
   u_ph = fromSIunit_u(u1_pT(p, T1_ph(p, h)))
 Case 2
   u_ph = fromSIunit_u(u2_pT(p, T2_ph(p, h)))
 Case 3
   u_ph = fromSIunit_u(u3_rhoT(1 / v3_ph(p, h), T3_ph(p, h)))
 Case 4
   Ts = T4_p(p)
   xs = x4_ph(p, h)
   If p < 16.529 Then
     u4v = u2_pT(p, Ts)
     u4L = u1_pT(p, Ts)
   Else
     v4V = v3_ph(p, h4V_p(p))
     u4v = u3_rhoT(1 / v4V, Ts)
     v4L = v3_ph(p, h4L_p(p))
     u4L = u3_rhoT(1 / v4L, Ts)
   End If
   u_ph = fromSIunit_u((xs * u4v + (1 - xs) * u4L))
 Case 5
   Ts = T5_ph(p, h)
   u_ph = fromSIunit_u(u5_pT(p, Ts))
 Case Else
  u_ph = CVErr(xlErrValue)
 End Select
End Function
Function u_ps(ByVal p As Double, ByVal s As Double) As Double
 Dim x As Double
 Dim u4v, uLp, uVp, u4L As Double
 p = toSIunit_p(p)
 s = toSIunit_s(s)
 Select Case region_ps(p, s)
 Case 1
   u_ps = fromSIunit_u(u1_pT(p, T1_ps(p, s)))
 Case 2
   u_ps = fromSIunit_u(u2_pT(p, T2_ps(p, s)))
 Case 3
   u_ps = fromSIunit_u(u3_rhoT(1 / v3_ps(p, s), T3_ps(p, s)))
 Case 4
   If p < 16.529 Then
     uLp = u1_pT(p, T4_p(p))
     uVp = u2_pT(p, T4_p(p))
   Else
     uLp = u3_rhoT(1 / (v3_ph(p, h4L_p(p))), T4_p(p))
     uVp = u3_rhoT(1 / (v3_ph(p, h4V_p(p))), T4_p(p))
   End If
   x = x4_ps(p, s)
   u_ps = fromSIunit_u((x * uVp + (1 - x) * uLp))
 Case 5
   u_ps = fromSIunit_u(u5_pT(p, T5_ps(p, s)))
 Case Else
  u_ps = CVErr(xlErrValue)
 End Select
End Function
'***********************************************************************************************************
'*1.9 Specific isobaric heat capacity (Cp)
Function CpV_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   CpV_p = fromSIunit_Cp(Cp2_pT(p, T4_p(p)))
  Else
   CpV_p = fromSIunit_Cp(Cp3_rhoT(1 / (v3_ph(p, h4V_p(p))), T4_p(p)))
  End If
 Else
   CpV_p = CVErr(xlErrValue)
 End If
End Function
Function CpL_p(ByVal p As Double) As Double
 Dim t, h, v As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   CpL_p = fromSIunit_Cp(Cp1_pT(p, T4_p(p)))
  Else
  t = T4_p(p)
  h = h4L_p(p)
  v = v3_ph(p, h4L_p(p))

   CpL_p = fromSIunit_Cp(Cp3_rhoT(1 / (v3_ph(p, h4L_p(p))), T4_p(p)))
  End If
 Else
   CpL_p = CVErr(xlErrValue)
 End If
End Function
Function CpV_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   CpV_T = fromSIunit_Cp(Cp2_pT(p4_T(t), t))
  Else
   CpV_T = fromSIunit_Cp(Cp3_rhoT(1 / (v3_ph(p4_T(t), h4V_p(p4_T(t)))), t))
  End If
 Else
   CpV_T = CVErr(xlErrValue)
 End If
End Function
Function CpL_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   CpL_T = fromSIunit_Cp(Cp1_pT(p4_T(t), t))
  Else
   CpL_T = fromSIunit_Cp(Cp3_rhoT(1 / (v3_ph(p4_T(t), h4L_p(p4_T(t)))), t))
  End If
 Else
   CpL_T = CVErr(xlErrValue)
 End If
End Function
Function Cp_pT(ByVal p As Double, ByVal t As Double) As Double
 p = toSIunit_p(p)
 t = toSIunit_T(t)
 Select Case region_pT(p, t)
 Case 1
   Cp_pT = fromSIunit_Cp(Cp1_pT(p, t))
 Case 2
   Cp_pT = fromSIunit_Cp(Cp2_pT(p, t))
 Case 3
   Cp_pT = fromSIunit_Cp(Cp3_rhoT(1 / v3_ph(p, h3_pT(p, t)), t))
 Case 4
   Cp_pT = CVErr(xlErrValue)
 Case 5
   Cp_pT = fromSIunit_Cp(Cp5_pT(p, t))
 Case Else
  Cp_pT = CVErr(xlErrValue)
 End Select
End Function
Function Cp_ph(ByVal p As Double, ByVal h As Double) As Double
 p = toSIunit_p(p)
 h = toSIunit_h(h)
 Select Case region_ph(p, h)
 Case 1
   Cp_ph = fromSIunit_Cp(Cp1_pT(p, T1_ph(p, h)))
 Case 2
   Cp_ph = fromSIunit_Cp(Cp2_pT(p, T2_ph(p, h)))
 Case 3
   Cp_ph = fromSIunit_Cp(Cp3_rhoT(1 / v3_ph(p, h), T3_ph(p, h)))
 Case 4
   Cp_ph = CVErr(xlErrValue) '#Not def. for mixture"
 Case 5
   Cp_ph = fromSIunit_Cp(Cp5_pT(p, T5_ph(p, h)))
 Case Else
  Cp_ph = CVErr(xlErrValue)
 End Select
End Function
Function Cp_ps(ByVal p As Double, ByVal s As Double) As Double
 p = toSIunit_p(p)
 s = toSIunit_s(s)
 Select Case region_ps(p, s)
 Case 1
   Cp_ps = fromSIunit_Cp(Cp1_pT(p, T1_ps(p, s)))
 Case 2
   Cp_ps = fromSIunit_Cp(Cp2_pT(p, T2_ps(p, s)))
 Case 3
   Cp_ps = fromSIunit_Cp(Cp3_rhoT(1 / v3_ps(p, s), T3_ps(p, s)))
 Case 4
   Cp_ps = CVErr(xlErrValue) '#Not def. for mixture"
 Case 5
   Cp_ps = fromSIunit_Cp(Cp5_pT(p, T5_ps(p, s)))
 Case Else
  Cp_ps = CVErr(xlErrValue)
 End Select
End Function
'***********************************************************************************************************
'*1.10 Specific isochoric heat capacity (Cv)
Function CvV_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   CvV_p = fromSIunit_Cv(Cv2_pT(p, T4_p(p)))
  Else
   CvV_p = fromSIunit_Cv(Cv3_rhoT(1 / (v3_ph(p, h4V_p(p))), T4_p(p)))
  End If
 Else
   CvV_p = CVErr(xlErrValue)
 End If
End Function
Function CvL_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   CvL_p = fromSIunit_Cv(Cv1_pT(p, T4_p(p)))
  Else
   CvL_p = fromSIunit_Cv(Cv3_rhoT(1 / (v3_ph(p, h4L_p(p))), T4_p(p)))
  End If
 Else
   CvL_p = CVErr(xlErrValue)
 End If
End Function
Function CvV_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   CvV_T = fromSIunit_Cv(Cv2_pT(p4_T(t), t))
  Else
   CvV_T = fromSIunit_Cv(Cv3_rhoT(1 / (v3_ph(p4_T(t), h4V_p(p4_T(t)))), t))
  End If
 Else
   CvV_T = CVErr(xlErrValue)
 End If
End Function
Function CvL_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   CvL_T = fromSIunit_Cv(Cv1_pT(p4_T(t), t))
  Else
   CvL_T = fromSIunit_Cv(Cv3_rhoT(1 / (v3_ph(p4_T(t), h4L_p(p4_T(t)))), t))
  End If
 Else
   CvL_T = CVErr(xlErrValue)
 End If
End Function
Function Cv_pT(ByVal p As Double, ByVal t As Double) As Double
 p = toSIunit_p(p)
 t = toSIunit_T(t)
 Select Case region_pT(p, t)
 Case 1
   Cv_pT = fromSIunit_Cv(Cv1_pT(p, t))
 Case 2
   Cv_pT = fromSIunit_Cv(Cv2_pT(p, t))
 Case 3
   Cv_pT = fromSIunit_Cv(Cv3_rhoT(1 / v3_ph(p, h3_pT(p, t)), t))
 Case 4
   Cv_pT = CVErr(xlErrValue)
 Case 5
   Cv_pT = fromSIunit_Cv(Cv5_pT(p, t))
 Case Else
  Cv_pT = CVErr(xlErrValue)
 End Select
End Function
Function Cv_ph(ByVal p, ByVal h) As Double
 p = toSIunit_p(p)
 h = toSIunit_h(h)
 Select Case region_ph(p, h)
 Case 1
   Cv_ph = fromSIunit_Cv(Cv1_pT(p, T1_ph(p, h)))
 Case 2
   Cv_ph = fromSIunit_Cv(Cv2_pT(p, T2_ph(p, h)))
 Case 3
   Cv_ph = fromSIunit_Cv(Cv3_rhoT(1 / v3_ph(p, h), T3_ph(p, h)))
 Case 4
   Cv_ph = CVErr(xlErrValue) '#Not def. for mixture"
 Case 5
   Cv_ph = fromSIunit_Cv(Cv5_pT(p, T5_ph(p, h)))
 Case Else
  Cv_ph = CVErr(xlErrValue)
 End Select
End Function

Function Cv_ps(ByVal p As Double, ByVal s As Double) As Double
 p = toSIunit_p(p)
 s = toSIunit_s(s)
 Select Case region_ps(p, s)
 Case 1
   Cv_ps = fromSIunit_Cv(Cv1_pT(p, T1_ps(p, s)))
 Case 2
   Cv_ps = fromSIunit_Cv(Cv2_pT(p, T2_ps(p, s)))
 Case 3
   Cv_ps = fromSIunit_Cv(Cv3_rhoT(1 / v3_ps(p, s), T3_ps(p, s)))
 Case 4
   Cv_ps = CVErr(xlErrValue) '#Not def. for mixture
 Case 5
   Cv_ps = fromSIunit_Cv(Cv5_pT(p, T5_ps(p, s)))
 Case Else
  Cv_ps = CVErr(xlErrValue)
 End Select
End Function


'***********************************************************************************************************
'*1.11 Speed of sound
Function wV_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   wV_p = fromSIunit_w(w2_pT(p, T4_p(p)))
  Else
   wV_p = fromSIunit_w(w3_rhoT(1 / (v3_ph(p, h4V_p(p))), T4_p(p)))
  End If
 Else
   wV_p = CVErr(xlErrValue)
 End If
End Function
Function wL_p(ByVal p As Double) As Double
 p = toSIunit_p(p)
 If p > 0.000611657 And p < 22.06395 Then
  If p < 16.529 Then
   wL_p = fromSIunit_w(w1_pT(p, T4_p(p)))
  Else
   wL_p = fromSIunit_w(w3_rhoT(1 / (v3_ph(p, h4L_p(p))), T4_p(p)))
  End If
 Else
   wL_p = CVErr(xlErrValue)
 End If
End Function
Function wV_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   wV_T = fromSIunit_w(w2_pT(p4_T(t), t))
  Else
   wV_T = fromSIunit_w(w3_rhoT(1 / (v3_ph(p4_T(t), h4V_p(p4_T(t)))), t))
  End If
 Else
   wV_T = CVErr(xlErrValue)
 End If
End Function
Function wL_T(ByVal t As Double) As Double
 t = toSIunit_T(t)
 If t > 273.15 And t < 647.096 Then
  If t <= 623.15 Then
   wL_T = fromSIunit_w(w1_pT(p4_T(t), t))
  Else
   wL_T = fromSIunit_w(w3_rhoT(1 / (v3_ph(p4_T(t), h4L_p(p4_T(t)))), t))
  End If
 Else
   wL_T = CVErr(xlErrValue)
 End If
End Function
Function w_pT(ByVal p As Double, ByVal t As Double) As Double
 p = toSIunit_p(p)
 t = toSIunit_T(t)
 Select Case region_pT(p, t)
 Case 1
   w_pT = fromSIunit_w(w1_pT(p, t))
 Case 2
   w_pT = fromSIunit_w(w2_pT(p, t))
 Case 3
   w_pT = fromSIunit_w(w3_rhoT(1 / v3_ph(p, h3_pT(p, t)), t))
 Case 4
   w_pT = CVErr(xlErrValue)
 Case 5
   w_pT = fromSIunit_w(w5_pT(p, t))
 Case Else
  w_pT = CVErr(xlErrValue)
 End Select
End Function

Function w_ph(ByVal p As Double, ByVal h As Double) As Double
 p = toSIunit_p(p)
 h = toSIunit_h(h)
 Select Case region_ph(p, h)
 Case 1
   w_ph = fromSIunit_w(w1_pT(p, T1_ph(p, h)))
 Case 2
   w_ph = fromSIunit_w(w2_pT(p, T2_ph(p, h)))
 Case 3
   w_ph = fromSIunit_w(w3_rhoT(1 / v3_ph(p, h), T3_ph(p, h)))
 Case 4
   w_ph = CVErr(xlErrValue) '#Not def. for mixture
 Case 5
   w_ph = fromSIunit_w(w5_pT(p, T5_ph(p, h)))
 Case Else
  w_ph = CVErr(xlErrValue)
 End Select
End Function

Function w_ps(ByVal p As Double, ByVal s As Double) As Double
 p = toSIunit_p(p)
 s = toSIunit_s(s)
 Select Case region_ps(p, s)
 Case 1
   w_ps = fromSIunit_w(w1_pT(p, T1_ps(p, s)))
 Case 2
   w_ps = fromSIunit_w(w2_pT(p, T2_ps(p, s)))
 Case 3
   w_ps = fromSIunit_w(w3_rhoT(1 / v3_ps(p, s), T3_ps(p, s)))
 Case 4
   w_ps = CVErr(xlErrValue) '#Not def. for mixture
 Case 5
   w_ps = fromSIunit_w(w5_pT(p, T5_ps(p, s)))
 Case Else
  w_ps = CVErr(xlErrValue)
 End Select
End Function
'***********************************************************************************************************
'*1.12 Viscosity
Function my_pT(ByVal p As Double, ByVal t As Double) As Double
 p = toSIunit_p(p)
 t = toSIunit_T(t)
 Select Case region_pT(p, t)
 Case 4
   my_pT = CVErr(xlErrValue)
 Case 1, 2, 3, 5
   my_pT = fromSIunit_my(my_AllRegions_pT(p, t))
 Case Else
   my_pT = CVErr(xlErrValue)
 End Select
End Function
Function my_ph(ByVal p As Double, ByVal h As Double) As Double
 p = toSIunit_p(p)
 h = toSIunit_h(h)
 Select Case region_ph(p, h)
 Case 1, 2, 3, 5
   my_ph = fromSIunit_my(my_AllRegions_ph(p, h))
 Case 4
  my_ph = CVErr(xlErrValue)
 Case Else
  my_ph = CVErr(xlErrValue)
 End Select
End Function
Function my_ps(ByVal p As Double, ByVal s As Double) As Double
 my_ps = my_ph(p, h_ps(p, s))
End Function
'***********************************************************************************************************
'*1.13 Prandtl
Function Pr_pT(ByVal p As Double, ByVal t As Double) As Double
  Dim Cp As Double
  Dim my As Double
  Dim tc As Double
  Cp = toSIunit_Cp(Cp_pT(p, t))
  my = toSIunit_my(my_pT(p, t))
  tc = toSIunit_tc(tc_pT(p, t))
  Pr_pT = Cp * 1000 * my / tc
End Function
Function Pr_ph(ByVal p As Double, ByVal h As Double) As Double
  Dim Cp As Double
  Dim my As Double
  Dim tc As Double
  Cp = toSIunit_Cp(Cp_ph(p, h))
  my = toSIunit_my(my_ph(p, h))
  tc = toSIunit_tc(tc_ph(p, h))
  Pr_ph = Cp * 1000 * my / tc
End Function
'***********************************************************************************************************
'*1.14 Kappa
Function Kappa_pT(ByVal p As Double, ByVal t As Double) As Double
  Dim Cp As Double
  Dim Cv As Double
  Cp = Cp_pT(p, t)
  Cv = Cv_pT(p, t)
  Kappa_pT = Cp / Cv
End Function

Function Kappa_ph(ByVal p As Double, ByVal h As Double) As Double
  Dim Cp As Double
  Dim Cv As Double
  Cv = Cv_ph(p, h)
  Cp = Cp_ph(p, h)
  Kappa_ph = Cp / Cv
End Function
'***********************************************************************************************************
'*1.15 Surface tension
Function st_t(ByVal t As Double) As Double
  t = toSIunit_T(t)
  st_t = fromSIunit_st(Surface_Tension_T(t))
End Function
Function st_p(ByVal p As Double) As Double
   Dim t As Double
   t = Tsat_p(p)
   t = toSIunit_T(t)
   st_p = fromSIunit_st(Surface_Tension_T(t))
End Function
'***********************************************************************************************************
'*1.16 Thermal conductivity
Function tcL_p(ByVal p As Double) As Double
  Dim t As Double
  Dim v As Double
  t = Tsat_p(p)
  v = vL_p(p)
  p = toSIunit_p(p)
  t = toSIunit_T(t)
  v = toSIunit_v(v)
  tcL_p = fromSIunit_tc(tc_ptrho(p, t, 1 / v))
End Function
Function tcV_p(ByVal p As Double) As Double
  Dim t As Double
  Dim v As Double
  t = Tsat_p(p)
  v = vV_p(p)
  p = toSIunit_p(p)
  t = toSIunit_T(t)
  v = toSIunit_v(v)
  tcV_p = fromSIunit_tc(tc_ptrho(p, t, 1 / v))
End Function
Function tcL_T(ByVal t As Double) As Double
  Dim p, v As Double
  p = psat_T(t)
  v = vL_T(t)
  p = toSIunit_p(p)
  t = toSIunit_T(t)
  v = toSIunit_v(v)
  tcL_T = fromSIunit_tc(tc_ptrho(p, t, 1 / v))
End Function
Function tcV_T(ByVal t As Double) As Double
  Dim p, v As Double
  p = psat_T(t)
  v = vV_T(t)
  p = toSIunit_p(p)
  t = toSIunit_T(t)
  v = toSIunit_v(v)
  tcV_T = fromSIunit_tc(tc_ptrho(p, t, 1 / v))
End Function
Function tc_pT(ByVal p As Double, ByVal t As Double) As Double
  Dim v As Double
  v = v_pT(p, t)
  p = toSIunit_p(p)
  t = toSIunit_T(t)
  v = toSIunit_v(v)
  tc_pT = fromSIunit_tc(tc_ptrho(p, t, 1 / v))
End Function
Function tc_ph(ByVal p As Double, ByVal h As Double) As Double
  Dim v As Double
  Dim t As Double
  v = v_ph(p, h)
  t = T_ph(p, h)
  p = toSIunit_p(p)
  t = toSIunit_T(t)
  v = toSIunit_v(v)
  tc_ph = fromSIunit_tc(tc_ptrho(p, t, 1 / v))
End Function
Function tc_hs(ByVal h As Double, ByVal s As Double) As Double
  Dim p As Double
  Dim v As Double
  Dim t As Double
  p = p_hs(h, s)
  v = v_ph(p, h)
  t = T_ph(p, h)
  p = toSIunit_p(p)
  t = toSIunit_T(t)
  v = toSIunit_v(v)
  tc_hs = fromSIunit_tc(tc_ptrho(p, t, 1 / v))
End Function
'***********************************************************************************************************
'*1.17 Vapour fraction
Function x_ph(ByVal p As Double, ByVal h As Double) As Double
 p = toSIunit_p(p)
 h = toSIunit_h(h)
  If p > 0.000611657 And p < 22.06395 Then
    x_ph = fromSIunit_x(x4_ph(p, h))
  Else
    x_ph = CVErr(xlErrValue)
  End If
End Function
Function x_ps(ByVal p As Double, ByVal s As Double) As Double
 p = toSIunit_p(p)
 s = toSIunit_s(s)
  If p > 0.000611657 And p < 22.06395 Then
    x_ps = fromSIunit_x(x4_ps(p, s))
  Else
    x_ps = CVErr(xlErrValue)
  End If
End Function
'***********************************************************************************************************
'*1.18 Vapour Volume Fraction
Function vx_ph(ByVal p As Double, ByVal h As Double) As Double
 Dim vL As Double
 Dim vV As Double
 Dim xs As Double
 p = toSIunit_p(p)
 h = toSIunit_h(h)
 If p > 0.000611657 And p < 22.06395 Then
    If p < 16.529 Then
      vL = v1_pT(p, T4_p(p))
      vV = v2_pT(p, T4_p(p))
    Else
      vL = v3_ph(p, h4L_p(p))
      vV = v3_ph(p, h4V_p(p))
    End If
    xs = x4_ph(p, h)
    vx_ph = fromSIunit_vx((xs * vV / (xs * vV + (1 - xs) * vL)))
  Else
    vx_ph = CVErr(xlErrValue)
  End If
End Function
Function vx_ps(ByVal p As Double, ByVal s As Double) As Double
 Dim vL As Double
 Dim vV As Double
 Dim xs As Double
 p = toSIunit_p(p)
 s = toSIunit_s(s)
 If p > 0.000611657 And p < 22.06395 Then
    If p < 16.529 Then
      vL = v1_pT(p, T4_p(p))
      vV = v2_pT(p, T4_p(p))
    Else
      vL = v3_ph(p, h4L_p(p))
      vV = v3_ph(p, h4V_p(p))
    End If
    xs = x4_ps(p, s)
    vx_ps = fromSIunit_vx((xs * vV / (xs * vV + (1 - xs) * vL)))
  Else
    vx_ps = CVErr(xlErrValue)
  End If
End Function

'***********************************************************************************************************
'*2 IAPWS IF 97 Calling functions                                                                          *
'***********************************************************************************************************
'
'***********************************************************************************************************
'*2.1 Functions for region 1
Function v1_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'5 Equations for Region 1, Section. 5.1 Basic Equation
'Eqution 7, Table 3, Page 6
  Dim i As Integer
  Dim ps, tau, g_p As Double
  Dim I1, J1, n1 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  I1 = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 8, 8, 21, 23, 29, 30, 31, 32)
  J1 = Array(-2, -1, 0, 1, 2, 3, 4, 5, -9, -7, -1, 0, 1, 3, -3, 0, 1, 3, 17, -4, 0, 6, -5, -2, 10, -8, -11, -6, -29, -31, -38, -39, -40, -41)
  n1 = Array(0.14632971213167, -0.84548187169114, -3.756360367204, 3.3855169168385, -0.95791963387872, 0.15772038513228, -0.016616417199501, 8.1214629983568E-04, 2.8319080123804E-04, -6.0706301565874E-04, -0.018990068218419, -0.032529748770505, -0.021841717175414, -5.283835796993E-05, -4.7184321073267E-04, -3.0001780793026E-04, 4.7661393906987E-05, -4.4141845330846E-06, -7.2694996297594E-16, -3.1679644845054E-05, -2.8270797985312E-06, -8.5205128120103E-10, -2.2425281908E-06, -6.5171222895601E-07, -1.4341729937924E-13, -4.0516996860117E-07, -1.2734301741641E-09, -1.7424871230634E-10, -6.8762131295531E-19, 1.4478307828521E-20, 2.6335781662795E-23, -1.1947622640071E-23, 1.8228094581404E-24, -9.3537087292458E-26)
  ps = p / 16.53
  tau = 1386 / t
  g_p = 0#
  For i = 0 To 33
   g_p = g_p - n1(i) * I1(i) * (7.1 - ps) ^ (I1(i) - 1) * (tau - 1.222) ^ J1(i)
  Next i
 v1_pT = R * t / p * ps * g_p / 1000
End Function
Function h1_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'5 Equations for Region 1, Section. 5.1 Basic Equation
'Eqution 7, Table 3, Page 6
  Dim i As Integer
  Dim ps, tau, g_t As Double
  Dim I1, J1, n1 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  I1 = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 8, 8, 21, 23, 29, 30, 31, 32)
  J1 = Array(-2, -1, 0, 1, 2, 3, 4, 5, -9, -7, -1, 0, 1, 3, -3, 0, 1, 3, 17, -4, 0, 6, -5, -2, 10, -8, -11, -6, -29, -31, -38, -39, -40, -41)
  n1 = Array(0.14632971213167, -0.84548187169114, -3.756360367204, 3.3855169168385, -0.95791963387872, 0.15772038513228, -0.016616417199501, 8.1214629983568E-04, 2.8319080123804E-04, -6.0706301565874E-04, -0.018990068218419, -0.032529748770505, -0.021841717175414, -5.283835796993E-05, -4.7184321073267E-04, -3.0001780793026E-04, 4.7661393906987E-05, -4.4141845330846E-06, -7.2694996297594E-16, -3.1679644845054E-05, -2.8270797985312E-06, -8.5205128120103E-10, -2.2425281908E-06, -6.5171222895601E-07, -1.4341729937924E-13, -4.0516996860117E-07, -1.2734301741641E-09, -1.7424871230634E-10, -6.8762131295531E-19, 1.4478307828521E-20, 2.6335781662795E-23, -1.1947622640071E-23, 1.8228094581404E-24, -9.3537087292458E-26)
  p = p / 16.53
  tau = 1386 / t
  g_t = 0#
  For i = 0 To 33
   g_t = g_t + (n1(i) * (7.1 - p) ^ I1(i) * J1(i) * (tau - 1.222) ^ (J1(i) - 1))
  Next i
 h1_pT = R * t * tau * g_t
End Function
Function u1_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'5 Equations for Region 1, Section. 5.1 Basic Equation
'Eqution 7, Table 3, Page 6
  Dim i As Integer
  Dim tau, g_t, g_p As Double
  Dim I1, J1, n1 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  I1 = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 8, 8, 21, 23, 29, 30, 31, 32)
  J1 = Array(-2, -1, 0, 1, 2, 3, 4, 5, -9, -7, -1, 0, 1, 3, -3, 0, 1, 3, 17, -4, 0, 6, -5, -2, 10, -8, -11, -6, -29, -31, -38, -39, -40, -41)
  n1 = Array(0.14632971213167, -0.84548187169114, -3.756360367204, 3.3855169168385, -0.95791963387872, 0.15772038513228, -0.016616417199501, 8.1214629983568E-04, 2.8319080123804E-04, -6.0706301565874E-04, -0.018990068218419, -0.032529748770505, -0.021841717175414, -5.283835796993E-05, -4.7184321073267E-04, -3.0001780793026E-04, 4.7661393906987E-05, -4.4141845330846E-06, -7.2694996297594E-16, -3.1679644845054E-05, -2.8270797985312E-06, -8.5205128120103E-10, -2.2425281908E-06, -6.5171222895601E-07, -1.4341729937924E-13, -4.0516996860117E-07, -1.2734301741641E-09, -1.7424871230634E-10, -6.8762131295531E-19, 1.4478307828521E-20, 2.6335781662795E-23, -1.1947622640071E-23, 1.8228094581404E-24, -9.3537087292458E-26)
  p = p / 16.53
  tau = 1386 / t
  g_t = 0#
  g_p = 0#
  For i = 0 To 33
   g_p = g_p - n1(i) * I1(i) * (7.1 - p) ^ (I1(i) - 1) * (tau - 1.222) ^ J1(i)
   g_t = g_t + (n1(i) * (7.1 - p) ^ I1(i) * J1(i) * (tau - 1.222) ^ (J1(i) - 1))
  Next i
  u1_pT = R * t * (tau * g_t - p * g_p)
End Function
Function s1_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'5 Equations for Region 1, Section. 5.1 Basic Equation
'Eqution 7, Table 3, Page 6
  Dim i As Integer
  Dim g, g_t As Double
  Dim I1, J1, n1 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  I1 = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 8, 8, 21, 23, 29, 30, 31, 32)
  J1 = Array(-2, -1, 0, 1, 2, 3, 4, 5, -9, -7, -1, 0, 1, 3, -3, 0, 1, 3, 17, -4, 0, 6, -5, -2, 10, -8, -11, -6, -29, -31, -38, -39, -40, -41)
  n1 = Array(0.14632971213167, -0.84548187169114, -3.756360367204, 3.3855169168385, -0.95791963387872, 0.15772038513228, -0.016616417199501, 8.1214629983568E-04, 2.8319080123804E-04, -6.0706301565874E-04, -0.018990068218419, -0.032529748770505, -0.021841717175414, -5.283835796993E-05, -4.7184321073267E-04, -3.0001780793026E-04, 4.7661393906987E-05, -4.4141845330846E-06, -7.2694996297594E-16, -3.1679644845054E-05, -2.8270797985312E-06, -8.5205128120103E-10, -2.2425281908E-06, -6.5171222895601E-07, -1.4341729937924E-13, -4.0516996860117E-07, -1.2734301741641E-09, -1.7424871230634E-10, -6.8762131295531E-19, 1.4478307828521E-20, 2.6335781662795E-23, -1.1947622640071E-23, 1.8228094581404E-24, -9.3537087292458E-26)
  p = p / 16.53
  t = 1386 / t
  g = 0#
  g_t = 0#
  For i = 0 To 33
   g_t = g_t + (n1(i) * (7.1 - p) ^ I1(i) * J1(i) * (t - 1.222) ^ (J1(i) - 1))
   g = g + n1(i) * (7.1 - p) ^ I1(i) * (t - 1.222) ^ J1(i)
  Next i
  s1_pT = R * t * g_t - R * g
End Function
Function Cp1_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'5 Equations for Region 1, Section. 5.1 Basic Equation
'Eqution 7, Table 3, Page 6
  Dim i As Integer
  Dim G_tt As Double
  Dim I1, J1, n1 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  I1 = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 8, 8, 21, 23, 29, 30, 31, 32)
  J1 = Array(-2, -1, 0, 1, 2, 3, 4, 5, -9, -7, -1, 0, 1, 3, -3, 0, 1, 3, 17, -4, 0, 6, -5, -2, 10, -8, -11, -6, -29, -31, -38, -39, -40, -41)
  n1 = Array(0.14632971213167, -0.84548187169114, -3.756360367204, 3.3855169168385, -0.95791963387872, 0.15772038513228, -0.016616417199501, 8.1214629983568E-04, 2.8319080123804E-04, -6.0706301565874E-04, -0.018990068218419, -0.032529748770505, -0.021841717175414, -5.283835796993E-05, -4.7184321073267E-04, -3.0001780793026E-04, 4.7661393906987E-05, -4.4141845330846E-06, -7.2694996297594E-16, -3.1679644845054E-05, -2.8270797985312E-06, -8.5205128120103E-10, -2.2425281908E-06, -6.5171222895601E-07, -1.4341729937924E-13, -4.0516996860117E-07, -1.2734301741641E-09, -1.7424871230634E-10, -6.8762131295531E-19, 1.4478307828521E-20, 2.6335781662795E-23, -1.1947622640071E-23, 1.8228094581404E-24, -9.3537087292458E-26)
  p = p / 16.53
  t = 1386 / t
  G_tt = 0#
  For i = 0 To 33
   G_tt = G_tt + (n1(i) * (7.1 - p) ^ I1(i) * J1(i) * (J1(i) - 1) * (t - 1.222) ^ (J1(i) - 2))
  Next i
  Cp1_pT = -R * t ^ 2 * G_tt
End Function
Function Cv1_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'5 Equations for Region 1, Section. 5.1 Basic Equation
'Eqution 7, Table 3, Page 6
  Dim i As Integer
  Dim g_p, g_pp, g_pt, G_tt As Double
  Dim I1, J1, n1 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  I1 = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 8, 8, 21, 23, 29, 30, 31, 32)
  J1 = Array(-2, -1, 0, 1, 2, 3, 4, 5, -9, -7, -1, 0, 1, 3, -3, 0, 1, 3, 17, -4, 0, 6, -5, -2, 10, -8, -11, -6, -29, -31, -38, -39, -40, -41)
  n1 = Array(0.14632971213167, -0.84548187169114, -3.756360367204, 3.3855169168385, -0.95791963387872, 0.15772038513228, -0.016616417199501, 8.1214629983568E-04, 2.8319080123804E-04, -6.0706301565874E-04, -0.018990068218419, -0.032529748770505, -0.021841717175414, -5.283835796993E-05, -4.7184321073267E-04, -3.0001780793026E-04, 4.7661393906987E-05, -4.4141845330846E-06, -7.2694996297594E-16, -3.1679644845054E-05, -2.8270797985312E-06, -8.5205128120103E-10, -2.2425281908E-06, -6.5171222895601E-07, -1.4341729937924E-13, -4.0516996860117E-07, -1.2734301741641E-09, -1.7424871230634E-10, -6.8762131295531E-19, 1.4478307828521E-20, 2.6335781662795E-23, -1.1947622640071E-23, 1.8228094581404E-24, -9.3537087292458E-26)
  p = p / 16.53
  t = 1386 / t
  g_p = 0#
  g_pp = 0#
  g_pt = 0#
  G_tt = 0#
  For i = 0 To 33
   g_p = g_p - n1(i) * I1(i) * (7.1 - p) ^ (I1(i) - 1) * (t - 1.222) ^ J1(i)
   g_pp = g_pp + n1(i) * I1(i) * (I1(i) - 1) * (7.1 - p) ^ (I1(i) - 2) * (t - 1.222) ^ J1(i)
   g_pt = g_pt - n1(i) * I1(i) * (7.1 - p) ^ (I1(i) - 1) * J1(i) * (t - 1.222) ^ (J1(i) - 1)
   G_tt = G_tt + n1(i) * (7.1 - p) ^ I1(i) * J1(i) * (J1(i) - 1) * (t - 1.222) ^ (J1(i) - 2)
  Next i
  Cv1_pT = R * (-(t ^ 2 * G_tt) + (g_p - t * g_pt) ^ 2 / g_pp)
End Function
Function w1_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'5 Equations for Region 1, Section. 5.1 Basic Equation
'Eqution 7, Table 3, Page 6
  Dim i As Integer
  Dim g_p, g_pp, g_pt, G_tt, tau As Double
  Dim I1, J1, n1 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  I1 = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 8, 8, 21, 23, 29, 30, 31, 32)
  J1 = Array(-2, -1, 0, 1, 2, 3, 4, 5, -9, -7, -1, 0, 1, 3, -3, 0, 1, 3, 17, -4, 0, 6, -5, -2, 10, -8, -11, -6, -29, -31, -38, -39, -40, -41)
  n1 = Array(0.14632971213167, -0.84548187169114, -3.756360367204, 3.3855169168385, -0.95791963387872, 0.15772038513228, -0.016616417199501, 8.1214629983568E-04, 2.8319080123804E-04, -6.0706301565874E-04, -0.018990068218419, -0.032529748770505, -0.021841717175414, -5.283835796993E-05, -4.7184321073267E-04, -3.0001780793026E-04, 4.7661393906987E-05, -4.4141845330846E-06, -7.2694996297594E-16, -3.1679644845054E-05, -2.8270797985312E-06, -8.5205128120103E-10, -2.2425281908E-06, -6.5171222895601E-07, -1.4341729937924E-13, -4.0516996860117E-07, -1.2734301741641E-09, -1.7424871230634E-10, -6.8762131295531E-19, 1.4478307828521E-20, 2.6335781662795E-23, -1.1947622640071E-23, 1.8228094581404E-24, -9.3537087292458E-26)
  p = p / 16.53
  tau = 1386 / t
  g_p = 0#
  g_pp = 0#
  g_pt = 0#
  G_tt = 0#
  For i = 0 To 33
   g_p = g_p - n1(i) * I1(i) * (7.1 - p) ^ (I1(i) - 1) * (tau - 1.222) ^ J1(i)
   g_pp = g_pp + n1(i) * I1(i) * (I1(i) - 1) * (7.1 - p) ^ (I1(i) - 2) * (tau - 1.222) ^ J1(i)
   g_pt = g_pt - n1(i) * I1(i) * (7.1 - p) ^ (I1(i) - 1) * J1(i) * (tau - 1.222) ^ (J1(i) - 1)
   G_tt = G_tt + n1(i) * (7.1 - p) ^ I1(i) * J1(i) * (J1(i) - 1) * (tau - 1.222) ^ (J1(i) - 2)
  Next i
  w1_pT = (1000 * R * t * g_p ^ 2 / ((g_p - tau * g_pt) ^ 2 / (tau ^ 2 * G_tt) - g_pp)) ^ 0.5
End Function
Function T1_ph(ByVal p As Double, ByVal h As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'5 Equations for Region 1, Section. 5.1 Basic Equation, 5.2.1 The Backward Equation T ( p,h )
'Eqution 11, Table 6, Page 10
  Dim i As Integer
  Dim t As Double
  Dim I1, J1, n1 As Variant
  I1 = Array(0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 2, 2, 3, 3, 4, 5, 6)
  J1 = Array(0, 1, 2, 6, 22, 32, 0, 1, 2, 3, 4, 10, 32, 10, 32, 10, 32, 32, 32, 32)
  n1 = Array(-238.72489924521, 404.21188637945, 113.49746881718, -5.8457616048039, -1.528548241314E-04, -1.0866707695377E-06, -13.391744872602, 43.211039183559, -54.010067170506, 30.535892203916, -6.5964749423638, 9.3965400878363E-03, 1.157364750534E-07, -2.5858641282073E-05, -4.0644363084799E-09, 6.6456186191635E-08, 8.0670734103027E-11, -9.3477771213947E-13, 5.8265442020601E-15, -1.5020185953503E-17)
  h = h / 2500
  t = 0#
  For i = 0 To 19
   t = t + n1(i) * p ^ I1(i) * (h + 1) ^ J1(i)
  Next i
  T1_ph = t
End Function
Function T1_ps(ByVal p As Double, ByVal s As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'5 Equations for Region 1, Section. 5.1 Basic Equation, 5.2.2 The Backward Equation T ( p, s )
'Eqution 13, Table 8, Page 11
  Dim i As Integer
  Dim I1, J1, n1 As Variant
  I1 = Array(0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 4)
  J1 = Array(0, 1, 2, 3, 11, 31, 0, 1, 2, 3, 12, 31, 0, 1, 2, 9, 31, 10, 32, 32)
  n1 = Array(174.78268058307, 34.806930892873, 6.5292584978455, 0.33039981775489, -1.9281382923196E-07, -2.4909197244573E-23, -0.26107636489332, 0.22592965981586, -0.064256463395226, 7.8876289270526E-03, 3.5672110607366E-10, 1.7332496994895E-24, 5.6608900654837E-04, -3.2635483139717E-04, 4.4778286690632E-05, -5.1322156908507E-10, -4.2522657042207E-26, 2.6400441360689E-13, 7.8124600459723E-29, -3.0732199903668E-31)
  T1_ps = 0#
  For i = 0 To 19
   T1_ps = T1_ps + n1(i) * p ^ I1(i) * (s + 2) ^ J1(i)
  Next i
End Function
Function p1_hs(ByVal h As Double, ByVal s As Double) As Double
'Supplementary Release on Backward Equations for Pressure as a Function of Enthalpy and Entropy p(h,s) to the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
'5 Backward Equation p(h,s) for Region 1
'Eqution 1, Table 2, Page 5
  Dim i As Integer
  Dim p As Double
  Dim I1, J1, n1 As Variant
  I1 = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 3, 4, 4, 5)
  J1 = Array(0, 1, 2, 4, 5, 6, 8, 14, 0, 1, 4, 6, 0, 1, 10, 4, 1, 4, 0)
  n1 = Array(-0.691997014660582, -18.361254878756, -9.28332409297335, 65.9639569909906, -16.2060388912024, 450.620017338667, 854.68067822417, 6075.23214001162, 32.6487682621856, -26.9408844582931, -319.9478483343, -928.35430704332, 30.3634537455249, -65.0540422444146, -4309.9131651613, -747.512324096068, 730.000345529245, 1142.84032569021, -436.407041874559)
  h = h / 3400
  s = s / 7.6
  p = 0#
  For i = 0 To 18
   p = p + n1(i) * (h + 0.05) ^ I1(i) * (s + 0.05) ^ J1(i)
  Next i
  p1_hs = p * 100
End Function
Function T1_prho(ByVal p As Double, ByVal rho As Double) As Double
  'Solve by iteration. Observe that fo low temperatures this equation has 2 solutions.
  'Solve with half interval method
  Dim i As Integer
  Dim Ts, Low_Bound, High_Bound, rhos As Double
  Low_Bound = 273.15
  High_Bound = T4_p(p)
  Do While Abs(rho - rhos) > 0.00001
    Ts = (Low_Bound + High_Bound) / 2
    rhos = 1 / v1_pT(p, Ts)
    If rhos < rho Then
      High_Bound = Ts
    Else
      Low_Bound = Ts
    End If
    Loop
    T1_prho = Ts
End Function
'***********************************************************************************************************
'*2.2 Functions for region 2

Function v2_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'6 Equations for Region 2, Section. 6.1 Basic Equation
'Table 11 and 12, Page 14 and 15
  Dim i As Integer
  Dim tau, g0_pi, gr_pi As Double
  Dim Ir, Jr, nr, J0, n0 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  J0 = Array(0, 1, -5, -4, -3, -2, -1, 2, 3)
  n0 = Array(-9.6927686500217, 10.086655968018, -0.005608791128302, 0.071452738081455, -0.40710498223928, 1.4240819171444, -4.383951131945, -0.28408632460772, 0.021268463753307)
  Ir = Array(1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 10, 16, 16, 18, 20, 20, 20, 21, 22, 23, 24, 24, 24)
  Jr = Array(0, 1, 2, 3, 6, 1, 2, 4, 7, 36, 0, 1, 3, 6, 35, 1, 2, 3, 7, 3, 16, 35, 0, 11, 25, 8, 36, 13, 4, 10, 14, 29, 50, 57, 20, 35, 48, 21, 53, 39, 26, 40, 58)
  nr = Array(-1.7731742473213E-03, -0.017834862292358, -0.045996013696365, -0.057581259083432, -0.05032527872793, -3.3032641670203E-05, -1.8948987516315E-04, -3.9392777243355E-03, -0.043797295650573, -2.6674547914087E-05, 2.0481737692309E-08, 4.3870667284435E-07, -3.227767723857E-05, -1.5033924542148E-03, -0.040668253562649, -7.8847309559367E-10, 1.2790717852285E-08, 4.8225372718507E-07, 2.2922076337661E-06, -1.6714766451061E-11, -2.1171472321355E-03, -23.895741934104, -5.905956432427E-18, -1.2621808899101E-06, -0.038946842435739, 1.1256211360459E-11, -8.2311340897998, 1.9809712802088E-08, 1.0406965210174E-19, -1.0234747095929E-13, -1.0018179379511E-09, -8.0882908646985E-11, 0.10693031879409, -0.33662250574171, 8.9185845355421E-25, 3.0629316876232E-13, -4.2002467698208E-06, -5.9056029685639E-26, 3.7826947613457E-06, -1.2768608934681E-15, 7.3087610595061E-29, 5.5414715350778E-17, -9.436970724121E-07)
  tau = 540 / t
  g0_pi = 1 / p
  gr_pi = 0#
  For i = 0 To 42
   gr_pi = gr_pi + nr(i) * Ir(i) * p ^ (Ir(i) - 1) * (tau - 0.5) ^ Jr(i)
  Next i
  v2_pT = R * t / p * p * (g0_pi + gr_pi) / 1000
End Function
Function h2_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'6 Equations for Region 2, Section. 6.1 Basic Equation
'Table 11 and 12, Page 14 and 15
  Dim i As Integer
  Dim tau, g0_tau, gr_tau As Double
  Dim Ir, Jr, nr, J0, n0 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  J0 = Array(0, 1, -5, -4, -3, -2, -1, 2, 3)
  n0 = Array(-9.6927686500217, 10.086655968018, -0.005608791128302, 0.071452738081455, -0.40710498223928, 1.4240819171444, -4.383951131945, -0.28408632460772, 0.021268463753307)
  Ir = Array(1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 10, 16, 16, 18, 20, 20, 20, 21, 22, 23, 24, 24, 24)
  Jr = Array(0, 1, 2, 3, 6, 1, 2, 4, 7, 36, 0, 1, 3, 6, 35, 1, 2, 3, 7, 3, 16, 35, 0, 11, 25, 8, 36, 13, 4, 10, 14, 29, 50, 57, 20, 35, 48, 21, 53, 39, 26, 40, 58)
  nr = Array(-1.7731742473213E-03, -0.017834862292358, -0.045996013696365, -0.057581259083432, -0.05032527872793, -3.3032641670203E-05, -1.8948987516315E-04, -3.9392777243355E-03, -0.043797295650573, -2.6674547914087E-05, 2.0481737692309E-08, 4.3870667284435E-07, -3.227767723857E-05, -1.5033924542148E-03, -0.040668253562649, -7.8847309559367E-10, 1.2790717852285E-08, 4.8225372718507E-07, 2.2922076337661E-06, -1.6714766451061E-11, -2.1171472321355E-03, -23.895741934104, -5.905956432427E-18, -1.2621808899101E-06, -0.038946842435739, 1.1256211360459E-11, -8.2311340897998, 1.9809712802088E-08, 1.0406965210174E-19, -1.0234747095929E-13, -1.0018179379511E-09, -8.0882908646985E-11, 0.10693031879409, -0.33662250574171, 8.9185845355421E-25, 3.0629316876232E-13, -4.2002467698208E-06, -5.9056029685639E-26, 3.7826947613457E-06, -1.2768608934681E-15, 7.3087610595061E-29, 5.5414715350778E-17, -9.436970724121E-07)
  tau = 540 / t
  g0_tau = 0#
  For i = 0 To 8
    g0_tau = g0_tau + n0(i) * J0(i) * tau ^ (J0(i) - 1)
  Next i
  gr_tau = 0#
  For i = 0 To 42
   gr_tau = gr_tau + nr(i) * p ^ Ir(i) * Jr(i) * (tau - 0.5) ^ (Jr(i) - 1)
  Next i
  h2_pT = R * t * tau * (g0_tau + gr_tau)
End Function
Function u2_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'6 Equations for Region 2, Section. 6.1 Basic Equation
'Table 11 and 12, Page 14 and 15
  Dim i As Integer
  Dim tau, g0_tau, g0_pi, gr_pi, gr_tau As Double
  Dim Ir, Jr, nr, J0, n0 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  J0 = Array(0, 1, -5, -4, -3, -2, -1, 2, 3)
  n0 = Array(-9.6927686500217, 10.086655968018, -0.005608791128302, 0.071452738081455, -0.40710498223928, 1.4240819171444, -4.383951131945, -0.28408632460772, 0.021268463753307)
  Ir = Array(1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 10, 16, 16, 18, 20, 20, 20, 21, 22, 23, 24, 24, 24)
  Jr = Array(0, 1, 2, 3, 6, 1, 2, 4, 7, 36, 0, 1, 3, 6, 35, 1, 2, 3, 7, 3, 16, 35, 0, 11, 25, 8, 36, 13, 4, 10, 14, 29, 50, 57, 20, 35, 48, 21, 53, 39, 26, 40, 58)
  nr = Array(-1.7731742473213E-03, -0.017834862292358, -0.045996013696365, -0.057581259083432, -0.05032527872793, -3.3032641670203E-05, -1.8948987516315E-04, -3.9392777243355E-03, -0.043797295650573, -2.6674547914087E-05, 2.0481737692309E-08, 4.3870667284435E-07, -3.227767723857E-05, -1.5033924542148E-03, -0.040668253562649, -7.8847309559367E-10, 1.2790717852285E-08, 4.8225372718507E-07, 2.2922076337661E-06, -1.6714766451061E-11, -2.1171472321355E-03, -23.895741934104, -5.905956432427E-18, -1.2621808899101E-06, -0.038946842435739, 1.1256211360459E-11, -8.2311340897998, 1.9809712802088E-08, 1.0406965210174E-19, -1.0234747095929E-13, -1.0018179379511E-09, -8.0882908646985E-11, 0.10693031879409, -0.33662250574171, 8.9185845355421E-25, 3.0629316876232E-13, -4.2002467698208E-06, -5.9056029685639E-26, 3.7826947613457E-06, -1.2768608934681E-15, 7.3087610595061E-29, 5.5414715350778E-17, -9.436970724121E-07)
  tau = 540 / t
  g0_pi = 1 / p
  g0_tau = 0#
  For i = 0 To 8
    g0_tau = g0_tau + n0(i) * J0(i) * tau ^ (J0(i) - 1)
  Next i
  gr_pi = 0#
  gr_tau = 0#
  For i = 0 To 42
   gr_pi = gr_pi + nr(i) * Ir(i) * p ^ (Ir(i) - 1) * (tau - 0.5) ^ Jr(i)
   gr_tau = gr_tau + nr(i) * p ^ Ir(i) * Jr(i) * (tau - 0.5) ^ (Jr(i) - 1)
  Next i
  u2_pT = R * t * (tau * (g0_tau + gr_tau) - p * (g0_pi + gr_pi))
End Function

Function s2_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'6 Equations for Region 2, Section. 6.1 Basic Equation
'Table 11 and 12, Page 14 and 15
  Dim i As Integer
  Dim tau, g0, g0_tau, gr, gr_tau As Double
  Dim Ir, Jr, nr, J0, n0 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  J0 = Array(0, 1, -5, -4, -3, -2, -1, 2, 3)
  n0 = Array(-9.6927686500217, 10.086655968018, -0.005608791128302, 0.071452738081455, -0.40710498223928, 1.4240819171444, -4.383951131945, -0.28408632460772, 0.021268463753307)
  Ir = Array(1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 10, 16, 16, 18, 20, 20, 20, 21, 22, 23, 24, 24, 24)
  Jr = Array(0, 1, 2, 3, 6, 1, 2, 4, 7, 36, 0, 1, 3, 6, 35, 1, 2, 3, 7, 3, 16, 35, 0, 11, 25, 8, 36, 13, 4, 10, 14, 29, 50, 57, 20, 35, 48, 21, 53, 39, 26, 40, 58)
  nr = Array(-1.7731742473213E-03, -0.017834862292358, -0.045996013696365, -0.057581259083432, -0.05032527872793, -3.3032641670203E-05, -1.8948987516315E-04, -3.9392777243355E-03, -0.043797295650573, -2.6674547914087E-05, 2.0481737692309E-08, 4.3870667284435E-07, -3.227767723857E-05, -1.5033924542148E-03, -0.040668253562649, -7.8847309559367E-10, 1.2790717852285E-08, 4.8225372718507E-07, 2.2922076337661E-06, -1.6714766451061E-11, -2.1171472321355E-03, -23.895741934104, -5.905956432427E-18, -1.2621808899101E-06, -0.038946842435739, 1.1256211360459E-11, -8.2311340897998, 1.9809712802088E-08, 1.0406965210174E-19, -1.0234747095929E-13, -1.0018179379511E-09, -8.0882908646985E-11, 0.10693031879409, -0.33662250574171, 8.9185845355421E-25, 3.0629316876232E-13, -4.2002467698208E-06, -5.9056029685639E-26, 3.7826947613457E-06, -1.2768608934681E-15, 7.3087610595061E-29, 5.5414715350778E-17, -9.436970724121E-07)
  tau = 540 / t
  g0 = Log(p)
  g0_tau = 0#
  For i = 0 To 8
    g0 = g0 + n0(i) * tau ^ J0(i)
    g0_tau = g0_tau + n0(i) * J0(i) * tau ^ (J0(i) - 1)
  Next i
  gr = 0#
  gr_tau = 0#
  For i = 0 To 42
   gr = gr + nr(i) * p ^ Ir(i) * (tau - 0.5) ^ Jr(i)
   gr_tau = gr_tau + nr(i) * p ^ Ir(i) * Jr(i) * (tau - 0.5) ^ (Jr(i) - 1)
  Next i
  s2_pT = R * (tau * (g0_tau + gr_tau) - (g0 + gr))
End Function
Function Cp2_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'6 Equations for Region 2, Section. 6.1 Basic Equation
'Table 11 and 12, Page 14 and 15
  Dim i As Integer
  Dim tau, g0_tautau, gr_tautau As Double
  Dim Ir, Jr, nr, J0, n0 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  J0 = Array(0, 1, -5, -4, -3, -2, -1, 2, 3)
  n0 = Array(-9.6927686500217, 10.086655968018, -0.005608791128302, 0.071452738081455, -0.40710498223928, 1.4240819171444, -4.383951131945, -0.28408632460772, 0.021268463753307)
  Ir = Array(1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 10, 16, 16, 18, 20, 20, 20, 21, 22, 23, 24, 24, 24)
  Jr = Array(0, 1, 2, 3, 6, 1, 2, 4, 7, 36, 0, 1, 3, 6, 35, 1, 2, 3, 7, 3, 16, 35, 0, 11, 25, 8, 36, 13, 4, 10, 14, 29, 50, 57, 20, 35, 48, 21, 53, 39, 26, 40, 58)
  nr = Array(-1.7731742473213E-03, -0.017834862292358, -0.045996013696365, -0.057581259083432, -0.05032527872793, -3.3032641670203E-05, -1.8948987516315E-04, -3.9392777243355E-03, -0.043797295650573, -2.6674547914087E-05, 2.0481737692309E-08, 4.3870667284435E-07, -3.227767723857E-05, -1.5033924542148E-03, -0.040668253562649, -7.8847309559367E-10, 1.2790717852285E-08, 4.8225372718507E-07, 2.2922076337661E-06, -1.6714766451061E-11, -2.1171472321355E-03, -23.895741934104, -5.905956432427E-18, -1.2621808899101E-06, -0.038946842435739, 1.1256211360459E-11, -8.2311340897998, 1.9809712802088E-08, 1.0406965210174E-19, -1.0234747095929E-13, -1.0018179379511E-09, -8.0882908646985E-11, 0.10693031879409, -0.33662250574171, 8.9185845355421E-25, 3.0629316876232E-13, -4.2002467698208E-06, -5.9056029685639E-26, 3.7826947613457E-06, -1.2768608934681E-15, 7.3087610595061E-29, 5.5414715350778E-17, -9.436970724121E-07)
  tau = 540 / t
  g0_tautau = 0#
  For i = 0 To 8
    g0_tautau = g0_tautau + n0(i) * J0(i) * (J0(i) - 1) * tau ^ (J0(i) - 2)
  Next i
  gr_tautau = 0#
  For i = 0 To 42
   gr_tautau = gr_tautau + nr(i) * p ^ Ir(i) * Jr(i) * (Jr(i) - 1) * (tau - 0.5) ^ (Jr(i) - 2)
  Next i
  Cp2_pT = -R * tau ^ 2 * (g0_tautau + gr_tautau)
End Function
Function Cv2_pT(ByVal p As Double, ByVal t As Double) As Double
  Dim i As Integer
  Dim tau, g0_tautau, gr_pi, gr_pitau, gr_pipi, gr_tautau As Double
  Dim Ir, Jr, nr, J0, n0 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  J0 = Array(0, 1, -5, -4, -3, -2, -1, 2, 3)
  n0 = Array(-9.6927686500217, 10.086655968018, -0.005608791128302, 0.071452738081455, -0.40710498223928, 1.4240819171444, -4.383951131945, -0.28408632460772, 0.021268463753307)
  Ir = Array(1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 10, 16, 16, 18, 20, 20, 20, 21, 22, 23, 24, 24, 24)
  Jr = Array(0, 1, 2, 3, 6, 1, 2, 4, 7, 36, 0, 1, 3, 6, 35, 1, 2, 3, 7, 3, 16, 35, 0, 11, 25, 8, 36, 13, 4, 10, 14, 29, 50, 57, 20, 35, 48, 21, 53, 39, 26, 40, 58)
  nr = Array(-1.7731742473213E-03, -0.017834862292358, -0.045996013696365, -0.057581259083432, -0.05032527872793, -3.3032641670203E-05, -1.8948987516315E-04, -3.9392777243355E-03, -0.043797295650573, -2.6674547914087E-05, 2.0481737692309E-08, 4.3870667284435E-07, -3.227767723857E-05, -1.5033924542148E-03, -0.040668253562649, -7.8847309559367E-10, 1.2790717852285E-08, 4.8225372718507E-07, 2.2922076337661E-06, -1.6714766451061E-11, -2.1171472321355E-03, -23.895741934104, -5.905956432427E-18, -1.2621808899101E-06, -0.038946842435739, 1.1256211360459E-11, -8.2311340897998, 1.9809712802088E-08, 1.0406965210174E-19, -1.0234747095929E-13, -1.0018179379511E-09, -8.0882908646985E-11, 0.10693031879409, -0.33662250574171, 8.9185845355421E-25, 3.0629316876232E-13, -4.2002467698208E-06, -5.9056029685639E-26, 3.7826947613457E-06, -1.2768608934681E-15, 7.3087610595061E-29, 5.5414715350778E-17, -9.436970724121E-07)
  tau = 540 / t
  g0_tautau = 0#
  For i = 0 To 8
    g0_tautau = g0_tautau + n0(i) * J0(i) * (J0(i) - 1) * tau ^ (J0(i) - 2)
  Next i
  gr_pi = 0#
  gr_pitau = 0#
  gr_pipi = 0#
  gr_tautau = 0#
  For i = 0 To 42
   gr_pi = gr_pi + nr(i) * Ir(i) * p ^ (Ir(i) - 1) * (tau - 0.5) ^ Jr(i)
   gr_pipi = gr_pipi + nr(i) * Ir(i) * (Ir(i) - 1) * p ^ (Ir(i) - 2) * (tau - 0.5) ^ Jr(i)
   gr_pitau = gr_pitau + nr(i) * Ir(i) * p ^ (Ir(i) - 1) * Jr(i) * (tau - 0.5) ^ (Jr(i) - 1)
   gr_tautau = gr_tautau + nr(i) * p ^ Ir(i) * Jr(i) * (Jr(i) - 1) * (tau - 0.5) ^ (Jr(i) - 2)
  Next i
  Cv2_pT = R * (-(tau ^ 2 * (g0_tautau + gr_tautau)) - ((1 + p * gr_pi - tau * p * gr_pitau) ^ 2) / (1 - p ^ 2 * gr_pipi))
End Function
Function w2_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'6 Equations for Region 2, Section. 6.1 Basic Equation
'Table 11 and 12, Page 14 and 15
  Dim i As Integer
  Dim tau, g0_tautau, gr_pi, gr_pitau, gr_pipi, gr_tautau As Double
  Dim Ir, Jr, nr, J0, n0 As Variant
  Const R As Double = 0.461526 'kJ/(kg K)
  J0 = Array(0, 1, -5, -4, -3, -2, -1, 2, 3)
  n0 = Array(-9.6927686500217, 10.086655968018, -0.005608791128302, 0.071452738081455, -0.40710498223928, 1.4240819171444, -4.383951131945, -0.28408632460772, 0.021268463753307)
  Ir = Array(1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 5, 6, 6, 6, 7, 7, 7, 8, 8, 9, 10, 10, 10, 16, 16, 18, 20, 20, 20, 21, 22, 23, 24, 24, 24)
  Jr = Array(0, 1, 2, 3, 6, 1, 2, 4, 7, 36, 0, 1, 3, 6, 35, 1, 2, 3, 7, 3, 16, 35, 0, 11, 25, 8, 36, 13, 4, 10, 14, 29, 50, 57, 20, 35, 48, 21, 53, 39, 26, 40, 58)
  nr = Array(-1.7731742473213E-03, -0.017834862292358, -0.045996013696365, -0.057581259083432, -0.05032527872793, -3.3032641670203E-05, -1.8948987516315E-04, -3.9392777243355E-03, -0.043797295650573, -2.6674547914087E-05, 2.0481737692309E-08, 4.3870667284435E-07, -3.227767723857E-05, -1.5033924542148E-03, -0.040668253562649, -7.8847309559367E-10, 1.2790717852285E-08, 4.8225372718507E-07, 2.2922076337661E-06, -1.6714766451061E-11, -2.1171472321355E-03, -23.895741934104, -5.905956432427E-18, -1.2621808899101E-06, -0.038946842435739, 1.1256211360459E-11, -8.2311340897998, 1.9809712802088E-08, 1.0406965210174E-19, -1.0234747095929E-13, -1.0018179379511E-09, -8.0882908646985E-11, 0.10693031879409, -0.33662250574171, 8.9185845355421E-25, 3.0629316876232E-13, -4.2002467698208E-06, -5.9056029685639E-26, 3.7826947613457E-06, -1.2768608934681E-15, 7.3087610595061E-29, 5.5414715350778E-17, -9.436970724121E-07)
  tau = 540 / t
  g0_tautau = 0#
  For i = 0 To 8
    g0_tautau = g0_tautau + n0(i) * J0(i) * (J0(i) - 1) * tau ^ (J0(i) - 2)
  Next i
  gr_pi = 0#
  gr_pitau = 0#
  gr_pipi = 0#
  gr_tautau = 0#
  For i = 0 To 42
   gr_pi = gr_pi + nr(i) * Ir(i) * p ^ (Ir(i) - 1) * (tau - 0.5) ^ Jr(i)
   gr_pipi = gr_pipi + nr(i) * Ir(i) * (Ir(i) - 1) * p ^ (Ir(i) - 2) * (tau - 0.5) ^ Jr(i)
   gr_pitau = gr_pitau + nr(i) * Ir(i) * p ^ (Ir(i) - 1) * Jr(i) * (tau - 0.5) ^ (Jr(i) - 1)
   gr_tautau = gr_tautau + nr(i) * p ^ Ir(i) * Jr(i) * (Jr(i) - 1) * (tau - 0.5) ^ (Jr(i) - 2)
  Next i
  w2_pT = (1000 * R * t * (1 + 2 * p * gr_pi + p ^ 2 * gr_pi ^ 2) / ((1 - p ^ 2 * gr_pipi) + (1 + p * gr_pi - tau * p * gr_pitau) ^ 2 / (tau ^ 2 * (g0_tautau + gr_tautau)))) ^ 0.5
End Function
Function T2_ph(ByVal p As Double, ByVal h As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  '6 Equations for Region 2,6.3.1 The Backward Equations T( p, h ) for Subregions 2a, 2b, and 2c
  Dim sub_reg As Integer
  Dim i As Integer
  Dim Ts, hs As Double
  Dim Ji, Ii, ni As Variant

  If p < 4 Then
   sub_reg = 1
  Else
   If p < (905.84278514723 - 0.67955786399241 * h + 1.2809002730136E-04 * h ^ 2) Then
     sub_reg = 2
   Else
     sub_reg = 3
   End If
  End If

  Select Case sub_reg
  Case 1
    'Subregion A
    'Table 20, Eq 22, page 22
    Ji = Array(0, 1, 2, 3, 7, 20, 0, 1, 2, 3, 7, 9, 11, 18, 44, 0, 2, 7, 36, 38, 40, 42, 44, 24, 44, 12, 32, 44, 32, 36, 42, 34, 44, 28)
    Ii = Array(0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 7)
    ni = Array(1089.8952318288, 849.51654495535, -107.81748091826, 33.153654801263, -7.4232016790248, 11.765048724356, 1.844574935579, -4.1792700549624, 6.2478196935812, -17.344563108114, -200.58176862096, 271.96065473796, -455.11318285818, 3091.9688604755, 252266.40357872, -6.1707422868339E-03, -0.31078046629583, 11.670873077107, 128127984.04046, -985549096.23276, 2822454697.3002, -3594897141.0703, 1722734991.3197, -13551.334240775, 12848734.66465, 1.3865724283226, 235988.32556514, -13105236.545054, 7399.9835474766, -551966.9703006, 3715408.5996233, 19127.72923966, -415351.64835634, -62.459855192507)
    Ts = 0
    hs = h / 2000
    For i = 0 To 33
      Ts = Ts + ni(i) * p ^ (Ii(i)) * (hs - 2.1) ^ Ji(i)
    Next i
    T2_ph = Ts
  Case 2
    'Subregion B
    'Table 21, Eq 23, page 23
    Ji = Array(0, 1, 2, 12, 18, 24, 28, 40, 0, 2, 6, 12, 18, 24, 28, 40, 2, 8, 18, 40, 1, 2, 12, 24, 2, 12, 18, 24, 28, 40, 18, 24, 40, 28, 2, 28, 1, 40)
    Ii = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 5, 5, 5, 6, 7, 7, 9, 9)
    ni = Array(1489.5041079516, 743.07798314034, -97.708318797837, 2.4742464705674, -0.63281320016026, 1.1385952129658, -0.47811863648625, 8.5208123431544E-03, 0.93747147377932, 3.3593118604916, 3.3809355601454, 0.16844539671904, 0.73875745236695, -0.47128737436186, 0.15020273139707, -0.002176411421975, -0.021810755324761, -0.10829784403677, -0.046333324635812, 7.1280351959551E-05, 1.1032831789999E-04, 1.8955248387902E-04, 3.0891541160537E-03, 1.3555504554949E-03, 2.8640237477456E-07, -1.0779857357512E-05, -7.6462712454814E-05, 1.4052392818316E-05, -3.1083814331434E-05, -1.0302738212103E-06, 2.821728163504E-07, 1.2704902271945E-06, 7.3803353468292E-08, -1.1030139238909E-08, -8.1456365207833E-14, -2.5180545682962E-11, -1.7565233969407E-18, 8.6934156344163E-15)
    Ts = 0
    hs = h / 2000
    For i = 0 To 37
      Ts = Ts + ni(i) * (p - 2) ^ (Ii(i)) * (hs - 2.6) ^ Ji(i)
    Next i
    T2_ph = Ts
  Case Else
    'Subregion C
    'Table 22, Eq 24, page 24
    Ji = Array(0, 4, 0, 2, 0, 2, 0, 1, 0, 2, 0, 1, 4, 8, 4, 0, 1, 4, 10, 12, 16, 20, 22)
    Ii = Array(-7, -7, -6, -6, -5, -5, -2, -2, -1, -1, 0, 0, 1, 1, 2, 6, 6, 6, 6, 6, 6, 6, 6)
    ni = Array(-3236839855524.2, 7326335090218.1, 358250899454.47, -583401318515.9, -10783068217.47, 20825544563.171, 610747.83564516, 859777.2253558, -25745.72360417, 31081.088422714, 1208.2315865936, 482.19755109255, 3.7966001272486, -10.842984880077, -0.04536417267666, 1.4559115658698E-13, 1.126159740723E-12, -1.7804982240686E-11, 1.2324579690832E-07, -1.1606921130984E-06, 2.7846367088554E-05, -5.9270038474176E-04, 1.2918582991878E-03)
    Ts = 0
    hs = h / 2000
    For i = 0 To 22
      Ts = Ts + ni(i) * (p + 25) ^ (Ii(i)) * (hs - 1.8) ^ Ji(i)
    Next i
    T2_ph = Ts
  End Select
End Function
Function T2_ps(ByVal p As Double, ByVal s As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  '6 Equations for Region 2,6.3.2 The Backward Equations T( p, s ) for Subregions 2a, 2b, and 2c
  'Page 26
  Dim sub_reg As Integer
  Dim i As Integer
  Dim teta, sigma As Double
  Dim Ji, Ii, ni As Variant

  If p < 4 Then
     sub_reg = 1
  Else
     If s < 5.85 Then
       sub_reg = 3
     Else
       sub_reg = 2
     End If
  End If
  Select Case sub_reg
  Case 1
   'Subregion A
   'Table 25, Eq 25, page 26
   Ii = Array(-1.5, -1.5, -1.5, -1.5, -1.5, -1.5, -1.25, -1.25, -1.25, -1, -1, -1, -1, -1, -1, -0.75, -0.75, -0.5, -0.5, -0.5, -0.5, -0.25, -0.25, -0.25, -0.25, 0.25, 0.25, 0.25, 0.25, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.5, 0.75, 0.75, 0.75, 0.75, 1, 1, 1.25, 1.25, 1.5, 1.5)
   Ji = Array(-24, -23, -19, -13, -11, -10, -19, -15, -6, -26, -21, -17, -16, -9, -8, -15, -14, -26, -13, -9, -7, -27, -25, -11, -6, 1, 4, 8, 11, 0, 1, 5, 6, 10, 14, 16, 0, 4, 9, 17, 7, 18, 3, 15, 5, 18)
   ni = Array(-392359.83861984, 515265.7382727, 40482.443161048, -321.93790923902, 96.961424218694, -22.867846371773, -449429.14124357, -5011.8336020166, 0.35684463560015, 44235.33584819, -13673.388811708, 421632.60207864, 22516.925837475, 474.42144865646, -149.31130797647, -197811.26320452, -23554.39947076, -19070.616302076, 55375.669883164, 3829.3691437363, -603.91860580567, 1936.3102620331, 4266.064369861, -5978.0638872718, -704.01463926862, 338.36784107553, 20.862786635187, 0.033834172656196, -4.3124428414893E-05, 166.53791356412, -139.86292055898, -0.78849547999872, 0.072132411753872, -5.9754839398283E-03, -1.2141358953904E-05, 2.3227096733871E-07, -10.538463566194, 2.0718925496502, -0.072193155260427, 2.074988708112E-07, -0.018340657911379, 2.9036272348696E-07, 0.21037527893619, 2.5681239729999E-04, -0.012799002933781, -8.2198102652018E-06)
   sigma = s / 2
   teta = 0
   For i = 0 To 45
     teta = teta + ni(i) * p ^ Ii(i) * (sigma - 2) ^ Ji(i)
   Next i
   T2_ps = teta
  Case 2
    'Subregion B
    'Table 26, Eq 26, page 27
    Ii = Array(-6, -6, -5, -5, -4, -4, -4, -3, -3, -3, -3, -2, -2, -2, -2, -1, -1, -1, -1, -1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 5, 5, 5)
    Ji = Array(0, 11, 0, 11, 0, 1, 11, 0, 1, 11, 12, 0, 1, 6, 10, 0, 1, 5, 8, 9, 0, 1, 2, 4, 5, 6, 9, 0, 1, 2, 3, 7, 8, 0, 1, 5, 0, 1, 3, 0, 1, 0, 1, 2)
    ni = Array(316876.65083497, 20.864175881858, -398593.99803599, -21.816058518877, 223697.85194242, -2784.1703445817, 9.920743607148, -75197.512299157, 2970.8605951158, -3.4406878548526, 0.38815564249115, 17511.29508575, -1423.7112854449, 1.0943803364167, 0.89971619308495, -3375.9740098958, 471.62885818355, -1.9188241993679, 0.41078580492196, -0.33465378172097, 1387.0034777505, -406.63326195838, 41.72734715961, 2.1932549434532, -1.0320050009077, 0.35882943516703, 5.2511453726066E-03, 12.838916450705, -2.8642437219381, 0.56912683664855, -0.099962954584931, -3.2632037778459E-03, 2.3320922576723E-04, -0.1533480985745, 0.029072288239902, 3.7534702741167E-04, 1.7296691702411E-03, -3.8556050844504E-04, -3.5017712292608E-05, -1.4566393631492E-05, 5.6420857267269E-06, 4.1286150074605E-08, -2.0684671118824E-08, 1.6409393674725E-09)
    sigma = s / 0.7853
    teta = 0
    For i = 0 To 43
      teta = teta + ni(i) * p ^ Ii(i) * (10 - sigma) ^ Ji(i)
    Next i
    T2_ps = teta
  Case Else
    'Subregion C
    'Table 27, Eq 27, page 28
    Ii = Array(-2, -2, -1, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4, 5, 5, 5, 6, 6, 7, 7, 7, 7, 7)
    Ji = Array(0, 1, 0, 0, 1, 2, 3, 0, 1, 3, 4, 0, 1, 2, 0, 1, 5, 0, 1, 4, 0, 1, 2, 0, 1, 0, 1, 3, 4, 5)
    ni = Array(909.68501005365, 2404.566708842, -591.6232638713, 541.45404128074, -270.98308411192, 979.76525097926, -469.66772959435, 14.399274604723, -19.104204230429, 5.3299167111971, -21.252975375934, -0.3114733441376, 0.60334840894623, -0.042764839702509, 5.8185597255259E-03, -0.014597008284753, 5.6631175631027E-03, -7.6155864584577E-05, 2.2440342919332E-04, -1.2561095013413E-05, 6.3323132660934E-07, -2.0541989675375E-06, 3.6405370390082E-08, -2.9759897789215E-09, 1.0136618529763E-08, 5.9925719692351E-12, -2.0677870105164E-11, -2.0874278181886E-11, 1.0162166825089E-10, -1.6429828281347E-10)
    sigma = s / 2.9251
    teta = 0
    For i = 0 To 29
      teta = teta + ni(i) * p ^ Ii(i) * (2 - sigma) ^ Ji(i)
    Next i
    T2_ps = teta
    End Select
End Function
Function p2_hs(ByVal h As Double, ByVal s As Double) As Double
'Supplementary Release on Backward Equations for Pressure as a Function of Enthalpy and Entropy p(h,s) to the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
'Chapter 6:Backward Equations p(h,s) for Region 2
  Dim sub_reg As Integer
  Dim i As Integer
  Dim eta, teta, sigma, p As Double
  Dim Ji, Ii, ni As Variant

  If h < (-3498.98083432139 + 2575.60716905876 * s - 421.073558227969 * s ^ 2 + 27.6349063799944 * s ^ 3) Then
    sub_reg = 1
  Else
   If s < 5.85 Then
     sub_reg = 3
   Else
     sub_reg = 2
   End If
  End If
  Select Case sub_reg
  Case 1
    'Subregion A
    'Table 6, Eq 3, page 8
    Ii = Array(0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 3, 3, 4, 5, 5, 6, 7)
    Ji = Array(1, 3, 6, 16, 20, 22, 0, 1, 2, 3, 5, 6, 10, 16, 20, 22, 3, 16, 20, 0, 2, 3, 6, 16, 16, 3, 16, 3, 1)
    ni = Array(-1.82575361923032E-02, -0.125229548799536, 0.592290437320145, 6.04769706185122, 238.624965444474, -298.639090222922, 0.051225081304075, -0.437266515606486, 0.413336902999504, -5.16468254574773, -5.57014838445711, 12.8555037824478, 11.414410895329, -119.504225652714, -2847.7798596156, 4317.57846408006, 1.1289404080265, 1974.09186206319, 1516.12444706087, 1.41324451421235E-02, 0.585501282219601, -2.97258075863012, 5.94567314847319, -6236.56565798905, 9659.86235133332, 6.81500934948134, -6332.07286824489, -5.5891922446576, 4.00645798472063E-02)
    eta = h / 4200
    sigma = s / 12
    p = 0
    For i = 0 To 28
      p = p + ni(i) * (eta - 0.5) ^ Ii(i) * (sigma - 1.2) ^ Ji(i)
    Next i
    p2_hs = p ^ 4 * 4
  Case 2
    'Subregion B
    'Table 7, Eq 4, page 9
    Ii = Array(0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 3, 4, 4, 5, 5, 6, 6, 6, 7, 7, 8, 8, 8, 8, 12, 14)
    Ji = Array(0, 1, 2, 4, 8, 0, 1, 2, 3, 5, 12, 1, 6, 18, 0, 1, 7, 12, 1, 16, 1, 12, 1, 8, 18, 1, 16, 1, 3, 14, 18, 10, 16)
    ni = Array(8.01496989929495E-02, -0.543862807146111, 0.337455597421283, 8.9055545115745, 313.840736431485, 0.797367065977789, -1.2161697355624, 8.72803386937477, -16.9769781757602, -186.552827328416, 95115.9274344237, -18.9168510120494, -4334.0703719484, 543212633.012715, 0.144793408386013, 128.024559637516, -67230.9534071268, 33697238.0095287, -586.63419676272, -22140322476.9889, 1716.06668708389, -570817595.806302, -3121.09693178482, -2078413.8463301, 3056059461577.86, 3221.57004314333, 326810259797.295, -1441.04158934487, 410.694867802691, 109077066873.024, -24796465425889.3, 1888019068.65134, -123651009018773#)
    eta = h / 4100
    sigma = s / 7.9
    For i = 0 To 32
      p = p + ni(i) * (eta - 0.6) ^ Ii(i) * (sigma - 1.01) ^ Ji(i)
    Next i
    p2_hs = p ^ 4 * 100
  Case Else
    'Subregion C
    'Table 8, Eq 5, page 10
    Ii = Array(0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 5, 5, 5, 5, 6, 6, 10, 12, 16)
    Ji = Array(0, 1, 2, 3, 4, 8, 0, 2, 5, 8, 14, 2, 3, 7, 10, 18, 0, 5, 8, 16, 18, 18, 1, 4, 6, 14, 8, 18, 7, 7, 10)
    ni = Array(0.112225607199012, -3.39005953606712, -32.0503911730094, -197.5973051049, -407.693861553446, 13294.3775222331, 1.70846839774007, 37.3694198142245, 3581.44365815434, 423014.446424664, -751071025.760063, 52.3446127607898, -228.351290812417, -960652.417056937, -80705929.2526074, 1626980172256.69, 0.772465073604171, 46392.9973837746, -13731788.5134128, 1704703926305.12, -25110462818730.8, 31774883083552#, 53.8685623675312, -55308.9094625169, -1028615.22421405, 2042494187562.34, 273918446.626977, -2.63963146312685E+15, -1078908541.08088, -29649262098.0124, -1.11754907323424E+15)
    eta = h / 3500
    sigma = s / 5.9
    For i = 0 To 30
      p = p + ni(i) * (eta - 0.7) ^ Ii(i) * (sigma - 1.1) ^ Ji(i)
    Next i
    p2_hs = p ^ 4 * 100
  End Select
End Function
Function T2_prho(ByVal p As Double, ByVal rho As Double) As Double
  'Solve by iteration. Observe that fo low temperatures this equation has 2 solutions.
  'Solve with half interval method
  Dim Low_Bound, High_Bound, rhos, Ts As Double

  If p < 16.5292 Then
    Low_Bound = T4_p(p)
  Else
    Low_Bound = B23T_p(p)
  End If
  High_Bound = 1073.15
  Do While Abs(rho - rhos) > 0.000001
    Ts = (Low_Bound + High_Bound) / 2
    rhos = 1 / v2_pT(p, Ts)
    If rhos < rho Then
      High_Bound = Ts
    Else
      Low_Bound = Ts
    End If
    Loop
    T2_prho = Ts
End Function
'***********************************************************************************************************
'*2.3 Functions for region 3

Function p3_rhoT(ByVal rho As Double, ByVal t As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  '7 Basic Equation for Region 3, Section. 6.1 Basic Equation
  'Table 30 and 31, Page 30 and 31
  Dim i As Integer, Ji, Ii, ni As Variant, delta, tau, fidelta As Double
  Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
  Ii = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 8, 9, 9, 10, 10, 11)
  Ji = Array(0, 0, 1, 2, 7, 10, 12, 23, 2, 6, 15, 17, 0, 2, 6, 7, 22, 26, 0, 2, 4, 16, 26, 0, 2, 4, 26, 1, 3, 26, 0, 2, 26, 2, 26, 2, 26, 0, 1, 26)
  ni = Array(1.0658070028513, -15.732845290239, 20.944396974307, -7.6867707878716, 2.6185947787954, -2.808078114862, 1.2053369696517, -8.4566812812502E-03, -1.2654315477714, -1.1524407806681, 0.88521043984318, -0.64207765181607, 0.38493460186671, -0.85214708824206, 4.8972281541877, -3.0502617256965, 0.039420536879154, 0.12558408424308, -0.2799932969871, 1.389979956946, -2.018991502357, -8.2147637173963E-03, -0.47596035734923, 0.0439840744735, -0.44476435428739, 0.90572070719733, 0.70522450087967, 0.10770512626332, -0.32913623258954, -0.50871062041158, -0.022175400873096, 0.094260751665092, 0.16436278447961, -0.013503372241348, -0.014834345352472, 5.7922953628084E-04, 3.2308904703711E-03, 8.0964802996215E-05, -1.6557679795037E-04, -4.4923899061815E-05)
  delta = rho / rhoc
  tau = tc / t
  fidelta = 0
  For i = 1 To 39
    fidelta = fidelta + ni(i) * Ii(i) * delta ^ (Ii(i) - 1) * tau ^ Ji(i)
  Next i
  fidelta = fidelta + ni(0) / delta
  p3_rhoT = rho * R * t * delta * fidelta / 1000
End Function
Function u3_rhoT(ByVal rho As Double, ByVal t As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  '7 Basic Equation for Region 3, Section. 6.1 Basic Equation
  'Table 30 and 31, Page 30 and 31
  Dim i As Integer, Ji, Ii, ni As Variant, delta, tau, fitau As Double
  Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
  Ii = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 8, 9, 9, 10, 10, 11)
  Ji = Array(0, 0, 1, 2, 7, 10, 12, 23, 2, 6, 15, 17, 0, 2, 6, 7, 22, 26, 0, 2, 4, 16, 26, 0, 2, 4, 26, 1, 3, 26, 0, 2, 26, 2, 26, 2, 26, 0, 1, 26)
  ni = Array(1.0658070028513, -15.732845290239, 20.944396974307, -7.6867707878716, 2.6185947787954, -2.808078114862, 1.2053369696517, -8.4566812812502E-03, -1.2654315477714, -1.1524407806681, 0.88521043984318, -0.64207765181607, 0.38493460186671, -0.85214708824206, 4.8972281541877, -3.0502617256965, 0.039420536879154, 0.12558408424308, -0.2799932969871, 1.389979956946, -2.018991502357, -8.2147637173963E-03, -0.47596035734923, 0.0439840744735, -0.44476435428739, 0.90572070719733, 0.70522450087967, 0.10770512626332, -0.32913623258954, -0.50871062041158, -0.022175400873096, 0.094260751665092, 0.16436278447961, -0.013503372241348, -0.014834345352472, 5.7922953628084E-04, 3.2308904703711E-03, 8.0964802996215E-05, -1.6557679795037E-04, -4.4923899061815E-05)
  delta = rho / rhoc
  tau = tc / t
  fitau = 0
  For i = 1 To 39
    fitau = fitau + ni(i) * delta ^ Ii(i) * Ji(i) * tau ^ (Ji(i) - 1)
  Next i
  u3_rhoT = R * t * (tau * fitau)
End Function

Function h3_rhoT(ByVal rho As Double, ByVal t As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  '7 Basic Equation for Region 3, Section. 6.1 Basic Equation
  'Table 30 and 31, Page 30 and 31
  Dim i As Integer, Ji, Ii, ni As Variant, delta, tau, fidelta, fitau As Double
  Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
  Ii = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 8, 9, 9, 10, 10, 11)
  Ji = Array(0, 0, 1, 2, 7, 10, 12, 23, 2, 6, 15, 17, 0, 2, 6, 7, 22, 26, 0, 2, 4, 16, 26, 0, 2, 4, 26, 1, 3, 26, 0, 2, 26, 2, 26, 2, 26, 0, 1, 26)
  ni = Array(1.0658070028513, -15.732845290239, 20.944396974307, -7.6867707878716, 2.6185947787954, -2.808078114862, 1.2053369696517, -8.4566812812502E-03, -1.2654315477714, -1.1524407806681, 0.88521043984318, -0.64207765181607, 0.38493460186671, -0.85214708824206, 4.8972281541877, -3.0502617256965, 0.039420536879154, 0.12558408424308, -0.2799932969871, 1.389979956946, -2.018991502357, -8.2147637173963E-03, -0.47596035734923, 0.0439840744735, -0.44476435428739, 0.90572070719733, 0.70522450087967, 0.10770512626332, -0.32913623258954, -0.50871062041158, -0.022175400873096, 0.094260751665092, 0.16436278447961, -0.013503372241348, -0.014834345352472, 5.7922953628084E-04, 3.2308904703711E-03, 8.0964802996215E-05, -1.6557679795037E-04, -4.4923899061815E-05)
  delta = rho / rhoc
  tau = tc / t
  fidelta = 0
  fitau = 0
  For i = 1 To 39
    fidelta = fidelta + ni(i) * Ii(i) * delta ^ (Ii(i) - 1) * tau ^ Ji(i)
    fitau = fitau + ni(i) * delta ^ Ii(i) * Ji(i) * tau ^ (Ji(i) - 1)
  Next i
  fidelta = fidelta + ni(0) / delta
  h3_rhoT = R * t * (tau * fitau + delta * fidelta)
End Function
Function s3_rhoT(ByVal rho As Double, ByVal t As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  '7 Basic Equation for Region 3, Section. 6.1 Basic Equation
  'Table 30 and 31, Page 30 and 31
  Dim i As Integer, Ji, Ii, ni As Variant, fi, delta, tau, fitau As Double
  Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
  Ii = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 8, 9, 9, 10, 10, 11)
  Ji = Array(0, 0, 1, 2, 7, 10, 12, 23, 2, 6, 15, 17, 0, 2, 6, 7, 22, 26, 0, 2, 4, 16, 26, 0, 2, 4, 26, 1, 3, 26, 0, 2, 26, 2, 26, 2, 26, 0, 1, 26)
  ni = Array(1.0658070028513, -15.732845290239, 20.944396974307, -7.6867707878716, 2.6185947787954, -2.808078114862, 1.2053369696517, -8.4566812812502E-03, -1.2654315477714, -1.1524407806681, 0.88521043984318, -0.64207765181607, 0.38493460186671, -0.85214708824206, 4.8972281541877, -3.0502617256965, 0.039420536879154, 0.12558408424308, -0.2799932969871, 1.389979956946, -2.018991502357, -8.2147637173963E-03, -0.47596035734923, 0.0439840744735, -0.44476435428739, 0.90572070719733, 0.70522450087967, 0.10770512626332, -0.32913623258954, -0.50871062041158, -0.022175400873096, 0.094260751665092, 0.16436278447961, -0.013503372241348, -0.014834345352472, 5.7922953628084E-04, 3.2308904703711E-03, 8.0964802996215E-05, -1.6557679795037E-04, -4.4923899061815E-05)
  delta = rho / rhoc
  tau = tc / t
  fi = 0
  fitau = 0
  For i = 1 To 39
    fi = fi + ni(i) * delta ^ Ii(i) * tau ^ Ji(i)
    fitau = fitau + ni(i) * delta ^ Ii(i) * Ji(i) * tau ^ (Ji(i) - 1)
  Next i
  fi = fi + ni(0) * Log(delta)
  s3_rhoT = R * (tau * fitau - fi)
End Function
Function Cp3_rhoT(ByVal rho As Double, ByVal t As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  '7 Basic Equation for Region 3, Section. 6.1 Basic Equation
  'Table 30 and 31, Page 30 and 31
  Dim i As Integer, Ji, Ii, ni As Variant, fideltatau, fi, delta, tau, fitautau, fidelta, fideltatautau, fideltadelta As Double
  Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
  Ii = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 8, 9, 9, 10, 10, 11)
  Ji = Array(0, 0, 1, 2, 7, 10, 12, 23, 2, 6, 15, 17, 0, 2, 6, 7, 22, 26, 0, 2, 4, 16, 26, 0, 2, 4, 26, 1, 3, 26, 0, 2, 26, 2, 26, 2, 26, 0, 1, 26)
  ni = Array(1.0658070028513, -15.732845290239, 20.944396974307, -7.6867707878716, 2.6185947787954, -2.808078114862, 1.2053369696517, -8.4566812812502E-03, -1.2654315477714, -1.1524407806681, 0.88521043984318, -0.64207765181607, 0.38493460186671, -0.85214708824206, 4.8972281541877, -3.0502617256965, 0.039420536879154, 0.12558408424308, -0.2799932969871, 1.389979956946, -2.018991502357, -8.2147637173963E-03, -0.47596035734923, 0.0439840744735, -0.44476435428739, 0.90572070719733, 0.70522450087967, 0.10770512626332, -0.32913623258954, -0.50871062041158, -0.022175400873096, 0.094260751665092, 0.16436278447961, -0.013503372241348, -0.014834345352472, 5.7922953628084E-04, 3.2308904703711E-03, 8.0964802996215E-05, -1.6557679795037E-04, -4.4923899061815E-05)
  delta = rho / rhoc
  tau = tc / t
  fitautau = 0
  fidelta = 0
  fideltatau = 0
  fideltadelta = 0
  For i = 1 To 39
    fitautau = fitautau + ni(i) * delta ^ Ii(i) * Ji(i) * (Ji(i) - 1) * tau ^ (Ji(i) - 2)
    fidelta = fidelta + ni(i) * Ii(i) * delta ^ (Ii(i) - 1) * tau ^ Ji(i)
    fideltatau = fideltatau + ni(i) * Ii(i) * delta ^ (Ii(i) - 1) * Ji(i) * tau ^ (Ji(i) - 1)
    fideltadelta = fideltadelta + ni(i) * Ii(i) * (Ii(i) - 1) * delta ^ (Ii(i) - 2) * tau ^ Ji(i)
  Next i
  fidelta = fidelta + ni(0) / delta
  fideltadelta = fideltadelta - ni(0) / (delta ^ 2)
  Cp3_rhoT = R * (-(tau ^ 2 * fitautau) + (delta * fidelta - delta * tau * fideltatau) ^ 2 / (2 * delta * fidelta + delta ^ 2 * fideltadelta))
End Function
Function Cv3_rhoT(ByVal rho As Double, ByVal t As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  '7 Basic Equation for Region 3, Section. 6.1 Basic Equation
  'Table 30 and 31, Page 30 and 31
  Dim i As Integer, Ji, Ii, ni As Variant, fi, delta, tau, fitautau As Double
  Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
  Ii = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 8, 9, 9, 10, 10, 11)
  Ji = Array(0, 0, 1, 2, 7, 10, 12, 23, 2, 6, 15, 17, 0, 2, 6, 7, 22, 26, 0, 2, 4, 16, 26, 0, 2, 4, 26, 1, 3, 26, 0, 2, 26, 2, 26, 2, 26, 0, 1, 26)
  ni = Array(1.0658070028513, -15.732845290239, 20.944396974307, -7.6867707878716, 2.6185947787954, -2.808078114862, 1.2053369696517, -8.4566812812502E-03, -1.2654315477714, -1.1524407806681, 0.88521043984318, -0.64207765181607, 0.38493460186671, -0.85214708824206, 4.8972281541877, -3.0502617256965, 0.039420536879154, 0.12558408424308, -0.2799932969871, 1.389979956946, -2.018991502357, -8.2147637173963E-03, -0.47596035734923, 0.0439840744735, -0.44476435428739, 0.90572070719733, 0.70522450087967, 0.10770512626332, -0.32913623258954, -0.50871062041158, -0.022175400873096, 0.094260751665092, 0.16436278447961, -0.013503372241348, -0.014834345352472, 5.7922953628084E-04, 3.2308904703711E-03, 8.0964802996215E-05, -1.6557679795037E-04, -4.4923899061815E-05)
  delta = rho / rhoc
  tau = tc / t
  fitautau = 0
  For i = 1 To 39
    fitautau = fitautau + ni(i) * delta ^ Ii(i) * Ji(i) * (Ji(i) - 1) * tau ^ (Ji(i) - 2)
  Next i
  Cv3_rhoT = R * -(tau * tau * fitautau)
End Function
Function w3_rhoT(ByVal rho As Double, ByVal t As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  '7 Basic Equation for Region 3, Section. 6.1 Basic Equation
  'Table 30 and 31, Page 30 and 31
  Dim i As Integer, Ji, Ii, ni As Variant, fi, delta, tau, fitautau, fidelta, fideltatau, fideltadelta As Double
  Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
  Ii = Array(0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 6, 7, 8, 9, 9, 10, 10, 11)
  Ji = Array(0, 0, 1, 2, 7, 10, 12, 23, 2, 6, 15, 17, 0, 2, 6, 7, 22, 26, 0, 2, 4, 16, 26, 0, 2, 4, 26, 1, 3, 26, 0, 2, 26, 2, 26, 2, 26, 0, 1, 26)
  ni = Array(1.0658070028513, -15.732845290239, 20.944396974307, -7.6867707878716, 2.6185947787954, -2.808078114862, 1.2053369696517, -8.4566812812502E-03, -1.2654315477714, -1.1524407806681, 0.88521043984318, -0.64207765181607, 0.38493460186671, -0.85214708824206, 4.8972281541877, -3.0502617256965, 0.039420536879154, 0.12558408424308, -0.2799932969871, 1.389979956946, -2.018991502357, -8.2147637173963E-03, -0.47596035734923, 0.0439840744735, -0.44476435428739, 0.90572070719733, 0.70522450087967, 0.10770512626332, -0.32913623258954, -0.50871062041158, -0.022175400873096, 0.094260751665092, 0.16436278447961, -0.013503372241348, -0.014834345352472, 5.7922953628084E-04, 3.2308904703711E-03, 8.0964802996215E-05, -1.6557679795037E-04, -4.4923899061815E-05)
  delta = rho / rhoc
  tau = tc / t
  fitautau = 0
  fidelta = 0
  fideltatau = 0
  fideltadelta = 0
  For i = 1 To 39
    fitautau = fitautau + ni(i) * delta ^ Ii(i) * Ji(i) * (Ji(i) - 1) * tau ^ (Ji(i) - 2)
    fidelta = fidelta + ni(i) * Ii(i) * delta ^ (Ii(i) - 1) * tau ^ Ji(i)
    fideltatau = fideltatau + ni(i) * Ii(i) * delta ^ (Ii(i) - 1) * Ji(i) * tau ^ (Ji(i) - 1)
    fideltadelta = fideltadelta + ni(i) * Ii(i) * (Ii(i) - 1) * delta ^ (Ii(i) - 2) * tau ^ Ji(i)
  Next i
  fidelta = fidelta + ni(0) / delta
  fideltadelta = fideltadelta - ni(0) / (delta ^ 2)
  w3_rhoT = (1000 * R * t * (2 * delta * fidelta + delta ^ 2 * fideltadelta - (delta * fidelta - delta * tau * fideltatau) ^ 2 / (tau ^ 2 * fitautau))) ^ 0.5
End Function
Function T3_ph(ByVal p As Double, ByVal h As Double) As Double
'Revised Supplementary Release on Backward Equations for the Functions T(p,h), v(p,h) and T(p,s), v(p,s) for Region 3 of the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
'2004
'Section 3.3 Backward Equations T(p,h) and v(p,h) for Subregions 3a and 3b
'Boundary equation, Eq 1 Page 5
 Dim i As Integer, Ji, Ii, ni As Variant, h3ab, ps, hs, Ts As Double
 Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
 h3ab = (2014.64004206875 + 3.74696550136983 * p - 2.19921901054187E-02 * p ^ 2 + 8.7513168600995E-05 * p ^ 3)
  If h < h3ab Then
    'Subregion 3a
    'Eq 2, Table 3, Page 7
    Ii = Array(-12, -12, -12, -12, -12, -12, -12, -12, -10, -10, -10, -8, -8, -8, -8, -5, -3, -2, -2, -2, -1, -1, 0, 0, 1, 3, 3, 4, 4, 10, 12)
    Ji = Array(0, 1, 2, 6, 14, 16, 20, 22, 1, 5, 12, 0, 2, 4, 10, 2, 0, 1, 3, 4, 0, 2, 0, 1, 1, 0, 1, 0, 3, 4, 5)
    ni = Array(-1.33645667811215E-07, 4.55912656802978E-06, -1.46294640700979E-05, 6.3934131297008E-03, 372.783927268847, -7186.54377460447, 573494.7521034, -2675693.29111439, -3.34066283302614E-05, -2.45479214069597E-02, 47.8087847764996, 7.64664131818904E-06, 1.28350627676972E-03, 1.71219081377331E-02, -8.51007304583213, -1.36513461629781E-02, -3.84460997596657E-06, 3.37423807911655E-03, -0.551624873066791, 0.72920227710747, -9.92522757376041E-03, -0.119308831407288, 0.793929190615421, 0.454270731799386, 0.20999859125991, -6.42109823904738E-03, -0.023515586860454, 2.52233108341612E-03, -7.64885133368119E-03, 1.36176427574291E-02, -1.33027883575669E-02)
    ps = p / 100
    hs = h / 2300
    Ts = 0
    For i = 0 To 30
      Ts = Ts + ni(i) * (ps + 0.24) ^ Ii(i) * (hs - 0.615) ^ Ji(i)
    Next i
    T3_ph = Ts * 760
  Else
    'Subregion 3b
    'Eq 3, Table 4, Page 7,8
    Ii = Array(-12, -12, -10, -10, -10, -10, -10, -8, -8, -8, -8, -8, -6, -6, -6, -4, -4, -3, -2, -2, -1, -1, -1, -1, -1, -1, 0, 0, 1, 3, 5, 6, 8)
    Ji = Array(0, 1, 0, 1, 5, 10, 12, 0, 1, 2, 4, 10, 0, 1, 2, 0, 1, 5, 0, 4, 2, 4, 6, 10, 14, 16, 0, 2, 1, 1, 1, 1, 1)
    ni = Array(3.2325457364492E-05, -1.27575556587181E-04, -4.75851877356068E-04, 1.56183014181602E-03, 0.105724860113781, -85.8514221132534, 724.140095480911, 2.96475810273257E-03, -5.92721983365988E-03, -1.26305422818666E-02, -0.115716196364853, 84.9000969739595, -1.08602260086615E-02, 1.54304475328851E-02, 7.50455441524466E-02, 2.52520973612982E-02, -6.02507901232996E-02, -3.07622221350501, -5.74011959864879E-02, 5.03471360939849, -0.925081888584834, 3.91733882917546, -77.314600713019, 9493.08762098587, -1410437.19679409, 8491662.30819026, 0.861095729446704, 0.32334644281172, 0.873281936020439, -0.436653048526683, 0.286596714529479, -0.131778331276228, 6.76682064330275E-03)
    hs = h / 2800
    ps = p / 100
    Ts = 0
    For i = 0 To 32
      Ts = Ts + ni(i) * (ps + 0.298) ^ Ii(i) * (hs - 0.72) ^ Ji(i)
    Next i
    T3_ph = Ts * 860
  End If
End Function
Function v3_ph(ByVal p As Double, ByVal h As Double) As Double
'Revised Supplementary Release on Backward Equations for the Functions T(p,h), v(p,h) and T(p,s), v(p,s) for Region 3 of the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
'2004
'Section 3.3 Backward Equations T(p,h) and v(p,h) for Subregions 3a and 3b
'Boundary equation, Eq 1 Page 5
 Dim i As Integer, Ji, Ii, ni As Variant, h3ab, ps, hs, vs As Double
 Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
  h3ab = (2014.64004206875 + 3.74696550136983 * p - 2.19921901054187E-02 * p ^ 2 + 8.7513168600995E-05 * p ^ 3)
  If h < h3ab Then
    'Subregion 3a
    'Eq 4, Table 6, Page 9
    Ii = Array(-12, -12, -12, -12, -10, -10, -10, -8, -8, -6, -6, -6, -4, -4, -3, -2, -2, -1, -1, -1, -1, 0, 0, 1, 1, 1, 2, 2, 3, 4, 5, 8)
    Ji = Array(6, 8, 12, 18, 4, 7, 10, 5, 12, 3, 4, 22, 2, 3, 7, 3, 16, 0, 1, 2, 3, 0, 1, 0, 1, 2, 0, 2, 0, 2, 2, 2)
    ni = Array(5.29944062966028E-03, -0.170099690234461, 11.1323814312927, -2178.98123145125, -5.06061827980875E-04, 0.556495239685324, -9.43672726094016, -0.297856807561527, 93.9353943717186, 1.92944939465981E-02, 0.421740664704763, -3689141.2628233, -7.37566847600639E-03, -0.354753242424366, -1.99768169338727, 1.15456297059049, 5683.6687581596, 8.08169540124668E-03, 0.172416341519307, 1.04270175292927, -0.297691372792847, 0.560394465163593, 0.275234661176914, -0.148347894866012, -6.51142513478515E-02, -2.92468715386302, 6.64876096952665E-02, 3.52335014263844, -1.46340792313332E-02, -2.24503486668184, 1.10533464706142, -4.08757344495612E-02)
    ps = p / 100
    hs = h / 2100
    vs = 0
    For i = 0 To 31
      vs = vs + ni(i) * (ps + 0.128) ^ Ii(i) * (hs - 0.727) ^ Ji(i)
    Next i
    v3_ph = vs * 0.0028
  Else
    'Subregion 3b
    'Eq 5, Table 7, Page 9
    Ii = Array(-12, -12, -8, -8, -8, -8, -8, -8, -6, -6, -6, -6, -6, -6, -4, -4, -4, -3, -3, -2, -2, -1, -1, -1, -1, 0, 1, 1, 2, 2)
    Ji = Array(0, 1, 0, 1, 3, 6, 7, 8, 0, 1, 2, 5, 6, 10, 3, 6, 10, 0, 2, 1, 2, 0, 1, 4, 5, 0, 0, 1, 2, 6)
    ni = Array(-2.25196934336318E-09, 1.40674363313486E-08, 2.3378408528056E-06, -3.31833715229001E-05, 1.07956778514318E-03, -0.271382067378863, 1.07202262490333, -0.853821329075382, -2.15214194340526E-05, 7.6965608822273E-04, -4.31136580433864E-03, 0.453342167309331, -0.507749535873652, -100.475154528389, -0.219201924648793, -3.21087965668917, 607.567815637771, 5.57686450685932E-04, 0.18749904002955, 9.05368030448107E-03, 0.285417173048685, 3.29924030996098E-02, 0.239897419685483, 4.82754995951394, -11.8035753702231, 0.169490044091791, -1.79967222507787E-02, 3.71810116332674E-02, -5.36288335065096E-02, 1.6069710109252)
    ps = p / 100
    hs = h / 2800
    vs = 0
    For i = 0 To 29
      vs = vs + ni(i) * (ps + 0.0661) ^ Ii(i) * (hs - 0.72) ^ Ji(i)
    Next i
    v3_ph = vs * 0.0088
  End If
End Function
Function T3_ps(ByVal p As Double, ByVal s As Double) As Double
'Revised Supplementary Release on Backward Equations for the Functions T(p,h), v(p,h) and T(p,s), v(p,s) for Region 3 of the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
'2004
'3.4 Backward Equations T(p,s) and v(p,s) for Subregions 3a and 3b
'Boundary equation, Eq 6 Page 11
 Dim i As Integer, Ji, Ii, ni As Variant, ps, sigma, teta As Double
 Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322

  If s <= 4.41202148223476 Then
    'Subregion 3a
    'Eq 6, Table 10, Page 11
    Ii = Array(-12, -12, -10, -10, -10, -10, -8, -8, -8, -8, -6, -6, -6, -5, -5, -5, -4, -4, -4, -2, -2, -1, -1, 0, 0, 0, 1, 2, 2, 3, 8, 8, 10)
    Ji = Array(28, 32, 4, 10, 12, 14, 5, 7, 8, 28, 2, 6, 32, 0, 14, 32, 6, 10, 36, 1, 4, 1, 6, 0, 1, 4, 0, 0, 3, 2, 0, 1, 2)
    ni = Array(1500420082.63875, -159397258480.424, 5.02181140217975E-04, -67.2057767855466, 1450.58545404456, -8238.8953488889, -0.154852214233853, 11.2305046746695, -29.7000213482822, 43856513263.5495, 1.37837838635464E-03, -2.97478527157462, 9717779473494.13, -5.71527767052398E-05, 28830.794977842, -74442828926270.3, 12.8017324848921, -368.275545889071, 6.64768904779177E+15, 0.044935925195888, -4.22897836099655, -0.240614376434179, -4.74341365254924, 0.72409399912611, 0.923874349695897, 3.99043655281015, 3.84066651868009E-02, -3.59344365571848E-03, -0.735196448821653, 0.188367048396131, 1.41064266818704E-04, -2.57418501496337E-03, 1.23220024851555E-03)
    sigma = s / 4.4
    ps = p / 100
    teta = 0
    For i = 0 To 32
      teta = teta + ni(i) * (ps + 0.24) ^ Ii(i) * (sigma - 0.703) ^ Ji(i)
    Next i
    T3_ps = teta * 760
  Else
    'Subregion 3b
    'Eq 7, Table 11, Page 11
    Ii = Array(-12, -12, -12, -12, -8, -8, -8, -6, -6, -6, -5, -5, -5, -5, -5, -4, -3, -3, -2, 0, 2, 3, 4, 5, 6, 8, 12, 14)
    Ji = Array(1, 3, 4, 7, 0, 1, 3, 0, 2, 4, 0, 1, 2, 4, 6, 12, 1, 6, 2, 0, 1, 1, 0, 24, 0, 3, 1, 2)
    ni = Array(0.52711170160166, -40.1317830052742, 153.020073134484, -2247.99398218827, -0.193993484669048, -1.40467557893768, 42.6799878114024, 0.752810643416743, 22.6657238616417, -622.873556909932, -0.660823667935396, 0.841267087271658, -25.3717501764397, 485.708963532948, 880.531517490555, 2650155.92794626, -0.359287150025783, -656.991567673753, 2.41768149185367, 0.856873461222588, 0.655143675313458, -0.213535213206406, 5.62974957606348E-03, -316955725450471#, -6.99997000152457E-04, 1.19845803210767E-02, 1.93848122022095E-05, -2.15095749182309E-05)
    sigma = s / 5.3
    ps = p / 100
    teta = 0
    For i = 0 To 27
      teta = teta + ni(i) * (ps + 0.76) ^ Ii(i) * (sigma - 0.818) ^ Ji(i)
    Next i
    T3_ps = teta * 860
  End If
End Function
Function v3_ps(ByVal p As Double, ByVal s As Double) As Double
'Revised Supplementary Release on Backward Equations for the Functions T(p,h), v(p,h) and T(p,s), v(p,s) for Region 3 of the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
'2004
'3.4 Backward Equations T(p,s) and v(p,s) for Subregions 3a and 3b
'Boundary equation, Eq 6 Page 11
 Dim i As Integer, Ji, Ii, ni As Variant, ps, sigma, omega As Double
 Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
  If s <= 4.41202148223476 Then
    'Subregion 3a
    'Eq 8, Table 13, Page 14
    Ii = Array(-12, -12, -12, -10, -10, -10, -10, -8, -8, -8, -8, -6, -5, -4, -3, -3, -2, -2, -1, -1, 0, 0, 0, 1, 2, 4, 5, 6)
    Ji = Array(10, 12, 14, 4, 8, 10, 20, 5, 6, 14, 16, 28, 1, 5, 2, 4, 3, 8, 1, 2, 0, 1, 3, 0, 0, 2, 2, 0)
    ni = Array(79.5544074093975, -2382.6124298459, 17681.3100617787, -1.10524727080379E-03, -15.3213833655326, 297.544599376982, -35031520.6871242, 0.277513761062119, -0.523964271036888, -148011.182995403, 1600148.99374266, 1708023226634.27, 2.46866996006494E-04, 1.6532608479798, -0.118008384666987, 2.537986423559, 0.965127704669424, -28.2172420532826, 0.203224612353823, 1.10648186063513, 0.52612794845128, 0.277000018736321, 1.08153340501132, -7.44127885357893E-02, 1.64094443541384E-02, -6.80468275301065E-02, 0.025798857610164, -1.45749861944416E-04)
    ps = p / 100
    sigma = s / 4.4
    omega = 0
    For i = 0 To 27
      omega = omega + ni(i) * (ps + 0.187) ^ Ii(i) * (sigma - 0.755) ^ Ji(i)
    Next i
    v3_ps = omega * 0.0028
  Else
    'Subregion 3b
    'Eq 9, Table 14, Page 14
    Ii = Array(-12, -12, -12, -12, -12, -12, -10, -10, -10, -10, -8, -5, -5, -5, -4, -4, -4, -4, -3, -2, -2, -2, -2, -2, -2, 0, 0, 0, 1, 1, 2)
    Ji = Array(0, 1, 2, 3, 5, 6, 0, 1, 2, 4, 0, 1, 2, 3, 0, 1, 2, 3, 1, 0, 1, 2, 3, 4, 12, 0, 1, 2, 0, 2, 2)
    ni = Array(5.91599780322238E-05, -1.85465997137856E-03, 1.04190510480013E-02, 5.9864730203859E-03, -0.771391189901699, 1.72549765557036, -4.67076079846526E-04, 1.34533823384439E-02, -8.08094336805495E-02, 0.508139374365767, 1.28584643361683E-03, -1.63899353915435, 5.86938199318063, -2.92466667918613, -6.14076301499537E-03, 5.76199014049172, -12.1613320606788, 1.67637540957944, -7.44135838773463, 3.78168091437659E-02, 4.01432203027688, 16.0279837479185, 3.17848779347728, -3.58362310304853, -1159952.60446827, 0.199256573577909, -0.122270624794624, -19.1449143716586, -1.50448002905284E-02, 14.6407900162154, -3.2747778718823)
    ps = p / 100
    sigma = s / 5.3
    omega = 0
    For i = 0 To 30
      omega = omega + ni(i) * (ps + 0.298) ^ Ii(i) * (sigma - 0.816) ^ Ji(i)
   Next i
   v3_ps = omega * 0.0088
  End If
End Function

Function p3_hs(ByVal h As Double, ByVal s As Double) As Double
'Supplementary Release on Backward Equations ( ) , p h s for Region 3,
'Equations as a Function of h and s for the Region Boundaries, and an Equation
'( ) sat , T hs for Region 4 of the IAPWS Industrial Formulation 1997 for the
'Thermodynamic Properties of Water and Steam
'2004
'Section 3 Backward Functions p(h,s), T(h,s), and v(h,s) for Region 3
 Dim i As Integer, Ji, Ii, ni As Variant, ps, sigma, eta As Double
 Const R As Double = 0.461526, tc As Double = 647.096, pc As Double = 22.064, rhoc As Double = 322
  If s < 4.41202148223476 Then
    'Subregion 3a
    'Eq 1, Table 3, Page 8
    Ii = Array(0, 0, 0, 1, 1, 1, 1, 1, 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 6, 7, 8, 10, 10, 14, 18, 20, 22, 22, 24, 28, 28, 32, 32)
    Ji = Array(0, 1, 5, 0, 3, 4, 8, 14, 6, 16, 0, 2, 3, 0, 1, 4, 5, 28, 28, 24, 1, 32, 36, 22, 28, 36, 16, 28, 36, 16, 36, 10, 28)
    ni = Array(7.70889828326934, -26.0835009128688, 267.416218930389, 17.2221089496844, -293.54233214597, 614.135601882478, -61056.2757725674, -65127225.1118219, 73591.9313521937, -11664650591.4191, 35.5267086434461, -596.144543825955, -475.842430145708, 69.6781965359503, 335.674250377312, 25052.6809130882, 146997.380630766, 5.38069315091534E+19, 1.43619827291346E+21, 3.64985866165994E+19, -2547.41561156775, 2.40120197096563E+27, -3.93847464679496E+29, 1.47073407024852E+24, -4.26391250432059E+31, 1.94509340621077E+38, 6.66212132114896E+23, 7.06777016552858E+33, 1.75563621975576E+41, 1.08408607429124E+28, 7.30872705175151E+43, 1.5914584739887E+24, 3.77121605943324E+40)
    sigma = s / 4.4
    eta = h / 2300
    ps = 0
    For i = 0 To 32
      ps = ps + ni(i) * (eta - 1.01) ^ Ii(i) * (sigma - 0.75) ^ Ji(i)
    Next i
    p3_hs = ps * 99
  Else
    'Subregion 3b
    'Eq 2, Table 4, Page 8
    Ii = Array(-12, -12, -12, -12, -12, -10, -10, -10, -10, -8, -8, -6, -6, -6, -6, -5, -4, -4, -4, -3, -3, -3, -3, -2, -2, -1, 0, 2, 2, 5, 6, 8, 10, 14, 14)
    Ji = Array(2, 10, 12, 14, 20, 2, 10, 14, 18, 2, 8, 2, 6, 7, 8, 10, 4, 5, 8, 1, 3, 5, 6, 0, 1, 0, 3, 0, 1, 0, 1, 1, 1, 3, 7)
    ni = Array(1.25244360717979E-13, -1.26599322553713E-02, 5.06878030140626, 31.7847171154202, -391041.161399932, -9.75733406392044E-11, -18.6312419488279, 510.973543414101, 373847.005822362, 2.99804024666572E-08, 20.0544393820342, -4.98030487662829E-06, -10.230180636003, 55.2819126990325, -206.211367510878, -7940.12232324823, 7.82248472028153, -58.6544326902468, 3550.73647696481, -1.15303107290162E-04, -1.75092403171802, 257.98168774816, -727.048374179467, 1.21644822609198E-04, 3.93137871762692E-02, 7.04181005909296E-03, -82.910820069811, -0.26517881813125, 13.7531682453991, -52.2394090753046, 2405.56298941048, -22736.1631268929, 89074.6343932567, -23923456.5822486, 5687958081.29714)
    sigma = s / 5.3
    eta = h / 2800
    ps = 0
    For i = 0 To 34
      ps = ps + ni(i) * (eta - 0.681) ^ Ii(i) * (sigma - 0.792) ^ Ji(i)
    Next i
    p3_hs = 16.6 / ps
  End If
End Function
Function h3_pT(ByVal p As Double, ByVal t As Double) As Double
   'Not avalible with IF 97
   'Solve function T3_ph-T=0 with half interval method.
   Dim Ts, Low_Bound, High_Bound, hs As Double
   'ver2.6 Start corrected bug
   If p < 22.06395 Then   'Bellow tripple point
     Ts = T4_p(p)    'Saturation temperature
     If t <= Ts Then   'Liquid side
       High_Bound = h4L_p(p) 'Max h är liauid h.
       Low_Bound = h1_pT(p, 623.15)
     Else
       Low_Bound = h4V_p(p)  'Min h är Vapour h.
       High_Bound = h2_pT(p, B23T_p(p))
     End If
   Else                  'Above tripple point. R3 from R2 till R3.
     Low_Bound = h1_pT(p, 623.15)
     High_Bound = h2_pT(p, B23T_p(p))
   End If
   'ver2.6 End corrected bug
   Ts = t + 1
   Do While Abs(t - Ts) > 0.000001
    hs = (Low_Bound + High_Bound) / 2
    Ts = T3_ph(p, hs)
    If Ts > t Then
      High_Bound = hs
    Else
      Low_Bound = hs
    End If
   Loop
   h3_pT = hs
End Function
Function T3_prho(ByVal p As Double, ByVal rho As Double)
  'Solve by iteration. Observe that fo low temperatures this equation has 2 solutions.
  'Solve with half interval method
  Dim ps, Low_Bound, High_Bound, Ts As Double
  Low_Bound = 623.15
  High_Bound = 1073.15
  Do While Abs(p - ps) > 0.00000001
    Ts = (Low_Bound + High_Bound) / 2
    ps = p3_rhoT(rho, Ts)
    If ps > p Then
      High_Bound = Ts
    Else
      Low_Bound = Ts
    End If
    Loop
    T3_prho = Ts
End Function

'***********************************************************************************************************
'*2.4 Functions for region 4
Function p4_T(ByVal t As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  'Section 8.1 The Saturation-Pressure Equation
  'Eq 30, Page 33
  Dim teta, a, b, c As Double
  teta = t - 0.23855557567849 / (t - 650.17534844798)
  a = teta ^ 2 + 1167.0521452767 * teta - 724213.16703206
  b = -17.073846940092 * teta ^ 2 + 12020.82470247 * teta - 3232555.0322333
  c = 14.91510861353 * teta ^ 2 - 4823.2657361591 * teta + 405113.40542057
  p4_T = (2 * c / (-b + (b ^ 2 - 4 * a * c) ^ 0.5)) ^ 4
End Function

Function T4_p(ByVal p As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  'Section 8.2 The Saturation-Temperature Equation
  'Eq 31, Page 34
  Dim beta, e, f, g, d As Double
  beta = p ^ 0.25
  e = beta ^ 2 - 17.073846940092 * beta + 14.91510861353
  f = 1167.0521452767 * beta ^ 2 + 12020.82470247 * beta - 4823.2657361591
  g = -724213.16703206 * beta ^ 2 - 3232555.0322333 * beta + 405113.40542057
  d = 2 * g / (-f - (f ^ 2 - 4 * e * g) ^ 0.5)
  T4_p = (650.17534844798 + d - ((650.17534844798 + d) ^ 2 - 4 * (-0.23855557567849 + 650.17534844798 * d)) ^ 0.5) / 2
End Function
Function h4_s(ByVal s As Double) As Double
'Supplementary Release on Backward Equations ( ) , p h s for Region 3,Equations as a Function of h and s for the Region Boundaries, and an Equation( ) sat , T hs for Region 4 of the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
'4 Equations for Region Boundaries Given Enthalpy and Entropy
' Se picture page 14
Dim Ii, Ji, ni As Variant, eta, sigma, sigma1, sigma2 As Double, i As Integer
  If s > -0.0001545495919 And s <= 3.77828134 Then
    'hL1_s
    'Eq 3,Table 9,Page 16
    Ii = Array(0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 4, 5, 5, 7, 8, 12, 12, 14, 14, 16, 20, 20, 22, 24, 28, 32, 32)
    Ji = Array(14, 36, 3, 16, 0, 5, 4, 36, 4, 16, 24, 18, 24, 1, 4, 2, 4, 1, 22, 10, 12, 28, 8, 3, 0, 6, 8)
    ni = Array(0.332171191705237, 6.11217706323496E-04, -8.82092478906822, -0.45562819254325, -2.63483840850452E-05, -22.3949661148062, -4.28398660164013, -0.616679338856916, -14.682303110404, 284.523138727299, -113.398503195444, 1156.71380760859, 395.551267359325, -1.54891257229285, 19.4486637751291, -3.57915139457043, -3.35369414148819, -0.66442679633246, 32332.1885383934, 3317.66744667084, -22350.1257931087, 5739538.75852936, 173.226193407919, -3.63968822121321E-02, 8.34596332878346E-07, 5.03611916682674, 65.5444787064505)
    sigma = s / 3.8
    eta = 0
    For i = 0 To 26
      eta = eta + ni(i) * (sigma - 1.09) ^ Ii(i) * (sigma + 0.0000366) ^ Ji(i)
    Next i
    h4_s = eta * 1700
  ElseIf s > 3.77828134 And s <= 4.41202148223476 Then
    'hL3_s
    'Eq 4,Table 10,Page 16
    Ii = Array(0, 0, 0, 0, 2, 3, 4, 4, 5, 5, 6, 7, 7, 7, 10, 10, 10, 32, 32)
    Ji = Array(1, 4, 10, 16, 1, 36, 3, 16, 20, 36, 4, 2, 28, 32, 14, 32, 36, 0, 6)
    ni = Array(0.822673364673336, 0.181977213534479, -0.011200026031362, -7.46778287048033E-04, -0.179046263257381, 4.24220110836657E-02, -0.341355823438768, -2.09881740853565, -8.22477343323596, -4.99684082076008, 0.191413958471069, 5.81062241093136E-02, -1655.05498701029, 1588.70443421201, -85.0623535172818, -31771.4386511207, -94589.0406632871, -1.3927384708869E-06, 0.63105253224098)
    sigma = s / 3.8
    eta = 0
    For i = 0 To 18
      eta = eta + ni(i) * (sigma - 1.09) ^ Ii(i) * (sigma + 0.0000366) ^ Ji(i)
    Next i
    h4_s = eta * 1700
  ElseIf s > 4.41202148223476 And s <= 5.85 Then
    'Section 4.4 Equations ( ) 2ab " h s and ( ) 2c3b "h s for the Saturated Vapor Line
    'Page 19, Eq 5
    'hV2c3b_s(s)
    Ii = Array(0, 0, 0, 1, 1, 5, 6, 7, 8, 8, 12, 16, 22, 22, 24, 36)
    Ji = Array(0, 3, 4, 0, 12, 36, 12, 16, 2, 20, 32, 36, 2, 32, 7, 20)
    ni = Array(1.04351280732769, -2.27807912708513, 1.80535256723202, 0.420440834792042, -105721.24483466, 4.36911607493884E+24, -328032702839.753, -6.7868676080427E+15, 7439.57464645363, -3.56896445355761E+19, 1.67590585186801E+31, -3.55028625419105E+37, 396611982166.538, -4.14716268484468E+40, 3.59080103867382E+18, -1.16994334851995E+40)
    sigma = s / 5.9
    eta = 0
    For i = 0 To 15
      eta = eta + ni(i) * (sigma - 1.02) ^ Ii(i) * (sigma - 0.726) ^ Ji(i)
    Next i
    h4_s = eta ^ 4 * 2800
  ElseIf s > 5.85 And s < 9.155759395 Then
    'Section 4.4 Equations ( ) 2ab " h s and ( ) 2c3b "h s for the Saturated Vapor Line
    'Page 20, Eq 6
    Ii = Array(1, 1, 2, 2, 4, 4, 7, 8, 8, 10, 12, 12, 18, 20, 24, 28, 28, 28, 28, 28, 32, 32, 32, 32, 32, 36, 36, 36, 36, 36)
    Ji = Array(8, 24, 4, 32, 1, 2, 7, 5, 12, 1, 0, 7, 10, 12, 32, 8, 12, 20, 22, 24, 2, 7, 12, 14, 24, 10, 12, 20, 22, 28)
    ni = Array(-524.581170928788, -9269472.18142218, -237.385107491666, 21077015581.2776, -23.9494562010986, 221.802480294197, -5104725.33393438, 1249813.96109147, 2000084369.96201, -815.158509791035, -157.612685637523, -11420042233.2791, 6.62364680776872E+15, -2.27622818296144E+18, -1.71048081348406E+31, 6.60788766938091E+15, 1.66320055886021E+22, -2.18003784381501E+29, -7.87276140295618E+29, 1.51062329700346E+31, 7957321.70300541, 1.31957647355347E+15, -3.2509706829914E+23, -4.18600611419248E+25, 2.97478906557467E+34, -9.53588761745473E+19, 1.66957699620939E+24, -1.75407764869978E+32, 3.47581490626396E+34, -7.10971318427851E+38)
    sigma1 = s / 5.21
    sigma2 = s / 9.2
    eta = 0
    For i = 0 To 29
      eta = eta + ni(i) * (1 / sigma1 - 0.513) ^ Ii(i) * (sigma2 - 0.524) ^ Ji(i)
    Next i
    h4_s = Exp(eta) * 2800
  Else
    h4_s = CVErr(xlErrValue)
  End If
End Function
Function p4_s(ByVal s As Double) As Double
  'Uses h4_s and p_hs for the diffrent regions to determine p4_s
  Dim hsat As Double
  hsat = h4_s(s)
  If s > -0.0001545495919 And s <= 3.77828134 Then
    p4_s = p1_hs(hsat, s)
  ElseIf s > 3.77828134 And s <= 5.210887663 Then
    p4_s = p3_hs(hsat, s)
  ElseIf s > 5.210887663 And s < 9.155759395 Then
    p4_s = p2_hs(hsat, s)
  Else
    p4_s = CVErr(xlErrValue)
  End If
End Function
Function h4L_p(ByVal p As Double) As Double
 Dim Low_Bound, High_Bound, hs, ps, Ts As Double
 If p > 0.000611657 And p < 22.06395 Then
  Ts = T4_p(p)
  If p < 16.529 Then
    h4L_p = h1_pT(p, Ts)
  Else
    'Iterate to find the the backward solution of p3sat_h
    Low_Bound = 1670.858218
    High_Bound = 2087.23500164864
    Do While Abs(p - ps) > 0.00001
      hs = (Low_Bound + High_Bound) / 2
      ps = p3sat_h(hs)
      If ps > p Then
        High_Bound = hs
      Else
        Low_Bound = hs
      End If
    Loop

    h4L_p = hs
  End If
 Else
  h4L_p = CVErr(xlErrValue)
 End If
End Function
Function h4V_p(ByVal p As Double) As Double
 Dim Low_Bound, High_Bound, hs, ps, Ts As Double
 If p > 0.000611657 And p < 22.06395 Then
  Ts = T4_p(p)
  If p < 16.529 Then
    h4V_p = h2_pT(p, Ts)
  Else
    'Iterate to find the the backward solution of p3sat_h
    Low_Bound = 2087.23500164864
    High_Bound = 2563.592004 + 5 '5 added to extrapolate to ensure even the border ==350°C solved.
    Do While Abs(p - ps) > 0.000001
      hs = (Low_Bound + High_Bound) / 2
      ps = p3sat_h(hs)
      If ps < p Then
        High_Bound = hs
      Else
        Low_Bound = hs
      End If
    Loop
    h4V_p = hs
  End If
 Else
  h4V_p = CVErr(xlErrValue)
 End If
End Function
Function x4_ph(ByVal p As Double, ByVal h As Double) As Double
'Calculate vapour fraction from hL and hV for given p
 Dim h4v, h4l As Double
  h4v = h4V_p(p)
  h4l = h4L_p(p)
  If h > h4v Then
    x4_ph = 1
  ElseIf h < h4l Then
    x4_ph = 0
  Else
    x4_ph = (h - h4l) / (h4v - h4l)
  End If
End Function
Function x4_ps(ByVal p As Double, ByVal s As Double) As Double
 Dim ssV, ssL As Double
  If p < 16.529 Then
   ssV = s2_pT(p, T4_p(p))
   ssL = s1_pT(p, T4_p(p))
  Else
   ssV = s3_rhoT(1 / (v3_ph(p, h4V_p(p))), T4_p(p))
   ssL = s3_rhoT(1 / (v3_ph(p, h4L_p(p))), T4_p(p))
  End If
  If s < ssL Then
    x4_ps = 0
  ElseIf s > ssV Then
    x4_ps = 1
  Else
    x4_ps = (s - ssL) / (ssV - ssL)
  End If
End Function
Function T4_hs(ByVal h As Double, ByVal s As Double) As Double
'Supplementary Release on Backward Equations ( ) , p h s for Region 3,
'Chapter 5.3 page 30.
'The if 97 function is only valid for part of region4. Use iteration outsida.
 Dim Ii, Ji, ni As Variant, hL, Ts, ss, p, sigma, eta, teta, High_Bound, Low_Bound, PL, s4V, v4V, s4L, v4L, xs As Double, i As Integer
   Ii = Array(0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 3, 4, 4, 5, 5, 5, 5, 6, 6, 6, 8, 10, 10, 12, 14, 14, 16, 16, 18, 18, 18, 20, 28)
   Ji = Array(0, 3, 12, 0, 1, 2, 5, 0, 5, 8, 0, 2, 3, 4, 0, 1, 1, 2, 4, 16, 6, 8, 22, 1, 20, 36, 24, 1, 28, 12, 32, 14, 22, 36, 24, 36)
   ni = Array(0.179882673606601, -0.267507455199603, 1.162767226126, 0.147545428713616, -0.512871635973248, 0.421333567697984, 0.56374952218987, 0.429274443819153, -3.3570455214214, 10.8890916499278, -0.248483390456012, 0.30415322190639, -0.494819763939905, 1.07551674933261, 7.33888415457688E-02, 1.40170545411085E-02, -0.106110975998808, 1.68324361811875E-02, 1.25028363714877, 1013.16840309509, -1.51791558000712, 52.4277865990866, 23049.5545563912, 2.49459806365456E-02, 2107964.67412137, 366836848.613065, -144814105.365163, -1.7927637300359E-03, 4899556021.00459, 471.262212070518, -82929439019.8652, -1715.45662263191, 3557776.82973575, 586062760258.436, -12988763.5078195, 31724744937.1057)
  If (s > 5.210887825 And s < 9.15546555571324) Then
    sigma = s / 9.2
    eta = h / 2800
    teta = 0
    For i = 0 To 35
      teta = teta + ni(i) * (eta - 0.119) ^ Ii(i) * (sigma - 1.07) ^ Ji(i)
    Next i
    T4_hs = teta * 550
Else
    'Function psat_h
    If s > -0.0001545495919 And s <= 3.77828134 Then
      Low_Bound = 0.000611
      High_Bound = 165.291642526045
      Do While Abs(hL - h) > 0.00001 And Abs(High_Bound - Low_Bound) > 0.0001
       PL = (Low_Bound + High_Bound) / 2
       Ts = T4_p(PL)
       hL = h1_pT(PL, Ts)
       If hL > h Then
         High_Bound = PL
       Else
         Low_Bound = PL
       End If
      Loop
    ElseIf s > 3.77828134 And s <= 4.41202148223476 Then
      PL = p3sat_h(h)
    ElseIf s > 4.41202148223476 And s <= 5.210887663 Then
      PL = p3sat_h(h)
    End If
    Low_Bound = 0.000611
    High_Bound = PL
    Do While Abs(s - ss) > 0.000001 And Abs(High_Bound - Low_Bound) > 0.0000001
      p = (Low_Bound + High_Bound) / 2

      'Calculate s4_ph
      Ts = T4_p(p)
      xs = x4_ph(p, h)
      If p < 16.529 Then
        s4V = s2_pT(p, Ts)
        s4L = s1_pT(p, Ts)
      Else
        v4V = v3_ph(p, h4V_p(p))
        s4V = s3_rhoT(1 / v4V, Ts)
        v4L = v3_ph(p, h4L_p(p))
        s4L = s3_rhoT(1 / v4L, Ts)
      End If
      ss = (xs * s4V + (1 - xs) * s4L)

      If ss < s Then
        High_Bound = p
      Else
        Low_Bound = p
      End If
    Loop
    T4_hs = T4_p(p)
End If
End Function
'***********************************************************************************************************
'*2.5 Functions for region 5
Function h5_pT(ByVal p As Double, ByVal t As Double) As Double
  'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
  'Basic Equation for Region 5
  'Eq 32,33, Page 36, Tables 37-41
   Dim Iir, Jir, nir, ni0, Ji0 As Variant, tau, gamma0_tau, gammar_tau As Double, i As Integer
   Const R As Double = 0.461526   'kJ/(kg K)
  Ji0 = Array(0, 1, -3, -2, -1, 2)
  ni0 = Array(-13.179983674201, 6.8540841634434, -0.024805148933466, 0.36901534980333, -3.1161318213925, -0.32961626538917)
  Iir = Array(1, 1, 1, 2, 3)
  Jir = Array(0, 1, 3, 9, 3)
  nir = Array(-1.2563183589592E-04, 2.1774678714571E-03, -0.004594282089991, -3.9724828359569E-06, 1.2919228289784E-07)
  tau = 1000 / t
  gamma0_tau = 0
  For i = 0 To 5
    gamma0_tau = gamma0_tau + ni0(i) * Ji0(i) * tau ^ (Ji0(i) - 1)
  Next i
  gammar_tau = 0
  For i = 0 To 4
    gammar_tau = gammar_tau + nir(i) * p ^ Iir(i) * Jir(i) * tau ^ (Jir(i) - 1)
  Next i
  h5_pT = R * t * tau * (gamma0_tau + gammar_tau)
End Function


Function v5_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'Basic Equation for Region 5
'Eq 32,33, Page 36, Tables 37-41
Dim Iir, Jir, nir, ni0, Ji0 As Variant, tau, gamma0_pi, gammar_pi As Double, i As Integer
Const R As Double = 0.461526   'kJ/(kg K)
Ji0 = Array(0, 1, -3, -2, -1, 2)
ni0 = Array(-13.179983674201, 6.8540841634434, -0.024805148933466, 0.36901534980333, -3.1161318213925, -0.32961626538917)
Iir = Array(1, 1, 1, 2, 3)
Jir = Array(0, 1, 3, 9, 3)
nir = Array(-1.2563183589592E-04, 2.1774678714571E-03, -0.004594282089991, -3.9724828359569E-06, 1.2919228289784E-07)
tau = 1000 / t
gamma0_pi = 1 / p
gammar_pi = 0
For i = 0 To 4
  gammar_pi = gammar_pi + nir(i) * Iir(i) * p ^ (Iir(i) - 1) * tau ^ Jir(i)
Next i
v5_pT = R * t / p * p * (gamma0_pi + gammar_pi) / 1000
End Function

Function u5_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'Basic Equation for Region 5
'Eq 32,33, Page 36, Tables 37-41
Dim Iir, Jir, nir, ni0, Ji0 As Variant, tau, gamma0_pi, gammar_pi, gamma0_tau, gammar_tau As Double, i As Integer
Const R As Double = 0.461526   'kJ/(kg K)
Ji0 = Array(0, 1, -3, -2, -1, 2)
ni0 = Array(-13.179983674201, 6.8540841634434, -0.024805148933466, 0.36901534980333, -3.1161318213925, -0.32961626538917)
Iir = Array(1, 1, 1, 2, 3)
Jir = Array(0, 1, 3, 9, 3)
nir = Array(-1.2563183589592E-04, 2.1774678714571E-03, -0.004594282089991, -3.9724828359569E-06, 1.2919228289784E-07)
tau = 1000 / t
gamma0_pi = 1 / p
gamma0_tau = 0
For i = 0 To 5
  gamma0_tau = gamma0_tau + ni0(i) * Ji0(i) * tau ^ (Ji0(i) - 1)
Next i
gammar_pi = 0
gammar_tau = 0
For i = 0 To 4
  gammar_pi = gammar_pi + nir(i) * Iir(i) * p ^ (Iir(i) - 1) * tau ^ Jir(i)
  gammar_tau = gammar_tau + nir(i) * p ^ Iir(i) * Jir(i) * tau ^ (Jir(i) - 1)
Next i
u5_pT = R * t * (tau * (gamma0_tau + gammar_tau) - p * (gamma0_pi + gammar_pi))
End Function
Function Cp5_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'Basic Equation for Region 5
'Eq 32,33, Page 36, Tables 37-41
Dim Iir, Jir, nir, ni0, Ji0 As Variant, tau, gamma0_tautau, gammar_tautau As Double, i As Integer
Const R As Double = 0.461526   'kJ/(kg K)
Ji0 = Array(0, 1, -3, -2, -1, 2)
ni0 = Array(-13.179983674201, 6.8540841634434, -0.024805148933466, 0.36901534980333, -3.1161318213925, -0.32961626538917)
Iir = Array(1, 1, 1, 2, 3)
Jir = Array(0, 1, 3, 9, 3)
nir = Array(-1.2563183589592E-04, 2.1774678714571E-03, -0.004594282089991, -3.9724828359569E-06, 1.2919228289784E-07)
tau = 1000 / t
gamma0_tautau = 0
For i = 0 To 5
  gamma0_tautau = gamma0_tautau + ni0(i) * Ji0(i) * (Ji0(i) - 1) * tau ^ (Ji0(i) - 2)
Next i
gammar_tautau = 0
For i = 0 To 4
  gammar_tautau = gammar_tautau + nir(i) * p ^ Iir(i) * Jir(i) * (Jir(i) - 1) * tau ^ (Jir(i) - 2)
Next i
Cp5_pT = -R * tau ^ 2 * (gamma0_tautau + gammar_tautau)
End Function

Function s5_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'Basic Equation for Region 5
'Eq 32,33, Page 36, Tables 37-41
Dim Iir, Jir, nir, ni0, Ji0 As Variant, tau, gamma0, gamma0_tau, gammar, gammar_tau As Double, i As Integer
Const R As Double = 0.461526   'kJ/(kg K)
Ji0 = Array(0, 1, -3, -2, -1, 2)
ni0 = Array(-13.179983674201, 6.8540841634434, -0.024805148933466, 0.36901534980333, -3.1161318213925, -0.32961626538917)
Iir = Array(1, 1, 1, 2, 3)
Jir = Array(0, 1, 3, 9, 3)
nir = Array(-1.2563183589592E-04, 2.1774678714571E-03, -0.004594282089991, -3.9724828359569E-06, 1.2919228289784E-07)
tau = 1000 / t
gamma0 = Log(p)
gamma0_tau = 0
For i = 0 To 5
  gamma0_tau = gamma0_tau + ni0(i) * Ji0(i) * tau ^ (Ji0(i) - 1)
  gamma0 = gamma0 + ni0(i) * tau ^ Ji0(i)
Next i
gammar = 0
gammar_tau = 0
For i = 0 To 4
  gammar = gammar + nir(i) * p ^ Iir(i) * tau ^ Jir(i)
  gammar_tau = gammar_tau + nir(i) * p ^ Iir(i) * Jir(i) * tau ^ (Jir(i) - 1)
Next i
s5_pT = R * (tau * (gamma0_tau + gammar_tau) - (gamma0 + gammar))
End Function
Function Cv5_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'Basic Equation for Region 5
'Eq 32,33, Page 36, Tables 37-41
Dim Iir, Jir, nir, ni0, Ji0 As Variant, tau, gamma0_tautau, gammar_pi, gammar_pitau, gammar_pipi, gammar_tautau As Double, i As Integer
Const R As Double = 0.461526   'kJ/(kg K)
Ji0 = Array(0, 1, -3, -2, -1, 2)
ni0 = Array(-13.179983674201, 6.8540841634434, -0.024805148933466, 0.36901534980333, -3.1161318213925, -0.32961626538917)
Iir = Array(1, 1, 1, 2, 3)
Jir = Array(0, 1, 3, 9, 3)
nir = Array(-1.2563183589592E-04, 2.1774678714571E-03, -0.004594282089991, -3.9724828359569E-06, 1.2919228289784E-07)
tau = 1000 / t
gamma0_tautau = 0
For i = 0 To 5
  gamma0_tautau = gamma0_tautau + ni0(i) * (Ji0(i) - 1) * Ji0(i) * tau ^ (Ji0(i) - 2)
Next i
gammar_pi = 0
gammar_pitau = 0
gammar_pipi = 0
gammar_tautau = 0
For i = 0 To 4
  gammar_pi = gammar_pi + nir(i) * Iir(i) * p ^ (Iir(i) - 1) * tau ^ Jir(i)
  gammar_pitau = gammar_pitau + nir(i) * Iir(i) * p ^ (Iir(i) - 1) * Jir(i) * tau ^ (Jir(i) - 1)
  gammar_pipi = gammar_pipi + nir(i) * Iir(i) * (Iir(i) - 1) * p ^ (Iir(i) - 2) * tau ^ Jir(i)
  gammar_tautau = gammar_tautau + nir(i) * p ^ Iir(i) * Jir(i) * (Jir(i) - 1) * tau ^ (Jir(i) - 2)
Next i
Cv5_pT = R * (-(tau ^ 2 * (gamma0_tautau + gammar_tautau)) - (1 + p * gammar_pi - tau * p * gammar_pitau) ^ 2 / (1 - p ^ 2 * gammar_pipi))

End Function
Function w5_pT(ByVal p As Double, ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam, September 1997
'Basic Equation for Region 5
'Eq 32,33, Page 36, Tables 37-41
Dim Iir, Jir, nir, ni0, Ji0 As Variant, tau, gamma0_tautau, gammar_pi, gammar_pitau, gammar_pipi, gammar_tautau As Double, i As Integer
Const R As Double = 0.461526   'kJ/(kg K)
Ji0 = Array(0, 1, -3, -2, -1, 2)
ni0 = Array(-13.179983674201, 6.8540841634434, -0.024805148933466, 0.36901534980333, -3.1161318213925, -0.32961626538917)
Iir = Array(1, 1, 1, 2, 3)
Jir = Array(0, 1, 3, 9, 3)
nir = Array(-1.2563183589592E-04, 2.1774678714571E-03, -0.004594282089991, -3.9724828359569E-06, 1.2919228289784E-07)
tau = 1000 / t
gamma0_tautau = 0
For i = 0 To 5
  gamma0_tautau = gamma0_tautau + ni0(i) * (Ji0(i) - 1) * Ji0(i) * tau ^ (Ji0(i) - 2)
Next i
gammar_pi = 0
gammar_pitau = 0
gammar_pipi = 0
gammar_tautau = 0
For i = 0 To 4
  gammar_pi = gammar_pi + nir(i) * Iir(i) * p ^ (Iir(i) - 1) * tau ^ Jir(i)
  gammar_pitau = gammar_pitau + nir(i) * Iir(i) * p ^ (Iir(i) - 1) * Jir(i) * tau ^ (Jir(i) - 1)
  gammar_pipi = gammar_pipi + nir(i) * Iir(i) * (Iir(i) - 1) * p ^ (Iir(i) - 2) * tau ^ Jir(i)
  gammar_tautau = gammar_tautau + nir(i) * p ^ Iir(i) * Jir(i) * (Jir(i) - 1) * tau ^ (Jir(i) - 2)
Next i
w5_pT = (1000 * R * t * (1 + 2 * p * gammar_pi + p ^ 2 * gammar_pi ^ 2) / ((1 - p ^ 2 * gammar_pipi) + (1 + p * gammar_pi - tau * p * gammar_pitau) ^ 2 / (tau ^ 2 * (gamma0_tautau + gammar_tautau)))) ^ 0.5
End Function

Function T5_ph(ByVal p As Double, ByVal h As Double) As Double
    'Solve with half interval method
    Dim Low_Bound, High_Bound, Ts, hs As Double
    Low_Bound = 1073.15
    High_Bound = 2273.15
    Do While Abs(h - hs) > 0.00001
      Ts = (Low_Bound + High_Bound) / 2
      hs = h5_pT(p, Ts)
      If hs > h Then
        High_Bound = Ts
      Else
        Low_Bound = Ts
      End If
    Loop
    T5_ph = Ts
End Function

Function T5_ps(ByVal p As Double, ByVal s As Double) As Double
    'Solve with half interval method
    Dim Low_Bound, High_Bound, Ts, ss As Double
    Low_Bound = 1073.15
    High_Bound = 2273.15
    Do While Abs(s - ss) > 0.00001
      Ts = (Low_Bound + High_Bound) / 2
      ss = s5_pT(p, Ts)
      If ss > s Then
        High_Bound = Ts
      Else
        Low_Bound = Ts
      End If
    Loop
    T5_ps = Ts
End Function
Function T5_prho(ByVal p As Double, ByVal rho As Double) As Double
  'Solve by iteration. Observe that fo low temperatures this equation has 2 solutions.
  'Solve with half interval method
  Dim Low_Bound, High_Bound, Ts, rhos As Double
    Low_Bound = 1073.15
    High_Bound = 2073.15
  Do While Abs(rho - rhos) > 0.000001
    Ts = (Low_Bound + High_Bound) / 2
    rhos = 1 / v2_pT(p, Ts)
    If rhos < rho Then
      High_Bound = Ts
    Else
      Low_Bound = Ts
    End If
    Loop
    T5_prho = Ts
End Function
'***********************************************************************************************************
'*3 Region Selection
'***********************************************************************************************************
'*3.1 Regions as a function of pT
Function region_pT(ByVal p As Double, ByVal t As Double) As Integer
Dim ps As Double
If t > 1073.15 And p < 10 And t < 2273.15 And p > 0.000611 Then
  region_pT = 5
ElseIf t <= 1073.15 And t > 273.15 And p <= 100 And p > 0.000611 Then
  If t > 623.15 Then
    If p > B23p_T(t) Then
     region_pT = 3
     If t < 647.096 Then
        ps = p4_T(t)
        If Abs(p - ps) < 0.00001 Then
           region_pT = 4
        End If
     End If
    Else
     region_pT = 2
    End If
   Else
    ps = p4_T(t)
    If Abs(p - ps) < 0.00001 Then
      region_pT = 4
    ElseIf p > ps Then
      region_pT = 1
    Else
      region_pT = 2
    End If
   End If
  Else
    region_pT = 0 '**Error, Outside valid area
  End If
End Function
'***********************************************************************************************************
'*3.2 Regions as a function of ph
Function region_ph(ByVal p, ByVal h) As Integer
Dim hL, hV, h_45, h_5u, Ts As Double
 'Check if outside pressure limits
 If p < 0.000611657 Or p > 100 Then
     region_ph = 0
     Exit Function
 End If

 'Check if outside low h.
 If h < 0.963 * p + 2.2 Then 'Linear adaption to h1_pt()+2 to speed up calcualations.
    If h < h1_pT(p, 273.15) Then
      region_ph = 0
      Exit Function
    End If
 End If

 If p < 16.5292 Then 'Bellow region 3,Check  region 1,4,2,5
   'Check Region 1
   Ts = T4_p(p)
   hL = 109.6635 * Log(p) + 40.3481 * p + 734.58 'Approximate function for hL_p
   If Abs(h - hL) < 100 Then 'If approximate is not god enough use real function
      hL = h1_pT(p, Ts)
   End If
   If h <= hL Then
     region_ph = 1
     Exit Function
   End If
   'Check Region 4
   hV = 45.1768 * Log(p) - 20.158 * p + 2804.4 'Approximate function for hV_p
   If Abs(h - hV) < 50 Then 'If approximate is not god enough use real function
      hV = h2_pT(p, Ts)
   End If
   If h < hV Then
     region_ph = 4
     Exit Function
   End If
   'Check upper limit of region 2 Quick Test
   If h < 4000 Then
     region_ph = 2
     Exit Function
   End If
  'Check region 2 (Real value)
   h_45 = h2_pT(p, 1073.15)
   If h <= h_45 Then
     region_ph = 2
     Exit Function
   End If
  'Check region 5
   If p > 10 Then
     region_ph = 0
     Exit Function
   End If
   h_5u = h5_pT(p, 2273.15)
   If h < h_5u Then
      region_ph = 5
      Exit Function
   End If
   region_ph = 0
   Exit Function
  Else 'For p>16.5292
   'Check if in region1
   If h < h1_pT(p, 623.15) Then
     region_ph = 1
     Exit Function
   End If
   'Check if in region 3 or 4 (Bellow Reg 2)
   If h < h2_pT(p, B23T_p(p)) Then
     'Region 3 or 4
     If p > p3sat_h(h) Then
       region_ph = 3
       Exit Function
     Else
       region_ph = 4
       Exit Function
     End If
  End If
  'Check if region 2
  If h < h2_pT(p, 1073.15) Then
    region_ph = 2
    Exit Function
  End If
 End If
 region_ph = 0
End Function
'***********************************************************************************************************
'*3.3 Regions as a function of ps
Function region_ps(ByVal p As Double, ByVal s) As Integer
Dim ss As Double
  If p < 0.000611657 Or p > 100 Or s < 0 Or s > s5_pT(p, 2273.15) Then
   region_ps = 0
   Exit Function
  End If

  'Check region 5
  If s > s2_pT(p, 1073.15) Then
    If p <= 10 Then
      region_ps = 5
      Exit Function
    Else
      region_ps = 0
      Exit Function
    End If
  End If

  'Check region 2
  If p > 16.529 Then
    ss = s2_pT(p, B23T_p(p)) 'Between 5.047 and 5.261. Use to speed up!
  Else
    ss = s2_pT(p, T4_p(p))
  End If
  If s > ss Then
      region_ps = 2
      Exit Function
  End If

  'Check region 3
  ss = s1_pT(p, 623.15)
  If p > 16.529 And s > ss Then
    If p > p3sat_s(s) Then
      region_ps = 3
      Exit Function
    Else
      region_ps = 4
      Exit Function
    End If
  End If

  'Check region 4 (Not inside region 3)
  If p < 16.529 And s > s1_pT(p, T4_p(p)) Then
    region_ps = 4
    Exit Function
  End If

  'Check region 1
  If p > 0.000611657 And s > s1_pT(p, 273.15) Then
    region_ps = 1
    Exit Function
  End If
  region_ps = 1
End Function
'***********************************************************************************************************
'*3.4 Regions as a function of hs
Function Region_hs(ByVal h, ByVal s) As Integer
Dim TMax, hMax, hB, hL, hV, vmax, Tmin, hMin As Double
  If s < -0.0001545495919 Then
    Region_hs = 0
    Exit Function
  End If
  'Check linear adaption to p=0.000611. If bellow region 4.
  hMin = (((-0.0415878 - 2500.89262) / (-0.00015455 - 9.155759)) * s)
  If s < 9.155759395 And h < hMin Then
    Region_hs = 0
    Exit Function
  End If

  '******Kolla 1 eller 4. (+liten bit över B13)
  If s >= -0.0001545495919 And s <= 3.77828134 Then
    If h < h4_s(s) Then
      Region_hs = 4
      Exit Function
    ElseIf s < 3.397782955 Then '100MPa line is limiting
      TMax = T1_ps(100, s)
      hMax = h1_pT(100, TMax)
      If h < hMax Then
       Region_hs = 1
       Exit Function
      Else
       Region_hs = 0
       Exit Function
      End If
     Else 'The point is either in region 4,1,3. Check B23
      hB = hB13_s(s)
      If h < hB Then
        Region_hs = 1
        Exit Function
      End If
      TMax = T3_ps(100, s)
      vmax = v3_ps(100, s)
      hMax = h3_rhoT(1 / vmax, TMax)
      If h < hMax Then
        Region_hs = 3
        Exit Function
      Else
        Region_hs = 0
        Exit Function
      End If
     End If
  End If

  '******Kolla region 2 eller 4. (Övre delen av omrĺde b23-> max)
  If s >= 5.260578707 And s <= 11.9212156897728 Then
    If s > 9.155759395 Then 'Above region 4
      Tmin = T2_ps(0.000611, s)
      hMin = h2_pT(0.000611, Tmin)
      'Function adapted to h(1073.15,s)
      hMax = -0.07554022 * s ^ 4 + 3.341571 * s ^ 3 - 55.42151 * s ^ 2 + 408.515 * s + 3031.338
      If h > hMin And h < hMax Then
        Region_hs = 2
        Exit Function
      Else
        Region_hs = 0
        Exit Function
      End If
    End If


      hV = h4_s(s)

    If h < hV Then  'Region 4. Under region 3.
        Region_hs = 4
        Exit Function
    End If
    If s < 6.04048367171238 Then
      TMax = T2_ps(100, s)
      hMax = h2_pT(100, TMax)
    Else
     'Function adapted to h(1073.15,s)
      hMax = -2.988734 * s ^ 4 + 121.4015 * s ^ 3 - 1805.15 * s ^ 2 + 11720.16 * s - 23998.33
    End If
     If h < hMax Then  'Region 2. Över region 4.
        Region_hs = 2
        Exit Function
    Else
        Region_hs = 0
        Exit Function
    End If
   End If

   'Kolla region 3 eller 4. Under kritiska punkten.
   If s >= 3.77828134 And s <= 4.41202148223476 Then
     hL = h4_s(s)
     If h < hL Then
       Region_hs = 4
       Exit Function
     End If
     TMax = T3_ps(100, s)
     vmax = v3_ps(100, s)
     hMax = h3_rhoT(1 / vmax, TMax)
     If h < hMax Then
        Region_hs = 3
        Exit Function
     Else
        Region_hs = 0
        Exit Function
    End If
   End If

   'Kolla region 3 eller 4 frĺn kritiska punkten till övre delen av b23
   If s >= 4.41202148223476 And s <= 5.260578707 Then
     hV = h4_s(s)
     If h < hV Then
        Region_hs = 4
        Exit Function
     End If
     'Kolla om vi är under b23 giltighetsomrĺde.
     If s <= 5.048096828 Then
       TMax = T3_ps(100, s)
       vmax = v3_ps(100, s)
       hMax = h3_rhoT(1 / vmax, TMax)
       If h < hMax Then
         Region_hs = 3
         Exit Function
       Else
         Region_hs = 0
         Exit Function
       End If
     Else 'Inom omrĺdet för B23 i s led.
       If (h > 2812.942061) Then 'Ovanför B23 i h_led
         If s > 5.09796573397125 Then
           TMax = T2_ps(100, s)
           hMax = h2_pT(100, TMax)
           If h < hMax Then
             Region_hs = 2
             Exit Function
           Else
             Region_hs = 0
             Exit Function
           End If
         Else
           Region_hs = 0
           Exit Function
         End If
       End If
       If (h < 2563.592004) Then   'Nedanför B23 i h_led men vi har redan kollat ovanför hV2c3b
          Region_hs = 3
          Exit Function
       End If
       'Vi är inom b23 omrĺdet i bĺde s och h led.
       If p2_hs(h, s) > B23p_T(TB23_hs(h, s)) Then
         Region_hs = 3
         Exit Function
       Else
         Region_hs = 2
         Exit Function
       End If
     End If
   End If
   Region_hs = CVErr(xlErrValue)
End Function
'***********************************************************************************************************
'*3.5 Regions as a function of p and rho
Function Region_prho(ByVal p As Double, ByVal rho) As Integer
  Dim v As Double
  v = 1 / rho
  If p < 0.000611657 Or p > 100 Then
    Region_prho = 0
    Exit Function
  End If
  If p < 16.5292 Then 'Bellow region 3, Check region 1,4,2
    If v < v1_pT(p, 273.15) Then 'Observe that this is not actually min of v. Not valid Water of 4°C is ligther.
      Region_prho = 0
      Exit Function
    End If
    If v <= v1_pT(p, T4_p(p)) Then
      Region_prho = 1
      Exit Function
    End If
    If v < v2_pT(p, T4_p(p)) Then
      Region_prho = 4
      Exit Function
    End If
    If v <= v2_pT(p, 1073.15) Then
      Region_prho = 2
      Exit Function
    End If
    If p > 10 Then 'Above region 5
      Region_prho = 0
      Exit Function
    End If
    If v <= v5_pT(p, 2073.15) Then
      Region_prho = 5
      Exit Function
    End If
  Else 'Check region 1,3,4,3,2 (Above the lowest point of region 3.)
    If v < v1_pT(p, 273.15) Then 'Observe that this is not actually min of v. Not valid Water of 4°C is ligther.
      Region_prho = 0
      Exit Function
    End If
    If v < v1_pT(p, 623.15) Then
      Region_prho = 1
      Exit Function
    End If
    'Check if in region 3 or 4 (Bellow Reg 2)
    If v < v2_pT(p, B23T_p(p)) Then
     'Region 3 or 4
      If p > 22.064 Then 'Above region 4
        Region_prho = 3
        Exit Function
      End If
      If v < v3_ph(p, h4L_p(p)) Or v > v3_ph(p, h4V_p(p)) Then 'Uses iteration!!
        Region_prho = 3
        Exit Function
      Else
        Region_prho = 4
        Exit Function
      End If
    End If
    'Check if region 2
    If v < v2_pT(p, 1073.15) Then
      Region_prho = 2
      Exit Function
    End If
  End If

  Region_prho = 0
End Function


'***********************************************************************************************************
'*4 Region Borders
'***********************************************************************************************************
'***********************************************************************************************************
'*4.1 Boundary between region 2 and 3.
Function B23p_T(ByVal t As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
'1997
'Section 4 Auxiliary Equation for the Boundary between Regions 2 and 3
'Eq 5, Page 5
B23p_T = 348.05185628969 - 1.1671859879975 * t + 1.0192970039326E-03 * t ^ 2
End Function
Function B23T_p(ByVal p As Double) As Double
'Release on the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
'1997
'Section 4 Auxiliary Equation for the Boundary between Regions 2 and 3
'Eq 6, Page 6
B23T_p = 572.54459862746 + ((p - 13.91883977887) / 1.0192970039326E-03) ^ 0.5
End Function
'***********************************************************************************************************
'*4.2 Region 3. pSat_h and pSat_s
Function p3sat_h(ByVal h As Double) As Double
'Revised Supplementary Release on Backward Equations for the Functions T(p,h), v(p,h) and T(p,s), v(p,s) for Region 3 of the IAPWS Industrial Formulation 1997 for the Thermodynamic Properties of Water and Steam
'2004
'Section 4 Boundary Equations psat(h) and psat(s) for the Saturation Lines of Region 3
'Se pictures Page 17, Eq 10, Table 17, Page 18
Dim Ii, Ji, ni As Variant, ps As Double, i As Integer
Ii = Array(0, 1, 1, 1, 1, 5, 7, 8, 14, 20, 22, 24, 28, 36)
Ji = Array(0, 1, 3, 4, 36, 3, 0, 24, 16, 16, 3, 18, 8, 24)
ni = Array(0.600073641753024, -9.36203654849857, 24.6590798594147, -107.014222858224, -91582131580576.8, -8623.32011700662, -23.5837344740032, 2.52304969384128E+17, -3.89718771997719E+18, -3.33775713645296E+22, 35649946963.6328, -1.48547544720641E+26, 3.30611514838798E+18, 8.13641294467829E+37)
h = h / 2600
ps = 0
For i = 0 To 13
  ps = ps + ni(i) * (h - 1.02) ^ Ii(i) * (h - 0.608) ^ Ji(i)
Next i
p3sat_h = ps * 22
End Function
Function p3sat_s(ByVal s As Double) As Double
Dim Ii, Ji, ni As Variant, sigma, p As Double, i As Integer
Ii = Array(0, 1, 1, 4, 12, 12, 16, 24, 28, 32)
Ji = Array(0, 1, 32, 7, 4, 14, 36, 10, 0, 18)
ni = Array(0.639767553612785, -12.9727445396014, -2.24595125848403E+15, 1774667.41801846, 7170793495.71538, -3.78829107169011E+17, -9.55586736431328E+34, 1.87269814676188E+23, 119254746466.473, 1.10649277244882E+36)
sigma = s / 5.2
p = 0
For i = 0 To 9
  p = p + ni(i) * (sigma - 1.03) ^ Ii(i) * (sigma - 0.699) ^ Ji(i)
Next i
p3sat_s = p * 22
End Function
'***********************************************************************************************************
'4.3 Region boundary 1to3 and 3to2 as a functions of s
Function hB13_s(ByVal s As Double) As Double
'Supplementary Release on Backward Equations ( ) , p h s for Region 3,
'Chapter 4.5 page 23.
Dim Ii, Ji, ni As Variant, sigma, eta As Double, i As Integer
  Ii = Array(0, 1, 1, 3, 5, 6)
  Ji = Array(0, -2, 2, -12, -4, -3)
  ni = Array(0.913965547600543, -4.30944856041991E-05, 60.3235694765419, 1.17518273082168E-18, 0.220000904781292, -69.0815545851641)
  sigma = s / 3.8
  eta = 0
  For i = 0 To 5
    eta = eta + ni(i) * (sigma - 0.884) ^ Ii(i) * (sigma - 0.864) ^ Ji(i)
  Next i
  hB13_s = eta * 1700
End Function
Function TB23_hs(ByVal h As Double, ByVal s As Double) As Double
'Supplementary Release on Backward Equations ( ) , p h s for Region 3,
'Chapter 4.6 page 25.
Dim Ii, Ji, ni As Variant, sigma, eta, teta As Double, i As Integer
   Ii = Array(-12, -10, -8, -4, -3, -2, -2, -2, -2, 0, 1, 1, 1, 3, 3, 5, 6, 6, 8, 8, 8, 12, 12, 14, 14)
   Ji = Array(10, 8, 3, 4, 3, -6, 2, 3, 4, 0, -3, -2, 10, -2, -1, -5, -6, -3, -8, -2, -1, -12, -1, -12, 1)
   ni = Array(6.2909626082981E-04, -8.23453502583165E-04, 5.15446951519474E-08, -1.17565945784945, 3.48519684726192, -5.07837382408313E-12, -2.84637670005479, -2.36092263939673, 6.01492324973779, 1.48039650824546, 3.60075182221907E-04, -1.26700045009952E-02, -1221843.32521413, 0.149276502463272, 0.698733471798484, -2.52207040114321E-02, 1.47151930985213E-02, -1.08618917681849, -9.36875039816322E-04, 81.9877897570217, -182.041861521835, 2.61907376402688E-06, -29162.6417025961, 1.40660774926165E-05, 7832370.62349385)
  sigma = s / 5.3
  eta = h / 3000
  teta = 0
  For i = 0 To 24
    teta = teta + ni(i) * (eta - 0.727) ^ Ii(i) * (sigma - 0.864) ^ Ji(i)
  Next i
  TB23_hs = teta * 900
End Function

'***********************************************************************************************************
'*5 Transport properties
'***********************************************************************************************************
'*5.1 Viscosity (IAPWS formulation 1985, Revised 2003)
'***********************************************************************************************************
Function my_AllRegions_pT(ByVal p As Double, ByVal t As Double) As Double
Dim h0, h1, h2, h3, h4, h5, h6 As Variant, rho, Ts, ps, my0, sum, my1, rhos As Double, i As Integer
  h0 = Array(0.5132047, 0.3205656, 0, 0, -0.7782567, 0.1885447)
  h1 = Array(0.2151778, 0.7317883, 1.241044, 1.476783, 0, 0)
  h2 = Array(-0.2818107, -1.070786, -1.263184, 0, 0, 0)
  h3 = Array(0.1778064, 0.460504, 0.2340379, -0.4924179, 0, 0)
  h4 = Array(-0.0417661, 0, 0, 0.1600435, 0, 0)
  h5 = Array(0, -0.01578386, 0, 0, 0, 0)
  h6 = Array(0, 0, 0, -0.003629481, 0, 0)

  'Calcualte density.
 Select Case region_pT(p, t)
 Case 1
   rho = 1 / v1_pT(p, t)
 Case 2
   rho = 1 / v2_pT(p, t)
 Case 3
   rho = 1 / v3_ph(p, h3_pT(p, t))
 Case 4
   rho = CVErr(xlErrValue)
 Case 5
   rho = 1 / v5_pT(p, t)
 Case Else
  my_AllRegions_pT = CVErr(xlErrValue)
  Exit Function
 End Select

  rhos = rho / 317.763
  Ts = t / 647.226
  ps = p / 22.115

  'Check valid area
  If t > 900 + 273.15 Or (t > 600 + 273.15 And p > 300) Or (t > 150 + 273.15 And p > 350) Or p > 500 Then
    my_AllRegions_pT = CVErr(xlErrValue)
    Exit Function
  End If
  my0 = Ts ^ 0.5 / (1 + 0.978197 / Ts + 0.579829 / (Ts ^ 2) - 0.202354 / (Ts ^ 3))
  sum = 0
  For i = 0 To 5
      sum = sum + h0(i) * (1 / Ts - 1) ^ i + h1(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 1 + h2(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 2 + h3(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 3 + h4(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 4 + h5(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 5 + h6(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 6
  Next i
  my1 = Exp(rhos * sum)
  my_AllRegions_pT = my0 * my1 * 0.000055071
End Function

Function my_AllRegions_ph(ByVal p As Double, ByVal h As Double) As Double
  Dim h0, h1, h2, h3, h4, h5, h6 As Variant, rho, t, Ts, ps, my0, sum, my1, rhos, v4V, v4L, xs As Double, i As Integer
  h0 = Array(0.5132047, 0.3205656, 0, 0, -0.7782567, 0.1885447)
  h1 = Array(0.2151778, 0.7317883, 1.241044, 1.476783, 0, 0)
  h2 = Array(-0.2818107, -1.070786, -1.263184, 0, 0, 0)
  h3 = Array(0.1778064, 0.460504, 0.2340379, -0.4924179, 0, 0)
  h4 = Array(-0.0417661, 0, 0, 0.1600435, 0, 0)
  h5 = Array(0, -0.01578386, 0, 0, 0, 0)
  h6 = Array(0, 0, 0, -0.003629481, 0, 0)

  'Calcualte density.
 Select Case region_ph(p, h)
 Case 1
   Ts = T1_ph(p, h)
   t = Ts
   rho = 1 / v1_pT(p, Ts)
 Case 2
   Ts = T2_ph(p, h)
   t = Ts
   rho = 1 / v2_pT(p, Ts)
 Case 3
   rho = 1 / v3_ph(p, h)
   t = T3_ph(p, h)
 Case 4
   xs = x4_ph(p, h)
   If p < 16.529 Then
     v4V = v2_pT(p, T4_p(p))
     v4L = v1_pT(p, T4_p(p))
   Else
     v4V = v3_ph(p, h4V_p(p))
     v4L = v3_ph(p, h4L_p(p))
    End If
    rho = 1 / (xs * v4V + (1 - xs) * v4L)
    t = T4_p(p)
 Case 5
   Ts = T5_ph(p, h)
   t = Ts
   rho = 1 / v5_pT(p, Ts)
 Case Else
  my_AllRegions_ph = CVErr(xlErrValue)
  Exit Function
 End Select
  rhos = rho / 317.763
  Ts = t / 647.226
  ps = p / 22.115
  'Check valid area
  If t > 900 + 273.15 Or (t > 600 + 273.15 And p > 300) Or (t > 150 + 273.15 And p > 350) Or p > 500 Then
    my_AllRegions_ph = CVErr(xlErrValue)
    Exit Function
  End If
  my0 = Ts ^ 0.5 / (1 + 0.978197 / Ts + 0.579829 / (Ts ^ 2) - 0.202354 / (Ts ^ 3))

  sum = 0
  For i = 0 To 5
      sum = sum + h0(i) * (1 / Ts - 1) ^ i + h1(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 1 + h2(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 2 + h3(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 3 + h4(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 4 + h5(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 5 + h6(i) * (1 / Ts - 1) ^ i * (rhos - 1) ^ 6
  Next i
  my1 = Exp(rhos * sum)
  my_AllRegions_ph = my0 * my1 * 0.000055071
End Function
'***********************************************************************************************************
'*5.2 Thermal Conductivity (IAPWS formulation 1985)
Function tc_ptrho(ByVal p As Double, ByVal t As Double, ByVal rho As Double) As Double
'Revised release on the IAPS Formulation 1985 for the Thermal Conductivity of ordinary water
'IAPWS September 1998
'Page 8
'ver2.6 Start corrected bug
 Dim tc0, tc1, dt, Q, s, tc2, tc As Double
 If t < 273.15 Then
   tc_ptrho = CVErr(xlErrValue) 'Out of range of validity (para. B4)
   Exit Function
 ElseIf t < 500 + 273.15 Then
   If p > 100 Then
     tc_ptrho = CVErr(xlErrValue) 'Out of range of validity (para. B4)
     Exit Function
   End If
 ElseIf t <= 650 + 273.15 Then
   If p > 70 Then
   tc_ptrho = CVErr(xlErrValue) 'Out of range of validity (para. B4)
   Exit Function
 End If
 ElseIf t <= 800 + 273.15 Then
   If p > 40 Then
      tc_ptrho = CVErr(xlErrValue) 'Out of range of validity (para. B4)
      Exit Function
   End If
 End If
 'ver2.6 End corrected bug

  t = t / 647.26
  rho = rho / 317.7
  tc0 = t ^ 0.5 * (0.0102811 + 0.0299621 * t + 0.0156146 * t ^ 2 - 0.00422464 * t ^ 3)
  tc1 = -0.39707 + 0.400302 * rho + 1.06 * Exp(-0.171587 * (rho + 2.39219) ^ 2)
  dt = Abs(t - 1) + 0.00308976
  Q = 2 + 0.0822994 / dt ^ (3 / 5)
  If t >= 1 Then
   s = 1 / dt
  Else
   s = 10.0932 / dt ^ (3 / 5)
  End If
  tc2 = (0.0701309 / t ^ 10 + 0.011852) * rho ^ (9 / 5) * Exp(0.642857 * (1 - rho ^ (14 / 5))) + 0.00169937 * s * rho ^ Q * Exp((Q / (1 + Q)) * (1 - rho ^ (1 + Q))) - 1.02 * Exp(-4.11717 * t ^ (3 / 2) - 6.17937 / rho ^ 5)
  tc_ptrho = tc0 + tc1 + tc2
End Function
'***********************************************************************************************************
'5.3 Surface Tension
Function Surface_Tension_T(ByVal t As Double)
'IAPWS Release on Surface Tension of Ordinary Water Substance,
'September 1994
Dim tau As Double
Const tc As Double = 647.096, b As Double = 0.2358, bb As Double = -0.625, my As Double = 1.256
If t < 0.01 Or t > tc Then
 Surface_Tension_T = "Out of valid region"
 Exit Function
End If
tau = 1 - t / tc
Surface_Tension_T = b * tau ^ my * (1 + bb * tau)
End Function
'***********************************************************************************************************
'*6 Units                                                                                      *
'***********************************************************************************************************

Function toSIunit_p(ByVal Ins As Double) As Double
'Translate bar to MPa
  toSIunit_p = Ins / 10
End Function
Function fromSIunit_p(ByVal Ins As Double) As Double
'Translate bar to MPa
  fromSIunit_p = Ins * 10
End Function
Function toSIunit_T(ByVal Ins As Double) As Double
'Translate degC to Kelvon
  toSIunit_T = Ins + 273.15
End Function
Function fromSIunit_T(ByVal Ins As Double) As Double
'Translate Kelvin to degC
  fromSIunit_T = Ins - 273.15
End Function
Function toSIunit_h(ByVal Ins As Double) As Double
  toSIunit_h = Ins
End Function
Function fromSIunit_h(ByVal Ins As Double) As Double
  fromSIunit_h = Ins
End Function
Function toSIunit_v(ByVal Ins As Double) As Double
  toSIunit_v = Ins
End Function
Function fromSIunit_v(ByVal Ins As Double) As Double
  fromSIunit_v = Ins
End Function
Function toSIunit_s(ByVal Ins As Double) As Double
  toSIunit_s = Ins
End Function
Function fromSIunit_s(ByVal Ins As Double) As Double
  fromSIunit_s = Ins
End Function
Function toSIunit_u(ByVal Ins As Double) As Double
  toSIunit_u = Ins
End Function
Function fromSIunit_u(ByVal Ins As Double) As Double
  fromSIunit_u = Ins
End Function
Function toSIunit_Cp(ByVal Ins As Double) As Double
  toSIunit_Cp = Ins
End Function
Function fromSIunit_Cp(ByVal Ins As Double) As Double
  fromSIunit_Cp = Ins
End Function
Function toSIunit_Cv(ByVal Ins As Double) As Double
  toSIunit_Cv = Ins
End Function
Function fromSIunit_Cv(ByVal Ins As Double) As Double
  fromSIunit_Cv = Ins
End Function
Function toSIunit_w(ByVal Ins As Double) As Double
  toSIunit_w = Ins
End Function
Function fromSIunit_w(ByVal Ins As Double) As Double
  fromSIunit_w = Ins
End Function
Function toSIunit_tc(ByVal Ins As Double) As Double
  toSIunit_tc = Ins
End Function
Function fromSIunit_tc(ByVal Ins As Double) As Double
  fromSIunit_tc = Ins
End Function
Function toSIunit_st(ByVal Ins As Double) As Double
  toSIunit_st = Ins
End Function
Function fromSIunit_st(ByVal Ins As Double) As Double
  fromSIunit_st = Ins
End Function
Function toSIunit_x(ByVal Ins As Double) As Double
  toSIunit_x = Ins
End Function
Function fromSIunit_x(ByVal Ins As Double) As Double
  fromSIunit_x = Ins
End Function
Function toSIunit_vx(ByVal Ins As Double) As Double
  toSIunit_vx = Ins
End Function
Function fromSIunit_vx(ByVal Ins As Double) As Double
  fromSIunit_vx = Ins
End Function
Function toSIunit_my(ByVal Ins As Double) As Double
  toSIunit_my = Ins
End Function
Function fromSIunit_my(ByVal Ins As Double) As Double
  fromSIunit_my = Ins
End Function