Attribute VB_Name = "Module444"
Public Function CalCS(Pstart As Double, Tstart_rankine As Double, Tlast_rankine As Double, G As Double, QG_mscfd As Double, Length_feet As Double, Intervals As Integer, Angle_radians As Double, Dia_inches As Double, Roughness_inches As Double) As Double
Rem          Cullender and Smith Correlation VBA Function
Rem          For personal use only. 
Rem          Code developed for use in Louisiana State University course PETE 4051
Rem          "Reserve Evaluation and Reservoir Management"
Rem          Spring Semester 2002. Adapted for distribution in connection with 
Rem          the Oklahoma Geological Survey.
Rem          Written By: Dr. R. G. Hughes
Rem                      2/1/2002
Rem          After Two-Phase Flow in Pipes by Brill and Beggs
Rem

      Dim Pave As Double
      Dim Pst As Double
      Dim Tave As Double
      Dim SINANG As Double
      Dim z As Double
      Dim mug As Double
      Dim DL As Double
      Dim Q_scfd As Double
      Dim P1, Told, Pold, Pnew1, Diff, Tnew As Double
      Dim I As Integer
      
      Told = Tstart_rankine
      Pold = Pstart
      Pst = Pstart
      SINANG = Cos(Angle_radians)
      DL = Length_feet / Intervals
      Pnew1 = Pold + 0.25 * (Pst / 100) * (DL / 100)
      
      For I = 1 To Intervals
         Tnew = Tstart_rankine + (Tlast_rankine - Tstart_rankine) / Length_feet * I * DL
         Tave = (Told + Tnew) / 2#
         
         Pave = (Pnew1 + Pold) / 2#
         z = zfact(Pave, Tave, G, 0#, 0#)
         mug = gasvis(Pave, Tave, G, z)

         Pnew2 = CULSTH(Pst, G, Tave, DL, QG_mscfd, -1, Dia_inches / 12#, SINANG, z, mug, Roughness_inches)
      
         Pst = Pnew2
      
      Next I

      CalCS = Pnew2
      
End Function

Public Function CULSTH(P1 As Double, SGPG As Double, T As Double, DIST As Double, Q As Double, ICONV As Integer, Dia As Double, SINANG As Double, z As Double, VISG As Double, Ed As Double) As Double

      Dim REN As Double
      Dim DIAIN As Double
      Dim P2 As Double
      Dim Pyo As Double
      Dim Pold As Double
      
      VD = DIST * SINANG
      DIAIN = Dia * 12#

Rem Friction Factor Calculation
      If (Q > 0#) Then
         REN = 20011# * SGPG * Q / 1000# / DIAIN / VISG
         F = FrFact(REN, Ed / DIAIN)
      Else
         F = 0#
      End If

      FSQ = 0.000667 * F * Q ^ 2 / (DIAIN) ^ 5
      
      P2 = P1 + 0.25 * (P1 / 100) * (DIST / 100)
      Pold = P1
      Pyo = P1
      ICONV = 1

25    For J = 1 To 150
         If (Abs(P2 - Pold) > 0.000001) Then
            Pold = P2
            z1 = zfact(Pyo, T, SGPG, 0, 0)
            z2 = zfact(P2, T, SGPG, 0, 0)
            P2FAC = P2 / ((T) * z2)
            P1FAC = Pyo / ((T) * z1)
            ZI2 = P2FAC / ((P2FAC ^ 2 * VD / DIST) + FSQ)
            ZI1 = P1FAC / ((P1FAC ^ 2 * VD / DIST) + FSQ)

            P2 = Pyo + (0.01875 * SGPG * DIST / (ZI2 + ZI1))
         
         Else
            If (ICONV < 2) Then
               Pold = P2
               Pyo = P2
               P2 = Pyo + 0.25 * (Pyo / 100) * (DIST / 100)
               ICONV = 3
               J = 1
            Else
               CULSTH = P2
               Exit Function
            End If
         End If
      Next J

End Function