www.squinch.org

• Paramdl:
  
• Arrange calculation parameters to match entered species.  Calculation allows for 21 standard components.  Paramdl packs the ones that are used into sets of working arrays.
• NOTE: The order of the components appears to be important, as it affects the results returned.  Each gas species has an integer ID.  These IDs must be processed in ascending numerical order for the result to be correct.
  
• Chardl:
  
• Characterises the gas by calculating parameters b1..b18, and various other parameters, in a pair of for loops.
• Normalise component mole fractions (ensure the total = 1.0000)
  
• for i=1 to (number of entered components)
• Calculate gas mix mole weight = running total of mole fraction[i]*mole weight[i]
  
• Calculate running total of mole fraction[i]*rki[i]^2.5
  
• Calculate running total of mole fraction[i]*ei[i]^2.5
• Calculate running total of mole fraction[i]*wi[i]
• Calculate running total of mole fraction[i]*qi[i]
• Calculate running total of hi[i]*(mole fraction[i])^₂
  
• for j = i to (number of entered components)
• This loop calculates interactions between one gas species and another.
  
• xij = xi[i]*xi[j] (if i <> j, we double this number)
• eij = beij[i][j] * sqrt(ei[i]*ei[j]) : energy interaction param
  
• s3 = xij*sqrt(rki[i]³*rki[j]³)
• calculate b1..b18 as running totals of various polynomials on s3, eij, etc.
• At end of loops, scale b parameters: bi = bi * a[i]
  
• calculate gas base density;
  
• calculate base compressibility.
  
• temp(Tflowing):
  
• calculate temperature dependent parameters fn[13]..fn[58]
  
• ddetail(Pflowing, Tflowing):
  
• Call braket(t, p) to determine a lower and upper limit on the gas density;  begin an iterative loop to converge on the density, as follows:
  
• Loop:
• Sort pressure and density points in order of decreasing pressure.
  
• Calculate the amount of density change, delx, at pressure point y2
  
• If we have converged, return x2 + delx , else...
• Save current x2 and y2 as x1 and y1;
  
• calculate x2 as x2 + delx
• calculate y2 as pdetail(x2,t)-p
  
• for at most 150 iterations.
• braket(t,p):
• Braket iterates to find a molar density on either side of the "correct answer" and returns these.  This narrows the range over which ddetail needs to converge.
  
• pdetail(d,t):
  
• calculates compressibility with zdetail(d,t) and returns the pressure.
• zdetail(d,t):
  
• calls temp(t) if the temperature has changed, then returns a polynomial equation based on density, bmix and the parameters fn[13..58].