2 replies to this topic

[mattb]

can you refresh my memory as to how to extract composition and temperature derivatives of fugacity, volume, enthalpy and entropy with VBA code from Prode Properties ?  

I have the C code working but I need to convert to VBA and I have problems with pointers,

I think there was a VBA code here posted by Paolo but I am unable to find the post at cheresources forum...

Thanks for help.

[PaoloPemi]

as for C / C++  etc. with Prode Properties you can access directly the functions to calculate

 

Fugacity + derivatives (vs. p,t,w)

Enthalpy + derivatives (vs. p,t,w)

Entropy + derivatives (vs. p,t,w)

Volume + derivatives (vs. p,t,w)

 

with VBA you need to create a space (remember first element is 0 as in C)

for example you may write something like this

 

' define space
Dim w(0 To 10) As Double
Dim dVw(0 To 10) As Double

' initialize process
process = 1
res = DPinit(process,stream)

' define composition
w(0) = 0.81
w(1) = 0.09
w(2) = 0.06
w(3) = 0.02
w(4) = 0.01
w(5) = 0.004
w(6) = 0.006
w(7) = 0.0
w(8) = 0.0
w(9) = 0.0

t = 280
p = 250000

' calculate volume and dV/dt dV/dp dV/dw
res = StrVvd(process,1,t,p,w(0),V,dVt,dVp,dVw(0))
 

in a similar way you can calculate the fugacity, enthalpy and entropy.

 

Being a direct access execution is fast,

for complex models such as CPA or SAFT you may allow some additional time for solving the association contribute,

 

Paolo

[mattb]

thanks Paolo,

I was able to extract the values following your instruction,

do you know if these are numerical or analytical ... ?

Edited by mattb, 30 March 2016 - 02:24 PM.