From: Will Crowe on 13 Feb 2007 11:40
I was able to get Labview to call on Refprop for properties of a single pure fluid, but haven't been able to do this for a mixture. There seems to be a discrepency between the calls documented in the help file, and those in the Labview DLL call.
Has anyone been able to call on properties of a mixture from Labview?
From: gsussman on 14 Feb 2007 11:10
The attached zip file contains VIs in LV 7.1 format that shoud give you a leg up on getting going with Refprop.
The code supports pure fluids as well as mixtures, but only a couple of
the calculations functions (SATP, SATT, TPFLSH), however it should give
you a good baseline for working out any of the other Refprop functions.
Refprop7 LV Code71.zip:
http://forums.ni.com/attachments/ni/170/229897/1/Refprop7 LV Code71.zip
From: Will Crowe on 20 Feb 2007 12:10
Thank you for those VI's.
However, I still seem to have the same problem, namely how to get properties of a mixture back from the Refprop DLL. The "refrigerant file" input in your VI is a single string which can take a single refrigerant (pure fluid) name. When I try to enter a mixture name into this string control, nothing is returned.
In the DLL descriptions that come with Refprop (for theSETUP subroutine) it names one of the inputs as "hfiles" and refers to this as an "array of file names specifying fluid/mixture components for each of the nc components". However, the control is a string control, not an array, so I can't figure out how you enter in several fluid names, to make up a mixture. I also don't know where you specify which mixture (the name, eg. R404A) that you want.
If I could just get these calls right, I think everything else would be OK. Certainly I can get labview to call in properties for a single fluid very easily, but I can't work it for a mixture.
I really appreciate your help,
From: gsussman on 20 Feb 2007 13:40
LabVIEW missed a couple of wires in the file read code when I backward compiled it from 8.2 to 8.0 to 7.1
Try this recompiled version. I verified it works with pure fluids and mixtures.
Look in the VI tree at the example (Refprop Example.vi).
Using this code, both pure fluids and mixtures are handled the exactly the same way.
Message Edited by gsussman on 02-20-2007 12:19 PM
Refprop 7.0 Recompiled.zip:
http://forums.ni.com/attachments/ni/170/231069/1/Refprop 7.0 Recompiled.zip
From: Will Crowe on 21 Feb 2007 12:40
I tried these VI's and managed to get properties for mixtures to read, which is major progress for me. However, I'm now getting a lot of errors (the type that require Labview to shut down). These don't happen all of the time. I use the part of the code that you sent me to initialise, and then I use the "Call_TPFLSHdll+Indicators" which I got some months ago (on this thread) to read properties when values of P and T are input. Maybe you have an updated version of the routine to do this. If not, can you suggest any possible reasons for the errors?