LabVIEW Example doesn't work on Mixture

[fabioint]

Hello,
I tryed to use the LabVIEW Example with Mixture and it seem doesn't work.

[Matthew-Boyd]

Can you provide more details, including a screenshot of the LabVIEW VI?

[ryankall82]

I copied the REFPROP.dll 32 bit version to my labview wrapper folder and I get these errors and the vi is broken:

[Matthew-Boyd]

The REFPROP VI is only for 32-bit LabVIEW, which may be your issue.

[fabioint]

Hi @Matthew-Boyd ,
thank you for your reply, and please excuse me for the delay in getting back to you.
I’m using LabVIEW 2024 (32-bit), and I'm running the example I found in the repository. As you can see, when I try to evaluate the parameters and set a mixture, I encounter an error.

[Matthew-Boyd]

This is a standard error from REFPROP, so your VI appears to be communicating with the library (DLL) fine. I am unable to replicate your error for 176.85 K and 201 kPa, so I would check your units. REFPROP has a few 'SI' unit systems, where pressure is either in P, kPa, or MPa (there's also bar). Note that the critical and max condentherm pressure for R454C is around 4.3 MPa. If you have the UI, you can verify this via Substance -> Fluid Information or use the UI to troubleshoot in general.

[nist-aharvey]

The error message suggests some sort of units problem somewhere. It says the critical (or max condentherm) pressure Pc is 0.15E-02 MPa, which is unphysically low (based on Matthew's number above, it is low by a factor of about 300, when I might have expected a factor of 1000). I suspect something somewhere (perhaps just the printing of the message) is off by a factor of 1000.
201 MPa would be out of range, but 201 kPa should be fine.
If it is a problem with pressure units, it might be easier to debug with a pure component where you don't have to worry about mixture phase envelopes which can be tricky. If the problem only happens with a mixture, that fact would aid the diagnosis of any possible bug.

By the way, if you are working with this particular mixture, there has been some better optimization since the release of REFPROP version 10. The new mixture model is described in this paper:
https://doi.org/10.1063/5.0135368
and it used a new EOS for 1234yf that is described in this paper:
https://doi.org/10.1007/s10765-022-03015-y
Both papers have supplementary material with files that can be used with REFPROP.

[fabioint]

@Matthew-Boyd
Thank you very much for your reply. I can’t understand why you are unable to reproduce my error. Do you mean that you see different values in your interface?
The VI screenshot I posted refers to the project I downloaded from the repository.
It’s certainly a library issue; before starting any debugging I wanted to check whether any other LabVIEW user had encountered the same problem and already found a solution

[fabioint]

@nist-aharvey you’re right — the error is in the units. I took a look at the code and in my opinion there are a few things that don’t seem correct. But before making any changes, I preferred to write here to check whether someone else had encountered the same issue before me and already found a solution.

[fabioint]

Hi, I found the issue.

I'm in Italy and here we use the comma as the decimal separator. Because of this, the wrapper was reading the REFPROP fluid/mixture files incorrectly, which led to the error I reported.

For now I temporarily solved the problem by changing the numeric regional settings on my PC, but since I don’t consider this a robust solution, I’m currently modifying the code to handle the decimal separator properly.

Once I finish the modification, I will share the proposed change here.

[Matthew-Boyd]

Thank you for letting us know--we will add this to our own bug report and also investigate ourselves. Much appreciated, and I look forward to seeing your modification.