topic Re: refprop in LabVIEW

refprop

jacbenimble — Wed, 28 Sep 2005 17:23:04 GMT

Hello,

I was wondering if anyone has ever completed an application accessing REFPROP from NIST.

I have used other DLL’s with the CIN tool but can not seem to make this REFPROP DLL work.

If anyone has a code snippet showing the settings of the CIN tool that is using REFPROP, it would be greatly appreciated.

Re: refprop

Travis_M. — Thu, 29 Sep 2005 20:08:03 GMT

Hello Jackbenimble,

It sounds like you are able to call other DLLs properly, so I am assuming that there is no problem from the LabVIEW end of things. I searched and found a link to a patch for the software I believe you are trying to call here. If you have any questions on exactly how to call third party DLLs please let us know -- I am more than happy to provide some documentation and help on that.

Hope that link helps. Have a great afternoon!

Regards,

Re: refprop

gsussman — Sun, 20 Nov 2005 16:12:43 GMT

Any new developments on this front?

I also need to access the Refprop DLL and can't seem to get the calling convention down. I have done a bunch of other DLL/labview interfaces before, however this one does not seem to conform to the normal rules of LabVIEW and dll calls.

Re: refprop

Travis_M. — Tue, 22 Nov 2005 22:29:02 GMT

Hello,

I don’t know about the specific problems with this DLL, but LabVIEW is only able to call with C or STDCALL (WINAPI) calling convention. The DLL seems to have a known issue (linked above) with some installation issues. I do not know if the customer above was able to get the software working, but please let us know if you have any questions on how to use the Call Library Function Node VI in LabVIEW with either calling convention.

Have a great day!

Re: refprop

jacbenimble — Tue, 22 Nov 2005 22:39:01 GMT

Yes, I was able to get this to work. I e-mailed Dr. Lemmon and he was more than happy to provide examples of his code being called by LabView. I am passing them on just as received. If you make more VIs, would you please forward them, or post them. We would all find some benifit in the shared work. Thanks John

Re: refprop

gsussman — Tue, 22 Nov 2005 22:39:38 GMT

I spoke to a guy at NIST yesterday. He was able to send me a copy of a couple of VIs that somebody cobbled together to initialize and make one function call. Hopefully within the next couple of weeks (time permitting) I will have time to clean up those calls as well as implement some of the other calls in a more standard driver format.

The problem with Refprop is not with the dll, per se, but more due to the somewhat cryptic way the parameters are entered.

I plan on submitting my finished VIs back to NIST for inclusion with the next version of Refprop that will be releasing sometime early next year.

Re: refprop

gsussman — Tue, 22 Nov 2005 22:41:33 GMT

Jack.....it looks like you got the same VIs I did, and from the same guy by the way.

When I get my code together I will post it with NIST as possibly on my FTP site.

Re: refprop

Will_Crowe — Tue, 13 Feb 2007 16:37:14 GMT

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?

Re: refprop

gsussman — Wed, 14 Feb 2007 15:55:22 GMT

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.

Re: refprop

Will_Crowe — Tue, 20 Feb 2007 17:05:16 GMT

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,

Will

Re: refprop

gsussman — Tue, 20 Feb 2007 18:19:19 GMT

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

Re: refprop

Will_Crowe — Wed, 21 Feb 2007 17:32:32 GMT

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?

Regards,

Will

Re: refprop

gsussman — Wed, 21 Feb 2007 17:40:31 GMT

Unfortunately I don't have any functions other than the ones that are included in the zip file I sent you.

LabVIEW errors (the type that require a shutdown) when calling a DLL are normally indicative of passing the DLL the wrong data type(s) or passing arguments that don't have the correct preinitialized size. LabVIEW does not allow allocation of memory by the DLL, LV must pass all parameters to the dll padded to specific lengths. The same holds true for any data retruned from the DLL.

The best advise I can give you is to use the code I sent you as a baseline for extending the functionality to other Refprop function calls.
Use the calling convention detailed in my code. DO NOT use the calling conventions used in the code you originally received from NIST. The NIST calling conventions are not formatted 100% correctly. They will work for pure fluids but will fail when attempting to work with mixtures.

Re: refprop

jacbenimble — Wed, 21 Feb 2007 18:01:29 GMT

I believe that most of these calculations have limits on the ranges. If a calculation attempt is made and the data input is not a reasonable number you will get this error. Maybe you could use some sort of valid range check before attempting the call. You could use the example Excel program supplied on with the NIST CD to check the response with the given data. I believe that if you attempt to give it data that is out of range it will respond with an error and allowable ranges. (In the excel example)

- There are 10 kinds of people in the world, those that know binary, and those that don't

Re: refprop

gsussman — Wed, 21 Feb 2007 22:04:45 GMT

You are correct about the allowable ranges, however that should only generate an error in the error cluster, and appropriate error source text.
Range checking would be a pretty difficult operation in that in many cases you have multi variable dependence. My recomendation would be to simply perform the calculation and pick up any errors returned by Refprop.

That being said, I believe the error that he described (LV crashes) is the result of an improper DLL call.

Re: refprop

Will_Crowe — Thu, 22 Feb 2007 23:13:08 GMT

As you say, I don’t think that it’s due to out of range values because sometimes it doesn’t give the error for several runs of the program, and then it appears even though the input values (and therefore the returned values) haven’t changed.

I tried to see if the error correlated with anything (time intervals between runs etc.) and the behaviour is pretty eratic – sometimes the program runs and sometimes it crashes.

One strange thing that happens if I’m editting the program that calls TPFLSHdll, is that

when I go to save or close the changed program, I occasionally get a report of an “insane” object and then a message saying there has been a Fatal Internal Error. So, even when I don’t run the VI that links to the DLL, but simply edit the program that contains this VI, unusual errors can arise.

I will try to check the calls to the DLL, but they seem to be what’s documented by NIST. Also, would the fact that it works fine for pure substances not suggest that the calls are OK?

Regards, Will.

Re: refprop

Will_Crowe — Tue, 10 Apr 2007 16:55:19 GMT

Dear gsussman,

I have been using the VI's that you posted to this forum to extract properties for R404A from refprop, and I am delighted to say that they are working well. The files that I earlier got from NIST were giving intermittent errors, on which subject you commented previously in this thread. I am currently using the TPFLSH routine to extract enthalpy values when P and T values are input. I would like, now, to do a similar routine for for PHFLSH (as I cannot find entropy with a PT input pair for one of the points) and I was hoping to look at the code of your TPSLSH routine. All that I wish to check is what is different about your call to the DLL and the call in the VI posted by NIST, that makes your one stable, and the other one crash. Would it be possible to get a non-passworded version of TPFLSHdll.VI to check this? I know this is a bit cheeky, but many of the other VI's that you posted are not passworded, and it would probably unlock the reason for the errors and allow me to develop other similar VI's.

Regards,

Will

Re: refprop

AustinPeter — Thu, 17 Apr 2008 10:52:42 GMT

Hi guys,

I see you have already come accross my problem before!

I am looking to get hold of the converter of refprop for use with simply converting nominal density values into pressure. I have used all the SubVI measurements that you have sent me already but none of them see to have the function that i actually need. Was just wandering if I was going about this the wrong way or there was something else that might be helpful out there.

Basically I just want to use the pressure and density functions. of the dll. I have some VB code which seems to be doing it ok. Any ideas. Would be great to get in contact about this. Best regards Pete Davies

davies.pg@gmail.com

Re: refprop

gsussman — Fri, 18 Apr 2008 15:48:42 GMT

Pete Just because the actual DLL call to the specific REFPROP function you need is not included in the supplied VIs, does not necessarily mean that it is not available in the REFPROP dll. The code developed was only those functions that I required when I built my original app. There was quite a number of functions that have not been included. If you can perform the function using the actual REFPROP exe file then there is a way to do it using the LabVIEW calls (some included, some you will have to build yourself). The key to doing it is to use the functions I posted earlier in this thread as a baseline for creating your own functions. Be very aware of the data sizes of the inputs to the DLL. Most of my code checks and formats it properly so don't strip that out by accident. Regards, Greg

Re: refprop

jon_mcbee — Thu, 12 Feb 2009 23:47:34 GMT

Hello, I have downloaded your Refprop zipped file for LV 7, thak you very much for your time and effort here. I am missing the Refprop.dll, I guessing that it is not included in your zipped folder but I wanted to be sure. Where would I find the Refprop.dll? Thanks.