View Full Version : How to calculate enthalpy?

19-10-2005, 11:40 AM
How to calculate enthalpy for R22 from the 4 basic equations? i.e.

1.Vapour pressure equation
2. Equation of state
3. Density of the saturated liquid
4. Heat capacity of the vapour

US Iceman
19-10-2005, 04:34 PM
The information you are looking for was supplied by the refrigerant manufacturers. Dupont and others used to provide a bulletin that contained the thermodynamic properties and equation of state (EOS) calculations.

The EOS information was in the front of the bulletin.

I have looked on several websites, and it appears the EOS calculations have been omitted from the property information in the current bulletins.

If this is something you really need and cannot find elsewhere I suggest the following:


This is a program you can purchase. Contained in the program appendix are the EOS calculations for the different refrigerants.

You can also compile a file from this software code to link to Excel or other programs.

If you have not done this before... Be prepared to spend a lot of time doing so.

US Iceman

US Iceman
19-10-2005, 06:12 PM
After much searching I found what you are looking for. This is from an old copy I have of R-22 properties. Everything is in Imperial units so you will have to do the conversions into and out of the equations if you are using SI.

Good luck.

US Iceman

20-10-2005, 05:26 AM
Thanks Iceman. But how to calculate Enthalpy value from the equations? :confused:

20-10-2005, 06:56 AM
Hi Thing,
ehthalpy=Cp*T,iceman offered equation can get Cv,so that you can get enthalpy by h=CvT+pv. Details you can refer to ASRHRE handbook fundamentals. If need ,pls give me your email.


29-10-2005, 03:10 PM
Mate I'd be getting my hands on the molier chart and plotting it. The equations will only make sense when you can see the refrigeration system right in front of you.

Thats my 2 cents