Peng Robinson Real Gas Model

cfd seeker · September 30, 2013, 03:25

Hi

I am trying to validate the experimentally tested Pressure Reducer. Pressure reducer reduces the Inlet pressure of 250 bars to approx. 5 bars.

Under such high pressure air cannot be treated as Ideal Gas. Because my intuition is under such large pressure variation from Inlet to Outlet, there will be large variations in both Density and Temperature of the air. So I am thinking of using Peng Robinson real gas model in CFX.

I am using Static Pressuer at Inlet and Mass Flow at Outlet Boundary Conditions.

My question: Is this model suitable under the mentioned conditions? Further there are many properties needs to be set for this model. For Specific Heat Capacity, values of some coefficients are required( Zero Pressure Gradient coefficients for modeling variable heat capacity). How to set these values for air?

Any help is appreciated.

Regards

ghorrocks · September 30, 2013, 18:20

If you have doubts about the model then the best thing to do is to run a benchmark case at similar conditions where you have high quality known answers for. These should be easily available for something like this - you should be able to get flow though an oriface up to very high pressures and that sounds like a good benchmark case to test the accuracy of different models.

September 30, 2013, 03:25	Peng Robinson Real Gas Model	#1
cfd seeker Senior Member Join Date: Mar 2011 Location: Germany Posts: 552 Rep Power: 20	Hi I am trying to validate the experimentally tested Pressure Reducer. Pressure reducer reduces the Inlet pressure of 250 bars to approx. 5 bars. Under such high pressure air cannot be treated as Ideal Gas. Because my intuition is under such large pressure variation from Inlet to Outlet, there will be large variations in both Density and Temperature of the air. So I am thinking of using Peng Robinson real gas model in CFX. I am using Static Pressuer at Inlet and Mass Flow at Outlet Boundary Conditions. My question: Is this model suitable under the mentioned conditions? Further there are many properties needs to be set for this model. For Specific Heat Capacity, values of some coefficients are required( Zero Pressure Gradient coefficients for modeling variable heat capacity). How to set these values for air? Any help is appreciated. Regards

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September 30, 2013, 18:20		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	If you have doubts about the model then the best thing to do is to run a benchmark case at similar conditions where you have high quality known answers for. These should be easily available for something like this - you should be able to get flow though an oriface up to very high pressures and that sounds like a good benchmark case to test the accuracy of different models.