Simulating a "Pseudo-water" flow

mikemech · May 18, 2011, 08:06

Hello.

I am trying to calculate the flow inside a heat exchanger, and I am using the "BuoyantSimpleFoam" solver. This solver assumes air and its corresponding thermophysical properties. The thing is, I want to have water instead, so I tried to change the values of thermophysical properties and transport properties so as to simulate "water". So, the original thermophysical properties file was this:

thermoType hPsiThermo<pureMixture<constTransport<specieThermo <hConstThermo<perfectGas>>>>>;
mixture air 1 28.96 1004.4 0 1.831e-05 0.703;

And I modified it so it looks like this:
thermoType hPsiThermo<pureMixture<constTransport<specieThermo <hConstThermo<perfectGas>>>>>;
mixture air 1 18 4213 0 298e-06 1.96;

As you can see, I just substituted Molecular Weight, Cp, latent heat of fusion and Prandtl Number with the values that correspond to water in 95 degrees Centigrade. I also substituted nu in transportProperties file with the value 0,29e-06.

My question is, if all these modifications are enough so as to run a peudo-water flow with BuoyantSimpleFoam solver ? Or I do I need to change other parameters as well?

Thanks in advance

vkrastev · May 18, 2011, 10:22

I think that you will get incorrect results, as using these settings will produce a density field calculated with the equation of state for perfect gases, which of course cannot be applied to liquid (incompressible) water. There is a much more elegant solution to your problem: use the last updated version of chtMultiRegionSimpleFoam, which allows to set an incompressible equation of state for liquids (if you have an updated 1.7.x version of OpenFOAM, then the solver has already these capabilities, if not take a look here http://www.cfd-online.com/Forums/ope...tml#post299931 to find where to download the modified source code)

Hope this helps

V.

May 18, 2011, 08:06	Simulating a "Pseudo-water" flow	#1
mikemech New Member Mike Join Date: May 2011 Posts: 19 Rep Power: 15	Hello. I am trying to calculate the flow inside a heat exchanger, and I am using the "BuoyantSimpleFoam" solver. This solver assumes air and its corresponding thermophysical properties. The thing is, I want to have water instead, so I tried to change the values of thermophysical properties and transport properties so as to simulate "water". So, the original thermophysical properties file was this: thermoType hPsiThermo<pureMixture<constTransport<specieThermo <hConstThermo<perfectGas>>>>>; mixture air 1 28.96 1004.4 0 1.831e-05 0.703; And I modified it so it looks like this: thermoType hPsiThermo<pureMixture<constTransport<specieThermo <hConstThermo<perfectGas>>>>>; mixture air 1 18 4213 0 298e-06 1.96; As you can see, I just substituted Molecular Weight, Cp, latent heat of fusion and Prandtl Number with the values that correspond to water in 95 degrees Centigrade. I also substituted nu in transportProperties file with the value 0,29e-06. My question is, if all these modifications are enough so as to run a peudo-water flow with BuoyantSimpleFoam solver ? Or I do I need to change other parameters as well? Thanks in advance

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May 18, 2011, 10:22		#2
vkrastev Senior Member Vesselin Krastev Join Date: Jan 2010 Location: University of Tor Vergata, Rome Posts: 368 Rep Power: 20	I think that you will get incorrect results, as using these settings will produce a density field calculated with the equation of state for perfect gases, which of course cannot be applied to liquid (incompressible) water. There is a much more elegant solution to your problem: use the last updated version of chtMultiRegionSimpleFoam, which allows to set an incompressible equation of state for liquids (if you have an updated 1.7.x version of OpenFOAM, then the solver has already these capabilities, if not take a look here http://www.cfd-online.com/Forums/ope...tml#post299931 to find where to download the modified source code) Hope this helps V.