# Air density variation

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 November 15, 2014, 14:46 Air density variation #1 Senior Member     hamed Join Date: Apr 2009 Posts: 148 Rep Power: 10 hi dear friends. i am modeling an air intercooler that cool's down compressed air.so air density changes(increases) while passing throw the intercooler and i need to monitor density and temperature variation. the problem is that i cant define air proper density at inlet BC. the air pressure is 2 bars and the temperature is equal to 146 deg of centigrade and a mas flow of 0.26kg/sec at inlet. how can i set the pressure and mass flow together at inlet Bc?how should i chenge the material properties to have the right air density at pressure and temperature variation? the velocity is about 3 to 12 m/sec and is far far away from speed of sound.i dont know if i should model a compressible flow?i know air can be assumes as ideal gas in my situation but how can i define the right density at inlet and monitor its variation throw the intercooler?

November 16, 2014, 05:13
#2
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Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
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Quote:
 how can i set the pressure and mass flow together at inlet Bc?
You can't. It is mathematically over specifying the flow so it is not possible. Instead put the mass flow rate boundary on the outlet and the pressure condition at the inlet. Easy fixed.

You will need to use the total energy model so the temperature can affect the density. (Just read the doco and it suggests a Thermal Energy model would also do it but I thought that was a constant density model)

 November 16, 2014, 06:28 #3 Senior Member     hamed Join Date: Apr 2009 Posts: 148 Rep Power: 10 Tnx gelenn .I really appreciate your guides

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