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November 9, 2015, 09:44 |
Back to the Basics...what am I missing???
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#1 |
New Member
Lee Watson
Join Date: Nov 2011
Posts: 6
Rep Power: 14 |
Problem:
I have a CHT problem. I have reduced it to a simple box of air with a heater inside. The problem is my air temperatures rise, as expected, but my density decreases as my pressure stays the same. I really expect temperature to rise. I did this in the lab by quickly evacuating air in a pressure vessel. The result was colder air than the vessel. As I monitored air pressure, as the air heated, the pressure begin to rise. What am I missing here? I'm solving steady state. If I solve transient, I get a pressure rise...?? Problem setup: Steady state Box: plastic Air: ideal gas Heater: metal sphere with volumetric heat gen Heat transfer: total energy BC: Convection on outer walls of Box. Problem is very well converged and temperatures have steadied. Air at 25C shows absolutely no change in pressure. Air Ideal Gas shows about .1Pa change in pressure....not enough to cover the 50 degC heat rise. Thanks for the input. Lee Watson TTi |
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November 19, 2015, 15:32 |
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#2 |
New Member
Nikola
Join Date: Dec 2014
Posts: 6
Rep Power: 11 |
Did you mistakenly use incompressible ideal gas (uses operating pressure and only changes density with temperature) instead of ideal gas?
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