Air Heating Up Rapidly

Metallic · January 1, 2019, 14:14

Hey guys,

I have made a transient cfx simulation consisting of two concrete slabs and air between them (with steel members too but this is irrelevant). I have defined all the materials and boundary conditions and i am heating up with temperature (time dependent) one side (wall) of the "sandwich". My problem is that after convergence post shows that actually concrete heats up at a reasonable rate that makes sense but the air in-between has unexplained crazy high temp. What am i missing? Cant find what the problem is....

I am a beginner in CFX (actually is my first simulation) coming from the mechanical background so be gentle

ghorrocks · January 2, 2019, 06:24

Is your simulation adequately converged? I strongly suspect not. Converge to a tighter tolerance. Also, for Conjugate Heat Transfer (CHT) simulations like this you should include imbalances in the convergence criteria. Residuals alone are a poor estimate of convergence for CHT simulations.

Metallic · January 16, 2019, 15:20

Hey thanks for your answer! I will check it out thoroughly during the next days and come back to you, if there is any progress.

January 1, 2019, 14:14	Air Heating Up Rapidly	#1
Metallic New Member Thomas Join Date: Jan 2019 Location: GR Posts: 4 Rep Power: 7	Hey guys, I have made a transient cfx simulation consisting of two concrete slabs and air between them (with steel members too but this is irrelevant). I have defined all the materials and boundary conditions and i am heating up with temperature (time dependent) one side (wall) of the "sandwich". My problem is that after convergence post shows that actually concrete heats up at a reasonable rate that makes sense but the air in-between has unexplained crazy high temp. What am i missing? Cant find what the problem is.... I am a beginner in CFX (actually is my first simulation) coming from the mechanical background so be gentle

January 2, 2019, 06:24		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,870 Rep Power: 144	Is your simulation adequately converged? I strongly suspect not. Converge to a tighter tolerance. Also, for Conjugate Heat Transfer (CHT) simulations like this you should include imbalances in the convergence criteria. Residuals alone are a poor estimate of convergence for CHT simulations. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

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January 16, 2019, 15:20		#3
Metallic New Member Thomas Join Date: Jan 2019 Location: GR Posts: 4 Rep Power: 7	Hey thanks for your answer! I will check it out thoroughly during the next days and come back to you, if there is any progress.