# Temperature does not change in Fluent simulation

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 November 15, 2017, 06:39 Temperature does not change in Fluent simulation #1 Member   Join Date: May 2017 Posts: 47 Rep Power: 9 Hello, I'm trying to simulate the heat transfer through a coil. I'm setting the heat transfer coefficient to 100 W/mēK and using a delta T of 20 K, but the temperatures barely change (you can also notice that the energy residuals don't change). However, using CFX solver with the same conditions, I get reasonable results. Does anybody have any clue what could be wrong, please? Boundary conditions: Inlet:velocity - 2 m/s temperature - 298.15 KOutlet:gauge pressure - 0 Pa Backflow temperature - 300 KWalls:no slip thermal - check attached figure 1 (I've set no solid walls for simplicity)1.png residuals.png Fluent.jpg CFX.jpg Attached figures: 1 - Wall thermal B.C.; 2 - Fluent residuals; 3 - Fluent post-processing; 4 - CFX post-processing. Thanks in advance.

 November 15, 2017, 19:59 #2 Senior Member   Alexander Join Date: Apr 2013 Posts: 2,363 Rep Power: 34 at inlet you have temperature - 298.15 K at outlet temperature - 300 K Fluent is trying to find solution according to your BC. I have no idea why the temperature goes down in CFX, if you have the same BC there You may try to use outflow BC in outlet Best regards

November 16, 2017, 10:36
#3
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Lucky
Join Date: Apr 2011
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Quote:
 Originally Posted by AlexanderZ at inlet you have temperature - 298.15 K at outlet temperature - 300 K s
That's a backflow temperature (an inlet temperature when there is reversed flow). The 300 K is not a hard BC.

Quote:
 Originally Posted by LThomes Does anybody have any clue what could be wrong, please?
It is a debugging problem I guess. Try using very stupid settings like 1000000 HTC.

November 16, 2017, 10:57
#4
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Quote:
 Originally Posted by AlexanderZ at inlet you have temperature - 298.15 K at outlet temperature - 300 K
As LuckyTran said, 300 K is the backflow temperature at the outlet, it does not set the outlet temperature to a constant 300 K.

Thanks for the replies.

 Tags change, coil, heat, temperature, transfer