UDF for heat convection coefficient with fixed surface temperature

Boo85 · July 10, 2012, 08:57

Hello everyone.

I am basically doing a simulation for air flow in a room.

What i would like to know if it would it be possible to specify a fixed heat transfer coefficient for the heat transfer into the fluid domain and a fixed surface temperature for a surface as boundary conditions?

Would it be possible with a UDF? I was looking through the UDF manual and saw that Define_Profile allow for the specification of a heat transfer coefficient, however i think its for an external flow outside the domain. Am i right?

CFX has this feature that allows for the specification of heat transfer coefficients via CCL by replacing the turbulent wall function.

Therefore how would it be possible to create a UDF to allow the input of both Heat transfer coefficient and fixed surface temperature into the fluid domain. If so can anyone direct me to a right direction.

Thanks alot!

flotus1 · July 10, 2012, 10:38

If the fluid is inside the domain you are simulating, the heat transfer coefficient cannot be a constant value.

It depends on the flow and turbulence conditions next to the wall, which are a result of the simulation.

Boo85 · July 10, 2012, 18:43

I felt this was funny at first as the heat transfer into the fluid in cfd is due to the fluid flow thus usually a convective heat transfer coefficient is not defined. however I have seen papers that do this by disabling the wall functions and fixing a heat transfer coefficient instead.

cfx also allows for this, via a ccl by change the wall functions. that's y I am wondering if fluent can do the same.

July 10, 2012, 08:57	UDF for heat convection coefficient with fixed surface temperature	#1
Boo85 New Member Chun Wheng Join Date: Aug 2011 Posts: 5 Rep Power: 14	Hello everyone. I am basically doing a simulation for air flow in a room. What i would like to know if it would it be possible to specify a fixed heat transfer coefficient for the heat transfer into the fluid domain and a fixed surface temperature for a surface as boundary conditions? Would it be possible with a UDF? I was looking through the UDF manual and saw that Define_Profile allow for the specification of a heat transfer coefficient, however i think its for an external flow outside the domain. Am i right? CFX has this feature that allows for the specification of heat transfer coefficients via CCL by replacing the turbulent wall function. Therefore how would it be possible to create a UDF to allow the input of both Heat transfer coefficient and fixed surface temperature into the fluid domain. If so can anyone direct me to a right direction. Thanks alot!

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July 10, 2012, 10:38		#2
flotus1 Super Moderator Alex Join Date: Jun 2012 Location: Germany Posts: 3,399 Rep Power: 46	If the fluid is inside the domain you are simulating, the heat transfer coefficient cannot be a constant value. It depends on the flow and turbulence conditions next to the wall, which are a result of the simulation.

July 10, 2012, 18:43		#3
Boo85 New Member Chun Wheng Join Date: Aug 2011 Posts: 5 Rep Power: 14	I felt this was funny at first as the heat transfer into the fluid in cfd is due to the fluid flow thus usually a convective heat transfer coefficient is not defined. however I have seen papers that do this by disabling the wall functions and fixing a heat transfer coefficient instead. cfx also allows for this, via a ccl by change the wall functions. that's y I am wondering if fluent can do the same.