UDF for a constant heat flux minus radiation based on face temperature

MarioArias · March 10, 2015, 00:08

I am trying to write a UDF which takes a total constant heat flux boundary condition, but also accounts for the radiative loses. I would like it to use the local face temperature to determine the net heat flux that should be applied at that node face.

If this is possible I would greatly appreciate some information.

Or if there is a better way of accounting for surface-to-ambient radiative loses, I would gladly take that advice.

Thanks,
Mario

vasava · March 10, 2015, 09:14

If I am not wrong, there are no macros for obtaining radiation related information on node, cell or face. You may have to manually process data exported from Export-->Solution Data option.

MarioArias · March 10, 2015, 10:21

Thanks for you reply.

I understand there is no radiation information, but couldn't I simply use the following equation in the UDF:

$Q''_{net} = Q''_{total} - \epsilon\sigma(T_{face}^{4}-T_{ambient}^{4})$

There must be a simple way to calculate the effects of surface-to-ambient radiation when applying a heat flux, it is such a basic concept.

I must be missing something.

Thanks again,
Mario Arias

`e` · March 10, 2015, 16:54

You could use your own calculation for radiation losses inside a custom boundary condition using a DEFINE_PROFILE macro. Loop through the faces using begin_f_loop and end_f_loop. The face temperature could be found with F_T(f,t) and the ambient temperature could either be found in another cell zone (if you are simulating the surrounding environment) or hard coded.

March 10, 2015, 00:08	UDF for a constant heat flux minus radiation based on face temperature	#1
MarioArias New Member Mario Arias Join Date: Mar 2015 Posts: 6 Rep Power: 11	I am trying to write a UDF which takes a total constant heat flux boundary condition, but also accounts for the radiative loses. I would like it to use the local face temperature to determine the net heat flux that should be applied at that node face. If this is possible I would greatly appreciate some information. Or if there is a better way of accounting for surface-to-ambient radiative loses, I would gladly take that advice. Thanks, Mario

March 10, 2015, 10:21	What about using temperature?	#3
MarioArias New Member Mario Arias Join Date: Mar 2015 Posts: 6 Rep Power: 11	Thanks for you reply. I understand there is no radiation information, but couldn't I simply use the following equation in the UDF: $Q''_{net} = Q''_{total} - \epsilon\sigma(T_{face}^{4}-T_{ambient}^{4})$ There must be a simple way to calculate the effects of surface-to-ambient radiation when applying a heat flux, it is such a basic concept. I must be missing something. Thanks again, Mario Arias

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
mass flow in is not equal to mass flow out	saii	CFX	12	March 19, 2018 06:21
Radiation Modeling	Chris89	CFX	20	August 14, 2014 08:51
Implement constant heat flux boundary condition	new_at_this	Main CFD Forum	2	April 7, 2012 00:35
interchanging face information with cell information/ radiation flux UDF	ximik	FLUENT	1	May 4, 2011 17:34
how to impose experimental dat as boundary conditi	Rogerio Fernandes Brito	FLUENT	14	November 25, 2008 06:47

March 10, 2015, 09:14		#2
vasava Senior Member Paritosh Vasava Join Date: Oct 2012 Location: Lappeenranta, Finland Posts: 732 Rep Power: 23	If I am not wrong, there are no macros for obtaining radiation related information on node, cell or face. You may have to manually process data exported from Export-->Solution Data option.

March 10, 2015, 16:54		#4
`e` Senior Member Join Date: Mar 2015 Posts: 892 Rep Power: 18	You could use your own calculation for radiation losses inside a custom boundary condition using a DEFINE_PROFILE macro. Loop through the faces using begin_f_loop and end_f_loop. The face temperature could be found with F_T(f,t) and the ambient temperature could either be found in another cell zone (if you are simulating the surrounding environment) or hard coded.