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

MarioArias · March 9, 2015, 23:08

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, 08:14

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, 09:21

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, 15:54

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 9, 2015, 23:08	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, 09:21	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

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March 10, 2015, 08:14		#2
vasava Senior Member Paritosh Vasava Join Date: Oct 2012 Location: Lappeenranta, Finland Posts: 732 Rep Power: 22	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, 15:54		#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.