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-   -   Total Heat Flux Calculated by FLUENT (http://www.cfd-online.com/Forums/fluent/41956-total-heat-flux-calculated-fluent.html)

 Darron August 7, 2006 18:53

Total Heat Flux Calculated by FLUENT

Users,

wanted: how to access the total heat flux, as calculated by FLUENT, from within a UDF.

context: I have a very simple rectangular (2d) enclosure- 4 walls. I've imposed constant temperatures to three of the sides and a linearly varying temperature along the 4th wall. I'm using the S2S radiation model, and this problem is radiation only- no flow. The walls are of "0" thickness and the enclosure is just air. I want the total heat flux at each cell/face, of the wall across from the one with varying temperature. I know Fluent can calculate the heat flux (you can plot it! or use "Wall Fluxes"), but I don't know how to get to it from within my UDF - is there a way to read it in or calculate it? Another way of calculating it using other vari ables determined by FLUENT? Thank you!

 Daniele Scatolini August 9, 2006 10:32

Re: Total Heat Flux Calculated by FLUENT

for each wall zone, within a f_loop,do this: co=F_C0(f,t); /*see udf manual*/ tco=THREAD_T0(t); temp_face=F_T(f,t); temp_centroid=C_T(co,tco); BOUNDARY_FACE_GEOMETRY(f,t,A,ds,es,A_by_es,dr0);/*see manual*/ q=C_K_L(co,tco)*(temp_centroid-temp_face)/ds; /*that is q=lambda*DT/ds !*/

 Daniele Scatolini August 9, 2006 10:38

Re: Total Heat Flux Calculated by FLUENT

Don't you know how i was surprised by the fact that fluent can plot the heat flux but doesn't have a simple macro that works for each cell/face as i did! Moreover,i tested my way to compute heat flux, summing it all over the faces of a wall,and comparing it to the fluent's plot: perfect. Please, if you know how to, ask fluent inc. to enclose a similar macro in the next release! Cheers from Roma.

 Darron August 17, 2006 13:31

Re: Total Heat Flux Calculated by FLUENT

Thank you Daniele. I just found a different way- good news! FLUENT does have a hidden macro for heat flux (I don't know how anyone is supposed to figure this out- I got it through a tech support search). You can use the macro "BOUNDARY_HEAT_FLUX(f,t)" to return the total (convection, radiation, conduction) heat flux for a given face. This is flux per area, so multiply that value by the boundary's area if you want the total heat flux. I worked great in my simple model. So hopfully this macro will show up in the next eddition of the FLUENT UDF manual! --Darron

 Darth Sander June 1, 2010 07:46

Hi Darron, I have the same problem...can you tell me where is this tuttorial/tech support or send me a copy or a link? Is it possible use the MACRO BOUNDARY_HEAT_FLUX with a dynamic mesh? Thank you very much...
Bye

 andred November 16, 2010 22:17

Would you please tell us more exactly of how to use the macro

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