Heat Transfer - how to use a surface as custom control?

Eike · October 31, 2016, 08:13

I am modeling heat transfer and want to get a surface for a local heat transfer coefficient.

I set a threshold at the interface between fluid and solid to capture the area of interest. Then I exported this surface as *.stl and importet it to another sim with the same cooled part but without the fluid region. I want to model only the solid as it is way faster and I am not interested in the fluid at this time.

Is there any way to use the imported surface as a heat flux or heat transfer coefficient?

kirrer · November 1, 2016, 10:29

From your source sim file, you can use that threshold to export a table of data (Specified Y+ HTC and temperature are usually preferred). Then, in the solid-only file you can create a Tabular Data Mapper to map data from the table to your target surface. Within the data mapper, expand Target Specifications > Surface > Proximity constraint. Enable this and set appropriately. Once it's enabled, it gives the option to set "alternate values" for cells that do not get mapped. I would recommend an HTC of 0 and temperature of 300K. Once this is defined, map it, then use the MappedSpecifiedY+HTC and Tref as the HTC and Tref boundary condition for the surface you are mapping it to.

This is the most straightforward way that I see to do what you are asking. Just keep in mind that if your solid solution changes temperature (transient or different boundary conditions), the fluid temperature would also change, which may (or may not) have a significant effect on heat transfer. By decoupling the two, you could miss this effect.

Eike · November 8, 2016, 04:42

Thanks a lot! Your answer was VERY helpful :-)

cwl · November 24, 2016, 11:42

If i got you right - you want to make a computation of heat transfer in solid (which is slow) and not waste time on solving fluid dynamics part after fluid flow has reached it's steady state.
In this case - you can select "Freeze Solver" for fluid (Pressure-Velocity) in Solver controls and thus only energy equations will be solved which is much faster.

November 1, 2016, 10:29		#2
kirrer New Member Kevin Join Date: Oct 2012 Posts: 29 Rep Power: 13	From your source sim file, you can use that threshold to export a table of data (Specified Y+ HTC and temperature are usually preferred). Then, in the solid-only file you can create a Tabular Data Mapper to map data from the table to your target surface. Within the data mapper, expand Target Specifications > Surface > Proximity constraint. Enable this and set appropriately. Once it's enabled, it gives the option to set "alternate values" for cells that do not get mapped. I would recommend an HTC of 0 and temperature of 300K. Once this is defined, map it, then use the MappedSpecifiedY+HTC and Tref as the HTC and Tref boundary condition for the surface you are mapping it to. This is the most straightforward way that I see to do what you are asking. Just keep in mind that if your solid solution changes temperature (transient or different boundary conditions), the fluid temperature would also change, which may (or may not) have a significant effect on heat transfer. By decoupling the two, you could miss this effect. Eike likes this.

November 8, 2016, 04:42		#3
Eike Member Eike Join Date: Sep 2011 Posts: 40 Rep Power: 14	Thanks a lot! Your answer was VERY helpful :-) kirrer likes this.

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November 24, 2016, 11:42		#4
cwl Senior Member Chaotic Water Join Date: Jul 2012 Location: Elgrin Fau Posts: 435 Rep Power: 17	If i got you right - you want to make a computation of heat transfer in solid (which is slow) and not waste time on solving fluid dynamics part after fluid flow has reached it's steady state. In this case - you can select "Freeze Solver" for fluid (Pressure-Velocity) in Solver controls and thus only energy equations will be solved which is much faster.