How to model planar 2D heat source between 3D objects?

thermokopf · September 22, 2024, 03:02

Icepak has source objects which are planar 2D heat sources. You can sandwich them between 3D blocks. Useful for approximating transistor power dissipation.

My question is how are these 2D source objects handled?

E.g. a 2D heat source with 1 W of power… does 50% of heat go up and down? What is the heat split?

evcelica · September 24, 2024, 09:41

I realize after I typed my response, you are using icepack, I was thinking of CFX.
I think a lot of the concepts are still relevant though. The heating is likely applied evenly to both sides of the interface, but where the heat actually flows depends on where the cooling is taking place.

For CFX: You can use a source term on one or both sides of the interface. It will then apply the heat to the side you specify. Some of that heat can flow to the other side, depending on where cooling is taking place. If you specified a thermal resistance at the interface less heat would go to the other side (depending on cooling). I would probably add half the heat to each side of the interface if you specified a large resistance there, otherwise, if there is no thermal resistance, adding it to either side should be very close to distributing it to both sides evenly, and where the heat actually goes depends on where cooling is taking place. Think of it as a 1D thermal resistance model with the thermal resistances in series.
You can run a simple test where you apply it fully to one side, then the other side and see the results don't change by much (if you have not specified a thermal resistance at that interface.)

September 22, 2024, 03:02	How to model planar 2D heat source between 3D objects?	#1
thermokopf New Member Xander Join Date: Oct 2023 Posts: 3 Rep Power: 3	Icepak has source objects which are planar 2D heat sources. You can sandwich them between 3D blocks. Useful for approximating transistor power dissipation. My question is how are these 2D source objects handled? E.g. a 2D heat source with 1 W of power… does 50% of heat go up and down? What is the heat split?

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September 24, 2024, 09:41		#2
evcelica Senior Member Erik Join Date: Feb 2011 Location: Earth (Land portion) Posts: 1,188 Rep Power: 23	I realize after I typed my response, you are using icepack, I was thinking of CFX. I think a lot of the concepts are still relevant though. The heating is likely applied evenly to both sides of the interface, but where the heat actually flows depends on where the cooling is taking place. For CFX: You can use a source term on one or both sides of the interface. It will then apply the heat to the side you specify. Some of that heat can flow to the other side, depending on where cooling is taking place. If you specified a thermal resistance at the interface less heat would go to the other side (depending on cooling). I would probably add half the heat to each side of the interface if you specified a large resistance there, otherwise, if there is no thermal resistance, adding it to either side should be very close to distributing it to both sides evenly, and where the heat actually goes depends on where cooling is taking place. Think of it as a 1D thermal resistance model with the thermal resistances in series. You can run a simple test where you apply it fully to one side, then the other side and see the results don't change by much (if you have not specified a thermal resistance at that interface.)