Heat transfer boundary conditions

flusk123 · May 4, 2017, 02:21

Can someone explain the difference between the Heat Generation rate (option in Heat Flux and Temperature Wall boundary conditions) and the Energy source term(which we define in cell zone conditions)

Both have units W/m3

Secondly, which condition to apply if amount of heat transfer (Q, Watt) from a chip is known. Surrounding medium is air

LuckyTran · May 6, 2017, 18:39

The energy source term is a volumetric energy source applied to cells in the computational domain (at each cell).

The heat generation rate is applied as a surface boundary condition. In wall boundary conditions there is a wall thickness parameter (the default is 0). The heat generation rate you specify is distributed over this thickness.

So energy source applies to cells, heat generation rate applies to surface. So where is your heat generated? Inside the domain or outside? It depends on how you have setup your domain, i.e. is your chip meshed or is it just a surface that you model?

flusk123 · May 7, 2017, 04:30

Thank you for your reponse.In my case, chip is a solid zone which is meshed.

For now, I am using volumetric source term by calculating the energy source by dividing rate of heat tranfer (in watt) by volume of chip (m3).

My follow up question is:

As I see the boundary regions created by fluent for the chip is for a single wall which it shares with the room wall. For other 5 walls (of chip) contact region is created and they have shadow walls as well.

So for this single wall, if I use a temperature/heat flux boundary condition with heat generation rate with the chip thickness specified as wall thickness. Would it be the one and the same thing?

May 4, 2017, 02:21	Heat transfer boundary conditions	#1
flusk123 New Member Join Date: May 2017 Posts: 4 Rep Power: 9	Can someone explain the difference between the Heat Generation rate (option in Heat Flux and Temperature Wall boundary conditions) and the Energy source term(which we define in cell zone conditions) Both have units W/m3 Secondly, which condition to apply if amount of heat transfer (Q, Watt) from a chip is known. Surrounding medium is air dhioprithvi likes this.

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May 6, 2017, 18:39		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,761 Rep Power: 66	The energy source term is a volumetric energy source applied to cells in the computational domain (at each cell). The heat generation rate is applied as a surface boundary condition. In wall boundary conditions there is a wall thickness parameter (the default is 0). The heat generation rate you specify is distributed over this thickness. So energy source applies to cells, heat generation rate applies to surface. So where is your heat generated? Inside the domain or outside? It depends on how you have setup your domain, i.e. is your chip meshed or is it just a surface that you model?

May 7, 2017, 04:30		#3
flusk123 New Member Join Date: May 2017 Posts: 4 Rep Power: 9	Thank you for your reponse.In my case, chip is a solid zone which is meshed. For now, I am using volumetric source term by calculating the energy source by dividing rate of heat tranfer (in watt) by volume of chip (m3). My follow up question is: As I see the boundary regions created by fluent for the chip is for a single wall which it shares with the room wall. For other 5 walls (of chip) contact region is created and they have shadow walls as well. So for this single wall, if I use a temperature/heat flux boundary condition with heat generation rate with the chip thickness specified as wall thickness. Would it be the one and the same thing?