boundary conditions in Ansys CFX (heatsource)

suitup · June 23, 2009, 10:21

Hello usercommunity,

I ve a little question about Ansys CFX 11, maybe you can help me.
I want to creat a heatsource by heatflow/flux on one side of an solid like the boundary condition heatflow in Ansys WB 11. How would be the best way to solve the problem?

My idea is to create a "boundary condition" and then selecting "wall" in the basic options and so on. The problem is that I am a little confused by the "Boundary Details"- and "Source" -options, there u can intergrate Heat flux twice.

If you can help me or can tell me another possibility to creat it, I would be very thankful.

Best regards.

ckleanth · June 23, 2009, 13:00

I'm not sure what you mean "in Ansys WB 11" but cfx either runnning in workbench or not is exacly the same.

anyway once you select a thermal model in a simulation you need to apply a boundary heat condition. a heat source in many ways is similar to a point source apart that can be applied to the whole domain (or using cel you can fix the source location somehwere in your domain) and is applied via a subdomain. if you have multifluid (multiphase) the difference between a phase heat source and a bulk heat source is that the phase heat source is multiplied by the volume fraction of the fluid

suitup · June 29, 2009, 09:53

Thank you for answering.

"Like Wb 11" i ment that i can define a boundary condition on a single layer. I ve attached a picture, so maybe it will be more understandable.

If i use subdomains and point source, i would just be able to selecte the whole solide or i ve just a point source put I would like to have a layer 50x50mm.

ckleanth · June 29, 2009, 10:59

what you want to model? if its the heat transfer between the fins and surrounding air then the easiest thing for you is to use a wall boundary condition with heat flux (or any other heat source)

btw from your picture i dont see the air domain so either you hid that or you forgot something

suitup · June 29, 2009, 11:10

no i just want to pump some heatpower into the heat sink by a heatsource over a layer on the bottom side, which replaces the chip or the PCB where the heat normally comes from.

Yeah i know that there is no air domain, thats just a pic of the simple WB11 simulation, it creates some boundary layer instead of creating a whole domain , thats why i want to simulate the heatsink with CFX, you know

Sorry for my bad explanation.

June 23, 2009, 10:21	boundary conditions in Ansys CFX (heatsource)	#1
suitup Member Join Date: Jun 2009 Location: Germany Posts: 38 Rep Power: 17	Hello usercommunity, I ve a little question about Ansys CFX 11, maybe you can help me. I want to creat a heatsource by heatflow/flux on one side of an solid like the boundary condition heatflow in Ansys WB 11. How would be the best way to solve the problem? My idea is to create a "boundary condition" and then selecting "wall" in the basic options and so on. The problem is that I am a little confused by the "Boundary Details"- and "Source" -options, there u can intergrate Heat flux twice. If you can help me or can tell me another possibility to creat it, I would be very thankful. Best regards.

June 23, 2009, 13:00		#2
ckleanth Senior Member George Join Date: Mar 2009 Location: Birmingham, UK Posts: 257 Rep Power: 18	I'm not sure what you mean "in Ansys WB 11" but cfx either runnning in workbench or not is exacly the same. anyway once you select a thermal model in a simulation you need to apply a boundary heat condition. a heat source in many ways is similar to a point source apart that can be applied to the whole domain (or using cel you can fix the source location somehwere in your domain) and is applied via a subdomain. if you have multifluid (multiphase) the difference between a phase heat source and a bulk heat source is that the phase heat source is multiplied by the volume fraction of the fluid __________________ Top 4 tips 1. Knowledge is everything and Ignorance is dangerous. 2. Understand your limitations and try to eliminate them. 3. Get yerself a bike and hoon the chuffer. You will soon learn why dogs like to hang their heads out the car window. 4. Please before asking any questions on how to run simulations in CFX, go though all the tutorials

June 29, 2009, 10:59		#4
ckleanth Senior Member George Join Date: Mar 2009 Location: Birmingham, UK Posts: 257 Rep Power: 18	what you want to model? if its the heat transfer between the fins and surrounding air then the easiest thing for you is to use a wall boundary condition with heat flux (or any other heat source) btw from your picture i dont see the air domain so either you hid that or you forgot something __________________ Top 4 tips 1. Knowledge is everything and Ignorance is dangerous. 2. Understand your limitations and try to eliminate them. 3. Get yerself a bike and hoon the chuffer. You will soon learn why dogs like to hang their heads out the car window. 4. Please before asking any questions on how to run simulations in CFX, go though all the tutorials

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June 29, 2009, 09:53		#3
suitup Member Join Date: Jun 2009 Location: Germany Posts: 38 Rep Power: 17	Thank you for answering. "Like Wb 11" i ment that i can define a boundary condition on a single layer. I ve attached a picture, so maybe it will be more understandable. If i use subdomains and point source, i would just be able to selecte the whole solide or i ve just a point source put I would like to have a layer 50x50mm.

June 29, 2009, 11:10		#5
suitup Member Join Date: Jun 2009 Location: Germany Posts: 38 Rep Power: 17	no i just want to pump some heatpower into the heat sink by a heatsource over a layer on the bottom side, which replaces the chip or the PCB where the heat normally comes from. Yeah i know that there is no air domain, thats just a pic of the simple WB11 simulation, it creates some boundary layer instead of creating a whole domain , thats why i want to simulate the heatsink with CFX, you know Sorry for my bad explanation.