Air cooling system for an array of PCB's using an air-tunnel

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I only started working with COMSOL a month ago and had never simulated anything like this before. I set up a model where I have an array of 24 PCBs that I want to cool. Previously, I created a water-cooling system using a simplified form of heat pipes.

To simplify the simulation, I reduced the setup to 4 PCBs. These PCBs are 6-layer PCBs (i.e., 6 layers of copper with epoxy (FR4) in between). There are 4 heat sources on each PCB, with power ratings of 3×1.2 W + 1×0.66 W.

For the physics, I am using:

Heat Transfer in Solids and Fluids Laminar Flow

To simulate air cooling, I created an air tunnel surrounding the entire setup. In the Heat Transfer module, I defined an inflow with 20°C and an outflow. In the Laminar Flow module, I set up an inlet (average velocity = 20 m/s) and an outlet (pressure = 1 atm).

However, I keep encountering an error. For a test, I created a simulation with just a sphere surrounded by the air tunnel (much simpler than a series of thin layers), but I still get an error.

I now suspect that I might be doing something wrong when inserting a solid object into a gas (air). Can anyone help me with this issue? (Do you have experience with this?)


4 Replies Last Post 18 dic 2024, 03:40 GMT-5
Jeff Hiller COMSOL Employee

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Posted: 2 months ago 17 dic 2024, 08:32 GMT-5

Hello Andi,

At 20m/s, are you sure your flow is laminar?

Jeff

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Jeff Hiller
Hello Andi, At 20m/s, are you sure your flow is laminar? Jeff

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Posted: 2 months ago 17 dic 2024, 09:09 GMT-5

Hello Jeff,

thank you for your reply. Propably not. I changed it to turbulent flow. But I still get an error message.

First I would like to ask how to solve this problem typically. From the point before I set a geometry of an air tunnel.

Lets say all the geometries and everything in the physics heat transfer in solid and liquids is correct. How would I procede onwards with building the air tunnel and the turbulent flow?

Do I have to cut a copy of my PCB assembly from the air tunnel? Is it enough just to set Inlet (with 20m/s) and Outlet (with pressure 1atm) at the ends of the air tunnel? Should I include the PCB's in the Turbulent flow or not? Should I use a different Flow Physics?

Best regards, Andi

Hello Jeff, thank you for your reply. Propably not. I changed it to turbulent flow. But I still get an error message. First I would like to ask how to solve this problem typically. From the point before I set a geometry of an air tunnel. Lets say all the geometries and everything in the physics heat transfer in solid and liquids is correct. How would I procede onwards with building the air tunnel and the turbulent flow? Do I have to cut a copy of my PCB assembly from the air tunnel? Is it enough just to set Inlet (with 20m/s) and Outlet (with pressure 1atm) at the ends of the air tunnel? Should I include the PCB's in the Turbulent flow or not? Should I use a different Flow Physics? Best regards, Andi

Jeff Hiller COMSOL Employee

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Posted: 2 months ago 17 dic 2024, 09:23 GMT-5
Updated: 2 months ago 17 dic 2024, 15:23 GMT-5

Hi Andi,

Here are some models of forced air cooling to help you get started.

Best,

Jeff

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Jeff Hiller
Hi Andi, Here are some models of [forced air cooling](https://www.comsol.com/models?q=forced%20air%20cooling) to help you get started. Best, Jeff

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Posted: 2 months ago 18 dic 2024, 03:40 GMT-5

Hello Jeff,

thank you found a few good examples there.

Best, Andi

Hello Jeff, thank you found a few good examples there. Best, Andi

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