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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?)