I've noticed that when using the electronics cooling module add-in with Solidworks Flow Simulation the temperature rise from the junction to the board is much higher than what is predicted by a simple hand calculation Delta T = q * Rjb, where Rjb is the junction to board thermal resistance. This problem only seems to occur when I'm using a printed-circuit board, along with a two-resistor component, both defined in the electronics cooling module.
If I have the two-resistor component mounted to a highly conductive material instead of a defined printed-circuit board the problem goes away. That is the temperature rise from the junction to the board agrees well with Delta T = q * Rjb. I've been using Flotherm for 10+ years so I think I have some experience with what to expect with the junction to board temperature rise, and I've tried different scenarios to try and identify the problem.
Has anyone else seen this issue? Any help is greatly appreciated.