Discussion Forum

Hi,

I've used Comsol 3.5a for one year and recently switched to v4.1 to catch up the trend. My problem is as follows:

With 3.5a, I'm using the "General Heat Transfer" from "Heat Transfer Module" to simulate the stationary heat transfer of water in a group of microchannels and the surrounding solid silicon parts. It does not need to solve fluid flow equations as I assign velocities to each fluid domain and the solver only deal with the thermal aspect.

Now, I'm trying to build and solve the model in version 4.1, preparing for the next step of my project. Unfortunately I didn't find the same "General Heat Transfer", but instead "Heat Transfer in Fluid". Seems that this module can deal with fluid domain & solid domain at the same time, and still, I can assign velocities to fluid domains and leave only thermal aspect to solve. Then, problem came out that the temperature field I got is quite different from the original one in v3.5a. Difference is around 30% and definitely it's not working as I thought.

Up to now I didn't find any mistake in things as domain settings, mesh or solver settings. I wish I could find some though. However, I'm curious about the boundary setting at channel inlet where I want to assign an inlet temperature. Should I simply use "Temperature" or "Open boundary"? I really appreciate if someone could help me figure it out.