Discussion Forum

Without seeing your model I suggest the following:

I guess you have two physics modules, heat transfer in solids and heat transfer in fluids. If the former has the temperature variable T1 and the latter T2, set in the former module temperature to T2 on the boundary, and in the latter T1.

Wish this helps Lasse

Hi ! I am currently doing a two dimensional simulation of a reactor. Chemical reaction take place in this reactor. The reactor is a cylinder reactor. I set up a two-dimensional axial symmetry model to simulate this process. In the core of the cylinder a cooling pipe run through the cylinder and water flow through the cooling pipe taking the heat away. I use heat transfer in porous media to simulate the process in the reactor, and laminar flow, heat transfer in fluid to simulate the heat transfer in the cooling water. Finally I use heat transfer in solid to simulate the heat transfer in the cooling pipe wall. However, I dont konw how to apply boundary conditions between the cooling pipe wall ,the reactor and the cooling water.I dont konw how to apply boundary conditions between the reactor and the cooling pipe wall, and boundary conditions between the cooling pipe wall and cooling water in order to make the heat transfer from the reactor to the cooling water. The model figure is attached. Could anyone tell me how to solve this problem? Thanks in advance!!

During my chem. eng. studies (decades ago) I learnt to use the heat flux boundary condition: Assume that the fluid temperature is T1 and in the pipe wall T2. Then the heat flux (Q) follows the cooling law

Q = ±k·(T1 - T2)

where k is the heat transfer coefficient. Its value can vary a lot depending on the convection and the materials involved. Typically they are in the range of 100...1000 W/m²K. You must choose plus or minus depending on the side of the boundary, i.e. in the fluid and the solid the signs are opposite.

Lasse

Thank you very much!!