[Mohsin1]

I need to model the dissipation of 180 kW of heat. I plan to simplify this from a 3D problem to a 2D analysis and define a heat flux boundary condition in Fluent.

My calculation for the original 3D case gives a heat flux of 2069 kW/m², which I found using the formula: 180 kW / (0.025 m * 3.48 m).

For the 2D model in ANSYS, I created the mesh by extruding the geometry by a single cell's thickness in the direction normal to the screen. I applied symmetry boundary conditions to the front and back faces.

I am unsure what value to use for the heat flux on the bottom face in this 2D simulation (also, should the heat flux be defined on the bottom face of 2d problem or bottom front edge?). I have attached a picture for reference. Any suggestions would be appreciated.

[MKuhn]

You can proceed in the same way as for the 3D model, that means define the inlet and outlet in the same way (not with symmetry). If you define under Physics --> Reference Values.. --> Length [m] = 3, you get your right value for the heat flux in W/m², as you can not define it in W/m in the boundary conditions, as it will be for the 2D modell.