[marcusaurelius]

I am trying to simulate 2D conjugate heat transfer over a finned surface. The simulation works fine and shows some results as shown in Figure 1, which is temperature profile.

But, the problem is that the wall temperature keeps rising even after simulating it for 60 seconds of time (transient) as shown Figure 2.

I expect the wall temperature to reach some pseuso-steady state condition (imaginary plot is shown in Figure 3). But it does not reach that stage.

I have made mesh really small (having minimum cell size = 0.00005 m) and time step of 0.00005 s, which are the smaller values than what I see in literature. So, I think mesh or time step is not the problem. Also I use second order schemes. I tried all SIMPLE, PISO and coupled. and all does not show the desired result (Temp still keeps rising)

I have also seen similar problem with other software as well. I am sure I have been doing something fundamental mistake here. What is it?