Hi Robert, I'm not intending on modeling boiling. Perhaps I should have the wall and initial condition at the same temperature. I'm trying to isolate the evaporation from the free surface so ideally the interface should drop as the liquid evaporates. You're right, with the way I have it set up with the surface at 200C & the initial at 100C, I should see vapor generating at the wall and bubbling up, but I don't see that either.