Natural convection problem (CFX 11.0)

Willy

Hi, Im studying a case where I have a steel tube with a electrical resistance inside of it, which I´ve modeled as a heat source. The power dissipation on the tube is 200 W and is inserted in an ethanol volume at 0°C. I would like to check how the tube heats up my fuel volume and how the tube is being cooled by the ethanol. We have made some lab measurements and from them I know that the temperature at the surface of the tube should be around 130 °C. It was also verified that we have boiling, so I´m working with both ethanol and ethanol gas as working fluids, and modeling thermal phase change as well (boiling temperature was considered 120.7 °C). The problem is that the temperature at the surface of the glow plug does not reach the equilibrium and keeps raising (around 300 °C) together with both fluids temperatures. For that I imagine that no heat transfer through natural convection is happening... Anybody could please give some advise on what´s happening? Any advise would be welcome!!!