An analysis of incipient boiling superheat in alkali liquid metals

Studies on the incipient boiling superheat (IBS) in alkali liquid metals have revealed that many factors can have effects on IBS. However, existing results about the effects of most variables are inconsistent and even conflicting. It is possible that effects of many variables are only apparent and the complex results can be explained with several simple factors. Three basic variables, i.e. the effects of inert gas diffusion, oxide layer and dynamic process were involved in our model to show their effects on IBS. Analysis showed that the inert gas diffusion should be carefully considered because it may result in large variation of IBS in a short time. Existence of oxide layer could help reducing IBS by keeping large cavities un-wetted and enhancing nucleation contact angle. The effect of dynamic process on IBS which may cause apparent velocity and heat flux effects may be explained with the variation of apparent nucleation contact angle caused by interface speed, and a correlation with some empirical coefficients was proposed to describe its effect. To verify the model several sets of experimental data were carefully selected. Predictions considering these effects were compared with these experimental data and good agreements were gained.