Mechanistic modelling of bubble growth in sodium pool boiling

Abstract

This work presents a mechanistic model to simulate the growth of a sodium bubble from nucleation to departure in sodium pool boiling. A previously developed and validated heat transfer sub-model is coupled to a force balance sub-model to predict the growth rate and departure radius of a sodium bubble. The model accounts for the change in the contact angle of a bubble as it grows, and the shrinkage of the bubble base prior to departure. The developed model is used to quantify and analyse the heat transfer from different regions, i.e. the microlayer, the macrolayer, the thermal boundary layer and the bulk liquid surrounding the bubble. In addition, bubble growth rate and departure radius are calculated for different values of wall superheat, rate of change of contact angle and bulk liquid temperature. It is found that the departure radius of a sodium bubble is on the order of a few centimetres and the wall superheat has a significant influence on the shape of a sodium bubble at departure.