A New Empirical Model for Bubble Growth: Boiling in an Infinite Medium and on a Wall at High Superheat

Abstract

At high superheat bubble growth is rapid and the heat transfer is dominated by radial convection. This has been found, in the case of a droplet boiling within another liquid and in the case of a bubble growing on a heated wall, leading to similar bubble growth curves. Based on experiments conducted for the first case, an empirical model is developed for the prediction of bubble growth within the radial convection dominated regime (the RCD model), occurring only at high superheat (0.26<Ste<0.41). This model shows a dependence of R∼t1/3 equivalent to Nusselt number decreasing over time (Nu∼t1/3) as opposed to R∼t1/2 appearing in most other models, leading to a highly unlikely constant Nusselt number. The new model is shown to give accurate predictions for the first case and for the second case at medium-high superheat (0.19<Ste<0.30, experimental data taken from literature). A comparison of the RCD model to other models, shows a more consistent and accurate prediction. However, in the second case (nucleate boiling) the RCD model requires the foreknowledge of the departure diameter, for which a reliable model still is lacking.