Wall nucleation modeling in subcooled boiling flow

Abstract

The bubble departure characteristics are studied in flow boiling considering the available experimental data in the literature. The current bubble departure diameter and departure frequency models are reviewed and compared with the collected database, revealing the current modeling shortcomings in forced convective flows. Based on an energy balance approach at the heated surface, the important dimensionless groups are identified and correlated for the bubble departure diameter and departure frequency. These dimensionless groups are the Jakob number, Boiling number, density ratio, and Prandtl number. The bubble departure diameter data also suggests some effect of the flow geometry in mini-channels. The newly proposed semi-empirical models for the bubble departure diameter and departure frequency are shown based on the available database to be accurate to within ±22% and ±35% respectively. This work also identifies important future experimental considerations for the bubble departure characteristics including data at elevated pressures, larger Prandtl numbers, and around the boundary between mini and conventional channels.