Development of subcooled wall boiling model considering bubble sliding in narrow rectangular channel

Abstract

Boiling two-phase flow simulation by two-fluid framework with interfacial interaction models has been successfully practiced in recent decades, and yet the model shows inability in simulating boiling two-phase flow in narrow rectangular channels, which are extensively existed in plate-type heat exchangers. This paper focused on the development of wall boiling model, which specifically considered the influence of bubble sliding in the description of wall boiling phenomena. The developed model describes the bubble behavior in nucleate boiling phase as the following sequences: nucleating, growing, detaching from nucleation site, sliding along the heated surface and then lifting off to the main flow. The sliding behavior was modeled according to the former experimental observation and measurement in the literatures. The departure and lift-off diameters were predicted by semi-mechanistic force-balance models. The developed model was implemented into CFD code and was applied to simulate several experimental subcooled boiling cases in a narrow rectangular channel. Results show that the developed model predicted wall temperature better against test data than the default RPI model, which proved the feasibility and suitability of present model in these cases. The evaporation heat flux calculated by developed model takes up less fraction, which accounts for the majority in RPI model.