Numerical Study on Subcooled Flow Boiling in Narrow Rectangular Channel Based on OpenFOAM

Abstract

As for the impacts from the scale effect of narrow rectangular channel, a wall nucleation model applying to the subcooled flow boiling in these channels was developed and verified, based on experimental data over such boiling in this study. Then it was transplanted into a two-fluid model through the OpenFOAM platform after correction, to construct a two-fluid solver applying to the numerical simulation of the subcooled flow boiling in narrow rectangular channel. Meanwhile, on this basis, we carried out the study on the impact of inlet subcooling, inlet mass flow rate and wall heating power on the heat transfer mechanism of wall boiling, while finding that with the increase of inlet subcooling and inlet mass flow rate, the ratio of single-phase convective heat flux gradually rose, in contrast to that of evaporate heat flux and quenching heat flux. The reason behind this was the increase of the above two factors reduced wall superheat, as well as bubble diameter and bubble influence area. However, the impact of heat flux for wall heating was more complicated. With the increase of wall heat flux, the convective heat flux increased first and then decreased, while the evaporate heat flux and quenching heat flux gradually rose, as do the wall fluid heat-transfer temperature difference and the bubble influence area, which respectively facilitated single-phase convective heat transfer and restricted the proportion of single-phase heat transfer. The competition of these two led to the increase and the ensued decrease of convective heat flux.

Keywords: narrow rectangular channel, subcooled flow boiling, two-fluid model, wall nucleation model, numerical simulation