Subcooled flow boiling of water in a large aspect ratio microchannel

Abstract

Water flow boiling in large aspect ratio microchannels was experimentally investigated in a rectangular microchannel 300μm deep and 6mm wide; hence, the hydraulic diameter was 571μm and the aspect ratio was 20. The tests used mass fluxes of G=261–961kg/(m2s) and heat fluxes of q″=631–987kW/m2 with the combined effects on the flow boiling phenomena characterized by the Boiling number at an inlet temperature of 65°C. The results show the flow patterns and the heat transfer and pressure drop characteristics during flow boiling in the large aspect ratio microchannel. Sweeping flow with relatively high heat transfer rates was observed while the strengthening effect of the bubble confinement on the heat transfer did not occur during the subcooled flow boiling in the large aspect ratio microchannel. Nucleate boiling dominated the heat transfer with the regular pressure drop fluctuations detected during the sweeping flow and the churn flow.