Experimental and numerical study of flow boiling heat transfer characteristics in rectangular groove-wall microchannels

Abstract

Flow boiling in microchannels shows high potential to cope with the high power density dissipation for electronic devices. However, it is a challenge to promote the heat transfer performance, particularly temperature oscillations and critical heat flux (CHF) due to the two-phase flow instability. Here, we have made a comprehensively comparison studies on the temperature oscillation, the bubble nucleation, the flow pattern of the groove-wall microchannels and plain-wall microchannels via experimental and numerical methods simultaneously. The experimental results show that the groove-wall microchannel achieves better heat transfer performance. which were conducted at inlet subcooling of 25 °C, effective heat fluxes of 1.82–70.83 W·m−2, and mass fluxes of 819.4–3493.1 kg·m−2·s−1. The groove-wall structure can enhance the CHF by 31.3 % at mass flow rate of 819.4 kg·m−2·s−1 comparing that of plain-wall structure. The whole process of the growth movement of bubbles in the grooved area were obtained by a three-dimensional, transient numerical model using Volume of Fluid (VOF) method, which shows that the groove-wall structure can advance the incipience of boiling, and the grooved structure can help to keep the wall wet in the slug flow and annular flow area. In addition, compared with plain-wall structure, the temperature oscillation amplitude in the groove-wall structure is reduced by 77.2 % at mass flow rate of 819.4 kg·m−2·s−1, which means the groove-wall structure plays good performance in preventing the counterflow and reduces the flow oscillation in the parallel channel. This work can deepen the understanding of flow boiling mechanism in rectangular groove-wall microchannel.