Investigation of flow distribution and effect of aspect ratio on critical heat flux in multiple parallel microchannel flow boiling

In this paper, an experimental study on the effect of the low aspect ratio of microchannel on the critical heat flux (CHF) during saturated flow boiling of water is presented. Multiple parallel silicon microchannels with different aspect ratios, hydraulic diameter, and number of channels in the range of 0.2-0.5, 154.0-184.8 mu m, and 3-9 respectively are fabricated, and the experiments are performed in the range of mass fluxes 24.1-806.5 kg m(-2) s(-1). It is found that the CHF is caused by the wall dryout near the microchannel exit. The effect of microchannel aspect ratio with the same hydraulic diameter on the CHF is found to be insignificant. Twenty-five CHF data points are obtained for microchannel flow boiling of water and are compared with the CHF predictive methods reported in the literature. A new CHF correlation is proposed, which predicts the measured CHF with the mean absolute deviation of 12.1%, which is substantially better than available CHF predictive methods. The findings from this study provide guidelines for designing multiple parallel microchannel heat sinks in two-phase flow for the thermal management of electronic equipment, spacecraft, satellites, energy conversion devices, and biomedical engineering.