Geometry-metrics-dependent flow boiling characteristics in rectangular microchannels

Microchannel flow boiling has been regarded as one of the most effective ways to remove high heat flux. The microchannel geometry plays a pivotal role in the flow boiling characteristics while its relevance with the flow boiling has not been quantitatively finalized yet. In this work, we designed three sets of microchannels of various widths to probe the geometry-metrics-dependent flow boiling heat transfer. It has been found that the flow patterns differed by the microchannel widths, and so did the average heat transfer coefficient (HTC) and critical heat flux (CHF). Particularly, the narrow microchannel of 50 mu m in width was highly susceptible to triggering the CHF due to the in-channel confinement of the bubble. The flow instability was found with less dependence on the microchannels but with strong relevance to the mass flux. Finally, we tailed a correlation by including the geometry metrics of the microchannel to enable more versatile and accurate CHF estimates with a small deviation of 11.2 %. The present study contributes to valuable experimental trials to probe the geometric effect of microchannels and further sheds light on geometry-dependent flow boiling characteristics.