Local, transient heat transfer measurements for flow boiling in a microchannel with a pin fin

•Local, transient flow boiling in a microchannel with a pin fin was experimentally studied.•The temperature measurements were synchronized with high-speed images to analyze boiling event.•Local heat transfer coefficient was calculated and compared with available models in the literature. Flow boiling in a microchannel with a pin fin was experimentally studied. Micro resistance temperature detectors (RTD) array was integrated inside a microchannel to enable local transient temperature measurement. The temperature measurements were synchronized with high-speed images to analyze boiling event and the corresponding transient temperature characteristics. Three distinct two-phase flow regimes were observed: bubbly flow, slug flow, and attached vapor cavity. Cyclic temperature fluctuations were observed during slug flow and it was related to local periodic vapor slug activities. In a single cycle, three distinct stages were observed: liquid wetting, film evaporation, and local dry out. These three processes were decomposed to calculate local heat transfer coefficient based on the experimental observation, as hx,y=τlhl+τfilmhfilm+τvhv and the result was compared with available models in the literature.