Experimental investigation of flow boiling characteristics in rectangular microchannels

Although boiling flow in microchannels has high performance potential in terms of heat transfer, flow instabilities, pressure fluctuations and high pressure drop during the boiling process are one of the major obstacles to the industrial expansion of microchannels. The small size of the channel prevents the growth of the bubbles in the channel and causes the formation of elongated bubbles limited by the channel dimensions in the flow direction. This significantly changes the bubble formation dynamics during flow boiling, flow regimes, heat transfer characteristics and pressure drop. In this study, the effects of channel height on the boiling flow heat transfer and pressure drop characteristics of microchannel heat sinks were investigated experimentally. In addition to the channel height (H = 300 µm and H = 450 µm), the effects of different heat flux and mass fluxes on the bubble formation dynamics, heat transfer and pressure drop in the boiling flow were investigated using a micro PIV system.