Experimental investigations of flow boiling heat transfer performance in finned micro-channels

The flow boiling heat transfer and pressure drop in rectangular-finned micro-channels (i.e. micro-channel with rectangular fins) were experimentally investigated at five different fin-heights. At three different mass fluxes and a range of heat fluxes, heat transfer coefficients and pressure drops in the micro-channels were measured. The flow patterns during the flow boiling process were visualized to estimate the flow regime transitions in the microchannels. The experimental results showed that the micro-channel with 500 mu m height fins (i.e. tip clearance = 100 mu m) performs the highest heat transfer and shows the highest resistance to flow boiling instability among the studied cases. Compared to the smooth micro-channel, the averaged heat transfer coefficient in the microchannel with 500 mu m height fins has been improved by up to 133.9 % at the same wall temperature. Compared to the micro-channel with 600 mu m height fins (i.e. tip clearance = 0 mu m), the averaged heat transfer coefficient in the micro-channel with 500 mu m height fins has been improved by up to 45.8 %. At the initial point of flow instability, the micro-channel with 500 mu m height fins has the highest pressure drop fluctuation frequency, the highest surface wetting frequency, and the lowest pressure drop variation coefficient among the studied cases. However, the micro-channel with 600 mu m height fins has the lowest pressure drop fluctuation frequency and highest pressure drop variation coefficient, hence experiencing the longest dry-out process among the studied cases.