Heat transfer characteristics and flow visualization during flow boiling of acetone in semi-open multi-microchannels

Experimental results of flow boiling characteristics and flow patterns with acetone in two different microchannel heat sinks are presented in this paper. A semi-open microchannel heat sink and a straight microchannel heat sink with 19 parallel microchannels each were designed and tested. The semi-open microchannels have a channel width of 0.8 mm, fin width of 0.4 mm, and pedestal height of 0.2 mm and the straight microchannels have a rectangular cross section of 0.8 mm × 1 mm. The experimental heat fluxes ranged from 0 to 90 kW/m2, vapor quality ranged from 0.05 to 0.5, mass fluxes ranged from 4.34 to 15.62 kg/m2·s and the inlet temperatures were 20 and 30°C, respectively. Compared to those in the straight microchannels, flow boiling heat transfer coefficients can be improved by up to 36.2%. Furthermore, flow patterns were observed with a speed video camera. The flow boiling heat transfer mechanisms are analyzed according to the observed flow patterns