Enhanced flow boiling in microchannels by self-sustained high frequency two-phase oscillations

Experimental study of flow boiling heat transfer in a microchannel array consisting of main channels connected to two auxiliary channels (each) was conducted. A microbubble-excited actuation mechanism, powered by high frequency vapor bubble growth and collapse, was established to create and sustain strong mixing in the microchannels. It was shown to significantly enhance flow boiling heat transfer in microchannels. Experimental studies were conducted at mass fluxes ranged from 150 to 480 kg/m2 s with de-ionized (DI) water as the working fluids. Compared with microchannels with inlet restrictors (IRs), the average two-phase heat transfer coefficient was improved by up to 149%. More importantly, a 71–90% reduction in pressure drop at moderate mass fluxes ranged from 400 to 1400 kg/m2 s was observed. Heat flux up to 552 W/cm2 at a mass flux of 480 kg/m2 s was demonstrated. Flow and heat transfer mechanisms were studied and discussed.