Flow Boiling in Microscale at High Flowrates

Abstract

Boiling heat transfer is an important heat removal mechanism for cooling applications in micro scale and finds many applications. Many studies were conducted to shed light on boiling heat transfer in microchannels. They were concentrated on saturation boiling at low mass fluxes (G<1000 kg/m2s). With the enhancement in micro pumping capabilities, flow boiling could be performed at higher mass velocities so that high cooling rates (>1000 W/cm2) could be possibly attained. Due to the increasing trend in critical heat flux and suppression of boiling instabilities with increasing mass velocity flow boiling is becoming more and more attractive at higher mass velocities, where subcooled boiling conditions are expected at high mass velocities. With the shift from low to high flow rates, a transition in both boiling heat transfer (saturated boiling heat transfer to subcooling boiling heat transfer) and critical heat flux (dryout type critical heat flux to departure from nucleate boiling critical heat flux) from one mechanism to another is likely to occur. Few experimental studies are present in the literature related to this subject. In this paper, it is aimed at addressing to the lack of information about boiling heat transfer at high flow rates and presenting experimental data and results related to boiling heat transfer and Critical Heat Flux (CHF) at high flowrates. New emerging technologies resulting in local heating such as nano-scale plasmonic applications and near field radiative energy exchange between objects could greatly benefit from boiling heat transfer at high flow rates in micro scale.