Favourably regulating two-phase flow regime of flow boiling HFE-7100 in microchannels using silicon nanowires.

ABSTRACT

High performance miniaturized electronic devices require enhanced, compact and reliable thermal management system. As an efficient compact space cooling technique, flow boiling in microchannels has recently gained wide acceptance. However, weak buoyancy effects and microgravity in avionics and numerous space systems operations hinder the performance of flow boiling microchannel thermal management system due to poor bubble departure capacity and unfavorable development of flow regimes. Here we report the flow boiling silicon nanowires (SiNWs) microchannels which can favorably regulate two-phase flow regimes by enhancing explosive boiling, minimizing bubble departure diameter, and smoothing flow regime transition. Extensive experimental investigations along with high speed visualizations are performed. The experiments are performed with the dielectric fluid HFE-7100 in a forced convection loop for wide range of heat and mass fluxes. High speed flow visualizations have been employed at up to 70 k frames per second (fps) to understand the boiling mechanism in terms of bubble dynamics, flow patterns, and flow regime developments for SiNWs microchannels. These studies show that SiNWs reduce intermittent flow regimes (slug/churn), improve rewetting and maintain thin liquid film at wall. Therefore, flow boiling in SiNW microchannels is promising to thermal management owing to its high heat transfer rate with low pressure drop and negligible microgravity sensitivity.