Thermohydraulic characterization of flow boiling in a nanostructured microchannel heat sink with vapor venting manifold

Capillarity due to textures on microchannel surfaces promotes thin-film evaporation to allow high heat dissipation in the annular flow boiling regime. However, the advantage of textures is not realized at moderate heat fluxes in the slug flow regime wherein rapid vapor generation due to improved nucleation increases temperature fluctuations. Here we investigate the combination of liquid supply and vapor-venting strategies with surface modifications to minimize temperature fluctuations in the slug flow regime. We perform experiments with plain wall (PWM) and nanostructured (NSM) microchannels to show that poor vapor venting with conventional horizontal-inlet and horizontal-outlet (HH) manifold design stimulates temperature fluctuations of approximate to +/- 5 degrees C , even at a nominal heat flux of approximate to 750 kW/m(2) . Conversely, a novel vertical-inlet and vertical-outlet (W) manifold design with jet impingement cooling at the inlet and enhanced vapor-suction at the outlet minimizes fluctuations. The W manifold when complemented with the intrinsic merits of NSM, reduces temperature fluctuations to within +/- 0.5 degrees C, up to a high heat flux of approximate to 1000 kW/m(2). These results suggest that surface modification techniques should be complimented with vapor venting strategies for heat transfer enhancement via flow stabilization in the slug flow regime. (C) 2018 Elsevier Ltd. All rights reserved.