Combined effect of inlet restrictor and nanostructure on two-phase flow performance of parallel microchannel heat sinks

Abstract

In this study, the combined effect of nanostructure and inlet restrictor on reducing the instabilities during flow boiling in parallel microchannel heat sinks is investigated experimentally. Four types of microchannel heat sinks are considered; plain microchannel, microchannel with inlet restrictor, nanostructured microchannel, and nanostructured microchannel with inlet restrictor. Different flow regimes such as bubbly flow, slug flow, annular flow, and partial dry out are observed with the variation in applied heat flux and mass flux. The fluctuations in pressure, temperature, and mass flux are characterised in each regime. It is found that the fluctuations increase with power input, which is primarily due to backflow of vapour in the upstream direction of flow. The microchannel with inlet restrictor is more effective in reducing fluctuations and result in less surface temperature compared to the baseline case of plain microchannel without restrictor at the same mass flux. Moreover, if the nanostructured surface is added to the plain microchannel with inlet restrictor, the effectiveness in reducing fluctuations increases at higher heat flux and also produces less surface temperature compared to other types of microchannels.