Numerical investigation of flow pattern and heat transfer characteristics in manifold microchannel heat sink for two-phase flow

Faced with increasing power density and the miniaturization of electronic devices, microchannel heat sinks with flow boiling are considered to be one of the most promising thermal management solutions. Similar in structure to the circulatory system in the human body, Manifold Microchannel (MMC) heat sinks have been proven to provide superior heat transfer compared to traditional microchannels, with better temperature uniformity. However, there have been few studies investigating the flow patterns in MMC heat sinks, which play a crucial role in the heat transfer mechanism during flow boiling. In this study, we conducted experiments and numerical simulations of flow boiling in MMC heat sinks. High-speed flow visualizations and instrumental measurements were carried out, and the results were compared with simulated data to illustrate the effects of heat flux, mass flux, and inlet subcooling on flow patterns and heat transfer characteristics. Our findings validate the accuracy of both our experimental and numerical methods. We thoroughly investigated the characteristics of flow patterns in MMC heat sinks, which differ significantly from those observed in traditional microchannel heat sinks. Due to the presence of numerous "short path" microchannels divided by manifold dividers, nucleated and growing bubbles are not confined and elongated within the microchannels. Instead, the flow patterns mainly consist of bubbly flow within the microchannels and confined bubble and annular flows within the outlet manifold channels. The dominant heat transfer mechanism in the microchannels is nucleate boiling, which can be attributed to the presence of glass-based manifold dividers.