Efficient Flow Boiling in Wedge-Shaped Manifold Microchannels for High Heat Flux Chips Cooling

Abstract

The flow boiling experiments are conducted using HFE-7100 as coolant to investigate flow patterns, hydraulic characteristics and heat transfer performance in manifold microchannels with conventional manifolds and wedge-shaped manifolds. The wedge-shaped manifolds microchannels (WMMC) can promote the flow pattern to transform from churn flow to annular flow, and greatly improve the distribution uniformity of the vapor volume ratio along the outlet manifold, which leads to an increase in vapor transport efficiency of the heat transfer system. Benefiting from these advantages, wedge-shaped manifold microchannels combine lower flow pressure drop, higher boiling heat transfer coefficient and greater critical heat flux. Compared to conventional manifold microchannels, the pressure drops of wedge-shaped manifold microchannels are reduced by 17.4% - 29%, the heat transfer coefficients are increased by 6.6%-18.5%, and the critical heat fluxes are increased by 11.6%-28%. Flow oscillations in WMMC can be triggered by the shift in flow pattern and the change in inlet state conditions. The combination of expanding the microchannel width and reducing the inlet subcooling significantly improve the two-phase flow instability while reducing the flow pressure drop. In practice, if the thermal power of heat sink and chip temperature meet the thermal management requirements, it is recommended to choose the wedge-shaped manifold microchannel with wider channels and lower inlet subcooling in preference.

Keywords: wedge-shaped manifold, manifold microchannel, flow boiling, visualization, flow pattern