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 comprehensively investigate flow patterns, hydraulic characteristics and heat transfer performance in manifold microchannels with conventional manifolds (CMMC) and wedge-shaped manifolds (WMMC). The wedge-shaped manifolds microchannels demonstrates superior performance by facilitating flow pattern transition from churn flow to annular flow, significantly improving vapor distribution uniformity along the outlet manifold, and enhancing vapor discharge efficiency. 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 CMMC, the pressure drops of WMMC are reduced by 17.4 % - 29 %, the heat transfer coefficients are increased by 12.4 % - 37.3 %, and the critical heat fluxes are increased by 11.6 % - 28 %. However, both manifold configurations experience flow instability due to intermittent dry-out on the microchannel walls at high heat fluxes. In WMMC, both flow pattern transitions and flow instability trigger volumetric flow rate oscillations, which can be effectively mitigated by reducing inlet subcooling. These findings provide valuable insights for optimizing two-phase manifold microchannel in applications.