A numerical study of subcooled flow boiling in a manifold microchannel heat sink with varying inlet-to-outlet width ratio

Abstract

The manifold microchannel heat sink receives an increasing number of attention lately due to its high heat flux dissipation. Numerical investigation of boiling phenomena in manifold microchannel (MMC) heat sinks remains a challenge due to the complexity of fluid route and the limitation of numerical accuracy. In this study, a computational fluid dynamics (CFD) approach including subcooled two-phase flow boiling process and conjugate heat transfer effect is performed using a MMC unit cell model. Different from steady-state single phase prediction in MMC heat sink, this type of modeling allows for the transient simulation for two-phase interface evolution during the boiling process. Two validation cases are conducted to validate the heat transfer phenomenon among three phases. Besides, this model is used for the assessment of the manifold dimensions in terms of inlet and outlet widths at the mass flux of 1300 kg/m2·s. Even though the geometric sizes of microchannels (15 μm × 150 μm) modeled have been fixed, results indicate that manifold ratio and base heat flux have strong effects on thermal resistance and pressure drop. With different manifold ratios, about 43.3% decrease of pressure drop can be caused at the base heat flux of 400 W/cm2 while the thermal resistances remain nearly stable. Accordingly, we strongly recommend an manifold ratio ranging from 1 to 2 for the manifold divider to reduce the pressure loss of the MMC heat sink.