Investigation of fluid flow and heat transfer characteristics in a microchannel heat sink with double-layered staggered cavities

Abstract

This paper is focused on a numerical investigation of fluid flow and heat transfer characteristics in a microchannel heat sink (MCHS) with double-layered staggered cavities (MCHS-DLSC). The effects of both the expansion-to-contraction ratio (φ) and the height ratio (β) on the thermal performance are studied by numerical simulation. A comparison is performed between the MCHS-DLSC and the MCHS with straight channels (MCHS-SC). The comprehensive performance of the MCHS-DLSC is evaluated. The flow, temperature, and pressure fields are employed to discern the mechanism of heat transfer enhancement for the MCHS-DLSC. The results indicate that the Nusselt number (Nu) and friction factor (f) of the MCHS-DLSC are 1.03–1.85 and 1.37–1.41 times higher than those of the MCHS-SC, respectively. However, the thermal resistances of the MCHS-DLSCs are at most 25.9–33.8% less than that of the MCHS-SC. The Nu, f, and thermal enhancement factor (PEC) decrease with the increase of the φ, while the R increases as the φ increases. However, when the β = 0.5, the Nu, f, and PEC reach maximum values at fixed φ under the corresponding Reynolds number, but the R is the minimum value simultaneously. It is confirmed that the DLSC can strengthen the fluid mixing, interrupting, and redeveloping of thermal boundary layers under the action of the jet and throttling effects. Hence, the DLSC has effective heat transfer enhancement.