Energy buffer mechanism for heat transfer enhancement in grooved channel cooling with flow intermittency

Abstract

Driven by the ever-growing heat load in industrial applications such as fast charging electrical vehicle batteries and high-performance processors, advanced cooling technologies for efficient thermal management are urgently needed. This numerical work demonstrates the great potential of flow intermittency in grooved channels for thermal performance improvement at laminar condition, and aims to reveal the underlying mechanism that governs the heat transfer enhancement. The open-source computational fluid dynamics code OpenFOAM is employed to resolve the intermittent channel flow with triangular surface grooves. The time-averaged Reynolds number Re m = 100 and the Strouhal number St = 0.2 are maintained, while the close time ratio γ ranges from 0.1 to 0.9. The thermal performance improvement is attributed to the “energy buffer” mechanism by cavity vortices, which induces strong near-wall reverse flow and promotes effective mainstream-boundary flow mixing. The results indicate that the averaged surface Nusselt number consistently increases with the close time ratio and at γ = 0.9 reaches 1.9 times of the steady-flow value. Particularly the heat transfer performance inside grooves is remarkably improved by a maximum of 175%. This novel concept of synergizing flow intermittency and surface structure achieves notable heat transfer enhancement under constant coolant consumption, and shows ample design space for further optimization.