Numerical investigation on conjugate heat transfer in octet-shape-based single unit cell thick metal foam

Abstract

Present study reports flow and thermal transport characteristics of metal-foam based on Octet-shaped unit cell (porosity ~ 0.97) for electronic cooling application with water as the working fluid. Conjugate simulations were carried out on a single cell thick lattice frame comprising of four consecutive connected unit cells in the streamwise direction. Simulations were performed for flow velocity range of 2–8 cm/s with the substrate subjected to a heat flux of 10 W/cm2, for two different solid-phases corresponding to solid-to-fluid thermal conductivity ratios (ks/kf) of 37 and 288. A control-volume-based energy balance method was adopted for calculation of global and cell-based convective heat transfer coefficient in the conjugate simulations, where the global heat transfer coefficient was ~ 2900 W/m2K for ks/kf~288 and ~ 2100 W/m2K for ks/kf~37, both for flow velocity of 8 cm/s. The cell-based heat transfer coefficient showed a sharp declining trend typical of developing flow. The interfacial heat transfer coefficient (hsf) on the fibers and the substrate-endwall was also obtained through separate simulations imposing constant heat flux and constant temperature boundary conditions on the walls. The averaged hsf on fiber walls and substrate-endwall was ~ 8700 W/m2K and ~ 2000 W/m2K, respectively, corresponding to average flow velocity of 8 cm/s.