Exposed-area dependent forced convective heat transfer in periodic lattice structures

Abstract

This study presents numerical investigations of heat transfer and fluid flow in metal foams made of distinctive topologies. Two bio-inspired structures referred to as sponge and body-centered sponge (BCS), which exhibit identical thermophysical properties along three orthogonal axes, are proposed. Initially, the pore-scale computational model is validated, showing a deviation of less than 3 % when compared to the existing literature. Despite the intricate conductive pathways of the BCS structure, it is found to be a highly promising porous material as a heat exchanger, exhibiting the highest Nusselt number (twice as much as in cubic structures in water flow), friction factor (4.7 times as that in cubic structures in water flow), and performance evaluation criterion (PEC) (1.2 times as that in cubic structures in water flow). In addition, it is concluded that the large exposed area of fluid-foam walls and the high tortuosity of the BCS structure significantly enhance the Nusselt number. This complexity increases the frequency of flow deflection and stagnation, contributing to improved heat transfer performance. Finally, empirical equations for the Nusselt number and friction factor as a function of the unified exposed area parameter, Reynolds number, and Prandtl number have been developed with acceptable precision, accompanying with the R-squared value higher than 0.97.