Large eddy simulations of kagome and body centered cubic lattice cells

Abstract

As advanced manufacturing methodologies such as additive manufacturing become accessible and cost effective, more complex and tailored internal cooling schemes can be achieved. One family of cooling geometries that has recently garnered interest within the heat transfer community are lattice structures. These structures offer enhanced mixing and large surface area-to-volume ratios, but their application in advanced heat exchangers is in relative infancy. This study explored the performance of two types of lattice unit cells, specifically Kagome and body centered cubic (BCC), by identifying the flow development and unsteady characteristics using large eddy simulations (LES) at a Reynolds number of 20,000. Simulation results agree well with experimental data, and differences between the two methods was found to be a function of the as-printed quality of the experimental geometry. Results indicate that both lattices feature spatial periodicity in the local Nusselt number and friction factor, due to the changes in flow area and flow interactions in the wake of each lattice strut. LES results show that the flow through the BCC lattice became fully developed, both hydrodynamically and thermally, with fewer unit cells than through the Kagome. In the entry region, the flow in the Kagome lattice became biased towards one side of the channel due to local wakes and interactions with the lattice struts, resulting in a bias to the local heat transfer. The simulations also revealed that the instantaneous vortices shed from the BCC lattice struts interacted with the duct endwalls, pulling the boundary layer from the wall and enhancing heat transfer.