Convective heat transfer correlations for Triply Periodic Minimal Surfaces based heat exchangers

Lattice structures based on Triply Periodic Minimal Surfaces (TPMS) have been extensively studied in the field of heat exchange due to the advantages they can offer in terms of increased heat exchange area and enhanced convective phenomena, thanks to their intricate geometry. Numerous studies have been conducted on fluid motion within these structures, confirming that Computational Fluid Dynamics (CFD) simulations can accurately replicate their thermo-fluid dynamic behavior. However, such simulations are computationally expensive and may be difficult to integrate in larger models of the whole system. Traditionally, heat exchanger design relies on convective heat transfer coefficient correlations based on non -dimensional groups, especially when dealing with turbulent flow. This study proposes a single correlation, based on the results of a series of CFD simulations, to calculate the convective heat transfer coefficient for various fluids and different TPMS topologies and geometries. This is achieved through a careful selection of characteristic lengths for the various non -dimensional groups considered. Within an acceptance range of +/- 20%, the predictive capability of the correlation is proved valid for three distinct TPMS topologies: Gyroid, Schwarz -Primitive, and SchwarzDiamond. It applies across a porosity range of 70% to 90%, considering various unit cell lengths and different fluids. Furthermore, the study presents the effect of viscous heating at high Reynolds numbers on the different topologies and compares the proposed correlation with existing ones.