Numerical analysis of non-regular and regular metal foam performance in heat transfer enhancing applications

The energy transition aims to implement strategies that enhance the utilisation of existing energy resources and improve the efficiency of high-energy demand processes, thereby reducing polluting emissions into the environment. The heat can be transferred with heat exchangers for direct heat usage; as more heat is transferred, the overall process energy efficiency increases. Several alternatives have been considered to increase the amount of heat recovered or transferred, including modifications in heat exchanger configurations to improve their effectiveness. As expected, an increase in the heat exchanger transfer area is desired, accompanied by a corresponding increase in pressure drop. In this sense, metal foams offer several advantages for developing heat-recovery systems: they have a low weight compared to the base material, exhibit good transport properties that enhance thermal energy absorption and transfer, and are associated with low-pressure losses due to their relatively high permeability. This work presents a thermohydraulic assessment of a heat transfer-enhancing appliance based on two types of open-cell metallic foam configurations: one non-regular structure foam (i.e., with random porosity distributions) and one regular-structured foam. A numerical assessment based on a Computational Fluid Dynamics approach is followed to analyse the thermohydraulic performance of both configurations. A comparison is made between two traditional geometries (i.e., a channel with non-heat-enhancing structures and a channel with a pin–fin pattern) to evaluate the increase in heat transfer and the pressure drop of the fluid as it passes through each configuration. The study found that the Nusselt number for regular foams stands out, ranging from 2.2 to 20.1, while maintaining lower friction factors (below 4.2) compared to other configurations. This confirms their superior thermal–hydraulic performance. Specifically, using a regular structured foam increases heat exchange by 94 % (27 % more than a non-regular foam) compared to an empty channel, with a pressure drop increase of 97.5 %, which is 2 % lower than that of a non-regular foam.