Comprehensive analysis of forced convection heat transfer enhanced by metal foam with pore density gradient structure

Metal foam, characterized by its large specific surface area, remarkable thermal and mechanical properties, is often used for heat dissipation in solar panels and solar energy storage systems. To address the pressure drop associated with the application of metal foam, eight foam metal composite structures with different pore gradient structures were developed. This study used computational fluid dynamics to analyze the heat transfer performance of structures with identical porosity but varying gradients. Results showed that gradient structures significantly reduce flow resistance. When high porosity metal foam occupies 20 %–80 % of the heat exchange section, the average pressure drop decreases by 17.2 %, 13.0 %, 8.7 %, and 4.7 % compared to uniform high porosity metal foam. The optimal configuration is 20 % low porosity and 80 % high porosity, with airflow performing better in the negative gradient direction. Practically, combining 10PPI and 20PPI allows for choosing either 20 % low porosity with 80 % high porosity or 40 % low porosity with 60 % high porosity. This study may offer a novel approach for heat exchange in solar energy applications.