Enhanced Thermal Efficiency of Solar Air Heaters Using Porous Material: An Experimental Approach

Abstract

This study presents a detailed experimental investigation into the energy and exergy efficiencies of a double-pass solar air heater (SAH) augmented with porous materials. The primary objective was to assess the impact of integrating steel-based hollow square porous elements, featuring porosities of 0.98 and 0.99, on the thermodynamic performance of the SAH under tropical environmental conditions. A prototype SAH with dimensions of 0.75 m × 1.85 m × 0.25 m was developed and evaluated based on empirical data encompassing solar irradiance, air inlet and outlet temperatures, and mass flow rate. The results demonstrate a significant improvement in both energy and exergy efficiencies with the incorporation of porous materials. Notably, the configuration with 0.98 porosity yielded superior results, with energy efficiencies ranging from 6.19% to 9.01% and a peak exergy efficiency of 0.26%. In comparison, the reference system without porous material exhibited lower average energy and exergy efficiencies of 4.98% and 0.11%, respectively. Furthermore, the porous media contributed to enhanced thermal inertia, leading to improved heat retention and a more stable outlet temperature profile under fluctuating solar irradiance. These findings underscore the thermodynamic advantages of utilizing high-porosity materials within a double-pass SAH, emphasizing their potential for efficient thermal energy conversion in agricultural and industrial drying applications, particularly in regions with high solar potential.