Comparative analytical study of thermal and thermo-hydraulic performance in solar air heaters with fins, baffles, porous matrix, and internal recycling

Abstract

This paper presents a comparative analytical investigation of five distinct configurations of single-pass flat plate solar air heaters (SAHs), incorporating fins, baffles, porous matrix, and internal air recycling. A steady-state, one-dimensional mathematical model was developed and solved analytically to evaluate both thermal and thermo-hydraulic performance under various mass flow rates and reflux ratios. The results indicate that using a porous matrix alone results in approximately 14% lower thermal efficiency compared to configurations with fins and baffles. Placing the matrix beneath the absorber plate improved thermal efficiency by about 1.5%, but reduced thermo-hydraulic efficiency by roughly 2.5% compared to placing it above. While combining enhancement techniques does not always yield superior performance, the SAH equipped with fins and baffles alone achieved the highest thermal and thermo-hydraulic efficiencies across most conditions. Furthermore, increasing solar radiation intensity and air mass flow rate enhanced useful heat gain, although higher pressure losses caused the thermo-hydraulic efficiency to decline at elevated flow rates. Overall, this study provides valuable insights into the optimal integration of thermal enhancement methods in solar air heaters for improved energy performance.