Experimental and Numerical Investigations of an Active Solar Air Heater: Energy and Exergy Analysis and Optimization to Increase the Efficiency

Abstract

Solar air heaters (SAHs) are simple and low-cost devices for harnessing renewable energy, but their practical application is often limited by low thermal and exergy efficiencies. Since exergy represents the useful portion of energy that can be converted into work, enhancing exergy effectiveness is essential for improving the overall performance of SAHs and advancing their role in sustainable heating technologies. This study investigated the optimization of exergy effectiveness by simultaneously considering geometrical parameters and operating conditions, thereby addressing limitations in earlier studies that typically focused on isolated factors. The novelty of this work lies in the integration of optimization, mathematical modeling, and experimental validation within a single framework. Unlike previous research, which often analyzed thermal and optical aspects separately, this study developed a comprehensive model that couples both behaviors, enabling a more rigorous and accurate assessment of SAH performance. Using MATLAB-based optimization, the maximum exergy efficiency was estimated at 7.315 %. Experimental tests were performed on two different days with discharge rates of 0.013 kg/s and 0.016 kg/s. The results show that optimum efficiencies occurred around 2:00 PM, with measured peak values of 2.245 % and 2.070 %, respectively. Additionally, linear regression equations were derived for both exergy and energy efficiency, offering practical correlations for design and analysis. Comparison with earlier studies confirmed the reliability of the proposed approach while also demonstrating its potential to guide the design of more effective and energy-efficient solar air heaters.