Improvement of solar air heaters performance with PCM-filled baffles and storage bed

Abstract

Solar air heaters (SAHs) are popular solar energy collection systems due to their simple design and construction. However, conventional SAHs face limitations, including a small heat transfer surface area, high thermal resistance between the airflow and the heater, and reduced performance during nights or cloudy days. This study proposes a solution by incorporating both a PCM storage bed and optimized PCM-filled baffles in the SAH. Initially, a 3D transient numerical analysis is conducted to investigate the SAH with a storage bed and PCM-filled baffles. The numerical modeling employs the TEDM approach to identify the optimal geometries for the PCM-filled baffles. Subsequently, experimental tests are conducted based on the identified optimal conditions. The results reveal that the height of the baffles is the most influential parameter in determining the daily effective efficiency. The proposed SAH exhibits a daily effective efficiency approximately 57.9% higher than that of a SAH without PCM and 52.6% higher than that of a SAH with a PCM storage bed at Re=5000. Moreover, the proposed SAH outperforms baffles-less SAHs by prolonging the duration during which the outlet air is at least 5° warmer than the inlet by approximately 54%.