Analysis , sizing and manufacturing of an indirect circulation solar air collector for drying agri – food products

Abstract

This work presents an experimental study comparing two indirect forced-convection solar air collectors designed for agricultural food drying: a conventional flat-plate solar collector (PSC) and an innovative solar collector equipped with flexible aluminum tubes (SCT), developed to enhance heat transfer. Experimental tests were conducted at the ETAP Laboratory of the University of Tlemcen under various solar radiation levels and airflow rates. The results showed that the SCT outperformed the PSC, providing an average air temperature increase of 2.30 °C and a 5.98% higher thermal efficiency. The collector was subsequently coupled with a drying chamber to form a complete indirect forced-convection solar drying system. Experimental investigations were carried out under real climatic conditions at the University of Tlemcen during June 2026 for both configurations (PSC and SCT). The experimental results confirmed the reliability of the system: the SCT achieved an outlet air temperature of 71.3 °C, compared with 54.8 °C for the PSC, corresponding to a temperature gain of 16.5 °C, and reached a maximum thermal efficiency of 55.4%, whereas the PSC achieved 33.8%. These findings demonstrate that integrating flexible aluminum tubes into solar air collectors is a simple, cost-effective, and efficient solution for enhancing the thermal performance of solar air collectors and improving the overall efficiency of solar drying systems.