Enhancing the Performance of an Indirect Solar Dryer Based on Baffle Geometry Optimization: An Experimental Study on Mint Drying Under Saharan Climate

ABSTRACT Solar drying provides an eco‐friendly and energy‐efficient alternative to traditional drying ‎methods, making it a practical choice for agriculture and food preservation in regions with high ‎solar availability. This paper describes research on an indirect solar drying (ISD) system that ‎uses a flat‐plate collector with three baffle geometries: simple, triangular, and serpentine. The ‎performance of the ISD was evaluated by the drying of mint plants, a significant agricultural ‎product in the arid climate of El‐Oued, Algeria. Experimental measurements were conducted ‎over several days in May under actual weather conditions, with data from the most stable day ‎chosen for analysis. Measurements were taken from 8:00 a.m. to 5:00 p.m. A thorough ‎evaluation of the system's thermal performance was performed, focusing on key factors such as ‎collector temperature, drying chamber temperature, moisture content, mass loss, shrinkage rate, ‎and thermal efficiency. The results indicate that the serpentine baffle design significantly ‎improved solar dryer ‎performance, ‎reaching a maximum outlet temperature of 67°C (vs. 62°C ‎for triangular and ‎‎56°C for simple ‎designs) and a drying chamber temperature of 52°C (4°C–6°C ‎higher than ‎others). The thermal ‎efficiency attained 36%–48%, above the triangular (29%–38%) and ‎simple (15%–‎‎32%) configurations. ‎Drying was fastest with the serpentine baffle, reducing mint ‎moisture ‎from 78% to 0% in 7.5 h ‎‎(by 3:30 p.m.)، finishing 1 h earlier than the triangular ‎and 1.5 ‎hours earlier than the simple design. A ‎logarithmic model best fit the data ( R ² = 0.9964, ‎RMSE ‎‎ = 0.0178), confirming a strong correlation ‎between baffle design and the efficiency of ‎the ‎drying process.‎