Thermal Characteristics and Dryer Performance Analysis of Double Pass Solar Collector Powered by Copper and Iron Oxide

Solar renewable energy is prospective for various engineering applications including heat exchanger and air dryer applications. The drying of agricultural products is influenced by the weather, which can limit their dryness on cloudy days and reduce drying efficiency, often necessitating additional measures to complete the drying process. This research aims to enrich the functional characteristics of a double-pass solar collector configured with a dryer unit for drying agriculture products, namely, potato chips, banana chips, and red chilies. The solar collector features a hybrid black paint coating prepared by mixing copper oxide (CuO) and iron oxide (Fe₃O₄) via a spray pyrolysis route with 0.3 µm thickness. The effect of hybrid coating on air temperature, energy input, thermal efficiency, drying rate, moisture ratio, and exergy efficiency of the solar-coupled dryer was estimated and compared with non-coating conditions. The result of hybrid nano-enhanced coating shows superior thermal performance and dryer performance than other coating conditions. The peak air temperature, energy input, and average efficiency are about 66.5 °C, 359.7 W, and 69.7%, respectively. Furthermore, the red chilies show a better average drying rate, moisture ratio, and exergy efficiency of about 0.81 kg/h, 0.39, and 8.4%, respectively.