Thermal Efficiency Enhancement of a Solar-Powered Dryer Equipped with Cylindrical Heat Fins for Turmeric Drying

Abstract

This research aimed to enhance the thermal efficiency of a solar-powered dryer by integrating cylindrical heat fins for turmeric drying. The prototype dryer was designed with a drying area of 1×1 m² and a parabolic-shaped roof, equipped with cylindrical heat fins of varying lengths (10, 20, 30, 40, and 50 mm) to investigate their effects on internal temperature, heat transfer rate, energy efficiency, and thermal efficiency of the solar dryer. Experimental studies were conducted under simulated solar radiation conditions using a 1,500 watt halogen lamp. The results indicated that the heat fin with a length of 40 mm achieved the highest internal temperature of 54°C and the highest heat transfer rate of 37 W. Additionally, it provided the highest average energy efficiency, ranging between 4.7% and 6.3%, at an air mass flow rate of 2.5×10^-3–7.0×10^-3 kg/s, which outperformed fins of other lengths. When comparing the thermal efficiency between dryers with and without heat fins, the fin-equipped dryer exhibited an average thermal efficiency approximately 2% higher throughout the drying process, with a peak thermal efficiency of 36% during the initial drying stage (10:30–12:00 hrs). Moreover, the fin-equipped dryer demonstrated a faster reduction in moisture content during the initial drying phase without compromising the quality attributes of the product, including moisture content, texture, color, and aroma. From practical application at the community level, the developed solar-powered dryer was able to reduce electricity costs by approximately 5 baht/kilogram/day compared to conventional electric dryers. The evaluation of user satisfaction revealed an overall satisfaction rating at a "very good" level, with an average score of 91.55%, reflecting the suitability of this technology for further application in community-based agricultural product processing.