Determination of drying characteristics and airflow performance of a turbo-stove assisted solar dryer

Food insecurity continues to affect many rural communities in the Philippines due to climate disruptions, poor postharvest systems, and inadequate food preservation methods. Solar drying offers a sustainable and low-cost solution to reduce postharvest losses, particularly for nutrient-rich yet highly perishable crops such as sweet potato leaves. This study designed and evaluated a twin-wall polycarbonate solar dryer with dimensions of 2.3m(width)x1.2m(height)x3m(length) integrated with a turbo-assisted stove (TSD) to enhance drying efficiency and thermal performance. Drying experiments were conducted using four configurations: open dryer (OD), closed dryer (CD), turbo-assisted stove dryer (TSD), and traditional sun drying (SD), with each dryer loaded with approximately 15kg of sweet potato leaves. When no load was present, the TSD exhibited the highest mean airflow rate of 1.14m³/s, followed by the CD (1.07m³/s) and OD (0.83m³/s). Under loaded conditions, the OD and CD recorded higher exhaust airflow rates of 0.54m³/s and 0.50m³/s, respectively, compared to 0.34m³/s for the TSD. The TSD achieved the highest and most consistent drying performance (40–60°C), with the bottom tray recording the peak rate of 358.91g H2O/g dM·h, attributed to its proximity to the heat source. On average, the TSD attained the highest drying rate of 93.784g H2O/g dM·h, which was significantly greater than that of OD (54.062), CD (44.339), and SD (38.067). In terms of moisture removal, sun and open drying methods retained the highest residual moisture, while the CD showed better efficiency, and the TSD consistently achieved the lowest moisture content due to its supplemental heat source and stable temperature conditions. Moreover, statistical analysis revealed a significant difference among treatments (p < 0.0001). Overall, the hybrid solar dryer demonstrated superior thermal performance, higher drying efficiency, and better product quality, making it a cost-effective and scalable postharvest solution for enhancing food preservation and food security in tropical rural areas.

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