Thermal Analysis of Solar Tunnel Dryer and Evaluation for Commercial Mango Leather Drying

A walk-in type semi-cylindrical shaped solar tunnel dryer (10 m x 3.75 m) was designed, developed and evaluated at Dr. B.S. Konakan Krishi Vidyapeeth, Dapoli for thermal analysis. The dryer was evaluated by conducting no-load test at laboratory to study the thermal profile, energy input/output during the winter and summer season. Based on the laboratory experience, a commercial scale solar tunnel dryer was installed and evaluated at M/s Shirodkar Food Products Pvt. Ltd., kudal, District Sindhudurg (MS) for commercial mango leather drying. The dryer was loaded with 250 kg mango pulp per batch by spreading over 210 number of grease-proof aluminium trays (1.2 kg pulp in each tray) in three layers (70 trays in each layer). Drying of mango leather was studied in comparison with open sun drying and electrical oven drying for time saving and energy consumption. The study revealed that the average rise in temperature of drying air was about 18 -22 0C over the ambient air. The average drying period reduced by 28 % over open sun drying method. The average temperature inside the solar dryer was 62+5 0C, and required 10 h for upper layer of trays, 13 h for second layer of trays, and 17 h for third level of trays as compared to 26 h in open sun drying. The operating energy cost of solar tunnel dryer was zero as compared to 102 kWh in electrical oven. Considering drying of 30 batches per season, the payback period of the system was 2.7 years.