Experimental Study of a Mixed-Mode Solar Dryer with Internal Reflectors for Tomatoes Preservation

A mixed-mode solar dryer with forced circulation and internal reflectors has been developed and evaluated for its performance for drying of tomato slices. Two solar PV module powered, 3 W DC fans, are installed for ventilation. The cabinet of the dryer is 70 cm in length and 70 pm wide and loading capacity of 2 kg of tomatoes, respectively. Tomatoes were cut into slices and loaded in perforated trays within the cabinet. The drying characteristics were studied and compared with natural convection based indirect solar dryer. To investigate its performance, three experimental runs with 1 kg of tomatoes were carried out in the dryer during the month of October 2024. The experiments showed that drying rate initially increased and then started decreasing gradually as the drying progressed. It was also observed that the forced convention drying produced better quality, color and texture of the dried product compared to natural convection based dryer. The drying temperature also improves with internal reflectors in dryer. At the start, the moisture content of tomatoes was 91-95 %. The time taken to dry 1 kg tomatoes up to 5-10% moisture content without auxiliary heating in 11-20 hours, while the drying efficiency was varying from 12 to 20%.