Performance investigation of solar air dryer with and without PCM based heat storage material for agricultural products drying

An indirect forced convection solar air drier integrated with phase change material (PCM-Paraffin wax 56-58, scientific name-Heptacosane, heat of fusion 223 kJ/kg, melting point is in the range of 56°C to 58°C) based on heat storage unit has been developed to test its performance for agricultural produce drying. A novel solar air dryer consists of a waste aluminum beverage can as a replacement of costly plain absorbing plate in a solar flat plate collector. The system consists of a solar panel along with a drying cabin integrated with PCM storage tray. A selective coating material made from a mixture of charcoal and black board paint has been used as a coating material and is applied over the aluminum cans. The performance of solar air dryer has been tested with and without PCM storage system for drying green chili crop of 15 kg weight. Three different mass flow rates (0.006, 0.008 and 0.01 kg/s) were considered under variable solar radiation condition. The results show that after sunset, the output air temperature of the drying cabin is 2 °C -11.2 °C higher than the ambient temperature. In addition, the maximum drying efficiency are evaluated and found that a maximum of 30.84% is achieved for a mass flow rate of 0.008 kg/s. The drying thermal efficiency was obtained with the use of PCM is 30.15%, 30.84% and 30.78% for the mass flow rate of 0.006 kg/s, 0.008 kg/s and 0.01kg/s respectively as compared to that without PCM i.e., 28.76%, 28.30% and 28.76% for the mass flow rate of 0.006 kg/s, 0.008 kg/s and 0.01 kg/s respectively The developed solar dryer successfully maintains the higher temperature after sunset which helps to reach desired moisture content of drying chili and it can be used for drying other agricultural produce like onion, coriander, slice of potato, etc.