Performance analysis of solar dryer with thermal energy storage and without thermal energy storage for Whole and Sliced ficus carica (fig)

Solar-drying technology offers an alternative which can process the vegetables and fruits in clean, hygienic and sanitary conditions to national and international standards with zero energy costs. It saves energy, time, occupies less area, improves product quality, makes the process more efficient and protects the environment. In this work efforts have been made to develop the mixed mode forced convection solar dryer for fig drying with thermal energy storage. The performance of the dryer has been investigated experimentally. Dryer is designed with capacity of 25 kg and consist of the parabolic trough collector-based air heating system integrated with thermal energy storage which utilizes Paraffin wax (PCM) as phase change material. Effect of mass flow rate of air on moisture content, drying rate and drying time with and without incorporation of thermal energy system has also been evaluated. The pretreated sliced and whole figs are dried with developed solar dryer to check effect on drying time for different air flow rates. The thermal efficiency of dryer has been evaluated with the without use of thermal energy storage system for sliced and whole fig for different air flow rates. The dried figs are tested for final moisture content and its nutrition value with the commercially available dried fig in the market. The result shows that it is possible to dry the figs cultivated in India in accordance with international norms for moisture content and nutrition value for dried fig. The moisture reduction of fig obtained with developed dryer is from 79% to 18% for sliced fig in 7 sunshine hours and 79% to18% for whole fig in 12 sunshine hours with thermal energy storage system. Incorporation of thermal energy storage system reduces drying time from 9 sunshine hours to 7 sunshine hours for sliced fig with mass flow rate air 0.027 kg/sec. Drying time reduction is observed with increase in mass flow rate of air for sliced as well as whole fig. The sliced fig gives better dryer thermal efficiency and lower drying time for higher mass flow rate of air. For the maximum mass flow rate of air of 0.027kg/s, sliced figs drying gives about 37% dryer efficiency with implementation of thermal energy storage and the lowest drying time of 9 hours.For the same mass flow rate the drying of whole figs gives lower efficiency of about 22% and increase in the drying time up to 14 hours as compared to the drying of sliced figs.