Investigation of the thermal performance of an indirect forced convection solar dryer for tapioca chips drying

Abstract

Tapioca (cassava) is rich in carbohydrates and is usually dried through the open sun drying method in rural areas, which ultimately reduces the quality of the dried products. Solar dryers are commonly preferred green structure for drying mostly food products under controlled environment by utilizing clean and eco-friendly solar energy. In this work, an indirect solar dryer powered by a solar air heater is fabricated with longitudinal fin arrangements for efficient heat exchange between the sensible heat storage material and absorber plate. The solar air heater is additionally facilitated with twin tilt adjustable mountings to maximize the absorption of solar insolation. Initial moisture content of tapioca was reduced from 64.45% (wet basis) to less than 10% (wet basis) in 90 min at 0.03 kg/s air flow rate with the average thermal efficiency of 34.75%. The effective moisture diffusivity value for solar drying was found to be varying between 6.769 × 10–11 and 9.298 × 10–11 m2/s for different flow rates, whereas for the open sun drying it was determined as 3.572 × 10–11 m2/s. The payback period of the solar drying system is obtained as just 1.30 y, which is much lower than the life of the system (10 y). The quality analysis of the dried samples indicated that the total colour change of the solar drying is better than the open sun drying. It is concluded that the solar drying substantially, reduces the drying time and can be utilized as an economic empowerment option for the rural women.