Tomatoes drying under natural conditions using an indirect solar dryer

Abstract

This paper presents an experimental study of an indirect solar dryer operating under natural convection in winter. The results show favorable thermal conditions for drying tomatoes. Tomato slices were dried from an initial mass of 616.56 g to a final mass of 196.31 g. Despite low solar radiation, the dryer increased the internal temperature by 14.6 °C. The thermal efficiencies of the solar air collector and the solar dryer were found to be 96% and 97%, respectively. The thermal efficiencies of the solar air collector and solar dryer were determined to be 96.98% and 82.13% respectively. The moisture content (MC) of the tomatoes decreased from 16.39 kg/kg (dry basis) to 2.91, 4.62, 5.15 and 5.38 kg/kg db for trays 1, 2, 3 and 4, respectively. Based on the drying kinetics, the average effective moisture diffusivity was 1.2593 × 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−9</sup> m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/s.