Feasibility Study into Design, Development and Testing of an Indirect Multi-Rack Solar Dryer for Agricultural Products

Abstract

This paper describes the design considerations, followed by the results achieved during its testing and finally a comparison between those experimental results and a computational simulation. The design of the solar dryer was developed with the use of CAD drawing software. The wood-structured unit consists of a front-pass collector, glazed with a 0.6 mm polycarbonate sheet and a copper absorber plate of 0.85 m2 area, and a drying chamber, which holds four wooden aluminium-meshed trays for the drying of different products. The unit was tested under artificial and natural conditions. For the former, an artificial lighting equipment was used to simulate 760 W/m2 solar irradiation and for the latter the unit was tested under direct sun exposure. The temperature achieved on the absorber plate was 67 °C, while the air temperature reached during the indoor test at inlet, tray 1, tray 2, tray 3, tray 4 and outlet was 26, 44, 42, 40.5, 39 and 37 °C, respectively. The results show that it took 14 hours to reduce the moisture content of 2,69 kg of sliced bananas from 78% to 16.9, 17.8 17.7 and 21.2% on trays 1, 2, 3 and 4, respectively and to 20.2% with open sun drying. The thermal efficiency of the designed solar dryer was 37% and the dryer efficiency 14%. The results achieved during the indoor test were compared with a test under natural conditions and a computational simulation (CFD). In both cases similar tendencies were found, showing that the manufacturing was successfully achieved.