DESIGN AND FABRICATION OF SOLAR TUNNEL DRYER FOR COPRA APPLICATION

Abstract

 A semi-cylindrical forced convection type solar tunnel dryer (STD) was designed and commissioned at M/s Miraj Products Pvt. Ltd., Nathdwara for drying processed tobacco. Essentially it is based on the mixed mode with direct and indirect type of heating mechanism i.e. the heated air from different solar flat plate collectors is passed through drying cabinet. At the same time, the drying cabinet absorbs solar energy directly through the transparent walls and roofs. It consists of 16×3.75 m² area, tunnel equipped with 12 solar flat plate collectors of 2 m² each propelled with 2 exhaust fans of 1 kW capacity placed on both ends of the tunnel. The dryer was tested at no-load and full-load conditions.  During no-load, without flat plate collectors, temperatures inside the dryer were about18-20℃ higher than the ambient temperature during summer day-light, where as in no-load with flat plate collectors, it was about 30℃ higher than the ambient temperature.  A batch of processed tobacco of 500 kg with an initial moisture content 138% d.b. were successfully dried in full load condition to have final moisture content of about 8.7% d.b. in 8 h. It has been observed that STD has many other advantages i.e. getting rid of toxicant gas to labours during opening drying due to lime presence in material, avoidance of product expose to fly contamination and dust concentrations etc.