Solar Dryer for Powder Drying

A natural circulation solar dryer for drying products in the form of powder has been developed. It is of modular design and aperture area of one module is 3.34 m(2). A new concept of moveable glazing has been introduced for ease in loading and unloading. Air entering the dryer moves in a zig-zag path as it flows over the product and under each tray before leaving from the top. There is a provision to dry the product under shade. Also, the dryer can be dismantled and stored in a room during off-season. The dryer was tested to dry Di-calcium phosphate (DCP) at Ludhiana (31 degrees N). The average drying efficiency for a batch was found to be 54.0%. The cost of drying DCP using this solar dryer was 0.56 Rupees per kg of dried DCP as compared to 1.94 Rupees per kg of dried DCP for a wood-fueled industrial dryer. In comparison to a solar tunnel dryer for DCP drying, the initial investment per kilogram of the dried DCP, floor area per kilogram of wet DCP, and cost of drying per kilogram of dried DCP for this dryer was reduced by 7.1%, 67.2%, and 16.4% respectively.