Conceptual design of tomato dryer: fabrication and testing of prototype

A hot–air dryer was designed, built and tested for small scale drying of tomato (Lycospersicum esculentum). Design considerations focused on portability, durability, ease of operation and maintenance, and techno–economic status of the micro and small scale tomato farmers and processors who are the intended users of the dryer. The functional parts of the dryer included an 0.67 hp centrifugal fan inside a fan casing, four heaters each of 1.25 kW inside a heating chamber and a drying chamber consisting three shelves of drying trays. In operation, air is heated by the heaters in the heating chamber and the heated air is conveyed to the drying chamber where it dries the tomato samples by heat and mass transfer processes. The dryer was tested by drying 840 g samples of sliced tomato at a temperature of 55°C for 6 h and results showed that the dryer was able to dry the tomato sample from the initial moisture content of 89% (wb) to the final moisture content of 21.8% (wb). Powered by a 1.0 hp single–phase electric motor, the dryer has a production cost of USD 250.