Despite high levels of good quality tomato production in Kenya, about 40% of the produce goes to waste. This loss is attributed to glut during the harvesting season, poor feeder roads which lead to inaccessibility to the market centres as well as bruise damage during transport. This translates to a huge financial loss to tomato farmers. Preservation through drying technology can help in reducing this loss. Therefore, this study was initiated to investigate the performance of an experimental Liquefied Petroleum Gas (LPG) dryer with energy storage for tomato drying in rural and urban markets. LPG was chosen for the study because it can easily be substituted with biogas produced from biodegradable market wastes in order to operate under all weather conditions and hopefully reduce operational costs. The dryer was designed, developed, constructed and installed at the Appropriate Technology workshop, Kenyatta University, Nairobi, Kenya. The main components of the dryer were the thermal storage tank/boiler, heat exchanger, drying chamber and two 12V DC fans powered by two 50-Watts photovoltaic/200 Amp-hours battery electrical system. The thermal storage system was constructed from a 225-litre water heater tank (diameter 63.5 cm and height 109.2 cm) whose centre contains a cylindrical tube fitted with an LPG burner. The wall of the tank/boiler was made from 14gauge (2mm) galvanized iron sheet capable of withstanding 4 bar pressure. The boiler was well insulated with a composite wall comprising of a 2.5cm layer of vermiculite thickness, followed by 5cm layer of woollen blanket materials and finally covered with 2.5cm of plaster of Paris. A shell and tube single pass cross flow heat exchanger rated at 8.21KW comprising of five radiator panels each consisting of two 0.038m internal diameter sub-headers and fourteen 0.025m internal diameter finned risers all made from galvanized iron pipes was constructed and fitted onto the entrance of a rectangular drying cabinet fitted with wire mesh trays. Sliced fresh tomatoes were loaded onto the trays. The LPG gas was lit and then ambient air was forced into the heat exchanger and heat energy was recovered using 12VDC pusher and puller fans powered by two-50W PV panel and 200Ah battery and passed through the drying trays. Several runs were conducted with and without load and repeated six times. The results demonstrate that unloaded dryer with ambient air entering at an average of 25oC and boiler maintained at 92oC and low, medium and high air flows of 0.19, 0.23 and 0.28m3/s respectively generated corresponding drying temperatures of 57.1, 54.4 and 52.5oC respectively. It was also observed that at an air velocity 0.28m3/s and drying air temperature of 52.5oC, the dryer showed potential to dry 9kg tomatoes from 93.7% to 13% (wb) moisture content within 10.3 hours and consuming 10 kg of liquid propane gas. With a maximum air velocity of 0.43m3/s and drying temperature of 43.3oC, tomatoes were dried to moisture content of 8% but at a longer duration of 11.5 hours consuming 6kg liquid petroleum gas.
AfroAsia, R (2021). Design, Development And Testing Of A Liquefied Petroleum Gas Powered Tomato Dryer With Water Energy Stotage. Afribary.com: Retrieved June 21, 2021, from https://afribary.com/works/design-development-and-testing-of-a-liquefied-petroleum-gas-powered-tomato-dryer-with-water-energy-stotage
Research, AfroAsia. "Design, Development And Testing Of A Liquefied Petroleum Gas Powered Tomato Dryer With Water Energy Stotage" Afribary.com. Afribary.com, 05 Jun. 2021, https://afribary.com/works/design-development-and-testing-of-a-liquefied-petroleum-gas-powered-tomato-dryer-with-water-energy-stotage . Accessed 21 Jun. 2021.
Research, AfroAsia. "Design, Development And Testing Of A Liquefied Petroleum Gas Powered Tomato Dryer With Water Energy Stotage". Afribary.com, Afribary.com, 05 Jun. 2021. Web. 21 Jun. 2021. < https://afribary.com/works/design-development-and-testing-of-a-liquefied-petroleum-gas-powered-tomato-dryer-with-water-energy-stotage >.
Research, AfroAsia. "Design, Development And Testing Of A Liquefied Petroleum Gas Powered Tomato Dryer With Water Energy Stotage" Afribary.com (2021). Accessed June 21, 2021. https://afribary.com/works/design-development-and-testing-of-a-liquefied-petroleum-gas-powered-tomato-dryer-with-water-energy-stotage