Equipment Sizing and Method for the Application of Exhaust Gas Waste Heat to Food Crops Drying Using a Hot Air Tray Dryer

Abstract

Objectives: Equipment sizing and method of utilizing exhaust gas waste heat for food crops drying are presented. Methods/findings: The sizing of the components of the equipment was achieved using known design principles. The system uses an axial flow turbine and a heat exchanger to harness the energy of the exhaust gas of a diesel engine generator. A 250 kVA generator with measured exhaust gas flow rate and temperature of 44.5 m 3 /min and 382.7 °C was selected for this work. The purpose of the recovered energy is for the drying of food crops. An arduino platform was used to control the operation of the components of the dryer. The drying chamber consists of three trays whose calculated total volume per batch is 0.0463 m 3. Weight losses across the trays, drying air temperature and humidity in the chamber are monitored by sensors. The test rig of the sized and fabricated equipment is currently undergoing extensive experimentation. Preliminary investigation of the dryer showed that the drying air in the chamber initially at the temperature and humidity of 31ºC and 71.2% was heated to 88ºC and 22.3% when the dryer operated without load for 45 min at an air speed of 2.0 m/s. Application: After cooling and maintaining the drying chamber averagely at 59ºC, each tray was loaded with 400 g of the grains of freshly harvested maize. The dryer was allowed to run for 30 min and the results obtained showed weight losses of 127.81 g, 118.36 g, and 116.91 g for the grains in trays 1, 2, and 3, respectively. The application of this energy recovery system to the drying of food products, would help to save a considerable amount of primary fuel which is considered a viable means of cost saving and amelioration of environmental degradation.

Investigation of the Thermal Profile of a Crop Dryer Powered by Generator Exhaust Gas Waste Heat

“…As human population and urbanization grow, there is a concomitant increase in energy use that translates into significant increases in fuel costs [1,2]. Diminishing supplies of petroleum and progressive rise in fuel prices are influencing governments and industries to seek for ways of improving the energy efficiency of engines [2,3].…”

“…As human population and urbanization grow, there is a concomitant increase in energy use that translates into significant increases in fuel costs [1,2]. Diminishing supplies of petroleum and progressive rise in fuel prices are influencing governments and industries to seek for ways of improving the energy efficiency of engines [2,3]. Woolley et al [4] reported that up to one third of the global energy consumption is attributable to the industrial sector, with about fifty percent mainly wasted as heat.…”

“…Waste heat recovery (WHR) is an important method of achieving reduction in energy wastes and the emission of greenhouse gases [5]. In recent times, considerable efforts are made towards the reduction of the quantity of energy dumped into the environment from internal combustion engines; and the main objective is to assist in conserving finite resources of fossil fuels, to reduce carbon footprint and combat climate change as well as improve process economics [2,6,7]. To reduce overdependence on fossil fuels and minimize their impact on the environment which manifests as pollutant emissions, Woolley et al [4] noted that manufacturers should prioritize on the use of renewable energy systems or the reduction of energy consumption using WHR techniques.…”

“…One method of achieving this is by the use of a WHR dryer. To actualize this, a tray dryer powered by generator exhaust gas waste heat for the drying of food crops was designed and developed by Ononogbo et al [2]. The equipment comprises two stages of waste energy recovery from the exhaust gas.…”

CFD Study of Exhaust Gas Energy Recovery Potential of a Radial Flow Turbine for Electricity Generation

“…Furthermore, the high cost of fuels required to generate power to operate production equipment and machines is also driving research on internal combustion (IC) engine efficiency optimization. Improved conversion of energy in engines gives rise to reduced energy costs globally [2,3]. Lee et al, [4] reported that the waste heat recovery has proved viable in improving the efficiency of IC engines.…”