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The drying process plays an important role in the preservation of agricultural products. To this day, the drying process of rice grains harvested by the farmers in Semangga District, Merauke Regency, has always used sunlight. However, during rainy season, the farmers cannot dry their grains, and if such thing happens for a long time, it will cause decayed grains. The drying characteristics of a material are necessary in designing the dryers in use. The method used in this research was the design of grain dryers, which took the form of heating oven, by utilizing heat from the residual exhaust gas of diesel engine. The exhaust gas coming out of the exhaust manifold would be flowed through the heating pipe in the oven heating chamber, then through the convective heat transfer process, followed by conductive heat transfer, and then the heat flow conduction would be transmitted to the drying chamber. The objective of this research was to design grain dryers by using Diesel engine's residual exhaust gas, and to calculate the efficiency of grain dryer using heat transfer analysis. The bulk gas temperature in the exhaust gas section for hot fluid in the pipe is 371.55 K at a motor rotation of 2400 rpm, with the flow rate of the incoming exhaust gas heat mass of 0.01798031 kJ/s. The velocity of incoming exhaust gas mass is 36.75 kg/s, with the comprehensive heat transfer coefficient on the inlets of 92.7334404 W/ m2.oC. The heat transfer in the air section/ fluid section in the inner pipe is 351.1351 K, while the convective heat transfer coefficient in exit pipe is 8.010580984 W/m2.oC, thus obtaining Comprehensive heat transfer of 40.2312698 W/ m2.oC. The logarithmic mean temperature difference (LMTD) in the evaporator is 35.69590751oC with total heat transfer area of 084178 m2. With 2400 rpm motor rotation, the total heat transfer at the heat exchanger, which is the usable maximum heat, is equal to 0.226296111 kW; while the effectiveness of heat exchanger is at 60.95%. The energy used to evaporate the water and the amount of convective heat transfer from dry air to the product are 0.03696 kW, while the amount of air energy used is 0.05150 kW, obtaining the efficiency of the drying machine at 71%. |
