Experimental Design of Compact Heat Exchanger for Waste Heat Recovery of Diesel Engine Exhaust Gases for Grain Dryers

Abstract??? In diesel engine cycle, 35% of energy losses through the exhaust gases, the heat is an energy potential that can still be reused for various purposes. This research aims to design a heat exchanger, based of diesel engine exhaust gases integrated with rice milling unit for drying agricultural products. The exhaust gas is derived from 6D16 diesel engine of 120 kVA as a power generator for rice milling unit at South Sulawesi. Exhaust gas temperature reaches 357oC with the mass flow rate of 636 kg/hour at ambient temperatures of 32oC and 84% relative humidity. From the calculation, the energy of the exhaust gas is able to dry 2 tons of paddy in the drying air temperature of 53oC and drying mass flow rate of 6,600 kg/hour for 8 hours drying time. Used is a compact heat exchanger with 0.3 m long, 0.3 m wide and 0.2 m high, using a plain- fin 2.0. Tests carried out using a flat bed drying 174 kg capacity of grain with 24.56% moisture content, using a drying air temperature of 53oC and mass flow rate of 706 kg/hour. At the test, the diesel engine operates on medium speed and without milling process, can produce 128oC exhaust gas temperature and mass flow rate of 403 kg/hour. Dried grain with a moisture content of 13.67% was obtained after the drying process for 5 hours 11 minutes