Performance Study of a Small Engine Waste Heated Bin Dryer in Deep Bed Drying of Paddy

Abstract

Research into minimizing post harvest losses and the effective utilization of available energy resources for the rural farmers has led to the idea to use small engine and its waste heat in drying of farm crops in the rural areas. An small engine ( ≈ 1.6 kW) powered flat deep-bed rough rice dryer was designed and constructed with dimension 900 × 900 ×1100 mm on the basis of available harvested engine waste. A part of the engine brake power was used to rotate the dryer fan directly coupled with the engine camshaft which harvest the engine waste heat released from the cooling system to heat up the drying air. The no-load test showed that engine-waste heat was sufficient to increase the drying air temperature 7 to 220C at an air flow rate of 12.6 to 1.2 kg/min, while the average ambient temperature and relative humidity were 26.7 and 71.1%. The energy requirement was 3.15 MJ/kg of water removed in drying a 100 cm deep grain bed in 22 h in two passes (12 h +10 h) with 12 h tempering overnight between the passes. The drying capacity of the dryer was approximately 22 kg/h (480 kg per batch) of rough rice, while the average ambient temperature and relative humidity were 23.5 and 91% (rainy day). A seventy to eighty centimeter deep grain bed seems to be optimum in order to avoid over-drying in the bottom and under-drying in the top layers at an engine speed of 3,600 rpm. Result have shown promise for this type of grain drying unit especially in major rice growing regions where the same engines which are used for pumping irrigation water and rice milling purposes.