THE PERFORMANCE OF A SOLAR-REGENERATED OPEN-CYCLE DESICCANT BED GRAIN COOLING SYSTEM

The cooling of stored food grains suppresses the growth of populations of insect pests, inhibits spoilage by fungi and helps to preserve grain quality. In temperate and subtropical climates, grains may be effectively cooled by ventilating them with ambient air. In tropical climates, the enthalpy of the air must be reduced before it can be used for cooling grain. One method of achieving this is to isothermally reduce the humidity of the air. This paper describes experiments carried out on a simple-to-build solar-regenerated open-cycle grain cooling system. The device consists of a 5.85 m2 collector coupled with two beds of silica gel. Results from a series of experiments suggest that the device may be used to cool up to 200 tonnes of grain. The electrical power consumption of the device is of the order of 0.3 watt per tonne of grain cooled, and the total electrical energy consumption is of order of 0.7 kWh per tonne of grain stored for a six-month period. The effectiveness of the device is a function of air flow rate and the enthalpy of ambient air, and results presented in this paper suggest that the solar cooling device is particularly effective in tropical climates.