Adaptation of heat pipe dehumidifying technology for drying

Heat pipe is a simple device that can quickly transfer heat from one point to another without the need of a mechanism. The basic make-up of a heat pipe is metal tube (usually copper) sealed at both ends, maintained at a certain pressure and charged with an industrial refrigerant. Using the dehumidifying principle, the Heat Pipe Enhanced Dryer removes moisture from heat pipes, the higher the relative humidity of the ambient air the more efficient it operates due to more water that will be removed. Because of its very dry air, the machine achieves the two most desirable features in grain drying: drying at low temperature to preserve grain quality; and drying in a very short time. Its shorter drying time provides additional energy savings and more grain can be dried during the the harvest season. Initial results from the testing conducted in Irosin, Sorsogon [Philippines] showed that palay with an initial weight of 1,167.50 kg and with an initial moisture content of 26 percent wet basis were effectively dried within 6 hours with a final moisture content of 14 percent wet basis. Total power consumption was 39 Kw-hr. The heat pipe dehumidifier was then retrofitted to a 1.5-ton capacity flat bed bin. The palay samples used for this test that has an initial moisture content of 19.8 percent and an initial weight of 1,405 kg dried down to 13.1 percent within 4 hours. Based on calculation, the drying costs in terms of energy used for this experiment was P0.19 per kg or P9.10 per bag (at 50 kg/bag) at P7 per Kw-hr rate (Irosin power rate) and 4-hour drying operation, while for a 6-hour drying operation, drying cost was P0.23 per kg or P10.9 per bag. These amounts are cheaper by more or less 50 percent than when conventional dryers are used. Grain quality analysis, on the other hand, showed that the head rice percentage using heat pipe enhanced dryer was 79.2 percent, which proves that grain drying using heat pipe dehumidification technology results to high quality grains