USING HEAT PUMP DRYERS IN FARMING

Abstract

The paper presents a schematic diagram of a farm grain dryer containing a steam compression heat pump, which can be also used for farmhouse heating in winter time. The authors have performed a thermodynamic analysis of the heat pump operation in farming dryers given the temperature of a drying agent at the dryer inlet is 60 Celsius degrees, and the heat pump evaporator is located in the ground with a temperature of 8 Celsius degrees. The boiling point of the refrigerant in the evaporator is 3 Celsius degree, which is 5 Celsius degrees lower than the ground temperature. After compressing the refrigerant up to 11.02 bar in the compressor, its temperature rises to 70 Celsius degrees. During the condensation process, the air passing through the drying chamber (drying agent), is heated to 60...63 Celsius degrees. Freon R600a (CH(CH3)5) has been selected as a refrigerant basing on a comparative analysis of the properties of various refrigerants, environmental safety, an operating temperature range, comparatively low pressure in the compression line, and market availability. A thermodynamic cycle of the heat pump has been constructed as well, which has provided the grounds for calculating the energy parameters of the installation. It has been revealed that the power conversion coefficient is equal to 2.98 and that the use of a heat pump allows saving up to 66.4% of the power used for drying. The thermal analysis of the heat pump operation in a grain dryer working process has proved the efficiency of its application on the farm.