Heat Pump Dryers
Heat pump dryers running cost just as 40% of oil dryer, 50% of coal burning boiler, 30% of electric boiler. During drying, the material does not craze,does not distortions, nondiscolouring,never degenerate, non-oxidize, drying completely,with good Rehydration, keep nutrient content. These dryers are also form of Dehumidificators. Conventionally, materials are dried either in the field (sun drying) or using high temperature dryers (electric, gas fired, etc.). The heat pump operates according to a basic air conditioning cycle involving four main components: the evaporator, the compressor, the condenser and the expansion valve. The working fluid (refrigerant) at low pressure is vaporized in the evaporator by heat drawn from the dryer exhaust air. The compressor raises the enthalpy of the working fluid of the heat pump and discharges it as superheated vapor at high-pressure. Heat is removed from the working fluid and returned to the process air at the condenser. The working fluid is then throttled to the low-pressure line (using an expansion valve) and enters the evaporator to complete the cycle. In the dryer system, hot and dry air at the exit of condenser is allowed to pass through the drying chamber where it gains latent heat from the material. The humid air at dryer exit then passes through the evaporator where condensation of moisture occurs as the air goes below dew point temperature.