Characteristics of heat pump drying

- May 07, 2019 -

Drying is a complex process of heat and mass transfer. It is not only affected by material characteristics and drying medium parameters, but also has an important relationship with drying process. Drying is not only a physical process, but also a biological and chemical process . The drying of agricultural products is not only to remove moisture from materials, but also to maintain its color, aroma, taste and texture, and even to retain the biological activity of agricultural products.

Heat pump can convert latent heat released from steam condensation in the exhaust gas from drying process into sensible heat through condenser. For many years, heat pump has been considered as an effective energy recovery method. Especially the combination of heat pump and good drying conditions has made heat pump drying widely used in wood, grain, fruits and vegetables, aquatic products and seeds and other heat sensitive materials drying

The characteristics of heat pump drying

<>1.1, high efficiency and energy saving

heat pump drying medium mainly comes from the recovery of the sensible heat and latent heat contained in the warm and humid air discharged during drying process, which needs input energy. Quantity is only the energy consumption of heat pump compressor, while heat pump has the characteristics of consuming a small amount of energy to obtain a large amount of heat. Therefore, compared with conventional drying devices, heat pump drying has obvious advantages of energy saving and high energy efficiency. Low temperature drying

< H3 > 1.2 at atmospheric pressure

By controlling the evaporation temperature and condensation temperature of heat pump, the drying temperature can be achieved between 0 100 at atmospheric pressure, which provides a low-cost and efficient drying method for heat sensitive materials. Heat pump drying is a kind of mild drying method, which is close to natural drying. The evaporation rate of surface water is close to that of internal surface migration. It ensures the quality, color and grade of dried goods.

<> 1.3 Heat pump drying medium can realize closed cycle

heat pump drying medium can be recycled in the closed system composed of dryer, evaporator and condenser, which can prevent the outside air from entering the drying room to pollute the dried materials. When the dried material is sensitive to oxygen in the air and easy to oxidize, inert medium (such as N2, CO2) can be used instead of air as drying medium to realize anaerobic drying.

<> 1.4 The heat pump drying can be designed into various structural forms according to the characteristics of materials. Heat pump can be combined with convective dryer to form heat pump convective drying device (such as heat pump box drying device, heat pump fluidized bed drying device, etc.) or heat pump heat conductive dryer to form heat pump heat conductive drying device (such as heat pump disc drying device, heat pump rotating device, etc.). Drum drying device and heat pump drum drying device can also be combined with high frequency, microwave and infrared heat pump drying device.

< H3 > 1.5 Environment-friendly < / H3 >

Material drying not only needs to improve product quality and save energy consumption, but also needs to be environmentally friendly. Based on the same evaluation criteria, heat pumps have little impact on global warming. Environmentally friendly is the advantage of heat pump drying unit. At present, heat pump is advocated to reduce CO2 emissions abroad, and its application will be further developed.

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