Brief introduction of the purpose of heat pump drying

The purpose of drying is to remove water from some raw materials and semi-finished products to facilitate packaging, transportation, storage, processing, and use. For example, to facilitate the packaging and transportation of food, medicines, and chemical raw materials, it is advisable to dry them before packaging and transportation. It must also be dried for storage purposes, if the moisture content is high it will be conducive to the reproduction of microorganisms, mold, insect pests or deterioration of the product.

The quality of some products is related to the water content. After a correct drying process, its effective components increase, thus improving the quality of the product. For example, the water content of coal must be controlled before combustion to improve the efficiency of the process.

Comparison between heat pump drying device and conventional drying device

Drying generally refers to a removal process. Mechanical method (such as centrifugal force, compressive force, etc.) heating method (to convert water into steam), chemical adsorption method (to remove water from materials) can be used to remove water from engineering materials. by adsorbent).

Conventional drying devices often directly use electric heating or fossil fuels to obtain the heat energy required for drying. As an example, consider the drying of materials with hot air. As shown in fig. 1.1, the conventional drying device, the ambient air is heated to a suitable temperature by using boiler or an electric heater, and the hot air enters the chamber to transfer heat to the material, so that the moisture in it is vaporizes and is released into the environment.

Waste gases that contain a lot of moisture are generally discharged directly into the environment. In terms of efficiency, if the fuel energy or electrical energy entering the heater is 100 parts. And the loss of heat energy from the heater is taken into account, the outgoing hot air uses 70-95 parts of the energy.

On the other hand, the heat pump is an efficient heating device (thermal energy produced/energy consumed > 100%). The heat pump dryer is a winning combination. In fig. 1.2 shows a typical heat pump dryer. In this drying method, the residual air discharged from the dryer is no longer discharged into the environment, but re-enters the heat pump. Heat pumps consume 100 parts of electrical energy and typically produce 140-800 parts of thermal energy.

TROCKNNER equipment uses the inverse Carnot principle to absorb free heat in the air by inputting a small amount of electrical energy and transferring it to the drying room. The heat pump dryer is composed; of a compressor, condenser (heater). throttling device (electronic expansion valve), evaporator (heat absorber) and other devices that help to form a circulation system for the refrigerant. The refrigerant circulates in the system under the action of the compressor. After entering the condenser, the refrigerant raises its temperature up to 120°C, which allows the air in the drying room to be heated. At the same time, it cools down into a liquid that flows into the evaporator, where it rapidly evaporates and absorbs heat to become a gas again, and the temperature drops to -30°C.