The air-energy heat pump dryer has been widely used drying products. Dried vegetables are a traditional ingredient. Such ingredient was made for the purpose of storing vegetable food. Talented vegetable growers make all kinds of fresh vegetables into dried vegetables for convenient storage in case of emergency. However, the soil structure in different regions is not exactly the same, the taste and nutrients of the same vegetable are slightly different, and the methods of making dried vegetables are also very different. Nowadays, the intention of making dried vegetables is no longer just for filling people’s stomach, but for enriching the food ingredient types and inheriting food civilization.

In the drying process of the air-energy heat pump dryer, when the leaf mustard was in touch with air, it will draw a lot of heat energy from the air, part of which is used to increase the temperature of the leaf mustard, and the other part is used for migration and evaporation of water in the leaf mustard. The air energy can continuously transfer heat to the leaf mustard and evaporate the water from the leaf mustard. This is the continuing drying process, which is divided into 2 stages: heating stage and constant speed drying.

The initial stage of drying is heating, and the temperature should be 40-50°C. The first is that the water on the surface of the leaf mustard absorbs energy and becomes water vapor. Its dissipating speed has a certain relationship with the surface area of the leaf mustard, air velocity, temperature, and relative humidity of the air. In terms of the agricultural product dryer, the faster the air flow rate, the higher the temperature. In addition, the lower the relative humidity of the air, the faster the dispersion speed. That is, if the leaf mustard evaporates faster, the moisture content becomes lower, and the drying speed become faster.

The air energy heat pump dryer is equipped with a special heat-absorbing medium, that is refrigerant. The refrigerant’s evaporation temperature is lower than minus 20 degrees compared with outside temperature. Therefore, the refrigerant can absorb external heat energy and realized internal evaporation. The temperature of the refrigerant has been risen through the operation of the compressor in the heat pump equipment, and then the refrigerant is converted from vaporization to liquefaction through the condenser. During the conversion process, a lot of heat is released and transferred to the reserve water in the water tank, which can realized the purpose for raising the water temperature and to make hot water.