Working principle of dryer

For example, the drying of wood before making wood models and wood utensils can prevent the deformation of products, and the drying of ceramic billets before calcination can prevent the cracking of finished products. In addition, after drying materials are also easy to transport and storage, such as the harvest of food dry to a certain wet content below, to prevent mildew. Since natural drying is far from meeting the needs of production development, various mechanical dryers are more and more widely used.
The amount of water vapor in the compressed air is determined by the temperature of the compressed air: while keeping the pressure of the compressed air basically unchanged, reducing the temperature of the compressed air can reduce the water vapor content of the compressed air, and the excess water vapor will condense into a liquid. Freeze dryers use this principle to dry compressed air using refrigeration technology. Therefore, the cold drying machine has a refrigeration system. The refrigeration system of freeze dryer belongs to compression refrigeration, which is composed of four basic components such as refrigeration compressor, condenser, evaporator and expansion valve. They are connected in turn by pipes to form a closed system, in which the refrigerant constantly circulates, changes state and exchanges heat with the compressed air and cooling medium. Compressed air dryers also have adsorption dryers and dissolving dryers.
The refrigeration compressor inhales the low-pressure (low-temperature) refrigerant in the evaporator into the compressor cylinder, and the refrigerant steam is compressed, and the pressure and temperature rise at the same time. The high-pressure and high-temperature refrigerant steam is pressed to the condenser, in the condenser, the refrigerant steam with a higher temperature and the cooling water or air with a lower temperature for heat exchange, the heat of the refrigerant is taken away by the water or air and condensed, and the refrigerant steam becomes a liquid. This part of the liquid is then transported to the expansion valve, through the expansion valve to choke into low temperature and low pressure liquid and into the evaporator; In the evaporator, the low-temperature and low-pressure refrigerant liquid absorbs the heat of the compressed air and vaporizes (commonly known as "evaporation"), and the compressed air condenses out a large amount of liquid water after cooling; The refrigerant steam in the evaporator is sucked away by the compressor, so that the refrigerant goes through four processes of compression, condensation, throttling and evaporation in the system, thus completing a cycle.
In the refrigeration system of the freeze dryer, the evaporator is the equipment that transmits the cold amount, in which the refrigerant absorbs the heat of the compressed air to achieve the purpose of dehydration and drying. The compressor is the heart, which plays the role of inhaling, compressing and transporting refrigerant steam. The condenser is a device that releases heat, transferring the heat absorbed in the evaporator along with the heat converted by the input power of the compressor to the cooling medium (such as water or air). The expansion valve/throttle valve throttles and depresses the refrigerant, controls and regulates the amount of refrigerant liquid flowing into the evaporator, and divides the system into two parts: the high pressure side and the low pressure side.