Vacuum pump is very useful in food cooling. Generally speaking, there are three ways of heat dissipation: convection (the flow of liquid or gas, which “transports” heat from one area to another); heat conduction (direct heat transfer through physical contact); radiation (infrared radiation). Bread and pastry are not suitable for heat conduction and radiation. In the process of convective heat dissipation, air flow needs a lot of time and space, and the transmission of air to accelerate the cooling process also needs a lot of energy.
Vacuum cooling is mainly used in the cold treatment of food fruits and vegetables and cut flowers. Its application principle is similar to that of another vacuum pump application, vacuum drying, but it is not the same in fact
The principle of vacuum cooling is similar to that of vacuum drying, that is, water will evaporate rapidly under vacuum. The difference is that vacuum drying is to remove water, and vacuum cooling is only to remove heat by evaporation of water to achieve the purpose of cooling. When the pressure drops to 610pa, the water will boil at 0 ℃ (that is, before and after the three-phase point of water), and the evaporation heat is 2500kj / kg. That is to say, in the low-pressure vacuum state, the water evaporation will take away more heat, so as to achieve the refrigeration effect.
The core equipment of vacuum cooling is the vacuum chamber and vacuum pump. The main process is to pump air after the product enters the vacuum chamber, pump the pressure in the vacuum chamber to the corresponding saturated steam pressure and keep it before and after. The moisture in the product starts to evaporate and take away heat. At this time, the temperature of the product object will drop rapidly until the temperature of the product is cooled to the required temperature Some vacuum pumps may need to be equipped with condensing equipment to catch water vapor).
Compared with air cooling, water cooling and other cooling methods, vacuum cooling has the advantages of energy saving, fast cooling speed, relatively uniform cooling, less impact on the product structure, etc., but also has the problems of large investment and high product weight loss rate. But generally speaking, it is also a fast, clean and safe cooling technology, which has more advantages than disadvantages and can obtain high quality products