The principle of vacuum cooling is similar to that of vacuum drying in that water evaporates rapidly in vacuum. The difference is that vacuum drying dehydrates water, while vacuum cooling only takes heat away by evaporation of water to achieve cooling purposes. The evaporation heat of water is 2256 kJ/kg when boiling at 100 C under normal pressure. When the pressure drops to 610 Pa, the water will boil and evaporate at 0 C (around the three-phase point of water), and then the evaporation heat is 2500 kJ/kg. That is to say, in the low-pressure vacuum state, water evaporation will take away more heat, so as to achieve the effect of refrigeration.
The core equipment of vacuum cooling is vacuum chamber and vacuum pump. The main process of vacuum cooling is to start pumping after the product enters the vacuum chamber. The pressure in the vacuum chamber is pumped to the corresponding saturated vapor pressure and maintained. The water in the product starts to evaporate in large quantities and takes away heat. At this time, the temperature of the product object will drop rapidly until the product temperature is cooled to the required temperature.high-performance-rotary-vane-vacuum-pump
Compared with air-cooled and water-cooled cooling methods, vacuum cooling has the advantages of energy saving, fast cooling speed, relatively uniform cooling, less impact on product structure, and also has the problems of large investment and high weight loss rate. But in general, it is a fast, clean and safe cooling technology, which has more advantages than disadvantages and can obtain high-quality products.
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