Vacuum pre cooler is a cooling and processing equipment that uses vacuum pre cooling technology to extract air and water vapor from the vacuum tank using a vacuum pump to reduce the air pressure inside the vacuum box. Under low pressure, the boiling point of water decreases, the latent heat of evaporation increases, and free water on the surface of the cooled object vaporizes, taking away its own and environmental heat, achieving a cooling effect.
Basic Principles
Fresh agricultural products still have vitality after harvesting, and respiratory and other physiological changes continue to accelerate product aging, wilting, and yellowing. Low temperature can inhibit physiological changes that cause product deterioration and slow down bacterial growth.
At a standard atmospheric pressure, the boiling point of water is 100 ℃, and the heat of evaporation is 2256KJ/kg; When the pressure drops to 610 Pa, the boiling point of water is 0 ℃ and the heat of evaporation is 2500KJ/kg. As the air pressure decreases, the boiling point of water decreases, and the heat consumed to evaporate a unit mass of water increases. Vacuum pre cooling is the process of rapidly evaporating water at a lower temperature in a vacuum treatment chamber under vacuum conditions. During this process, a significant amount of heat is consumed, resulting in a cooling effect in the vacuum chamber without an external heat source. The principle of vacuum pre cooling technology is simple, the cooling speed is high, and it is widely used in the preservation, transportation, and storage of agricultural products.
In vacuum pre cooling, pre cooling refers to a rapid cooling in a short period of time, and the pre cooling time is determined based on the properties of the cooled object, usually in minutes or hours. Vacuum pre cooling treatment is not a simple cooling method, but a technology that utilizes the special environment of vacuum to achieve rapid cooling.
An air pre cooler is not a refrigeration equipment, but a cooling and processing equipment, which is a cooling device used before products are placed in storage rooms or on shelves. The physiological changes of the product after cooling are slowed down, which can extend the storage or shelf life of the product. The vacuum precooler is designed based on the characteristics of low boiling point and high evaporation heat of water under low pressure. Its main characteristics are as follows:
1. Fast cooling speed: It takes 20-30 minutes to reach the required refrigeration temperature.
2. Uniform cooling: The free vaporization of water on the surface of the product takes away its own heat to achieve the purpose of cooling, achieving uniform cooling from the inside out.
3. Clean and hygienic: Under vacuum conditions, it can sterilize or inhibit bacterial growth, preventing cross contamination.
4. Thin layer drying effect: It has unique effects such as curing skin damage or inhibiting expansion of fresh-keeping materials.
5. No packaging restrictions: As long as there are air holes in the packaging, the item can be evenly cooled.
6. High freshness: It can preserve the original color, aroma, and taste of food, and extend the shelf life.
7. High degree of automation: The refrigeration system and vacuum system pressure can be controlled through pressure sensors, making it convenient to adjust the vacuum degree of the vacuum pre cooler. It can also be remotely controlled, making it easy to monitor equipment operation and quickly solve equipment faults.
8. High precision: Equipped with precision digital temperature and humidity controllers, precise control of vacuum and humidity.
9. Safety and stability: The electrical part adopts well-known brand products to ensure stable operation, long service life, and safe operation of the machine.