College】 【weak pre-cooling refrigerator】.

<br> I. Introduction cold storage cold storage: -23 ℃ ~ -28 ℃. . Library, also known as freezing, freezing cold, the general storage temperature at -20 ° C ~ -30 ° C or so, through the cooling fan or a dedicated device to achieve the frozen food frozen. .<BR> Cold storage temperature is -20 ° C below, as seafood and cold drinks need to -20 ° C the following was not bad, is characterized by low-temperature cold storage equipment from time to time will be gradually put into cold storage, after a period of time .cold storage temperature of -20 ° C, of this time no special requirements, but the stringent requirements of storage temperature is at -18 ° C ~ -23 ° C is a typical low temperature between the cold storage, but storage of dairy products containing .cold, storage temperature should be set at -20 ° C ~ -28 ° C can be, but two different temperature require different levels of equipment, a large gap between investment in equipment. .<BR> Most professionals believe that the low temperature cold storage refrigeration temperature as low as possible, ice storage can extend the shelf life of things, but there are all kinds of items should be based on the storage temperature may be required to fruits and vegetables, low storage .temperature easily lead to frostbite occurs, and low temperature meat products can be stored longer. .However, the economic and energy standpoint, it should be to preserve a long time to select the low-temperature cold storage temperature, such as meat stored at -18 ° C the next 4-6 months, can be stored under -23 ° C 8-12 .months, because meat is coming in 5 months the hands of consumers, so sometimes choose to consider whether the storage temperature -23 ° C, so cold storage design must depend on the life cycle of material goods, the preservation of its effective .the preservation of the environment to choose the right temperature. .Second, the low-temperature air pre-cooling refrigerator pre-cooling methods: air pre-cooling method is easy to adjust air temperature and humidity, can be used for a variety of foods cooling refrigerated transport, equipment cost is low. .Vacuum cooling: According to reduce the boiling point of water with the pressure also reduces the physical nature of the pre-cooling the food placed into a vacuum tank vacuum, when the pressure is reduced to a certain value, the food began to evaporate the water surface, absorbing the latent heat of vaporization, so that food .cooling method is own by vacuum cooling method. .Water pre-cooling: the use of water will be cooled down to the initial temperature of the food from the end of the required water temperature is known as pre-cooling method..