The use and classification of cold storage Cold storage is a building that uses artificial cooling to make the air temperature in a fixed space reach a specified temperature in order to store items.
Cold storage can be widely used in food factories, dairy factories, pharmaceutical factories, chemical plants, fruit and vegetable warehouses, poultry and egg warehouses, hotels, hotels, supermarkets, hospitals, blood stations, troops, laboratories, etc. Cold storage is mainly used for constant temperature storage of food, dairy products, meat, aquatic products, poultry, fruits and vegetables, cold drinks, flowers, green plants, tea, medicines, chemical raw materials, electronic instruments and instruments.
Cold storage can be divided into different types according to various characteristics. The first is classified according to the scale of cold storage capacity.
At present, the division of cold storage capacity is not unified, and it is generally divided into large, medium and small. The refrigeration capacity of large cold storage is more than 10,000 tons; The refrigeration capacity of medium-sized cold storage is 1000~10,000 tons; The refrigeration capacity of small cold storage is less than 1000 tons.
The second is classified by refrigeration design temperature. It can be divided into four categories of cold storage: high temperature, medium temperature, low temperature and ultra-low temperature.
Generally, the refrigeration design temperature of high-temperature cold storage is -2 °C ~ +8 °C; The refrigeration design temperature of medium temperature cold storage is -10 °C ~ -23 °C; The temperature of low temperature cold storage is generally -23 °C ~ -30 °C; The temperature of ultra-low temperature quick-frozen cold storage is generally -30 °C ~ -80 °C. The third is classified according to the library structure category.
The first is civil cold storage. This is a kind of cold storage that is currently built more, which can be built into single or multi-storey.
The main body of the building is generally a reinforced concrete frame structure or a brick-concrete structure. The enclosure structure of the civil cold storage is a heavy structure, with large thermal inertness, the diurnal fluctuation of outdoor air temperature and the diurnal temperature fluctuation caused by solar radiation on the outer surface of the enclosure structure, and the attenuation in the enclosure structure is large, so the temperature fluctuation of the inner surface of the enclosure structure is small, and the storage temperature is easy to stabilize.
The second is the combined plate cold storage. This kind of cold storage is a single-layer form, the library plate is a steel frame lightweight prefabricated heat insulation panel assembly structure, and its load-bearing components are mostly made of thin-walled steel.
The inner and outer panels of the library board are made of colored steel plate, and the core material of the library board is foamed rigid polyurethane or bonded polystyrene foam board. Since all components except the ground are prefabricated in a professional factory according to unified standards and assembled at the construction site, the construction progress is fast and the construction period is short.
Again earth cold storage. It is also known as earthen cave cold storage, the cave body is mostly arch structure, there are single hole body type, there are also continuous arch form.
It is generally masonry and has a certain thickness of loess covering as a thermal insulation. Used as a low-temperature covered cold storage, the foundation of the cave should be on a sand layer or bedrock that is not prone to frost heave.
Because it has the advantages of adapting to local conditions, local materials, simple construction, low cost, strong and durable, it has been greatly developed in northwest China. There is also cave cold storage.
It is generally built in a rock layer with relatively hard stone and good integrity, and the inside of the cave is generally lined or anchored, and the thickness of the rock layer covering the cave is generally not less than 20 meters. Structure and main equipment of cold storage 1, thermal insulation material and moisture-proof layer A, library plate: pre-produced, with fixed length, width and thickness, can be selected according to the needs of library installation.
High and medium temperature cold storage generally uses 10 cm thick plates, low temperature storage and freezing storage generally use 12 cm or 15 cm thick plates; B, polyurethane spraying foam material: the material is directly sprayed in the warehouse to form a polyurethane board that does not absorb water and has good heat insulation, but the cost is higher. C, polystyrene spray foam material: the material also forms polystyrene plate by spraying, which is more absorbent than polyurethane board, and has poor heat insulation, but the cost is lower.
D, due to the moisture of the thermal insulation material, the thermal insulation performance is reduced. Therefore, a moisture-proof layer should be added on both sides of the heat insulation board, or only an outer moisture-proof layer can be made.
The moisture-proof layer is generally made of asphalt, linoleum, plastic coating, plastic film or metal plate. 2. Refrigeration system A, compressor (the most critical accessory): Under normal circumstances, fully enclosed compressors are selected for small cold storage.
Medium-sized cold storage generally uses semi-hermetic compressors. Semi-hermetic compressors are selected for large cold storage.
B, evaporator: under normal circumstances, the fan is selected as the evaporator for the high-temperature warehouse, which is characterized by fast cooling speed, but it is easy to cause moisture loss of refrigerated products; The evaporation pipe made of seamless steel pipe is mainly used for medium and low temperature cold storage, which is characterized by good constant temperature effect and timely cold storage. C, condenser: The condenser has air cooling, water cooling and cooling methods combining air and water.
Air cooling is limited to small cold storage plants, while water-cooled condensers can be used in all forms of refrigeration systems. 3. Other accessories: temperature control machine, door lock, hinge, handle, etc.
Features and requirements In order to maintain a certain low temperature in the cold storage, the walls, floors and flat roofs of the cold storage are covered with a certain thickness of thermal insulation materials to reduce the heat introduced from the outside. In order to reduce the absorption of radiant energy from the sun, the surface of the outer wall of the cold storage is generally painted white or light color.
Therefore, cold storage buildings are different from general industrial and civil buildings and have their unique structure. Cold storage buildings should prevent the diffusion of water vapor and the penetration of air.
When outdoor air invades, it not only increases the cooling consumption of the cold storage, but also brings moisture into the warehouse, and the condensation of moisture causes the building structure, especially the thermal insulation structure, to be damaged by moisture freezing, so it is necessary to set up a moisture-proof heat insulation layer to make the cold storage building have good sealing and moisture-proof air insulation performance. The foundation of the cold storage is affected by low temperature, and the moisture in the soil is easily frozen.
Due to the volume expansion after the soil freezes, it will cause the ground to rupture and the entire building structure to deform, and the cold storage will be unusable in serious cases. For this reason, in addition to an effective thermal insulation layer, the low-temperature cold storage floor must also be treated under the thermal insulation layer to prevent the soil from freezing.
The floor of the cold storage should be stacked with a large number of goods, and it is necessary to pass through various loading and unloading transportation machinery and equipment, so its structure should be strong and have a large bearing capacity. Building structures are vulnerable to damage in low temperature environments, especially during periodic freezing and melting cycles.
Therefore, the building materials of the cold storage and the structure of each part of the cold storage should have sufficient frost resistance. In general, cold storage buildings are designed to ensure the quality of buildings with their strict thermal insulation, sealing, solidity and frost resistance.
Choose the right cold storage Determine the size of the cold storage according to the tonnage of the goods you store, the daily incoming and outgoing goods and the size of the building, determine the specifications and dimensions of the warehouse door and the opening direction of the door. The installation environment of cold storage should be clean, dry and ventilated.
Depending on the items stored, the temperature in the warehouse is determined by selection. Choose fresh-keeping storage (+5°C~-5°C), refrigeration and freezing (0°C~-18.
