1. What is a cold storage?
Storage buildings with artificial refrigeration and cold preservation function.
2. Several classifications of cold storage
According to the structural form
Civil engineering library (multi-storey steel concrete structure building library)
Assembly warehouse (single-story steel structure high shelf cold storage)
Civil assembly mixed library (mixed structure)
According to the nature of production
Production cold storage (self-use warehouse of food production and processing enterprises)
Distributed cold storage (logistics cold storage)
Retail cold storage (Shangchao fresh temporary storage)
Household cold storage
According to the insulation system
Internal thermal insulation cold storage (thermal insulation is located on the outdoor side of the structural frame)
External thermal insulation cold storage (thermal insulation is located at the indoor side of the structural frame)
Divide according to scale
Large-scale cold storage: more than 10000 tons
Medium-sized cold storage: within 10000-1000 tons.
Small cold storage: less than 1000 tons
According to the library temperature
High temperature cold storage: design temperature of cold storage (-2~8℃)
Medium temperature cold storage: the design temperature of cold storage (-10~-23℃)
Low temperature cold storage: the design temperature of cold storage (-23~-30℃)
Ultra-low temperature cold storage: design temperature of cold storage (-30~-80℃)
According to the stored goods
Food cold storage
Fruit cold storage
Vegetable cold storage
Drug cold storage
Cold storage of other products
3. Advantages and disadvantages and applicability of civil engineering library and assembly library
Civil warehouse: The durability and stability of the building are good, and the maximum storage capacity can be obtained per unit land area, which is convenient for decentralized leasing. However, with the increase of labor costs, the construction cost is getting higher and higher, which is suitable for the situation of scattered stacking or palletizing and the need for more storage area per unit land area. The market cold storage mainly based on area leasing is generally suitable for decentralized leasing in the agricultural batch market.
Assembly warehouse: the main building materials are prefabricated in the factory, which is easier to control the quality than the civil warehouse, and the construction period is shorter, but the durability of the building is not as good as that of the civil warehouse. It is suitable for taking shelves as the storage mode and trying to get the largest storage unit (trust) in the unit area, which is generally suitable for three-party logistics and large-scale production enterprises.
4. Floor frost heaving of cold storage and protective measures
Floor frost heaving refers to the frost heaving of the soil layer under the floor of the cold storage. The frost heaving phenomenon in cold storage is related to the thickness of floor insulation layer, the movement of freezing point isotherm, the migration of water in soil, soil quality and water content. Although the cold storage floor has a certain thickness of insulation layer, it can not completely isolate the heat transfer. The frost heaving of the ground floor is also the biggest problem faced by the ground structure of cold storage.
Ways to prevent the floor from frost heaving
Overhead floor (direct and reliable, with high cost)
Ventilation floor (with certain limitations)
Heating floor (cost saving, high construction requirements)
Multi-storey cold storage is suggested to be overhead when the geological conditions are poor, and other ways can be considered when it is good; When the geological conditions of single-storey cold storage are poor, it is suggested to heat or ventilate the floor, and when it is poor, overhead can be considered.
5. Cold storage insulation system and analysis
Internal thermal insulation and external structural form: the main structural layer of the building is located outside the thermal insulation. Thermal insulation materials form a continuous closed space in the warehouse.
Its advantages are neatness in the storeroom, easy cleaning, existence of suspended ceiling, flat top and easy division between storerooms; Disadvantages are that there is a self-built cavity with suspended ceiling on the roof, the height of the building is increased, and the double-layer system increases the investment. The thermal insulation wall occupies internal space and reduces the actual use area. All structural parts, cables and hangers that wear suspended ceiling and wallboard are easy to form cold bridges.
External thermal insulation and internal structural form: the main structural layer of the building is located inside the thermal insulation. Thermal insulation materials form a connected closed space, in which the main structure of Chiang's building is wrapped.
Its advantages are that heat preservation is combined with building envelope system, which saves space and investment. The equipment and pipeline hangers in the warehouse are directly connected with the main structure, and no additional cold bridge treatment is needed. The construction is convenient, fast and safe, and it can be developed into a shelf integrated warehouse. The disadvantage is that it is not easy to divide between libraries.
6. Selection of refrigerants
Ammonia: It has the longest history and is the best choice in the field of industrial refrigeration all over the world. Due to its own characteristics, ammonia systems generally adopt centralized refrigeration and set up specialized computer rooms, which are applied to large-scale refrigeration systems (cold storage with a capacity of more than 10,000 tons). In recent years, there has also been a trend of miniaturization and modularization, with the emphasis on improving safety and reducing filling capacity.
Freon: most of the modular units used in cold storage are distributed refrigeration, which is suitable for small and medium-sized cold storage and large-scale cold storage with limited use of ammonia. At the same time, it is suitable for metering in different rooms or intensive processing and sorting by personnel. For the sake of environmental protection, large-scale cold storage should avoid Freon system as much as possible.
Carbon dioxide: Cascade system and cold-carrying system are mainly used in cold storage. The low-temperature field is more suitable for cascade and the high-temperature field is suitable for cold-carrying. Compared with the traditional ammonia and freon system, the cascade system is still more expensive, and its efficiency has no obvious advantage in the temperature application range of cold storage.
7. Choose air cooler or exhaust pipe?
The assembly warehouse is dominated by air coolers, which have a fast cooling speed, and can quickly pull the temperature of the cold storage to the set temperature when the electricity price is underestimated. The packaging of food is getting better and better, and the design of air coolers is more elaborate, which has less and less impact on the dry consumption of goods.
Most of the civil warehouses are lined with pipes, but the trend of new construction is that the proportion of pipes is decreasing day by day, and foreign developed countries have basically eliminated pipes. Compared with the cold air blower, it is difficult to quickly lower the temperature of the cold storage, and there is more frost in the warehouse, which will even affect the quality of goods.
High-end customers are reluctant to enter the exhaust pipe warehouse, and seafood and wholesale customers are reluctant to enter the air cooler warehouse.
8. Shelf form suitable for cold storage
Single-entry deep beam shelf: suitable for quick picking.
Narrow roadway shelf: Compared with ordinary single depth, it has the same sorting property and can get higher storage density per unit area.
Double-depth beam shelf: suitable for large-scale three-way logistics, taking into account the balance of storage density and selection.
Drive-in or gravity shelf: with high storage density, it is suitable for the storage of pallets with fewer SKUs and more single SKUs, and has low requirements for sorting.
Shuttle shelf: Compared with drive-in or gravity shelf, it has higher storage density and is suitable for long-term storage of high-density goods.
Fully automatic shelf: divided into single and double depth, it can realize high density storage in unit warehouse area and can be operated quickly and accurately in unmanned working environment.
9. How to choose the compressor type for cold storage with different areas and temperature zones?
Single scroll unit/parallel scroll unit (suitable for small and medium/medium high temperature)
Single piston/parallel piston unit (suitable for medium/medium low temperature)
Screw single machine/screw parallel unit (suitable for large and medium-sized/high, medium and low temperature)
10. Defrosting of cold storage and methods
The defrosting of cold storage is mainly due to frost on the evaporator surface in cold storage, which reduces the humidity in cold storage, hinders the heat conduction of pipeline and affects the refrigeration effect.
Hot air defrosting (suitable for large, medium and small cold storage tube defrosting)
Water spray defrosting (mostly used for defrosting of large and medium-sized air coolers)
Electric defrosting (electric heating tubes are mostly used for small and medium-sized air coolers)
Mechanical manual defrosting (suitable for defrosting of small cold storage pipes)
11. Mold removal in cold storage and methods
Mold generally grows in dark and humid places and can adapt to lower temperatures. Usually in the high temperature warehouse, the situation is the most serious. Mold grows in the cold storage, and spores will fly everywhere, thus polluting the goods and products stored in the warehouse.
Mechanical mildew removal (manual cleaning and removal of moldy parts)
Physical mildew removal (by means of temperature, humidity, ultraviolet light, high-frequency electricity and copper wire mesh filter)
Chemical mildew removal (carbon dioxide, bleaching powder, sodium fluoride, etc.)
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