Cold storage basics 1. Cold storage A warehouse that us […]
Cold storage basics
1. Cold storage
A warehouse that uses cooling facilities to create suitable humidity and low temperature conditions is also called a cold storage. Cold storage is the basis for the development of the cold chain industry, an important part of the cold chain, and also a market segment with a large capacity in the cold chain industry.
2. The composition of cold storage
Cold storage is generally composed of maintenance structure and refrigeration equipment. It is mostly refrigerated by a compressor, using liquid with a very low vaporization temperature as a coolant to evaporate under low pressure and mechanically controlled conditions, and absorb the heat in the storage to achieve the purpose of cooling.
Commonly used refrigeration systems are mainly composed of compressors, throttle valves, condensers and evaporators.
2 Classification of cold storage
1. According to the structure, the cold storage can be divided into: civil cold storage, assembled cold storage (active cold storage)
2. According to the nature of use, cold storage can be divided into: production cold storage, distribution cold storage, retail cold storage
3. According to the scale, the cold storage can be divided into: large cold storage, medium cold storage, small cold storage (small cold storage)
4. According to the working fluids of the cold storage refrigeration equipment, the cold storage can be divided into: ammonia cold storage and freon cold storage
5. According to the requirements of storage temperature, cold storage can be divided into:
High-temperature storage: The storage temperature is around +5℃～-5℃, mainly used to store fruits and vegetables, eggs, medicinal materials, etc. The storage temperature is generally controlled at no lower than the freezing temperature of the food juice. The holding temperature of the cooling room or cooling room is usually around 0°C.
Medium temperature storage: the storage temperature is around -10℃～-18℃, mainly used to store meat, aquatic products and products suitable for this temperature range.
Low-temperature storage: the storage temperature is around -23℃～-30℃, also known as freezing storage, freezing cold storage, freezing food through air cooler or special freezing device.
Ultra-low temperature storage: The storage temperature is less than -30℃, used for special purposes such as quick freezing, industrial testing, and medicine.
6. According to the compressor type:
1. Suction and exhaust method: a) scroll type; b) piston type; c) screw type
2. Structure: a) Fully enclosed type; b) Semi-closed type
3 Four major components of cold storage
1. Thermal expansion valve
1. Throttling and reducing pressure;
2. Adjust the refrigerant flow;
3. Keep it superheated
Precautions for calculation and selection
1. Information needed for cooling load calculation:
① Environment-meteorological parameters, surrounding buildings, installation location
② Stored items-temperature requirements
③ Cold storage size-length, width, height
④ Insulation structure-material, thickness, side plate, top plate, bottom plate
⑤ Osmotic load-medium, strong, weak, ventilation frequency
⑥ Product load-type, storage, storage volume, storage temperature, freezing and cooling time
⑦ Mixed load-including lighting, motors, and operators
⑧ Other electrical equipment
⑨ Condensation method-air cooling or water cooling, evaporative cooling
⑩ Type of evaporator-air cooler, pipe rack, etc.
2. Source of cold storage load:
① Heat conduction-wall, top plate, bottom plate
② Penetration-opening and closing doors, gaps in enclosure structure, forced ventilation
③ Store products-freezing and cooling, cold storage
④ Mixed load
1. Heat conduction-wall, top plate, bottom plate
Q = K x A x △T
Q = total heat load
K = heat transfer coefficient
A = area
△T = temperature difference
Pay attention to the different temperature differences of the wall, top and bottom