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How to build cold room and design the refrigeration system?

What is a cold room?

Cold room is a building warehouse using refrigeration machine to reach a certain temperature and has insulation to hold the temperature.

It is also a constant temperature and humidity storage room for foods, liquid, chemical, pharmaceutical, vaccine, scientific experiments and other items. The refrigeration system of the cold room is still a core component of the construction of the entire cold storage room.

1, Cold room refrigeration system refrigerant:
Ammonia: the oldest in history, the best choice in the field of industrial refrigeration worldwide. Due to the characteristics of the ammonia system, it is generally used for centralized refrigeration, with a special machine room for large-scale refrigeration systems (more than 10,000 tons of cold storage). There is a trend toward miniaturization and modulation, with an emphasis on improving safety and reducing the amount of charging.

Freon: It is widely used in cold storage to disperse refrigeration. It is suitable for small and medium-sized cold storage and large-scale cold storage with limited ammonia. For environmental protection, large-scale cold storage The Freon system should be avoided as much as possible.

CO2: The cold storage application is mainly based on cascade system and loading system. The low-temperature field is more suitable for cascade. The high-temperature field is suitable for loading. The cascade system is more expensive than the traditional ammonia and Freon system.
According to the cold room temperature:
High temperature cold room design temperature (-2~8°C)
Medium temperature cold room design temperature (-10~-23°C)
Low temperature cold room design temperature (-23~-30°C)
Ultra-low temperature cold room design temperature (-30~-80°C)
According to the cold room scale:
Large cold storage over 10,000 tons
Medium-sized cold storage 1000-10,000 tons
Small cold storage less than 1000 tons
The polyurethane cold room panels is made of lightweight polyurethane as the inner material of the cold room panels. There are Pu panels, PUR panels and PIR panels. Jointing type is Cam lock, tongue and groove, hook and pin. The surface materials has galvanized color steel, stainless steel, and aluminum sheet.
The cold room panels thickness is 50mm, 75mm, 100mm, 120mm, 150mm, 175mm, 200mm, 250mm. The quality of cold room panels is also an important reason to affect the cold room temperature.
The most important in purchasing cold room panels is the density and air tightness of the panels.

2, Refrigeration system compressor unit choice:

The compressor is the heart of the refrigeration system. According to the scale of the cold room and the design temperature, the rational selection of the refrigeration compressor unit is the key to the design of the refrigeration system.

In the cold room applications, we mainly use reciprocating compressors, screw compressors and scroll compressors.

Ammonia refrigeration systems generally use open-type compressors, mainly using open screw compressors. Freon refrigeration systems generally use scroll compressors and semi-hermetic or hermetic compressors. When the cooling capacity is small, semi hermetic reciprocating compressors are generally used. When the cooling capacity is large, open screw compressors are generally used. In order to meet the economic requirements of the refrigeration system under different load conditions, and to ensure the reliability of the operation of the refrigeration system, the compressor unit can be used in parallel with multiple compressors.

3, Liquid supply type choice:

The liquid supply of the refrigeration system are divided into four types: direct expansion supply, gravity supply, liquid pump supply, and air pump supply.

The common liquid supply for cold room refrigeration systems are direct expansion type liquid supply and liquid pump forced supply. Usually, the small refrigeration system uses a direct expansion type liquid supply system, and the large refrigeration system uses a barrel pump forced liquid supply system.

The advantages of the barrel pump are as follows: 1 the evaporator has high heat exchange efficiency and good cooling effect; 2 can ensure long-distance liquid supply; 3 the operating condition of the refrigeration compressor can be improved to ensure the safe operation of the refrigeration compressor And improve the refrigeration efficiency of the compressor; 4 system operation is simple and reliable, easy to centralize control and automation.

The disadvantages of it: 1 the refrigerant charging is large, the machine room area is increased, and the initial investment is increased; 2 the system oil return is complicated, and the faulty treatment will cause the entire refrigeration system running failure.

4, Refrigeration system automation control

For large refrigeration systems, centralized PLC control systems are generally used.