The refrigeration system of a cold storage is the core that ensures the realization of refrigeration and freezing functions. It consists of a series of carefully designed components that work together to maintain the temperature inside the storage within a preset low temperature range.
The system primarily comprises four key components: firstly, the refrigeration compressor, which compresses the refrigerant, increasing its pressure and temperature; secondly, the condenser, which cools and converts the high-temperature, high-pressure gaseous refrigerant into a liquid state; thirdly, the throttling device, such as an expansion valve or capillary tube, which facilitates evaporation and heat absorption by reducing the pressure of the liquid refrigerant; and finally, the evaporator, where the refrigerant absorbs heat from the surrounding environment to achieve a cooling effect. In addition, there are a series of common auxiliary components, which are described below.

1. Compressor

Commonly used types include rotary, piston, screw, scroll, centrifugal, and so on.

2. Condenser

The main purpose is to cool and condense the superheated steam discharged from the compressor into high-pressure liquid.

Water-cooled condenser: The refrigerant vapor condenses outside the tubes inside the shell, with cooling water flowing inside the tubes. Generally, the cooling water enters from the bottom and exits from the top. It has a high heat transfer coefficient and good condensation effect, and is often equipped with a water pump and a cooling tower.

Air-cooled condenser: It utilizes air as the cooling medium and employs a fan to accelerate air flow. It is suitable for locations where water supply is difficult or where installing equipment such as cooling towers is not feasible, albeit with slightly reduced condensation efficiency.

3. Throttling device

The main function is to throttle and reduce pressure, ensuring a pressure difference between the condenser and the evaporator, so that the refrigerant evaporates and absorbs heat at low pressure (low temperature) in the evaporator; it adjusts the flow of refrigerant to adapt to changes in the heat load of the evaporator. Thermal expansion valve: internal balance type, external balance type, capillary tube, electronic expansion valve.

4. Evaporator

The throttled liquid refrigerant vaporizes and absorbs heat (at low temperature and low pressure) in the evaporator, thereby reducing the temperature of the medium being cooled.

Calandria: simple structure, easy to manufacture, low heat transfer coefficient, difficult oil return.

Air cooler: Generally, it is of the non-flooded type, with a small amount of liquid charge, which is conducive to oil return, resulting in less heat loss and faster temperature reduction.

Horizontal shell-and-tube evaporator: Typically a dry shell-and-tube evaporator, it boasts a high heat transfer coefficient but poses difficulties in oil return. It is commonly used in water chillers.

5. Oil separator

Function: After separating the refrigerant oil from the refrigerant in the exhaust pipe, the refrigerant oil directly enters the crankcase of the compressor, reducing the amount of oil carried to the refrigeration system and minimizing the impact on the heat transfer efficiency of the heat exchanger.

Application: Refrigeration systems with medium and low temperature ranges and long pipelines (supply and suction pipes).

6. Gas-liquid separator

Function: Before entering the compressor's suction valve, the low-temperature and low-pressure refrigerant gas separates the unevaporated refrigerant liquid in the evaporator of the refrigeration system, preventing the compressor from experiencing wet stroke (liquid hammer).

7. Drying filter

Function: It absorbs moisture from liquid refrigerant and filters contaminants and impurities from the refrigerant. It is typically installed at the refrigerant outlet of the liquid receiver and water-cooled condenser. There are several types, including those for filtering moisture, impurities, and acids.

8. Solenoid valve

Function: When the compressor stops operating, the solenoid valve closes to prevent high-pressure refrigerant from entering the low-pressure system. This prevents liquid hammer when the compressor is restarted. (This article is sourced from the Refrigeration Encyclopedia WeChat official account) Installation location: 100mm to 200mm away from the thermal expansion valve

9. Liquid reservoir

Function: When the operating conditions change or the cooling capacity needs to be adjusted, it can balance and stabilize the flow of refrigerant within the system, ensuring the normal operation of the refrigeration device. Its capacity should be able to accommodate all the refrigerant, with the maximum capacity being 80% of its container volume.

10. Oil collector

Function: In parallel systems, it is commonly used to collect the oil separated by various oil separators, ensuring the normal operation of each oil separator, and subsequently returning the oil to each compressor. (This article is sourced from the official account of Refrigeration Encyclopedia on WeChat)

11. Evaporator pressure regulator

The primary function of the evaporation pressure regulator is to maintain a constant internal pressure within the evaporator. Consequently, it opens and closes based on the load conditions of the evaporator. Pressure variations at the regulator's outlet do not affect its degree of opening or closing, as the pressure regulator is equipped with an equalizing bellows (where the area of the bellows and the valve seat are equal). The evaporation pressure regulator features a pressure gauge connection for setting the desired evaporation pressure.

12. Inspection of protective devices (inspection of high-voltage controllers)

Adjust the protection value of the high-pressure controller to a value lower than the system pressure. At this point, the control loop should protect itself; otherwise, the cause of the problem should be identified.