Names, Functions and Maintenance Methods of Each Component in the Cold Storage System

2025-04-30

Compressor: It plays the role of compressing and driving the refrigerant in the refrigerant circuit. The compressor extracts the refrigerant from the low-pressure area, compresses it, and then sends it to the high-pressure area for cooling and condensation. Heat is dissipated into the air through the heat sink, and the refrigerant changes from a gaseous state to a liquid state, with an increase in pressure.
Condenser: It is one of the main heat exchange equipment in the cold storage refrigeration system. Its function is to cool and condense the high-temperature superheated refrigerant vapor discharged by the compressor of the assembled cold storage into a high-pressure liquid.
Evaporator: It absorbs the heat inside the cold storage, causing the liquid refrigerant to evaporate under low pressure and low temperature. It absorbs the heat transmitted from the cold storage and evaporates into a gaseous refrigerant. The gaseous refrigerant is sucked into the compressor for compression and then discharged into the condenser to release heat. Basically, the principles of the evaporator and the condenser are the same. The difference is that the former absorbs heat from the inside of the storage, while the latter dissipates heat to the outside.
Liquid Receiver: It stores the Freon storage tank to ensure that the refrigerant is always in a saturated state.
Solenoid Valve: Firstly, it prevents the refrigerant liquid in the high-pressure part from entering the evaporator when the compressor stops, avoids the too-high low pressure when the compressor starts next time, and prevents the compressor from liquid hammer. Secondly, when the temperature of the cold storage reaches the set value, the temperature controller acts, the solenoid valve loses power, and the compressor stops when the low pressure reaches the shutdown set value. When the temperature inside the cold storage rises back to the set value, the temperature controller acts, the solenoid valve gets power, and the compressor starts when the low pressure rises to the compressor startup set value.
High and Low Pressure Protector: It protects the compressor by preventing the high pressure from being too high and the low pressure from being too low.
Temperature Controller: It is equivalent to the brain of the cold storage, controlling the start and stop of the cold storage refrigeration, as well as the start and stop of defrosting and the fan.
Drier Filter: It filters impurities and moisture in the system.
Oil Pressure Protector: It ensures that the compressor has sufficient lubricating oil.
Expansion Valve: Also called the throttle valve, it can create a huge pressure difference between the high and low pressures of the system, causing the high-pressure refrigeration liquid at the outlet of the expansion valve to rapidly expand and evaporate. It absorbs the heat in the air through the pipe wall for heat and cold exchange.
Oil Separator: Its function is to separate the lubricating oil in the high-pressure steam discharged by the refrigeration compressor to ensure the safe and efficient operation of the device. According to the oil separation principle of reducing the gas flow rate and changing the gas flow direction, the oil particles in the high-pressure steam can be separated under the action of gravity. Generally, when the gas flow rate is below 1m/s, the oil particles with a diameter of more than 0.2mm contained in the steam can be separated. Commonly used oil separators include four types: scrubbing type, centrifugal type, packed type, and filtering type.
Evaporator Pressure Regulating Valve: It is used to prevent the evaporator pressure (and the evaporation temperature) from dropping below the specified value. Sometimes it is also used to adjust the evaporator pressure to adapt to the change of the load.
Fan Speed Regulator: This series of fan speed regulators is mainly used for the speed regulation of the fan motors of the outdoor air-cooled condensers of refrigeration equipment, or for the speed regulation of the air coolers in cold storages.
Common Fault Handling of the Cold Storage Refrigeration System

Refrigerant Leakage: After the refrigerant leaks in the system, the refrigeration capacity is insufficient, the suction and exhaust pressures are low, and a much louder intermittent "squeaking" airflow sound than usual can be heard at the expansion valve. The evaporator does not frost or has only a small amount of floating frost at the corners. If the expansion valve hole is enlarged, the suction pressure still does not change much. After the system is shut down, the internal equilibrium pressure is generally lower than the saturated pressure corresponding to the same ambient temperature.
Exclusion Method: After the refrigerant leaks, do not rush to charge the refrigerant into the system. Instead, immediately find the leakage point. After repair, fill in the refrigerant. The refrigeration system with an open compressor has many joints and sealing surfaces, and there are correspondingly more potential leakage points. During maintenance, it is necessary to pay attention to finding out the vulnerable leakage links and check according to experience whether there are phenomena such as oil leakage, pipeline breakage, and loose joints at the main leakage points.
Excessive Refrigerant Charging after Maintenance: If the amount of refrigerant charged into the refrigeration system after maintenance exceeds the capacity of the system, the refrigerant will occupy a certain volume of the condenser, reducing the heat dissipation area, resulting in a decrease in its refrigeration effect. The suction and exhaust pressures are generally higher than the normal pressure values, the evaporator does not frost firmly, and the temperature in the storage decreases slowly.
Exclusion Method: According to the operation procedure, the machine should be stopped for a few minutes, and then the excess refrigerant should be released at the high-pressure shut-off valve. At this time, the residual air in the system can also be released together.
Air in the Refrigeration System: The presence of air in the refrigeration system will reduce the refrigeration efficiency. The prominent phenomenon is that the suction and exhaust pressures rise (but the exhaust pressure has not exceeded the rated value), and the temperature from the compressor outlet to the condenser inlet increases significantly. Due to the presence of air in the system, both the exhaust pressure and the exhaust temperature rise.
Exclusion Method: After the machine is stopped for a few minutes, air can be released continuously several times from the high-pressure shut-off valve. Some refrigerant can also be appropriately charged according to the actual situation.
Low Compressor Efficiency: The low efficiency of the refrigeration compressor means that under the condition that the working conditions remain unchanged, the actual exhaust volume decreases, resulting in a corresponding reduction in the refrigeration capacity. This phenomenon mostly occurs in compressors that have been used for a long time.
Due to large wear, the fit clearance of each component is large, and the sealing performance of the air valve decreases, causing the actual exhaust volume to decrease.
Exclusion Method:
Check whether the cylinder head paper gasket is broken through and causes leakage. If so, replace it;
Check whether the high and low-pressure exhaust valve plates are not closed tightly. If so, replace them;
Check the fit clearance between the piston and the cylinder. If the clearance is too large, replace it.
Excessive Frosting on the Evaporator Surface: The frost layer on the evaporator pipeline accumulates thicker and thicker. When the entire pipeline is covered with a transparent ice layer, it will seriously affect heat transfer, resulting in the temperature inside the storage not dropping to the required range.
Exclusion Method: Stop the machine for defrosting, open the storage door to let the air circulate, or use a fan, etc. to accelerate the circulation and reduce the defrosting time. Do not knock the frost layer with iron tools, wooden sticks, etc. to prevent damage to the evaporator pipeline.
Refrigeration Oil in the Evaporator Pipeline: During the refrigeration cycle process, some refrigeration oil remains in the evaporator pipeline. After a long time of use, when there is a large amount of residual oil in the evaporator, it will seriously affect its heat transfer effect, resulting in a poor refrigeration phenomenon.
Exclusion Method: Remove the refrigeration oil in the evaporator. Remove the evaporator, blow it out, and then dry it. For those that are not easy to disassemble, you can use a compressor to blow air out from the evaporator inlet.
Unsmooth Refrigeration System: Due to the unclean cleaning of the refrigeration system, after several times of use, dirt gradually accumulates in the filter, and some mesh holes are blocked, resulting in a reduction in the refrigerant flow rate and affecting the refrigeration effect. The filters at the expansion valve and the compressor suction port in the system also have a slight blockage phenomenon.
Exclusion Method: Remove the slightly blocked components, clean and dry them, and then reinstall them.
Refrigerant Leakage: The compressor starts easily (when the compressor components are not damaged), the suction pressure is in a vacuum state, the exhaust pressure is very low, the exhaust pipe is cold, and the sound of liquid water flow cannot be heard in the evaporator.
Exclusion Method: Check the whole machine, mainly checking the vulnerable leakage parts. After finding the leakage part, it can be repaired according to the specific situation. Finally, evacuate and charge the refrigerant.
Freezing Blockage of the Expansion Valve Hole:
(1) The main components in the refrigeration system are not properly dried;
(2) The whole system is not thoroughly evacuated;
(3) The water content of the refrigerant exceeds the standard.
Exclusion Method: Connect a filter filled with a moisture absorber (silica gel, anhydrous calcium chloride) in series in the refrigeration system to filter out the moisture in the system, and then remove the filter.
Dirt Blockage at the Expansion Valve Filter Screen: When there is a large amount of relatively coarse powdery dirt in the system, the entire filter screen will be blocked, and the refrigerant cannot pass through, resulting in no refrigeration.
Exclusion Method: Remove the filter, clean and dry it, and reinstall it into the system.
Filter Blockage: The desiccant becomes pasty after being used for a long time and blocks the filter, or dirt gradually accumulates in the filter, causing blockage.
Exclusion Method: Remove the filter, clean and dry it, replace the desiccant, and install it into the system.
Refrigerant Leakage in the Expansion Valve Thermal Bulb: After the temperature-sensing agent in the expansion valve thermal bulb leaks, the two acting forces below the diaphragm push the diaphragm upward, closing the valve hole. The refrigerant in the system cannot pass through, resulting in no refrigeration. At this time, the expansion valve does not frost, the low pressure is in a vacuum state, and the sound of airflow cannot be heard in the evaporator.
Exclusion Method: Stop the machine and close the shut-off valve. Remove the expansion valve and check whether the filter screen is blocked. If not, you can blow into the expansion valve inlet with your mouth to see if it is ventilated. You can also visually inspect or disassemble it for inspection. Replace it if it is damaged.
Residual Air in the System: When there is air circulation in the system, the exhaust pressure will be too high, the exhaust temperature will be high, the exhaust pipe will be hot to the touch, the refrigeration effect will be poor. Soon after the compressor runs, the exhaust pressure exceeds the normal value, forcing the pressure relay to act.
Exclusion Method: Stop the machine and release the air at the exhaust valve hole.
Shutdown Caused by Too Low Suction Pressure: When the suction pressure in the system is lower than the set value of the pressure relay, its contacts act to cut off the power supply.
Exclusion Method: 1.
Refrigerant leakage. 2. System blockage.