Why does the refrigeration system of a cold storage emphasize the need for vacuum pumping?
Let's first take a look at the composition of air, as shown in the following figure. Nitrogen accounts for 78%, oxygen accounts for 21%, and other gases account for 1%. What are the effects of these gas components on the refrigeration system after entering it?Piston type Compressor Unit
The impact of nitrogen in the air on the system:
Firstly, we need to know that nitrogen is a non condensable gas. The so-called non condensable gas refers to the gas circulating in the system with the refrigerant, not condensing with the refrigerant, and not producing a refrigeration effect.Screw type Compressor Unit
The presence of non condensable gases poses great harm to refrigeration systems, mainly manifested in the increase of system condensation pressure, condensation temperature, compressor exhaust temperature, and power consumption. Nitrogen enters the evaporator and cannot evaporate with the refrigerant; It will also occupy the heat exchange area of the evaporator, preventing the refrigerant from fully evaporating and reducing the refrigeration efficiency; At the same time, high exhaust temperature may cause carbonization of lubricating oil, affecting lubrication efficiency, and in severe cases, burning out the refrigeration compressor motor.
The impact of oxygen in the air on the system:
Oxygen, like nitrogen, is also a non condensable gas. We have already analyzed the hazards of non condensable gases, and we will not repeat them here. However, it is worth noting that compared to nitrogen, if oxygen enters the refrigeration system, there are still these hazards:
Oxygen in the air will react chemically with the refrigeration oil in the refrigeration system to produce organic compounds, which eventually form impurities and enter the refrigeration system, causing adverse consequences such as dirt and blockage.Air Cooled type Condenser Unit
Oxygen can easily react with refrigerants, water vapor, and other substances to form acids, causing oxidation of the refrigeration oil. These acids can damage various components of the refrigeration system and damage the insulation layer of the motor; At the same time, these acid products will remain in the refrigeration system without any problems at first, but over time, they will eventually cause damage to the compressor. The following image illustrates these issues very well.Water Cooled type Condenser Unit
The impact of other gases on the refrigeration system:
Water vapor affects the normal operation of refrigeration systems, with the smallest solubility in Freon liquids, and the solubility gradually decreases as the temperature decreases. The most intuitive effects of water vapor on refrigeration systems are as follows, which we will illustrate in graphic form:
There is water in the refrigeration system, and the first impact is on the throttling structure. When water vapor enters the throttling mechanism, the temperature rapidly decreases and the water reaches the freezing point, causing ice to form, blocking the small through-holes of the throttling structure and causing ice blockage.Evaporator Unit
Corrosion of pipeline water vapor entering the refrigeration system increases the water content of the system, causing corrosion and blockage of pipelines and equipment.Mobile Cold Room
Generate sediment and sludge. During the compression process of the compressor, water vapor encounters high temperatures and produces a series of chemical reactions with refrigeration oil, refrigerant, organic matter, etc., resulting in damage to the motor winding, metal corrosion, and the formation of sludge deposits.Refrigeration Project and Construction
In summary, in order to ensure the effectiveness of refrigeration equipment and extend its lifespan, it is necessary to ensure that the refrigeration system is free of air. Therefore, the correct method is to exclude air from the system. In the practical application process of refrigeration systems, deposits and corrosion can cause blockage and failure of expansion valves, filter dryers, and filters. The only reliable way to remove water vapor from the air in the refrigeration system is to take the correct operating steps and use a deep vacuum pump.
For newly installed units, a vacuum pump must be used to vacuum the entire refrigeration system. It is not allowed to use the compressor of this unit to vacuum the system, otherwise it may cause irreparable damage to the compressor.
