Why should a refrigeration system be vacuumed? How to vacuum?

2021-07-23

Why do refrigeration systems emphasize vacuumization? Let's take a look at the composition of the air, as shown in the figure below: Nitrogen makes up 78% of the air; Oxygen 21%; Other gases account for 1%. So let's look at, what does the composition of the gas do to the cooling system when it enters the cooling system?

1. The effect of nitrogen on the refrigeration system

First of all, nitrogen is a noncondensable gas. The so-called non-condensable gas refers to the gas circulating in the system with the refrigerant, and does not condense with the refrigerant, and does not produce refrigeration effect.

The existence of non-condensable gas has great harm to the refrigeration system, which is mainly manifested in the increase of condensing pressure, condensing temperature, compressor exhaust temperature and power consumption. Nitrogen enters the evaporator and cannot evaporate with the refrigerant; It will also occupy the heat transfer area of the evaporator, so that the refrigerant can not be fully evaporated, and the refrigeration efficiency is reduced. At the same time, because the exhaust temperature is too high, it may lead to the carbonization of lubricating oil, affecting the lubrication effect, and burning the refrigeration compressor motor in serious cases.



2. the influence of oxygen on refrigeration system

Oxygen and nitrogen are also non-condensable gases. We have already analyzed the harm of non-condensable gases above, and we will not repeat it here. It's worth noting, however, that compared to nitrogen, oxygen has these hazards when it gets into the refrigeration system:

1. Oxygen in the air will react with the freezing oil in the refrigeration system to generate organic matter, and finally form impurities that enter the refrigeration system, resulting in dirty plugging and other adverse consequences.

2, oxygen and refrigerant, water vapor and other easy to produce the formation of acid chemical reaction, the oxidation of freezing oil, these acids will damage the refrigeration system components, damage the insulation layer of the motor; And these acid products stay in the refrigeration system, initially no problem, over time, eventually lead to compressor damage. Here's a good illustration of these issues.



3. the impact of other gases (water vapor) on the refrigeration system

Water vapor affects the normal operation of the refrigeration system. The solubility of the freon liquid is the smallest and decreases as the temperature decreases.

The most intuitive effects of steam on refrigeration systems are the following three.

1. There is water in the refrigeration system. The first effect is the throttle structure.

2, corrosion pipe water vapor into the refrigeration system, the water content of the system increases, causing corrosion and blockage of pipelines and equipment.

3, produce sludge sediment. In the process of compressor compression, water vapor meets high temperature and freezing oil, refrigerant, organic matter, etc., producing a series of chemical reactions, resulting in motor windings damage, metal corrosion and the formation of sludge deposits.

To sum up, in order to ensure the effect of refrigeration equipment and extend the life of refrigeration equipment, it is necessary to ensure that there is no non-condensable gas in refrigeration, and the refrigeration system must be vacuumed.


4. refrigeration system vacuum operation method

Here we talk about the method and process of vacuuming, because there is only household air conditioning vacuum material in hand, so the following vacuuming equipment is household air conditioning as an example, in fact, other refrigeration equipment vacuuming operation is similar, the principle is the same.

1. Before operation, check that the vacuum pump sealant pad is not damaged and the vacuum gauge pressure gauge is zero. The fluoridation tube, vacuum gauge and vacuum pump are combined together.

2. Screw off the nut at the fluoridation port from the valve, and screw the fluoridation pipe to the fluoridation port. Open the vacuum meter and then turn on the power switch of the vacuum pump to start vacuumizing. Normal system vacuum should be below -756mmHg. The vacuuming time depends on the size of the refrigeration system and vacuum pump.

3. after the completion of the evacuation operation, quickly remove the fluoride tube and vacuum gauge, and then fully open the valve.