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Water and Freon cannot dissolve each other, so when the refrigeration system contains moisture, when passing through the expansion valve or capillary , the saturation temperature decreases and freezes to form an ice blockage, which affects the normal operation of the refrigeration system. In addition, moisture in the system will accelerate metal corrosion.
1. The refrigeration system has moisture treatment methods
1. Nitrogen heating and purging
Many refrigeration people encounter water in the system. The most basic method they use is to purge the pipes with nitrogen. This method can also be used, but it cannot completely eliminate the water in the system. Here we recommend an enhanced purging method; use heated nitrogen to remove water from the system.
The specific operation is as follows:
- Prepare several bottles of nitrogen;
- Use copper pipes to make a heating section;
- Connect nitrogen bottles , heating tube , and refrigeration system;
- Open the nitrogen bottle, purge the pipe, and use oxygen acetylene to heat the heating section;
- use hot nitrogen to purge the pipe, and increase the nitrogen pressure appropriately
The advantage of using hot nitrogen is that it can heat the moisture in the system and turn it into water vapor, which is easy to discharge from the system. If the refrigeration system is relatively large, it is recommended to use segmented purging. For components such as expansion valves, liquid reservoirs, and gas-liquid separators, they can be baked in a high-temperature oven to remove moisture.
2, vacuum dehumidification
Vacuum dehumidification is a method of using vacuum pump to dehumidify the refrigeration system. There are two states of moisture in the system: steam and liquid; when the moisture is in the steam state, it is easy to remove, while in the liquid state, it is more difficult to remove. The specific operations of
are as follows:
- uses a large-capacity vacuum pump to drain the equipment at multiple lower locations of the equipment at the same time;
- heats the equipment to give more heat without damaging the equipment;
- raises the temperature to warm and vaporizes water into water vapor, making it easier to pump out the system.
3. Operational dehumidification
The method of operational dehumidification is to run the refrigeration system and use an external removable drying filter barrel to dry the moisture in the system. The dryer is generally a pressure-resistant cylinder with drying agents inside, such as silica gel , anhydrous calcium chloride, activated aluminum, etc. The dryer is generally installed in parallel with the filter on the pipeline from the liquid storage cylinder to the thermal expansion valve . It is only used within a few days after the refrigerant is charged and the filter is turned off to allow the moisture in the system to be absorbed in the dryer. After normal operation, only the refrigerant is generally allowed to pass through the filter. If the dryer and filter are put together, they become drying filter .
The operation method is as follows:
- Connect the external drying filter barrel to the system, and replace the desiccant after running for several hours;
- At the same time, observe the operating parameters of the unit and pay attention to the operating sound of the compressor . If the drying filter is cold, the expansion valve is frosted, and there is a pressure difference of more than 0.5 kg before and after the return air filter, the unit should be stopped immediately;
- then repeat the above work to continuously replace the desiccant. The interval can be gradually lengthened with the number of times; judge based on the principle of water absorption and discoloration of the desiccant.
2. Moisture treatment case
Failure phenomenon: A certain refrigeration system is equipped with heat recovery for both medium and low temperature systems. In order to prevent the condensation pressure from being too low in winter, the air inlet, liquid outlet, water inlet and return of the heat recovery were closed. Shortly after opening the water valve and air valve in March, I found water droplets and mist on the sight glass of the unit liquid storage tank . I realized that the heat exchanger was leaking, and immediately closed all valves.
Solution: First close all unit compressor suction and exhaust valves and oil valves, take out the filter core of the liquid supply system and the filter core of the air return system, use gauze to make a filter-sized bag, put water-absorbent silica gel into the filter barrel. Start the operation so that the refrigerant can circulate. If the expansion valve is found to be blocked by ice, you can use hot water or hot air to blow it open. And replace the silica gel repeatedly every 2-4 hours to absorb the moisture in the system. After the overall operation is normal, replace the refrigeration oil , oil filter and liquid supply and return air filter element . If necessary, replace it twice.
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