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The master disassembles the high-resolution atlas of the refrigeration compressor The principle of auxiliary equipment of air conditioning and refrigeration system The Secret of Counterfeit Refrigeration Compressor watermark Today, a user who came to repair a display cabinet said that the compressor of the freezer sometimes works and sometimes does not work About refrigeration compressor overload protector, we must understand these thingsCauses and harms of non-condensable gas produced by refrigeration system
First, the impact of the presence of non-condensable gases on the refrigeration system
The presence of non-condensable gas will increase the condensation pressure of the refrigeration system, the condensation temperature will increase, the compressor exhaust temperature will increase, the power consumption will increase, and the refrigeration efficiency will decrease. It affects the lubricating effect and burns the compressor motor of the refrigeration compressor when it is severe.
Second, the cause of non-condensable gas
The non-condensable gas in the refrigeration system is mainly leaked air. When the refrigerant is filled and the lubricant is filled, the outside air enters the opportunity, or the system is not tightly sealed, causing the air to enter the system. In addition, non-condensable gas may also be generated due to the decomposition of the refrigerating oil, the impure refrigerant, the decomposition after contact with dirt, and the corrosion of metal materials.
3. The main performance of non-condensable gas in the system is as follows
1. The discharge pressure and discharge temperature of the compressor increase, the pressure gauge pointer on the condenser (or accumulator) swings violently, the compressor cylinder is hot, and the condenser shell is very hot.
2. Uneven frost on the surface of the evaporator.
3. When there is a large amount of non-condensable gas, the storage temperature cannot be reduced due to the reduction of the cooling capacity of the device, the compressor runs for a long time, and even the compressor is stopped due to the operation of the high-voltage relay.
To further determine whether there is non-condensable gas in the system, the following methods can be used:
You can use the pressure gauge to measure the condensation pressure (high pressure) of the refrigeration system and compare it with the corresponding pressure under the ambient air temperature at that time (you can query with the pressure enthalpy chart). If the measured pressure is greater than the saturation pressure at ambient temperature, it means that the system contains non-condensable gas; the difference between the two can be regarded as the content of non-condensable gas.
For example: the actual measured condensation pressure of a refrigeration system R22 system is 13.2kg / cm2 gauge pressure, and the ambient temperature at that time was 35 degrees Celsius. By querying the "R22 refrigerant temperature and pressure comparison table", the corresponding pressure at a temperature of 35 degrees is 12.81kg / cm2 gauge pressure, it can be seen that the saturation pressure at this temperature is lower than the actual operating condensation pressure, indicating the existence of the system The pressure content of the non-condensable gas is: 13.2-12.81 = 0.39kg / cm2 gauge pressure.
Fourth, the method of removing non-condensable gas
First of all, prevention is the main task. Before charging the refrigerant in the refrigeration system, evacuate thoroughly.
Secondly, install a non-condensable gas separator and a discharge valve to the system to periodically or automatically discharge the non-condensable gas in the system. The method of excluding non-condensable gas varies with the air release equipment of the device.
Non-condensable gas is easy to separate naturally from the refrigerant at a low temperature and the system is at rest. Its specific gravity is smaller than that of the refrigerant. After separation, it accumulates in the high part of the system (above), so it should be selected at the lowest temperature period. The system has the longest downtime, and the discharge point at the highest point of the refrigeration system is discharged. It is also possible to open the valve directly above a container in the system for discharge, or to discharge each container separately.
Now only introduce the operation method of deflation by using the condenser deflation valve:
1. Close the outlet valve of the reservoir.
2. Turn on the compressor and press the refrigerant (and non-condensable gas) in the system into the condenser until the low-pressure relay is activated and stopped.
3. After stopping, let the condenser continue to circulate cooling water to make the refrigerant fully condense. Because the non-condensable gas is lighter than the refrigerant gas, it accumulates on the top of the condenser (some small-scale equipments have the condenser on the bottom of the compressor, in this case, they gather at the highest place in the high-pressure system).
4. Open the purge valve at the top of the condenser (or the multi-purpose through slot of the double-seat exhaust shut-off valve or the outlet of the exhaust temperature gauge socket, etc.) to release the non-condensable gas. The opening of the air release valve should not be too large. In order to judge the situation of deflation, you can use your hand to face the airflow. If you feel like the wind is blowing, it means that the gas is released; if there is oil on the hand and a cold feeling, it means that the refrigerant gas has been released. The bleed valve should be closed immediately.
Bleeding during the operation of the compressor will release a large amount of refrigerant gas, so it is not allowed. After the compressor is stopped, the bleed valve is opened without a necessary period of time. The bleed effect is very poor, and the loss of refrigerant is very large, so it should also be avoided.
Some small refrigeration devices may not have a bleed valve. At this time, you can loosen a joint on the top of the high-pressure gas line to deflate, or you can press all the refrigerant back into the refrigerant cylinder, and then cool and stand the cylinder. After the non-condensable gas is released from the cylinder, the refrigerant is charged back to the system.
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