The core problem of compressor oper
Will the amount of refrigerant cause frost in the return pipe and compressor
As far as air conditioners are concerned, generally speaking, the principle of system circulation is the same as that of refrigerator freezers. The symptoms of air conditioner systems are similar to those of refrigerator freezers when they lack fluorine. Under rated air-conditioning conditions, the air-conditioning system lacks fluorine and then the return pipe frost is not easy to occur. After the lack of fluorine, the return pipe temperature will only be higher than normal, that is, the return air superheat temperature is higher than normal. At this time, the common sense of the principle of refrigeration cycle, There are certain conditions for the fluorine return pipe to be able to form frost. The indoor temperature is low or the internal machine ventilation and heat exchange are poor; the ambient temperature is low and the machine runs for a long time, the evaporator starts to form frost from the entrance, and slowly becomes more and more. It is possible to fill the evaporator up to the return pipe, but it is not true that the return pipe will form frost if it is lack of fluorine.
How can the return pipe of refrigeration appliances be frosted? Under what circumstances will it be frosted? Scientific ethics and logic must be used to explain this problem.
For household air conditioners, take R22 refrigerant as an example. Its saturated gauge pressure at 0 degrees is 0.399MPa. When this pressure is lower than the corresponding temperature of 0 degrees, it is the crystallization point (freezing point) of water. Of course, the outer surface of the tube It will first dew and then frost. This is a normal physical reaction and change. Therefore, after the low pressure of the household air conditioner is lower than 0.399MPa, the connecting pipe will start to form frost.
The refrigerants used in household refrigerators and freezers are R12, R134a, R600a, etc. When the saturation pressure of R12 refrigerant is lower than 2.11kg, the saturation pressure of R134a refrigerant is lower than 0.193MPa, and the saturation pressure of R600a refrigerant is lower than 0.058MPa gauge pressure. Afterwards, its saturation temperature is 0 degrees or below. When the temperature is below 0 degrees, if more refrigerant is added to the system at this time, the refrigerant in the evaporator cannot be fully exchanged (absorbing heat) to produce boiling (evaporation) ), if the return air superheat is too small, the liquid refrigerant will enter the return air pipe or even the compressor, which will inevitably cause frosting of the return air pipe and even the compressor.
The difference in cold storage is that according to the thermal properties (physical and chemical properties) of the refrigerant used, as well as the evaporation temperature and return air superheat specified by the system, when the superheat is too small, such as the opening of the expansion valve is too large, or the system If there is too much refrigerant and the liquid level in the evaporator is too high (too much), the return air will entrain over-moist and over-humid gas, and the compressor may cause liquid shock and frost.
These are different systems. Under different refrigerants and different corresponding pressures and temperatures, different reactions occur, which are also the specific thermal conditions of the refrigeration system. This is a basic problem that is easy to understand. Don't misunderstand and confuse it!
