Why does the air conditioner evaporator frost?

Why does the air conditioner evaporator frost?

Air conditioner evaporator frost, this is a relatively common phenomenon in the refrigeration world, but also more attention to a technical problem. Why does the air conditioner evaporator frost?

The reason for evaporator frost is low evaporation temperature & insufficient evaporator heat exchange (one or the other). Summarised, it could be due to the following 8 reasons:

① Insufficient air supply, including blocked air ducts, blocked filters, blocked fin gap, fan does not rotate or lower speed, resulting in insufficient heat transfer, evaporative pressure, evaporative temperature;

② heat exchanger itself, heat exchanger common use, heat transfer performance decline, so that the evaporating pressure is reduced;

③ external temperature is too low, civil refrigeration is generally not less than 20 ℃, refrigeration in a low-temperature environment will cause insufficient heat transfer, low evaporative pressure;

④ expansion valve is gambling plug or control the opening of the pulse motor system damage, long-term operation of the system, some debris will be blocked in the mouth of the expansion valve so that it can not work properly, reducing the refrigerant flow, so that the evaporative pressure is reduced, the opening of the control is out of order will also cause a reduction in the flow, the pressure is reduced;

⑤ secondary throttling, pipe bending or clogging of sundries inside the evaporator, resulting in secondary throttling, so that the part after the secondary throttling appears to have lower pressure and lower temperature;

⑥ poorly matched system, accurately evaporator is smaller or compressor working condition is too high, in this case, even if the evaporator performance is fully exerted, due to the compressor working condition is too high will cause suction pressure is low, the evaporation temperature drops;

(7) lack of refrigerant, evaporative pressure is low, evaporative temperature is low.

(8) too much refrigerant, many people think that too much refrigerant evaporating pressure rise will not produce frost, but too much refrigerant, excess refrigerant is basically in the liquid state in the condenser after the section to the expansion valve before the pipeline, this time the system cycle slows down, liquid subcooling increases, the expansion valve opens up less, evaporating temperature is reduced, too much refrigerant back to the temperature of the tube is a negative value of the situation.