Why does the refrigerator return tube freeze? The high probability is that these factors

Frosting on the return port of the compressor in the refrigeration system is a very common phenomenon in the refrigeration system. Under normal circumstances, system problems will not immediately occur, and slight frosting generally does not need to be dealt with. If the frosting phenomenon is serious, then the cause of the frosting first needs to be clarified.

为什么冰箱回气管结冰

1. The compressor return port is frosted

Frosting on the return air port means that the return air temperature of the compressor is too low. So what circumstances will cause the return air temperature of the compressor to be too low?

For refrigerant of the same quality, if the volume and pressure are changed, the temperature will behave differently. If the return air temperature of the compressor is low, it will generally show both low return air pressure and high refrigerant volume of the same volume. The root cause for this situation is that the refrigerant flowing through the evaporator cannot completely absorb the heat required to expand itself to a predetermined pressure and temperature value.

There are two causes of this problem:

1. The supply of liquid refrigerant in the throttle valve is normal, but the evaporator cannot absorb heat normally;

2. The evaporator absorbs heat normally, but the throttle valve has too much refrigerant supply, that is, too much refrigerant flow, which we usually understand as too much refrigerant.

2. Due to less fluorine, the return air from the compressor is frosted

1. Due to the extremely small flow rate of refrigerant

Too little refrigerant expansion will not utilize the entire evaporator area, and will only form low temperatures in local areas of the evaporator. Due to the small amount of refrigerant, the rapid expansion in some areas will cause the local temperatures to be too low, resulting in frosting of the evaporator.

After local frosting, because an insulation layer is formed on the surface of the evaporator and the heat exchange rate in this area is low, the expansion of the refrigerant is transferred to other areas, and the entire evaporator is gradually frosted or frozen, and the entire evaporator forms an insulation layer, so the expansion spreads to the compressor return pipe, causing the compressor return air to frost.

为什么冰箱回气管结冰

2. Due to the small amount of refrigerant

The low evaporation pressure of the evaporator leads to low evaporation temperature, which will gradually lead to dew condensation in the evaporator to form an insulation layer, and the transfer of the expansion point to the compressor return air will cause frosting in the compressor return air.

Both of the above points will show frosting on the evaporator before the return air from the compressor frosts.

In fact, in most cases, for frost exposure, you just need to adjust the hot gas bypass valve. Specific method: Open the rear end cover of the hot gas bypass valve, and then use the No. 8 Allen wrench to turn the adjustment nut inside clockwise. The adjustment process should not be too fast. Generally, pause after turning it for about half a turn to let the system run for a period of time. After a period of time, we will decide whether to continue the adjustment. Wait until the operation is stable and the frosting of the compressor disappears before tightening the end cover.

3. The cylinder head is frosted (in severe cases, the crankcase is frosted)

Frosting on the cylinder head is caused by a large amount of wet steam or refrigerant being sucked into the compressor. The main reasons for this situation are:

1. The opening of the thermal expansion valve is adjusted too much, and the temperature sensor is incorrectly installed or the fixing is loose, resulting in the felt temperature being too high and the valve core opens abnormally.

The thermal expansion valve is a direct-acting proportional regulator that uses the degree of superheat at the outlet of the evaporator as a feedback signal, compares it with a given degree of superheat and generates a deviation signal to regulate the refrigerant flow entering the evaporator. It integrates a transmitter, a regulator and an actuator.

Thermal expansion valves can be divided into two types according to different balancing methods: internal balanced thermal expansion valves and external balanced thermal expansion valves.

The opening of the thermal expansion valve is adjusted too much, and the temperature sensor is incorrectly installed or the fixing is loose, resulting in the felt temperature being too high and the valve core opens abnormally, causing a large amount of wet steam to be sucked into the compressor, causing frosting on the cylinder head.

If the superheat at the outlet of the evaporator is too high, the superheat section at the rear of the evaporator will be too long, and the refrigeration capacity will be significantly reduced; if the superheat at the outlet is too small, it may cause liquid strike of the compressor or even frosting on the cylinder head. It is generally believed that the expansion valve should be adjusted to the operating superheat at the evaporator outlet to 3℃~8℃.

为什么冰箱回气管结冰

2. The liquid supply solenoid valve leaks or the expansion valve does not close tightly during shutdown. As a result, a large amount of refrigerant liquid has accumulated in the evaporator before start-up. This situation can also easily cause compressor liquid hit!

3. Too much refrigerant in the system. The liquid level in the condenser is higher, the condensation heat exchange area is reduced, which increases the condensation pressure. That is, the pressure in front of the expansion valve increases, and the amount of refrigerant flowing into the evaporator increases. The liquid refrigerant cannot be completely evaporated in the evaporator. Therefore, the compressor absorbs wet steam, and the cylinder head will be cold or even frosted, which may cause “liquid hammer”, and the evaporation pressure will also be high.

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