1-Cold storage equipment: Frost on the compressor return air port indicates that the compressor return air temperature is too low. So what will cause the compressor return air temperature to be too low?
It is well known that if the volume and pressure of the same quality of refrigerant are changed, the temperature will have different performances. That is, if the liquid refrigerant absorbs more heat, the pressure, temperature and volume of the same quality of refrigerant will be high. If the heat absorption is less, the pressure, temperature and volume will be low.
That is to say, if the compressor return air temperature is low, it will generally show low return air pressure and high refrigerant volume of the same volume. The root cause of this situation is that the refrigerant flowing through the evaporator cannot absorb the heat required for its own expansion to the predetermined pressure and temperature value, resulting in low return air temperature, pressure and volume values.
There are two reasons for this problem:
1. The throttle valve liquid refrigerant supply is normal, but the evaporator cannot absorb heat normally to supply refrigerant expansion.
2. The evaporator absorbs heat normally, but the throttle valve refrigerant supply is too much, that is, the refrigerant flow is too much. We usually understand it as too much fluorine, that is, too much fluorine will also cause low pressure.
2- Cold storage equipment: Frosting of compressor return air due to insufficient fluorine
1. Due to the extremely low flow rate of refrigerant, the refrigerant will start to expand in the first expandable space after flowing out of the rear end of the throttle valve. Most of the frost on the liquid distributor head at the rear end of the expansion valve is often caused by lack of fluorine or insufficient flow of the expansion valve. Too little refrigerant expansion will not utilize the entire evaporator area, and only low temperature will be formed locally in the evaporator. Some areas will expand rapidly due to the small amount of refrigerant, causing the local temperature to be too low, resulting in evaporator frost.
After local frost, due to the formation of an insulation layer on the surface of the evaporator and the low heat exchange in this area, the expansion of the refrigerant will be transferred to other areas, and the entire evaporator will gradually frost or freeze. The entire evaporator will form an insulation layer, so the expansion will spread to the compressor return pipe, causing the compressor return air to frost.
2. Due to the small amount of refrigerant, the evaporator evaporation pressure is low, resulting in low evaporation temperature, which will gradually cause the evaporator to condense and form an insulation layer, and the expansion point will be transferred to the compressor return air, causing the compressor return air to frost. Both of the above points will show that the evaporator is frosted before the compressor return air is frosted.
In fact, in most cases, for the frosting phenomenon, you only need to adjust the hot gas bypass valve. The specific method is to open the rear end cover of the hot gas bypass valve, and then use a No. 8 hexagonal wrench to turn the adjusting nut inside clockwise. The adjustment process should not be too fast. Generally, it will be paused after turning half a circle. Let the system run for a while to see the frosting situation before deciding whether to continue to adjust. Wait until the operation is stable and the frosting phenomenon of the compressor disappears before tightening the end cover.
For models below 15 cubic meters, since there is no hot gas bypass valve, if the frosting phenomenon is serious, the starting pressure of the condensing fan pressure switch can be appropriately increased. The specific method is to first find the pressure switch, remove the small piece of the pressure switch adjustment nut, and then use a cross screwdriver to rotate clockwise. The entire adjustment also needs to be done slowly. Adjust it half a circle to see the situation before deciding whether to adjust it.
Post time: Nov-29-2024