Expansion valve debugging precautions

Update:22-12-2018
Summary:

If the expansion valve outlet pressure is too low, the […]

If the expansion valve outlet pressure is too low, the corresponding evaporation pressure and temperature are too low. However, due to the decrease in the flow rate into the evaporator, the pressure is reduced, the evaporation rate is slowed down, the cooling capacity per unit volume (time) is decreased, and the cooling efficiency is lowered. Conversely, if the expansion valve outlet pressure is too high, the corresponding evaporation pressure and temperature are too high. The flow rate and pressure entering the evaporator are increased. Due to the excess evaporation of the liquid, the over-exhausted gas (or even the liquid) is sucked by the compressor, causing the wet stroke (liquid blow) of the compressor, causing the compressor to malfunction, resulting in a series of work. Bad conditions, even damage the compressor. Therefore, the opening degree of the expansion valve should be adjusted according to the library temperature at that time, that is, adjusted under the pressure corresponding to the reservoir temperature.

The expansion valve must be carefully and patiently adjusted. The pressure must be exchanged between the evaporator and the reservoir to create a heat exchange boiling (evaporation) and then through the pipeline into the compressor suction chamber to reflect the pressure gauge. It takes a time. Each time the expansion valve is mobilized, it usually takes 10~15 minutes before the adjustment pressure of the expansion valve can be stabilized on the suction pressure gauge, and the adjustment cannot be performed too quickly. The suction pressure of the compressor is the main parameter for adjusting the pressure of the expansion valve.

It is often prone to failures such as clogging of the filter screen and leakage of the temperature sensitive agent. The adjustment reaction is not sensitive, the regulation is out of control or cannot be adjusted. When frost is formed at the inlet of the expansion valve (or the valve cover is also frosted), the temperature of the inlet pipe is lower than normal temperature and even condensation; the suction pressure of the compressor is lower than the corresponding pressure at the storage temperature, the machine operating temperature And the exhaust temperature is high, the cooling temperature drops slowly or can not fall, mostly the filter screen of the expansion valve is blocked, or the dirty plug is blocked.

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