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If the pressure of the air-conditioning water-cooled unit is too high in use, it will have a fatal impact on the compressor and even the compressor will burn out. There are many reasons for the high pressure. This paper briefly discusses the common reasons and the corresponding treatment methods.
   (I) cooling water flow is too low to reach system rating
The main manifestation of insufficient cooling water flow: the pressure difference between the inlet and outlet water becomes smaller and the temperature difference becomes larger. The cooling water flow is insufficient, the heat exchange between the refrigerant and the cooling water in the condenser is insufficient, and the heat of the refrigerant cannot be taken away, resulting in the high temperature and high pressure gas from the compressor cannot be liquefied into a low temperature and high pressure liquid, and the pressure of the compressor to the condenser pipeline is too high, It is easy to cause the pressure switch to act, and the system is shut down for protection.
There are many reasons for the lack of cooling water flow. The common ones are lack of water in the cooling water system, a large amount of air mixed in the cooling system, and the cooling pump flow is too small to match the system. The usual treatment methods are: increasing the amount of cooling water in the system; installing an exhaust valve at a high position in the pipeline to discharge the gas; replacing the cooling pump that matches the system.
(II) cooling water temperature is too high
For the chiller cooling water rated conditions are usually 30~35 ℃, high water temperature, poor heat dissipation, will inevitably lead to high condensing temperature, condensing pressure (or exhaust pressure) will certainly be too high, this phenomenon mostly occurs in high temperature summer. The reason for the high water temperature may be: cooling tower failure, such as fan belt loosening, blocking or reversal, water distributor failure, this situation will lead to high cooling water temperature, and rapid and continuous rise; high outside temperature, cooling water The heat dissipation path is short, and the amount of water that can be circulated is small. In this case, the cooling water temperature will generally be maintained at a higher level.
Usually, the main methods to deal with the above problems are: to check and repair the cooling tower fan and water distributor; to extend the cooling water circuit and increase the storage tank.
(III) condenser fouling, blockage, poor heat transfer effect
The cooling water is usually tap water, which is easy to scale when the temperature exceeds 30 ℃. In addition, the cooling tower is open and directly exposed to the air, foreign matter and dust can easily enter the cooling water system, blocking the condenser, reducing the heat exchange area, affecting the heat exchange efficiency and causing the condensation pressure to be too high.
The simplest and most direct way to solve this problem is to clean the condenser regularly. Physical descaling cleaning and chemical cleaning can be selected according to scaling and blocking.
Physical descaling method: mechanical descaling is a method of descaling the condenser of the steel cooling tube with a flexible shaft pipe washer, especially suitable for vertical shell and tube condensers.
Chemical pickling descaling method: the condenser is cleaned with a prepared weak acid descaling agent to make the scale fall off and improve the heat transfer efficiency of the condenser.
Mixing non-condensable gas in (IV) system
The non-condensable gas in the system mainly refers to the air intruding through various channels. Although these non-condensable gases circulate in the system together with the refrigerant, they cannot be liquefied under the working pressure and temperature conditions of the unit, and finally remain in the condenser. When there is too much non-condensable gas in the device, the heat transfer performance of the condenser and evaporator will deteriorate, and the condensing pressure and exhaust temperature will be too high.
The discharged non-condensable gases can be discharged directly to the atmosphere through the purge valve at the top of the condenser or accumulator, and some refrigerant will inevitably be lost during the venting.
Excessive (V) refrigerant
The volume ratio of the refrigerant in the air conditioning system has certain requirements. Excessive refrigerant increases the compressor load and the compressor current is large. Too much refrigerant affects its own heat dissipation effect, and the condensing temperature and pressure will increase accordingly. When there is too much refrigerant and the liquid in the evaporator cannot be completely evaporated, the liquid refrigerant will be sucked back into the compressor, causing "liquid hammer" phenomenon, which will damage the valve plate and even burn the motor in severe cases. Therefore, the amount of refrigerant in the system must not be excessive.
Too much refrigerant treatment method is to recover or discharge part of the refrigerant until the amount of refrigerant is adjusted to the best effect of the system.