Refrigeration capacity can not meet the depot load requirements (low compressor efficiency)
There are two main reasons for the lack of refrigerant rotation quantity. 
One is that the refrigerant charge is not enough, at this time, it is only necessary to replenish the sufficient amount of refrigerant;
Another reason is that there are more refrigerant leaks in the system, in this case, we should first find the leaks, focus on checking the pipeline and valve connections, find out the leaks and repair them, and then charge the sufficient amount of refrigerant.
Lack of refrigeration capacity (insufficient amount of refrigerant in the system)
Insufficient amount of refrigerant in the system will directly affect the refrigerant flow into the evaporator. When the expansion valve opens too much, the expansion valve is not adjusted properly or blocked. When the refrigerant flow is large, the evaporation pressure and evaporation temperature will rise, and the temperature drop of the warehouse will be slowed down; meanwhile, when the expansion valve is too small or blocked, the refrigerant flow will be reduced, and the refrigeration capacity of the system will be reduced, and the temperature drop of the warehouse will also be slowed down. Generally, we can observe the evaporation pressure, evaporation temperature and the frost of the suction pipe to determine whether the refrigerant flow of the expansion valve is suitable. Blockage of the expansion valve is an important factor affecting the refrigerant flow, and the main reasons for the blockage of the expansion valve are ice blockage and dirty blockage. Ice blockage is because the drying effect of the drier is not good, the refrigerant contains water, and when it flows through the expansion valve, the temperature drops to below 0℃, the water in the refrigerant will become ice and block the throttle valve hole; dirty blockage is because the inlet filter of the expansion valve contains more dirt, and the refrigerant is not smoothly flowing, forming a blockage.
Refrigerant flow is too large or too small (improperly adjusted or blocked expansion valve)
Its heat transfer coefficient will be reduced, once the evaporator heat transfer tube has more refrigerant oil attached to its internal appearance. Similarly, if there is more air in the heat transfer tube, the evaporator’s heat transfer area is reduced, and its heat transfer efficiency will be significantly reduced, and the temperature of the storage room is slowed down. Therefore, the daily operation and maintenance, should pay attention to timely clear the evaporator heat transfer tube inside the appearance of oil and discharge the air in the evaporator, in order to improve the evaporator heat transfer efficiency.
Heat transfer effect decreases (evaporator in the presence of more air or freezing oil)
This is mainly because the evaporator exterior frost layer is too thick or too much dust caused by the cold storage evaporator exterior temperature is mostly lower than 0 ℃, resulting in another important reason for the slow decline of the temperature of the library is the evaporator heat transfer efficiency is low. And the humidity of the warehouse is relatively high, the moisture in the air is very easy to frost in the evaporator exterior, and even ice, affecting the heat transfer effect of the evaporator. In order to prevent the evaporator’s exterior frost layer is too thick, it needs to be defrosted on a regular basis.
The following are two simple defrosting methods:
① stop melting frost. That is, stop the compressor operation, open the door, let the temperature of the library back up, to be automatically melted frost layer, and then restart the compressor.
②Frost flushing. After moving the goods out of the warehouse, directly flush the surface of the evaporator row tube with high temperature tap water to make the frost layer dissolve or fall off. In addition to the frost too thick will lead to evaporator heat transfer effect is not good, evaporator appearance because of temporary not cleaned and dust accumulation is too thick, its heat transfer efficiency will also be significantly reduced.
Heat transfer effect decreases (evaporator exterior frost is too thick or too much dust accumulation)
Heat insulation and insulation effect is poor, poor heat insulation function is because the thickness of the insulation layer of the pipeline, warehouse insulation wall, etc. is not enough. It is mainly caused by improper selection of thickness of insulation layer when designing or poor quality of insulation material when constructing.
In addition, the construction and use process, the insulation material insulation moisture-proof function may be damaged resulting in insulation layer moisture, deformation, and even rotting, its insulation and insulation capacity decreases, the library against cold loss increases, the library temperature drop significantly slowed.
Another important reason for the loss of cold is the poor sealing function of the warehouse, there are more hot air from the air leakage into the warehouse. Generally, if the seal of the door or cold storage heat insulation wall seal at the condensation phenomenon, it means that the seal is not tight.
In addition, the frequent opening and closing of the door or more people entering the warehouse together will also increase the loss of cold storage. Should try to prevent open the door to prevent a lot of hot air into the warehouse. Of course, the warehouse into the stock frequently or into the stock is too large, the heat load increases sharply, to cool down to the delineated temperature generally takes a longer time.
Resulting in a large loss of cold (cold storage because of poor insulation or sealing function)
Cylinder liner and piston ring and other parts because of severe wear, the compressor because of temporary operation. With increased clearance, sealing function will be correspondingly reduced, the compressor’s air delivery coefficient is also reduced, the refrigeration capacity will be reduced. When the cooling capacity is less than the heat load of the warehouse, it will lead to a slow decline in the temperature of the warehouse. Can be observed by observing the compressor suction and discharge pressure roughly determine the compressor’s refrigeration capacity. If the compressor’s cooling capacity decreases, the common method is to replace the compressor cylinder sleeve and piston ring, if the replacement still does not work, other factors should be considered, and even dismantle the machine to test, to exclude fault factors.
Post time: Apr-26-2023