It is a common phenomenon that the temperature of the supermarket freezer cannot drop and the temperature drops slowly. Here is a brief analysis of the reasons for the slow temperature drop, hoping to bring some help to friends in the same industry.
1. Due to the poor heat insulation or sealing performance of the freezer, the loss of cooling capacity is large
The reason why the heat insulation performance is poor is that the thickness of the insulation layer of pipes, heat insulation boards, etc. is not enough, and the effect of heat insulation and heat preservation is not good. It is mainly caused by the improper selection of the thickness of the insulation layer during design or the poor quality of insulation materials during construction. . In addition, during the construction process, the thermal insulation and moisture-proof performance of the thermal insulation material may be damaged, causing the thermal insulation layer to be damp, deformed, or even eroded. Another important reason for the large cooling loss is poor sealing performance, and more hot air invades from the leak. Generally, if there is condensation on the sealing strip of the door or the heat insulation seal of the refrigerator, it means that the seal is not tight. In addition, frequent opening and closing of doors or more people entering the warehouse together will also increase the loss of cooling capacity. Opening the door should be avoided as much as possible to prevent a large amount of hot air from entering. Of course, when the stock is purchased frequently or the quantity purchased is too large, the heat load will increase sharply, and it generally takes a long time to cool down to the specified temperature.
2. The frost on the surface of the evaporator is too thick or there is too much dust, and the heat transfer effect is reduced.
Another important reason for the slow temperature drop is the low heat transfer efficiency of the evaporator, which is mainly caused by the thick frost layer or excessive dust accumulation on the surface of the evaporator. Since the surface temperature of the refrigerator evaporator is mostly lower than 0°C, and the humidity is relatively high, the moisture in the air is easy to frost or even freeze on the surface of the evaporator, which affects the heat transfer effect of the evaporator. Too thick for the surface frost layer of the device that prevents evaporating, need regularly it to be defrosted.
Here are two simpler defrosting methods:
① Shut down to defrost. That is, stop the compressor, open the door, let the temperature rise, and restart the compressor after the frost layer melts automatically.
②Frost. After moving the goods out of the freezer, rinse the surface of the evaporator exhaust pipe directly with tap water at a higher temperature to dissolve or fall off the frost layer. In addition to the poor heat transfer effect of the evaporator due to too thick frosting, the heat transfer efficiency of the evaporator will also be significantly reduced due to the thick dust accumulation on the surface of the evaporator due to long-term cleaning.
3. There is more air or refrigerated oil in the evaporator of the supermarket freezer, and the heat transfer effect is reduced
Once more refrigerant oil is attached to the inner surface of the heat transfer tube of the evaporator, its heat transfer coefficient will decrease. Similarly, if there is more air in the heat transfer tube, the heat transfer area of the evaporator will decrease, and its heat transfer coefficient Efficiency will also drop significantly, and the rate of temperature drop will slow down accordingly. Therefore, in daily operation and maintenance, care should be taken to remove the oil on the inner surface of the evaporator heat transfer tube and discharge the air in the evaporator in time to improve the heat transfer efficiency of the evaporator.
Improper adjustment or blockage of the throttle valve will directly affect the refrigerant flow into the evaporator. When the throttle valve is opened too large, the refrigerant flow rate is too large, the evaporation pressure and evaporation temperature will also increase, and the temperature drop rate will slow down; at the same time, when the throttle valve is opened too small or blocked, the refrigerant flow rate will increase. The cooling capacity of the system is also reduced, and the temperature drop rate of the warehouse will also slow down.
Generally, it can be judged whether the refrigerant flow rate of the throttle valve is appropriate by observing the evaporation pressure, evaporation temperature and frosting of the suction pipe. Throttle valve blockage is an important factor affecting the refrigerant flow rate, and the main causes of throttle valve blockage are ice blockage and dirty blockage. Ice blockage is due to the poor drying effect of the dryer. The refrigerant contains moisture. When it flows through the throttle valve, the temperature drops below 0°C, and the moisture in the refrigerant freezes and blocks the throttle valve hole; dirty blockage is Due to the accumulation of more dirt on the inlet filter of the throttle valve, the circulation of the refrigerant is not smooth, forming a blockage.
In addition, you can also tell customers some precautions for using the freezer:
1. The freezer for long-distance transportation should be placed for 2 hours before it can be powered on to prevent damage to the system due to excessive pressure. For the first use, let the empty cabinet run for 1 hour, and then put the items in when the temperature in the cabinet drops to the required temperature in the cabinet.
2. Items should be separated when put in. If they are crowded too tightly, it will affect the air-conditioning circulation.
3. The surrounding area of the freezer should not be close to the heat source, so as to avoid direct sunlight and affect the cooling effect.
4. During the automatic defrosting process, the temperature inside the freezer will rise in a short period of time. When the hot air outside the cabinet meets the food with a cold surface, dew will condense on the surface of the food. Most of the dew will be removed when the machine is turned on for refrigeration, and a small amount of dew will still remain on the food, which is a normal phenomenon.
5. The needle valve on the evaporator of the refrigerator is used for system testing and refrigerant filling, and should not be opened at ordinary times to prevent refrigerant leakage.
6. The freezer shall not store flammable, explosive and volatile liquids and gases.
7. The shelf structure of the freezer can bear no more than 50kg of weight per square meter (need to be evenly distributed), too much will damage the shelf.
8. The ground should not have subsidence and should be kept level, otherwise it will affect the drainage. Poor drainage will affect the normal cooling and damage the fan.
Post time: Mar-20-2023
