Ultra-low temperature refrigerators are also known as ultra-low temperature freezers, ultra-low temperature storage boxes, etc. Generally, there are two types of boxes: horizontal and vertical. The inner box is generally divided into multiple layers, and each layer is designed with an inner door that can be opened and closed independently. Refrigerants now generally use environmentally friendly refrigerants to meet environmental protection requirements.
The common ultra-low temperature refrigerators are 40-degree low-temperature refrigerators, 60-degree low-temperature refrigerators, and 80-degree low-temperature refrigerators. The maintenance and working principles of ultra-low temperature refrigerators are similar. When the power is turned on, when the panel shows that the temperature is higher than the set temperature, the stage compressor starts first, and the stage refrigeration system starts to work, so that the condenser temperature of the second stage refrigeration system drops, that is, the temperature of the refrigerant in the second stage drops.
After a delay of a few minutes, the second-stage refrigeration system also starts to work, and its evaporator is on the inner wall of the refrigerator, which can make the temperature inside the refrigerator drop a lot, and all the heat released by its condenser is absorbed by the evaporator of the first-stage refrigeration system. , the heat released by the stage condenser is dissipated into the air.
When the internal temperature of the refrigerator reaches the set temperature, the resistance of the temperature sensing probe transmits the information, the control relay loses power and disconnects, and the two-stage refrigeration system stops working. When the temperature in the ultra-low temperature refrigerator rises again and exceeds the set temperature, the ultra-low temperature refrigerator repeats the above operation process again, so that the temperature in the refrigerator is always kept around the set temperature. Knowing the working principle of the ultra-low temperature refrigerator can guarantee the maintenance of the ultra-low temperature refrigerator. When repairing the ultra-low temperature refrigerator, you can check and deal with it according to its working principle.
The refrigeration system of the ultra-low temperature refrigerator basically adopts the working principle of cascade refrigeration, and two fully enclosed compressors are used as high and low temperature compressors. The copper tube of the low temperature evaporator is directly attached to the outside of the inner box in the form of a coil, and the gap between the coil and the box wall is filled with thermal conductive glue to increase the heat exchange effect. The condensing evaporator is a shell-and-tube structure, with four-pipe threaded copper tubes inside, and a counter-flow heat exchange method is adopted.
The low-temperature stage system is also equipped with a gas heat exchanger, which enables the low-pressure gas from the evaporator to exchange heat with the high-pressure gas before entering the condensing evaporator, which not only reduces the heat load of the condensing evaporator, but also makes full use of the heat. Most of the filters use wax-removing filters, the purpose of which is to effectively eliminate paraffin in the refrigeration oil to reduce the possibility of "oil blockage" in the system. In addition, the ultra-low temperature refrigerator can also be equipped with some accessories according to different uses.
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