The refrigeration system of ultra-low temperature industrial refrigerators generally 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 evaporator of the cryogenic machine is directly attached to the outside of the inner box in the form of a coil, and the gap between the coil and the wall of the box is filled with thermal conductive paste to increase the heat exchange effect. The condensing evaporator is a shell-and-tube structure with four threaded copper tubes inside and adopts a countercurrent heat exchange method.

Design overview of ultra-low temperature industrial refrigerators:
1. In order to be practical, the chemical and thermal stability of the refrigerant should be good. It will not decompose or deteriorate during the refrigeration cycle. It will not corrode the materials of machinery and equipment. It will not chemically react with lubricating oil. In addition, it is safe, non-toxic and non-toxic. Harm, low flammability and explosiveness.
2. Environmental acceptability. After the refrigerant is selected according to its nature, it in turn requires the process arrangement, structural design and operation of the refrigeration system to adapt to it.
3. The reaction kettle made of stainless steel is more robust and durable, while the glass reaction kettle allows users to observe the reaction process in the kettle body.

Engine assembly is carried out in a low temperature environment below minus 30°C. The mainstream automobile engine manufacturers have their own low temperature assembly workshops. Engines assembled in a low temperature environment have good sealing properties and are not prone to oil leakage. Only in this way can they produce high Quality engine.

Typical fit of hole and shaft:
There are three types of typical fits between holes and shafts, namely clearance fits, transition fits and interference fits. In simple terms, clearance fit means that the diameter of the hole is larger than the shaft diameter, which can be assembled at room temperature. The shaft diameter of the interference fit is larger than the aperture, and the interference fit is a tighter and firmer fit. But the problem is that it is impossible for us to fit the large-diameter shaft into the small-diameter hole at room temperature. This requires the help of very hand-breaking, using the principle of thermal expansion and contraction to let the shaft shrink and expand, and then match the shaft hole. Return to normal temperature and achieve a tight interference fit.

The assembly process of an industrial low-temperature refrigerator is as follows: Take out the workpiece cooled to a low temperature from the low-temperature assembly equipment, the workpiece will not immediately return to room temperature. At this time, the heated fitting will be assembled with it, and then returned to room temperature to complete the interference. Assembled.