Refrigerator can be divided into: compression refrigerator, absorption refrigerator, steam jet refrigerator, semiconductor refrigerator. Among them, steam compression refrigerator (piston, rotary, screw, centrifugal), absorption refrigerator and steam jet refrigerator are widely used. In my country, except for a few refrigerators with large cooling capacity and special purposes, general-purpose piston, centrifugal, screw, vortex, lithium bromide absorption, steam jet refrigerator, as well as freezing, refrigeration, low-temperature testing equipment can be manufactured by ourselves.

1. Compression refrigeration
1) Screw refrigerator: simple structure, few wearing parts, long service life, high single-stage compression ratio, and there is a trend of replacing piston type in large and medium cooling capacity.
2) Piston refrigerator: relatively mature technology, high efficiency, wide operating temperature range, can be made into large, medium and small specifications of various products, is the most widely used type of refrigerator.
3) Centrifugal refrigeration machine: uses a high-speed rotating impeller to make the refrigerant gas gain kinetic energy, and then increases its pressure through a diffuser and cools it to liquefy, throttling and refrigerating. It has the characteristics of compact structure, large cooling capacity per unit, and energy regulation. The machines used for air conditioning mostly use R11 and R12 refrigerants.
2. Absorption refrigeration
The refrigerant is evaporated by the adsorption of the absorbent on the refrigerant. Commonly used are ammonia-water absorption refrigeration machine and lithium bromide-water absorption refrigeration machine, which use heat source as power, consume less electricity, operate smoothly, have fewer wearing parts, and have a large energy regulation range. It is a newly developed type of refrigeration machine.