A brief discussion on refrigeration knowledge
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I’ve been here for a while without saying much to everyone, but seeing that you’re all very interested in refrigeration, I’ll talk about it with you today. The principle of refrigeration is as follows: during cooling, the liquid refrigerant at low temperature and pressure absorbs the heat from the medium to be cooled – whether it’s water or air – and evaporates into a gas. This gas is then drawn in by the compressor, compressed into a high-pressure gaseous state, and subsequently sent to the condenser. In the condenser, the cooling medium (water or air) facilitates heat exchange, removing the heat released by the refrigerant and causing the high-temperature, high-pressure refrigerant gas to condense into a medium-temperature, high-pressure liquid. The high-pressure liquid passes through a throttling device (capillary tube or expansion valve) and enters the evaporator, where it evaporates at a corresponding low pressure, absorbing heat from the medium to be cooled. Thus, one refrigeration cycle is completed. What I’m referring to here is compression refrigeration, not absorption refrigeration. Compression refrigeration refers to the types using R22 or R717 (ammonia) as refrigerants. If anyone has any questions related to refrigeration, feel free to ask; let’s learn together*. The above content is original – no plagiarism, haha: lol. (I hope this post can become a valuable resource on refrigeration.)
At present, China’s reforms and opening up are continuing to deepen, and the markets for industrial and agricultural products have expanded from the domestic level to the international stage. The rapid development of international trade urgently requires that the relevant standards formulated by our country be brought in line with international standards. The internationalization of standards is being actively pursued under **’s guidance by the industrial, agricultural, and trade sectors, in collaboration with research institutions and universities. At present, China has referred to some highly authoritative foreign standards to formulate **standards and technical specifications for various types of refrigeration compressors, in order to improve the performance, quality, reliability, and durability of its products and to promote rationalization at all stages of production, distribution, and use. These standards mainly include the test method standards for the performance of positive-displacement refrigeration compressors, the standards for the type, basic parameters, and technical requirements of small and medium-sized single-stage piston refrigeration compressors, the standards for hermetically sealed motors-compressors in household room air conditioners, the standards for hermetically sealed motors-compressors in household refrigerators, as well as the standards for the type and basic parameters of oil-injected single-stage screw refrigeration compressors.
Screw compressors have a long history of development, boasting extensive experience in design, manufacturing, and operation; they are still widely used and continue to evolve in various fields to this day. The continuous advancement of refrigeration compressors is also reflected in the diversity of their types. Various types of compressors other than piston-type ones, such as centrifugal, screw, rotary vane, and scroll compressors, have been effectively developed, each with its own unique features that are truly impressive. This provides technicians working in refrigeration engineering with more options when selecting refrigeration compressor types. Under such circumstances, the scope of application for piston compressors is bound to be affected, showing a trend of gradual reduction, a trend that is more pronounced in the range of low cooling capacities. However, in the range of medium and low cooling capacities, piston compressors remain the preferred choice in practice. With the continuous improvement in the reliability and durability of compressors, along with the pursuit of more compact and lightweight designs, it was only natural for refrigeration compressors to evolve from open-type to closed-type designs. In Japan, for example, over 90% of piston compressors with a power range of 15–22 kW are of semi-closed type ； For those that cannot rely on external repairs. In ships, vehicles, and remote areas, open-type compressors that facilitate on-site maintenance still have their advantages.