The compressor is regarded as the heart of the refrigeration system, and the term that best expresses the characteristics of the compressor is called "steam pump". The actual responsibility of the compressor is to increase the pressure and increase the suction pressure to the discharge pressure.
Compression ratio is a technical expression of pressure difference, which means the absolute pressure on the high pressure side divided by the absolute pressure on the low pressure side. The calculation of compression ratio must use absolute pressure value. In order to avoid negative values in the calculated compression ratio, absolute pressure, not gauge pressure, must be used when calculating the pressure ratio. The absolute pressure value can be used to make the calculated value of the compression ratio positive, which makes sense.
There are five types of compressors used in the refrigeration and air-conditioning industry: reciprocating, screw, rotary, scroll and centrifugal. The reciprocating compressor is the most widely used compressor in small and medium-sized commercial refrigeration systems. Screw compressors are mainly used in large commercial and industrial systems. Rotary compressors and scroll compressors are mainly used in household and small-capacity commercial air-conditioning devices, while centrifugal compressors are widely used in air-conditioning systems in large buildings.
Various reciprocating compressors are generally classified according to the compressor housing form and the setting mode of the drive mechanism. According to the shell type, there are open and closed semi-hermetic compressors. Closed type means that the entire compressor is arranged in a shell.
1. Compressed air as power
Compressed air is used to drive various pneumatic machinery and tools. The discharge pressure of the compressor is 0.7~0.8MPa, which is used to control instruments and their automation devices; vehicle braking, door and window opening and closing; pharmaceutical industry, brewing industry Stirring; blowing of mid-latitude sand on air jet looms; starting of large and medium-sized diesel engines; coal mining by high-pressure blasting; launching of certain weapons in the defense industry, ups and downs of submarines, torpedoes shooting and driving, and salvage of sunken ships.
2. Compressed air is used for refrigeration and gas separation
The gas is compressed, cooled, expanded and liquefied for artificial refrigeration (refrigeration, refrigeration and air conditioning), such as ammonia or freon compressors. This type of compressor is usually called "refrigerator" or "ice machine." In addition, if the liquefied gas is a mixed gas, the components can be separated separately in the separation device to obtain various gases of qualified purity. For example, after air is liquefied and separated, pure oxygen, pure nitrogen and pure other rare gases can be obtained. At present, in the petrochemical industry, the raw material gas—petroleum cracked gas is separated by first compressing and then using different cooling temperatures to separate the components.
3. Compressed gas is used for synthesis and polymerization
In the chemical industry, gas is compressed to high pressure, which often facilitates synthesis and polymerization. For example, nitrogen and hydrogen synthesize ammonia, hydrogen and carbon dioxide synthesize methanol, carbon dioxide and ammonia synthesize urea and so on. Another example is the rapid development of the polyethylene industry in the chemical industry, with a wide range of polymerization pressures, some even reaching 3,200 kg/cm².
4. The compressed gas is used for the hydrorefining of oil
In the petroleum industry, artificially heating and pressurizing hydrogen to react with oil can crack the reconstituted hydrocarbons into lighter hydrocarbons, such as the lightening of heavy oil and the hydrofining of lubricating oil.
5. Gas delivery
Compressors used to transport gas with pipelines facilitate gas transport after pressurization.