What is the development of co2 as a refrigerant?
In the late 19th century to the 1930s, CO2 (R744), ammonia (R717), SO2 (R764), and methyl chloride (R40) were widely used.
In 1850, it was originally proposed by the American Alexander Twining to use CO2 as a refrigerant in a vapor compression system and it obtained a British patent.
In 1867, Thaddeus SCLowe successfully used CO2 for commercial machines for the first time and obtained a British patent.
In 1869 he made an ice machine.
In 1882, Carlvon Linde designed and developed a refrigerator using CO2 as a working fluid for FKrupp in Essen, Germany.
In 1884, W Raydt designed the CO2 compression ice-making system and obtained British Patent No. 15475. J Harrison from Australia designed a CO2 plant for refrigeration and obtained the British patent No. 1890.
In 1886, the German CO2 compressor designed by Franz Windhausen was granted a British patent. The British company J&EHal acquired the patent, improved it and started production in 1890. In the 1890s, the United States began to use CO2 for refrigeration.
In 1897 KroeschelBros Boiler Company established a branch in Chicago to produce CO2 compressors.
Before and after 1919, CO2 refrigeration compressors were widely used in comfort air conditioners.
In 1920, CO2 was used in church air conditioning systems.
In 1925, the dry ice cycle was used for air conditioning.
In 1927, CO2 was used in the office's air conditioning system.
In 1930, CO2 was used in residential air-conditioning systems. It was later used in various commercial buildings and public facilities for air conditioning and refrigeration systems.
CO2 refrigeration has reached a very brilliant level.According to statistics, of the 356 ships worldwide in 1900, 37% used air circulation refrigerating machines, 37% used ammonia absorption refrigerating machines, and 25% used CO2 vapor compression refrigerating machines. In 1930, 80% of ships used CO2 chillers and the remaining 20% used ammonia chillers. Due to the poor technical level at that time, the lower critical temperature (31.1°C) and higher critical pressure (7.37MPa) of CO2 made the CO2 system less efficient. In addition, the cooling medium of the condenser mostly uses groundwater or seawater with lower temperature, which basically belongs to the subcritical cycle. When the water temperature is high (such as the temperature of the cooling water of a ship traveling on the tropical sea can be close to 30 °C), its cooling efficiency will be even lower. Therefore, CO2 refrigeration technology has not been further developed for use in automotive air conditioners, heat pumps, etc.
In 1931, CFC refrigerant represented by R12 was quickly replaced by CO2 in safe refrigerants because of its non-toxic, non-flammable, non-explosive, non-irritating, moderate pressure, and high refrigeration efficiency. In the position, CO2 is no longer being used as a refrigerant.
Re-emphasis on CO2 refrigerant
Due to the adverse effects of CFCs on the warming of the ozone layer and the atmosphere, the protection of the environment and the realization of replacement of CFCs have become common concerns of the world. From the 1985 Vienna Convention for the Protection of the Ozone Layer to the Montreal Protocol of 1987 and the amendments to the Montreal Protocol at the London Conference in 1990 and the Copenhagen Conference in 1992, the process of substitution of CFCs worldwide has been accelerating. In June 1991, China signed the revised "Montreal Protocol" and became one of the contracting states. The “China Ozone Depletion Phase-out National Programme” was compiled from May to July 1992 and approved by the State Council in January 1993. In this way, the phase-out of ODS has become an international responsibility in accordance with national programmes. The primary reason for the replacement of CFCs is because they destroy the ozone layer, so new alternative working fluids must have no damage to the ozone layer. HFC-type working fluids, because they have no destructive power to the ozone layer, have become an important medium for replacing CFCs. In particular, HFC134a has been produced and used on a large scale as a replacement for CFC12. Although HFCs do not destroy the ozone layer, they are chemically stable and can accumulate after release, which ultimately leads to a significant greenhouse effect. Although one can work hard to synthesize better working fluids, due to the large amount of refrigerant used, a considerable part will eventually inevitably leak into the atmosphere. Any discharge of a large amount of synthetic materials into the natural world will have an impact on the environment. Therefore, a common view nowadays is the use of natural working fluids. Former chairman of International Refrigeration Society, Norway's G?rentenzen promoted the use of natural working fluids from 1989 to 1994, especially for the study and promotion of CO2. Since then, the research and application of CO2 refrigeration devices have once again become a hot spot in the world.