Modern refrigeration technology was developed in the late18th century.
Before that, people knew how to use cold a long time ago.
In ancient China, people used natural ice to store food and prevent heatstroke and cool down.
In his book "Travels of Marco Polo", Kyle Polo gave a detailed introduction to China's refrigeration and the method of making an ice house.
1755, Coulomb, a chemistry teacher in Edinburgh, used ether evaporation to freeze water.
His student Braque explained the phenomena of melting and gasification in essence, put forward the concept of latent heat and invented the ice calorimeter, which marked the beginning of modern refrigeration technology.
In general refrigeration, the inventor Polkins made the first vapor compression refrigerator with ether as working medium in 1834, and formally applied for British patent No.6662.
This is the prototype of all later vapor compression refrigerators, but the working medium used is ether, which is easy to burn.
In 1875, Cali and Linde used ammonia as refrigerant, and from then on, vapor compression refrigerators began to dominate.
During this period, the phenomenon that adiabatic expansion of air will significantly reduce the air temperature began to be used for refrigeration.
1844, Dr. Koryo established an air conditioning station for patients with closed circulating air refrigerator, which made him famous at one fell swoop.
William Simmons introduced the regenerator into the air refrigerator to improve the performance of the refrigerator.
1859, Carrey invented the ammonia absorption refrigeration system and applied for the principle patent.
In about 19 10, Mahlis Leblanc invented the steam jet refrigeration system.
In the 20th century, refrigeration technology has made greater development.
Fully enclosed refrigeration compressor has been successfully developed (General Electric Company, USA); Miriger discovered freon refrigerant and used it in vapor compression refrigeration cycle and mixed refrigerant application; The invention of regenerative dehumidifier cycle in Bernington and the appearance of heat pump promoted the development of refrigeration technology.
At low temperature, in 1877, Calit liquid oxygen; 1895 Linde liquefied air and established air separation equipment; 1898, Dewar precooled hydrogen with liquid air, and then changed hydrogen into liquid by adiabatic throttling, and the temperature dropped to 20.4 K; 1908, Kamelin Annas precooled helium with liquid air and liquid hydrogen, and then liquefied helium with adiabatic throttling to obtain a low temperature of 4.2K.
Dewar bottle, invented by Dewar in 1892, is used to store cryogenic liquid, which provides important conditions for research in cryogenic field.
1934, Kapicha invented the helium liquefier, which first cooled helium with an expander and then liquefied it with adiabatic throttling. In 1947, Collins used a double expander to precool helium.
At present, most helium liquefiers adopt expanders, which have been widely used in the development and practical use of refrigeration technology.
The invention of a new cooling method expands the range of low temperature and enters the field of ultra-low temperature.
Debye and Jiao Ke proposed the method of adiabatic demagnetization with paramagnetic salt in 1926 and 1927 respectively, and the low temperature obtained by this method has now reached (1×10-3 ~ 5×10-3) k; The method of nuclear adiabatic demagnetization proposed by Kuti and Simon can reduce the temperature. Couty obtained 20× 10-3K at 1956.
The dilution refrigeration method of 3He-4He mixture proposed by London in 195 1 and developed in 1965 can reach 4×10-3k; The method proposed by Pomerancek in 1950 achieves 1× 10-3k by adiabatic curing of compressed liquid 3He.
The recent development of refrigeration technology is mainly due to the worldwide demand for food, comfort and health, as well as aerospace technology, national defense construction and scientific experiments, which made this technology develop rapidly in the second half of the 20th century.
With the penetration and promotion of technological progress in microelectronics, computers, new raw materials and other related industries, refrigeration technology has made some breakthrough progress, but it is also facing new challenges.
The breakthrough lies in:
(1) Application of Microelectronics and Computer Technology
The wave of "mechatronics" has greatly promoted refrigeration technology.
Basic research: Computer simulation of refrigeration cycle started at 1960.
At present, there are various cycles in the field of general cooling and low temperature, such as: coke soup throttling refrigeration cycle (J-T cycle), Stirling refrigeration cycle, Willimir cycle (VM cycle), Gifford-McMahon cycle (G-M cycle), Solvin cycle (SV cycle), inverse Brayton cycle, pulse cycle, absorption refrigeration cycle and thermoelectric refrigeration cycle; Various cycles using acoustic refrigeration, optical refrigeration and chemical refrigeration; As well as various new mixed cycles, such as small pulse tube refrigerator cycle driven by thermoacoustic Stirling engine, computer simulation technology is widely used in cycle research.
The thermophysical process of refrigeration system, the steady and transient characteristics of system and components, the properties of single working medium and mixed working medium are studied. , but also inseparable from the application of microelectronics and computer technology.
In the design and manufacture of refrigeration products, computers have been widely used in CAD and CAM.
For example, the finite element method and finite difference method of computer-controlled structural parts design and precision machining.
The biggest influence of computers and microprocessors on refrigeration technology lies in the development of advanced automatic control systems.
This is a comprehensive technology involving advanced control methods, reliable integrated chips, special control modules and excellent sensors.
At present, it is very common to use computer control in refrigeration system, and the control mode is changing from simple mechanical control to comprehensive control, which is helpful to improve product performance.
(2) Application of new materials in refrigeration products
Ceramic and ceramic composite materials (such as fused timely, stabilized zirconia, titanium boride, silicon oxide, etc.). ) has a series of excellent properties: lighter than steel, good strength and toughness, wear resistance, low thermal conductivity and high surface finish.
The performance of parts can be improved by infiltrating ceramics into sol by sintering or using ceramics as glaze on the surface of parts.
Polymer materials (engineering plastics, synthetic rubber and composite materials) are used as electrical insulation materials and vibration damping components in refrigeration products.
And hose material; Using the thermoplasticity of polymer materials, complex parts (rotor, valve plate, etc. ) manufactured by new technology and heat setting method.
The application of these new materials has brought about the improvement of product performance and life and the reduction of cost.
(3) the development of mechanical equipment
In order to meet all kinds of refrigeration needs, new products are constantly introduced and the degree of commercialization is constantly improving.
The compressor develops from reciprocating to rotary, with the goal of high efficiency, reliability, low vibration, low noise, simple structure and low cost.
Such as new screw compressor, scroll compressor compressor and cycloidal compressor, all have excellent characteristics and competitiveness.
On the compressor drive device, frequency converter is used to drive the air conditioner, heat pump and central refrigeration system at variable speed, which brings energy-saving effect.
In the aspect of low-temperature mechanical equipment, although the various low-temperature cycles mentioned above have long been proposed, the products produced and developed in recent years have made great progress in temperature, refrigeration capacity, start-up speed, reliability, energy consumption and volume.
At present, most helium liquefiers are expansion type, the medium-sized ones are Collins machines composed of double expanders, and the large ones use turboexpanders.
Radiation refrigeration and solid-state refrigeration have been applied in practice.
The cryogenic refrigerator based on 3He-4He mixed dilution refrigeration principle has been commercialized and can be used as the precooling equipment of magnetic refrigerator.
Various gas separation equipment, heat exchangers and cryostats have also made great progress in efficiency, compactness and reliability.
(4) Working medium
After the mixed refrigerants of Freon and * * *, due to the oil crisis of 1970, the energy-saving consciousness was put in an important position, and a series of non-* * boiling refrigerants were dramatically developed in the development of new refrigerants, which achieved the energy-saving effect and met some specific needs.
Due to ozone depletion and greenhouse effect, serious environmental problems have been caused, which led to the global ban on CFCs in the late 1980s, and then spread to HCFC, which is both a historic impact and a new development opportunity.
In recent years, the development of alternative refrigerants and the research results of their thermophysical properties are proof.
When the working fluid is at a very low temperature, its quantum characteristics become very important, and its quantum effect must be considered. At this time, the performance coefficient and refrigeration capacity of the cycle are different from the classical expression and need to be obtained through the study of quantum thermodynamic cycle.
Refrigeration and cryogenic technology are dynamic disciplines and industrial fields.
The huge market growth potential and the cross penetration of new technologies have opened up a broad development world for it.
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Development history of refrigeration and air conditioning
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In the 1960s and 1970s, there was a rare dry weather in the United States. In order to solve the problem of cold and heat sources of air conditioning in arid and water-deficient areas, the United States took the lead in developing air-cooled chillers, replacing cooling towers with air heat dissipation. Its English name is: Air cool Chiller, or Chiller for short!
In the history of air-conditioning, the United States has developed and improved the central unit air-conditioning system with air ducts, and has received strong support from air-conditioning equipment dealers and distributors who are installing and maintaining the unit air-conditioning system with air ducts on site.
WRAC is the simplest and cheapest system, which can be easily purchased in retail stores and installed by itself when the continuous high temperature comes.
At the same time, SRAC without air ducts and special purpose acquisition companies have been developed and perfected in Japan since 1970s, driven by different American markets.
After that, the equipment design and manufacturing technology was transferred to China in 1990s, through joint venture with local companies (including local manufacturers of major components such as compressors, heat exchangers, electric actuators, fine valves and electronic controllers).
In the 1990s, China also absorbed the advanced technology of large air-conditioning equipment from other advanced countries and established joint ventures with most large American companies.
Today, China is a top country, and its major local factories and joint ventures produce a large number of SRAC and special purpose acquisition companies to meet the growing domestic market and export demand.
In the past few years, Japan has been exporting SRAC and special purpose acquisition company products to China, Europe and the Middle East to open up new markets.
However, China is now the largest exporter of air conditioners. In 200 1 year, the total export volume of WRAC, SRAC and special purpose acquisition companies reached 5 million units, and it is estimated that 7.5 million or 8 million units will be exported in 2002, while Japan is losing its export status.
Review by country:
++++USA
The United States is the largest air-conditioning market, accounting for 28% of the total sales of air-conditioning equipment in the world, and most of them are unit air-conditioning systems with air ducts.
The proportion of heat pumps is relatively low, with 200 1 accounting for 20% in quantity and 30% in sales.
There are some obvious reasons for the difference between American air-conditioning market and other countries:
Most people live in suburban detached houses with vast space. For the comfort of the whole indoor space, it is more convenient to install air ducts.
Energy prices are relatively low, electricity and gas can be supplied nationwide, and gas stoves can be used for heating through natural gas pipe networks in winter.
Most land is not suitable for heat pump without auxiliary electric heating in cold weather in winter, and auxiliary electric heating is not economical.
A strong network of industrial distributors and economic agents promotes the central air conditioning system with air ducts, which has relatively low installation cost and provides delayed maintenance support.
++++Japan
Household air conditioners began to be produced locally by WRAC or imported from the United States in the 1960s. Because most people live in the living area and only have strong requirements for air conditioning in a single room, central system is generally not used to save expensive electricity bills.
However, many people complain that high running noise and vibration are unacceptable in the bedroom.
At the same time, it is not convenient to install in the room.
After the painful experience of WRAC, SRAC was later developed into indoor wall-mounted installation, which made the room air conditioning unit run quietly and install conveniently.
Functionally, although SRAC has lost the functions of fresh air intake and return air exhaust, the single room air conditioners of WRAC and SRAC are almost the same in the presence of people.
In the buyer's market, additional small SRAC units are needed, which are characterized by low noise and can be easily installed as "additional units" in the bedroom.
Heat pump type can be well accepted by people in cooling and heating seasons.
Some features, such as lower noise, more sufficient heating capacity, lower power consumption (i.e. higher efficiency), smaller unit size or improved indoor air distribution, attract users' attention and interest.
Because the energy cost is cheaper than electricity and the heating capacity is higher at lower ambient temperature, kerosene stoves are still widely used to heat indoor space.
However, SRAC heat pump is an indispensable use for many people in the bedroom. It can not only run safely, but also prevent fire, because the indoor temperature is low and the room space is good when sleeping.
Lifestyle has changed, from opening doors and windows so that you can breathe fresh air when you sleep to closing doors and windows with locking devices for urban safety, which requires buying more SRAC units indoors.
Forced fans are installed indoors to suck in fresh outdoor air and exhaust indoor air, and heat exchange elements are used to achieve the purpose of energy saving.
The breakthrough technology involved in the 1980s solved the inherent shortcomings of heat pumps and promoted the sales of SRAC units.
In discount stores, such as white goods, including the main cost of sending and installing, has triggered a price war.
The installation of SRAC is very simple and fast, and people with low technical level on site can complete the installation, refrigerant piping and wiring of the unit within a few hours.
In the past, there were some quality problems, such as refrigerant leakage, component failure and comprehensive failure, which were directly related to factory maintenance or subcontracting maintenance units.
Now with the improvement of product reliability, after-sales maintenance calls are greatly reduced.
However, the business form is still the same as before. SRAC is sold through discount stores with low cost, and after-sales service is directly undertaken by the manufacturer or its sub-contracted maintenance unit.
The sales of special purpose acquisition companies are similar to SRAC's light commercial market.
Manufacturers are more engaged in the sales of so-called "multi-purpose acquisition company systems in buildings", contact air conditioning system designers and mechanical contractors, and maintain high added value with manufacturers.
1 The special-purpose acquisition company that combines compression and condensation units with multiple indoor units is increasingly popular in newly-built houses with refrigerant pipes installed on the walls.
* * * Public utilities (such as electricity and gas) and units responsible for formulating national energy policies are subsidizing the development of new technologies and promoting the installation of new air-conditioning systems with attractive plans.
These products include commercial energy-saving heat pumps, GHP and direct gas absorption refrigerators.
The benefits of discounted energy prices make users willing to install new energy-saving air conditioning systems or use them for technological transformation at a much lower operating energy cost.
In this way, even if the initial cost increases, the investment recovery is still very attractive.
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Development events of refrigeration:
1820-artificial ice was made in the laboratory for the first time.
1824- revealing the principle of absorption refrigeration
The production of artificial ice began.
1855- manufacturing absorption refrigeration device.
1890- small pieces of artificial ice enter the market-mechanical ice making industry begins.
19 10- Home mechanical refrigerator appears.
1913-the first manual household refrigerator was manufactured.