Refrigeration is a action in which assignment is done to move calefaction from one area to another. This assignment is commonly done by automated work, but can additionally be done by magnetism, laser or added means. Refrigeration has abounding applications, including, but not bound to: domiciliary refrigerators, automated freezers, cryogenics, air conditioning, and calefaction pumps.
Saturday, 10 March 2012
Historical applications
ce harvesting
The use of ice to air-condition and appropriately bottle aliment goes aback to aged times.12 Through the ages, the melancholia agriculture of snow and ice was a approved convenance of best of the age-old cultures: Chinese, Greeks, Romans, Persians. Ice and snow were stored in caves or dugouts lined with harbinger or added careful materials. The Persians stored ice in a pit alleged a yakhchal. Rationing of the ice accustomed the canning of foods over the balmy periods. This convenance formed able-bodied through the centuries, with icehouses actual in use into the 20th century.
In the 16th century, the analysis of actinic algidity was one of the aboriginal accomplish against bogus agency of refrigeration. Sodium nitrate or potassium nitrate, back added to water, bargain the baptize temperature and created a array of algidity ablution for cooling substances. In Italy, such a band-aid was acclimated to arctic wine and cakes.3
During the aboriginal bisected of the 19th century, ice agriculture became big business in America. New Englander Frederic Tudor, who became accepted as the "Ice King", formed on developing more good insulation articles to address ice continued distances, abnormally to the tropics.
The use of ice to air-condition and appropriately bottle aliment goes aback to aged times.12 Through the ages, the melancholia agriculture of snow and ice was a approved convenance of best of the age-old cultures: Chinese, Greeks, Romans, Persians. Ice and snow were stored in caves or dugouts lined with harbinger or added careful materials. The Persians stored ice in a pit alleged a yakhchal. Rationing of the ice accustomed the canning of foods over the balmy periods. This convenance formed able-bodied through the centuries, with icehouses actual in use into the 20th century.
In the 16th century, the analysis of actinic algidity was one of the aboriginal accomplish against bogus agency of refrigeration. Sodium nitrate or potassium nitrate, back added to water, bargain the baptize temperature and created a array of algidity ablution for cooling substances. In Italy, such a band-aid was acclimated to arctic wine and cakes.3
During the aboriginal bisected of the 19th century, ice agriculture became big business in America. New Englander Frederic Tudor, who became accepted as the "Ice King", formed on developing more good insulation articles to address ice continued distances, abnormally to the tropics.
First refrigeration systems
The aboriginal accepted adjustment of bogus algidity was approved by William Cullen at the University of Glasgow in Scotland in 1756. Cullen acclimated a pump to actualize a fractional exhaustion over a alembic of diethyl ether, which again boiled, arresting calefaction from the surrounding air.4 The agreement alike created a baby bulk of ice, but had no applied appliance at that time.
In 1758, Benjamin Franklin and John Hadley, assistant of allure at Cambridge University, conducted an agreement to analyze the assumption of dehydration as a agency to rapidly air-conditioned an object. Franklin and Hadley accepted dehydration of awful airy liquids, such as booze and ether, could be acclimated to drive bottomward the temperature of an article accomplished the freezing point of water. They conducted their agreement with the ball of a mercury thermometer as their article and with a bellows acclimated to "quicken" the evaporation; they bargain the temperature of the thermometer ball bottomward to 7 °F (−14 °C), while the ambient temperature was 65 °F (18 °C). Franklin acclaimed that anon afterwards they anesthetized the freezing point of baptize (32 °F), a attenuate blur of ice formed on the apparent of the thermometer's ball and that the ice accumulation was about a division inch blubbery back they chock-full the agreement aloft extensive 7 °F (−14 °C). Franklin concluded, "From this experiment, one may see the achievability of freezing a man to afterlife on a balmy summer's day".5
In 1805, American artist Oliver Evans designed, but never built, a algidity arrangement based on the vapor-compression algidity aeon rather than actinic solutions or airy liquids such as ethyl ether.
In 1820, the British scientist Michael Faraday abounding ammonia and added gases by application aerial pressures and low temperatures.
An American active in Great Britain, Jacob Perkins, acquired the aboriginal apparent for a vapor-compression algidity arrangement in 1834. Perkins congenital a ancestor arrangement and it absolutely worked, although it did not accomplish commercially.6
In 1842, an American physician, John Gorrie, advised the aboriginal arrangement to air-condition baptize to aftermath ice. He additionally conceived the abstraction of application his algidity arrangement to air-conditioned the air for abundance in homes and hospitals (i.e., air conditioning). His arrangement aeroembolism air, again partly cooled the hot aeroembolism air with baptize afore acceptance it to aggrandize while accomplishing allotment of the assignment bare to drive the air compressor. That isentropic amplification cooled the air to a temperature low abundant to benumb baptize and aftermath ice, or to breeze "through a aqueduct for ability algidity otherwise" as declared in his apparent accepted by the U.S. Apparent Office in 1851.7 Gorrie congenital a alive prototype, but his arrangement was a bartering failure.
In 1758, Benjamin Franklin and John Hadley, assistant of allure at Cambridge University, conducted an agreement to analyze the assumption of dehydration as a agency to rapidly air-conditioned an object. Franklin and Hadley accepted dehydration of awful airy liquids, such as booze and ether, could be acclimated to drive bottomward the temperature of an article accomplished the freezing point of water. They conducted their agreement with the ball of a mercury thermometer as their article and with a bellows acclimated to "quicken" the evaporation; they bargain the temperature of the thermometer ball bottomward to 7 °F (−14 °C), while the ambient temperature was 65 °F (18 °C). Franklin acclaimed that anon afterwards they anesthetized the freezing point of baptize (32 °F), a attenuate blur of ice formed on the apparent of the thermometer's ball and that the ice accumulation was about a division inch blubbery back they chock-full the agreement aloft extensive 7 °F (−14 °C). Franklin concluded, "From this experiment, one may see the achievability of freezing a man to afterlife on a balmy summer's day".5
In 1805, American artist Oliver Evans designed, but never built, a algidity arrangement based on the vapor-compression algidity aeon rather than actinic solutions or airy liquids such as ethyl ether.
In 1820, the British scientist Michael Faraday abounding ammonia and added gases by application aerial pressures and low temperatures.
An American active in Great Britain, Jacob Perkins, acquired the aboriginal apparent for a vapor-compression algidity arrangement in 1834. Perkins congenital a ancestor arrangement and it absolutely worked, although it did not accomplish commercially.6
In 1842, an American physician, John Gorrie, advised the aboriginal arrangement to air-condition baptize to aftermath ice. He additionally conceived the abstraction of application his algidity arrangement to air-conditioned the air for abundance in homes and hospitals (i.e., air conditioning). His arrangement aeroembolism air, again partly cooled the hot aeroembolism air with baptize afore acceptance it to aggrandize while accomplishing allotment of the assignment bare to drive the air compressor. That isentropic amplification cooled the air to a temperature low abundant to benumb baptize and aftermath ice, or to breeze "through a aqueduct for ability algidity otherwise" as declared in his apparent accepted by the U.S. Apparent Office in 1851.7 Gorrie congenital a alive prototype, but his arrangement was a bartering failure.
Widespread commercial use
By the 1870s, breweries had become the better users of bartering algidity units, admitting some still relied on harvested ice. Admitting the ice-harvesting industry had developed badly by the about-face of the 20th century, abuse and carrion had amorphous to edge into accustomed ice, authoritative it a botheration in the city suburbs. Eventually, breweries began to accuse of attenuated ice. This aloft the appeal for added avant-garde and consumer-ready algidity and ice-making machines.
Carl von Linde, an engineering assistant at the Technological University Munich in Germany, patented an bigger adjustment of liquefying gases in 1876. His fresh action fabricated accessible application gases such as ammonia, sulfur dioxide (SO2) and methyl chloride (CH3Cl) as refrigerants and they were broadly acclimated for that purpose until the backward 1920’s.
Refrigerated railroad cars were alien in the US in the 1840s for brief carriage of dairy products. In 1867, J.B. Sutherland of Detroit, Michigan patented the refrigerator car advised with ice tanks at either end of the car and chase flaps abreast the attic which would actualize a force abstract of algid air through the car.
By 1900, the meat packing houses of Chicago had adopted ammonia-cycle bartering refrigeration. By 1914, about every area acclimated bogus refrigeration. The big meat packers, Armour, Swift, and Wilson, had purchased the best big-ticket units which they installed on alternation cars and in annex houses and accumulator accessories in the added alien administration areas.
It was not until the average of the 20th aeon that algidity units were advised for accession on trucks or lorries. Refrigerated cartage are acclimated to carriage decaying goods, such as arctic foods, bake-apple and vegetables, and temperature-sensitive chemicals. Best avant-garde refrigerators accumulate the temperature amid -40 and 20 °C, and accept a best burden of about 24,000 kg gross weight (in Europe).
Home and customer use
With the apparatus of constructed refrigerants based mostly on a chlorofluorocarbon (CFC) chemical, safer refrigerators were accessible for home and customer use. Freon is a brand of the Dupont Corporation and refers to these CFCs, and after hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC), refrigerants developed in the backward 1920s. These refrigerants were advised at the time to be beneath adverse than the commonly-used refrigerants of the time, including methyl formate, ammonia, methyl chloride, and sulfur dioxide. The absorbed was to accommodate algidity accessories for home use after danger: these CFC refrigerants answered that need. In the 1970s, though, the compounds were begin to be reacting with atmospheric ozone, an important aegis adjoin solar ultraviolet radiation, and their use as a refrigerant common was concise in the Montreal Protocol of 1987.
Carl von Linde, an engineering assistant at the Technological University Munich in Germany, patented an bigger adjustment of liquefying gases in 1876. His fresh action fabricated accessible application gases such as ammonia, sulfur dioxide (SO2) and methyl chloride (CH3Cl) as refrigerants and they were broadly acclimated for that purpose until the backward 1920’s.
Refrigerated railroad cars were alien in the US in the 1840s for brief carriage of dairy products. In 1867, J.B. Sutherland of Detroit, Michigan patented the refrigerator car advised with ice tanks at either end of the car and chase flaps abreast the attic which would actualize a force abstract of algid air through the car.
By 1900, the meat packing houses of Chicago had adopted ammonia-cycle bartering refrigeration. By 1914, about every area acclimated bogus refrigeration. The big meat packers, Armour, Swift, and Wilson, had purchased the best big-ticket units which they installed on alternation cars and in annex houses and accumulator accessories in the added alien administration areas.
It was not until the average of the 20th aeon that algidity units were advised for accession on trucks or lorries. Refrigerated cartage are acclimated to carriage decaying goods, such as arctic foods, bake-apple and vegetables, and temperature-sensitive chemicals. Best avant-garde refrigerators accumulate the temperature amid -40 and 20 °C, and accept a best burden of about 24,000 kg gross weight (in Europe).
Home and customer use
With the apparatus of constructed refrigerants based mostly on a chlorofluorocarbon (CFC) chemical, safer refrigerators were accessible for home and customer use. Freon is a brand of the Dupont Corporation and refers to these CFCs, and after hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC), refrigerants developed in the backward 1920s. These refrigerants were advised at the time to be beneath adverse than the commonly-used refrigerants of the time, including methyl formate, ammonia, methyl chloride, and sulfur dioxide. The absorbed was to accommodate algidity accessories for home use after danger: these CFC refrigerants answered that need. In the 1970s, though, the compounds were begin to be reacting with atmospheric ozone, an important aegis adjoin solar ultraviolet radiation, and their use as a refrigerant common was concise in the Montreal Protocol of 1987.
Current applications of refrigeration
Probably the best broadly acclimated accepted applications of algidity are for air conditioning clandestine homes and attainable buildings, and refrigerating food in homes, restaurants and ample accumulator warehouses. The use of refrigerators in kitchens for autumn fruits and vegetables has accustomed abacus beginning salads to the avant-garde diet year round, and autumn angle and meats cautiously for continued periods.
In business and manufacturing, there are abounding uses for refrigeration. Algidity is acclimated to liquify gases - oxygen, nitrogen, propane and methane, for example. In aeroembolism air purification, it is acclimated to abbreviate baptize breath from aeroembolism air to abate its damp content. In oil refineries, actinic plants, and petrochemical plants, algidity is acclimated to advance assertive processes at their bare low temperatures (for example, in alkylation of butenes and butane to aftermath a aerial octane gasoline component). Metal workers use algidity to atmosphere animate and cutlery. In alteration temperature-sensitive food and added abstracts by trucks, trains, airplanes and sea-going vessels, algidity is a necessity.
Dairy articles are consistently in charge of refrigeration, and it was alone apparent in the accomplished few decades that eggs bare to be air-conditioned during addition rather than cat-and-mouse to be air-conditioned afterwards accession at the grocery store. Meats, banty and angle all charge be kept in climate-controlled environments afore actuality sold. Algidity additionally helps accumulate fruits and vegetables comestible longer.
One of the best affecting uses of algidity was in the development of the sushi/sashimi industry in Japan. Afore the analysis of refrigeration, abounding sushi connoisseurs were at accident of application diseases. The dangers of unrefrigerated sashimi were not brought to ablaze for decades due to the abridgement of analysis and healthcare administration beyond rural Japan. Around mid-century, the Zojirushi corporation, based in Kyoto, fabricated breakthroughs in refrigerator designs, authoritative refrigerators cheaper and added attainable for restaurant proprietors and the accepted public.
In business and manufacturing, there are abounding uses for refrigeration. Algidity is acclimated to liquify gases - oxygen, nitrogen, propane and methane, for example. In aeroembolism air purification, it is acclimated to abbreviate baptize breath from aeroembolism air to abate its damp content. In oil refineries, actinic plants, and petrochemical plants, algidity is acclimated to advance assertive processes at their bare low temperatures (for example, in alkylation of butenes and butane to aftermath a aerial octane gasoline component). Metal workers use algidity to atmosphere animate and cutlery. In alteration temperature-sensitive food and added abstracts by trucks, trains, airplanes and sea-going vessels, algidity is a necessity.
Dairy articles are consistently in charge of refrigeration, and it was alone apparent in the accomplished few decades that eggs bare to be air-conditioned during addition rather than cat-and-mouse to be air-conditioned afterwards accession at the grocery store. Meats, banty and angle all charge be kept in climate-controlled environments afore actuality sold. Algidity additionally helps accumulate fruits and vegetables comestible longer.
One of the best affecting uses of algidity was in the development of the sushi/sashimi industry in Japan. Afore the analysis of refrigeration, abounding sushi connoisseurs were at accident of application diseases. The dangers of unrefrigerated sashimi were not brought to ablaze for decades due to the abridgement of analysis and healthcare administration beyond rural Japan. Around mid-century, the Zojirushi corporation, based in Kyoto, fabricated breakthroughs in refrigerator designs, authoritative refrigerators cheaper and added attainable for restaurant proprietors and the accepted public.
Cyclic refrigeration
This consists of a algidity cycle, area calefaction is removed from a low-temperature amplitude or antecedent and alone to a high-temperature bore with the advice of alien work, and its inverse, the thermodynamic ability cycle. In the ability cycle, calefaction is supplied from a high-temperature antecedent to the engine, allotment of the calefaction actuality acclimated to aftermath assignment and the blow actuality alone to a low-temperature sink. This satisfies the additional law of thermodynamics.
A algidity aeon describes the changes that booty abode in the refrigerant as it alternately absorbs and rejects calefaction as it circulates through a refrigerator. It is additionally activated to HVACR work, back anecdotic the "process" of refrigerant breeze through an HVACR unit, whether it is a packaged or breach system.
Heat artlessly flows from hot to cold. Assignment is activated to air-conditioned a active amplitude or accumulator aggregate by pumping calefaction from a lower temperature calefaction antecedent into a college temperature calefaction sink. Insulation is acclimated to abate the assignment and activity bare to accomplish and advance a lower temperature in the cooled space. The operating assumption of the algidity aeon was declared mathematically by Sadi Carnot in 1824 as a calefaction engine.
The best accepted types of algidity systems use the reverse-Rankine vapor-compression algidity cycle, although assimilation calefaction pumps are acclimated in a boyhood of applications.
Cyclic algidity can be classified as:
Vapor cycle, and
Gas cycle
Vapor aeon algidity can added be classified as:
Vapor-compression refrigeration
Vapor-absorption refrigeration
A algidity aeon describes the changes that booty abode in the refrigerant as it alternately absorbs and rejects calefaction as it circulates through a refrigerator. It is additionally activated to HVACR work, back anecdotic the "process" of refrigerant breeze through an HVACR unit, whether it is a packaged or breach system.
Heat artlessly flows from hot to cold. Assignment is activated to air-conditioned a active amplitude or accumulator aggregate by pumping calefaction from a lower temperature calefaction antecedent into a college temperature calefaction sink. Insulation is acclimated to abate the assignment and activity bare to accomplish and advance a lower temperature in the cooled space. The operating assumption of the algidity aeon was declared mathematically by Sadi Carnot in 1824 as a calefaction engine.
The best accepted types of algidity systems use the reverse-Rankine vapor-compression algidity cycle, although assimilation calefaction pumps are acclimated in a boyhood of applications.
Cyclic algidity can be classified as:
Vapor cycle, and
Gas cycle
Vapor aeon algidity can added be classified as:
Vapor-compression refrigeration
Vapor-absorption refrigeration
Vapor-compression cycle
The vapor-compression aeon is acclimated in best domiciliary refrigerators as able-bodied as in abounding ample bartering and automated algidity systems. Figure 1 provides a schematic diagram of the apparatus of a archetypal vapor-compression algidity system
.
The thermodynamics of the aeon can be analyzed on a diagram1011 as apparent in Figure 2. In this cycle, a circulating refrigerant such as Freon enters the compressor as a vapor. From point 1 to point 2, the breath is aeroembolism at connected anarchy and exits the compressor as a breath at a college temperature, but still beneath the breath burden at that temperature. From point 2 to point 3 and on to point 4, the breath campaign through the condenser which cools the breath until it starts condensing, and again condenses the breath into a aqueous by removing added calefaction at connected burden and temperature. Between credibility 4 and 5, the aqueous refrigerant goes through the amplification valve (also alleged a burke valve) area its burden abruptly decreases, causing beam dehydration and auto-refrigeration of, typically, beneath than bisected of the liquid.
That after-effects in a admixture of aqueous and breath at a lower temperature and burden as apparent at point 5. The algid liquid-vapor admixture again campaign through the evaporator braid or tubes and is absolutely vaporized by cooling the balmy air (from the amplitude actuality refrigerated) actuality absolute by a fan beyond the evaporator braid or tubes. The consistent refrigerant breath allotment to the compressor basin at point 1 to complete the thermodynamic cycle.
The aloft altercation is based on the ideal vapor-compression algidity cycle, and does not booty into annual real-world furnishings like frictional burden bead in the system, slight thermodynamic irreversibility during the compression of the refrigerant vapor, or non-ideal gas behavior (if any).
e advice about the architecture and achievement of vapor-compression algidity systems is accessible in the archetypal Perry's Chemical Engineers' Handbook.12
.
The thermodynamics of the aeon can be analyzed on a diagram1011 as apparent in Figure 2. In this cycle, a circulating refrigerant such as Freon enters the compressor as a vapor. From point 1 to point 2, the breath is aeroembolism at connected anarchy and exits the compressor as a breath at a college temperature, but still beneath the breath burden at that temperature. From point 2 to point 3 and on to point 4, the breath campaign through the condenser which cools the breath until it starts condensing, and again condenses the breath into a aqueous by removing added calefaction at connected burden and temperature. Between credibility 4 and 5, the aqueous refrigerant goes through the amplification valve (also alleged a burke valve) area its burden abruptly decreases, causing beam dehydration and auto-refrigeration of, typically, beneath than bisected of the liquid.
That after-effects in a admixture of aqueous and breath at a lower temperature and burden as apparent at point 5. The algid liquid-vapor admixture again campaign through the evaporator braid or tubes and is absolutely vaporized by cooling the balmy air (from the amplitude actuality refrigerated) actuality absolute by a fan beyond the evaporator braid or tubes. The consistent refrigerant breath allotment to the compressor basin at point 1 to complete the thermodynamic cycle.
The aloft altercation is based on the ideal vapor-compression algidity cycle, and does not booty into annual real-world furnishings like frictional burden bead in the system, slight thermodynamic irreversibility during the compression of the refrigerant vapor, or non-ideal gas behavior (if any).
e advice about the architecture and achievement of vapor-compression algidity systems is accessible in the archetypal Perry's Chemical Engineers' Handbook.12
Vapor absorption cycle
In the aboriginal years of the twentieth century, the breath assimilation aeon application water-ammonia systems was accepted and broadly used. After the development of the breath compression cycle, the breath assimilation aeon absent abundant of its accent because of its low accessory of achievement (about one fifth of that of the breath compression cycle). Today, the breath assimilation aeon is acclimated mainly area ammunition for heating is accessible but electricity is not, such as in recreational cartage that backpack LP gas. It is additionally acclimated in automated environments area abounding decay calefaction overcomes its inefficiency.
The assimilation aeon is agnate to the compression cycle, except for the adjustment of adopting the burden of the refrigerant vapor. In the assimilation system, the compressor is replaced by an cushion which dissolves the refrigerant in a acceptable liquid, a aqueous pump which raises the burden and a architect which, on calefaction addition, drives off the refrigerant breath from the high-pressure liquid. Some assignment is bare by the aqueous pump but, for a accustomed abundance of refrigerant, it is abundant abate than bare by the compressor in the breath compression cycle. In an assimilation refrigerator, a acceptable aggregate of refrigerant and absorptive is used. The best accepted combinations are ammonia (refrigerant) and baptize (absorbent), and baptize (refrigerant) and lithium bromideabsorbent.
The assimilation aeon is agnate to the compression cycle, except for the adjustment of adopting the burden of the refrigerant vapor. In the assimilation system, the compressor is replaced by an cushion which dissolves the refrigerant in a acceptable liquid, a aqueous pump which raises the burden and a architect which, on calefaction addition, drives off the refrigerant breath from the high-pressure liquid. Some assignment is bare by the aqueous pump but, for a accustomed abundance of refrigerant, it is abundant abate than bare by the compressor in the breath compression cycle. In an assimilation refrigerator, a acceptable aggregate of refrigerant and absorptive is used. The best accepted combinations are ammonia (refrigerant) and baptize (absorbent), and baptize (refrigerant) and lithium bromideabsorbent.
Gas cycle
When the alive aqueous is a gas that is aeroembolism and broadcast but doesn't change phase, the algidity aeon is alleged a gas cycle. Air is best generally this alive fluid. As there is no abstract and dehydration advised in a gas cycle, apparatus agnate to the condenser and evaporator in a breath compression aeon are the hot and algid gas-to-gas calefaction exchangers in gas cycles.
The gas aeon is beneath able than the breath compression aeon because the gas aeon works on the about-face Brayton aeon instead of the about-face Rankine cycle. As such the alive aqueous does not accept and adios calefaction at connected temperature. In the gas cycle, the algidity aftereffect is according to the artefact of the specific calefaction of the gas and the acceleration in temperature of the gas in the low temperature side. Therefore, for the aforementioned cooling load, a gas algidity aeon needs a ample accumulation breeze amount and is bulky.
Because of their lower ability and beyond bulk, air aeon coolers are not generally acclimated nowadays in earthbound cooling devices. However, the air aeon apparatus is actual accepted on gas turbine-powered jet aircraft as cooling and blast units, because aeroembolism air is readily accessible from the engines' compressor sections. Such units additionally serve the purpose of pressurizing the aircraft.
The gas aeon is beneath able than the breath compression aeon because the gas aeon works on the about-face Brayton aeon instead of the about-face Rankine cycle. As such the alive aqueous does not accept and adios calefaction at connected temperature. In the gas cycle, the algidity aftereffect is according to the artefact of the specific calefaction of the gas and the acceleration in temperature of the gas in the low temperature side. Therefore, for the aforementioned cooling load, a gas algidity aeon needs a ample accumulation breeze amount and is bulky.
Because of their lower ability and beyond bulk, air aeon coolers are not generally acclimated nowadays in earthbound cooling devices. However, the air aeon apparatus is actual accepted on gas turbine-powered jet aircraft as cooling and blast units, because aeroembolism air is readily accessible from the engines' compressor sections. Such units additionally serve the purpose of pressurizing the aircraft.
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