Refrigeration

Refrigeration

Overview
Refrigeration is a process in which work is done to move heat from one location to another. This work is traditionally done by mechanical work
Mechanical work
In physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...

, but can also be done by magnetism
Magnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...

, laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

 or other means. Refrigeration has many applications, including, but not limited to: household refrigerators, industrial freezers, cryogenics, air conditioning, and heat pumps.

The use of ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 to refrigerate and thus preserve food goes back to prehistoric times.
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Encyclopedia
Refrigeration is a process in which work is done to move heat from one location to another. This work is traditionally done by mechanical work
Mechanical work
In physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...

, but can also be done by magnetism
Magnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...

, laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...

 or other means. Refrigeration has many applications, including, but not limited to: household refrigerators, industrial freezers, cryogenics, air conditioning, and heat pumps.

Ice harvesting


The use of ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 to refrigerate and thus preserve food goes back to prehistoric times. Through the ages, the seasonal harvesting of snow and ice was a regular practice of most of the ancient cultures: Chinese, Greeks, Romans, Persians. Ice and snow were stored in caves or dugouts
Dugout (shelter)
A dugout or dug-out, also known as a pithouse, pit-house, earth lodge, mud hut, is a shelter for humans or domesticated animals and livestock based on a hole or depression dug into the ground. These structures are one of the most ancient types of human housing known to archeologists...

 lined with straw
Straw
Straw is an agricultural by-product, the dry stalks of cereal plants, after the grain and chaff have been removed. Straw makes up about half of the yield of cereal crops such as barley, oats, rice, rye and wheat. It has many uses, including fuel, livestock bedding and fodder, thatching and...

 or other insulating materials. The Persians stored ice in a pit called a yakhchal
Yakhchal
Yakhchāl is an ancient type of refrigerator. The word also means "glacier" in Persian.In 400 BC Persian engineers had already mastered the technique of storing ice in the middle of summer in the desert....

. Rationing of the ice allowed the preservation of foods over the warm periods. This practice worked well through the centuries, with icehouse
Icehouse (building)
Ice houses were buildings used to store ice throughout the year, prior to the invention of the refrigerator. Some were underground chambers, usually man-made, close to natural sources of winter ice such as freshwater lakes, but many were buildings with various types of insulation.During the...

s remaining in use into the 20th century.

In the 16th century, the discovery of chemical refrigeration was one of the first steps toward artificial means of refrigeration. Sodium nitrate
Sodium nitrate
Sodium nitrate is the chemical compound with the formula NaNO3. This salt, also known as Chile saltpeter or Peru saltpeter to distinguish it from ordinary saltpeter, potassium nitrate, is a white solid which is very soluble in water...

 or potassium nitrate
Potassium nitrate
Potassium nitrate is a chemical compound with the formula KNO3. It is an ionic salt of potassium ions K+ and nitrate ions NO3−.It occurs as a mineral niter and is a natural solid source of nitrogen. Its common names include saltpetre , from medieval Latin sal petræ: "stone salt" or possibly "Salt...

, when added to water, lowered the water temperature and created a sort of refrigeration bath for cooling substances. In Italy, such a solution was used to chill wine and cakes.

During the first half of the 19th century, ice harvesting became big business in America. New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...

er Frederic Tudor
Frederic Tudor
Frederic Tudor was known as Boston's "Ice King", and was the founder of the Tudor Ice Company. During the early 19th Century, he made a fortune shipping ice to the Caribbean, Europe, and even as far away as India from sources of fresh water ice in New England.The Tudor Ice Company harvested ice in...

, who became known as the "Ice King", worked on developing better insulation
Thermal insulation
Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...

 products to ship ice long distances, especially to the tropics.

First refrigeration systems


The first known method of artificial refrigeration was demonstrated by William Cullen
William Cullen
William Cullen FRS FRSE FRCPE FPSG was a Scottish physician, chemist and agriculturalist, and one of the most important professors at the Edinburgh Medical School, during its heyday as the leading center of medical education in the English-speaking world.Cullen was also a central figure in the...

 at the University of Glasgow
University of Glasgow
The University of Glasgow is the fourth-oldest university in the English-speaking world and one of Scotland's four ancient universities. Located in Glasgow, the university was founded in 1451 and is presently one of seventeen British higher education institutions ranked amongst the top 100 of the...

 in Scotland
Scotland
Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 in 1756. Cullen used a pump to create a partial vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...

 over a container of diethyl ether
Diethyl ether
Diethyl ether, also known as ethyl ether, simply ether, or ethoxyethane, is an organic compound in the ether class with the formula . It is a colorless, highly volatile flammable liquid with a characteristic odor...

, which then boiled
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....

, absorbing heat from the surrounding air. The experiment even created a small amount of ice, but had no practical application at that time.

In 1758, Benjamin Franklin
Benjamin Franklin
Dr. Benjamin Franklin was one of the Founding Fathers of the United States. A noted polymath, Franklin was a leading author, printer, political theorist, politician, postmaster, scientist, musician, inventor, satirist, civic activist, statesman, and diplomat...

 and John Hadley, professor of chemistry at Cambridge University, conducted an experiment to explore the principle of evaporation as a means to rapidly cool an object. Franklin and Hadley confirmed evaporation of highly volatile liquids, such as alcohol and ether, could be used to drive down the temperature of an object past the freezing point of water. They conducted their experiment with the bulb of a mercury thermometer as their object and with a bellows used to "quicken" the evaporation; they lowered the temperature of the thermometer bulb down to 7 °F (-13.9 °C), while the ambient temperature was 65 °F (18.3 °C). Franklin noted that soon after they passed the freezing point of water (32 °F), a thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about a quarter inch thick when they stopped the experiment upon reaching 7 °F (-13.9 °C). Franklin concluded, "From this experiment, one may see the possibility of freezing a man to death on a warm summer's day".

In 1805, American inventor Oliver Evans
Oliver Evans
Oliver Evans was an American inventor. Evans was born in Newport, Delaware to a family of Welsh settlers. At the age of 14 he was apprenticed to a wheelwright....

 designed, but never built, a refrigeration system based on the vapor-compression refrigeration
Vapor-compression refrigeration
Vapor-compression refrigeration is one of the many refrigeration cycles available for use. It has been and is the most widely used method for air-conditioning of large public buildings, offices, private residences, hotels, hospitals, theaters, restaurants and automobiles...

 cycle rather than chemical solutions or volatile liquids such as ethyl ether.

In 1820, the British scientist Michael Faraday
Michael Faraday
Michael Faraday, FRS was an English chemist and physicist who contributed to the fields of electromagnetism and electrochemistry....

 liquefied ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

 and other gases by using high pressures and low temperatures.

An American living in Great Britain, Jacob Perkins
Jacob Perkins
Jacob Perkins was an Anglo-American inventor, mechanical engineer and physicist. Born in Newburyport, Massachusetts, Perkins was apprenticed to a goldsmith...

, obtained the first patent for a vapor-compression refrigeration system in 1834. Perkins built a prototype system and it actually worked, although it did not succeed commercially.

In 1842, an American physician, John Gorrie
John Gorrie
John Gorrie , physician, scientist, inventor, and humanitarian, is considered the father of refrigeration and air conditioning. He was born on the Island of Nevis to Scottish parents on October 3, 1802, and spent his childhood in South Carolina...

, designed the first system to refrigerate water to produce ice. He also conceived the idea of using his refrigeration system to cool the air for comfort in homes and hospitals (i.e., air conditioning). His system compressed air, then partly cooled the hot compressed air with water before allowing it to expand while doing part of the work needed to drive the air compressor
Gas compressor
A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...

. That isentropic expansion cooled the air to a temperature low enough to freeze water and produce ice, or to flow "through a pipe for effecting refrigeration otherwise" as stated in his patent granted by the U.S. Patent Office in 1851. Gorrie built a working prototype, but his system was a commercial failure.

Alexander Twining began experimenting with vapor-compression refrigeration in 1848, and obtained patents in 1850 and 1853. He is credited with having initiated commercial refrigeration in the United States by 1856.

Meanwhile in Australia, James Harrison
James Harrison (engineer)
James Harrison was an Australian newspaper printer, journalist, politician, and pioneer in the field of mechanical refrigeration.-Early life:...

 began operation of a mechanical ice-making machine in 1851 on the banks of the Barwon River at Rocky Point in Geelong, Victoria. His first commercial ice-making machine followed in 1854, and his patent for an ether liquid-vapour compression refrigeration system was granted in 1855. Harrison introduced commercial vapour-compression refrigeration to breweries and meat packing houses, and by 1861, a dozen of his systems were in operation.

Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

n, Argentine
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

, and American
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

 concerns experimented with refrigerated shipping in the mid 1870s; the first commercial success came when William Soltau Davidson
William Soltau Davidson
William Soltau Davidson was the New Zealand pioneer of refrigerated shipping.-Early life:Son of Frances Pillans and bank manager David Davidson, William Davidson was born in Montreal, Canada. He attended the Edinburgh Academy, , before taking a position book keeping in Glasgow...

 fitted a compression refrigeration unit to the New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...

 vessel Dunedin
Dunedin (ship)
The Dunedin was the first ship to complete a truly successful transport of refrigerated meat. In its capacity, it helped set the stage for New Zealand's success as a major provider of agricultural exports, notwithstanding its extreme remoteness from most markets.-Ship origins:The 1,320-ton, ...

 in 1882, leading to a meat and dairy boom in Australasia
Australasia
Australasia is a region of Oceania comprising Australia, New Zealand, the island of New Guinea, and neighbouring islands in the Pacific Ocean. The term was coined by Charles de Brosses in Histoire des navigations aux terres australes...

 and South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

. J & E Hall of Dartford
Dartford
Dartford is the principal town in the borough of Dartford. It is situated in the northwest corner of Kent, England, east south-east of central London....

, England outfitted the 'SS Selembria' with a vapor compression system to bring 30,000 carcasses of mutton from the Falkland Islands
Falkland Islands
The Falkland Islands are an archipelago in the South Atlantic Ocean, located about from the coast of mainland South America. The archipelago consists of East Falkland, West Falkland and 776 lesser islands. The capital, Stanley, is on East Falkland...

 in 1886.

The first gas absorption refrigeration system using gaseous ammonia dissolved in water (referred to as "aqua ammonia") was developed by Ferdinand Carré
Ferdinand Carré
Ferdinand Philippe Edouard Carré was a French engineer, born at Moislains on 11 March 1824. Carré is best known as the inventor of refrigeration equipment used to produce ice...

 of France in 1859 and patented in 1860. Due to the toxicity of ammonia, such systems were not developed for use in homes, but were used to manufacture ice for sale. In the United States, the consumer public at that time still used the ice box
Ice Box
The Ice Box is a 5,010-seat multi-purpose arena in Lincoln, Nebraska. It was adapted for hockey upon the Lincoln Stars' arrival in 1997. The Ice Box is located at 1800 State Fair Park Drive, on the Nebraska State Fair grounds....

 with ice brought in from commercial suppliers, many of whom were still harvesting ice and storing it in an icehouse
Icehouse (building)
Ice houses were buildings used to store ice throughout the year, prior to the invention of the refrigerator. Some were underground chambers, usually man-made, close to natural sources of winter ice such as freshwater lakes, but many were buildings with various types of insulation.During the...

.

Thaddeus Lowe, an American balloonist from the Civil War, had experimented over the years with the properties of gases. One of his mainstay enterprises was the high-volume production of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 gas. He also held several patents on ice-making machines. His "Compression Ice Machine" would revolutionize the cold storage industry. In 1869, other investors and he purchased an old steamship onto which they loaded one of Lowe’s refrigeration units, and began shipping fresh fruit from New York to the Gulf Coast area, and fresh meat from Galveston, Texas back to New York. Because of Lowe’s lack of knowledge about shipping, the business was a costly failure, and it was difficult for the public to get used to the idea of being able to consume meat that had been so long out of the packing house.

Domestic mechanical refrigerator
Refrigerator
A refrigerator is a common household appliance that consists of a thermally insulated compartment and a heat pump that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room...

s became available in the United States around 1911.

Widespread commercial use



By the 1870s, breweries had become the largest users of commercial refrigeration units, though some still relied on harvested ice. Though the ice-harvesting industry had grown immensely by the turn of the 20th century, pollution and sewage had begun to creep into natural ice, making it a problem in the metropolitan suburbs. Eventually, breweries began to complain of tainted ice. This raised demand for more modern and consumer-ready refrigeration and ice-making machines. In 1895, German engineer Carl von Linde
Carl von Linde
Professor Doctor Carl Paul Gottfried von Linde was a German engineer who developed refrigeration and gas separation technologies...

 set up a large-scale process for the production of liquid air, and eventually liquid oxygen, for use in safe household refrigerators.

Refrigerated railroad cars were introduced in the US in the 1840s for short-run transport of dairy products. In 1867, J.B. Sutherland of Detroit, Michigan patented the refrigerator car designed with ice tanks at either end of the car and ventilator flaps near the floor which would create a gravity draft of cold air through the car.

By 1900, the meat packing houses of Chicago had adopted ammonia-cycle commercial refrigeration. By 1914, almost every location used artificial refrigeration. The big meat packers, Armour
Armour and Company
Armour & Company was an American slaughterhouse and meatpacking company founded in Chicago, Illinois, in 1867 by the Armour brothers, led by Philip Danforth Armour. By 1880, the company was Chicago's most important business and helped make the city and its Union Stock Yards the center of the...

, Swift, and Wilson, had purchased the most expensive units which they installed on train cars and in branch houses and storage facilities in the more remote distribution areas.

It was not until the middle of the 20th century that refrigeration units were designed for installation on trucks or lorries. Refrigerated vehicles are used to transport perishable goods, such as frozen foods, fruit and vegetables, and temperature-sensitive chemicals. Most modern refrigerators keep the temperature between -40 and 20 °C, and have a maximum payload of around 24,000 kg gross weight (in Europe).

Home and consumer use


With the invention of synthetic refrigerants based mostly on a chlorofluorocarbon
Chlorofluorocarbon
A chlorofluorocarbon is an organic compound that contains carbon, chlorine, and fluorine, produced as a volatile derivative of methane and ethane. A common subclass are the hydrochlorofluorocarbons , which contain hydrogen, as well. They are also commonly known by the DuPont trade name Freon...

 (CFC) chemical, safer refrigerators were possible for home and consumer use. Freon is a trademark
Trademark
A trademark, trade mark, or trade-mark is a distinctive sign or indicator used by an individual, business organization, or other legal entity to identify that the products or services to consumers with which the trademark appears originate from a unique source, and to distinguish its products or...

 of the Dupont Corporation and refers to these CFCs, and later hydrochlorofluorocarbon (HCFC) and hydrofluorocarbon (HFC), refrigerants developed in the late 1920s. These refrigerants were considered at the time to be less harmful than the commonly-used refrigerants of the time, including methyl formate
Methyl formate
Methyl formate, also called methyl methanoate, is the methyl ester of formic acid. The simplest example of an ester, it is a clear liquid with an ethereal odor, high vapor pressure, and low surface tension.-Production:...

, ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...

, methyl chloride, and sulfur dioxide
Sulfur dioxide
Sulfur dioxide is the chemical compound with the formula . It is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel...

. The intent was to provide refrigeration equipment for home use without danger: these CFC refrigerants answered that need. In the 1970s, though, the compounds were found to be reacting with atmospheric ozone
Ozone layer
The ozone layer is a layer in Earth's atmosphere which contains relatively high concentrations of ozone . This layer absorbs 97–99% of the Sun's high frequency ultraviolet light, which is potentially damaging to the life forms on Earth...

, an important protection against solar ultraviolet radiation, and their use as a refrigerant worldwide was curtailed in the Montreal Protocol
Montreal Protocol
The Montreal Protocol on Substances That Deplete the Ozone Layer is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances believed to be responsible for ozone depletion...

 of 1987.

Current applications of refrigeration


Probably the most widely used current applications of refrigeration are for air conditioning private homes and public buildings, and refrigerating foodstuffs in homes, restaurants and large storage warehouses. The use of refrigerators in kitchens for storing fruits and vegetables has allowed adding fresh salads to the modern diet year round, and storing fish and meats safely for long periods.

In commerce and manufacturing, there are many uses for refrigeration. Refrigeration is used to liquify gases - oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

, nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...

, propane
Propane
Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central...

 and methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...

, for example. In compressed air purification, it is used to condense
Condensation
Condensation is the change of the physical state of matter from gaseous phase into liquid phase, and is the reverse of vaporization. When the transition happens from the gaseous phase into the solid phase directly, the change is called deposition....

 water vapor from compressed air to reduce its moisture content. In oil refineries
Oil refinery
An oil refinery or petroleum refinery is an industrial process plant where crude oil is processed and refined into more useful petroleum products, such as gasoline, diesel fuel, asphalt base, heating oil, kerosene, and liquefied petroleum gas...

, chemical plant
Chemical plant
A chemical plant is an industrial process plant that manufactures chemicals, usually on a large scale. The general objective of a chemical plant is to create new material wealth via the chemical or biological transformation and or separation of materials. Chemical plants use special equipment,...

s, and petrochemical
Petrochemical
Petrochemicals are chemical products derived from petroleum. Some chemical compounds made from petroleum are also obtained from other fossil fuels, such as coal or natural gas, or renewable sources such as corn or sugar cane....

 plants, refrigeration is used to maintain certain processes at their needed low temperatures (for example, in alkylation
Alkylation
Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion or a carbene . Alkylating agents are widely used in chemistry because the alkyl group is probably the most common group encountered in...

 of butenes and butane
Butane
Butane is a gas with the formula C4H10 that is an alkane with four carbon atoms. The term may refer to any of two structural isomers, or to a mixture of them: in the IUPAC nomenclature, however, butane refers only to the unbranched n-butane isomer; the other one being called "methylpropane" or...

 to produce a high octane
Octane rating
Octane rating or octane number is a standard measure of the anti-knock properties of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating...

 gasoline component). Metal workers use refrigeration to temper steel and cutlery. In transporting temperature-sensitive foodstuffs and other materials by trucks, trains, airplanes and sea-going vessels, refrigeration is a necessity.

Dairy products are constantly in need of refrigeration, and it was only discovered in the past few decades that eggs needed to be refrigerated during shipment rather than waiting to be refrigerated after arrival at the grocery store. Meats, poultry and fish all must be kept in climate-controlled environments before being sold. Refrigeration also helps keep fruits and vegetables edible longer.

One of the most influential uses of refrigeration was in the development of the sushi
Sushi
is a Japanese food consisting of cooked vinegared rice combined with other ingredients . Neta and forms of sushi presentation vary, but the ingredient which all sushi have in common is shari...

/sashimi
Sashimi
Sashimi is a Japanese delicacy. It consists of very fresh raw meat, most commonly fish, sliced into thin pieces.-Origin:The word sashimi means "pierced body", i.e...

 industry in Japan. Before the discovery of refrigeration, many sushi connoisseurs were at risk of contracting diseases. The dangers of unrefrigerated sashimi were not brought to light for decades due to the lack of research and healthcare distribution across rural Japan. Around mid-century, the Zojirushi corporation, based in Kyoto, made breakthroughs in refrigerator designs, making refrigerators cheaper and more accessible for restaurant proprietors and the general public.

Methods of refrigeration


Methods of refrigeration can be classified as non-cyclic, cyclic, thermoelectric and magnetic.

Non-cyclic refrigeration


In non-cyclic refrigeration, cooling is accomplished by melting ice
Ice
Ice is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...

 or by subliming
Sublimation (physics)
Sublimation is the process of transition of a substance from the solid phase to the gas phase without passing through an intermediate liquid phase...

 dry ice
Dry ice
Dry ice, sometimes referred to as "Cardice" or as "card ice" , is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue...

 (frozen carbon dioxide). These methods are used for small-scale refrigeration such as in laboratories and workshops, or in portable cooler
Cooler
A cooler, cool box, portable ice chest, chilly bin , or esky most commonly is an insulated box used to keep food or drink cool. Ice cubes are most commonly placed in it to help the things inside stay cool...

s.

Ice owes its effectiveness as a cooling agent to its melting point
Melting point
The melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...

 of 0 °C (32 °F) at sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...

. To melt, ice must absorb 333.55 kJ/kg (about 144 Btu/lb) of heat. Foodstuffs maintained near this temperature have an increased storage life.

Solid carbon dioxide has no liquid phase at normal atmospheric pressure, and sublimes directly from the solid to vapor phase at a temperature of -78.5 °C (-109.3 °F), and is effective for maintaining products at low temperatures during sublimation. Systems such as this where the refrigerant evaporates and is vented to the atmosphere are known as "total loss refrigeration".

Cyclic refrigeration



This consists of a refrigeration cycle, where heat is removed from a low-temperature space or source and rejected to a high-temperature sink with the help of external work, and its inverse, the thermodynamic power cycle. In the power cycle, heat is supplied from a high-temperature source to the engine, part of the heat being used to produce work and the rest being rejected to a low-temperature sink. This satisfies the second law of thermodynamics
Second law of thermodynamics
The second law of thermodynamics is an expression of the tendency that over time, differences in temperature, pressure, and chemical potential equilibrate in an isolated physical system. From the state of thermodynamic equilibrium, the law deduced the principle of the increase of entropy and...

.

A refrigeration cycle describes the changes that take place in the refrigerant as it alternately absorbs and rejects heat as it circulates through a refrigerator
Refrigerator
A refrigerator is a common household appliance that consists of a thermally insulated compartment and a heat pump that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room...

. It is also applied to HVACR work, when describing the "process" of refrigerant flow through an HVACR unit, whether it is a packaged or split system.

Heat naturally flows from hot to cold. Work
Mechanical work
In physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does work...

 is applied to cool a living space or storage volume by pumping heat from a lower temperature heat source into a higher temperature heat sink. Insulation
Thermal insulation
Thermal insulation is the reduction of the effects of the various processes of heat transfer between objects in thermal contact or in range of radiative influence. Heat transfer is the transfer of thermal energy between objects of differing temperature...

 is used to reduce the work and energy needed to achieve and maintain a lower temperature in the cooled space. The operating principle of the refrigeration cycle was described mathematically by Sadi Carnot
Nicolas Léonard Sadi Carnot
Nicolas Léonard Sadi Carnot was a French military engineer who, in his 1824 Reflections on the Motive Power of Fire, gave the first successful theoretical account of heat engines, now known as the Carnot cycle, thereby laying the foundations of the second law of thermodynamics...

 in 1824 as a heat engine
Carnot heat engine
A Carnot heat engine is a hypothetical engine that operates on the reversible Carnot cycle. The basic model for this engine was developed by Nicolas Léonard Sadi Carnot in 1824...

.

The most common types of refrigeration systems use the reverse-Rankine vapor-compression refrigeration
Vapor-compression refrigeration
Vapor-compression refrigeration is one of the many refrigeration cycles available for use. It has been and is the most widely used method for air-conditioning of large public buildings, offices, private residences, hotels, hospitals, theaters, restaurants and automobiles...

 cycle, although absorption heat pump
Absorption heat pump
Absorption heat pump is essentially an air-source heat pump driven not by electricity, but by a heat source such as solar-heated water, or geothermal-heated water...

s are used in a minority of applications.

Cyclic refrigeration can be classified as:
  1. Vapor cycle, and
  2. Gas cycle


Vapor cycle refrigeration can further be classified as:
  1. Vapor-compression refrigeration
    Vapor-compression refrigeration
    Vapor-compression refrigeration is one of the many refrigeration cycles available for use. It has been and is the most widely used method for air-conditioning of large public buildings, offices, private residences, hotels, hospitals, theaters, restaurants and automobiles...

  2. Vapor-absorption refrigeration
    Absorption refrigerator
    An absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling system...


Vapor-compression cycle

(See Heat pump and refrigeration cycle
Heat pump and refrigeration cycle
Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pumps and refrigerators. A heat pump is a machine or device that moves heat from one location at a lower temperature to another location at a higher temperature using mechanical work or a...

 and Vapor-compression refrigeration
Vapor-compression refrigeration
Vapor-compression refrigeration is one of the many refrigeration cycles available for use. It has been and is the most widely used method for air-conditioning of large public buildings, offices, private residences, hotels, hospitals, theaters, restaurants and automobiles...

 for more details)


The vapor-compression cycle is used in most household refrigerators as well as in many large commercial and industrial refrigeration systems. Figure 1 provides a schematic diagram of the components of a typical vapor-compression refrigeration system.
The thermodynamics
Thermodynamics
Thermodynamics is a physical science that studies the effects on material bodies, and on radiation in regions of space, of transfer of heat and of work done on or by the bodies or radiation...

 of the cycle can be analyzed on a diagram as shown in Figure 2. In this cycle, a circulating refrigerant such as Freon enters the compressor
Gas compressor
A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of a gas...

 as a vapor. From point 1 to point 2, the vapor is compressed at constant entropy
Entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...

 and exits the compressor as a vapor at a higher temperature, but still below the vapor pressure
Vapor pressure
Vapor pressure or equilibrium vapor pressure is the pressure of a vapor in thermodynamic equilibrium with its condensed phases in a closed system. All liquids have a tendency to evaporate, and some solids can sublimate into a gaseous form...

 at that temperature. From point 2 to point 3 and on to point 4, the vapor travels through the condenser
Condenser (heat transfer)
In systems involving heat transfer, a condenser is a device or unit used to condense a substance from its gaseous to its liquid state, typically by cooling it. In so doing, the latent heat is given up by the substance, and will transfer to the condenser coolant...

 which cools the vapor until it starts condensing, and then condenses the vapor into a liquid by removing additional heat at constant pressure and temperature. Between points 4 and 5, the liquid refrigerant goes through the expansion valve
Thermal expansion valve
A thermal expansion valve is a component in refrigeration and air conditioning systems that controls the amount of refrigerant flow into the evaporator thereby controlling the superheating at the outlet of the evaporator...

 (also called a throttle valve) where its pressure abruptly decreases, causing flash evaporation
Flash evaporation
Flash evaporation is the partial vapor that occurs when a saturated liquid stream undergoes a reduction in pressure by passing through a throttling valve or other throttling device. This process is one of the simplest unit operations...

 and auto-refrigeration of, typically, less than half of the liquid.
That results in a mixture of liquid and vapor at a lower temperature and pressure as shown at point 5. The cold liquid-vapor mixture then travels through the evaporator coil or tubes and is completely vaporized by cooling the warm air (from the space being refrigerated) being blown by a fan across the evaporator coil or tubes. The resulting refrigerant vapor returns to the compressor inlet at point 1 to complete the thermodynamic cycle.

The above discussion is based on the ideal vapor-compression refrigeration cycle, and does not take into account real-world effects like frictional pressure drop in the system, slight thermodynamic irreversibility during the compression of the refrigerant vapor, or non-ideal gas
Ideal gas
An ideal gas is a theoretical gas composed of a set of randomly-moving, non-interacting point particles. The ideal gas concept is useful because it obeys the ideal gas law, a simplified equation of state, and is amenable to analysis under statistical mechanics.At normal conditions such as...

 behavior (if any).

More information about the design and performance of vapor-compression refrigeration systems is available in the classic Perry's Chemical Engineers' Handbook
Perry's Chemical Engineers' Handbook
Perry's Chemical Engineers' Handbook was first published in 1934 and the most current eighth edition was published in October 2007...

.

Vapor absorption cycle



In the early years of the twentieth century, the vapor absorption cycle using water-ammonia systems was popular and widely used. After the development of the vapor compression cycle, the vapor absorption cycle lost much of its importance because of its low coefficient of performance (about one fifth of that of the vapor compression cycle). Today, the vapor absorption cycle is used mainly where fuel for heating is available but electricity is not, such as in recreational vehicles that carry LP gas. It is also used in industrial environments where plentiful waste heat overcomes its inefficiency.

The absorption cycle is similar to the compression cycle, except for the method of raising the pressure of the refrigerant vapor. In the absorption system, the compressor is replaced by an absorber which dissolves the refrigerant in a suitable liquid, a liquid pump which raises the pressure and a generator which, on heat addition, drives off the refrigerant vapor from the high-pressure liquid. Some work is needed by the liquid pump but, for a given quantity of refrigerant, it is much smaller than needed by the compressor in the vapor compression cycle. In an absorption refrigerator, a suitable combination of refrigerant and absorbent is used. The most common combinations are ammonia (refrigerant) and water (absorbent), and water (refrigerant) and lithium bromide[absorbent].

Gas cycle


When the working fluid is a gas that is compressed and expanded but doesn't change phase, the refrigeration cycle is called a gas cycle. Air is most often this working fluid. As there is no condensation and evaporation intended in a gas cycle, components corresponding to the condenser and evaporator in a vapor compression cycle are the hot and cold gas-to-gas heat exchangers in gas cycles.

The gas cycle is less efficient than the vapor compression cycle because the gas cycle works on the reverse Brayton cycle
Brayton cycle
The Brayton cycle is a thermodynamic cycle that describes the workings of the gas turbine engine, basis of the airbreathing jet engine and others. It is named after George Brayton , the American engineer who developed it, although it was originally proposed and patented by Englishman John Barber...

 instead of the reverse Rankine cycle
Rankine cycle
The Rankine cycle is a cycle that converts heat into work. The heat is supplied externally to a closed loop, which usually uses water. This cycle generates about 90% of all electric power used throughout the world, including virtually all solar thermal, biomass, coal and nuclear power plants. It is...

. As such the working fluid does not receive and reject heat at constant temperature. In the gas cycle, the refrigeration effect is equal to the product of the specific heat of the gas and the rise in temperature of the gas in the low temperature side. Therefore, for the same cooling load, a gas refrigeration cycle needs a large mass flow rate and is bulky.

Because of their lower efficiency and larger bulk, air cycle coolers are not often used nowadays in terrestrial cooling devices. However, the air cycle machine
Air cycle machine
An air cycle machine is the refrigeration unit of the environmental control system used in pressurized gas turbine-powered aircraft. Normally an aircraft has two or three of these ACM. Each ACM and its components are often referred as an Air Conditioning Pack.The air cycle cooling process uses...

 is very common on gas turbine
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....

-powered jet aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 as cooling and ventilation units, because compressed air is readily available from the engines' compressor sections. Such units also serve the purpose of pressurizing the aircraft.

Thermoelectric refrigeration


Thermoelectric cooling
Thermoelectric cooling
Thermoelectric cooling uses the Peltier effect to create a heat flux between the junction of two different types of materials. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other side against the...

 uses the Peltier effect to create a heat flux
Flux
In the various subfields of physics, there exist two common usages of the term flux, both with rigorous mathematical frameworks.* In the study of transport phenomena , flux is defined as flow per unit area, where flow is the movement of some quantity per time...

 between the junction of two different types of materials. This effect is commonly used in camping and portable coolers and for cooling electronic components and small instruments.

Magnetic refrigeration


Magnetic refrigeration, or adiabatic demagnetization, is a cooling technology based on the magnetocaloric effect, an intrinsic property of magnetic solids. The refrigerant is often a paramagnetic
Paramagnetism
Paramagnetism is a form of magnetism whereby the paramagnetic material is only attracted when in the presence of an externally applied magnetic field. In contrast with this, diamagnetic materials are repulsive when placed in a magnetic field...

 salt
Salt
In chemistry, salts are ionic compounds that result from the neutralization reaction of an acid and a base. They are composed of cations and anions so that the product is electrically neutral...

, such as cerium
Cerium
Cerium is a chemical element with the symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet . Cerium is the most abundant of the rare earth elements, making up about 0.0046% of the Earth's crust by weight...

 magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...

 nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...

. The active magnetic
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

 dipole
Dipole
In physics, there are several kinds of dipoles:*An electric dipole is a separation of positive and negative charges. The simplest example of this is a pair of electric charges of equal magnitude but opposite sign, separated by some distance. A permanent electric dipole is called an electret.*A...

s in this case are those of the electron shell
Electron shell
An electron shell may be thought of as an orbit followed by electrons around an atom's nucleus. The closest shell to the nucleus is called the "1 shell" , followed by the "2 shell" , then the "3 shell" , and so on further and further from the nucleus. The shell letters K,L,M,.....

s of the paramagnetic atoms.

A strong magnetic field is applied to the refrigerant, forcing its various magnetic dipoles to align and putting these degrees of freedom of the refrigerant into a state of lowered entropy
Entropy
Entropy is a thermodynamic property that can be used to determine the energy available for useful work in a thermodynamic process, such as in energy conversion devices, engines, or machines. Such devices can only be driven by convertible energy, and have a theoretical maximum efficiency when...

. A heat sink then absorbs the heat released by the refrigerant due to its loss of entropy. Thermal contact with the heat sink is then broken so that the system is insulated, and the magnetic field is switched off. This increases the heat capacity of the refrigerant, thus decreasing its temperature below the temperature of the heat sink.

Because few materials exhibit the needed properties at room temperature, applications have so far been limited to cryogenics
Cryogenics
In physics, cryogenics is the study of the production of very low temperature and the behavior of materials at those temperatures. A person who studies elements under extremely cold temperature is called a cryogenicist. Rather than the relative temperature scales of Celsius and Fahrenheit,...

 and research.

Other methods


Other methods of refrigeration include the air cycle machine
Air cycle machine
An air cycle machine is the refrigeration unit of the environmental control system used in pressurized gas turbine-powered aircraft. Normally an aircraft has two or three of these ACM. Each ACM and its components are often referred as an Air Conditioning Pack.The air cycle cooling process uses...

 used in aircraft; the vortex tube
Vortex tube
The vortex tube, also known as the Ranque-Hilsch vortex tube, is a mechanical device that separates a compressed gas into hot and cold streams. It has no moving parts....

 used for spot cooling, when compressed air is available; and thermoacoustic refrigeration
Thermoacoustic refrigeration
Thermoacoustic engines are thermoacoustic devices which use high-amplitude sound waves to pump heat from one place to another, or conversely use a heat difference to induce high-amplitude sound waves. In general, thermoacoustic engines can be divided into standing wave and travelling wave devices...

 using sound waves in a pressurized gas to drive heat transfer and heat exchange; steam jet cooling
Steam jet cooling
Steam jet cooling uses a high-pressure jet of steam to cool water or other fluid media. Typical uses include industrial sites, where a suitable steam supply already exists for other purposes or, historically, for air conditioning on passenger trains which use steam for heating. Steam jet cooling...

 popular in the early 1930s for air conditioning large buildings; thermoelastic cooling using a smart metal alloy stretching and relaxing. Many Stirling cycle
Stirling cycle
The Stirling cycle is a thermodynamic cycle that describes the general class of Stirling devices. This includes the original Stirling engine that was invented, developed and patented in 1816 by Reverend Dr...

 heat engines can be run backwards to act as a refrigerator, and therefore these engines have a niche use in cryogenics
Cryogenics
In physics, cryogenics is the study of the production of very low temperature and the behavior of materials at those temperatures. A person who studies elements under extremely cold temperature is called a cryogenicist. Rather than the relative temperature scales of Celsius and Fahrenheit,...

.

Unit of refrigeration


The units of refrigeration are always a unit of power. Domestic and commercial refrigerators may be rated in kJ/s, or Btu/h of cooling. For commercial and industrial refrigeration systems most of the world uses the kilowatt (kW) as the basic unit refrigeration. Typically, commercial and industrial refrigeration systems North America are rated in tons of refrigeration (TR). Historically, one TR was defined as the energy removal rate that will freeze one short ton of water at 0 °C (32 °F) in one day. This was very important because many early refrigeration systems were in ice houses. The simple unit allowed owners of these refrigeration systems measure a day's output of ice against energy consumption and compare their plant to one down the street. While ice houses make up a much smaller part of the refrigeration industry than they once did, the unit TR has remained in North America. The unit's value as historically defined is approximately 11,958 Btu/hr (3.505 kW) has been redefined to be exactly 12,000 Btu/hr (3.517 kW).

While not truly a unit, a refrigeration system's coefficient of performance (CoP) is very important in determining a system's overall efficiency. It is defined as refrigeration capacity in kW divided by the energy input in kW. While CoP is a very simple measure of performance, it is typically not used for industrial refrigeration in North America. Owners and manufacturers of these systems typically use performance factor (PF). A system's PF is defined as a system's energy input in horsepower divided by its refrigeration capacity in TR. Both CoP and PF can be applied to either the entire system or to system components. For example, an individual compressor can be rated by comparing the energy needed to run the compressor versus the expected refrigeration capacity based on inlet volume flow rate. It is important to note that both CoP and PF for a refrigeration system are only defined at specific operating conditions. Moving away from those operating conditions can dramatically change a system's performance.

See also

  • Auto-defrost
  • Beef ring
    Beef ring
    Beef rings are cooperative groups of anywhere from six to twenty-four farms, with each member of the cooperative being required to supply one animal over the course of the summer to the cooperative for slaughter...

  • Carnot Engine
  • Cold chain
    Cold chain
    A cold chain is a temperature-controlled supply chain. An unbroken cold chain is an uninterrupted series of storage and distribution activities which maintain a given temperature range...

  • Colebrook equation
  • Coolgardie safe
    Coolgardie safe
    The Coolgardie Safe is a low-tech refrigeration unit which uses the heat transfer which occurs during evaporation of water. It was named after the place where it was invented — the small mining town of Coolgardie, Western Australia, near Kalgoorlie-Boulder....

  • Einstein refrigerator
    Einstein refrigerator
    The Einstein-Szilard or Einstein refrigerator is an absorption refrigerator which has no moving parts, operates at constant pressure, and requires only a heat source to operate...

  • Freezer
  • Heat pump
    Heat pump
    A heat pump is a machine or device that effectively "moves" thermal energy from one location called the "source," which is at a lower temperature, to another location called the "sink" or "heat sink", which is at a higher temperature. An air conditioner is a particular type of heat pump, but the...

  • Heating, Ventilating and Air-conditioning
    HVAC
    HVAC refers to technology of indoor or automotive environmental comfort. HVAC system design is a major subdiscipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, and heat transfer...

  • Icebox
    Icebox
    An icebox is a compact non-mechanical refrigerator which was a common kitchen appliance before the development of safe powered refrigeration devices.- Design :...

  • Icyball
  • Laser cooling
    Laser cooling
    Laser cooling refers to the number of techniques in which atomic and molecular samples are cooled through the interaction with one or more laser light fields...

  • Pot-in-pot refrigerator
    Pot-in-pot refrigerator
    The pot-in-pot refrigerator, also known as a Zeer الزير in Arabic, is a refrigeration device which keeps food cool without electricity by using evaporative cooling. A porous outer earthenware pot, lined with wet sand, contains an inner pot within which the food is placed...

  • Pumpable ice technology
    Pumpable ice technology
    Pumpable ice technology is a technology to produce fluids or secondary refrigerants also called coolants with a viscosity of water or jelly and the cooling capacity of ice...

  • Redundant refrigeration system
  • Reefer ship
  • Refrigerant
    Refrigerant
    A refrigerant is a substance used in a heat cycle usually including, for enhanced efficiency, a reversible phase change from a liquid to a gas. Traditionally, fluorocarbons, especially chlorofluorocarbons, were used as refrigerants, but they are being phased out because of their ozone depletion...

  • Refrigerated container
  • Refrigeration cycle
  • Refrigerator
    Refrigerator
    A refrigerator is a common household appliance that consists of a thermally insulated compartment and a heat pump that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room...

  • Refrigerator car
    Refrigerator car
    A refrigerator car is a refrigerated boxcar , a piece of railroad rolling stock designed to carry perishable freight at specific temperatures. Refrigerator cars differ from simple insulated boxcars and ventilated boxcars , neither of which are fitted with cooling apparatus...

  • Refrigerator truck
    Refrigerator truck
    A refrigerator truck is a van or truck designed to carry perishable freight at specific temperatures. Like refrigerator cars, refrigerated trucks differ from simple insulated and ventilated vans , neither of which are fitted with cooling apparatus...

  • Seasonal energy efficiency ratio (SEER)
    Seasonal energy efficiency ratio
    The efficiency of air conditioners is often rated by the Seasonal Energy Efficiency Ratio which is defined by the Air Conditioning, Heating and Refrigeration Institute in its standard ARI 210/240, Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment.The SEER rating of...

  • Steam jet cooling
    Steam jet cooling
    Steam jet cooling uses a high-pressure jet of steam to cool water or other fluid media. Typical uses include industrial sites, where a suitable steam supply already exists for other purposes or, historically, for air conditioning on passenger trains which use steam for heating. Steam jet cooling...

  • Vapor-compression refrigeration
    Vapor-compression refrigeration
    Vapor-compression refrigeration is one of the many refrigeration cycles available for use. It has been and is the most widely used method for air-conditioning of large public buildings, offices, private residences, hotels, hospitals, theaters, restaurants and automobiles...


  • Additional reading

    • Refrigeration volume, ASHRAE Handbook
      ASHRAE Handbook
      The ASHRAE Handbook is the four-volume flagship publication of the nonprofit technical organization American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc....

      , ASHRAE, Inc., Atlanta, GA
    • Stoecker and Jones, Refrigeration and Air Conditioning, Tata-McGraw Hill Publishers
    • Mathur, M.L., Mehta, F.S., Thermal Engineering Vol II
    • MSN Encarta Encyclopedia

    External links