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125-419: A refrigerator , commonly fridge , is a commercial and home appliance consisting of a thermally insulated compartment and a heat pump (mechanical, electronic or chemical) that transfers heat from its inside to its external environment so that its inside is cooled to a temperature below the room temperature. Refrigeration is an essential food storage technique around the world. The low temperature reduces

250-457: A relative permittivity and relative permeability that are not identically unity. In the theory of classical electromagnetism, free space has the following properties: The vacuum of classical electromagnetism can be viewed as an idealized electromagnetic medium with the constitutive relations in SI units: relating the electric displacement field D to the electric field E and

375-671: A container of diethyl ether , which then boiled , absorbing heat from the surrounding air. The experiment even created a small amount of ice, but had no practical application at that time. In 1805, American inventor Oliver Evans described a closed vapor-compression refrigeration cycle for the production of ice by ether under vacuum. In 1820, the British scientist Michael Faraday liquefied ammonia and other gases by using high pressures and low temperatures, and in 1834, an American expatriate in Great Britain, Jacob Perkins , built

500-414: A dispenser in the door. Domestic refrigerators and freezers for food storage are made in a range of sizes. Among the smallest are Peltier-type refrigerators designed to chill beverages. A large domestic refrigerator stands as tall as a person and may be about one metre (3 ft 3 in) wide with a capacity of 0.6 m (21 cu ft). Refrigerators and freezers may be free standing, or built into

625-579: A dozen of his systems were in operation. The first gas absorption refrigeration system (compressor-less and powered by a heat-source) was developed by Edward Toussaint of France in 1859 and patented in 1860. It used gaseous ammonia dissolved in water ("aqua ammonia"). Carl von Linde , an engineering professor at the Technological University Munich in Germany, patented an improved method of liquefying gases in 1876, creating

750-449: A frozen food storage compartment may have a small section just to make ice cubes. Freezers may have drawers to store food in, or they may have no divisions (chest freezers). Refrigerators and freezers may be free-standing, or built into a kitchen's cabinet. Three distinct classes of refrigerator are common: Other specialized cooling mechanisms may be used for cooling, but have not been applied to domestic or commercial refrigerators. In

875-579: A fundamental limit within which instantaneous position and momentum , or energy and time can be measured. This far reaching consequences also threatened whether the "emptiness" of space between particles exists. The strictest criterion to define a vacuum is a region of space and time where all the components of the stress–energy tensor are zero. This means that this region is devoid of energy and momentum, and by consequence, it must be empty of particles and other physical fields (such as electromagnetism) that contain energy and momentum. In general relativity ,

1000-604: A good model for realizable vacuum, and agrees with a number of experimental observations as described next. QED vacuum has interesting and complex properties. In QED vacuum, the electric and magnetic fields have zero average values, but their variances are not zero. As a result, QED vacuum contains vacuum fluctuations ( virtual particles that hop into and out of existence), and a finite energy called vacuum energy . Vacuum fluctuations are an essential and ubiquitous part of quantum field theory. Some experimentally verified effects of vacuum fluctuations include spontaneous emission and

1125-451: A house without air-conditioning (space heating and/or cooling) refrigerators consume more energy than any other home device. In the early 1990s a competition was held among the major US manufacturers to encourage energy efficiency. Current US models that are Energy Star qualified use 50% less energy than the average 1974 model used. The most energy-efficient unit made in the US consumes about half

1250-448: A kilowatt-hour per day (equivalent to 20 W continuously). But even ordinary units are reasonably efficient; some smaller units use less than 0.2 kWh per day (equivalent to 8 W continuously). Larger units, especially those with large freezers and icemakers, may use as much as 4 kW·h per day (equivalent to 170 W continuously). The European Union uses a letter-based mandatory energy efficiency rating label , with A being

1375-431: A kitchen. The refrigerator allows the modern household to keep food fresh for longer than before. Freezers allow people to buy perishable food in bulk and eat it at leisure, and make bulk purchases . Ancient origins Ancient Iranians were among the first to invent a form of cooler utilizing the principles of evaporative cooling and radiative cooling called yakhchāls . These complexes used subterranean storage spaces,

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1500-614: A large industrial ammonia refrigerator which was powered by electric compressors (together with the Esslingen Machine Works). Its electric compressors were manufactured by the Ganz Works . At the 1896 Millennium Exhibition, Röck and the Esslingen Machine Works presented a 6-tonne capacity artificial ice producing plant. In 1906, the first large Hungarian cold store (with a capacity of 3,000 tonnes,

1625-524: A large thickly insulated above-ground domed structure, and outfitted with badgirs (wind-catchers) and series of qanats (aqueducts). Pre-electric refrigeration In modern times, before the invention of the modern electric refrigerator, icehouses and iceboxes were used to provide cool storage for most of the year. Placed near freshwater lakes or packed with snow and ice during the winter, they were once very common. Natural means are still used to cool foods today. On mountainsides, runoff from melting snow

1750-399: A liquid nitrogen backup. Alternatives to the vapor-compression cycle not in current mass production include: Many modern refrigerator/freezers have the freezer on top and the refrigerator on the bottom. Most refrigerator-freezers—except for manual defrost models or cheaper units—use what appears to be two thermostats. Only the refrigerator compartment is properly temperature controlled. When

1875-540: A luxury item, became commonplace. Freezer units are used in households as well as in industry and commerce. Commercial refrigerator and freezer units were in use for almost 40 years prior to the common home models. The freezer-over-refrigerator style had been the basic style since the 1940s, until modern, side-by-side refrigerators broke the trend. A vapor compression cycle is used in most household refrigerators, refrigerator–freezers and freezers. Newer refrigerators may include automatic defrosting , chilled water, and ice from

2000-447: A luxury item, became commonplace. In 1955 the domestic deep freezer, which was cold enough to allow the owners to freeze fresh food themselves rather than buying food already frozen with Clarence Birdseye's process, went on sale. There are walk in freezers, as the name implies, they allow for one to walk into the freezer. Safety regulations requires an emergency releases and employers should check to ensure no one will trapped inside when

2125-432: A mass spectrometer must be used in conjunction with the ionization gauge for accurate measurement. Vacuum is useful in a variety of processes and devices. Its first widespread use was in the incandescent light bulb to protect the filament from chemical degradation. The chemical inertness produced by a vacuum is also useful for electron beam welding , cold welding , vacuum packing and vacuum frying . Ultra-high vacuum

2250-479: A measurable vacuum relative to the local environment. Similarly, much higher than normal relative vacuum readings are possible deep in the Earth's ocean. A submarine maintaining an internal pressure of 1 atmosphere submerged to a depth of 10 atmospheres (98 metres; a 9.8-metre column of seawater has the equivalent weight of 1 atm) is effectively a vacuum chamber keeping out the crushing exterior water pressures, though

2375-447: A minute drag on the Earth's orbit. While the Earth does, in fact, move through a relatively dense medium in comparison to that of interstellar space, the drag is so minuscule that it could not be detected. In 1912, astronomer Henry Pickering commented: "While the interstellar absorbing medium may be simply the ether, [it] is characteristic of a gas, and free gaseous molecules are certainly there". Thereafter, however, luminiferous aether

2500-556: A much more energy than compressor refrigeration, other qualities such as silent operation or the ability to use gas can favor their use in small enclosures, a mobile environment or in environments where failure of refrigeration must not be possible. Home appliance A home appliance , also referred to as a domestic appliance , an electric appliance or a household appliance , is a machine which assists in household functions such as cooking , cleaning and food preservation . The domestic application attached to home appliance

2625-405: A partial vacuum of about 10 Pa (0.1  Torr ). A number of electrical properties become observable at this vacuum level, which renewed interest in further research. While outer space provides the most rarefied example of a naturally occurring partial vacuum, the heavens were originally thought to be seamlessly filled by a rigid indestructible material called aether . Borrowing somewhat from

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2750-400: A phenomenon known as auto-refrigeration . This cold and partially vaporized refrigerant continues through the coils or tubes of the evaporator unit. A fan blows air from the compartment ("box air") across these coils or tubes and the refrigerant completely vaporizes, drawing further latent heat from the box air. This cooled air is returned to the refrigerator or freezer compartment, and so keeps

2875-426: A proposed propulsion system for interplanetary travel . All of the observable universe is filled with large numbers of photons , the so-called cosmic background radiation , and quite likely a correspondingly large number of neutrinos . The current temperature of this radiation is about 3  K (−270.15  °C ; −454.27  °F ). The quality of a vacuum is indicated by the amount of matter remaining in

3000-554: A range of sizes. Among the smallest is a 4-litre (0.14 cu ft) Peltier refrigerator advertised as being able to hold 6 cans of beer. A large domestic refrigerator stands as tall as a person and may be about 1 metre (3.3 ft) wide with a capacity of 600 litres (21 cu ft). Some models for small households fit under kitchen work surfaces, usually about 86 centimetres (34 in) high. Refrigerators may be combined with freezers, either stacked with refrigerator or freezer above, below, or side by side. A refrigerator without

3125-423: A similar gas, as a refrigerant, with its condenser kept at around −40   °C by a second stage which uses a more conventional refrigerant. For much lower temperatures, laboratories usually purchase liquid nitrogen (−196 °C [−320.8 °F]), kept in a Dewar flask , into which the samples are suspended. Cryogenic chest freezers can achieve temperatures of down to −150 °C (−238 °F), and may include

3250-772: A small initial boost to the home appliance industry. In the Post–World War II economic expansion , the domestic use of dishwashers , and clothes dryers were part of a shift for convenience. Increasing discretionary income was reflected by a rise in miscellaneous home appliances. In America during the 1980s, the industry shipped $ 1.5 billion worth of goods each year and employed over 14,000 workers, with revenues doubling between 1982 and 1990 to $ 3.3 billion. Throughout this period, companies merged and acquired one another to reduce research and production costs and eliminate competitors, resulting in antitrust legislation . The United States Department of Energy reviews compliance with

3375-486: A uniquely American innovation that emerged in the early twentieth century. The development of these appliances is tied to the disappearance of full-time domestic servants and the desire to reduce the time-consuming activities in pursuit of more recreational time. In the early 1900s, electric and gas appliances included washing machines , water heaters , refrigerators, kettles and sewing machines . The invention of Earl Richardson's small electric clothes iron in 1903 gave

3500-552: A unit that was mounted on top of an ice box. His first device, produced over the next few years in several hundred units, was called DOMELRE . In 1914, engineer Nathaniel B. Wales of Detroit, Michigan, introduced an idea for a practical electric refrigeration unit, which later became the basis for the Kelvinator . A self-contained refrigerator, with a compressor on the bottom of the cabinet was invented by Alfred Mellowes in 1916. Mellowes produced this refrigerator commercially but

3625-477: A vacuum if he wanted and the 1277 Paris condemnations of Bishop Étienne Tempier , which required there to be no restrictions on the powers of God, led to the conclusion that God could create a vacuum if he so wished. From the 14th century onward increasingly departed from the Aristotelian perspective, scholars widely acknowledged that a supernatural void exists beyond the confines of the cosmos itself by

3750-430: A vacuum is called outgassing . All materials, solid or liquid, have a small vapour pressure , and their outgassing becomes important when the vacuum pressure falls below this vapour pressure. Outgassing has the same effect as a leak and will limit the achievable vacuum. Outgassing products may condense on nearby colder surfaces, which can be troublesome if they obscure optical instruments or react with other materials. This

3875-400: A vacuum was present, if only for an instant, between two flat plates when they were rapidly separated. There was much discussion of whether the air moved in quickly enough as the plates were separated, or, as Walter Burley postulated, whether a 'celestial agent' prevented the vacuum arising. Jean Buridan reported in the 14th century that teams of ten horses could not pull open bellows when

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4000-549: A vanishing stress–energy tensor implies, through Einstein field equations , the vanishing of all the components of the Ricci tensor . Vacuum does not mean that the curvature of space-time is necessarily flat: the gravitational field can still produce curvature in a vacuum in the form of tidal forces and gravitational waves (technically, these phenomena are the components of the Weyl tensor ). The black hole (with zero electric charge)

4125-931: A washing machine and clothes dryer could share information about load characteristics (gentle/normal, light/full), and synchronize their finish times so the wet laundry does not have to wait before being put in the dryer. Additionally, some manufacturers of home appliances are quickly beginning to place hardware that enables Internet connectivity in home appliances to allow for remote control , automation, communication with other home appliances, and more functionality enabling connected cooking. Internet-connected home appliances were especially prevalent during recent Consumer Electronics Show events. Appliance recycling consists of dismantling waste home appliances and scrapping their parts for reuse. The main types of appliances that are recycled are T.V.s, refrigerators, air conditioners, washing machines, and computers. It involves disassembly, removal of hazardous components and destruction of

4250-515: A wide array of vacuum technologies has since become available. The development of human spaceflight has raised interest in the impact of vacuum on human health, and on life forms in general. The word vacuum comes from Latin  'an empty space, void', noun use of neuter of vacuus , meaning "empty", related to vacare , meaning "to be empty". Vacuum is one of the few words in the English language that contains two consecutive instances of

4375-412: A worldwide success and was commercialized by Electrolux . Other pioneers included Charles Tellier , David Boyle, and Raoul Pictet . Carl von Linde was the first to patent and make a practical and compact refrigerator. These home units usually required the installation of the mechanical parts, motor and compressor, in the basement or an adjacent room while the cold box was located in the kitchen. There

4500-414: Is a convenient way to cool drinks, and during the winter one can keep milk fresh much longer just by keeping it outdoors. The word "refrigeratory" was used at least as early as the 17th century. Artificial refrigeration The history of artificial refrigeration began when Scottish professor William Cullen designed a small refrigerating machine in 1755. Cullen used a pump to create a partial vacuum over

4625-516: Is a non-SI unit): Vacuum is measured in units of pressure , typically as a subtraction relative to ambient atmospheric pressure on Earth. But the amount of relative measurable vacuum varies with local conditions. On the surface of Venus , where ground-level atmospheric pressure is much higher than on Earth, much higher relative vacuum readings would be possible. On the surface of the Moon with almost no atmosphere, it would be extremely difficult to create

4750-515: Is an elegant example of a region completely "filled" with vacuum, but still showing a strong curvature. In classical electromagnetism , the vacuum of free space , or sometimes just free space or perfect vacuum , is a standard reference medium for electromagnetic effects. Some authors refer to this reference medium as classical vacuum , a terminology intended to separate this concept from QED vacuum or QCD vacuum , where vacuum fluctuations can produce transient virtual particle densities and

4875-427: Is an even higher-quality vacuum, with the equivalent of just a few hydrogen atoms per cubic meter on average in intergalactic space. Vacuum has been a frequent topic of philosophical debate since ancient Greek times, but was not studied empirically until the 17th century. Clemens Timpler (1605) philosophized about the experimental possibility of producing a vacuum in small tubes. Evangelista Torricelli produced

5000-538: Is connected to the region of interest. Any fluid can be used, but mercury is preferred for its high density and low vapour pressure. Simple hydrostatic gauges can measure pressures ranging from 1 torr (100 Pa) to above atmospheric. An important variation is the McLeod gauge which isolates a known volume of vacuum and compresses it to multiply the height variation of the liquid column. The McLeod gauge can measure vacuums as high as 10  torr (0.1 mPa), which

5125-434: Is equal to the displacement of a millimeter of mercury ( mmHg ) in a manometer with 1 torr equaling 133.3223684 pascals above absolute zero pressure. Vacuum is often also measured on the barometric scale or as a percentage of atmospheric pressure in bars or atmospheres . Low vacuum is often measured in millimeters of mercury (mmHg) or pascals (Pa) below standard atmospheric pressure. "Below atmospheric" means that

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5250-410: Is forced through a metering or throttling device, also known as an expansion valve (essentially a pin-hole sized constriction in the tubing) to an area of much lower pressure. The sudden decrease in pressure results in explosive-like flash evaporation of a portion (typically about half) of the liquid. The latent heat absorbed by this flash evaporation is drawn mostly from adjacent still-liquid refrigerant,

5375-404: Is not acceptable. They can be totally silent (if a fan for air circulation is not fitted) but are less energy-efficient than other methods. "Ultra-cold" or " ultra-low temperature (ULT) " (typically −80 or −86 °C [−112 or −123 °F]) freezers, as used for storing biological samples, also generally employ two stages of cooling, but in cascade . The lower temperature stage uses methane , or

5500-573: Is not used. High vacuum systems must be clean and free of organic matter to minimize outgassing. Ultra-high vacuum systems are usually baked, preferably under vacuum, to temporarily raise the vapour pressure of all outgassing materials and boil them off. Once the bulk of the outgassing materials are boiled off and evacuated, the system may be cooled to lower vapour pressures and minimize residual outgassing during actual operation. Some systems are cooled well below room temperature by liquid nitrogen to shut down residual outgassing and simultaneously cryopump

5625-419: Is of great concern to space missions, where an obscured telescope or solar cell can ruin an expensive mission. The most prevalent outgassing product in vacuum systems is water absorbed by chamber materials. It can be reduced by desiccating or baking the chamber, and removing absorbent materials. Outgassed water can condense in the oil of rotary vane pumps and reduce their net speed drastically if gas ballasting

5750-437: Is referred to as ' QED vacuum ' to distinguish it from the vacuum of quantum chromodynamics , denoted as QCD vacuum . QED vacuum is a state with no matter particles (hence the name), and no photons . As described above, this state is impossible to achieve experimentally. (Even if every matter particle could somehow be removed from a volume, it would be impossible to eliminate all the blackbody photons .) Nonetheless, it provides

5875-422: Is still blown from the freezer. Newer refrigerators may include: These older freezer compartments were the main cooling body of the refrigerator, and only maintained a temperature of around −6 °C (21 °F), which is suitable for keeping food for a week. Later advances included automatic ice units and self compartmentalized freezing units. Domestic refrigerators and freezers for food storage are made in

6000-447: Is still found in many old systems. Refrigeration, continually operated, typically consumes up to 50% of the energy used by a supermarket. Doors, made of glass to allow inspection of contents, improve efficiency significantly over open display cases, which use 1.3 times the energy. In 1913, the first electric refrigerators for home and domestic use were invented and produced by Fred W. Wolf of Fort Wayne, Indiana, with models consisting of

6125-516: Is the highest qualification, for those refrigerators that are at least 30% more efficient than Federal standards. About 82% of the Energy Star qualified refrigerators are Tier 1, with 13% qualifying as Tier 2, and just 5% at Tier 3. Besides the standard style of compressor refrigeration used in ordinary household refrigerators and freezers, there are technologies such as absorption and magnetic refrigeration . Although these designs generally use

6250-454: Is the lowest direct measurement of pressure that is possible with current technology. Other vacuum gauges can measure lower pressures, but only indirectly by measurement of other pressure-controlled properties. These indirect measurements must be calibrated via a direct measurement, most commonly a McLeod gauge. The kenotometer is a particular type of hydrostatic gauge, typically used in power plants using steam turbines. The kenotometer measures

6375-606: Is tied to the definition of appliance as "an instrument or device designed for a particular use or function". Collins English Dictionary defines "home appliance" as: "devices or machines, usually electrical, that are in your home and which you use to do jobs such as cleaning or cooking". The broad usage allows for nearly any device intended for domestic use to be a home appliance, including consumer electronics as well as stoves , refrigerators , toasters and air conditioners . The development of self-contained electric and gas-powered appliances, an American innovation, emerged in

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6500-463: Is used in the kitchen, including: juicers , electric mixers , meat grinders , coffee grinders , deep fryers , herb grinders , food processors , electric kettles , waffle irons , coffee makers , blenders , rice cookers , toasters and exhaust hoods . In the 1960s the product design for appliances such as washing machines , refrigerators , and electric toasters shifted away from Streamline Moderne and embraced technological advances in

6625-443: Is used in the study of atomically clean substrates, as only a very good vacuum preserves atomic-scale clean surfaces for a reasonably long time (on the order of minutes to days). High to ultra-high vacuum removes the obstruction of air, allowing particle beams to deposit or remove materials without contamination. This is the principle behind chemical vapor deposition , physical vapor deposition , and dry etching which are essential to

6750-412: Is useful for flywheel energy storage and ultracentrifuges . Vacuums are commonly used to produce suction , which has an even wider variety of applications. The Newcomen steam engine used vacuum instead of pressure to drive a piston. In the 19th century, vacuum was used for traction on Isambard Kingdom Brunel 's experimental atmospheric railway . Vacuum brakes were once widely used on trains in

6875-458: Is using a separate fan for each compartment, the Dual Fan approach. Doing so allows for separate control and airflow on a single compressor system. An absorption refrigerator works differently from a compressor refrigerator, using a source of heat , such as combustion of liquefied petroleum gas , solar thermal energy or an electric heating element. These heat sources are much quieter than

7000-475: The Heading Indicator (HI) ) are typically vacuum-powered, as protection against loss of all (electrically powered) instruments, since early aircraft often did not have electrical systems, and since there are two readily available sources of vacuum on a moving aircraft, the engine and an external venturi. Vacuum induction melting uses electromagnetic induction within a vacuum. Maintaining a vacuum in

7125-503: The Lamb shift . Coulomb's law and the electric potential in vacuum near an electric charge are modified. Theoretically, in QCD multiple vacuum states can coexist. The starting and ending of cosmological inflation is thought to have arisen from transitions between different vacuum states. For theories obtained by quantization of a classical theory, each stationary point of the energy in

7250-1145: The National Appliance Energy Conservation Act of 1987, which required manufacturers to reduce the energy consumption of the appliances by 25% every five years. In the 1990s, the appliance industry was very consolidated, with over 90% of the products being sold by just five companies. For example, in 1991, dishwasher manufacturing market share was split between General Electric with 40% market share, Whirlpool with 31%, Electrolux with 20%, Maytag with 7% and Thermador with just 2%. Major appliances, also known as white goods, comprise major household appliances and may include: air conditioners, dishwashers, clothes dryers, drying cabinets , freezers , refrigerators, kitchen stoves , water heaters, washing machines, trash compactors , microwave ovens , and induction cookers . White goods were typically painted or enameled white, and many of them still are. Small appliances are typically small household electrical machines, also very useful and easily carried and installed. Yet another category

7375-453: The Sun and the dynamic pressure of the solar winds , so the definition of pressure becomes difficult to interpret. The thermosphere in this range has large gradients of pressure, temperature and composition, and varies greatly due to space weather . Astrophysicists prefer to use number density to describe these environments, in units of particles per cubic centimetre. But although it meets

7500-431: The condenser is an important aspect of the efficient operation of steam turbines . A steam jet ejector or liquid ring vacuum pump is used for this purpose. The typical vacuum maintained in the condenser steam space at the exhaust of the turbine (also called condenser backpressure) is in the range 5 to 15 kPa (absolute), depending on the type of condenser and the ambient conditions. Evaporation and sublimation into

7625-541: The configuration space gives rise to a single vacuum. String theory is believed to have a huge number of vacua – the so-called string theory landscape . Outer space has very low density and pressure, and is the closest physical approximation of a perfect vacuum. But no vacuum is truly perfect, not even in interstellar space, where there are still a few hydrogen atoms per cubic meter. Stars, planets, and moons keep their atmospheres by gravitational attraction, and as such, atmospheres have no clearly delineated boundary:

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7750-420: The icebox , which had been a common household appliance for almost a century and a half. The United States Food and Drug Administration recommends that the refrigerator be kept at or below 4 °C (40 °F) and that the freezer be regulated at −18 °C (0 °F). The first cooling systems for food involved ice. Artificial refrigeration began in the mid-1750s, and developed in the early 1800s. In 1834,

7875-458: The magnetic field or H -field H to the magnetic induction or B -field B . Here r is a spatial location and t is time. In quantum mechanics and quantum field theory , the vacuum is defined as the state (that is, the solution to the equations of the theory) with the lowest possible energy (the ground state of the Hilbert space ). In quantum electrodynamics this vacuum

8000-431: The pneuma of Stoic physics , aether came to be regarded as the rarefied air from which it took its name, (see Aether (mythology) ). Early theories of light posited a ubiquitous terrestrial and celestial medium through which light propagated. Additionally, the concept informed Isaac Newton 's explanations of both refraction and of radiant heat. 19th century experiments into this luminiferous aether attempted to detect

8125-484: The 1 atm inside the submarine would not normally be considered a vacuum. Therefore, to properly understand the following discussions of vacuum measurement, it is important that the reader assumes the relative measurements are being done on Earth at sea level, at exactly 1 atmosphere of ambient atmospheric pressure. The SI unit of pressure is the pascal (symbol Pa), but vacuum is often measured in torrs , named for an Italian physicist Torricelli (1608–1647). A torr

8250-410: The 17th century. This idea, influenced by Stoic physics , helped to segregate natural and theological concerns. Almost two thousand years after Plato, René Descartes also proposed a geometrically based alternative theory of atomism, without the problematic nothing–everything dichotomy of void and atom. Although Descartes agreed with the contemporary position, that a vacuum does not occur in nature,

8375-482: The 1920s; up to this time freezing was not an auxiliary function of the modern refrigerator. The first refrigerator to see widespread use was the General Electric "Monitor-Top" refrigerator introduced in 1927, so-called, by the public, because of its resemblance to the gun turret on the ironclad warship USS Monitor of the 1860s. The compressor assembly, which emitted a great deal of heat, was placed above

8500-415: The 1960s, embracing new materials and colors. Consumer electronics , often referred to as brown goods, include items like TVs and computers. There is a growing trend towards home automation and internet-connected appliances. Recycling of home appliances involves dismantling and recovering materials. While many appliances have existed for centuries, the self-contained electric or gas powered appliances are

8625-567: The 1970s and 1980s, even though environmental issues led to the banning of very effective (Freon) refrigerants. Early refrigerator models (from 1916) had a cold compartment for ice cube trays. From the late 1920s fresh vegetables were successfully processed through freezing by the Postum Company (the forerunner of General Foods ), which had acquired the technology when it bought the rights to Clarence Birdseye 's successful fresh freezing methods. The majority of refrigerators were white in

8750-684: The 1980s, black became fashionable. In the late 1990s stainless steel came into vogue. Since 1961 the Color Marketing Group has attempted to coordinate the colors of appliances and other consumer goods. Freezer units are used in households and in industry and commerce. Food stored at or below −18 °C (0 °F) is safe indefinitely. Most household freezers maintain temperatures from −23 to −18 °C (−9 to 0 °F), although some freezer-only units can achieve −34 °C (−29 °F) and lower. Refrigerator freezers generally do not achieve lower than −23 °C (−9 °F), since

8875-918: The Internet. Some such appliances were traditionally finished with genuine or imitation wood, hence the name. This has become rare but the name has stuck, even for goods that are unlikely ever to have had a wooden case (e.g. camcorders). In the 2010s, this distinction is absent in large big box consumer electronics stores , which sell both entertainment, communication, and home office devices and kitchen appliances such as refrigerators. The highest selling consumer electronics products are compact discs . Examples are: home electronics, radio receivers , TV sets , VCRs , CD and DVD players , digital cameras , camcorders , still cameras , clocks , alarm clocks , computers , video game consoles , HiFi and home cinema , telephones and answering machines . A survey conducted in 2020 of more than thirteen thousand people in

9000-536: The MFP of room temperature air is roughly 100 mm, which is on the order of everyday objects such as vacuum tubes . The Crookes radiometer turns when the MFP is larger than the size of the vanes. Vacuum quality is subdivided into ranges according to the technology required to achieve it or measure it. These ranges were defined in ISO 3529-1:2019 as shown in the following table (100 Pa corresponds to 0.75 Torr; Torr

9125-452: The UK but, except on heritage railways , they have been replaced by air brakes . Manifold vacuum can be used to drive accessories on automobiles . The best known application is the vacuum servo , used to provide power assistance for the brakes . Obsolete applications include vacuum-driven windscreen wipers and Autovac fuel pumps. Some aircraft instruments ( Attitude Indicator (AI) and

9250-437: The UK revealed how long appliance owners had their appliances before needing to replace them due to a fault, deteriorating performance, or the age of the appliance. There is a trend of networking home appliances together, and combining their controls and key functions. For instance, energy distribution could be managed more evenly so that when a washing machine is on, an oven can go into a delayed start mode, or vice versa. Or,

9375-482: The United States in the 1930s as prices fell and non-toxic, non-flammable synthetic refrigerants such as Freon-12 (R-12) were introduced. However, R-12 proved to be damaging to the ozone layer , causing governments to issue a ban on its use in new refrigerators and air-conditioning systems in 1994. The less harmful replacement for R-12, R-134a (tetrafluoroethane), has been in common use since 1990, but R-12

9500-424: The absolute pressure is equal to the current atmospheric pressure. In other words, most low vacuum gauges that read, for example 50.79 Torr. Many inexpensive low vacuum gauges have a margin of error and may report a vacuum of 0 Torr but in practice this generally requires a two-stage rotary vane or other medium type of vacuum pump to go much beyond (lower than) 1 torr. Many devices are used to measure

9625-613: The box air cold. Note that the cool air in the refrigerator or freezer is still warmer than the refrigerant in the evaporator. Refrigerant leaves the evaporator, now fully vaporized and slightly heated, and returns to the compressor inlet to continue the cycle. Modern domestic refrigerators are extremely reliable because motor and compressor are integrated within a welded container, "sealed unit", with greatly reduced likelihood of leakage or contamination. By comparison, externally-coupled refrigeration compressors, such as those in automobile air conditioning, inevitably leak fluid and lubricant past

9750-410: The cabinet, and enclosed by a decorative ring. Over a million units were produced. As the refrigerating medium, these refrigerators used either sulfur dioxide , which is corrosive to the eyes and may cause loss of vision, painful skin burns and lesions, or methyl formate , which is highly flammable, harmful to the eyes, and toxic if inhaled or ingested. The introduction of Freon in the 1920s expanded

9875-409: The compressor as high-pressure superheated vapor. The superheated vapor travels under pressure through coils or tubes that make up the condenser ; the coils or tubes are passively cooled by exposure to air in the room. The condenser cools the vapor, which liquefies. As the refrigerant leaves the condenser, it is still under pressure but is now only slightly above room temperature. This liquid refrigerant

10000-564: The compressor motor in a typical refrigerator. A fan or pump might be the only mechanical moving parts; reliance on convection is considered impractical. Other uses of an absorption refrigerator (or "chiller") include large systems used in office buildings or complexes such as hospitals and universities. These large systems are used to chill a brine solution that is circulated through the building. The Peltier effect uses electricity to pump heat directly; refrigerators employing this system are sometimes used for camping, or in situations where noise

10125-523: The definition of outer space, the atmospheric density within the first few hundred kilometers above the Kármán line is still sufficient to produce significant drag on satellites . Most artificial satellites operate in this region called low Earth orbit and must fire their engines every couple of weeks or a few times a year (depending on solar activity). The drag here is low enough that it could theoretically be overcome by radiation pressure on solar sails ,

10250-417: The denser surrounding material continuum would immediately fill any incipient rarity that might give rise to a void. In his Physics , book IV, Aristotle offered numerous arguments against the void: for example, that motion through a medium which offered no impediment could continue ad infinitum , there being no reason that something would come to rest anywhere in particular. In the medieval Muslim world ,

10375-456: The density of atmospheric gas simply decreases with distance from the object. The Earth's atmospheric pressure drops to about 32 millipascals (4.6 × 10  psi) at 100 kilometres (62 mi) of altitude, the Kármán line , which is a common definition of the boundary with outer space. Beyond this line, isotropic gas pressure rapidly becomes insignificant when compared to radiation pressure from

10500-446: The early 1950s, but between the mid-1950s and the present, manufacturers and designers have added color. Pastel colors, such as pink and turquoise, gained popularity in the late 1950s and early 1960s. Certain versions also had brushed chrome plating, which is akin to a stainless steel appearance. During the latter part of the 1960s and the early 1970s, earth tone colors were popular, including Harvest Gold , Avocado Green and almond. In

10625-421: The early 20th century. This evolution is linked to the decline of full-time domestic servants and desire to reduce household chores, allowing for more leisure time. Early appliances included washing machines , water heaters , refrigerators, and sewing machines . The industry saw significant growth post-World War II, with the introduction of dishwashers and clothes dryers . By the 1980s, the appliance industry

10750-609: The equipment to recover materials, generally by shredding, sorting and grading. Vacuum The quality of a partial vacuum refers to how closely it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum. For example, a typical vacuum cleaner produces enough suction to reduce air pressure by around 20%. But higher-quality vacuums are possible. Ultra-high vacuum chambers, common in chemistry, physics, and engineering, operate below one trillionth (10 ) of atmospheric pressure (100 nPa), and can reach around 100 particles/cm . Outer space

10875-701: The fabrication of semiconductors and optical coatings , and to surface science . The reduction of convection provides the thermal insulation of thermos bottles . Deep vacuum lowers the boiling point of liquids and promotes low temperature outgassing which is used in freeze drying , adhesive preparation, distillation , metallurgy , and process purging. The electrical properties of vacuum make electron microscopes and vacuum tubes possible, including cathode-ray tubes . Vacuum interrupters are used in electrical switchgear. Vacuum arc processes are industrially important for production of certain grades of steel or high purity materials. The elimination of air friction

11000-768: The fabrication of sheet metal . A choice in color, as well as fashionable accessory , could be offered to the mass market without increasing production cost . Home appliances were sold as space-saving ensembles. Consumer electronics or home electronics are electronic ( analog or digital ) equipment intended for everyday use, typically in private homes. Consumer electronics include devices used for entertainment , communications and recreation . In British English, they are often called brown goods by producers and sellers, to distinguish them from " white goods " which are meant for housekeeping tasks, such as washing machines and refrigerators, although nowadays, these could be considered brown goods, some of these being connected to

11125-454: The first century AD. Following Plato , however, even the abstract concept of a featureless void faced considerable skepticism: it could not be apprehended by the senses, it could not, itself, provide additional explanatory power beyond the physical volume with which it was commensurate and, by definition, it was quite literally nothing at all, which cannot rightly be said to exist. Aristotle believed that no void could occur naturally, because

11250-445: The first laboratory vacuum in 1643, and other experimental techniques were developed as a result of his theories of atmospheric pressure. A Torricellian vacuum is created by filling with mercury a tall glass container closed at one end, and then inverting it in a bowl to contain the mercury (see below). Vacuum became a valuable industrial tool in the 20th century with the introduction of incandescent light bulbs and vacuum tubes , and

11375-439: The first reliable and efficient compressed-ammonia refrigerator. His new process made possible the use of gases such as ammonia (NH 3 ), sulfur dioxide (SO 2 ) and methyl chloride (CH 3 Cl) as refrigerants, which were widely used for that purpose until the late 1920s despite safety concerns. In 1895 he discovered the refrigeration cycle . In 1894, Hungarian inventor and industrialist István Röck started to manufacture

11500-528: The first working vapor-compression refrigeration , using the same technology seen in air conditioners , system was built. The first commercial ice-making machine was invented in 1854. In 1913, refrigerators for home use were invented. In 1923 Frigidaire introduced the first self-contained unit. The introduction of Freon in the 1920s expanded the refrigerator market during the 1930s. Home freezers as separate compartments (larger than necessary just for ice cubes) were introduced in 1940. Frozen foods , previously

11625-438: The first working vapor-compression refrigeration system. It was a closed-cycle device that could operate continuously. A similar attempt was made in 1842, by American physician, John Gorrie , who built a working prototype, but it was a commercial failure. American engineer Alexander Twining took out a British patent in 1850 for a vapor compression system that used ether. The first practical vapor compression refrigeration system

11750-432: The flexure of the diaphragm, which results in a change in capacitance. These gauges are effective from 10  torr to 10  torr, and beyond. Thermal conductivity gauges rely on the fact that the ability of a gas to conduct heat decreases with pressure. In this type of gauge, a wire filament is heated by running current through it. A thermocouple or Resistance Temperature Detector (RTD) can then be used to measure

11875-414: The freezer temperature will have no effect on the refrigerator temperature. The freezer control may also be adjusted to compensate for any refrigerator adjustment. This means the refrigerator may become too warm. However, because only enough air is diverted to the refrigerator compartment, the freezer usually re-acquires the set temperature quickly, unless the door is opened. When a door is opened, either in

12000-426: The gas density decreases, the MFP increases, and when the MFP is longer than the chamber, pump, spacecraft, or other objects present, the continuum assumptions of fluid mechanics do not apply. This vacuum state is called high vacuum , and the study of fluid flows in this regime is called particle gas dynamics. The MFP of air at atmospheric pressure is very short, 70  nm , but at 100  mPa (≈ 10   Torr )

12125-416: The gases being measured. Ionization gauges are used in ultrahigh vacuum. They come in two types: hot cathode and cold cathode. In the hot cathode version an electrically heated filament produces an electron beam. The electrons travel through the gauge and ionize gas molecules around them. The resulting ions are collected at a negative electrode. The current depends on the number of ions, which depends on

12250-490: The hemispheres, teams of horses could not separate two hemispheres from which the air had been partially evacuated. Robert Boyle improved Guericke's design and with the help of Robert Hooke further developed vacuum pump technology. Thereafter, research into the partial vacuum lapsed until 1850 when August Toepler invented the Toepler pump and in 1855 when Heinrich Geissler invented the mercury displacement pump, achieving

12375-871: The largest in Europe) opened in Tóth Kálmán Street, Budapest, the machine was manufactured by the Ganz Works . Until nationalisation after the Second World War, large-scale industrial refrigerator production in Hungary was in the hands of Röck and Ganz Works. Commercial refrigerator and freezer units, which go by many other names, were in use for almost 40 years prior to the common home models. They used gas systems such as ammonia (R-717) or sulfur dioxide (R-764), which occasionally leaked, making them unsafe for home use. Practical household refrigerators were introduced in 1915 and gained wider acceptance in

12500-420: The lid or door on top, sacrificing convenience for efficiency and partial immunity to power outages. Many modern upright freezers come with an ice dispenser built into their door. Some upscale models include thermostat displays and controls. Home freezers as separate compartments (larger than necessary just for ice cubes), or as separate units, were introduced in the United States in 1940. Frozen foods, previously

12625-413: The more humid refrigerator air is mixed with the dry freezer air. Multiple manufacturers offer dual compressor models. These models have separate freezer and refrigerator compartments that operate independently of each other, sometimes mounted within a single cabinet. Each has its own separate compressor, condenser and evaporator coils, insulation, thermostat, and door. A hybrid between the two designs

12750-525: The most efficient, instead of the Energy Star. For US refrigerators, the Consortium on Energy Efficiency (CEE) further differentiates between Energy Star qualified refrigerators. Tier 1 refrigerators are those that are 20% to 24.9% more efficient than the Federal minimum standards set by the National Appliance Energy Conservation Act (NAECA). Tier 2 are those that are 25% to 29.9% more efficient. Tier 3

12875-413: The physicist and Islamic scholar Al-Farabi wrote a treatise rejecting the existence of the vacuum in the 10th century. He concluded that air's volume can expand to fill available space, and therefore the concept of a perfect vacuum was incoherent. According to Ahmad Dallal , Abū Rayhān al-Bīrūnī states that "there is no observable evidence that rules out the possibility of vacuum". The suction pump

13000-413: The port was sealed. The 17th century saw the first attempts to quantify measurements of partial vacuum. Evangelista Torricelli 's mercury barometer of 1643 and Blaise Pascal 's experiments both demonstrated a partial vacuum. In 1654, Otto von Guericke invented the first vacuum pump and conducted his famous Magdeburg hemispheres experiment, showing that, owing to atmospheric pressure outside

13125-429: The pressure in a vacuum, depending on what range of vacuum is needed. Hydrostatic gauges (such as the mercury column manometer ) consist of a vertical column of liquid in a tube whose ends are exposed to different pressures. The column will rise or fall until its weight is in equilibrium with the pressure differential between the two ends of the tube. The simplest design is a closed-end U-shaped tube, one side of which

13250-631: The pressure in the gauge. Hot cathode gauges are accurate from 10  torr to 10 torr. The principle behind cold cathode version is the same, except that electrons are produced in a discharge created by a high voltage electrical discharge. Cold cathode gauges are accurate from 10  torr to 10  torr. Ionization gauge calibration is very sensitive to construction geometry, chemical composition of gases being measured, corrosion and surface deposits. Their calibration can be invalidated by activation at atmospheric pressure or low vacuum. The composition of gases at high vacuums will usually be unpredictable, so

13375-410: The refrigerator gets too warm, the thermostat starts the cooling process and a fan circulates the air around the freezer. During this time, the refrigerator also gets colder. The freezer control knob only controls the amount of air that flows into the refrigerator via a damper system. Changing the refrigerator temperature will inadvertently change the freezer temperature in the opposite direction. Changing

13500-492: The refrigerator market during the 1930s and provided a safer, low-toxicity alternative to previously used refrigerants. Separate freezers became common during the 1940s; the term for the unit, popular at the time, was deep freeze . These devices, or appliances , did not go into mass production for use in the home until after World War II. The 1950s and 1960s saw technical advances like automatic defrosting and automatic ice making. More efficient refrigerators were developed in

13625-420: The refrigerator or the freezer, the fan in some units stops immediately to prevent excessive frost build up on the freezer's evaporator coil, because this coil is cooling two areas. When the freezer reaches temperature, the unit cycles off, no matter what the refrigerator temperature is. Modern computerized refrigerators do not use the damper system. The computer manages fan speed for both compartments, although air

13750-450: The reproduction rate of bacteria , so the refrigerator lowers the rate of spoilage . A refrigerator maintains a temperature a few degrees above the freezing point of water. The optimal temperature range for perishable food storage is 3 to 5 °C (37 to 41 °F). A freezer is a specialized refrigerator, or portion of a refrigerator, that maintains its contents’ temperature below the freezing point of water. The refrigerator replaced

13875-422: The same coolant loop serves both compartments: Lowering the freezer compartment temperature excessively causes difficulties in maintaining above-freezing temperature in the refrigerator compartment. Domestic freezers can be included as a separate compartment in a refrigerator, or can be a separate appliance. Domestic freezers may be either upright, resembling a refrigerator, or chest freezers , wider than tall with

14000-454: The shaft seals. This leads to a requirement for periodic recharging and, if ignored, possible compressor failure. Refrigerators with two compartments need special design to control the cooling of refrigerator or freezer compartments. Typically, the compressors and condenser coils are mounted at the top of the cabinet, with a single fan to cool them both. This arrangement has a few downsides: each compartment cannot be controlled independently and

14125-406: The success of his namesake coordinate system and more implicitly, the spatial–corporeal component of his metaphysics would come to define the philosophically modern notion of empty space as a quantified extension of volume. By the ancient definition however, directional information and magnitude were conceptually distinct. Medieval thought experiments into the idea of a vacuum considered whether

14250-439: The system, so that a high quality vacuum is one with very little matter left in it. Vacuum is primarily measured by its absolute pressure , but a complete characterization requires further parameters, such as temperature and chemical composition. One of the most important parameters is the mean free path (MFP) of residual gases, which indicates the average distance that molecules will travel between collisions with each other. As

14375-408: The system. Fluids cannot generally be pulled, so a vacuum cannot be created by suction . Suction can spread and dilute a vacuum by letting a higher pressure push fluids into it, but the vacuum has to be created first before suction can occur. The easiest way to create an artificial vacuum is to expand the volume of a container. For example, the diaphragm muscle expands the chest cavity, which causes

14500-455: The temperature of the filament. This temperature is dependent on the rate at which the filament loses heat to the surrounding gas, and therefore on the thermal conductivity. A common variant is the Pirani gauge which uses a single platinum filament as both the heated element and RTD. These gauges are accurate from 10 torr to 10  torr, but they are sensitive to the chemical composition of

14625-403: The unit gets locked as hypothermia is possible if one is in freezer for longer periods of time. A vapor compression cycle is used in most household refrigerators, refrigerator–freezers and freezers. In this cycle, a circulating refrigerant such as R134a enters a compressor as low-pressure vapor at or slightly below the temperature of the refrigerator interior. The vapor is compressed and exits

14750-431: The vacuum in the steam space of the condenser, that is, the exhaust of the last stage of the turbine. Mechanical or elastic gauges depend on a Bourdon tube, diaphragm, or capsule, usually made of metal, which will change shape in response to the pressure of the region in question. A variation on this idea is the capacitance manometer , in which the diaphragm makes up a part of a capacitor. A change in pressure leads to

14875-443: The vowel u . Historically, there has been much dispute over whether such a thing as a vacuum can exist. Ancient Greek philosophers debated the existence of a vacuum, or void, in the context of atomism , which posited void and atom as the fundamental explanatory elements of physics. Lucretius argued for the existence of vacuum in the first century BC and Hero of Alexandria tried unsuccessfully to create an artificial vacuum in

15000-478: Was a 1922 model that consisted of a wooden cold box, water-cooled compressor, an ice cube tray and a 0.25-cubic-metre (9 cu ft) compartment, and cost $ 714. (A 1922 Model-T Ford cost about $ 476.) By 1923, Kelvinator held 80 percent of the market for electric refrigerators. Also in 1923 Frigidaire introduced the first self-contained unit. About this same time porcelain-covered metal cabinets began to appear. Ice cube trays were introduced more and more during

15125-457: Was booming, leading to mergers and antitrust legislation. The US National Appliance Energy Conservation Act of 1987 mandated a 25% reduction in energy consumption every five years. By the 1990s, five companies dominated over 90% of the market. Major appliances , often called white goods, include items like refrigerators and washing machines, while small appliances encompass items such as toasters and coffee makers . Product design shifted in

15250-594: Was bought out by William C. Durant in 1918, who started the Frigidaire company to mass-produce refrigerators. In 1918, Kelvinator company introduced the first refrigerator with any type of automatic control. The absorption refrigerator was invented by Baltzar von Platen and Carl Munters from Sweden in 1922, while they were still students at the Royal Institute of Technology in Stockholm. It became

15375-556: Was built by James Harrison , a Scottish Australian. His 1856 patent was for a vapor compression system using ether, alcohol or ammonia. He built a mechanical ice-making machine in 1851 on the banks of the Barwon River at Rocky Point in Geelong , Victoria , and his first commercial ice-making machine followed in 1854. Harrison also introduced commercial vapor-compression refrigeration to breweries and meat packing houses, and by 1861,

15500-500: Was described by Arab engineer Al-Jazari in the 13th century, and later appeared in Europe from the 15th century. European scholars such as Roger Bacon , Blasius of Parma and Walter Burley in the 13th and 14th century focused considerable attention on issues concerning the concept of a vacuum. The commonly held view that nature abhorred a vacuum was called horror vacui . There was even speculation that even God could not create

15625-461: Was discarded. Later, in 1930, Paul Dirac proposed a model of the vacuum as an infinite sea of particles possessing negative energy, called the Dirac sea . This theory helped refine the predictions of his earlier formulated Dirac equation , and successfully predicted the existence of the positron , confirmed two years later. Werner Heisenberg 's uncertainty principle , formulated in 1927, predicted

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