A refrigerator (often called a "fridge" for short) is a cooling Cooling is the transfer of thermal energy via thermal radiation, heat conduction or convection. It may also refer to: appliance comprising a thermally insulated The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer. Heat energy can be transferred by conduction, convection, radiation or by actual movement of material from one location to another. For the purposes of this discussion only the first three compartment and a heat pump A heat pump is a machine or device that moves heat from one location to another location (the 'sink' or 'heat sink') using mechanical work. Most heat pump technology moves heat from a low temperature heat source to a higher temperature heat sink. Common examples are food refrigerators and freezers, air conditioners, and reversible-cycle heat pumps—chemical or mechanical means—to transfer heat from it to the external environment, cooling the contents to a temperature below ambient. Cooling is a popular food storage technique Food preservation is the process of treating and handling food to stop or greatly slow down spoilage caused or accelerated by micro-organisms. Some methods, however, use benign bacteria, yeasts or fungi to add specific qualities and to preserve food (e.g., cheese, wine). Maintaining or creating nutritional value, texture and flavour is important in developed countries and works by decreasing the reproduction rate of bacteria. The device is thus used to reduce the rate of spoilage of foodstuffs. A device described as a "refrigerator" maintains a temperature a few degrees above the freezing point The melting point of a solid is the temperature at which the vapor pressure of the solid and the liquid are equal. At the melting point the solid and liquid phase exist in equilibrium. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point. Because of the ability of some substances to of water. Optimum temperature range for perishable food storage is 1.7 to 3.3 Celsius = 33 to 38 Fahrenheit. A similar device which maintains a temperature below the freezing point of water is called a "freezer." The refrigerator is a relatively modern invention among kitchen appliances Home appliances are electrical/mechanical appliances which accomplish some household functions, such as cooking or cleaning. It replaced the icebox An Icebox was the common appliance for providing refrigeration in the home before safe refrigerants made compact mechanical refrigerators feasible, which had been a common household appliance for almost a century and a half prior. For this reason, a refrigerator is sometimes referred to as an "icebox."

Contents

Freezer

Freezer units are used in households and in industry and commerce. Most freezers operate around 0 °F (−18 °C). Domestic freezers can be included as a separate compartment in a refrigerator, or can be a separate appliance. Domestic freezers are generally upright units resembling refrigerators, or chests resembling upright units laid on their side. Many upright modern freezers come with an ice dispenser built into their door.

Commercial and domestic refrigerators

Commercial fridge and freezer units, which go by many other names, were in use for almost 40 years prior to the common home models. They used toxic gas systems, which occasionally leaked, making them unsafe for home use. Practical household refrigerators were introduced in 1915 and gained wider acceptance in the United States in the 1930s as prices fell and non-toxic, non-flammable synthetic refrigerants A refrigerant is a substance used in a heat cycle usually including, for enhanced efficiency, a reversible phase change from a gas to a liquid. Traditionally, fluorocarbons, especially chlorofluorocarbons were used as refrigerants, but they are being phased out because of their ozone depletion effects. Other common refrigerants used in various such as Freon A chlorofluorocarbon is an organic compound that contains carbon, chlorine, and fluorine, produced as a volatile derivative of methane and ethane. A common subclass is the hydrochlorofluorocarbons (HCFCs), which contain hydrogen, as well. They are also commonly known by the DuPont trade name Freon. The most common representative is or R-12 Dichlorodifluoromethane , usually sold under the brand name Freon-12, is a chlorofluorocarbon halomethane (CFC), used as a refrigerant and aerosol spray propellant. Complying with the Montreal Protocol, its manufacture was banned in the United States along with many other countries in 1994 due to concerns about damage to the ozone layer. It is were introduced. It is notable that while 60% of households in the US owned a refrigerator by the 1930s, it was not until 40 years later, in the 1970s, that the refrigerator achieved a similar level of penetration in the United Kingdom.[1]

History

See also: Timeline of low-temperature technology The following is a timeline of low-temperature technology and cryogenic technology A Monitor-style (General Electric format), more like an icebox with its refrigerating mechanisms on top.

Before the invention of the refrigerator, icehouses Ice houses originally invented in Persia were buildings used to store ice throughout the year, prior to the invention of the refrigerator. The most common designs involved underground chambers, usually man-made, which were built close to natural sources of winter ice such as freshwater lakes 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 is a convenient way to cool drinks, and during the winter one can keep milk fresh much longer just by keeping it outdoors.

In the 11th century, the Persian physicist Physics in medieval Islam included experimental physics, mathematical physics and theoretical physics. The fields of physics that were studied by Muslim scientists during this time also included optics and magnetism , mechanics (including statics, dynamics, kinematics and motion), and astrophysics (see Islamic astronomy). These studies flourished and chemist Alchemy and chemistry in Islam refers to the study of both traditional alchemy and early practical chemistry by scientists in the medieval Islamic world. The word alchemy itself was derived from the Arabic word الكيمياء al-kimia, in turn derived from the Persian word کيميا kimia Ibn Sina Abū ‘Alī al-Ḥusayn ibn ‘Abd Allāh ibn Sīnā', known as Abū Alī Sīnā or, more commonly, Ibn Sīnā (Arabic: ابن سینا‎), but most commonly known in English by his Latinized name Avicenna (Greek: Aβιτζιανός, Avitzianós), (c. 980 - 1037) was a polymath of Persian origin and the foremost physician and philosopher of his (Avicenna) invented the refrigerated coil A dehumidifier is typically a household appliance that reduces the level of humidity in the air, usually for health reasons. Humid air can cause mold and mildew to grow inside homes, which has various health risks. Very high humidity levels are also unpleasant for human beings, can cause condensation and can make it hard to dry laundry or sleep, which condenses aromatic In organic chemistry, the structures of some rings of atoms are unexpectedly stable. Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibit a stabilization stronger than would be expected by the stabilization of conjugation alone. It can also be considered a manifestation of cyclic vapours.[2][3] This was a breakthrough in distillation Distillation is a method of separating mixtures based on differences in their volatilities in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction technology and he made use of it in his steam distillation Steam distillation is a special type of distillation for temperature sensitive materials like natural aromatic compounds process, which requires refrigerated tubing, to produce essential oils An essential oil is a concentrated, hydrophobic liquid containing volatile aroma compounds from plants. Essential oils are also known as volatile, ethereal oils or aetherolea, or simply as the "oil of" the plant from which they were extracted, such as oil of clove. An oil is "essential" in the sense that it carries a.[4]

The first known artificial refrigeration was demonstrated by William Cullen Cullen was born in Hamilton, Lanarkshire. His father William was a lawyer retained by the Duke of Hamilton and his mother was Elizabeth Roberton of Whistlebury. He studied at Hamilton Grammar School, then, in 1726, began a General Studies arts course at the University of Glasgow. He began his medical training as apprentice to John Paisley, a at the 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 world in 1748. Between 1805, when 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 the first refrigeration machine that used vapor instead of liquid, and 1902 when Willis Haviland Carrier Willis Haviland Carrier was an engineer and inventor, and is known as the man who invented modern air conditioning demonstrated the first air conditioner An air conditioner is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The cooling is done using a simple refrigeration cycle. In construction, a complete system of heating, ventilation, and air conditioning is referred to as "HVAC". Its purpose, in a building or an automobile, is to provide, scores of inventors contributed many small advances in cooling machinery. In-home refrigeration became a reality in 1834 with the invention of the cooling compression system by the American inventor Jacob Perkins.[5] In 1850 or 1851, Dr. 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. He received his medical education at the College of Physicians and Surgeons of the Western District of demonstrated an ice maker.[citation needed]

In 1857, Australian James Harrison James Harrison was an Australian newspaper printer, journalist, politician, and pioneer in the field of mechanical refrigeration developed the world first practical ice making machine and refrigeration system, and it was used in the brewing and meat packing industries of Geelong Geelong is a port city located on Corio Bay and the Barwon River, 75 kilometres (47 mi) in the state of Victoria, Australia south-west of capital Melbourne. Geelong is the second most populated city and the fifth most populated non-capital city in Australia. The estimated urban population is 160,991 people,. The City of Greater Geelong, Victoria. Ferdinand Carré Ferdinand Carré was a French engineer, born at Moislains, in the Somme department in 1824. He died in 1894 of France developed a somewhat more complex system in 1859. Unlike earlier compression-compression machines, which used air as a coolant, Carré's equipment contained rapidly expanding ammonia. The absorption refrigerator The absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling system. Absorption refrigerators are a popular alternative to regular compressor refrigerators where electricity is unreliable, costly, or unavailable, where noise from the compressor is problematic, or where surplus heat is was invented by Baltzar von Platen and Carl Munters Carl Georg Munters , born 22 March 1897 in Dala-Järna, Kopparbergs län, Sweden, died in 1989. Swedish inventor, most known for inventing the gas absorption refrigerator together with Baltzar von Platen now sold by Electrolux in 1922, while they were still students at the Royal Institute of Technology The Royal Institute of Technology is an university in Stockholm, Sweden. KTH was founded in 1827 as Sweden's first polytechnic and is with TKK in Espoo, depending on definition, Scandinavia's largest institution of higher education in technology and one of the leading technical universities in Europe in Stockholm Stockholm (Swedish pronunciation: [ˈstɔkːɔlm] ) is the capital and the largest city of Sweden. It is the site of the national Swedish government, the Riksdag (parliament), and the official residence of the Swedish monarch as well as the prime minister. Since 1980, the monarch has resided at Drottningholm Palace outside of Stockholm and uses. It became a worldwide success and was commercialized by Electrolux The Electrolux Group is a Swedish manufacturer of home and professional appliances and is the world's 2nd largest appliance manufacturer. According to the company, it sells more than 40 million products to customers in 150 countries annually, which translates to 2 products every second, every day of the year. Electrolux products include. Other pioneers included Charles Tellier Charles Tellier was a French engineer, born in Paris. He early made a study of motors and compressed air. In 1868 he began experiments in refrigeration, which resulted ultimately in the refrigerating plant as used on ocean vessels, to preserve meats and other perishable food. In 1911 Tellier was awarded the Joest prize by the French Institute and, David Boyle, and Raoul Pictet Raoul-Pierre Pictet was a Swiss physicist and the first person to liquefy nitrogen. He was born in Geneva and served as professor in the university of that city. He devoted himself largely to problems involving the production of low temperatures and the liquefaction and solidification of gases. Carl von Linde Professor Doctor Carl Paul Gottfried von Linde was a German engineer who developed refrigeration and gas separation technologies. Linde was a member of scientific and engineering associations, including being on the board of trustees of the Physikalisch-Technische Bundesanstalt German National Metrology Institute and the Bavarian Academy of 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 was a 1922 model that consisted of a wooden cold box, water-cooled Water cooling is a method of heat removal from components. As opposed to air cooling, water is used as the heat transmitter. Water cooling is commonly used for cooling internal combustion engines in automobiles and large electrical generators. Other uses include cooling the barrels of machine guns, cooling of lubricant oil in pumps; for cooling compressor, an ice cube Ice cubes are small, roughly cube-shaped pieces of ice, conventionally used to cool beverages. Ice cubes are often preferred over crushed ice because they melt more slowly; they are standard in mixed drinks that call for ice, in which case the drink is said to be "on the rocks." tray and a 9 cubic feet The cubic foot is an and US customary (non-metric) unit of volume, used in the United States and the United Kingdom. It is defined as the volume of a cube with sides of one foot (0.3048 m) in length compartment, and cost $714. (A 1922 Model-T The Ford Model T is an automobile that was produced by Henry Ford's Ford Motor Company from 1908 through 1927. The Model T set 1908 as the historic year that the automobile became popular. It is generally regarded as the first affordable automobile, the car that opened travel to the common middle-class American; some of this was because of Ford's Ford cost about $450.) 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 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 because of its resemblance to the gun turret on the ironclad warship USS Monitor USS Monitor was an ironclad warship commissioned by the United States Navy in 1861. Completed in 1862, she was the first ironclad built for the U.S. Navy.[citation needed] She is most famous for her participation in the first-ever naval battle between two ironclad warships, the Battle of Hampton Roads on 9 March 1862, in which Monitor fought the of the 1860s. The compressor assembly, which emitted a great deal of heat, was placed above the cabinet, and surrounded with a decorative ring. Over 1,000,000 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 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, which is highly flammable, harmful to the eyes, and toxic if inhaled or ingested. Many of these units are still functional today. These cooling systems cannot legally be recharged with the hazardous original refrigerants if they leak or break down.

Older U.S. refrigerator model, with freezer compartment

The introduction of Freon A chlorofluorocarbon is an organic compound that contains carbon, chlorine, and fluorine, produced as a volatile derivative of methane and ethane. A common subclass is the hydrochlorofluorocarbons (HCFCs), which contain hydrogen, as well. They are also commonly known by the DuPont trade name Freon. The most common representative is in the 1920s expanded 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 popular term at the time for the unit was a "deep freeze". These devices, or "appliances", did not go into mass production for use in the home until after World War II Albania · Australia · Austria · Azerbaijan · Belarus · Belgium · Brazil · Bulgaria · Burma · Cambodia · Canada · Ceylon (Sri Lanka) · Channel Islands · China · Czechoslovakia · Denmark · Dutch East Indies · Egypt · Estonia · Finland · France · Germany · Gibraltar · Greece · Greenland · Hong Kong · Hungary · Iceland ·. The 1950s and 1960s saw technical advances like automatic defrosting Defrosting is a procedure, performed periodically on refrigerators and freezers to maintain their operating efficiency. Over time, as the door is opened and closed, letting in new air, water vapour from the air condenses on the cooling elements within the cabinet. It also refers to leaving frozen food at a higher temperature prior to cooking and automatic ice making. More efficient refrigerators were developed in the 1970s and 1980s, even though environmental issues Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total volume of ozone in Earth's stratosphere since the late 1970s, and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period. The latter phenomenon is commonly 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 Post Foods, LLC, also known as Post Cereals was founded by C.W. Post. It began in 1895 with the first Postum, a "cereal beverage", developed by Post in Battle Creek, Michigan. The first cereal, Grape-Nuts, was developed in 1897. Post has its headquarters in the Bank of America Plaza in Downtown St. Louis, Missouri (the forerunner of General Foods General Foods Corporation was a company whose direct predecessor was established in the USA by Charles William Post as the Postum Cereal Company in 1895. The name General Foods was adopted in 1929, after several corporate acquisitions. In November, 1985 General Foods was acquired by Philip Morris Companies for $5.6 billion, the largest non-oil), which had acquired the technology when it bought the rights to Clarence Birdseye Clarence Frank Birdseye II was an American inventor who is considered the founder of the modern frozen food industry's successful fresh freezing methods.

The first successful application of frozen foods occurred when General Foods heiress Marjorie Merriweather Post (then wife of Joseph E. Davies, United States Ambassador to the Soviet Union) deployed commercial-grade freezers in Spaso House, the U.S. Embassy in Moscow, in advance of the Davies’ arrival. Post, fearful of the USSR's food processing safety standards, fully stocked the freezers with products from General Foods' Birdseye unit. The frozen food stores allowed the Davies to entertain lavishly and serve fresh frozen foods that would otherwise be out of season. Upon returning from Moscow, Post (who resumed her maiden name after divorcing Davies) directed General Foods to market frozen product to upscale restaurants.

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 a luxury item, began to be commonplace.

General technical explanation

Main article: Refrigeration Vapor Compression Cycle: 1) Condenser, 2) Expansion valve, 3) Evaporator unit, 4) Compressor

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 above the temperature of the refrigerator interior. The vapor is compressed and exits the compressor as high-pressure superheated vapor. The superheated vapor travels under pressure through coils or tubes comprising "the condenser", which 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 is forced through a metering or throttling device, also known as an expansion valve (essentially a constriction) 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, 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 refrigerator or freezer 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 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.

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 the compressor motor in a typical refrigerator. A fan or pump might be the only mechanical moving parts; reliance on convection is considered impractical.

The Peltier effect uses electricity to pump heat directly; this type of refrigerator is sometimes used for camping, or where noise is not acceptable. They can be totally silent (if they don't include a fan for air circulation) but are less energy-efficient than other methods.

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.

Other alternatives to the vapor-compression cycle but not in current use include thermionic, vortex tube, air cycle, magnetic cooling, Stirling cycle, Malone refrigeration, acoustic cooling, pulse tube and water cycle systems.[6]

Features

The inside of a common U.S. home refrigerator

Newer refrigerators may include:

Early freezer units accumulated ice crystals around the freezing units. This was a result of humidity introduced into the units when the doors to the freezer were opened. This frost buildup required periodic thawing ("defrosting") of the units to maintain their efficiency. Manual Defrost (referred to as Cyclic) units are still available. Advances in automatic defrosting eliminating the thawing task were introduced in the 1950s, but are not universal, due to energy performance and cost. These units utilized a counter, that only defrosted the freezer compartment (Freezer Chest) when a specific number of door openings had been made. The units were just a small timer combined with an electrical heater wire which heater the Freezer's walls for a short amount of time to remove all traces of frost/frosting. Also, early units featured freezer compartments located within the larger refrigerator, and accessed by opening the refrigerator door, and then the smaller internal freezer door; units featuring an entirely separate freezer compartment were introduced in the early 1960s, becoming the industry standard by the middle of that decade. These older freezer compartments were the main cooling body of the refrigerator, and only maintained a temperature of around -6°C, which is suitable for keeping food for a week.

Later advances included automatic ice units and self compartmentalized freezing units.

An increasingly important environmental concern is the disposal of old refrigerators - initially because of the freon coolant damaging the ozone layer, but as the older generation of refrigerators disappears it is the destruction of CFC-bearing insulation which causes concern. Modern refrigerators usually use a refrigerant called HFC-134a (1,1,1,2-Tetrafluoroethane), which does not deplete the ozone layer, instead of freon.

Disposal of discarded refrigerators is regulated, often mandating the removal of doors: children playing hide-and-seek have been asphyxiated while hiding inside discarded refrigerators, particularly older models with latching doors. More modern units use a magnetic door gasket which holds the door sealed but can be pushed open from the inside. This gasket was invented by Herman C. Ells Sr. But children can still come to harm if they hide in a discarded refrigerator.[7]

Types of domestic refrigerators

Household refrigerator output in 2000

Domestic refrigerators and freezers for food storage are made in a range of sizes. Among the smallest is a 4 L Peltier fridge advertised as being able to hold 6 cans of beer. A large domestic fridge stands as tall as a person and may be about 1 m wide with a capacity of 600 L. Some models for small households fit under kitchen work surfaces, usually about 86 cm high. Fridges may be combined with freezers, either stacked with fridge or freezer above, below, or side by side. A fridge without 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).

Fridges and freezers may be free-standing, or built into a kitchen.

Energy efficiency

An auto-defrost unit uses a blower fan to keep moisture out of the unit. It also has a heating coil beneath the evaporator that periodically heats the freezer compartment and melts any ice buildup. Some units also have heaters in the side of the door to keep the unit from "weeping." Manual defrost units are available in used-appliance shops or by special order.

Refrigerators used to consume more energy than any other home appliance, but in the last twenty years great strides have been made to make refrigerators more energy efficient. In the early 1990s a competition was held among the major manufacturers to encourage energy efficiency. Current models that are Energy Star qualified use 50 percent less energy than models made before 1993.[11] The most energy-efficient unit made in the US is designed to run on 120 or 110 volts, and consumes about half a kilowatt-hour per day.[12] But even ordinary units are quite efficient; some smaller units use less than 0.5 kilowatt-hour per day. Larger units, especially those with large freezers and icemakers, may use as much as 4 kWh per day. Although, some older units can be made more efficient with modifications; such as New Door Seals, cleaning the condenser coils at rear and adjusting and/or replacing the thermostat to make temperatures more accurate.

Among the different styles of refrigerators, top-freezer models are more efficient than bottom-freezer models of the same capacity, which are in turn more efficient than side-freezer models. Models with through-the-door ice units are less efficient than those without.[13] Dr. Tom Chalko in Australia has developed an external thermostat to convert any chest freezer into a chest fridge using only about 0.1kWh per day—the amount of energy used by a 100 watt light bulb in one hour.[14] A similar device is manufactured by Johnson Controls.[15] Scientists at Oxford University have reconstructed a refrigerator invented in 1930 by Leó Szilárd and Albert Einstein in their efforts to replace current technologies with energy efficient green technology. The Einstein refrigerator operates without electricity and uses no moving parts or greenhouse gases.[16]

Impact on lifestyle

The refrigerator allows the modern family to keep food fresh for much longer than before. This, along with the modern supermarket, allows most families, without a sizeable garden in which to grow vegetables and raise animals, a vastly more varied diet and improved health resulting from improved nutrition.[citation needed] Dairy products, meats, fish, poultry and vegetables can be kept refrigerated in the same space within the kitchen (although raw meat should be kept separate from other foodstuffs for reasons of hygiene).

The refrigerator lets people eat more salads, fresh fruits and vegetables, without having to own a garden or an orchard. Exotic foodstuffs from far-off countries that have been imported by means of refrigeration can be enjoyed in the home because of domestic refrigeration.

Freezers allow households to buy food in bulk: it can be eaten at leisure, and bulk purchase saves money (see economies of scale). Ice cream, a popular commodity of the 20th century, could previously only be obtained by traveling long distances to where the product was made fresh, and had to be eaten on the spot. Now it is a common food item. Ice on demand not only adds to the enjoyment of cold drinks, but is useful for first-aid, and for cold packs that can be kept frozen for picnics or in case of emergency.

Temperature zones and ratings

Commercial for electric refrigerators in Pittsburgh, Pennsylvania, 1926

Some refrigerators are now divided into four zones to store different types of food:

The capacity of a refrigerator is measured in either litres or cubic feet. Typically the volume of a combined fridge-freezer is split to 100 litres (3.53 cubic feet) for the freezer and 140 litres (4.94 cubic feet) for the refrigerator, although these values are highly variable.

Temperature settings for refrigerator and freezer compartments are often given arbitrary numbers by manufacturers (for example, 1 through 9, warmest to coldest), but generally 1.7 to 3.3 °C (35 to 38 °F) is ideal for the refrigerator compartment and −18 °C (−0.4 °F) for the freezer. Some refrigerators are required to be within certain external temperature parameters to run properly. This can be an issue when placing units in an unfinished area such as a garage.

European freezers, and refrigerators with a freezer compartment, have a four star rating system to grade freezers.

Although both the three and four star ratings specify the same minimum temperature of -18°C, only a four star freezer is intended to be used for freezing fresh food. Three (or fewer) stars are used for frozen food compartments which are only suitable for storing frozen food; introducing fresh food into such a compartment is likely to result in unacceptable temperature rises. Most European Refrigerators include a Moist Cold Fridge section (which does require defrosting at irregular intervals) and a Frost Free Freezer section, to keep frozen food frost free.

Non-food use

Refrigerators have many other uses. Examples include laboratories, for storing samples awaiting analysis, and morgues, for storing corpses.

Recycling

Old refrigerators have been adapted to create low cost passive solar water heating systems.[17]

See also

Notes and references

  1. ^ Jstor.org: Household appliances and the use of time: the United States and Britain since the 1920s
  2. ^ Pitman, Vicki (2004). Aromatherapy: A Practical Approach. Nelson Thornes. p. xi. ISBN 0748773460.
  3. ^ Myers, Richard (2003). The Basics of Chemistry. Greenwood Publishing Group. p. 14. ISBN 0313316643.
  4. ^ Marlene Ericksen (2000), Healing with Aromatherapy, p. 9, McGraw-Hill, ISBN 0658003828
  5. ^ Who Invented the Refrigerator
  6. ^ IIFIIR.org
  7. ^ Adams, Cecil (2005). "Is it impossible to open a refrigerator door from the inside?". http://www.straightdope.com/columns/050304.html. Retrieved 2006-08-31.
  8. ^ Thermal mass refrigerators
  9. ^ Solar refrigerators for developing world
  10. ^ Magnetic refrigerators
  11. ^ "Refrigerators & Freezers". Energy Star. http://www.energystar.gov/index.cfm?c=refrig.pr_refrigerators.
  12. ^ Humboldt.edu
  13. ^ "What's more energy efficient, a refrigerator with a top-mounted freezers, bottom-mounted freezer, or a side-by-side?". Energy Star. http://energystar.custhelp.com/cgi-bin/energystar.cfg/php/enduser/std_adp.php?p_faqid=4912.
  14. ^ MTbest.net "A fridge that takes only 0.1 kWh a day?". http://mtbest.net/chest_fridge.pdf MTbest.net.
  15. ^ Kegman.net
  16. ^ "Albert Einstein Refrigerator"
  17. ^ "More ways to recycle old refrigerators into low cost solar water heaters". Mother Earth News. 1978 January. http://www.motherearthnews.com/Do-It-Yourself/1978-01-01/More-Ways-to-Recycle-Old-Refrigerators-into-Low-Cost-Solar-Water-Heaters.aspx. Retrieved 2009-10-13.

External links

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Look up refrigerator or freezer in Wiktionary, the free dictionary.

Categories: Home appliances | Heat pumps | Food storage | Cooling technology | Food preservation | English inventions | 1915 introductions

 

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'Freezer' Answers
How to fix a clogged freezer drain in a refrigerator?
Q. Water is pooling under the floor of the freezer on top of the fresh food compartment. There are no visible drains to access on the inside of the freezer or refrigerator compartments. The brand name is Amana and it is a top to bottom unit.
Asked by mo miller - Thu Mar 18 22:36:54 2010 - - 3 Answers - 0 Comments

A. you have to take apart the freezer floor and get a hair dryer on the ice clogging up the drain hole
Answered by dvdacmn - Fri Mar 19 07:00:49 2010

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Sun Jul 25 08:44:22 2010
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