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refrigerator

  (rĭ-frĭj'ə-rā'tər) pronunciation
n.

An appliance, cabinet, or room for storing food or other substances at a low temperature.


 
 
How Products are Made: How is a refrigerator made?

Background

Prior to the development of artificial refrigeration techniques during the 1800s, people utilized a variety of means to chill and preserve foodstuffs. For centuries, ice served as the principal refrigerant. Ironically, the ancient Indians and Egyptians pioneered an ice-making technique that served as the conceptual basis for the first "modern" refrigerators developed during the nineteenth century: evaporation. The relatively quick evaporation of a liquid creates an expanding volume of gas. As water vapor rises, its kinetic energy increases dramatically, in part because the warm vapor is drawing in energy from its surroundings, which are cooled by this process. The Indians and Egyptians took advantage of this phenomenon by placing wide, shallow bowls filled with water outside during the cool nights. As some water quickly evaporated, the remaining water cooled, forming ice. With this method, it was possible to create sizeable chunks of ice that could then be used to cool food.

Using a more primitive means of procuring ice, the ancient Chinese simply transported it from the mountains to cool their food; later, the Greeks and Romans adopted this practice. To preserve the ice itself, people stored it in pits or caves insulated with straw and wood, by which means they could maintain a supply of ice for months. In industrialized nations, ice served as the primary method of chilling food through the nineteenth century, when people inserted blocks of ice in insulated cabinets alongside the food they wished to store. Even today, in many developing nations ice remains the sole available refrigerant.

The first known attempt to develop an artificial refrigerator took place in Scotland at the University of Glasgow. There, in 1748, William Cullen revived the ancient Indian-Egyptian practice of freezing liquid by means of evaporation, although he accelerated the process by boiling ethyl ether into a partial vacuum (ethyl evaporates more quickly than water). Cullen attempted this merely as an experiment, as did American Oliver Evans, who designed another refrigerator in 1805. Evans's machine, based on a closed cycle of compressed ether, represented the first effort to use simple vapor instead of vaporizing a liquid. While Evans never developed his machine beyond the prototype stage, in 1844 an American doctor named John Gorrie actually built a very similar machine to provide ice for the hospital in which he worked. Gorrie's machine compressed air that was next cooled with water. The cooled air was then routed into an engine cylinder, and, as it re-expanded, its temperature dropped enough so that ice could be made.

In 1856 another American, Alexander Twinning, began selling a refrigeration machine based on the same vapor-compression principle, and soon after that Australian James Harrison enlarged the American design (meant to be used in individual homes) for the meat-packing and beer-making industries. Three years later, Ferdinand Carre refined the basic concept underlying all of these refrigerators when he introduced ammonia as a coolant. Ammonia represented an advance because it expands more rapidly than water and can thus absorb more heat from its environs. Carre also contributed other innovations. His refrigerator operated by means of a cycle in which a refrigerant vapor (ammonia) was absorbed in a liquid (a mixture of ammonia and water) that was subsequently heated. The heat caused the refrigerant to vaporize, thereby creating a cooling effect (after it vaporized, the refrigerant was condensed so that it could once again be absorbed in the liquid, repeating the cycle). Carre's machine not only sold extremely well, it also inaugurated modern refrigeration by upgrading Evans's compression concept and adding a more sophisticated refrigerant. These components remain the basis of most refrigerators used today.

Ammonia itself posed several problems, however. While it served as a very effective coolant, it was both odiferous and poisonous when it leaked, and it quickly disappeared from refrigeration after synthetic alternatives were developed during the 1920s. The best known of these, patented by Du Pont under the name freon, was created by chemically altering the methane molecule, substituting two chlorine and two fluorine atoms for its four hydrogen atoms. The resulting gas (technically, dichlorofluoromethane) was hailed because its low boiling point, surface tension, and viscosity rendered it an ideal—and ostensibly problem-free—refrigerant. Later, in the 1970s, scientists realized that freon posed problems of its own related to the environment (see "Environmental Concerns" section below) and began searching for new agents to use in refrigeration.

Raw Materials

Refrigerators today consist of several basic components: the exterior cabinet and door, the inner cabinet or liner, the insulation inserted between the two, the cooling system, the refrigerant, and the fixtures. The cabinet and door are made of aluminum or steel sheet metal that is sometimes prepainted. The metal is generally purchased in a coil that is either fed directly into the manufacturing process or cut to size and fed sheet by sheet. The inner cabinet is made of sheet metal, like the outer cabinet, or of plastic. The insulation that fills the gap between the inner and outer cabinets consists of fiberglass or polyfoam. The components of the cooling system (compressor, condenser, coils, fins) are made of aluminum, copper, or an alloy. The tubing is usually copper, because of that metal's ductility—its ability to bend without breaking. Freon remains the most commonly used refrigerant, and almost all of the large interior fixtures (door and cabinet liners) are made from vacuum-formed plastic; smaller fixtures (butter compartments, egg trays, salad crispers) are purchased as small plastic blanks or in pre-formed pieces.

Design

The contemporary refrigerator is based on two basic laws of physics: one, that heat flows from warmer material to cooler materials and never the reverse; two, that decreasing the pressure of a gas also decreases its temperature. Although refinements have been made since Carre introduced his model during the late nineteenth century, these basic principles are still visible in today's refrigerators.

Refrigerators work by removing the warmth from the air within their interior compartments and relaying that heat to the air outside. The coolant (freon) accomplishes this transfer as it passes through a circuit, moving from the evaporator to the condenser. Beginning in the evaporator, which lies inside an insulated cabinet, the freon is heated. Because it has been made to boil, the freon draws heat from the air within the refrigerator. Having absorbed this heat, the freon is then routed to the condenser. In this set of copper coils (usually mounted at the back or on the bottom of the refrigerator), the freon condenses—returns to a liquid state—transferring its heat into the outside air as it does so. After cooling, the freon then returns to the evaporator, where it is once again heated and begins to absorb heat from the food stored within the refrigerator. Sometimes, to increase their surface area (and thus facilitate thermal transfer), the evaporator and the condenser are fitted with metal fins.

For defrosting, a coil is wrapped around the freezer unit. When the timer reaches defrost, the refrigerant is passed through this coil while it is hot to raise the temperature and melt the ice. The coil is generally positioned away from any ice makers to prevent the ice cubes from melting and freezing together.

The Manufacturing
Process

Outer cabinet and door

  • Pieces of sheet metal are either welded or clinched together. Clinching is a process closely resembling stapling in that the two pieces are crimped together under pressure, though no additional pieces such as staples are added. If the part of the cabinet is to be visible, it will be welded and ground down to appear as one piece. The extent to which the welding process is automated depends on the company and the number of refrigerators being produced.
  • If the sheet metal was not purchased in precoated form, it is now painted. Some manufacturers use spray equipment to lay a uniform coat of paint on the metal. Others dip the parts in a paint/solvent mixture before heating them to bake the paint onto the surface.

Inner cabinet

  • The inner cabinet is sometimes made from sheet metal very similar to the outer shell. Any seams are caulked to improve insulation and looks. Some manufacturers and some models use plastic for inner liners; for example, the inner door is almost exclusively made from plastic today. The plastic liners are vacuum formed. In this process, a thick piece of plastic slightly larger than the finished part has its outer edges clamped and is then heated. The hot plastic is next pulled by vacuum into a mold and cooled. After trimming, the resulting part is ready for assembly.
  • The inner cabinet is inserted into the outer cabinet, and the two are snapped together before the fixtures are inserted. Some tubes and wires are run through the gap between the two before it is filled with insulation. A dispensing device (sometimes robotically operated, sometimes a manually operated long 'gun') inserts foam between the walls. When heated in an oven, this foam expands to add rigidity and insulation to the cabinet. A similar process is used for the doors.

Cooling system

  • The refrigeration components are attached to the cabinet using screws and clips. The tubing is soldered together, and a protective coating is sprayed on the joints. The order of this assembly varies between manufacturers and models. The copper tubing from which the coils (condensers and evaporators) have separately been cut, bent, and soldered is then attached to the refrigerator as a unit.
  • The seal on the refrigerator door is created by means of magnet laden gaskets that are attached to the doors with screws. Handles and hinges are also screwed onto the door before its hinges are screwed onto the cabinet. Some adjustment is allowed for proper operation of the door.

Testing and adding accessories

  • Most manufacturers mix testing with manufacturing from this point on. The unit is leak tested with nitrogen (a safe gas that makes up about 79 percent of the air); if it passes, it is charged with refrigerant and subjected to further testing. Next, the accessories (shelves, crispers, ice trays, etc.) are added and taped down for shipping. The unit is given a final look and then packaged for shipping.

Quality Control

As mentioned above, all subassemblies of tubing that will contain refrigerant are pressure-tested with nitrogen, which will reveal any flaws in the tubing and in the soldering that joins it. The entire unit is also leak-tested prior to charging with freon. Once charged, the unit is tested as a whole to ensure that it is capable of reaching design temperatures including those necessary during the defrost cycle. The unit is operated with sensors inside that determine the temperature changes over time. Sometimes the refrigerant pressures are also measured. The unit is then subjected to a final 'sniff test by a machine that detects refrigerant to ensure that no leaks have developed during testing.

By products/Waste

Metal components that are rejected are sold to metal recycling companies. Plastic components are ground into small pieces and either reused as raw material or returned to the vendor for reuse. If a unit is rejected after it has been charged, the refrigerant is drained by special equipment and reused.

Environmental Concerns

In the mid-1970s, scientists began to understand that as gases in the chlorofluorocarbon (CFC) group, which includes freon, waft upward into the stratosphere (the upper layer of the atmosphere), they gradually decompose, releasing chlorine atoms as they do so. The problem with this is that each chlorine atom can destroy tens of thousand of ozone molecules, ozone being the triatomic form of oxygen that comprises a protective layer in the stratosphere, absorbing much solar ultraviolet radiation that would harm animal life if it reached the earth's surface. As researchers realized that CFC emissions were exacerbating the hole in the ozone layer over the Antarctic continent, public pressure to limit emissions mounted. In 1987, representatives from nations around the globe signed an agreement, the Montreal Protocol on Substances that Deplete the Ozone Layer, in which they agreed to phase out production of the chemicals known to deplete the ozone layer, including freon. Unfortunately, chlorofluorocarbons are also present in the polystyrene foam that some manufacturers use as an insulator between the external case and the interior lining of their refrigerators. So, efforts to reduce the CFC emissions from refrigerators are presently continuing on two fronts, as manufacturers attempt to find alternatives to both the coolant freon and the insulator polystyrene.

The Future

In terms of freon, several intermediate steps have been taken to minimize CFC emission as researchers attempt to identify safe coolant alternatives. Refrigerator designs have been improved to reduce the amount of freon needed; leak detection systems have been installed; maintenance has been limited to trained, authorized personnel; and refrigerant is recovered and recycled whenever possible. Moreover, long-term replacements for freon are being explored. Thus far, the most promising among them is HCFC-22, which, although still a chlorofluorocarbon, contains an additional hydrogen atom that reduces the molecule's ozone-depletion capacity by 95 percent. While its cost (three to five times greater than that of freon) is problematic, HCFC-22 is presently undergoing tests to determine its toxicity.

CFC-containing insulation may be replaced by the same kind of vacuum insulation that is used in thermos bottles. Research indicates that vacuum insulation is more efficient in terms of both space and energy, so, at present, it appears that insulation alternatives will become viable well before freon substitutes.

Where To Learn More

Books

Boast, Michael F. Newnes Refrigeration Pocket Book. Butterworth-Heinemann, 1991.

Cerepnalkovski, I. Modern Refrigerating Machines. Elsevier Science Publishing, 1991.

Dellino, Clive V. Cold and Chilled Storage Technology. Van Nostrand Reinhold, 1989.

Marsh, R. Warren and Olive C. Throats. Principles of Refrigeration. Delmar Publishers Inc., 1979.

Stoecker, W. F. and J. W. Jones. Refrigeration & Air Conditioning. McGraw-Hill, 1982.

Periodicals

"Refrigeration's Revitalization." Appliance, February 1993, pp. 54-58.

"Refrigerator Doors Have a 'Clear' Edge." Design News. January 7, 1991, p. 33.

"A $30-million Super-Efficient Refrigerator." Electrical World. July, 1992, p. 30.

Marbach, William D. "Now, An Icebox That's Cool for the Environment." Business Week. July 22, 1991, p. 65.

Murray, Charles J. "Plastic Welding Technique Aids Refrigerator Assembly: Special Parts Replace Metal Anchors on Refrigerator Liners." Design News. February 15, 1988, p. 230.

[Article by: Barry M. Marton]


 
Sci-Tech Encyclopedia: Refrigerator

An insulated, cooled compartment. If it is large enough for the entry of a person, it is termed a walk-in box; otherwise it is called a reach-in refrigerator. Cooling may be by mechanical or gas refrigeration, by water or dry ice, or by brine circulation. Temperatures maintained depend upon the requirements of the product stored, generally varying from 55°F (13°C) down to 0°F (−18°C), and sometimes lower.

A household or domestic refrigerator is a factory-built, self-contained cabinet. The range of storage capacities is wide and varies among manufacturers. Modem designs have a main compartment for holding food above freezing, a second compartment for storage below freezing, and trays for the freezing of ice cubes. Low-temperature household refrigerators, or home freezers, for the storage of frozen foods are manufactured in both the chest and the upright, or vertical, types.

A commercial refrigerator is any factory-built refrigerated fixture, cabinet, or room that can be assembled and disassembled readily. Commercial or built-in refrigerators are used in restaurants, markets, hospitals, hotels, and schools for the storage of food and other perishables. See also Refrigeration.

 
Architecture: refrigerator

A container and a means of cooling it, such as a commercial refrigerator, service refrigerator, etc.

 
Word Tutor: refrigerator
pronunciation

IN BRIEF: A box or room in which the air is kept cool to keep food, etc. from spoiling.

pronunciation Leftovers in their less visible form are called memories. Stored in the refrigerator of the mind and the cupboard of the heart. — Robert Fulghum

 
Wikipedia: refrigerator
"Fridge" redirects here. For the band, see Fridge (band). For other uses, see Fridge (disambiguation).
"Freezer" redirects here. For the machine used to make ice cream, see Ice cream freezer.
A typical refrigerator with its door open
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A typical refrigerator with its door open

A refrigerator (often called a "fridge" for short) is a cooling appliance comprising a thermally insulated compartment and a mechanism to transfer heat from it to the external environment, cooling the contents to a temperature below ambient. Refrigerators are extensively used to store foods which deteriorate at ambient temperatures; spoilage from bacterial growth and other processes is much slower at low temperatures. Devices described as "refrigerators" maintain a temperature a few degrees above the freezing point of water; similar devices which maintain temperatures below the freezing point of water are called "freezers". The refrigerator is a relatively modern invention amongst kitchen appliances. It replaced the common icebox which had been placed outside for almost a century and a half prior, and is sometimes still called by the original name "icebox".

Freezers keep their contents, usually foods, frozen. They are used both in households and for commercial use. Most freezers operate at around -18 °C (0 °F). Domestic freezers can be included as a compartment in a refrigerator, sharing the same mechanism or with a separate mechanism, or can be standalone units. Domestic freezers are generally upright units, resembling refrigerators, or chests, resembling upright units laid on their backs. Many modern freezers come with an icemaker.

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 ammonia gas systems, making them unsafe for home use. Practical household refrigerators were introduced in the 1915 and gained wider acceptance in the United States in the 1930s as prices fell and non-toxic, non-flammable synthetic refrigerants such as Freon or R-12 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 of the refrigerator

See also: Timeline of low-temperature technology

Before the invention of the refrigerator, icehouses were used to provide cool storage for most of the year. These structures were mainly built and used in ancient Persia (Iran). Placed near freshwater lakes or packed with snow and ice during the winter, they were once very common. Using the environment to cool foodstuffs is still common today. On mountainsides run off from melting snow higher up is a convenient way to cool drinks, and during the winter months simply placing one's milk outside one's window is sufficient to greatly extend its useful life.

The first known artificial refrigeration was demonstrated by William Cullen at the University of Glasgow in 1748, and relied on the vapor-compression refrigeration process explained by Michael Faraday. Between 1805, when Oliver Evans designed the first refrigeration machine that used vapor instead of liquid, and 1902 when Willis Haviland Carrier demonstrated the first air conditioner, scores of inventors contributed many small advances in cooling machinery. In 1850 or 1851, Dr. John Gorrie demonstrated an ice maker. In 1857, Australian James Harrison introduced vapor-compression refrigeration to the brewing and meat packing industries. The absorption refrigerator was invented by Baltzar von Platen and Carl Munters in 1922, while they were still students at the Royal Institute of Technology in Stockholm, Sweden. It became a worldwide success and was commercialized by Electrolux. Other pioneers included Charles Tellier, David Boyle, and Raoul Pictet.

At the start of the 20th Century, about half of households in the United States relied on melting ice (and an icebox) to keep food cold, while the remaining half had no cooled storage at all. The ice used for household storage was expensive because ice had to be cut from winter ponds (or mechanically produced), stored centrally until needed, and delivered regularly.

In a few exceptional cases, mechanical refrigeration systems had been adapted by the start of the 20th century for use in the homes of the very wealthy, and might be used for cooling both living and food storage areas. One early system was installed at the mansion of Walter Pierce, an oil company executive.[1]

Marcel Audiffren of France championed the idea of a refrigerating machine for cooling and preserving foods at home. His U.S. patents, issued in 1895 and 1908, were purchased by the American Audiffren Refrigerating Machine Company. Machines based on Audiffren's sulfur dioxide process were manufactured by General Electric in Fort Wayne, Indiana and marketed by the Johns-Manville company. The first unit was sold in 1911. Audiffren machines were expensive, selling for about $1,000 — about twice as much as an automobile cost at the time.

General Electric sought to develop refrigerators of its own, and in 1915 the first Guardian unit was assembled in a back yard wash house as a predecessor to the Frigidaire. In 1916 Kelvinator and Servel came out with two units among a field of competing models. This number increased to 200 by 1920. In 1918, Kelvinator had a model with automatic controls.

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 compressor, an ice cube tray and a 9 cubic foot compartment for $714. (A 1922 Model-T 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 a function of the modern refrigerator.

A Monitor-style (General Electric format) refrigerator, more like an icebox with its refrigerating mechanisms on top.
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A Monitor-style (General Electric format) refrigerator, more like an icebox with its refrigerating mechanisms on top.

The first refrigerator to see widespread use was the General Electric "Monitor-Top" refrigerator introduced in 1927. The compressor assembly, which emitted a substantial amount of heat, was placed above the cabinet, and surrounded with a decorative ring. Over 1,000,000 units were produced. This refrigerator used sulfur dioxide refrigerant. Many units are still functional today.

The introduction of freon expanded the refrigerator market during the 1930s, and freezer units became a little more common and requested during the 1940s. Home units did not go into mass production until after WWII. The 1950s and 60s saw technical advances like automatic defrosting and automatic ice making. Developments of the 1970s and 80s brought about more efficient refrigerators, and environmental issues banned the use of CFC (freon) refrigerants used in sealed systems.

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. Current models that are Energy Star qualified use 50 percent less energy than models made before 1993. [2]

Early refrigerator models (1916 and on) featured a cold compartment for ice cube trays. Successful processing of fresh vegetables through freezing began in the late 1920s 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 first successful example of the benefits 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 to Spasso House (US Embassy) in Moscow in advance of the Davies’ arrival. Post, fearful of the food processing safety observed in the USSR, then fully stocked the freezers with product processed from General Foods Birdseye unit. The frozen food stores allowed the Davies’ to lavishly entertain 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.

Introduction of home freezer units occurred in the United States in 1940, and frozen foods began to make the transition from luxury to necessity.

How a refrigerator works

Main article: refrigeration

Refrigerators work by the use of heat pumps operating in a refrigeration cycle. An industrial refrigerator is simply a refrigerator used in an industrial setting, usually in a restaurant or supermarket. They may consist of either a cooling compartment only (a larger refrigerator) or a freezing compartment only (a freezer) or contain both. The industry has nicknames for these units as well sometimes referring to them as a “cold box” or a “walk-in.” The dual compartment was introduced commercially by General Electric in 1939.

The vapor compression cycle is used in most household refrigerators. In this cycle, a circulating refrigerant such as freon enters the compressor as a vapor at its boiling point. The vapor is compressed and exits the compressor as a superheated vapor. The superheated vapor travels through part of the condenser which removes the superheat by cooling the vapor. The vapor travels through the remainder of the condenser and is condensed into a liquid at its boiling point. The saturated liquid refrigerant passes through the expansion valve where its pressure abruptly decreases. The decrease in pressure results in the flash evaporation and auto-refrigeration of a portion of the liquid (typically, less than half of the liquid flashes). The cold and partially vaporized refrigerant travels through the coil or tubes in the evaporator. There a fan circulates room air across the coil or tubes, and the refrigerant is totally vaporized, extracting heat from the air which is then returned to the food compartment. The refrigerant vapor returns to the compressor inlet to complete the thermodynamic cycle.

An absorption refrigerator works differently from a compressor refrigerator, using a source of heat, and typically runs more quietly.

The Peltier effect uses electricity directly to pump heat; refrigerators using this effect are sometimes used for camping, or where noise is not acceptable. They are totally silent, but less energy-efficient than other methods.

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.[3]

Types of domestic refrigerator

Household refrigerator output in 2000
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Household refrigerator output in 2000

Domestic refrigerators and freezers for food storage are made in a range of sizes. Amongst 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 true freezer may have a small compartment to make ice. 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.

Compressor refrigerators are by far the most common type; they make a noticeable noise. Absorption or Peltier units are used where quiet running is required; Peltier coolers are used in the smallest refrigerators as they have no bulky mechanism.

Compressor and Peltier refrigerators are invariably powered by electricity; absorption units can in principle be designed to be powered by any heat source. Gas-only and dual power gas/electricity units are available.

Refrigeration units for commercial and for non-food use are made in a huge range of sizes and styles.

The impact of the refrigerator on the home

Virtually all homes in the developed world have a refrigerator of one kind or another. The invention of the refrigerator has allowed the modern family to purchase, store, freeze, prepare and preserve food products in a fresh state for much longer periods of time than was previously possible. For the majority of families without a sizeable garden in which to grow vegetables and raise livestock, the advent of the refrigerator along with the modern supermarket led to a vastly more varied diet and improved health resulting from improved nutrition. Dairy products, meats, fish, poultry and vegetables can all 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 allows families to consume more salads, fresh fruits and vegetables during meals 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 the availability of domestic refrigeration.

The luxury of freezing allows households to purchase more foods in bulk that can be eaten at leisure while the bulk purchase provides cost savings (see economies of scale). Ice cream, a popular commodity of the 20th century, was previously only available by traveling long distances to where the product was made fresh and had to be eaten on the spot. Now it is a practically ubiquitous food item. Ice on-demand not only adds to the enjoyment of cold drinks, but is useful in first-aid applications, not to mention cold packs that can be kept frozen for picnics or in case of emergency.

Features

The inside of a common home refrigerator
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The inside of a common home refrigerator

Newer refrigerators may include:

  • Automatic defrosting: In any refrigerator, over time, water vapor in the air condenses onto the cooling coils as frost, eventually building up into a thick layer of ice. This ice acts as an insulator, reducing cooling efficiency. In the past, the ice was removed by periodically emptying the refrigerator and turning it off to let the ice melt, perhaps aided by hot water applied by the user (a process known as defrosting). In a refrigerator equipped for frost-free operation, however, a heater and a thermostat are fitted around the cooling coils. The cooling is periodically switched off (with the period varying between every 6 to 24 hours depending on the model) and the heater is turned on until the temperature around the coils slightly exceeds the freezing point of water, after which normal cooling resumes. This melts any frost which has collected around the coils. Melt water drops into a small gulley, through a small pipe which drains into a tray on the top of the compressor from which it is then evaporated into the surrounding air by residual heat generated by the operation of the compressor.[4]
  • A power failure warning, alerting the user by flashing a temperature display. The maximum temperature reached during the power failure may be displayed, along with information on whether the frozen food has defrosted or may contain harmful bacteria;
  • Chilled water and ice available from an in-door station, so the door need not be opened;
  • Cabinet rollers that allow the refigerator to be easily rolled around for easier cleaning;
  • Adjustable shelves and trays that can be moved around to suit the user;
  • A Status Indicator to notify the user when it is time to change the water filter;
  • An in-door ice caddy, which relocates the ice-maker storage to the freezer door and saves approximately 60 litres (about 2 cubic feet) of usable freezer space. It is also removable, and helps to prevent ice-maker clogging;
  • A cooling zone in the refrigerator door shelves. Air from the freezer section is diverted to the refrigerator door, to better cool milk or juice stored in the door shelf;
  • An LCD suggesting what types of food should be stored at what temperatures, and the expiration date of the food stored;
  • Extras unrelated to refrigeration, such as a television set, radio, or DVD player built into a door.

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 build up of frost required periodic thawing of the units to maintain their efficiency. Advances in frost-free refrigeration eliminating the thawing task were introduced in the 1950s. 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 entirely separate freezer compartment were introduced in the early 1960s, becoming the industry standard by the middle of that decade.

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 (1,2,2,2-tetrafluoroethane) instead of freon, which has no ozone layer depleting properties.

Disposal of discarded refrigerators is regulated, often mandating the removal of doors: children playing hide-and-seek have been asphyxiated while hiding inside a discarded refrigerator. This was particularly true for the older models that had latching doors. More modern units use a magnetic door gasket to hold the door sealed but can actually be pushed open from the inside. However, children can be unwittingly harmed by hiding inside any discarded refrigerator.[5]

Temperature zones and ratings

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

  • -18 °C (0 °F) (freezer)
  • 0 °C (32 °F) (meats)
  • 5 °C (40 °F) (refrigerator)
  • 10 °C (50 °F) (vegetables)

The capacity of a refrigerator is measured in either litres or cubic feet (US). 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 (for example, 1 through 9, warmest to coldest) by manufacturers, but generally 2 to 8 °C (36 to 46 °F) is ideal for the refrigerator compartment and -18 °C (0 °F) for the freezer. Some refrigerators require a certain external temperature (60 °F) to run properly. This can be an issue when placing a refrigerator 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.

  • *  : max temperature = -6°C. Maximum storage time for frozen food is 1 week
  • **  : max temperature = -12°C. Maximum storage time for frozen food is 1 month
  • ***  : max temperature = -18°C. Maximum storage time for frozen food is 3 months
  • *(***) : max temperature = -18°C. Maximum storage time for frozen food is up to 12 months

Although both the three and four star ratings specify the same maximum 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.

Media

  • Theater commercial, electric refrigerator, 1926
    Image:Theater commercial, electric refrigerator, 1926.ogg
    Largely graphic commercial for electric refrigerators in general and a refrigerator show, presumably in Pittsburgh, in particular. (7.61 MB, ogg/Theora format).


  • Problems seeing the videos? See media help.

See also

Notes

  1. ^ Pauken, Mike, P.E. (1999). Sleeping Soundly on Summer Nights (pdf). series on HVAC&R arts and sciences. ASHRAE. Retrieved on 2006-08-26.
  2. ^ "Refrigerators & Freezers", Energy Star. 
  3. ^ http://www.iifiir.org/en/doc/1051.pdf
  4. ^ Siemens Domestic Appliances FAQ Refrigeration (2006). Retrieved on 2007-01-26.
  5. ^ Adams, Cecil (2005). Is it impossible to open a refrigerator door from the inside?. Retrieved on 2006-08-31.

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Misspellings: refrigerator

Common misspelling(s) of refrigerator

  • refridgerator

 
Translations: Translations for: Refrigerator

Dansk (Danish)
n. - køleskab, kølerum

Nederlands (Dutch)
koelkast, koelcel

Français (French)
n. - réfrigérateur, frigidaire, chambre frigorifique

Deutsch (German)
n. - Kühlschrank

Ελληνική (Greek)
n. - ψυγείο

Italiano (Italian)
frigorifero

Português (Portuguese)
n. - geladeira (f)

Русский (Russian)
рефрижератор

Español (Spanish)
n. - frigorífico, nevera, refrigerador, heladera

Svenska (Swedish)
n. - kylskåp, kylare

中文（简体） (Chinese (Simplified))
冰箱, 雪柜, 冷冻库, 冷藏室

中文（繁體） (Chinese (Traditional))
n. - 冰箱, 雪櫃, 冷凍庫, 冷藏室

한국어 (Korean)
n. - 냉장고, 냉각 장치, 증기 응결기

日本語 (Japanese)
n. - 冷蔵庫, 冷却装置, 冷凍庫, 冷凍室, 冷凍装置

العربيه (Arabic)
‏(الاسم) ثلاجه‏

עברית (Hebrew)
n. - ‮מקרר‬

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Best of the Web: refrigerator

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American Sign Language
commtechlab.msu.edu
 
How?
home.howstuffworks.com
 
 
 

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Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
How Products are Made. How Products are Made. Copyright © 2002 by The Gale Group, Inc. All rights reserved.  Read more
Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved.  Read more
Architecture. McGraw-Hill Dictionary of Architecture and Construction. Copyright © 2003 by McGraw-Hill Companies, Inc. All rights reserved.  Read more
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