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Food in a refrigerator with its door open
Inside a regular family refrigerator - 360°-photo
show as 360° surround photography
A side-by-side refrigerator-freezer with an icemaker

A refrigerator (colloquially fridge, or fridgefreezer in the UK) is a popular household appliance that consists of a thermally insulated compartment and a heat pump (mechanical, electronic or chemical) that transfers heat from the inside of the fridge to its external environment so that the inside of the fridge is cooled to a temperature below the ambient temperature of the room. Refrigeration is an essential food storage technique in developed countries. The lower temperature lowers the reproduction rate of bacteria, so the refrigerator reduces the rate of spoilage. A refrigerator maintains a temperature a few degrees above the freezing point of water. Optimum temperature range for perishable food storage is 3 to 5 °C (37 to 41 °F).[1] A similar device that maintains a temperature below the freezing point of water is called a freezer. The refrigerator replaced the icebox, which had been a common household appliance for almost a century and a half. For this reason, a refrigerator is sometimes referred to as an icebox in American usage.

The first cooling systems for food involved using ice. Artificial refrigeration began in the mid-1750s, and developed in the early 1800s. In 1834, the first working vapor-compression refrigeration 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 a luxury item, became commonplace.

Freezer units are used in households and in industry and commerce. Commercial refrigerator and freezer units were in use for almost 40 years prior to the common home models. The freezer-on-top-and-refrigerator-on-bottom style has been the basic style since the 1940s, until modern 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 a dispenser in the door.

Domestic refrigerators and freezers for food storage are made in a range of sizes. Among the smallest is a 4 L 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 m wide with a capacity of 600 L. Refrigerators and freezers may be free-standing, or built into a kitchen. The refrigerator allows the modern household to keep food fresh for longer than before. Freezers allow people to buy food in bulk and eat it at leisure, and bulk purchases save money.


Refrigeration technology

Before the invention of the refrigerator, icehouses 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. The word "refrigeratory" was used at least as early as the 17th century[2]

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 a container of diethyl ether, which then boiled, absorbing heat from the surrounding air.[3] The experiment even created a small amount of ice, but had no practical application at that time.

Schematic of Dr. John Gorrie's 1841 mechanical ice machine.

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 the first working vapor-compression refrigeration system. It was a closed-cycle device that could operate continuously.[4] A similar attempt was made in 1842, by American physician, John Gorrie,[5] 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.


Ferdinand Carré's ice-making device

The first gas absorption refrigeration system using gaseous ammonia dissolved in water (referred to as "aqua ammonia") was developed by Ferdinand Carré of France in 1859 and patented in 1860. Carl von Linde, an engineering professor at the Technological University Munich in Germany, patented an improved method of liquefying gases in 1876. His new process made possible the use of gases such as ammonia (NH3), sulfur dioxide (SO2) and methyl chloride (CH3Cl) as refrigerants and they were widely used for that purpose until the late 1920s.

Domestic refrigerator

McCray pre-electric home refrigerator ad (1905). This company, founded in 1887, is still in business.




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 of the 1860s. The compressor assembly, which emitted a great deal of heat, was placed above 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. Many of these units are still functional today, after requiring little more service than a replacement start relay or thermostat if at all. These cooling systems cannot legally be recharged with the hazardous original refrigerants if they leak or break down.





Freezer units are used in households and in industry and commerce. Food stored at or below -18 °C (0 °F) is safe indefinitely.[8] 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. Refrigerators generally do not achieve lower than -23 °C (-9 °F), since 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 are generally upright units resembling refrigerators or chests (upright units laid on their backs). Many modern upright freezers come with an ice dispenser built into their door. Some upscale models include thermostat displays and controls, and sometimes flatscreen televisions as well.

Commercial and domestic refrigerators


A common commercial refrigerator is the glass fronted beverage cooler. These type of appliances are typically designed for specific re-load conditions meaning that they generally have a larger cooling system. This ensures that they are able to cope with a large throughput of drinks and frequent door opening. As a result, it is common for these types of commercial refrigerators to have energy consumption of >4 kWh/day.[9]

Styles of refrigerators


In the early 1950s most refrigerators were white, but from the mid-1950s through present day designers and manufacturers put color onto refrigerators. In the late-1950s/early-1960s, pastel colors like turquoise and pink became popular, brushed chrome-plating (similar to stainless finish) was available on some models from different brands. In the late 1960s and throughout the 1970s, earth tone colors were popular, including Harvest Gold, Avocado Green and almond. In the 1980s, black became fashionable. In the late 1990s stainless steel came into vogue, and in 2009, one manufacturer introduced multi-color designs.

Production by country

General technical explanation

Basic functioning of a refrigerator
Process and components of a conventional refrigerator
An Embraco compressor and fan-assisted condenser coil


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 the shaft seals. This leads to a requirement for periodic recharging and, if ignored, possible compressor failure.


The Peltier effect uses electricity to pump heat directly; refrigerators employing this system are sometimes used for camping, or in situations where noise 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.


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 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.[11] Changing the refrigerator temperature will inadvertently change the freezer temperature in the opposite direction. Changing the freezer temperature will have no effect on the refrigerator temperature. The freezer control may also be adjusted to compensate for any refrigerator adjustment.




"Ultra-cold" or "ultra-low temperature (ULT)" (typically -80C) freezers, as used for storing biological samples, also generally employ two stages of cooling, but in cascade. The lower temperature stage uses methane, or a similar gas, as a refrigerant, with its condenser kept at around -40C by a second stage which uses a more conventional refrigerant. Well known brands include Forma and Revco (both now Thermo Scientific) and Thermoline. For much lower temperatures (around -196C), laboratories usually purchase liquid nitrogen, kept in a Dewar flask, into which the samples are suspended.




Newer refrigerators may include:

  • Automatic defrosting
  • A power failure warning that alerts the user by flashing a temperature display. It may display the maximum temperature reached during the power failure, and whether frozen food has defrosted or may contain harmful bacteria.
  • Chilled water and ice from a dispenser in the door. Water and ice dispensing became available in the 1970s. In some refrigerators, the process of making ice is built-in so the user doesn't have to manually use ice trays. Some refrigerators have water chillers and water filtration systems.
  • Cabinet rollers that lets the refrigerator roll out for easier cleaning
  • Adjustable shelves and trays
  • A status indicator that notifies 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 (2 cu ft) 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 cool milk or juice stored in the door shelf.
  • A drop down door built into the refrigerator main door, giving easy access to frequently used items such as milk, thus saving energy by not having to open the main door.
  • A Fast Freeze function to rapidly cool foods by running the compressor for a predetermined amount of time and thus temporarily lowering the freezer temperature below normal operating levels. It is recommended to use this feature several hours before adding more than 1 kg of unfrozen food to the freezer. For freezers without this feature, lowering the temperature setting to the coldest will have the same effect.


In the early 1950s, the butter conditioner's patent was filed and published by the inventor Nave Alfred E. This feature was supposed to "provide a new and improved food storage receptacle for storing butter or the like which may quickly and easily be removed from the refrigerator cabinet for the purpose of cleaning."[13] Because of the high interest to the invention, companies in UK, New Zealand, and Australia started to include the feature into the mass fridge production and soon it became a symbol of the local culture. However, not long after that it was removed from production as according to the companies this was the only way for them to meet new ecology regulations and they found it inefficient to have a heat generating device inside a fridge.

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

An increasingly important environmental concern is the disposal of old refrigerators-- initially because freon coolant damages the ozone layer--but as older generation refrigerators wear out, the destruction of CFC-bearing insulation also 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. A R-134a is now becoming very uncommon in Europe. Newer refrigerants are being used instead. The main refrigerant now used is R-600a, or isobutane which has a smaller effect on the atmosphere if released. There have been reports of refrigerators exploding if the refrigerant leaks isobutane in the presence of a spark. If the coolant leaks into the fridge, at times when the door is not being opened (such as overnight) the concentration of coolant in the air within the fridge can build up to form an explosive mixture that can be ignited either by a spark from the thermostat or when the light comes on as the door is opened, resulting in documented cases of serious property damage and injury or even death from the resulting explosion.[14]

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. Since 2 August 1956, under U.S. federal law, refrigerator doors are no longer permitted to latch so they cannot be opened from the inside.[15] Modern units use a magnetic door gasket that holds the door sealed but allows it to be pushed open from the inside.[16] This gasket was invented, developed and manufactured by Max Baermann (1903-1984) of Bergisch Gladbach/Germany.[17]

Types of domestic refrigerators



Three distinct classes of refrigerator are common:

  • Compressor refrigerators are by far the most common type; they make a noticeable noise, but are most efficient and give greatest cooling effect. Portable compressor refrigerators for recreational vehicle (RV) and camping use are expensive but effective and reliable. Refrigeration units for commercial and industrial applications can be made in various sizes, shapes and styles to fit customer needs. Commercial and industrial refrigerators may have their compressors located away from the cabinet (similar to split system air conditioners) to reduce noise nuisance and reduce the load on air conditioning in hot weather.
  • Absorption refrigerators may be used in caravans and trailers, and dwellings lacking electricity, such as farms or rural cabins, where they have a long history. They may be powered by any heat source: gas (natural or propane) or kerosene being common. Models made for camping and RV use often have the option of running (inefficiently) on 12 volt battery power.
    • Solar refrigerators and Thermal mass refrigerators are designed to reduce electrical consumption. Solar refrigerators have the added advantage that they do not use refrigerants that are harmful to the environment or flammable. Typical solar designs are absorption refrigerators that use ammonia as the working gas, and employ large mirrors to concentrate sufficient sunlight to reach the temperature required to free gaseous ammonia from the solvent.[18][19] Most thermal mass refrigerators are designed to use electricity intermittently. As these units are heavily insulated, cooling load is limited primarily to heat introduced by new items to be refrigerated, and ambient air transfer when the unit is open. Very little power is therefore required if opened infrequently.
  • Peltier refrigerators are powered by electricity, usually 12 volt DC, but mains-powered wine coolers are available. Peltier refrigerators are inexpensive but inefficient and become progressively more inefficient with increased cooling effect; much of this inefficiency may be related to the temperature differential across the short distance between the "hot" and "cold" sides of the Peltier cell. Peltier refrigerators generally use heat sinks and fans to lower this differential; the only noise produced comes from the fan. Reversing the polarity of the voltage applied to the Peltier cells results in a heating rather than cooling effect.

Other specialised cooling mechanisms may be used for cooling, but have not been applied to domestic or commercial refrigerators.

  • Magnetic refrigerators are refrigerators that work on the magnetocaloric effect. The cooling effect is triggered by placing a metal alloy in a magnetic field.[20]
  • Acoustic refrigerators are refrigerators that use resonant linear reciprocating motors/alternators to generate a sound that is converted to heat and cold using compressed helium gas. The heat is discarded and the cold is routed to the refrigerator.

Energy efficiency

European energy label for a fridge.
Modern American-style / side-by-side refrigerators

In a house without air-conditioning (space heating and/or cooling) refrigerators consumed more energy than any other home device.[21] In the early 1990s a competition was held among the major manufacturers to encourage energy efficiency.[22] Current US models that are Energy Star qualified use 50% less energy than the average models made in 1974.[23] The most energy-efficient unit made in the US consumes about half a kilowatt-hour per day (equivalent to 20 W continuously).[24] But even ordinary units are quite 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 instead of the Energy Star; thus EU refrigerators at the point of sale are labelled according to how energy-efficient they are.



Many refrigerators made in the 1930s and 1940s were far more efficient than most that were made later. This is partly attributable to the addition of new features, such as auto-defrost, that reduced efficiency. Additionally, after World War 2, refrigerator style became more important than efficiency. This was especially true in the USA in the 1970s, when side-by-side models (known as American fridgefreezers outside of the US) with ice dispensers and water chillers became popular. However, the reduction in efficiency also arose partly from reduction in the amount of insulation to cut costs.


Because of the introduction of new energy efficiency standards, refrigerators made today are much more efficient than those made in the 1930s; they consume the same amount of energy while being three times as large.[27][28]




Frost-free refrigerators, including some early frost free refrigerator/freezers that used a cold plate in their refrigerator section instead of airflow from the freezer section, generally don't shut off their refrigerator fans during defrosting. This allows consumers to leave food in the main refrigerator compartment uncovered, and also helps keep vegetables moist. This method also helps reduce energy consumption, because the refrigerator is above freeze point and can pass the warmer-than-freezing air through the evaporator or cold plate to aid the defrosting cycle.


With the advent of digital inverter compressors, the energy consumption is even further reduced than a single-speed induction motor compressor, and thus contributes far less in the way of greenhouse gases. [30]

Effect on lifestyle

The refrigerator allows the modern family to keep food fresh for longer than before. The most notable improvement is for meat and other highly perishable wares, which needed to be refined to gain anything resembling shelf life.[] (On the other hand, refrigerators and freezers can also be stocked with processed, quick-cook foods that are less healthy.) Refrigeration in transit makes it possible to enjoy food from distant places.

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 food for reasons of hygiene).

Freezers allow people to buy food in bulk and eat it at leisure, and bulk purchases save money. Ice cream, a popular commodity of the 20th century, could previously only be obtained by traveling to where the product was made and eating it 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


  • -18 °C (0 °F) (freezer)
  • 0 °C (32 °F) (meat zone)
  • 5 °C (41 °F) (cooling zone)
  • 10 °C (50 °F) (crisper)

The capacity of a refrigerator is measured in either liters or cubic feet. Typically the volume of a combined refrigerator-freezer is split with 1/3rds to 1/4th of the volume allocated to the freezer although these values are highly variable.


  • [*]  : min temperature = -6 °C (21 °F). Maximum storage time for (pre-frozen) food is 1 week
  • [**]  : min temperature = -12 °C (10 °F). Maximum storage time for (pre-frozen) food is 1 month
  • [***]  : min temperature = -18 °C (0 °F). Maximum storage time for (pre-frozen) food is between 3 and 12 months depending on type (meat, vegetables, fish, etc.)



Commercial refrigeration temperatures

(from warmest to coolest)[31]

  • Refrigerators 35 °F to 38 °F, and not greater than maximum refrigerator temperature at 41 °F
  • Freezer, Reach-in -10 °F to +5 °F
  • Freezer, Walk-in -10 °F to 0 °F
  • Freezer, Ice Cream -20 °F to -10 °F

See also


  2. ^ Venetum Britannicum, 1676, London, p. 176 in the 1678 edition.
  5. ^ "Improved process for the artificial production of ice", U.S. Patent Office, Patent 8080, 1851 Archived 27 December 2016 at the Wayback Machine.
  6. ^ Dennis R. Heldman (29 August 2003). Encyclopedia of Agricultural, Food, and Biological Engineering (Print). CRC Press. p. 350. ISBN 978-0-8247-0938-9. Archived from the original on 5 May 2016. 
  7. ^ "The History of Household Wonders: History of the Refrigerator". History.com. A&E Television Networks. 2006. Archived from the original on March 26, 2008. 
  8. ^ "Freezing and food safety". USDA. Archived from the original on 18 September 2013. Retrieved 2013. 
  9. ^ "Chest Freezer Reviews". Archived from the original on 12 September 2017. 
  10. ^ Production - household refrigerators -- Country and Region Comparisons Archived 29 March 2013 at the Wayback Machine.. Statinfo.biz. Retrieved on 26 August 2013.
  11. ^ Refrigerator - Adjusting Temperature Controls. geappliances.com
  12. ^ James, Stephen J. (2003). "Developments in domestic refrigeration and consumer attitudes" (PDF). Bulletin of the IIR. 5. Archived from the original (PDF) on 19 March 2009. 
  13. ^ Butter Conditioner Archived 26 October 2016 at the Wayback Machine.. Google Patents.
  14. ^ "Archived copy". Archived from the original on 6 February 2016. Retrieved 2017.  Daily Mail February 2016, "Archived copy". Archived from the original on 5 August 2017. Retrieved 2017.  Daily Mirror November 2015, "Archived copy". Archived from the original on 25 February 2017. Retrieved 2017.  Daily Mail September 2009
  16. ^ Adams, Cecil (2005). "Is it impossible to open a refrigerator door from the inside?". Archived from the original on 7 July 2006. Retrieved 2006. 
  17. ^ "Archived copy". Archived from the original on 28 April 2016. Retrieved 2015. ; "Archived copy". Archived from the original on 23 December 2015. Retrieved 2015. 
  18. ^ The Green V. Your Refrigerator, Thermal Mass Fridges, And Sustainability. /blog.thegreenv.com. 17 July 2007.
  19. ^ LaMonica, Martin (14 September 2007) Hawaiian firm shrinks solar thermal power Archived 23 August 2012 at the Wayback Machine.. News.cnet.com.
  20. ^ "Towards the magnetic fridge" Archived 7 December 2008 at the Wayback Machine.. Physorg. 21 April 2006
  21. ^ "Which UK - Saving Energy". Which UK. Archived from the original on 10 November 2014. Retrieved 2014. 
  22. ^ Feist, J. W.; Farhang, R.; Erickson, J.; Stergakos, E. (1994). "Super Efficient Refrigerators: The Golden Carrot from Concept to Reality" (PDF). Proceedings of the ACEEE. 3: 3.67-3.76. Archived from the original (PDF) on 25 September 2013. 
  23. ^ "Refrigerators & Freezers". Energy Star. Archived from the original on 7 February 2006. 
  24. ^ Itakura, Kosuke. Sun Frost - The World's Most Efficient Refrigerators. Humboldt.edu
  25. ^ "High-efficiency specifications for REFRIGERATORS" (PDF). Consortium for Energy Efficiency. January 2007. Archived (PDF) from the original on 15 January 2013. 
  26. ^ "Understanding Energy Efficiency Standards". FridgeDimensions.com. Archived from the original on 2 November 2012. 
  27. ^ "Successes of Energy Efficiency: The United States and California National Trust" (PDF). Archived (PDF) from the original on 25 February 2012. 
  28. ^ Calwell, Chris & Reeder, Travis (2001). "Out With the Old, In With the New" (PDF). Natural Resources Defense Council. Archived (PDF) from the original on 8 June 2011. 
  29. ^ Kakaç, Sadik; Avelino, M. R.; Smirnov, H. F. (2012-12-06). Low Temperature and Cryogenic Refrigeration. Springer Science & Business Media. ISBN 9789401000994. 
  30. ^ How the Digital Inverter Compressor Has Transformed the Modern Refrigerator
  31. ^ Northeast Cooling | Category: Commercial Refrigeration Maintenance Tips Archived 22 April 2017 at the Wayback Machine.

Further reading

  • Rees, Jonathan. Refrigeration Nation: A History of Ice, Appliances, and Enterprise in America (Johns Hopkins University Press; 2013) 256 pages

External links




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