Last updated

Food in a refrigerator with its door open Open refrigerator with food at night.jpg
Food in a refrigerator with its door open
Exterior of a modern refrigerator A Samsung Refrigerator.jpg
Exterior of a modern refrigerator

A refrigerator, colloquially fridge, is a commercial and home appliance consisting of a thermally insulated compartment and a heat pump (mechanical, electronic or chemical) that transfers heat from its inside to its external environment so that its inside is cooled to a temperature below the room temperature. [1] Refrigeration is an essential food storage technique around the world. [2] The low 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. The optimal temperature range for perishable food storage is 3 to 5 °C (37 to 41 °F). [3] A similar device that maintains a temperature below the freezing point of water is called a freezer. [4] The refrigerator replaced the icebox, which had been a common household appliance for almost a century and a half. The United States Food and Drug Administration recommends that the refrigerator be kept at or below 4 °C (40 °F) and that the freezer be regulated at −18 °C (0 °F). [5]


The first cooling systems for food involved ice. [6] Artificial refrigeration began in the mid-1750s, and developed in the early 1800s. [7] In 1834, the first working vapor-compression refrigeration, using the same technology seen in air conditioners, system was built. [8] The first commercial ice-making machine was invented in 1854. [9] In 1913, refrigerators for home use were invented. [10] 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 as well as in industry and commerce. Commercial refrigerator and freezer units were in use for almost 40 years prior to the common home models. The freezer-over-refrigerator style had been the basic style since the 1940s, until modern, side-by-side refrigerators broke the trend. A vapor compression cycle is used in most household refrigerators, refrigerator–freezers and freezers. Newer refrigerators may include automatic defrosting, chilled water, and ice from a dispenser in the door.

Domestic refrigerators and freezers for food storage are made in a range of sizes. Among the smallest are Peltier-type refrigerators designed to chill beverages. A large domestic refrigerator stands as tall as a person and may be about one metre (3 ft 3 in) wide with a capacity of 0.6 m3 (21 cu ft). 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 perishable food in bulk and eat it at leisure, and make bulk purchases.


Commercial for electric refrigerators in Pittsburgh, Pennsylvania, 1926

Technology development

Ancient origins

Ancient Iranians were among the first to invent a form of cooler utilizing the principles of evaporative cooling and radiative cooling called yakhchāls. These complexes used subterranean storage spaces, a large thickly insulated above-ground domed structure, and outfitted with badgirs (wind-catchers) and series of qanats (aqueducts).[ citation needed ] [11]

Pre-electric refrigeration

In modern times, before the invention of the modern electric refrigerator, icehouses and iceboxes were used to provide cool storage for most of the year. Placed near freshwater lakes or packed with snow and ice during the winter, they were once very common. Natural means are still used to cool foods today. On mountainsides, runoff from melting snow 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. [12]

Artificial refrigeration

Gorrie Ice Machine.png
Schematic of Dr. John Gorrie's 1841 mechanical ice machine
Ferdinand Carré's ice-making device

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. [13] The experiment even created a small amount of ice, but had no practical application at that time.

In 1805, American inventor Oliver Evans described a closed vapor-compression refrigeration cycle for the production of ice by ether under vacuum. In 1820, the British scientist Michael Faraday liquefied ammonia and other gases by using high pressures and low temperatures, and in 1834, an American expatriate in Great Britain, Jacob Perkins, built the first working vapor-compression refrigeration system. It was a closed-cycle device that could operate continuously. [14] A similar attempt was made in 1842, by American physician, John Gorrie, [15] who built a working prototype, but it was a commercial failure. American engineer Alexander Twining took out a British patent in 1850 for a vapor compression system that used ether.

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

The first gas absorption refrigeration system (compressor-less and powered by a heat-source) was developed by Edward Toussaint of France in 1859 and patented in 1860. It used gaseous ammonia dissolved in water ("aqua ammonia").

Carl von Linde, an engineering professor at the Technological University Munich in Germany, patented an improved method of liquefying gases in 1876. His new process made possible the use of gases such as ammonia (NH3), sulfur dioxide (SO2) and methyl chloride (CH3Cl) as refrigerants, which were widely used for that purpose until the late 1920s despite safety concerns. [16]

Electric refrigerators

Production of refrigerators in France, ca. 1950s French Refrigerator Plant Increases its Productivity - DPLA - 95f3ac5808bd87d40bb4379003218b75.jpg
Production of refrigerators in France, ca. 1950s

In 1894, Hungarian inventor and industrialist István Röck started to manufacture a large industrial ammonia refrigerator which was powered by electric compressors (together with the Esslingen Machine Works). Its electric compressors were manufactured by the Ganz Works. At the 1896 Millennium Exhibition, Röck and the Esslingen Machine Works presented a 6-tonne capacity artificial ice producing plant. In 1906, the first large Hungarian cold store (with a capacity of 3,000 tonnes, the largest in Europe) opened in Tóth Kálmán Street, Budapest, the machine was manufactured by the Ganz Works. Until nationalisation after the Second World War, large-scale industrial refrigerator production in Hungary was in the hands of Röck and Ganz Works. [17]

Commercial refrigerator and freezer units, which go by many other names, were in use for almost 40 years prior to the common home models. They used gas systems such as ammonia (R-717) or sulfur dioxide (R-764), which occasionally leaked, making them unsafe for home use. Practical household refrigerators were introduced in 1915 and gained wider acceptance in the United States in the 1930s as prices fell and non-toxic, non-flammable synthetic refrigerants such as Freon-12 (R-12) were introduced. However, R-12 proved to be damaging to the ozone layer, causing governments to issue a ban on its use in new refrigerators and air-conditioning systems in 1994. The less harmful replacement for R-12, R-134a (tetrafluoroethane), has been in common use since 1990, but R-12 is still found in many old systems.

The glass-fronted beverage cooler is mostly used as a commercial refrigerator. These types of appliances are usually designed for specific load requirements, resulting in a larger cooling mechanism. 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 compose up to 50% of the energy usage of a supermarket. [18] Commercial refrigerators efficiency is primarily dependent on the compressor that moves. Refrigerators can be able to cause technical harm to the compressor in certain cases.[ clarification needed ] It can be restored or mounted again, depending on the degree of damage. Other kinds of damage, such as a cooler leak, can go undetected until serious problems arise. Health concerns are chief among these problems, with refrigerant poisoning being the most alarming. In order to detect harmful leaks early on, refrigerant levels need to be regularly monitored. Regular routine maintenance should avoid the risk of keeping food products at the right temperature. Even the slightest change in circumstances can affect consistency, resulting in breaches of food safety and potential penalties.[ opinion ][ citation needed ]

Residential refrigerators

DOMELRE refrigerator c. 1914 DOMELRE refrigerator c. 1914.png
DOMELRE refrigerator c. 1914

In 1913, the first electric refrigerators for home and domestic use were invented and produced by Fred W. Wolf of Fort Wayne, Indiana, with models consisting of a unit that was mounted on top of an ice box. [19] [20] His first device, produced over the next few years in several hundred units, was called DOMELRE. [21] [22] In 1914, engineer Nathaniel B. Wales of Detroit, Michigan, introduced an idea for a practical electric refrigeration unit, which later became the basis for the Kelvinator. A self-contained refrigerator, with a compressor on the bottom of the cabinet was invented by Alfred Mellowes in 1916. Mellowes produced this refrigerator commercially but was bought out by William C. Durant in 1918, who started the Frigidaire company to mass-produce refrigerators. In 1918, Kelvinator company introduced the first refrigerator with any type of automatic control. The absorption refrigerator was invented by Baltzar von Platen and Carl Munters from Sweden in 1922, while they were still students at the Royal Institute of Technology in Stockholm. It became a worldwide success and was commercialized by Electrolux. Other pioneers included Charles Tellier, David Boyle, and Raoul Pictet. Carl von Linde was the first to patent and make a practical and compact refrigerator.

These home units usually required the installation of the mechanical parts, motor and compressor, in the basement or an adjacent room while the cold box was located in the kitchen. There was a 1922 model that consisted of a wooden cold box, water-cooled compressor, an ice cube tray and a 0.25-cubic-metre (9 cu ft) compartment, and cost $714. (A 1922 Model-T Ford cost about $476.) By 1923, Kelvinator held 80 percent of the market for electric refrigerators. Also in 1923 Frigidaire introduced the first self-contained unit. About this same time porcelain-covered metal cabinets began to appear. Ice cube trays were introduced more and more during the 1920s; up to this time freezing was not an auxiliary function of the modern refrigerator.

General Electric "Monitor-Top" refrigerator, introduced in 1927, priced at $525, with the first all-steel cabinet, designed by Christian Steenstrup Monitor refer.jpg
General Electric "Monitor-Top" refrigerator, introduced in 1927, priced at $525, with the first all-steel cabinet, designed by Christian Steenstrup

The first refrigerator to see widespread use was the General Electric "Monitor-Top" refrigerator introduced in 1927, so-called, by the public, because of its resemblance to the gun turret on the ironclad warship USS Monitor of the 1860s. [24] 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. [25]

The introduction of Freon 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 term for the unit, popular at the time, was deep freeze. These devices, or appliances , did not go into mass production for use in the home until after World War II. [26] The 1950s and 1960s saw technical advances like automatic defrosting and automatic ice making. More efficient refrigerators were developed in the 1970s and 1980s, even though environmental issues led to the banning of very effective (Freon) refrigerants. Early refrigerator models (from 1916) had a cold compartment for ice cube trays. From the late 1920s fresh vegetables were successfully processed through freezing by the Postum Company (the forerunner of General Foods), which had acquired the technology when it bought the rights to Clarence Birdseye's successful fresh freezing methods.

Styles of refrigerators

In the early 1950s most refrigerators were white, but from the mid-1950s to the present day, designers and manufacturers have put color onto refrigerators. In the late-1950s/early-1960s, pastel colors like turquoise and pink became popular, and brushed chrome-plating (similar to a stainless steel finish) was available on some models. 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. Since 1961 the Color Marketing Group has attempted to coordinate the colors of appliances and other consumer goods.


Freezer units are used in households and in industry and commerce. Food stored at or below −18 °C (0 °F) is safe indefinitely. [27] Most household freezers maintain temperatures from −23 to −18 °C (−9 to 0 °F), although some freezer-only units can achieve −34 °C (−29 °F) and lower. Refrigerator freezers generally do not achieve lower than −23 °C (−9 °F), since the same coolant loop serves both compartments: Lowering the freezer compartment temperature excessively causes difficulties in maintaining above-freezing temperature in the refrigerator compartment. Domestic freezers can be included as a separate compartment in a refrigerator, or can be a separate appliance. Domestic freezers may be either upright, resembling a refrigerator, or chest freezers, wider than tall with the lid or door on top, sacrificing convenience for efficiency and partial immunity to power outages. [28] Many modern upright freezers come with an ice dispenser built into their door. Some upscale models include thermostat displays and controls.

Home freezers as separate compartments (larger than necessary just for ice cubes), or as separate units, were introduced in the United States in 1940. Frozen foods, previously a luxury item, became commonplace.

In 1955 the domestic deep freezer, which was cold enough to allow the owners to freeze fresh food themselves rather than buying food already frozen with Clarence Birdseye's process, went on sale. [29] [30]

Refrigerator technologies

Basic functioning of a refrigerator Refrigerator Cycle.svg
Basic functioning of a refrigerator
Process and components of a conventional refrigerator
Vapor compression cycle - A: hot compartment (kitchen), B: cold compartment (refrigerator box), I: insulation, 1: Condenser, 2: Expansion valve, 3: Evaporator unit, 4: Compressor Refrigerator-cycle.svg
Vapor compression cycle – A: hot compartment (kitchen), B: cold compartment (refrigerator box), I: insulation, 1: Condenser, 2: Expansion valve, 3: Evaporator unit, 4: Compressor
An Embraco compressor and fan-assisted condenser coil Refrigeration comp and coil.jpg
An Embraco compressor and fan-assisted condenser coil

Compressor refrigerators

A vapor compression cycle is used in most household refrigerators, refrigerator–freezers and freezers. In this cycle, a circulating refrigerant such as R134a enters a compressor as low-pressure vapor at or slightly below the temperature of the refrigerator interior. The vapor is compressed and exits the compressor as high-pressure superheated vapor. The superheated vapor travels under pressure through coils or tubes that make up the condenser; the coils or tubes are passively cooled by exposure to air in the room. The condenser cools the vapor, which liquefies. As the refrigerant leaves the condenser, it is still under pressure but is now only slightly above room temperature. This liquid refrigerant is forced through a metering or throttling device, also known as an expansion valve (essentially a pin-hole sized constriction in the tubing) to an area of much lower pressure. The sudden decrease in pressure results in explosive-like flash evaporation of a portion (typically about half) of the liquid. The latent heat absorbed by this flash evaporation is drawn mostly from adjacent still-liquid refrigerant, a phenomenon known as auto-refrigeration. This cold and partially vaporized refrigerant continues through the coils or tubes of the evaporator unit. A fan blows air from the compartment ("box air") across these coils or tubes and the refrigerant completely vaporizes, drawing further latent heat from the box air. This cooled air is returned to the refrigerator or freezer compartment, and so keeps the box air cold. Note that the cool air in the refrigerator or freezer is still warmer than the refrigerant in the evaporator. Refrigerant leaves the evaporator, now fully vaporized and slightly heated, and returns to the compressor inlet to continue the cycle.

Modern domestic refrigerators are extremely reliable because motor and compressor are integrated within a welded container, "sealed unit", with greatly reduced likelihood of leakage or contamination. By comparison, externally-coupled refrigeration compressors, such as those in automobile air conditioning, inevitably leak fluid and lubricant past the shaft seals. This leads to a requirement for periodic recharging and, if ignored, possible compressor failure.

Dual compartment designs

Refrigerators with two compartments need special design to control the cooling of refrigerator or freezer compartments. Typically, the compressors and condenser coils are mounted at the top of the cabinet, with a single fan to cool them both. This arrangement has a few downsides: each compartment cannot be controlled independently and the more humid refrigerator air is mixed with the dry freezer air. [31]

Multiple manufacturers offer dual compressor models. These models have separate freezer and refrigerator compartments that operate independently of each other, sometimes mounted within a single cabinet. Each has its own separate compressor, condenser and evaporator coils, insulation, thermostat, and door.[ citation needed ]

A hybrid between the two designs is using a separate fan for each compartment, the Dual Fan approach. Doing so allows for separate control and airflow on a single compressor system.[ citation needed ]

Absorption refrigerators

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.

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.

Peltier effect refrigerators

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.

Ultra-low temperature refrigerators

"Ultra-cold" or "ultra-low temperature (ULT)" (typically −80 or −86 °C [−112 or −123 °F]) freezers, as used for storing biological samples, also generally employ two stages of cooling, but in cascade. The lower temperature stage uses methane, or a similar gas, as a refrigerant, with its condenser kept at around −40 °C by a second stage which uses a more conventional refrigerant.

For much lower temperatures, laboratories usually purchase liquid nitrogen (−196 °C [−320.8 °F]), kept in a Dewar flask, into which the samples are suspended. Cryogenic chest freezers can achieve temperatures of down to −150 °C (−238 °F), and may include a liquid nitrogen backup.

Other refrigerators

Alternatives to the vapor-compression cycle not in current mass production include:


Many modern refrigerator/freezers have the freezer on top and the refrigerator on the bottom. Most refrigerator-freezers—except for manual defrost models or cheaper units—use what appears to be two thermostats. Only the refrigerator compartment is properly temperature controlled. When 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. [33] Changing the refrigerator temperature will inadvertently change the freezer temperature in the opposite direction.[ citation needed ] 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.[ citation needed ]

This means the refrigerator may become too warm. However, because only enough air is diverted to the refrigerator compartment, the freezer usually re-acquires the set temperature quickly, unless the door is opened. When a door is opened, either in the refrigerator or the freezer, the fan in some units stops immediately to prevent excessive frost build up on the freezer's evaporator coil, because this coil is cooling two areas. When the freezer reaches temperature, the unit cycles off, no matter what the refrigerator temperature is. Modern computerized refrigerators do not use the damper system. The computer manages fan speed for both compartments, although air is still blown from the freezer.[ citation needed ]


The inside of a home refrigerator containing a large variety of everyday food items Fridgeinterior.jpg
The inside of a home refrigerator containing a large variety of everyday food items

Newer refrigerators may include:

These older freezer compartments were the main cooling body of the refrigerator, and only maintained a temperature of around −6 °C (21 °F), which is suitable for keeping food for a week.

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

Types of domestic refrigerators

Domestic refrigerators and freezers for food storage are made in a range of sizes. Among the smallest is a 4-litre (0.14 cu ft) Peltier refrigerator advertised as being able to hold 6 cans of beer. A large domestic refrigerator stands as tall as a person and may be about 1 metre (3.3 ft) wide with a capacity of 600 litres (21 cu ft). Some models for small households fit under kitchen work surfaces, usually about 86 centimetres (34 in) high. Refrigerators may be combined with freezers, either stacked with refrigerator or freezer above, below, or side by side. A refrigerator without a frozen food storage compartment may have a small section just to make ice cubes. Freezers may have drawers to store food in, or they may have no divisions (chest freezers).

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

Three distinct classes of refrigerator are common:

Compressor refrigerators

Absorption refrigerator

Peltier refrigerators

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

Magnetic refrigerator

Energy efficiency

A European energy label for a refrigerator Energy label 2010.svg
A European energy label for a refrigerator

In a house without air-conditioning (space heating and/or cooling) refrigerators consumed more energy than any other home device. [36] In the early 1990s a competition was held among the major manufacturers to encourage energy efficiency. [37] Current US models that are Energy Star qualified use 50% less energy than the average models made in 1974. [38] The most energy-efficient unit made in the US consumes about half a kilowatt-hour per day (equivalent to 20 W continuously). [39] 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.

For US refrigerators, the Consortium on Energy Efficiency (CEE) further differentiates between Energy Star qualified refrigerators. Tier 1 refrigerators are those that are 20% to 24.9% more efficient than the Federal minimum standards set by the National Appliance Energy Conservation Act (NAECA). Tier 2 are those that are 25% to 29.9% more efficient. Tier 3 is the highest qualification, for those refrigerators that are at least 30% more efficient than Federal standards. [40] About 82% of the Energy Star qualified refrigerators are Tier 1, with 13% qualifying as Tier 2, and just 5% at Tier 3.[ citation needed ]

Besides the standard style of compressor refrigeration used in ordinary household refrigerators and freezers, there are technologies such as absorption refrigeration and magnetic refrigeration. Although these designs generally use a much larger amount of energy compared to compressor refrigeration, other qualities such as silent operation or the ability to use gas can favor these refrigeration units in small enclosures, a mobile environment or in environments where unit failure would lead to devastating consequences.[ citation needed ]

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 US 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.[ citation needed ]


Display of modern American-style / side-by-side refrigerators, available for purchase in a store ExpensiveRefrigerators.JPG
Display of modern American-style / side-by-side refrigerators, available for purchase in a store

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. [41] [42]

The efficiency of older refrigerators can be improved by defrosting (if the unit is manual defrost) and cleaning them regularly, replacing old and worn door seals with new ones, adjusting the thermostat to accommodate the actual contents (a refrigerator needn't be colder than 4 °C (39 °F) to store drinks and non-perishable items) and also replacing insulation, where applicable. Some sites recommend cleaning condenser coils every month or so on units with coils on the rear, to add life to the coils and not suffer an unnoticeable deterioration in efficiency over an extended period, the unit should be able to ventilate or "breathe" with adequate spaces around the front, back, sides and above the unit. If the refrigerator uses a fan to keep the condenser cool, then this must be cleaned or serviced, at per individual manufactures recommendations.[ citation needed ]

Auto defrosting

Frost-free refrigerators or freezers use electric fans to cool the appropriate compartment. [43] This could be called a "fan forced" refrigerator, whereas manual defrost units rely on colder air lying at the bottom, versus the warm air at the top to achieve adequate cooling. The air is drawn in through an inlet duct and passed through the evaporator where it is cooled, the air is then circulated throughout the cabinet via a series of ducts and vents. Because the air passing the evaporator is supposedly warm and moist, frost begins to form on the evaporator (especially on a freezer's evaporator). In cheaper and/or older models, a defrost cycle is controlled via a mechanical timer. This timer is set to shut off the compressor and fan and energize a heating element located near or around the evaporator for about 15 to 30 minutes at every 6 to 12 hours. This melts any frost or ice build-up and allows the refrigerator to work normally once more. It is believed that frost free units have a lower tolerance for frost, due to their air-conditioner-like evaporator coils. Therefore, if a door is left open accidentally (especially the freezer), the defrost system may not remove all frost, in this case, the freezer (or refrigerator) must be defrosted. [44]

If the defrosting system melts all the ice before the timed defrosting period ends, then a small device (called a defrost limiter) acts like a thermostat and shuts off the heating element to prevent too large a temperature fluctuation, it also prevents hot blasts of air when the system starts again, should it finish defrosting early. On some early frost-free models, the defrost limiter also sends a signal to the defrost timer to start the compressor and fan as soon as it shuts off the heating element before the timed defrost cycle ends. When the defrost cycle is completed, the compressor and fan are allowed to cycle back on. [44]

Frost-free refrigerators, including some early frost-free refrigerators/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.[ citation needed ]


Refrigerator in a rural store Kholodil'nik v sel'skom magazine.jpg
Refrigerator in a rural store

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. [45]

The energy consumption of a refrigerator is also dependent on the type of refrigeration being done. For instance, Inverter Refrigerators consume comparatively less energy than a typical non-inverter refrigerator. In an inverter refrigerator, the compressor is used conditionally on requirement basis. For instance, an inverter refrigerator might use less energy during the winters than it does during the summers. This is because the compressor works for a shorter time than it does during the summers.

Further, newer models of inverter compressor refrigerators take in to account various external and internal conditions to adjust the compressor speed and thus optimize cooling and energy consumption. Most of them use at least 4 sensors which help detect variance in external temperature, internal temperature owing to opening of the refrigerator door or keeping new food inside; humidity and usage patterns. Depending on the sensor inputs, the compressor adjusts its speed. For example, if door is opened or new food is kept, the sensor detects an increase in temperature inside the cabin and signals the compressor to increase its speed till a pre-determined temperature is attained. After which, the compressor runs at a minimum speed to just maintain the internal temperature. The compressor typically runs between 1200 and 4500 rpm. Inverter compressors not only optimizes cooling but is also superior in terms of durability and energy efficiency. [46] A device consumes maximum energy and undergoes maximum wear and tear when it switches itself on. As an inverter compressor never switches itself off and instead runs on varying speed, it minimizes wear and tear and energy usage. LG played a significant role in improving inverter compressors as we know it by reducing the friction points in the compressor and thus introducing Linear Inverter Compressors. Conventionally, all domestic refrigerators use a reciprocating drive which is connected to the piston. But in a linear inverter compressor, the piston which is a permanent magnet is suspended between two electromagnets. The AC changes the magnetic poles of the electromagnet, which results in the push and pull that compresses the refrigerant. LG claims that this helps reduce energy consumption by 32% and noise by 25% compared to their conventional compressors.

Form factor

The physical design of refrigerators also plays a large part in its energy efficiency. The most efficient is the chest-style freezer, as its top-opening design minimizes convection when opening the doors, reducing the amount of warm moist air entering the freezer. On the other hand, in-door ice dispensers cause more heat leakage, contributing to an increase in energy consumption. [47]


Global adoption

The gradual global adoption of refrigerators marks a transformative era in food preservation and domestic convenience. Since the refrigerators introduction in the 20th century, refrigerators have transitioned from being luxurious items to everyday commodities which have altered the understandings of food storage practices. Refrigerators have significantly impacted various aspects of many individual's daily lives by providing food safety to people around the world spanning across a wide variety of cultural and socioeconomic backgrounds.

The global adoption of refrigerators has also changed how societies handle their food supply. The introduction of the refrigerator in different societies has resulted in the monetization and industrialized mass food production systems which are commonly linked to increased food waste, animal wastes, and dangerous chemical wastes being traced back into different ecosystems. In addition, refrigerators have also provided an easier way to access food for many individuals around the world, with man options that commercialization has promoted leaning towards low-nutrient dense foods. [48]

After consumer refrigerators became financially viable for production and sale on a large scale, their prevalence around the globe expanded greatly. In the United States an estimated 99.5% of households have a refrigerator. [49] Refrigerator ownership are more common in developed western countries, but has stayed relatively low in eastern and developing countries despite its growing popularity. Throughout Eastern Europe and the Middle East, only 80% of its population own refrigerators. In addition to this, 65% of the population in China are stated to have refrigerators. The distribution of consumer refrigerators are also skewed as urban areas exhibit larger refrigeration ownership percentages compared to rural areas. [50]

Supplantation of the Ice Trade

The Ice Trade was a industry in the 19th and 20th century of the harvesting, transportation, and sale of natural and artificial ice for the purposes of refrigeration and consumption. The majority of the ice used for trade was harvested from North America and transported globally with some smaller operations working out of Norway. [51] With the introduction of more affordable large and home scale refrigeration around the 1920's, the need for large scale ice harvest and transportation was no longer needed, and the Ice Trade subsequently slowed and shrank to smaller scale local services or disappeared altogether. [52]

Effect on diet and lifestyle

The refrigerator allows households to keep food fresh for longer than before. The most notable improvement is for meat and other highly perishable wares, which previously needed to be preserved or otherwise processed for long term storage and transport. [53] This change in the supply chains of food products led to a marked increase in the quality of food in areas where refrigeration was being used. Additionally, the increased freshness and shelf life of food caused by the advent of refrigeration in addition to growing global communication methods has resulted in an increase in cultural exchange through food products from different regions of the world. There have also been claims that this increase in the quality of food is responsible for an increased in the height of United States citizens around the early 1900's. [53]

Refrigeration has also contributed to a decrease in the quality of food in some regions. By allowing, in part, for the phenomena of Globalization in the food sector, refrigeration has made the creation and transportation of ultra-processed foods and convenience foods inexpensive leading to their prevalence, especially in lower-income regions. These regions of lessened access to higher quality foods are referred to as Food Deserts.

Freezers allow people to buy food in bulk and eat it at leisure, and bulk purchases may 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

Residential units

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.

Temperature settings for refrigerator and freezer compartments are often given arbitrary numbers by manufacturers (for example, 1 through 9, warmest to coldest), but generally 3 to 5 °C (37 to 41 °F) [3] is ideal for the refrigerator compartment and −18 °C (0 °F) for the freezer. Some refrigerators must 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.

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

European freezers, and refrigerators with a freezer compartment, have a four star rating system to grade freezers. [54]

Blue Star.svgmin temperature: −6 °C (21 °F).
Maximum storage time for (pre-frozen) food is 1 week
Blue Star.svgBlue Star.svgmin temperature: −12 °C (10 °F).
Maximum storage time for (pre-frozen) food is 1 month
Blue Star.svgBlue Star.svgBlue Star.svgmin 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.)
Blue Star.svgBlue Star.svgBlue Star.svgBlue Star.svgmin temperature: −18 °C (0 °F).
Maximum storage time for pre-frozen or frozen-from-fresh food is between 3 and 12 months

Although both the three and four star ratings specify the same storage times and same minimum temperature of −18 °C (0 °F), only a four star freezer is intended for freezing fresh food, and may include a "fast freeze" function (runs the compressor continually, down to as low as −26 °C (−15 °F)) to facilitate this. Three (or fewer) stars are used for frozen food compartments that are only suitable for storing frozen food; introducing fresh food into such a compartment is likely to result in unacceptable temperature rises. This difference in categorization is shown in the design of the 4-star logo, where the "standard" three stars are displayed in a box using "positive" colours, denoting the same normal operation as a 3-star freezer, and the fourth star showing the additional fresh food/fast freeze function is prefixed to the box in "negative" colours or with other distinct formatting. [ citation needed ]

Most European refrigerators include a moist cold refrigerator section (which does require (automatic) defrosting at irregular intervals) and a (rarely frost free) freezer section.

Commercial refrigeration temperatures

(from warmest to coolest)

2 to 3 °C (35 to 38 °F), and not greater than maximum refrigerator temperature at 5 °C (41 °F)
Freezer, Reach-in
−23 to −15 °C (−10 to +5 °F)
Freezer, Walk-in
−23 to −18 °C (−10 to 0 °F)
Freezer, Ice Cream
−29 to −23 °C (−20 to −10 °F)


1941 Ad for Servel Electrolux Gas Refrigerator (Absorption), designed by Norman Bel Geddes. In 1998, CPSC warned that old units still in use could be deadly, and offered a $100 reward plus disposal costs to consumers who properly disposed of their old Servels. Servel Electrolux Gas Refrigerator ad, 1941.jpg
1941 Ad for Servel Electrolux Gas Refrigerator (Absorption), designed by Norman Bel Geddes. In 1998, CPSC warned that old units still in use could be deadly, and offered a $100 reward plus disposal costs to consumers who properly disposed of their old Servels.

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, unlike Freon. R-134a is becoming much rarer in Europe, where newer refrigerants are being used instead. The main refrigerant now used is R-600a (also known as 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 refrigerator, at times when the door is not being opened (such as overnight) the concentration of coolant in the air within the refrigerator 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. [60]

Disposal of discarded refrigerators is regulated, often mandating the removal of doors for safety reasons. Children playing hide-and-seek have been asphyxiated while hiding inside discarded refrigerators, particularly older models with latching doors, in a phenomenon called refrigerator death. Since 2 August 1956, under U.S. federal law, refrigerator doors are no longer permitted to latch and they can be opened from the inside. [61] Modern units use a magnetic door gasket that holds the door sealed but allows it to be pushed open from the inside. [62] This gasket was invented, developed and manufactured by Max Baermann (1903–1984) of Bergisch Gladbach/Germany. [63] [64]

Regarding total life-cycle costs, many governments offer incentives to encourage recycling of old refrigerators. One example is the Phoenix refrigerator program launched in Australia. This government incentive picked up old refrigerators, paying their owners for "donating" the refrigerator. The refrigerator was then refurbished, with new door seals, a thorough cleaning and the removal of items, such as the cover that is strapped to the back of many older units. The resulting refrigerators, now over 10% more efficient, were then distributed to low-income families.[ citation needed ]

Similar to the Australian program, the United States also has a program for collecting and replacing older less efficient refrigerators and other White Goods. [65] These programs seek to collect large appliances that may be old and inefficient or breaking, and replace them with newer and more efficient appliances. This is in an effort to reduce the cost of the additional cost these appliances impose on lower-income families through their inefficient energy and gas usage, as well as reduce pollution caused by the continued use of these appliances.

Inside a regular family refrigerator - 360deg photo
(view as a 360deg interactive panorama) Inside a refrigerator - 360deg Photo.jpg
Inside a regular family refrigerator – 360° photo
( view as a 360° interactive panorama )

See also

Related Research Articles

<span class="mw-page-title-main">Refrigeration</span> Process of moving heat from one location to another in controlled conditions

Refrigeration is any of various types of cooling of a space, substance, or system to lower and/or maintain its temperature below the ambient one. Refrigeration is an artificial, or human-made, cooling method.

<span class="mw-page-title-main">Heat pump</span> System that transfers heat from one space to another

A heat pump is a device that uses work to transfer heat from a cool space to a warm space by transferring thermal energy using a refrigeration cycle, cooling the cool space and warming the warm space. In cold weather, a heat pump can move heat from the cool outdoors to warm a house; the pump may also be designed to move heat from the house to the warmer outdoors in warm weather. As they transfer heat rather than generating heat, they are more energy-efficient than other ways of heating or cooling a home.

<span class="mw-page-title-main">Dehumidifier</span> Device which reduces humidity

A dehumidifier is an air conditioning device which reduces and maintains the level of humidity in the air. This is done usually for health or thermal comfort reasons, or to eliminate musty odor and to prevent the growth of mildew by extracting water from the air. It can be used for household, commercial, or industrial applications. Large dehumidifiers are used in commercial buildings such as indoor ice rinks and swimming pools, as well as manufacturing plants or storage warehouses. Typical air conditioning systems combine dehumidification with cooling, by operating cooling coils below the dewpoint and draining away the water that condenses.

<span class="mw-page-title-main">Frozen food</span> Food stored at temperatures below the freezing point of water, for extending its shelf life

Freezing food preserves it from the time it is prepared to the time it is eaten. Since early times, farmers, fishermen, and trappers have preserved grains and produce in unheated buildings during the winter season. Freezing food slows decomposition by turning residual moisture into ice, inhibiting the growth of most bacterial species. In the food commodity industry, there are two processes: mechanical and cryogenic. The freezing kinetics is important to preserve the food quality and texture. Quicker freezing generates smaller ice crystals and maintains cellular structure. Cryogenic freezing is the quickest freezing technology available due to the ultra low liquid nitrogen temperature −196 °C (−320 °F).

<span class="mw-page-title-main">Evaporative cooler</span> Device that cools air through the evaporation of water

An evaporative cooler is a device that cools air through the evaporation of water. Evaporative cooling differs from other air conditioning systems, which use vapor-compression or absorption refrigeration cycles. Evaporative cooling exploits the fact that water will absorb a relatively large amount of heat in order to evaporate. The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation). This can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants.

<span class="mw-page-title-main">Chiller</span> Machine that removes heat from a liquid coolant via vapor compression

A chiller is a machine that removes heat from a liquid coolant via a vapor-compression, adsorption refrigeration, or absorption refrigeration cycles. This liquid can then be circulated through a heat exchanger to cool equipment, or another process stream. As a necessary by-product, refrigeration creates waste heat that must be exhausted to ambience, or for greater efficiency, recovered for heating purposes. Vapor compression chillers may use any of a number of different types of compressors. Most common today are the hermetic scroll, semi-hermetic screw, or centrifugal compressors. The condensing side of the chiller can be either air or water cooled. Even when liquid cooled, the chiller is often cooled by an induced or forced draft cooling tower. Absorption and adsorption chillers require a heat source to function.

<span class="mw-page-title-main">Defrosting (refrigeration)</span> Removal of frost and ice from a refrigerator

In refrigerators, defrosting is the removal of frost and ice.

Auto-defrost, automatic defrost or self-defrosting is a technique which regularly defrosts the evaporator in a refrigerator or freezer. Appliances using this technique are often called frost free, frostless, or no-frost.

<span class="mw-page-title-main">Icemaker</span> Consumer device for making ice, found inside a freezer

An icemaker, ice generator, or ice machine may refer to either a consumer device for making ice, found inside a home freezer; a stand-alone appliance for making ice, or an industrial machine for making ice on a large scale. The term "ice machine" usually refers to the stand-alone appliance.

<span class="mw-page-title-main">Icyball</span> Early refrigerator invented in the 1920s

Icyball is a name given to two early refrigerators, one made by Australian Sir Edward Hallstrom in 1923, and the other design patented by David Forbes Keith of Toronto, and manufactured by American Powel Crosley Jr., who bought the rights to the device. Both devices are unusual in design in that they did not require the use of electricity for cooling. They can run for a day on a cup of kerosene, allowing rural users lacking electricity the benefits of refrigeration.

<span class="mw-page-title-main">Absorption refrigerator</span> Refrigerator that uses a heat source

An absorption refrigerator is a refrigerator that uses a heat source to provide the energy needed to drive the cooling process. Solar energy, burning a fossil fuel, waste heat from factories, and district heating systems are examples of convenient heat sources that can be used. An absorption refrigerator uses two coolants: the first coolant performs evaporative cooling and then is absorbed into the second coolant; heat is needed to reset the two coolants to their initial states. Absorption refrigerators are commonly used in recreational vehicles (RVs), campers, and caravans because the heat required to power them can be provided by a propane fuel burner, by a low-voltage DC electric heater or by a mains-powered electric heater. Absorption refrigerators can also be used to air-condition buildings using the waste heat from a gas turbine or water heater in the building. Using waste heat from a gas turbine makes the turbine very efficient because it first produces electricity, then hot water, and finally, air-conditioning—trigeneration.

Economizers, or economisers (UK), are mechanical devices intended to reduce energy consumption, or to perform useful function such as preheating a fluid. The term economizer is used for other purposes as well. Boiler, power plant, heating, refrigeration, ventilating, and air conditioning (HVAC) uses are discussed in this article. In simple terms, an economizer is a heat exchanger.

<span class="mw-page-title-main">Vapor-compression refrigeration</span> Refrigeration process

Vapour-compression refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air conditioning of buildings and automobiles. It is also used in domestic and commercial refrigerators, large-scale warehouses for chilled or frozen storage of foods and meats, refrigerated trucks and railroad cars, and a host of other commercial and industrial services. Oil refineries, petrochemical and chemical processing plants, and natural gas processing plants are among the many types of industrial plants that often utilize large vapor-compression refrigeration systems. Cascade refrigeration systems may also be implemented using two compressors.

<span class="mw-page-title-main">Absorption heat pump</span> Heat pump driven by thermal energy

An absorption heat pump (AHP) is a heat pump driven by thermal energy such as combustion of natural gas, steam solar-heated water, air or geothermal-heated water differently from compression heat pumps that are driven by mechanical energy. AHPs are more complex and require larger units compared to compression heat pumps. In particular, the lower electricity demand of such heat pumps is related to the liquid pumping only. Their applications are restricted to those cases when electricity is extremely expensive or a large amount of unutilized heat at suitable temperatures is available and when the cooling or heating output has a greater value than heat input consumed. Absorption refrigerators also work on the same principle, but are not reversible and cannot serve as a heat source.

<span class="mw-page-title-main">Air source heat pump</span> Most common type of heat pump

An air source heat pump (ASHP) is a heat pump that can absorb heat from air outside a building and release it inside; it uses the same vapor-compression refrigeration process and much the same equipment as an air conditioner, but in the opposite direction. ASHPs are the most common type of heat pump and, usually being smaller, tend to be used to heat individual houses or flats rather than blocks, districts or industrial processes.

<span class="mw-page-title-main">Heat pump and refrigeration cycle</span> Mathematical models of heat pumps and refrigeration

Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pump, air conditioning and refrigeration systems. A heat pump is a mechanical system that transmits heat from one location at a certain temperature to another location at a higher temperature. Thus a heat pump may be thought of as a "heater" if the objective is to warm the heat sink, or a "refrigerator" or “cooler” if the objective is to cool the heat source. The operating principles in both cases are the same; energy is used to move heat from a colder place to a warmer place.

Natural refrigerants are considered substances that serve as refrigerants in refrigeration systems. They are alternatives to synthetic refrigerants such as chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), and hydrofluorocarbon (HFC) based refrigerants. Unlike other refrigerants, natural refrigerants can be found in nature and are commercially available thanks to physical industrial processes like fractional distillation, chemical reactions such as Haber process and spin-off gases. The most prominent of these include various natural hydrocarbons, carbon dioxide, ammonia, and water. Natural refrigerants are preferred actually in new equipment to their synthetic counterparts for their presumption of higher degrees of sustainability. With the current technologies available, almost 75 percent of the refrigeration and air conditioning sector has the potential to be converted to natural refrigerants.

HVAC is a major sub discipline of mechanical engineering. The goal of HVAC design is to balance indoor environmental comfort with other factors such as installation cost, ease of maintenance, and energy efficiency. The discipline of HVAC includes a large number of specialized terms and acronyms, many of which are summarized in this glossary.

<span class="mw-page-title-main">Pumpable ice technology</span> Type of technology to produce and use fluids or secondary refrigerants

Pumpable icetechnology (PIT) uses thin liquids, with the cooling capacity of ice. Pumpable ice is typically a slurry of ice crystals or particles ranging from 5 micrometers to 1 cm in diameter and transported in brine, seawater, food liquid, or gas bubbles of air, ozone, or carbon dioxide.

<span class="mw-page-title-main">ULT freezer</span> Freezer used for storing contents at unusually low temperatures

An ultra low temperature (ULT) freezer is a refrigerator that stores contents at −80 to −86 °C. An ultra low temperature freezer is commonly referred to as a "minus 80 freezer" or a "negative 80 freezer", referring to the most common temperature standard. ULT freezers come in upright and chest freezer formats.


  1. Peavitt, Helen (15 November 2017). Refrigerator: The Story of Cool in the Kitchen. Reaktion Books. p. 8. ISBN   978-1-78023-797-8.
  2. Aung, Myo Min; Chang, Yoon Seok (11 October 2022). Cold Chain Management. Springer Nature. p. 46. ISBN   978-3-031-09567-2.
  3. 1 2 . Keep your fridge-freezer clean and ice-free. BBC. 30 April 2008
  4. R, Rajesh Kumar (1 August 2020). Basics of Mechanical Engineering. Jyothis Publishers. p. 117. ISBN   978-93-5254-883-5.
  5. . Are You Storing Food Safely? Archived 5 March 2022 at the Wayback Machine FDA. 9 February 2021
  6. Accorsi, Riccardo; Manzini, Riccardo (12 June 2019). Sustainable Food Supply Chains: Planning, Design, and Control through Interdisciplinary Methodologies. Academic Press. p. 189. ISBN   978-0-12-813412-2.
  7. Traitler, Helmut; Dubois, Michel J. F.; Heikes, Keith; Petiard, Vincent; Zilberman, David (5 February 2018). Megatrends in Food and Agriculture: Technology, Water Use and Nutrition. John Wiley & Sons. p. 120. ISBN   978-1-119-39114-2.
  8. Yahia, Elhadi M. (16 July 2019). Postharvest Technology of Perishable Horticultural Commodities. Woodhead Publishing. p. 212. ISBN   978-0-12-813277-7.
  9. Zhang, Ce; Yang, Jianming (3 January 2020). A History of Mechanical Engineering. Springer Nature. p. 117. ISBN   978-981-15-0833-2.
  10. O'Reilly, Catherine (17 November 2008). Did Thomas Crapper Really Invent the Toilet?: The Inventions That Changed Our Homes and Our Lives. Skyhorse Publishing, Inc. ISBN   978-1-62873-278-8.
  11. Ebrahimi, Ali; Shayegani, Aida; Zarandi, Mahnaz Mahmoudi (2021). "Thermal Performance of Sustainable Element in Moayedi Icehouse in Iran". International Journal of Architectural Heritage. 15 (5): 740–756. doi:10.1080/15583058.2019.1645243. S2CID   202094054 . Retrieved 2 February 2021.
  12. Venetum Britannicum, 1676, London, p. 176 in the 1678 edition.
  13. Arora, Ramesh Chandra (30 March 2012). "Mechanical vapour compression refrigeration". Refrigeration and Air Conditioning. New Delhi, India: PHI Learning. p. 3. ISBN   978-81-203-3915-6.
  14. Burstall, Aubrey F. (1965). A History of Mechanical Engineering. The MIT Press. ISBN   0-262-52001-X.
  15. US 8080A,John Gorrie,"Improved process for the artificial production of ice",issued 1851-05-06 Archived 11 March 2022 at the Wayback Machine
  16. "Refrigerator vacuum dehydration unit". Vacuum. 28 (2): 81. February 1978. doi:10.1016/s0042-207x(78)80528-4. ISSN   0042-207X.
  17. The development and heyday of mechanical science (Hungarian)
  18. Fricke, Brian; Becker, Bryan (12 June 2010). "Energy Use of Doored and Open Vertical Refrigerated Display Cases". International Refrigeration and Air Conditioning Conference via Purdue e-Pubs.
  19. US 1126605,Fred W. Wolf,"Refrigerating apparatus",issued 1915-01-26 Archived 7 March 2022 at the Wayback Machine
  20. 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.
  21. "DOMELRE First Electric Refrigerator |". Archived from the original on 2 August 2021. Retrieved 2 August 2021.
  22. "Air Conditioning and Refrigeration History - part 3 - Greatest Engineering Achievements of the Twentieth Century". Archived from the original on 2 August 2021. Retrieved 2 August 2021.
  23. "G.E. Monitor Top Refrigerator". Archived from the original on 16 April 2020. Retrieved 25 January 2020.
  24. Lobocki, Neil (4 October 2017). "The General Electric Monitor Top Refrigerator". Archived from the original on 25 January 2020. Retrieved 25 January 2020.
  25. "GE Monitor-Top Refrigerator - Albany Institute of History and Art". Archived from the original on 6 August 2020. Retrieved 1 June 2020.
  26. "The History of Household Wonders: History of the Refrigerator". . A&E Television Networks. 2006. Archived from the original on 26 March 2008.
  27. "Freezing and food safety". USDA. Archived from the original on 18 September 2013. Retrieved 6 August 2013.
  28. "Advertising". The Australian Women's Weekly . Australia. 19 September 1973. p. 26. Archived from the original on 25 April 2023. Retrieved 13 January 2020 via Trove.
  29. Barnes-Svarney, Patricia; Svarney, Thomas E. (23 February 2015). The Handy Nutrition Answer Book. Visible Ink Press. ISBN   9781578595532. Archived from the original on 25 April 2023. Retrieved 14 March 2023.
  30. "Power To The People – Chicago Tribune". Chicago Tribune . 25 February 1990. Archived from the original on 16 January 2023. Retrieved 16 January 2023.
  31. "What is Dual-Cooling Technology?". Archived from the original on 6 August 2020. Retrieved 13 May 2020.
  32. 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.
  33. Refrigerator – Adjusting Temperature Controls.
  34. US 2579848,Alfred E. Nave,"Butter conditioner",issued 1951-12-25 Archived 15 April 2021 at the Wayback Machine
  35. "Towards the magnetic fridge" Archived 7 December 2008 at the Wayback Machine . Physorg. 21 April 2006
  36. "Which UK – Saving Energy". Which UK. Archived from the original on 10 November 2014. Retrieved 10 November 2014.
  37. 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.
  38. "Refrigerators & Freezers". Energy Star . Archived from the original on 7 February 2006.
  39. Itakura, Kosuke. Sun Frost – The World's Most Efficient Refrigerators.
  40. "High-efficiency specifications for REFRIGERATORS" (PDF). Consortium for Energy Efficiency. January 2007. Archived (PDF) from the original on 15 January 2013.
  41. "Successes of Energy Efficiency: The United States and California National Trust" (PDF). Archived (PDF) from the original on 25 February 2012.
  42. 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.
  43. Kakaç, Sadik; Avelino, M. R.; Smirnov, H. F. (6 December 2012). Low Temperature and Cryogenic Refrigeration. Springer Science & Business Media. ISBN   9789401000994. Archived from the original on 25 April 2023. Retrieved 13 December 2017.
  44. 1 2 Badri, Deyae; Toublanc, Cyril; Rouaud, Olivier; Havet, Michel (1 November 2021). "Review on frosting, defrosting and frost management techniques in industrial food freezers". Renewable and Sustainable Energy Reviews. 151: 111545. doi:10.1016/j.rser.2021.111545. ISSN   1364-0321.
  45. "How the Digital Inverter Compressor Has Transformed the Modern Refrigerator". Archived from the original on 15 February 2020. Retrieved 25 January 2020.
  46. Chang, Wen Ruey; Liu, Der Yeong; Chen, San Guei; and Wu, Nan Yi, "The Components and Control Methods for Implementation of Inverter-Controlled Refrigerators/Freezers" (2004). International Refrigeration and Air Conditioning Conference. Paper 696.
  47. Technology Connections (7 April 2020). "Chest Freezers; What they tell us about designing for X". YouTube. Archived from the original on 12 May 2020. Retrieved 13 May 2020.
  48. Meuse, Matt (21 April 2023). "How the humble household refrigerator changed the world — for better and for worse".
  49. "Not just a cool convenience: How electric refrigeration shaped the "cold chain"". 5 November 2015. Retrieved 5 December 2023.
  50. Martinez, Sebastian; Murguia, Juan M.; Rejas, Brisa; Winters, Solis (13 January 2021). "Refrigeration and child growth: What is the connection?". Maternal & Child Nutrition. 17 (2): e13083. doi:10.1111/mcn.13083. ISSN   1740-8695. PMC   7988856 . PMID   33439555.
  51. Clemen, Rudolf A. “The American Ice Harvests: An Historical Study in Technology, 1800–1918. By Richard O. Cummings. Berkeley and Los Angeles: University of California Press, 1949. Pp. x, 184. $3.00.” The Journal of economic history 10.2 (1950): 226–227. Web.
  52. "Tracing the History of New England's Ice Trade". Boston University. 7 February 2022. Retrieved 4 December 2023.
  53. 1 2 Craig, L. A. (1 June 2004). "The Effect of Mechanical Refrigeration on Nutrition in the United States". Social Science History. 28 (2): 325–336. doi:10.1215/01455532-28-2-325 (inactive 12 February 2024). ISSN   0145-5532.{{cite journal}}: CS1 maint: DOI inactive as of February 2024 (link)
  54. Commission Regulation (EU) 2019/2019 of 1 October 2019 laying down ecodesign requirements for refrigerating appliances pursuant to Directive 2009/125/EC of the European Parliament and of the Council and repealing Commission Regulation (EC) No 643/2009 (Text with EEA relevance.), 5 December 2019, archived from the original on 25 April 2023, retrieved 21 October 2020
  55. Lobocki, Neil (4 October 2017). "The First Absorption Refrigerator". Archived from the original on 26 January 2020. Retrieved 25 January 2020.
  56. US 95817S,Norman Bel Geddes,"Design for a refrigerator cabinet",issued 1935-06-04 Archived 11 March 2022 at the Wayback Machine
  57. US 2127212A,Norman Bel Geddes,"Refrigerator",published 1935-07-24,issued 1938-08-16 Archived 13 June 2021 at the Wayback Machine
  58. "Norman Bel Geddes Database". Archived from the original on 26 January 2020. Retrieved 25 January 2020.
  59. "CPSC, Warns That Old Servel Gas Refrigerators Still In Use Can Be Deadly". U.S. Consumer Product Safety Commission. 19 May 2016. Archived from the original on 26 January 2020. Retrieved 25 January 2020.
  60. "Tragic bride-to-be's fridge-freezer exploded and 'turned into a Bunsen burner'". Daily Mirror . 12 November 2015. Archived from the original on 5 August 2017. Retrieved 14 June 2017. Daily Mirror November 2015
  62. Adams, Cecil (2005). "Is it impossible to open a refrigerator door from the inside?". Archived from the original on 7 July 2006. Retrieved 31 August 2006.
  63. Max Baermann GMBH. "Flexible Magnetic Strips". Archived from the original on 28 April 2016. Retrieved 20 June 2020.
  64. US 2959832,Max Baermann,"Flexible or resilient permanent magnets",issued 1960-11-15 Archived 7 March 2022 at the Wayback Machine
  65. Haney, Kevin (4 December 2023). "Free Appliance Replacement: Low-Income Government Programs". Retrieved 5 December 2023.

Further reading