Domestic refrigerators (usually shortened to fridge) are amongst the most common electric applicances in the world, for instance being present in 99.5% of American homes. They use refrigeration to help preserve food. They invariably work using phase change heat pumps operating in a refrigeration cycle.

They may consist of either a cooling compartment only (a larder refrigerator) or a freezing compartment only (a freezer) or contain both. The dual compartment was introduced commercially by General Electric in 1939. Some refrigerators are now divided into four zones for the storage of different types of food:

• -18°C or 0°F (freezer)
• 0°C or 32°F (meats)
• 4°C or 40°F (refrigerator)
• 10°C or 50°F (vegetables), for the storage of different food types.

The capacity of the refrigerator (freezer and/or fridge) is measured in litres (or cu. ft.). Typically the freezer volume is 100 litres (this will vary) and the fridge 140 litres.

Contents

1 Types 1.1 Freezer situation 2 Features 3 Microwave-refrigerator combo 4 History 5 External links

Types

• Freestanding
• Built under: fridges and freezers which can be installed under the counter top.
• Integrated.
• In-Column fridges or freezers: these are built into a tall cabinet in your kitchen furniture. The appliance is built in to your kitchen so that it looks like a normal cupboard. Getting the right size fridge is very important when choosing integrated.

Freezer situation

• Eye level freezer refrigerator (or top mount).
• Bottom freezer refrigerator (or bottom mount). The freezer is generally bigger and the refrigerator has two independent motor-compressors.

Features

Some newer refrigerators may feature:

• An LCD suggesting what types of food should be stored at what temperatures and the expiry date of the food stored.

• Filter Status Indicator tells you when it's time for a change

• A power failure warning, alerting the user to the failure, usually by flashing the temperature display. The maximum temperature reached during the power failure may be displayed, along with information on whether the frozen food has defrosted or may contain harmful bacteria.

• Frost-free operation. Over time atmospheric water vapour condenses onto the cooling coils as ice, which can eventually build up into a layer several centimetres thick. This can be removed by emptying the refrigerator and turning it off so that the ice melts. In a refrigerator equipped for frost-free operation, a heater and a thermostat are fitted around the cooling coils. Every six hours or so the cooling is switched off and the heater turned on until the temperature around the coils slightly exceeds the freezing point of water when normal cooling is restored. This melts any ice which has collected around the coils and prevents it from building up.

An increasingly important environmental concern is the disposal of old refrigerators - initially because of the freon coolant damaging the ozone layer, but as the older generation of refrigerators disappears it is the destruction of CFC-bearing insulation which causes concern. Modern refrigerators usually use a refrigerant called HFC-134a (1,2,2,2-tetrafluoroethane) instead of freon, which has no ozone layer depleting properties.

Microwave-refrigerator combo

A microwave/refrigerator combo is a freezer, fridge and microwave oven combined into a single, compact, energy-efficient unit. The foods can be translated from one compartiment to the other one following a timer to defrost, warm and cook them (with a week program, if necessary).

History

Although ice houses have been used for thousands of years to provide a source of ice in summer, the first common domestic refrigeration was in the form of ice boxes in the latter years of the 19th Century. As the ice melted it was replaced with ice bought from commercial manufacturers.

1856, Using the principal of vapour compression, Australian James Harrison produced the world's first practical refrigerator. He was commissioned by a brewery to build a machine that cooled beer.

The first domestic refrigerator was apparently manufactured in 1913 by Fred W. Wolf Jnr. in Chicago, and called the DOMELRE (DOMestic ELectric REfrigerator). It was not commercially successful, that distinction apparently going to the Kelvinator Company. This company was formed in May 1916 as the Electro-Automatic Refrigerating Company by Edmund J. Copeland and an industrialist, Arnold H. Gross. The company was renamed within two months to the Kelvinator Company and produced their first model shortly afterwards. Like most of their modern descendents, this refrigerator cooled using a phase change heat pump.

The first refrigerators were of the "remote" type, essentially an upgrade of an existing ice box with the installation of a cooling unit in it, but the motor, compressor and condenser installed either beside it or in the basement. The first self-contained refrigerators were not manufactured until 1925.

The earliest units used a toxic gas, sulfur dioxide as their refrigerant, converting it between gas and liquid through mechanical compression. It was not until the 1930s that General Motors developed the freons which were neither toxic nor inflammable and continued to be used until the 1990s.

In the early 1920s the industry grew considerably, with some other manufacturers using absorption of ammonia in water instead of liquifying a gas through compression to achieve the phase change. However, these were not very successful, largely because of public predujice against ammonia as a refrigerant. Today they are used in homes that are not connected to the electric grid, and in recreational vehicles because they can be efficiently powered using a heat source rather than an electric motor.

See also: microwave refrigerator combo, side-by-side, ice and water dispenser, ice cube tray, larder, defrost (manual, frost free), chiller, reversible door, compressor, thermostat, drawers, thaw, shelves, rack (for eggs, bottles,...) , spill proof, star rating, noise (dB(A)), fuzzy logic, stainless steel, bisque, timer, LED .

External links

• History of the Refrigerator - Gizmohighway Technology Guide (http://www.gizmohighway.com/history/refrigerator.htm)
• How Refrigerators Work (http://www.repairclinic.com/0088_4_3.asp) Article by RepairClinic
• How Refrigerators Work (http://home.howstuffworks.com/refrigerator.htm) Article by HowStuffWorks
• http://inventors.about.com/library/inventors/blrefrigerator.htm
• [1] (http://www.subzero.com/subzero/subzhistory.asp) Article by Sub-Zero on the History of the Refrigerator

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Freezer is also Japanese name for Articuno, a Pokémon