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Refrigerator

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A refrigerator is a vital household and commercial appliance designed to preserve food.

Fridgeinterior
Fridgeinterior

It consists of a thermally insulated compartment and a heat pump. This heat pump can be mechanical, electronic, or chemical in nature. The machine works by transferring heat from the inside of the compartment to the external environment. This process cools the interior to a temperature below the ambient temperature of the room. This cooling is essential because low temperatures reduce the reproduction rate of bacteria. By slowing bacteria, the refrigerator lowers the overall rate of food spoilage.

Most modern refrigerators operate using a vapor compression cycle.

Refrigerator-cycle
Refrigerator-cycle

This process functions as a continuous loop to move heat. A refrigerant, which is a special substance, moves through the system to absorb heat from the interior. The machine then carries that heat to the outside of the unit. This technology is the same basic principle used in many air conditioning systems.

Newer models may include additional features like automatic defrosting or ice dispensers. Some very small versions, called Peltier-type refrigerators, are designed specifically to chill beverages.

There are different types of cooling compartments used for various purposes. A standard refrigerator maintains a temperature a few degrees above the freezing point of water. The United States Food and Drug Administration recommends keeping this temperature at 40°F or below. A freezer is a specialized part of a refrigerator that stays below the freezing point.

Open refrigerator with food at night
Open refrigerator with food at night

The FDA recommends that freezers be regulated at 0°F. While refrigerators keep food fresh, freezers allow people to store perishable food in bulk for later use. Some modern designs use a side-by-side style, while the freezer-over-refrigerator style was the standard from the 1940s onward.

Humans have used various methods to achieve cooling throughout history. Ancient Iranians used complexes called yakhchāls to store things coolly. These used subterranean spaces and wind-catchers called badgirs. Before electricity, people relied on icehouses and iceboxes. These were often filled with snow or ice collected from freshwater lakes. In 1755, Scottish professor William Cullen created a small refrigerating machine. He used a pump to create a vacuum over diethyl ether. This caused the ether to boil and absorb heat from the air. Although it created a small amount of ice, it had no practical use at that time.

Many inventors contributed to the development of artificial refrigeration. In 1834, Jacob Perkins built the first working vapor-compression system. Later, James Harrison built a practical mechanical ice-making machine in 1851. He received a patent for his system in 1856. In 1876, Carl von Linde patented an improved method for liquefying gases. This made the first reliable and efficient compressed-ammonia refrigerator.

Linde cycle 1895 -1903 patent cryo
Linde cycle 1895 -1903 patent cryo

His work allowed for the use of refrigerants like ammonia, sulfur dioxide, and methyl chloride. These gases were widely used until the late 1920s, though they raised safety concerns.

The transition to home electric refrigerators happened in stages. In 1913, Fred W. Wolf invented the first electric refrigerators for domestic use. His model, called DOMELRE, was mounted on top of an existing ice box.

DOMELRE refrigerator c. 1914
DOMELRE refrigerator c. 1914

Later, in 1923, Frigidaire introduced the first self-contained unit. The General Electric "Monitor-Top" refrigerator, released in 1927, became very popular.

Monitor refer
Monitor refer

It was named for its resemblance to a warship turret. Over a million of these units were produced. However, they used substances like sulfur dioxide or methyl formate, which could be toxic or flammable.

Safety and environmental science eventually changed how refrigerators are made. The introduction of Freon in the 1920s made refrigerators much safer for homes. Freon was a low-toxicity alternative to older, dangerous gases. However, Freon-12 was later found to damage the ozone layer. In 1994, governments issued a ban on its use. Today, R-134a is a common replacement, though R-12 is still found in older systems. Modern refrigeration remains a major consumer of energy. In supermarkets, refrigeration can consume up to 50% of the total energy used. Using glass doors on display cases can improve efficiency compared to open cases.

Energy label 2010
Energy label 2010
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🖼️ Images & Media (17)
File:Open refrigerator with food at night.jpg
Open refrigerator with food at night.jpg
Theater commercial, electric...
File:Linde cycle 1895 -1903 patent cryo.jpg
Linde cycle 1895 -1903 patent cryo.jpg
File:French Refrigerator Plant Increases its Productivity - DPLA - 95f3ac5808bd87d40bb4379003218b75.jpg
French Refrigerator Plant Increases its...
File:Röck istván 1896.jpg
Röck istván 1896.jpg
File:DOMELRE refrigerator c. 1914.png
DOMELRE refrigerator c. 1914.png
File:Monitor refer.jpg
Monitor refer.jpg
File:Refrigerator Cycle.svg
Refrigerator Cycle.svg
Introduction to the Process and...
File:Refrigerator-cycle.svg
Refrigerator-cycle.svg
File:Refrigeration comp and coil.jpg
Refrigeration comp and coil.jpg
File:Fridgeinterior.jpg
Fridgeinterior.jpg

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