Refrigerator/ AC
NAME: Refrigerator
ALTERNATIVE NAME/S: icebox, fridge
Benjamin Franklin “ noted a principle of refrigeration by observing that on a very hot day, he stayed cooler in a wet shirt in a breeze than he did in a dry one. To understand this phenomenon more clearly, he conducted experiments. In 1758 on a warm day in Cambridge, England, he and fellow scientist John Hadley experimented by continually wetting the ball of a mercury thermometer with ether and using bellows to evaporate the ether.[187] With each subsequent evaporation, the thermometer read a lower temperature, eventually reaching 7 °F (−14 °C). Another thermometer showed that the room temperature was constant at 65 °F (18 °C). In his letter Cooling by Evaporation, Franklin noted that, "One may see the possibility of freezing a man to death on a warm summer's day."[188] According to Michael Faraday, Franklin's experiments on the non-conduction of ice are worth mentioning, although the law of the general effect of liquefaction on electrolytes is not attributed to Franklin....”
The first practical refrigerator was developed by Von Linde*, in Munich, Germany, when he was looking for ways to allow the local brewers to brew beer safely in the summer heat.
The principle behind every refrigerator is that when a gas (called the refrigerant) is compressed it becomes liquid. When its pressure is then decreased it vaporizes and draws heat from its immediate surroundings, which then become colder. This principle had been shown in 1748 in Glasgow, Scotland by Dr William Cullen* and used again in 1844, in Apalachicola, Florida, by Dr John Gorrie*.
In a modern fridge, the refrigerant is a gas that vaporizes at an extremely low temperature (in the case of ammonia: –27F). This gas is squeezed by a compressor and heats up (the heat is dissipated by the coils on the back of the outside of refrigerator). The compressed gas then cools down and condenses into a liquid. When the liquid is released through an expansion valve, it is sent through another set of coils, inside the refrigerator. The released liquid immediately warms up (to –27F) and vaporizes, drawing heat from the coils and their surroundings. This makes the coils and their immediate surroundings extremely cold, and a fan blows the supercold air through the refrigerator interior, cooling the content down. The refrigerant vapor in the coils returns to the compressor and is compressed into liquid again.
ONELINER: The refrigerator, the coolest invention
OTHER CONNECTIONS: Refrigerated railcars and ships allowed meat, dairy and produce to be moved quickly hundreds of miles, resulting in cowboy cattle drives and radically altering the diet of city folk. CFC’s were banned in the Montreal Protocol treaty, which has led to a recovery of the earth’s protective ozone layer.
BIBLIOGRAPHY:
Encyclopedia Britannica
www.howstuffworks.com
How We Got To Now: AC migration to Sun Belt leads to election of President Reagan
See Air Conditioning