Refrigeration, fridges, freezers – It’s history
The topic of discussion is on the history of refrigeration. Below is an article based on the history of refrigeration.
A Brief History Of Refrigeration
The manufacturing process
The History of refrigeration is an interesting topic.
Prior to the development of artificial refrigeration techniques during the 1800s, people utilized a variety of means to chill and preserve foodstuffs.
For centuries, ice served as the principal refrigerant. Ironically, the ancient Indians and Egyptians pioneered an ice-making technique that served as the conceptual basis for the first “modern” refrigerators developed during the nineteenth century: evaporation. The relatively quick evaporation of a liquid creates an expanding volume of gas.
As water vapor rises, its kinetic energy increases dramatically, in part because the warm vapor is drawing in energy from its surroundings, which are cooled by this process. The Indians and Egyptians took advantage of this phenomenon by placing wide, shallow bowls filled with water outside during the cool nights. As some water quickly evaporated, the remaining water cooled, forming ice.
With this method, it was possible to create sizeable chunks of ice that could then be used to cool food.
What Developed Next
Using a more primitive means of procuring ice, the ancient Chinese simply transported it from the mountains to cool their food; later, the Greeks and Romans adopted this practice.
To preserve the ice itself, people stored it in pits or caves insulated with straw and wood, by which means they could maintain a supply of ice for months. In industrialized nations, ice served as the primary method of chilling food through the nineteenth century, when people inserted blocks of ice in insulated cabinets alongside the food they wished to store.
Even today, in many developing nations ice remains the sole available refrigerant.
A More Modern Approach
The first known attempt to develop an artificial refrigerator took place in Scotland at the University of Glasgow.
There, in 1748, William Cullen revived the ancient Indian-Egyptian practice of freezing liquid by means of evaporation, although he accelerated the process by boiling ethyl ether into a partial vacuum (ethyl evaporates more quickly than water).
Cullen attempted this merely as an experiment, as did American Oliver Evans, who designed another refrigerator in 1805. Evans’s machine, based on a closed cycle of compressed ether, represented the first effort to use simple vapor instead of vaporizing a liquid.
While Evans never developed his machine beyond the prototype stage, in 1844 an American doctor named John Gorrie actually built a very similar machine to provide ice for the hospital in which he worked. Gorrie’s machine compressed air that was next cooled with water.
The cooled air was then routed into an engine cylinder, and, as it re-expanded, its temperature dropped enough so that ice could be made.
In 1856 another American, Alexander Twinning, began selling a refrigeration machine based on the same vapor-compression principle, and soon after that Australian James Harrison enlarged the American design (meant to be used in individual homes) for the meat-packing and beer-making industries. Three years later, Ferdinand Carre refined the basic concept underlying all of these refrigerators when he introduced ammonia as a coolant.
Ammonia represented an advance because it expands more rapidly than water and can thus absorb more heat from its environs. Carre also contributed other innovations. His refrigerator operated by means of a cycle in which a refrigerant vapor (ammonia) was absorbed in a liquid (a mixture of ammonia and water) that was subsequently heated.
The heat caused the refrigerant to vaporize, thereby creating a cooling effect (after it vaporized, the refrigerant was condensed so that it could once again be absorbed in the liquid, repeating the cycle). Carre’s machine not only sold extremely well, it also inaugurated modern refrigeration by upgrading Evans’s compression concept and adding a more sophisticated refrigerant. These components remain the basis of most refrigerators used today.
What Happened To Ammonia
Ammonia itself posed several problems, however. While it served as a very effective coolant, it was both odiferous and poisonous when it leaked, and it quickly disappeared from refrigeration after synthetic alternatives were developed during the 1920s.
The best known of these, patented by Du Pont under the name freon, was created by chemically altering the methane molecule, substituting two chlorine and two fluorine atoms for its four hydrogen atoms. The resulting gas (technically, dichlorofluoromethane) was hailed because its low boiling point, surface tension, and viscosity rendered it an ideal—and ostensibly problem-free—refrigerant.
Later, in the 1970s, scientists realized that freon posed problems of its own related to the environment and began searching for new agents to use in refrigeration.