第2篇 冷冻运输的历史 History of Refrigeration

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History of Refrigeration

A

The term refrigeration refers to cooling an area or substance below the environmental temperature, the process of removing heat. Mechanical refrigeration uses the evaporation of a liquid refrigerant to absorb heat. The refrigerant goes through a cycle so that it can be reused, the main cycles are; vapour-compression, absorption, steam-jet or steam-ejector, and air. Maryland farmer Thomas Moore first introduced the term Refrigerator in 1803, the appliance we know today first appeared in the 20th century.

B

Prior to mechanical refrigeration systems, people found different ways of preserving their food. Some people preferred to use cooling systems of ice or snow found either locally or brought down from mountains and sometimes stored in cellars. Using those techniques meant that diets would have consisted of very little fresh food or fruits and vegetables, but mostly of bread, cheese and salted meats. Milk and cheeses were difficult to keep fresh, they were usually stored in a cellar or window box, but despite those methods, they could not prevent rapid spoilage. People were more than ready for a better system of preserving food.Later on, it was discovered that adding chemicals like sodium nitrate or potassium nitrate to water caused the temperature to fall. Cooling wine with this technique was first recorded in 1550, as was the term “to refrigerate”. Cooling drinks became very popular by 1600 in Europe, especially in Spain, Italy and France. Instead of cooling water at night, people used a new technique; rotating long necked bottles in water which held dissolved saltpeter. The solution was used to create very low temperatures and even to make ice. By the end of the 17th century, iced drinks including frozen juices and liquors were very popular in French society.

C

A demand for ice soon became very strong. Consumer demand for fresh food, especially produce, led to diet reform between 1830 and the Civil War, fueled by the dramatic growth of cities and the improvement in economic status of the general populace. And as cities grew, so did the distance between the consumer and the source of the food. In 1799, ice was first shipped commercially out of Canal Street in New York City to Charleston, South Carolina. The attempt was a failure as there was very little ice left when the shipment arrived. Frederick Tudor and Nathaniel Wyeth of New England saw the great potential that existed for the ice business and revolutionized the industry with their efforts in the first half of the 1800s. Tudor, who was known as the “Ice King”, was more focused on shipping ice to tropical climates. To ensure his product would arrive safely, he experimented with different insulating materials and built icehouses that decreased melting losses from 66 percent to less than 8 percent. Wyeth developed a method of cheaply and quickly cutting uniform blocks of ice that transformed the ice industry. He made speed handling techniques in storage, transportation and distribution possible, with less waste.

D

Eventually it became clear that the ice being scraped was not all clean and was causing health problems. It was becoming an increasingly difficult task to find clean sources of natural ice and by the 1890’s, pollution and sewage dumping had made the job seem even more impossible. The first signs were noticed in the brewing industry, and then the meat packing and dairy industries became seriously affected. Some sort of clean, mechanical refrigeration was desperately needed.

E

Many inventive men were involved in the eventual creation of the refrigerator, through different discoveries that each built on the next. Dr. William Cullen, a Scotsman, was the first to study the evaporation of liquids in a vacuum in 1720. He later demonstrated the first known artificial refrigeration at the University of Glasgow in 1748 by letting ethyl ether boil into a partial vacuum. Olvier Evans, an American inventor, designed the first refrigeration machine to use vapor instead of liquid in 1805. Although he did not actually build it, an American physician named John Gorrie, produced one very similar to Evans’ in 1842 to cool the patients with yellow fever in a Florida hospital. His basic principle is still the most often used in refrigerators today. He found the best way to cool the air was by compressing a gas, then cooling it by sending it through radiating coils, and then expanding it to lower the temperature even more. Evans was granted the first U.S. patent for mechanical refrigeration in 1851 after giving up his medical practice to focus on his experimentation with ice making. In 1820 Michael Faraday, a Londoner, first liquefied ammonia to cause cooling. Ferdinand Carre of France developed the first ammonia/water refrigeration machine in 1859. Carl von Linde was also very influential in the creation of refrigeration. In 1873 he designed the first practical and portable compressor refrigeration machine in Munich and in 1876 he began using an ammonia cycle rather than the methyl ether he used in his earlier models. Linde later developed a new method (Linde technique) for the liquefaction of large quantities of air in 1894. The meat packing industry in Chicago was the next to adopt mechanical refrigeration nearly a decade later.

F

Beginning in the 1840s, refrigerated cars were used to transport milk and butter. By 1860, refrigerated transport was limited to mostly seafood and dairy products. The refrigerated railroad car was patented by J.B. Sutherland of Detroit, Michigan in 1867. He designed an insulated car with ice bunkers in each end. Air came in on the top, passed through the bunkers, and circulated through the car by gravity, controlled by the use of hanging flaps that created differences in air temperature. There were different car designs based upon the type of cargo, whether meat or fruit. The first refrigerated car to carry fresh fruit was built in 1867 by Parker Earle of Illinois, who shipped strawberries on the Illinois Central Railroad. Each chest contained 100 pounds of ice and 200 quarts of strawberries. It wasn until 1949 that a refrigeration system made its way into the trucking industry by way of a roof-mounted cooling device, patented by Fred Jones.

G

Refrigerators that were built in the late 1800s to 1929 used the toxic gases; methyl chloride, ammonia and sulphur dioxide as refrigerants. There were numerous fatal accidents that occurred in the 1920s when methyl chloride leaked out of refrigerators. After the terrible incidents, three American companies began researching less dangerous methods of refrigeration. Frigidaire discovered a new class of synthetic refrigerants called halocarbons or CFCs (chlorofluorocarbons) in 1928. That research lead to the discovery of chlorofluorocarbons (Freon), which quickly became the standard used in compressor refrigerators. Freon was safer for those nearby but was later discovered in 1973 by Prof. James Lovelock, to be harmful to the ozone layer. To prevent further damage, new developments were made, such as Hydroflourocarbons which have no known effect on the ozone layer. Chlorofluorocarbons (CFS) are no longer used; they are outlawed in several places, making refrigeration far safer today than it has ever been.

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