G azərbaycan respublikasi təHSİl naziRLİYİ azərbaycan texniKİ universiteti M. M. QƏNDİLova e. Q. İsmayilova

JOKES, LAUGHS, SMILES
Luck
An unhappy student of a foreign language said: “Speaking a foreign language is a matter of luck – sometimes you’re lucky to say something correct.”

UNIT XX

He that climbs a ladder must begin

at the first round

Scott, Walter

AIR CONDITIONING AND REFRIGERATION
The mechanical refrigeration industry dates back to the time of the American Civil War. But, the machines then designed were not very important commercially for many years. It was at the end of the nineteenth century that the first ice-making machine started commercial production using ammonia as a refrigerant. Ammonia was for many years the most widely used liquid refrigerant and indeed, is still used today in quite a few specialized applications. However, after many years work chemists developed the boiling-point fluids now in wide use in nearly all refrigeration and air-conditioning systems: non – toxic, non- flammable and non-corrosive.

The first use of mechanical refrigeration for ice-making purposes and cooling of large meat holding rooms and other big warehouses was at the beginning of the twentieth century. The artificial ice made by ice plants in towns and cities began to supplant natural ice. In the 1920s a major breakthrough took place with the development of the domestic refrigerator. At the same time, larger and more specialized equipment was being developed for chilling applications in industry and commerce.

The idea of adapting the refrigeration cycle to creating artificial “climate” for industrial purposes seems to have occurred to a number of industrialists and refrigeration engineers soon after the turn of the century.

In the 1920s air-conditioning for comfort was first used when the motion picture industry was building theatres in the United States. While a few residences were air-conditioned prior to World War II home air –conditioning did not really start growing until some ten years after the war. The early residential air-conditioners were expensive and installed only in the most expensive houses.

Today, the number of centrally air-conditioned (cooled and heated) homes is growing day by day. In addition to it, there exist window-type air-conditioners and split-type air-conditioners which are used for air-conditioning of one or more rooms and confined spaces. Most of the schools, universities, hospitals and public buildings have been air-conditioned today because air-conditioners and refrigerators have become an integral part of the daily life of population of the world.

Aside from the creation of comfort conditions, air-conditioning cuts the costs of products and steps up production. Most of the food that reaches our tables depends on refrigeration, from producer to consumer. Refrigerated trucks and trains, warehouses and food processing plants, etc. serve for better organization of food service and its transportation and storage. Refrigeration plays a decisive part in medicine and surgery. Refrigerated storage cabinets keep blood and living parts of the human body in “ banks” to be used in surgery.

In addition to these there are newly developed and still to be developed applications of refrigeration. Astronauts have to be protected from the heat generated by their passage through the atmosphere at take-off or landing. This is achieved by special refrigeration equipment developed for this purpose.