History
Civilizations throughout the ages have found ingenious ways to combat the heat in their region. An earlier form of air cooling, the windcatcher (Bâd gir), was invented in Persia (Iran) thousands of years ago in the form of wind shafts on the roof, which caught the wind, passed it over subterranean water in a qanat and discharged the cooled air into the building. Nowadays Iranians have changed the windcatcher into an evaporative cooler (Coolere Âbi) and use it widely. There are 9 million evaporative coolers in central Iran, and in just the first two months of year 1385 in the Persian/Iranian calendar (April–May 2006) 130,000 evaporative coolers were sold in Iran.
The evaporative cooler was the subject of numerous US patents in the 20th century; many of these, starting in 1906, suggested or assumed the use of excelsior (wood wool) pads as the elements to bring a large volume of water in contact with moving air to allow evaporation to occur. A typical design, as shown in a 1945 patent, includes a water reservoir (usually with level controlled by a float valve), a pump to circulate water over the excelsior pads and a squirrel-cage fan to draw air through the pads and into the house. This design and this material remain dominant in evaporative coolers in the American Southwest, where they are also used to increase humidity. In the United States, the use of the term swamp cooler may be due to the odor of algae produced by early units.
Evaporative cooling was in vogue for aircraft engines in the 1930s, for example with the Beardmore Tornado airship engine. Here the system was used to reduce, or eliminate completely, the radiator which would otherwise create considerable drag. In these systems the water in the engine was kept under pressure with pumps, allowing it to heat to temperatures above 100°C, as the actual boiling point is a function of the pressure. The superheated water was then sprayed through a nozzle into an open tube, where it flashed into steam, releasing its heat. The tubes could be placed under the skin of the aircraft, resulting in a zero-drag cooling system.
However these systems also had serious disadvantages. Since the amount of tubing needed to cool the water was large, the cooling system covered a significant portion of the plane even though it was hidden. This added complexity and reliability issues. In addition this large size meant it was very easy for it to be hit by enemy fire, and practically impossible to armor. British and U.S. developers used ethylene glycol instead, cooling the liquid in radiators. The Germans instead used streamlining and positioning of traditional radiators. Even the method's most ardent supporters, Heinkel's Günter brothers, eventually gave up on it in 1940.
Externally-mounted evaporative cooling devices to cool interior air were used in some automobiles, often as aftermarket accessories, until modern vapor-compression air conditioning became widely available.
Read more about this topic: Evaporative Cooler
Famous quotes containing the word history:
“The myth of independence from the mother is abandoned in mid- life as women learn new routes around the mother—both the mother without and the mother within. A mid-life daughter may reengage with a mother or put new controls on care and set limits to love. But whatever she does, her child’s history is never finished.”
—Terri Apter (20th century)
“There is one great fact, characteristic of this our nineteenth century, a fact which no party dares deny. On the one hand, there have started into life industrial and scientific forces which no epoch of former human history had ever suspected. On the other hand, there exist symptoms of decay, far surpassing the horrors recorded of the latter times of the Roman empire. In our days everything seems pregnant with its contrary.”
—Karl Marx (1818–1883)
“When we of the so-called better classes are scared as men were never scared in history at material ugliness and hardship; when we put off marriage until our house can be artistic, and quake at the thought of having a child without a bank-account and doomed to manual labor, it is time for thinking men to protest against so unmanly and irreligious a state of opinion.”
—William James (1842–1910)