|
A centrifugal fan is a mechanical device for moving air or other gases. The terms "blower" and "squirrel cage fan" (because it looks like a hamster wheel) are frequently used as synonyms. These fans increase the speed of air stream with the rotating impellers. They use the kinetic energy of the impellers or the rotating blade to increase the pressure of the air/gas stream which in turn moves them against the resistance caused by ducts, dampers and other components. Centrifugal fans accelerate air radially, changing the direction (typically by 90°) of the airflow. They are sturdy, quiet, reliable, and capable of operating over a wide range of conditions. Centrifugal fans are constant displacement devices or constant volume devices, meaning that, at a constant fan speed, a centrifugal fan will pump a constant volume of air rather than a constant mass. This means that the air velocity in a system is fixed even though the mass flow rate through the fan is not. Centrifugal fans are not positive displacement devices. Centrifugal fans have certain advantages and disadvantages when contrasted with positive-displacement blowers.〔 United Nations Environment Programme. ("Fans and Blowers" ). 2006. p. 9. quote: "The centrifugal blower and the positive displacement blower are two main types of blowers" 〕〔 ("Advantages of Rotary Positive Displacement Blowers Versus Centrifugal Blowers" ). 1996. 〕〔 Juan Loera, P.E. ("Overview of Blower Technologies" ). p. 10. 〕〔 Jim Brown. ("The Great Debate: Centrifugal Fan vs. Positive Displacement Pump" ). 2008. 〕〔 Vac2Go. ("What’s better, a PD or Fan Combination Unit?" ). 2013. 〕 The centrifugal fan is one of the most widely used fans. Centrifugal fans are by far the most prevalent type of fan used in the HVAC industry today. They are usually cheaper than axial fans and simpler in construction.〔(【引用サイトリンク】url=http://www.energystar.gov/index.cfm?c=business.EPA_BUM_CH8_AirDistSystems#SS_8_3_1 )〕 It is used in transporting gas or materials and in ventilation system for buildings. They are also used commonly in central heating/cooling systems. They are also well-suited for industrial processes and air pollution control systems. It has a fan wheel composed of a number of fan blades, or ribs, mounted around a hub. As shown in the animated figure, the hub turns on a driveshaft that passes through the fan housing. The gas enters from the side of the fan wheel, turns 90 degrees and accelerates due to centrifugal force as it flows over the fan blades and exits the fan housing.〔(Fan types ) (U.S. Environmental Protection Agency website page)〕 == History == The centrifugal fan was invented by Russian military engineer Alexander Sablukov in 1832, and found its usage both in the Russian light industry (such as sugar making) and abroad.〔(A History of Mechanical Fan ) 〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「centrifugal fan」の詳細全文を読む スポンサード リンク
|