tailieunhanh - Know and Understand Centrifugal Pumps Episode 4

Tham khảo tài liệu 'know and understand centrifugal pumps episode 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Useful Work and Pump Efficiency Useful work from a pump The physicist James Watt is honored in the electrical community for the term watt . He made various advancements and improvements to stationary boilers and steam engines. It is said that the first practical use of the steam engine was in raising call it pumping water out of the coalmines. Almost all mines would flood if the water were not pumped from the bilge out of the mine. Before the steam engine the miners used children and horses to lift and carry the bilge water. James Watt developed the terms of energy work and power. He defined the following Energy is the capacity to perform work. Example I have the energy in my bicep muscle to lift a 100-pound weight. Work is a force multiplied over a distance. Example If I lift a 5-pound weight one foot into the air then I ve performed 5 footpounds of work. Power is work performed within a certain specified time frame. Power is when I perform 5 foot-pounds of work within a second or minute. Many people confuse these terms but they actually have precise definitions. If I should lift 10 pounds a distance of 10 feet then I ve performed 100-foot-pounds of work 10 pounds X 10 feet 100 . Before the steam engine the most powerful force to perform work or exert a force was a horse. James Watt with actual tests determined that a coal mine draft horse could lift 550 pounds a distance of one foot within a second. So James Watt declared 550 foot-lbs sec. to be one Horsepower. To this day this has become the standard definition of a horsepower 1 HP 44 Useful Work and Pump Efficiency 10 Feet Figure 5-1 550 . sec. . This is the reason that even today all motors whether steam internal combustion engines boilers electric motors gas turbines and even jet and rocket engines are rated in Horsepower and not Ostrich power or Iguana power. We say that the motor generates horsepower HP and that the pump consumes brake horsepower BHp . The difference between HP output and BHp input .