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Pump Selection. Chapter 5. Think of a sprinkler head, except you turn the sprinkler to move the water rather then the other way around. Centrifugal Pump Concept. Principle of angular momentum conservation Momentum=mass*velocity Angular momentum=radius*mass*velocity - PowerPoint PPT Presentation
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Chapter 5
© The University of Texas at El Paso
Centrifugal Pump Concept
Think of a sprinkler head, except you turn the sprinkler to move the water rather then the other way around
© The University of Texas at El Paso
• Principle of angular momentum conservation
• Momentum=mass*velocity
• Angular momentum=radius*mass*velocity
• Torque=time rate of change of angular momentum
© The University of Texas at El Paso
PUMPING ENERGY• Power=Qhpump
• = Q (P2-P1)
• The mechanical horsepower, also known as imperial horsepower, of exactly 550 foot-pounds per second is approximately equivalent to 745.7 watts.
© The University of Texas at El Paso
Types of Pumps• Propeller, used for
low head (<12 m), high capacity (>20L/s)
© The University of Texas at El Paso
Multistage propeller
• Used in deep wellswith high head and lowflow rate
© The University of Texas at El Paso
Jet Pumps
• Take energy from high pressure fluid
• No moving parts• Compact and light
but not efficient• Q1 is high pressure
fluid• Q2 is fluid to be
pumped
© The University of Texas at El Paso
Positive Displacement Pumps
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Positive Displacement Pump
• Very high head, low flow
© The University of Texas at El Paso
How to size a pump
• To find operating point:• obtain pump curve from manufacturer, pumps
pump less water at higher heads• calculate the system curve, the system curve is
an equation that tells how much water flows through a pipe system as a function of the head (energy per unit weight) added by the pump.
• • Energy efficiency is maximized when the
operation point (intersection of pump and system curves) is at the point of maximum pump efficiency
© The University of Texas at El Paso
Cavitation is Evil
• Cavitation can occur whenever the absolute pressure locally gets below the vapor pressure of the water
• Frequent issue when pump is higher than water reservoir but can occur with any pump
• Common site of cavitation is near tips of impellor vanes where velocity is high
© The University of Texas at El Paso
Pump Selection
© The University of Texas at El Paso
© The University of Texas at El Paso
Pump Tips
• http://www.pumpfundamentals.com/centrifugal-pump-tips.htm
© The University of Texas at El Paso
Pump Fundamentals
• http://www.pumpfundamentals.com/tutorial2.htm#pump-pressure
• http://www.pumpworld.com/Capacity.htm
© The University of Texas at El Paso
How to size a pump
• To find operating point:• obtain pump curve from manufacturer, pumps
pump less water at higher heads• calculate the system curve, the system curve is
an equation that tells how much water flows through a pipe system as a function of the head (energy per unit weight) added by the pump.
• • Energy efficiency is maximized when the
operation point (intersection of pump and system curves) is at the point of maximum pump efficiency
© The University of Texas at El Paso
Explain Pump Curve
System curve
Brake horsepower (bhp) is the measure of an engine's horsepower before the loss in power caused by the gearbox, alternator, differential, water pump, and other auxiliary components
© The University of Texas at El Paso
How to size a pump
• To find operating point:• obtain pump curve from manufacturer, pumps
pump less water at higher heads• calculate the system curve, the system curve is
an equation that tells how much water flows through a pipe system as a function of the head (energy per unit weight) added by the pump.
• • Energy efficiency is maximized when the
operation point (intersection of pump and system curves) is at the point of maximum pump efficiency
© The University of Texas at El Paso
Example System
• Show using Bernoulli Equation (good quiz!)
• Hpump=z2-z1+hloss
• This is the system curve for our simple system shown below
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Solution where curves intersect
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Pumps in Parallel – Add Discharge
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Pumps in Series – Add Head
© The University of Texas at El Paso
The solid lines are labeled; the dashed line is the system curve. If we change the pump rpm (revolutions per minute), from 3250 to 4350, how much more water do we pump and how does the power input change? Show your work by drawing on the figure.
