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*vel ocity Angular momentum=radius*ma ss*velocity Torque=time rate of change of angular momentum

© The University of Texas at El Paso PUMPING ENERGY Power=  Qh pump = Q (P 2 -P 1 ) The mechanical horsepower, also known as imperial horsepower, of exactly 550 foot-pounds per second is approximately equivalent to watts.foot-pounds

© The University of Texas at El Paso Types of Pumps Propeller, used for low head ( 20L/s)

© The University of Texas at El Paso Multistage propeller Used in deep wells with high head and low flow 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

© The University of Texas at El Paso 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

Pump Tips gal-pump-tips.htmhttp:// gal-pump-tips.htm

© The University of Texas at El Paso Pump Fundamentals

© 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!) H pump =z 2 -z 1 +h loss This is the system curve for our simple system shown below

© The University of Texas at El Paso Solution where curves intersect

© The University of Texas at El Paso Pumps in Parallel – Add Discharge

© The University of Texas at El Paso 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.