Energy Conservation (Bernoulli’s Equation)

Energy conservation(cont.)

Example: Determine the efficiency of the pump if the power input of the motor

is measured to be 1.5 hp. It is known that the pump delivers 300 gal/min of water.

Mercury (gm=844.9 lb/ft3)

water (gw=62.4 lb/ft3)

1 hp=550 lb-ft/s

No turbine work and frictional losses, hence: hE=hL=0. Also z1=z2

6-in dia. pipe

4-in dia.pipe

Given: Q=300 gal/min=0.667 ft3/s=AV

ÞV1= Q/A1=3.33 ft/s V2=Q/A2=7.54 ft/s

pump

Z=15 in

If energy is added, removed or lost via pumps turbines, friction, etc.then we use

Extended Bernoulli’s Equation

Looking at the pressure term: