CE 230-Engineering Fluid Mechanics

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CE 230-Engineering Fluid Mechanics
Lecture 25-27 ENERGY EQUATION
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Bernoulli Equation did not account for 1) Energy
loss due to viscous resistance 2) Energy that can
be add to the system through a device 3) Energy
that can be taken from the system through a
device These are some of the limitations of
BE Instead we will use an equation that takes
care of all these This is the Energy Equation
for1-D, steady, incompressible flow
1 for uniform v Close to 1 turbulant Close to 2
laminar
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Find K.E. correction factor for flow in a
circular pipe if the velocity is given by
Recall
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We must calculate V
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Example 7.3
Compare your results with results obtained using
BE)
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Example 7.4
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Example 7.5
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Concept of EGL HGL

• The total head (energy/unit weight) can be split
  into three components
• 1) Elevation head
• 2) Pressure head
• 3) Velocity head
• To see the variation of the flow energy we may
  draw a line called EGL

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EGL and HGL in a straight pipe
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Influence of pump on HGL and HGL
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Influence of size change on HGL and EGL
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Influence of size change on HGL and EGL
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What if pipe was not horizontal ?