Mechanical Energy Balance: Summary

The answers to the ConcepTests are given below and will open in a separate window. 
Key points from this module:
  • The mechanical energy balance assumes an incompressible fluid and steady-state flow.
  • An increase in fluid velocity corresponds to a decrease in the sum of the static pressure, potential energy and internal energy.
  • For a fluid flowing horizontally, when the velocity increases, the pressure decreases.
  • The Bernoulli equation is used when the there are no frictional losses and no shaft work.
  • A Pitot tube can be used to measure fluid velocity by using the Bernoulli equation.
From studying this module, you should now be able to:
  • Apply Bernoulli’s equations to determine flow rates.
  • Know where to apply Bernoulli’s Equation in a system.
  • Make assumptions based on the physical nature of the problem.
  • Use Bernoulli’s equation to find velocity, pressure, and/or height at any point in the system.
  • Use the continuity equation in conjunction with Bernoulli’s equation to relate two velocities.
Additional Source:

Bernoulli Pressure Lowering – Visual representation of pressure drop due constriction in a tube- friction is also taken into account.

Prepared by John L. Falconer, Department of Chemical and Biological Engineering, University of Colorado Boulder