In a hydraulic system, what energy forms does the impeller convert rotational energy into to raise the fluid’s energy?

• A. Kinetic energy and potential energy.
• B. Head energy and flow energy.
• C. Thermal energy and chemical energy.
• D. Electrical energy.

Answer: (B)

Rotating the impeller injects mechanical energy into the fluid, raising its hydraulic energy. This energy shows up as head energy, which accounts for pressure (and elevation) energy per unit weight, and as flow energy, which is the fluid’s kinetic energy from its velocity. In a pump, the impeller increases both the pressure and the speed of the fluid, so the two relevant forms are head energy and flow energy. Thermal, chemical, or electrical energies aren’t the forms the fluid gains from the impeller in a hydraulic system, and while velocity and elevation are parts of the energy picture, hydraulic practice describes them together as head energy and flow energy.