Conversion of Kinetic Energy to Pressure Energy

The key idea is that the energy created by the centrifugal force is kinetic energy.
The amount of energy given to the liquid is proportional to the velocity at the edge or
vane tip of the impeller. The faster the impeller revolves or the bigger the impeller is,
then the higher will be the velocity of the liquid at the vane tip and the greater the energy
imparted to the liquid.
This kinetic energy of a liquid coming out of an impeller is harnessed by creating
a resistance to the flow. The first resistance is created by the pump volute (casing) that
catches the liquid and slows it down. In the discharge nozzle, the liquid further
decelerates and its velocity is converted to pressure according to Bernoulli’s principle.
Therefore, the head (pressure in terms of height of liquid) developed is
approximately equal to the velocity energy at the periphery of the impeller expressed by
the following well-known formula:

This head can also be calculated from the readings on the pressure gauges
attached to the suction and discharge lines.
Pump curves relate flow rate and pressure (head)
developed by the pump at different impeller sizes
and rotational speeds. The centrifugal pump
operation should conform to the pump curves
supplied by the manufacturer. In order to read
and understand the pump curves, it is very
important to develop a clear understanding of the
terms used in the curves. This topic will be
covered later.