Editorial: Is there a Difference between Centrifugal and Rotodynamic Pumps?

Pumps are often labelled as either Centrifugal or Positive Displacement, but you have probably heard of rotodynamic pumps which is often incorrectly interchanged with the word centrifugal pumps. So, is there a difference between rotodynamic pump and Centrifugal pumps?
Editorial: Is there a Difference between Centrifugal and Rotodynamic Pumps?

Is there a difference between Centrifugal & Rotodynamic pumps? (Image source: Crest Pumps)

The short answer is yes, there is a marked difference, but lets explore further.

Rotodynamic pumps include a rotation part (such as an impeller, rotor or propeller) that imparts mechanical energy on a fluid, so increasing the kinetic energy of the fluid that is then converted to potential energy (pressure) in the pump casing. There are generally three types of impeller / rotor / propeller and the following illustrates the differences and direction of flow of each type.

Figure (a) shows that the fluid is taken in through the impeller eye and accelerated at an angle of 90 degrees (radially). This is a radial or centrifugal impeller.
Figure (b) shows the fluid taken from the eye and accelerated at an angle, so this is a mixed flow pump.
Figure (c) shows the liquid being accelerated along the pipe, or axially, so this is an axial flow machine.

So only figure (a) shows a Centrifugal impeller from which we can conclude that all centrifugal pumps are rotodynamic but not all rotodynamic pumps are centrifugal.

Author: Tony Dashwood, Technical Director Crest Pumps


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