What is the effect of increased head on the discharge of a centrifugal pump?

In a centrifugal pump, the discharge refers to the volume of fluid that is moved through the pump over a certain time. When the head, which is the height of the fluid column that the pump can raise, increases, the relationship between head and discharge becomes crucial to understand.

As head increases, it typically leads to an increase in the resistance against which the pump has to work, known as the system head loss. This increased resistance often results in a decrease in the pump's discharge rate. Essentially, pumps are designed to operate most efficiently at a certain point, known as the Best Efficiency Point (BEP), and as system head increases beyond that point, performance typically drops, leading to a decrease in discharge.

This phenomenon is a result of the pump's characteristic curve, which demonstrates how flow rates change with varying heads. At higher heads, the pump is unable to maintain the same flow rates due to the increased pressure required to overcome the head, which results in a reduction in discharge.

Understanding this concept is critical for engineers and operators when selecting pumps and designing systems to ensure that they operate efficiently within the desired parameters.