What happens to the discharge flow of centrifugal pumps when the discharge head increases?

When the discharge head increases in a centrifugal pump system, the discharge flow typically decreases due to the pump's operating characteristics and the relationship between flow rate and head.

Centrifugal pumps operate based on the principles of converting rotational energy into kinetic energy, which is then converted into pressure energy to move the fluid. The performance of a centrifugal pump is often represented by a pump curve, which illustrates how flow rate varies with discharge head.

As the discharge head increases, the centrifugal pump reaches a point where it cannot maintain the same flow rate against the higher pressure requirements. This is because the pump has a specific design point where it operates most efficiently. When the system head (total discharge head) rises beyond this design point, the pump's ability to push fluid through the system diminishes, resulting in a decrease in flow rate.

In practical applications, if you were to plot the flow rate against the discharge head, you would observe an inverse relationship: increased head leads to reduced flow. This behavior is fundamental in pump design and operation, reflecting the limits of the pump's capability to overcome head losses. Thus, as discharge head increases, the discharge flow decreases, confirming the answer.