If the pumping rate in a variable speed centrifugal pump is doubled, what will happen to the discharge pressure?

When the pumping rate in a variable speed centrifugal pump is doubled, the discharge pressure will typically increase. This relationship arises from the principles of pump performance and fluid dynamics.

In centrifugal pumps, the discharge pressure is influenced by the flow rate and the system's resistance. As the pump speed increases, it imparts more energy to the fluid, allowing it to overcome the system's head loss – which includes friction losses, elevation changes, and other factors. This results in a higher discharge pressure as the pump works harder to move a greater volume of fluid.

The fundamental concept here is that centrifugal pumps are designed to provide a certain relationship between flow rate and pressure. As the flow rate increases, the pressure generated by the pump also increases, given that the system conditions allow for it. Thus, when the pumping rate is doubled, the increase in energy supplied to the fluid leads to a corresponding increase in discharge pressure.

Other options may imply that pressure decreases or remains the same, which would not occur under normal operating conditions for a centrifugal pump when flow is increased, as well as suggesting that discharge pressure becomes inconsistent, which is not typical unless there are fluctuations in system resistance or other operational issues.