What causes an increase in discharge pressure in a pump system?

The increase in discharge pressure in a pump system can be attributed to a number of factors, with increasing flow rate being a key contributor. When the flow rate through a pump is increased, it means that more fluid is being moved through the system in a given amount of time. This higher demand for fluid results in a greater load on the pump, leading to an increase in the pressure at the discharge side.

In a centrifugal pump, as the flow rate increases, the pump has to work against the resistance of the system, including friction losses and elevation changes. This increased resistance generally translates into a higher discharge pressure to maintain the desired flow rate.

On the other hand, reducing impeller size generally decreases the flow rate and can lead to lower discharge pressure, while higher viscosity of fluid typically leads to increased friction losses, which may also result in lower discharge pressure at a constant flow rate. Decreasing the valve opening can create back pressure in the system, which could affect the discharge pressure; however, this option does not directly correlate with an increase in flow rate. Thus, increasing flow rate is the primary factor that leads to an increase in discharge pressure in a pump system.