Pressure changes due to the variable diameter at the outlet of the centrifugal pump
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The centrifugal pump has a diameter change at its outlet; the diameter of the pump’s outlet pipe is DN450, while that of the reduced-diameter section is DN600. If pressure gauges are installed on both pipes, which one will show a higher pressure? (Losses are not considered for now)
Theoretically, the outlet pressure should be higher, but the outlet pressure of a centrifugal pump is related to the pressure and resistance in the downstream system; therefore, the actual measured pressure should be the same
Ignoring losses, the total energy is theoretically balanced. If the pipeline is horizontal, after the diameter is increased the flow velocity decreases, the kinetic energy drops, and this can be converted into pressure energy. But on the vertical section, the height increases, meaning kinetic energy is converted into potential energy; as more of it is converted, the pressure energy decreases instead. It’s not easy to determine whether the pressure is increasing or decreasing.
Bernoulli’s equation, calculated theoretically