The issue of diameter changes in the inlet and outlet pipes of water pumps
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A colleague told me that the reduction in diameter at the pump inlet is intended to provide the fluid inside the pump with an adequate initial velocity, while the increase in diameter at the outlet is meant to reduce the flow velocity and thus convert kinetic energy into potential energy (pressure) more effectively. Generally, the flow velocity at the pump inlet is lower than that at the outlet; therefore, the pipe diameter at the pump inlet must be larger than that at the outlet. I would like to ask whether the diameter of the pump’s outlet pipe affects its outlet pressure What is their relationship? Is there a linear relationship between flow rate and pressure? Thank you all, experts
The inlet pipe is larger than the pump’s inlet in order to reduce the flow velocity and increase the device’s net positive suction head. There must be 5 times the length of straight pipe before the API pump inlet. Thickening the pump outlet is done to reduce losses in the outlet pipeline. The selection of the pipe diameter can be based on the maximum allowable resistance drop specified in the standards, that is, the KPa value of resistance drop over a pipe length of 100 meters.
The inlet pipe termination is intended to increase the net positive suction head; a larger pipe diameter, lower flow velocity, and higher inlet pressure all make it less likely for cavitation to occur in the pump.
Your colleague is right; you should make up for it by studying specialized courses like fluid mechanics – pumps and fans