Seeking help with the actual calculation principles for the shaft power and efficiency of centrifugal pumps
Thread Content
In the testing of centrifugal pumps, shaft power and efficiency are evaluated. Nowadays, the data is generally generated directly by the test bench. The problem is that I’ve encountered a manufacturer who, using the same current, voltage, head, and flow rate, produced two different sets of data. I would like to know what parameters these test benches use to calculate the shaft power and efficiency of the pumps 1. The parameters that can be measured include inlet and outlet pressure, flow rate, current, and voltage ； 2. For shielded pumps, the motor itself is manufactured by the pump manufacturer; how is the shaft power and efficiency of such pumps calculated? Even the rotation speed cannot be measured. It was found in the forum that shaft power = (flow rate × head × density) / (3600 × 102 × efficiency). What parameter is this 102? Which pump to choose?
102=1000/9.81
Efficiency is effective power divided by shaft power. Shaft power can be calculated by multiplying the motor’s input power by efficiency; the transmission efficiency of the coupling can generally be ignored
In the case of shielded pumps, where the rotor rotates within the medium, the efficiency of the motor can only be at a theoretical level
You don’t need to worry about shaft power and efficiency; it’s something provided by the manufacturer, but it’s not necessarily accurate. For pumps of the same model and with identical parameters, the efficiency difference is only 2%-3%. What other manufacturers provide you is usually already processed. If you really want to pay attention to it, then buy a flow meter by yourself and measure it once the pump is running.
Simply put, the efficiency of a pump is the work done on the fluid, expressed as a percentage of the power delivered by the motor to the pump.
I don’t want to get entangled in this issue. The problem lies with the QPI610; sometimes, the manufacturer and the owner sign an agreement specifying that the deviation from the rated power should not exceed 104%, and that’s when problems can arise