Efficiency issues of various pumps
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I would like to ask everyone for advice: During the project quotation phase, the prices for the mechanical equipment have not yet been obtained. I am currently trying to calculate the power consumption and estimate the efficiency of the pumps, but I’ve encountered a problem. Below are some efficiency data for pumps that I have used in the past: The boiler feed pumps made by KSB can achieve an efficiency of 65%, with a head of 400 meters and a flow rate of 30 tons. Waste water pumps have a head of around 60 meters and a flow rate of about 30 cubic meters. The fluorocarbon-lined centrifugal pumps made by Riichi only achieve an efficiency of 53%. Blackman’s sliding vane pumps, with a flow rate of 600 L/h and a pressure of 5 barg, have an efficiency of only 34%. Wilo’s gear pumps, with a flow rate of 500 L/h and a pressure of 5 barg, also have an efficiency of only 30%. These values are quite far from the 90% efficiency mentioned in textbooks. So I’m a bit confused – the efficiency of different pumps varies greatly; it’s rare to see efficiencies of 70%. The efficiency of fans, on the other hand, is relatively stable, ranging from 75% to 80%. I would like to ask everyone how I can estimate the efficiency of a pump in order to determine the initial power consumption. Thank you
At noon today, I also discussed pump efficiency with Guanzhong Caizi from the forum. Pump efficiency is closely related to the pump’s specific speed, flow rate, and structural design (such as the type of impeller). Even for pumps of the same model available on the market, those produced by different manufacturers can have varying efficiencies, and this is related to the precision of the manufacturing process. In my opinion, when choosing a pump, the efficiency of the pumps should be compared under identical conditions; for example, it makes sense to compare efficiencies when several different pump types are capable of delivering the same flow rate and head. It is meaningless to compare the efficiencies of pumps with different performance characteristics, so it is necessary to consider the specific operating conditions one is in order to make such a comparison.
I would like to ask why the efficiency of the gear pump I described is so low – only 30%
The efficiency of a gear pump should be around 70%-80%; in some cases it can reach up to 90%. The 30% you mentioned likely refers to the system efficiency. If you have any questions when selecting or purchasing a pump, remember to communicate more with the pump manufacturer; don’t rely solely on the instructions. Differences in errors and the literal meaning of the text can lead to confusion, and may even result in incorrect pump selection.
I suspect the formula you used to calculate the pump efficiency is incorrect; the efficiency calculation methods for gear pumps, which are positive displacement pumps, differ from those for centrifugal pumps. Hehe
I don’t calculate the pump’s efficiency; I just choose the model specified by the manufacturer.
Different operating conditions, different manufacturers, and various pump types can all affect efficiency; even the same pump may exhibit different efficiencies under different operating conditions. There is no unified conclusion on this; it is recommended that you contact the manufacturer to inquire about the price.