Pump efficiency issue
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How is pump efficiency specifically defined? When I was looking at the specifications for high-speed pumps today, I found that some of them have a pump efficiency of less than 30%. Does this mean that the efficiency is very low? Is such a low efficiency acceptable? Hehe, I’m still a student; I just want to learn some basic knowledge
The efficiency formula for a pump is: useful power/shaft power, which takes into account the losses caused by hydraulic, volumetric, mechanical, and other factors. The efficiency of centrifugal pumps is generally considered good when it is around 60-70%; high-speed pumps suffer from greater mechanical losses, and an efficiency of 30% is still considered normal.
The efficiency of a pump is closely related to its structural design. Although pump manufacturers strive to improve efficiency by developing various hydraulic models, the pump’s structure determines that its efficiency can only fall within a certain range. For example, conventional IS centrifugal pumps and those used in petrochemical processes have relatively high efficiencies, reaching over 80%. On the other hand, pumps such as pipeline pumps, low-flow pumps, shielded pumps, and magnetic drive pumps, which also belong to the category of centrifugal pumps, have lower efficiencies – as mentioned by the original poster, these can be as low as 20-30%.
Pumps with high head and low flow rate certainly have low efficiency, whereas pumps with high flow rate and low head have high efficiency; it is mainly a matter of losses.
Efficiency is closely related to head and flow rate; as mentioned above, it is also greatly influenced by the type of impeller. For example, under the same conditions of flow rate and head, the efficiency of a closed impeller is greater than that of a semi-open impeller, which in turn is greater than that of an open impeller.
The efficiency of a pump is related to the flow rate and the specific speed; generally speaking, the higher the flow rate and specific speed, the higher the efficiency； Conversely, the lower it is. There are standards for this; I’ll pass them to you once I have the authority to do so.