What factors are related to pump efficiency

Time:2022.12.28Browse:

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1. Mechanical loss


It is mainly the friction loss (also called disc loss) between the liquid and the outer surface of the front and rear cover plates of the impeller and the pump chamber.




The disc loss accounts for a large proportion, even up to 30% of the effective power. The test shows that the disc loss is proportional to the third power of the rotating speed and the fifth power of the impeller outer diameter. Therefore, the larger the outer diameter of the impeller, the greater the disc loss. Although the disc loss is proportional to the third power of the speed, at a given head, with the increase of the speed, the outer diameter of the impeller is correspondingly reduced (it can be considered that the pump speed is doubled, and the outer diameter of the impeller is halved), and the disc loss is proportional to the fifth power. Therefore, with the increase of the speed, the disc loss does not increase, but decreases, which is one of the reasons for the development of high-speed pumps.



2. Volume loss


A part of the liquid in the impeller leaks back to the impeller inlet through the clearance of the impeller seal ring and cannot be effectively utilized, resulting in loss. Therefore (official account: pump steward), the smaller the clearance of the seal ring, the better. However, due to processing and assembly and other reasons, too small the clearance may cause eccentric wear or seizure. The national standard has made special provisions on the clearance of various types of pumps.




3. Hydraulic loss


The fluid in the overflow part of the pump (from the inlet to the outlet) must have the loss caused by the change of speed and direction. These two parts are hydraulic losses. To reduce this loss, in addition to improving the smoothness of the flow passage components, try to select an excellent hydraulic model.


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