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Efficiency of water pump

Efficiency refers to the percentage of the effective power of the water pump and the ratio of shaft power, it marks the effective degree of energy conversion of the water pump, which is an important technical and economic index of the water pump. The efficiency on the pump nameplate is corresponding to the efficiency when the flow is designed, which is the highest efficiency of the pump. The higher the efficiency of the pump, the smaller the energy loss when the pump is working.  The pump shaft power cannot be fully transmitted to the output of the liquid, which must be part of the energy loss. The energy loss in a water pump can be divided into three parts, namely hydraulic loss, volume loss, and mechanical loss.

Hydraulic loss and hydraulic efficiency

Friction loss, local loss, and impact loss are generated when water flows through the suction chamber, impeller, and pressure chamber of the pump. Friction loss is the loss caused by friction resistance between the flow of water and the wall of the overflow parts. Local loss is the loss caused by the change of flow velocity and direction in the pump. The impact loss is the loss caused by the flow of water at the inlet, outlet, and pressure out of the chamber of the pump under the non-design condition. The greater the hydraulic loss, the smaller the head of the pump. The head of the water pump which does not consider the loss of water force in the water pump is the theoretical head HT, then the ratio of the water pump head H to the theoretical head HT is called hydraulic efficiency H.

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Efficiency of water pump

Volume loss and volume efficiency

After the flow of water through the impeller, a small part of high-pressure water passes through the pump internal clearance (such as leakage ring) and axial force balancing device (such as balance hole) leakage into the impeller inlet, and another part leakage from the shaft package to the pump outside, which consumes part of the energy, that is, volume loss. The larger the leakage q, the smaller the water output q of the pump. The ratio of flow Q through the pump outlet to the flow Q + Q through the pump inlet is called volume efficiency v.

Mechanical loss and mechanical efficiency

When the impeller rotates in the liquid, the outer surface of the front and rear cover plate and the liquid produce friction loss (that is, the wheel loss). When the pump shaft rotates, the shaft and shaft seal and bearings produce friction loss. After the mechanical loss is deducted from the input power of the pump, the power transferred by the impeller to the liquid is called water power, which is represented by PW.

The efficiency of the water pump is the product of volume efficiency, hydraulic efficiency, and mechanical efficiency. To improve the efficiency of the pump, we must reduce all kinds of losses in the pump. To improve the efficiency of water pump, in addition to improving and improving the aspects of the hydraulic model, selection of materials, processing technology, parts, and other aspects, the use unit should pay attention to correctly selecting pump type, ensuring installation quality, reasonably adjusting operation conditions and strengthening maintenance management. Only in order to make the pump often operate in an efficient state, to achieve the purpose of saving energy, reducing costs, and improving economic benefits.


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