The function of minimum flow valve

At a certain temperature, the liquid generates bubbles when the pressure is reduced to the vaporization pressure at this temperature. This bubble generation phenomenon is called cavitation. The bubbles generated during cavitation are reduced in volume and burst when flowing to high pressure. Such phenomenon that bubbles disappear in liquid due to pressure rise is called cavitation collapse. When the pump is in operation, if the absolute pressure of the pumped liquid is reduced to the liquid vaporization pressure at the current temperature due to the high speed friction between the blade and the fluid in the local area of the flowing part (usually somewhere behind the impeller blade inlet), the liquid will start to vaporize, generate a lot of steam and form bubbles. When the liquid containing a lot of bubbles moves forward through the high pressure area in the impeller, the high pressure liquid around the bubble will cause the bubble to shrink sharply and even break. At the same time of bubble condensation and fracture, the liquid particle fills the hole at a very high speed, at this moment, it generates a very strong water hammer effect, and strikes the metal surface with a very high impact frequency, the impact stress can reach hundreds to thousands of atmospheres, the impact frequency can reach tens of thousands of times per second, and the wall thickness can be broken down in serious cases. The cavitation process in the water pump is the process of generating bubbles and breaking bubbles in the water pump to damage the flow passage parts. In addition to the damage to the flow passage parts, the cavitation of the water pump will also produce noise and vibration, which will lead to the performance degradation of the pump. In serious cases, the liquid in the pump will be interrupted and cannot work normally. The function of the minimum flow valve is to prevent the heat from being carried away at low flow and ensure the minimum flow through the pump。
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