0107 Lecture9_NPSH

0107 Lecture9_NPSH - suction side near the pump impeller...

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    1 MER 439 - Design of Thermal Fluid  Systems Professor Anderson Winter Term 2010
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    2 Cavitation Low pressures are commonly encounter-ed on  the suction side of a pump Cavitation can occur Cavitation occurs when a liquid pressure at a  given location is reduced to the vapor pressure  of the liquid. Vapor bubbles form and the liquid  starts to boil. Causes loss in efficiency and structural  damage to the pump.
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    3 Cavitation - NPSH To characterize the potential for cavitation  the difference in the total head on the 
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Unformatted text preview: suction side near the pump impeller inlet and the liquid vapor pressure head is used: g v P g s V g s P NPSH - + = 2 2 4 Net Positive Suction Head (NPSH) The required NPSH R is the value that must be maintained to avoid cavitation. The available NPSH A represents the head loss that actually occurs for the system. 5 Example 1 Q = 0.5 ft 3 /sec NPSH R = 15 ft T = 80 o F P = 14.7 psi k L = 20, D = 4 in Determine the maximum z 1 for no cavitation...
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0107 Lecture9_NPSH - suction side near the pump impeller...

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