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Unformatted text preview: 9/11/2008 1 Fluid Mechanics 3502 Fluid Mechanics 3502 Day 4 (Fall, 2008) Day 4 (Fall, 2008) Vapor Pressure (very briefly) Chapter 3: Fluid Statics Part I y The basics y Gage pressure / piezometric pressure y Pressure on a solid surface Vapor Pressure Vapor Pressure y Analogy: boiling temperature ◦ Boiling temperature = temperature at which a liquid boils ◦ Below maintains a liquid ◦ Dependent on pressure y Vapor pressure ◦ Vapor pressure = pressure at which a liquid vaporizes ◦ Above, maintains a liquid ◦ Dependent on temperature (Need gas/liquid interface for this to be important – not such a strict limitation) Vapor pressure (cont’d) Vapor pressure (cont’d) y At a liquid / gas interface the liquid continuously vaporizes and condenses. y If the pressure in the gas above the liquid is higher than the vapor pressure, this reaches a steady state. y IF the pressure above the liquid is less than the vapor pressure more vaporization than condensation occurs pressure, more vaporization than condensation occurs and the liquid boils. y If the liquid is in a closed volume subjected to a vacuum, enough liquid vaporizes to form a gas phase above the liquid that exerts a “vapor” pressure on the liquid y In water at 20 ° C, the water vapor pressure is 2340 Pa Vapor pressure and engineering Vapor pressure and engineering design design - cavitation cavitation y Boiling associated with low pressures often occurs in localized low-pressure zones of flowing liquids, e.g., on the suction side of a pump. e....
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- Fall '08
- Fluid Dynamics, Vapor pressure, Gage Pressure, single liquid