1 / 11

FLUID PROPERTIES Chapter 2

FLUID PROPERTIES Chapter 2. CE319F: Elementary Mechanics of Fluids. Elasticity (Compressibility). If pressure acting on mass of fluid increases: fluid contracts If pressure acting on mass of fluid decreases: fluid expands

melvyn
Download Presentation

FLUID PROPERTIES Chapter 2

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. FLUID PROPERTIES Chapter 2 CE319F: Elementary Mechanics of Fluids

  2. Elasticity (Compressibility) • If pressure acting on mass of fluid increases: fluid contracts • If pressure acting on mass of fluid decreases: fluid expands • Elasticity relates to amount of deformation for a given change in pressure Ev = bulk modulus of elasticity How does second part of equation come about? Small dV/V = large modulus of elasticity

  3. Example Based on the definition of Ev and the equation of state, derive an equation for the modulus of elasticity of an ideal gas.

  4. Vapor Pressure (Pvp) • Vapor pressure of a pure liquid = equilibrium partial pressure of the gas molecules of that species above a flat surface of the pure liquid • Concept on board • Very strong function of temperature (Pvp up as T up) • Very important property of liquids • When Pvp exceeds total air pressure applied at surface, liquid will boil. • Pressure at which a liquid will boil for a given temperature • At 10 oC, vapor pressure of water = 0.012 atm = 1200 Pa • If reduce pressure to this value - get boiling of water • Formation of cavitation bubbles • Harm to pipes, pumps, turbines, propellers • If Pvp > 1 atm compound = gas • If Pvp < 1 atm compound = liquid or solid

  5. Vapor Pressure (Pvp) Water Vapor pressure of water (and other liquids) is a strong function of temperature.

  6. Vapor Pressure (Pvp) - continued Pvp,H2O = Pexp(13.3185a – 1.9760a2 – 0.6445a3 – 0.1299a4) P = 101,325 Pa a = 1 – (373.15/T) T = oK valid to +/- 0.1% accuracy for T in range of -50 to 140 oC Equation for relative humidity of air = percentage to which air is “saturated” with water vapor. How does RH affect drying of building materials, and why? Implications? How does RH affect dust mites? Implications?

  7. 300 mm Dust Mites

  8. Example (HW!): Relative Humidity • The relative humidity of air in a room is 80% at 25 oC. • What is the concentration of water vapor in air on a volume % basis? • If the air contacts a cold surface, water may condense (see effects on next slide). What temperature is required to cause water condensation?

  9. Example: Relative Humidity Continued

More Related