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Examples

Examples . Concrete block Pontoon . One Minute Paper. Statics. Fluid dynamics . Fluids in motion Pumps Fans Compressors Turbines Heat exchangers. Conservation . Energy & mass; neither created nor destroyed in ordinary process Control volume

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Examples

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  1. Examples • Concrete block • Pontoon

  2. One Minute Paper Statics

  3. Fluid dynamics • Fluids in motion • Pumps • Fans • Compressors • Turbines • Heat exchangers

  4. Conservation • Energy & mass; neither created nor destroyed in ordinary process • Control volume • Steady state: no accumulation nor depletion

  5. Flowing fluid • Steady flow • Uniform flow • Mass flow rate: Kg/ time, lbm/time • Volume flow rate: m3/time, ft3/time, cfm, gpm

  6. Continuity Mass flow rate Volume flow rate

  7. Nozzle • (ρVA)1= (ρVA)2

  8. Energy balance • Kinetic • Potential • Flow •  Energy – changes in properties

  9. Bernoulli Equation • Energy per weight of flowing fluid • Head • Pressure • Velocity • Elevation

  10. Bernoulli Equation • Assumptions • Steady state • Incompressible fluid • No friction in fluid stream

  11. Bernoulli Equation • Useful because: • Process flow reasonable steady • Compressibility effects small • Friction effects minor

  12. Bernoulli Equation – Pitot tube • Horizontal • Velocity at stagnation point is 0 • Incompressible fluid • Steady state • Velocity as function of pressure difference

  13. Bernoulli Equation • P/ - static pressure • V2/2g – velocity pressure • PT = PS + PV • V = [(2g/) (PT – Ps)]1/2

  14. Hot Wire Anemometer

  15. Example • Water flowing from hose attached to a main at 400kPa. Boy covers most of hose outlet with thumb, producing a vertical, thin jet of high speed water. What is maximum height of jet?

  16. Example • A large tank open to the atmosphere is filled with water. A tap near the bottom of the tank is opened to allow flow from a smooth, rounded opening. Find the outlet velocity.

  17. Example • During a trip, motorist runs out of fuel. A helpful driver allows you to siphon fuel from her auto. (2) is located 0.75m below (1); (3) is 2m above (1). Siphon diameter is 4mm. Find the minimum time to transfer 4 L of fuel & the pressure at (3). Fuel density is 750 kg/m3.

  18. Homework • Water flows through a 2-inch diameter pipe at 200 lbm/min. Its temperature is 60oF. Find the velocity of water flow.

  19. Homework • Water from a pipe line is diverted into weigh tank for exactly 9 minutes. Tank weight increases 4765 lbf. Water temperature is 60oF.

  20. Homework • Steady flow of gas through a pipe whose diameter decreases from 1.0 meter to 60cm. The gas density decreases from 2 kg/m3 to 1.6 kg/m3. The entering velocity is 25 m/s. What is exit velocity?

  21. Reynolds Transport Theorem • General energy equation: expands Bernoulli Equation

  22. References • Images & examples • Mechanics of Fluids, 3rd Edition, Potter & Wiggert, Brooks & Cole • Applied Fluid Mechanics, 6th Edition, Mott, Prentice Hall • Engineering Fluid Mechanics, 5th Edition Crowe, & Roberson, Wiley • Fluid Mechanics Cengel & Cimbala McGraw Hill • Which of the examples were helpful?

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