#### Transcript Thermodynamics I

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 Steady state: no accumulation nor depletion Flowing fluid Steady flow Uniform flow Mass flow rate: Kg/ time, lbm/time Volume flow rate: m3/time, ft3/time, cfm, gpm Continuity Mass flow rate Volume flow rate Nozzle (ρVA)1= (ρVA)2 Energy balance Kinetic Potential Flow Energy – changes in properties Bernoulli Equation • • • Energy per weight of flowing fluid Head Pressure Velocity Elevation Bernoulli Equation • • • Assumptions Steady state Incompressible fluid No friction in fluid stream Bernoulli Equation • • • Useful because: Process flow reasonable steady Compressibility effects small Friction effects minor Bernoulli Equation – Pitot tube Horizontal Velocity at stagnation point is 0 Incompressible fluid Steady state Velocity as function of pressure difference Bernoulli Equation P/ - static pressure V2/2g – velocity pressure PT = P S + P V V = [(2g/) (PT – Ps)]1/2 Hot Wire Anemometer 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? 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. 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. Homework Water flows through a 2-inch diameter pipe at 200 lbm/min. Its temperature is 60oF. Find the velocity of water flow. Homework Water from a pipe line is diverted into weigh tank for exactly 9 minutes. Tank weight increases 4765 lbf. Water temperature is 60oF. 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? Reynolds Transport Theorem General energy equation: expands Bernoulli Equation 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?