Transcript Thermodynamics I

Examples
 Concrete block
 Pontoon
One Minute Paper
Statics
Fluid dynamics
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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
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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
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Kinetic
Potential
Flow
 Energy – changes in properties
Bernoulli Equation
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Energy per weight of flowing fluid
Head
Pressure
Velocity
Elevation
Bernoulli Equation
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Assumptions
Steady state
Incompressible fluid
No friction in fluid stream
Bernoulli Equation
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Useful because:
Process flow reasonable steady
Compressibility effects small
Friction effects minor
Bernoulli Equation – Pitot tube
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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
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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?