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Fluid part 2
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FLUID FLOW MEASUREMENT
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Pitot tube
For a compressible fluid, use the above incompressible fluid equation if the
Mach number ≤ 0.3. 3
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Pitot tube
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• The static pressure of air (1.20 kg/m3) flowing in a pipe is
measured by a precision gauge to be (68.95 kPa). A pitot tube-
manometer indicates (0.523 m) of mercury. The density of
mercury is (13 600 kg/m3). Losses are insignificant. What is the
velocity of the air in the pipe?
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venturi meter
The coefficient of velocity, Cv, accounts for the small effect of friction and
is very close to 1.0, usually 0.98 or 0.99
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Orifices meter
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Orifice Discharging
Submerged Orifice Operating under Steady-Flow Orifice Discharging Freely into Atmosphere
Conditions
c coefficient of discharge of the orifice
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Closed Conduit Hydraulics
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Head loss in pipe
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Pressure Drop for Laminar Flow
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Hazen-Williams Equation
S is the slope of the energy line
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Circular Pipe Head Loss Equation (Head Loss Expressed in Feet)
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Circular Pipe pressure drop Equation
Hazen-Williams Equation
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Open channel flow
An open channel is a fluid passageway that
allows part of the fluid to be exposed to the
atmosphere. This type of channel includes
natural waterways, canals, and pipes flowing
under the influence of gravity
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Uniform Steady Flow
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Uniform Steady Flow
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Manning's Equation
slope of energy grade line
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Minor Losses in Pipe Fittings, Contractions, and Expansions
Head losses also occur as the fluid flows through pipe fittings (i.e.,
elbows, valves, couplings, etc.) and sudden pipe contractions
and expansions.
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Minor Losses in Pipe Fittings, Contractions, and
Expansions
• Specific fittings have characteristic values of C, which will be provided in the problem statement
• generally accepted nominal value for head loss in well-streamlined gradual
contractions
• The head loss at either an entrance or exit of a pipe from or to a
reservoir
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• A pipe transmits water from a tank A to point C that is lower than water level in the
tank by 4 m. The pipe is 100 mm diameter and 15 m long. The highest point on the
pipe B is 1.5 m above water level in the tank and 5 m long from the tank the fluid
velocity is 1.26 m/s . The friction factor is 0.08, with sharp inlet to the pipe.
Calculate the pressure in the pipe at the point B?
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Multipath Pipeline Problems
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Series pipes
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Parallel pipe
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Pump
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Pump head
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Pump power
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CAVITATION
What is the cavitation :
spontaneous vaporization of fluid inside the pump
Why cavitation happen ?
Where ever the fluid pressure is less than vapor
pressure small pocket of vapor will form as vapor
pocket reach the service of Impeller local high fluid
pressure collapses them
Cavitation disadvantage
Vibration , noise, and impeller pitting and structure
damage to pump
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Net positive head available
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Find NPSHA
Source Pressure = 1 Kg / Cm2
Suction Lift - 3 m
Friction loss in pipeline
Foot Valve, Strainer, Bend, Valve
1m, temperature of water : 20°C
A. 5.8
B. 10
C. 1
D. 100
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Find NPSHR
• Vacuum in Vessel 600 mm of HG
Temperature : 40°C,
• Friction Loss : 1m
Vapour pressure is 7.38 K Pa
• Sg of mercury : 13.6
A. 16
B. 20
C. 22
D. 30
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Centrifugal Pump Characteristics
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Operating point
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Practical pump curve
FE Course
pump selection
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Pumps in Series
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Pumps in Parallel
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Scaling Laws; Affinity Laws
Two pumps are geometrically similar when all corresponding dimensions have the
same constant ratio and all angles such as blade angles, β 1 and β 2, are equal
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A 6 in pump operating at 1770 rpm discharges 1500 gal/min of cold
water (SG = 1.0) against an 80 ft head at 85% efficiency. A
homologous 8 in pump operating at 1170 rpm is being considered as
a replacement What total head and capacity can be expected from
the new pump
A. 62 ,2400
B. 62 ,3000
C. 100 ,7000
D. 0, 0
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THE IMPULSE-MOMENTUM PRINCIPLE
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PIPE BENDS, ENLARGEMENTS, AND CONTRACTIONS
The impulse-momentum principle illustrates that fluid
momentum is not always conserved when the fluid is acted upon
by an external force. Examples of external forces are gravity (
considered zero for horizontal pipes), gage pressure, friction, and
turning forces from walls and vanes. Only if these external forces
are absent is fluid momentum conserved.
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impulse-momentum
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Water is accelerated by a nozzle to an average speed of 20 m/s, and strikes a stationary
vertical plate at a rate of 10 kg/s with a normal velocity of 20 m/s After the strike, the
water stream splatters off in all directions in the plane of the plate. Determine the
force needed to prevent the plate from moving horizontally due to the water stream.
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