3. Flow through a NozzleFlow through a Nozzle
2211
21
222111
21
vAvA
ibleincompress
vAvA
Avm
mm
=
ρ=ρ
ρ=ρ
ρ=
=
1
1
1
1
v
A
m
ρ
2
2
2
2
v
A
m
ρ
Basic Equations:
a.) Continuity:
mass in = mass out
b.) Bernoulli’s Eqn.
Total pressure is
constant throughout
7. Y = Compressibility Factor
=1 for incompressible flow
or when ∆P<< Pabs
C= Discharge Coefficient
=f(Re) and
nature of specific flow meter
∆P
Flow through a NozzleFlow through a Nozzle
P
8. Flow through a Venturi MeterFlow through a Venturi Meter
In a venturi, 0.95 < C < 0.98
Advantage:
Pressure recovery
Uses little power
9. Flow through a Venturi MeterFlow through a Venturi Meter
C
Re
2 x 105
µ
ρ
= 11vd
e
R
0.98
Based upon the conditions in the pipe
approaching the meter
10. Back to the NozzleBack to the Nozzle
P1 P2
P
P1
P2
11. Shorter and cheaper than venturi
But larger pressure drop.
Thus, more power lost in operating.
The Nozzle FlowmeterThe Nozzle Flowmeter
C
0.86
0.98
103
105
Re
13. Flow Through an Orifice MeterFlow Through an Orifice Meter
P1 P2
P
P1
d D
14. Flow Through an Orifice MeterFlow Through an Orifice Meter
-Cheapest and Simplest
-But biggest pressure drop and power lost (C~0.6 - 0.7)
-Side Note:
Pressure drop caused by friction and turbulence of shear
layer downstream of vena contracta
CM
A
A
C =
−
2
1
2
1
1
0.6
0.85
β=d/D0.1 0.8
Re
100k
5000
10k
21. Vortex meters operate on the principle that when a non-streamlined
object is placed in the middle of a flow stream, vortices are shed
alternately downstream of the object. The frequency of the vortex
shedding is directly proportional to the velocity of the liquid
flowing in the pipeline.
23. Based upon Faraday’s Law
The fluid is the conductor, must be electrically conductive.
E=BDVx10-8
E=voltage, volts
B=magnetic flux density, gauss
D= length of the conductor, cm
V=velocity of the conductor, cm/sec
Magnetic flowmeterMagnetic flowmeter
26. Coriolis Mass Flow MeterCoriolis Mass Flow Meter
Vibrating Flow Tube
Fluid Force is Reacting to Vibration
of Flow Tube
End View of Flow Tube
Showing Twist
Twist Angle
Twist Angle
Flow
Force
Flow Force
Flow
Flow
