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Mass flow meter Direct measurement of true value of
mass flow rate
Principle- an additional movement isimparted to a flowing fluid where by an
intermediate measuring parameter
derived in system
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Turbo flow meter ( massflow) Principleconservation of angular
momentum
Moment of momentum law inturbodynamics
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Turbo flow meter
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Turbo flow meter -construction 2 impellers mounted on coaxial distance
Channels are provided on impellers
Impeller at up stream rotated at const.Speed -by syn. motorgear mechanism
2 impeller driven element- connected to a
spring Stationary discto reduce viscous
coupling b/w impellers
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working Fluid enters the channel of impeller- exert
inertial moment causing a torsion.
Liquid now in II impeller- exert apressure. Rotates driven wheel
Balanced by spring to equilibrium
To which a rotational pickup is attached
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Mass flow meter Coriolisflow meter Used to find mass flow rates of foams,
slurries, mixtures
Used for sticky, thick viscous fluids likeoils, sand mix, peanut butter
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Principle- coriolisflowmeter Any body moving with a const velocity on
a rotating surface with an angular velocity
will acquire an acceleration F F perpendicular to V &
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Construction workingA U tube flow line is used- suspended on a
cantilever with its two ends supported on
a mounting. -A fluid passed with constant velocity V , -
made to vibrate with angular velocity
-Will produce a torsion deflectionproportional to V
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Bridge Type flow meter
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Bridge type flow meter Pressure drop across pump proportional
to mass flow
w = K P
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E = - B.d. v X 10 -8V
Where
B- magnetic flux density
D- diameter of tube
V- velocity of liquid low
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application Corrosive acids, acid slurries, paper pulp,
detergents etc
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advantages Does not obstruct flow
No moving part
Good accuracy
Reliable
Fast response
Independent of other fluid properties
except conductivity
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Disadvantages Pipe should be full
Expensive for small pipes
o/p in micro volts so needs amplification
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Ultra sonic transducer Sound travels in material medium
Propagation of sound is modulated by
characteristics of medium High freq >20 K Hzcan be beamed is
used
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Ultra sonic flow meter methods
Doppler
shift
Transit
timeeffect
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Doppler shift Particles in fluid impart a freq. Shift
proportional to particle velocity
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Transit time type
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Phase shift = 2 w v b / c2
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Doppler method
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Doppler method
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Laser anemometer Employed where txn of coherent laser
light through fluid is possible
Provide scattering also Doppler phenomena
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Laser anemometer Freq of scattering beam from a moving
object differ from incident beam by a
value proportional to velocity of body Ie, fd propotional to flow velocity
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Block schematic
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Disadvantage Less sensitive
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