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Mass flow meter
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Mass flow meter

• Direct measurement of true value of mass flow
  rate
• Principle- an additional movement is imparted to
  a flowing fluid where by an intermediate
  measuring parameter derived in system

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Turbo flow meter ( mass flow)

• Principle conservation of angular momentum
• Moment of momentum law in turbodynamics

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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. motor gear mechanism
• 2 impeller driven element- connected to a spring
• Stationary disc to 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 a pressure.
  Rotates driven wheel
• Balanced by spring to equilibrium
• To which a rotational pickup is attached

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Working

• torsion proportional to flow
• Instead of spring retarding disc, magnetic
  assembly is used

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Mass flow meter Coriolis flow meter

• Used to find mass flow rates of foams, slurries,
  mixtures
• Used for sticky, thick viscous fluids like oils,
  sand mix, peanut butter

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Principle- coriolis flowmeter

• 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 working

• A 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 deflection proportional
  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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Electromagnetic flow meter

• Principle Faradays Law of electromagnetic
  Induction
• Ie, sped of flow measured in terms of potential
  difference induced when liquid moves in a pipe
  transverse to magnetic field

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• E - B.d. v X 10 -8 V
• Where
• B- magnetic flux density
• D- diameter of tube
• V- velocity of liquid low

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• As long as flux density is constant, Volume flow
  rate proportional to induced emf
• Min conductivity 10 -3 S /m
• Insulating non magnetic pipe

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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 gt20 K Hz can be beamed is used

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Ultra sonic flow meter

• methods

Doppler shift
Transit time effect
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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 / c 2

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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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Advantages

• Wide range -0.03 cm/s to 120 m/s
• Good precisio
• No pressure loss

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Disadvantage

• Less sensitive

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