flow measurement important variable in plant operation important variable in plant operation...
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Flow measurementFlow measurement
Flow measurementFlow measurement
Important variable in plant operationImportant variable in plant operation Measured primarily for determining Measured primarily for determining
the amount of fluid flowing the amount of fluid flowing
Fluid typesFluid types
Less or highly viscousLess or highly viscous Clear or opaqueClear or opaque Clean or dirtyClean or dirty Wet or dryWet or dry Erosive or corrosiveErosive or corrosive
Fluid flow typeFluid flow type
Stream line or viscous or laminarStream line or viscous or laminar TurbulentTurbulent Combined viscous or turbulentCombined viscous or turbulent
Fluid flow – steam lineFluid flow – steam line
Occurs at low velocitiesOccurs at low velocities All parts flowing in one direction All parts flowing in one direction
parallel to walls parallel to walls Change in cross section means Change in cross section means
change in direction of flowchange in direction of flow Pressure drop Pressure drop ∞∞ flow velocity flow velocity
Fluid flow - turbulentFluid flow - turbulent
Liquid behaves as independent Liquid behaves as independent entitiesentities
Pressure varies with Kinetic energyPressure varies with Kinetic energy Prop. To square of turbulent flow Prop. To square of turbulent flow
velocityvelocity
Flow meterFlow meter
Flow measured as a quantity or rate Flow measured as a quantity or rate of flowof flow
In terms of weight or flowIn terms of weight or flow
Types of flow metersTypes of flow meters
Head type metersHead type meters Rota meter (variable –area type)Rota meter (variable –area type) Electromagnetic typeElectromagnetic type Mechanical typeMechanical type AnemometerAnemometer Ultrasonic flow meterUltrasonic flow meter Vortex flow meterVortex flow meter
Head type flowmeterHead type flowmeter
Produce a pressure difference when Produce a pressure difference when fluid flow is maintained through themfluid flow is maintained through them
Diff. Pressure propotional to square Diff. Pressure propotional to square of flow rateof flow rate
Uses Bernoulli’s theoremUses Bernoulli’s theorem
Bernoulli's theormBernoulli's theorm
Bernoulli’s theormBernoulli’s theorm
Pressure head + velocity head + Pressure head + velocity head + elevation head (at a point) = elevation head (at a point) =
pressure head + velocity head + pressure head + velocity head + elevation head ( at some other point) elevation head ( at some other point) + loss due to friction+ loss due to friction
Bernoulli’s theormBernoulli’s theorm
For in compressible liquidFor in compressible liquid
Q = EAQ = EA22 sqrt ( (2gP sqrt ( (2gPdd)/ )/ ρρ))
For compressible liquidFor compressible liquid
Q = EAQ = EA2 2 φφ sqrt ( (2gP sqrt ( (2gPdd)/ )/ ρρ11))
Head flow meter -typesHead flow meter -types
Orifice meterOrifice meter VenturimeterVenturimeter Flow nozzleFlow nozzle Pitot tubePitot tube
Orifice metersOrifice meters
Orifice metersOrifice meters
Head type meter used for large Head type meter used for large &medium pipes&medium pipes
Orifice plate- inserted to pipe to Orifice plate- inserted to pipe to create a partial restriction to flowcreate a partial restriction to flow
Pressure before orifice plate rises Pressure before orifice plate rises and pressure after it reduces but and pressure after it reduces but velocity increasesvelocity increases
Pressure differncesPressure differnces
Position where velocity is maximum Position where velocity is maximum & static pressure is min is known as & static pressure is min is known as vena contractavena contracta
Diff. Pressure calculationDiff. Pressure calculation
Orifice meterOrifice meter
Usually pressure tapping is at a Usually pressure tapping is at a distance D & D/2 for up stream & distance D & D/2 for up stream & down streamdown stream
D- diameter of pipeD- diameter of pipe For pipe size 0.05m or moreFor pipe size 0.05m or more Orifice to pipe diameter is 0.6Orifice to pipe diameter is 0.6
Friction & contraction effects are Friction & contraction effects are considered. So new term is considered. So new term is incorporated called discharge co-incorporated called discharge co-efficient ©efficient ©
C varies with Reynolds's no.C varies with Reynolds's no.
Q = 2.35 X 10 Q = 2.35 X 10 -3-3 c d c d22 E E √√ (P (Pdd / /ρρ))
Flow measurementFlow measurement
ConstructionConstruction
Normal thickness -0.015 m for pipe Normal thickness -0.015 m for pipe with diameter 0.15 m & 0.003 for with diameter 0.15 m & 0.003 for largerlarger
Materials used bronze, stainless Materials used bronze, stainless steel, phosphor bronze, gun metal steel, phosphor bronze, gun metal etc.etc.
Orifice plate & flangesOrifice plate & flanges
Types of orifice platesTypes of orifice plates
Types of orifice plateTypes of orifice plate
If fluid contains suspended If fluid contains suspended materials , particles tend to settle materials , particles tend to settle down in orifice,- to avoid this- down in orifice,- to avoid this- segmented or ccentric type usedsegmented or ccentric type used
AdvantageAdvantage
Simple, reliableSimple, reliable
DisadvantageDisadvantage
Poor accuracy, Poor accuracy, poor calibrationpoor calibration maintenance problemsmaintenance problems
Venturi meterVenturi meter
Three sections- venturimeterThree sections- venturimeter
Converging conical section at up Converging conical section at up streamstream
Cylindrical throat- provides a panel Cylindrical throat- provides a panel for measurement- pressure for measurement- pressure decreased- flow rate steadydecreased- flow rate steady
Diverging recovery outletDiverging recovery outlet
Principle- Bernoulli's theormPrinciple- Bernoulli's theorm
dimensionsdimensions
Throat to diameter ratio 0.25 to 0.75Throat to diameter ratio 0.25 to 0.75 Discharge co-efficient – 0.9 to 1.0Discharge co-efficient – 0.9 to 1.0 Made of cast iron, gun metal, Made of cast iron, gun metal,
stainless steelstainless steel May be circular, square or May be circular, square or
rectangularrectangular
featuresfeatures
Calculation similar to orifice plateCalculation similar to orifice plate Better than orifice meterBetter than orifice meter
Flow nozzleFlow nozzle
Flow nozzleFlow nozzle
Flow nozzleFlow nozzle
Principle- Bernoulli’s theoremPrinciple- Bernoulli’s theorem SimpleSimple Used in higher velocities, difficult to Used in higher velocities, difficult to
maintain, costlymaintain, costly Used in gasesUsed in gases
Pitot tubePitot tube
Pitot tubePitot tube
Cylindrical probe inserted into fluidCylindrical probe inserted into fluid Velocity head converted into impact Velocity head converted into impact
pressurepressure Diff b/w static pressure & impact Diff b/w static pressure & impact
pressure- proptional to flow pressure- proptional to flow
By introduction of pitot tubeBy introduction of pitot tube
Pitot tubePitot tube
FeaturesFeatures
Easy to installEasy to install No pressure lossNo pressure loss Sensitive to up stream disturbanceSensitive to up stream disturbance Not used for sticky and dirty fluidsNot used for sticky and dirty fluids
Thank uThank u