Viscometry and Types of industrial Viscometers

Important liquid foods property

1. ◾Viscosity
Definition
FormulaandUnits
◾Viscometer
Introduction
Importance
◾TypesofViscometer
5
CONTENTS

2. ◾Afluidflowproperty.
◾Internalpropertyofafluid
thatoffersresistancetoflow.
◾Itisameasureofhoweasilya
fluidcanflow.
◾Itcanalsobeviewedasa
resistancetoshearforce,
moreviscousthefluidis,
highertheresistance.
VISCOSITY
6

3. ◾Formula:
Viscosity=shearstress
shearrate
◾SIunit:
Theunitsofviscosityis:
pious
centi-pious
FORMULA&UNITS
7

4. ◾Definition:
“Aviscometerisaninstrumentused tomeasure
theviscosityofafluid.”
◾Itisalsoknownas“Viscosimeter.”
◾Viscometeronlymeasuresunderoneflow
condition
◾Themeasureoftheresistanceistakenby
measuringthedragresistanceduringrelative
motionthroughthefluid.
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VISCOMETER

5. ◾Measuringviscosityisimportantwhen
consideringprocessconditionsformaterials
thatneedtobepumpedorpiped.Iteffects
dippingandcoatingperformance,whichis
particularlyrelevanttosyrupsandlotions.
◾Viscometercanbeusedtomonitorbatch
consistencyandqualitycontrol.
◾Theyarealsousedtocharacterizeplastics.
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IMPORTANCE

6. TYPESOFVISCOMETER
Capillaryviscometer
Fallingandrisingbody
apparatus
Rotationalviscometer
10

7. ◾Introduction:
Theseviscometersaresuitableforonly
Newtoniansystems.
◾Principle:
CAPILLARYVISCOMETERbasedon
Poiseuille’slaw.
Thismethodofmeasurement,
measurestimetakenfordefined
quantityoffluidtoflowthrougha
capillarywithknowndiameterand
length.andisthencomparedwithtime
requiredtoflowbyaliquidofknown
viscosity(usuallywater)
CAPILLARYVISCOMETER
11

8. Ifη1andη2aretheviscositiesofunknownandstandardliquid
,ρ1andρ2aredensitiesandT1andT2aretimerequiredto
flowinsecthen;
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η1/η2=ρ1t1/ρ2t2 .
η1/η2=RELATIVEVISCOSITYOFLIQ.
Theaboveeq.isbasedonPOISEUILLE’SLAWforliq.Flowing
throughcapillarytube.
η=πr⁴tΔP/8lV
Where,
r=radiusofinsidecapillary
t=timeflow
ΔP=Pressureunderwhichliq.Flow
L=lengthofcapillary
V=Volumeoffluidflowing
Thise.qcanalsobewrittenas
η=KtΔP k=constant
FORMULA

9. Ostwald’sviscometer
Suspendedlevel
viscometer
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TYPEOFCAPILLARYVISCOMETER

10. ◾Ostwald’sviscometeralso
knownasU-tubeviscometer
◾Adevicewhichisusedto
measuretheviscosityofthe
liquidwithaknowndensity.
◾Thisdeviceisnamedafter
“WilhelmOstwald”.
OSTWALD’SVISCOMETER
14

11. ◾Theviscometerisfilledwithliq.Upto
bulkAthrough1
st
arm.
◾Thensucktheliq.Through2
nd
armto
upperpointCofthebulk
B.
◾Nowallowtheliq.Topassfromupper
markedCtolowermarkedD.
◾Andnotethetimeofflowfromupper
markedCtolowermarkedD.
◾Nowtheviscosityofliq.Canbe
calculatedbyusingformula;
η1/η2=ρ1t1/ρ2t2
WORKINGPRINCIPLE
15

12. ◾Itisamodifiedformof
Ostwald’sviscometer.
◾Init,thereisthirdvertical
armattachedtothebulb
belowthecapillarypartof
therightarm.
◾Liquidisintroducedintothe
viscometerthroughtheleft
armInquantitysufficientto
fillthebulbintheleftarm.
UBBELOHDESUSPENDEDLEVEL
VISCOMETER
16

13. OTHERTYPESOFCAPILLARY
VISCOMETERS
17

14. Advantages Disadvantages
Nosingletubeis
suitableforall
viscosities
Basicmodelscanonly
beusedfortranslucent
fluids
Difficulttocleanthe
capillarytubes
ADVANTAGES&DISADVANTAGES
Measureprecise
viscositiesformany
diversefluids
Small$Portable
Inexpensive
Easytouse
Canuseawideverityof
capillarytubesonthe
sameviscometer
18

15. FALLINGSPHERE
VISCOMETER
RISINGSPHERE
VISCOMETER
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FALLING&RISINGBODYAPPARATUS

16. ◾INTRODUCTION:
Fallingsphereviscometeris
suitableforNewtoniansystems.
◾PRINCIPLE:
Stoke’slawisthebasisofthe
fallingsphereviscometer,in
whichthefluidisstationary.
Stoke’slaw:
“Itstatesthatwhena
bodyfallsinviscousmedia,it
experiencesaresistancewhich
opposethemotionofthefluid.”
FALLINGSPHEREVISCOMETER
20

17. ◾Thesample&ballareplacedin
theinnerglasstube&allowedto
reachtemperatureequilibrium
withthewaterinthesurrounding
constanttemperaturejacket.
◾Thetubeandjacketarethen
inverted.Whicheffectively
placedtheballatthetopof
innerglasstube.
◾Thetimefortheballtofall
betweentwomarksisaccurately
measuredandrepeatedseveral
time.
WORKING
21

18. ◾Viscousdragonbody=forceresponsibleforthedownward
movement,thus:
3пηdv=п/6d³gxPs–P1
where,
D=diameterofthesphere
g=accelerationduetogravity
v=terminalvelocity
Ps=densityofsphere
P1=densityofliquid
byrearrangingformula:
η=d²g(Ps–p1)/18v
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FORMULA

19. ◾HOEPPLERBALLVISCOMETER:
Itisafallingballinstrumentwhichusesashort,nearly
verticalglasstubeoflargediameterandcloselyfittingball
ofeithersteelorglass.
Thesampleandtheballareloadedintotheinnercylinder
andbroughttothetemperatureofmeasurementbymeans
ofaconstanttemperatureouterjacket.
Theloadingpinisreleasedandtheapparatusisinvertedto
placetheballintheinitialstatingposition.
Thetimefortheballtotransversethedistancebetween
twomarksismeasured
Aminimum30sectimeisusedforbestresult.
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EXAMPLE

20. ◾Risingsphereviscometerisalso
namedasRheometer.
◾Itisanimportantinstrumentto
studytheyieldvalueofNon–
Newtoniansystems.
◾Init1.9cmdiameterstainless
steelsphereconnectedtoastrain
gauzeviaaplatinum-rhodiumwire
isliftedthroughthematerialunder
testataveryslowratebyamotor
drivenarm.
◾Theshearingstresscausedby
straininthegelstructureis
recordedcontinuously.
RISINGSPHEREVISCOMETER
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21. Highsheardevices,
Thisisincredibly
importantwhen
dealingwithnon-
Newtonianfluids
whichincludesmost
ofthefluidsusedin
printingandcoating
today.
ADVANTAGES DISADVANTAGES
Canbemaintenance
intensive
Canbepartsintensive
Replacementpartscan
becostly
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FALLING&RISINGBODYAPPARATUS

22. INTRODUCTION:
Theseviscometersaresuitableforboth
Newtonianandnon-Newtoniansystems.
Amongstthemostwidelyusedmeter
PRINCIPLE:
Basedontheprinciplethatthefluid
whoseviscosityisbeingmeasuredis
shearedbetweentwosurfaces.Inthese
viscometeroneofthesurfaceisstationary
andotherisrotatedbyanexternaldrive
andfluidfillsthespaceinbetween.The
measurementsareconductedbyAppling
eitheraconstanttorqueandmeasuringthe
changesinthespeedofrotationorapplying
aconstantspeedandmeasuringthe
changesinthetorque.
ROTATIONALVISCOMETER
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23. TYPES
Cupandbob
viscometer
Searletype
viscometer
Stormer
viscometer
Brookfield
viscometer
Couettetype
viscometer
MacMicheal
viscometer
Coneand
Plate
viscometer
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24. ◾Itisconsistoftwocoaxial
cylindersofdifferent
diameters.
◾Theoutercylinderforms
thecupintowhichtheinner
cylinderorbobisfixed
centrally.
◾Thetorquesetupinthebob
ismeasuredintermsof
angulardeflectionQofa
pointerthatexhibitonthe
scale.
CUPANDBOBVISCOMETER
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25. TYPES
◾Twotypesofinstrumentexistdependingon
whetherthecuporthebobrotates.
Couettetype
viscometer
Searletype
viscometer
29

26. ◾Inthisthecupisrotatedand
theviscousdragonthebob
producedbytheliquid
resultsinatorquewhichis
proportionaltotheviscosity
oftheliquid.
◾Example:
MacMichaelviscometer
COUETTETYPEVISCOMETER
30

27. η=KM/w
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FORMULA

28. ◾Insearletypeviscometer,thebobisrotated
whilethecupisheldstationary.
◾Examples:
Stormerviscometer
Brookfieldviscometer
SEARLETYPEVISCOMETER
32

29. η=kvw/v
33
◾Where
◾Kv=instrumentconstant
◾W=weightingram
◾V=rpmgeneratedduetow
FORMULA

30. ◾Acone-plateisprecisetorquemeterwhichdrivenasdiscrete
rotationalspeed.
◾Thetorquemeasuringsystemwhichconsistofacalibrated
berylliumcopperspringconnectingthedrivenmechanismto
rotatingcone,senseofresistancetorotationcausedby
presenceofsamplefluidbetweentheconeandstationaryflat
plate.
CONEANDPLATEVISCOMETER
34

31. ◾ViscosityinpiosesofaNewtonianliq.Is
calculatedbyeq.
h=CT/v
Where
Cisaninstrumentconstant
V=speedofconeinrevolution/min
T=torqereading
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FORMULA

32. Canmeasureviscosities
ofopaque,settling,or
non-Newtonianfluids.
Usefulforcharacterizing
shear-thinningandtime-
dependentbehavior.
Speedoftherotatingpart
easilyadjusted.
Oftenlinkedto
computersforsemi-
automatedmeasurement.
ADVANTAGES DISADVANTAGES
Canberelatively
expensive.
Oftenlargeandnot
portable.
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ROTATIONALVISCOMETER

33. ◾Vibrationalviscometers
◾Bubbleviscometers
◾Oscillatingviscometers
◾Orificeviscometers.
◾StabingerViscometers
◾Electromagneticallyspinningsphere
viscometer(EMSV)
◾Rectangular-slitviscometers
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OTHERTYPESOFVISCOMETERS