viscousity unit engineering

8/10/2019 Viscousity Unit Engineering

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There are two related measures of fluid viscosity - known as dynamic(or absolute) andkinematicviscosity.

Dynamic (absolute) Viscosity

is the tangential force per unit area required to move one horizontal plane with respect to the

other at unit velocity when maintained a unit distance apart by the fluid.

The shearing stress between the layers of non turbulent fluid moving in straight parallel lines canbe defined for a Newtonian fluid as:

The dynamic or absolute viscosity can be expressed like

= dc/dy (1)

where

= shearing stress

= dynamic viscosity

Equation (1) is known as the Newtons Law of Friction.

In theSI systemthe dynamic viscosity units are N s/m2, Pa sor kg/m swhere

1 Pa s = 1 N s/m2= 1 kg/m s

The dynamic viscosity is also often expressed in the metric CGS (centimeter-gram-second)system as g/cm.s, dyne.s/cm2or poise (p)where

1 poise = dyne s/cm2= g/cm s = 1/10 Pa s

For practical use the Poiseis to large and it's usual divided by 100into the smaller unit called thecentiPoise (cP)where

1 p = 100 cP
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Water at 68.4oF (20.2

oC)has an absolute viscosity of one - 1 - centiPoise.

1 N s/m2= 1 Pa s = 10 poise = 1,000 milliPa s

Kinematic Viscosity

is the ratio of absolute or dynamic viscosity to density - a quantity in which no force is involved.Kinematic viscosity can be obtained by dividing the absolute viscosity of a fluid with it's massdensity

= / (2)

where

= kinematic viscosity

= absolute or dynamic viscosity

= density

In the SI-system the theoretical unit is m2/s or commonly used Stoke (St)where

1 St = 10-4m2/s

Since the Stokeis an unpractical large unit, it is usual divided by 100to give the unit calledCentistokes (cSt)where

1 St = 100 cSt 1 cSt = 10-6m2/s

1 m2/s = 1 x 104cm2/s =1 x 104stokes = 1 x 106centistokes

Since the specific gravity of water at68.4oF (20.2

oC) is almost one (1), the kinematic viscosity of

water at 68.4oFis for all practical purposes 1.0 cSt.

Viscosity and Reference Temperatures

The viscosity of a fluid is highly temperature dependent and for either dynamic or kinematicviscosity to be meaningful, the reference temperaturemust be quoted. In ISO 8217 thereference temperature for a residual fluid is 100

oC. For a distillate fluid the reference temperature

is40oC.

For a liquid - the kinematic viscosity will decreasewithhigher temperature

For a gas - the kinematic viscosity will increasewith highertemperature

Other Commonly used Viscosity Units


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Saybolt Universal Seconds (or SUS, SSU)

Saybolt Universal Seconds (or SUS) is used to measure viscosity. The efflux time is SayboltUniversal Seconds (SUS) required for 60 milliliters of a petroleum product to flow through thecalibrated orifice of a Saybolt Universal viscometer, under carefully controlled temperature and asprescribed by test method ASTM D 88. This method has largely been replaced by the kinematic

viscosity method. Saybolt Universal Seconds is also called the SSU number (Seconds SayboltUniversal)or SSF number (Saybolt Seconds Furol).

Kinematic viscosity versus dynamic or absolute viscosity can be expressed as

= 4.63 / SG (3)

where

= kinematic vicosity (SSU)

= dynamic or absolute viscosity (cP)

Degree Engler

Degree Engler is used in Great Britain as a scale to measure kinematic viscosity. Unlike theSaybolt and Redwood scales, the Engler scale is based on comparing a flow of the substancebeing tested to the flow of another substance - water. Viscosity in Engler degrees is the ratio ofthe time of a flow of 200 cubic centimetresof the fluid whose viscosity is being measured - to thetime of flow of 200 cubic centimetersof water at the same temperature (usually 20

oCbut

sometimes 50oC or 100

oC) in a standardized Engler viscosity meter.

Newtonian Fluids

Fluids for which the shearing stress is linearly related to the rate of shearing strain are designatedas Newtonian Fluids.

Newtonian materials are referred to as true liquids since their viscosity or consistency is notaffected by shear such as agitation or pumping at a constant temperature. Fortunately mostcommon fluids, both liquids and gases, are Newtonian. Water and oils are examples ofNewtonian liquids.

Shear-thinning or Pseudoplastic Liquids

Shear-thinningor pseudoplastic liquidsare those whose apparent viscosity decreases withincreasing shear rate. Their structure is time-independent.

Thixotropic Fluids

Thixotropic liquidshave a time-dependent structure. The apparent viscosity of a thixotropicliquid decreases with increasing time, at a constant shear rate.

Ketchup and mayonnaise are examples of thixotropic materials. They appear thick or viscous butare possible to pump quite easily.


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Acetaldehyde CH3CHO6168

16.120

0.3050.295

36

Acetic acid - vinegar - 10%

CH3COOH59 15 1.35 31.7

Acetic acid - 50% 59 15 2.27 33

Acetic acid - 80% 59 15 2.85 35

Acetic acid - concentratedglacial

59 15 1.34 31.7

Acetic acid anhydride(CH3COO)2O

59 15 0.88

Acetone CH3COCH3 68 20 0.41

Alcohol - allyl68

1042040

1.600.90cp

31.8

Alcohol - butyl-n 68 20 3.64 38

Alcohol - ethyl (grain)C2H5OH

68100

2037.8

1.521.2

31.731.5

Alcohol - methyl (wood)CH3OH

5932

150

0.741.04

Alcohol - propyl68

1222050

2.81.4

3531.7

Aluminum sulfate - 36%solution

68 20 1.41 31.7

Ammonia 0 -17.8 0.30

Aniline 68 20 4.37 40
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50 10 6.4 46.4

Asphalt RC-0, MC-0, SC-077

10025

37.8159-32460-108

737-1.5M280-500

Automatic crankcase oilSAE 10W

0 -17.8 1295-max 6M-max


0 -17.8 1295-2590 6M-12M


0 -17.8 2590-10350 12M-48M

Automatic crankcase oilSAE 20

210 98.9 5.7-9.6 45-58


210 98.9 9.6-12.9 58-70


210 98.9 12.9-16.8 70-85

Automatic crankcase oilSAE 50 210 98.9 16.8-22.7 85-110

Automotive gear oil SAE75W

210 98.9 4.2 min 40 min


210 98.9 7.0 min 49 min

Automotive gear oil SAE

85W

210 98.9 11.0 min 63 min


210 98.9 14-25 74-120

Automotive gear oil SAE140

210 98.9 25-43 120-200


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Automotive gear oilSAE150

210 98.9 43 - min 200 min

Beer 68 20 1.8 32

Benzene (Benzol) C6H63268

020

1.00.74

31

Bone oil130212

54.4100

47.511.6

22065

Bromine 68 20 0.34

Butane-n -5030

-1.1 0.520.35

Butyric acid n6832

200

1.612.3 cp

31.6

Calcium chloride 5% 65 18.3 1.156

Calcium chloride 25% 60 15.6 4.0 39

Carbolic acid (phenol)65

19418.390

11.831.26 cp

65

Carbon tetrachloride CCl468

10020

37.80.6120.53

Carbon disulfide CS23268

020

0.330.298

Castor oil100130

37.854.4

259-32598-130

1200-1500

450-600

China wood oil69

10020.637.8

308.5125.5

1425580


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Chloroform68

1402060

0.380.35

Coconut oil100

130

37.8

54.4

29.8-31.6

14.7-15.7

140-148

76-80

Cod oil (fish oil)100130

37.854.4

32.119.4

15095

Corn oil130212

54.4100

28.78.6

13554

Corn starch solution,22Baum

70100

21.137.8

32.127.5

150130

Corn starch solution,24Baum

70100

21.137.8

129.895.2

600440

Corn starch solution, 25Baum

70100

21.137.8

303173.2

1400800

Cotton seed oil100130

37.854.4

37.920.6

176100

Crude oil 48oAPI60

13015.654.4

3.81.6

3931.8

Crude oil 40oAPI60

13015.654.4

9.73.5

55.738

Crude oil 35.6oAPI60

13015.654.4

17.84.9

88.442.3

Crude oil 32.6oAPI60

13015.654.4

23.27.1

11046.8

Decane-n0

10017.837.8

2.361.001

3431
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Diethyl glycol 70 21.1 32 149.7

Diethyl ether 68 20 0.32

Diesel fuel 2D100130

37.854.4

2-61.-3.97

32.6-45.5-39


37.854.4

6-11.753.97-6.78

45.5-6539-48


37.854.4

29.8 max13.1 max

140 max70 max

Diesel fuel 5D 122160

5071.1

86.6 max35.2 max

400 max165 max

Ethyl acetateCH3COOC2H3

5968

1520

0.40.49

Ethyl bromide C2H5Br 68 20 0.27

Ethylene bromide 68 20 0.787

Ethylene chloride 68 20 0.668

Ethylene glycol 70 21.1 17.8 88.4

Formic acid 10% 68 20 1.04 31

Formic acid 50% 68 20 1.2 31.5

Formic acid 80% 68 20 1.4 31.7

Formic acid concentrated6877

2025

1.481.57cp

31.7

Freon -11 70 21.1 0.21


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104 40 0.32cp

Methyl iodide68

1042040

0.2130.42cp

Menhaden oil100130

37.854.4

29.818.2

14090

Milk 68 20 1.13 31.5

Molasses A, first100130

37.854.4

281-5070151-1760

1300-23500

700-8160

B, second100130

37.854.4

1410-13.2M660-3.3M

6535-611803058-15294

C, blackstrap100130

37.854.4

2630-55M1320-16.5M

12190-255M6120-76.5M

Naphthalene 176212 80100 0.90.78cp

Neatstool oil100130

37.854.4

49.727.5

230130

Nitrobenzene 68 20 1.67 31.8

Nonane-n0

100-17.837.8

1.7280.807

32

Octane-n0

100-17.837.8

1.2660.645

31.7

Olive oil100130

37.854.4

43.224.1

200
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Palms oil100130

37.854.4

47.826.4

Peanut oil100

130

37.8

54.4

42

23.4200

Pentane-n080

17.826.7

0.5080.342

Petrolatum130160

54.471.1

20.515

10077

Petroleum ether 60 15.6 31(est) 1.1

Propionic acid3268

020

1.52cp1.13

31.5

Propylene glycol 70 21.1 52 241

Quenching oil(typical)

100-120 20.5-25

Rapeseed oil

100

130

37.8

54.4

54.1

31

250

145

Rosin oil100130

37.854.4

324.7129.9

1500600

Rosin (wood)100200

37.893.3

216-11M108-4400

1M-50M500-20M

Sesame seed oil100130

37.854.4

39.623

184110

Sodium chloride 5% 68 20 1.097 31.1

Sodium chloride 25% 60 15.6 2.4 34
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220 1000Tomato Juice

SAE 50 Crankcase OilSAE 90 Gear Oil

440 2000 SAE 140 Gear Oil

1100 5000Glycerine (20oC)

SAE 250 Gear Oil

2200 10,000 Honey

6250 28,000 Mayonnaise

19,000 86,000 Sour cream

Centipoise(CPS)

Millipascalseconds(mPas)

Poise(P)

Centistokes(cSt)

Stokes(S)

SayboltSecondsUniversal

(SSU)

1 0.01 1 0.01 31

2 0.02 2 0.02 34

4 0.04 4 0.04 38

7 0.07 7 0.07 47

10 0.1 10 0.1 60

15 0.15 15 0.15 80

20 0.2 20 0.2 100

25 0.24 25 0.24 130


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30 0.3 30 0.3 160

40 0.4 40 0.4 210

50 0.5 50 0.5 260

60 0.6 60 0.6 320

70 0.7 70 0.7 370

80 0.8 80 0.8 430

90 0.9 90 0.9 480

100 1 100 1 530

120 1.2 120 1.2 580

140 1.4 140 1.4 690

160 1.6 160 1.6 790

180 1.8 180 1.8 900

200 2 200 2 1000

220 2.2 220 2.2 1100

240 2.4 240 2.4 1200

260 2.6 260 2.6 1280

280 2.8 280 2.8 1380

300 3 300 3 1475


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320 3.2 320 3.2 1530

340 3.4 340 3.4 1630

360 3.6 360 3.6 1730

380 3.8 380 3.8 1850

400 4 400 4 1950

420 4.2 420 4.2 2050

440 4.4 440 4.4 2160

460 4.6 460 4.6 2270

480 4.8 480 4.8 2380

500 5 500 5 2480

550 5.5 550 5.5 2660

600 6 600 6 2900

700 7 700 7 3380

800 8 800 8 3880

900 9 900 9 4300

1000 10 1000 10 4600

1100 11 1100 11 5200

1200 12 1200 12 5620


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1300 13 1300 13 6100

1400 14 1400 14 6480

1500 15 1500 15 7000

1600 16 1600 16 7500

1700 17 1700 17 8000

1800 18 1800 18 8500

1900 19 1900 19 9000

2000 20 2000 20 9400

2100 21 2100 21 9850

2200 22 2200 22 10300

2300 23 2300 23 10750

2400 24 2400 24 11200

2500 25 2500 25 11600

3000 30 3000 30 14500

3500 35 3500 35 16500

4000 40 4000 40 18500

4500 45 4500 45 21000

5000 50 5000 50 23500


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100000 1000 100000 1000 462000

125000 1250 125000 1250 578000

150000 1500 150000 1500 694000

175000 1750 175000 1750 810000

200000 2000 200000 2000 925000

Kinematic viscosity can be converted from SSU to Centistokes like

Centistokes= 0.226 SSU- 195 / SSU

where

SSU< 100

Centistokes= 0.220 SSU- 135 / SSU

where

SSU> 100

Viscosity and Temperature

Kinematic viscosity of liquids like water, mercury, oils SAE 10 and oil no. 3 - and gases like air,hydrogen and helium are indicated below. Note that

for liquids viscosity decreases with temperature for gases viscosity increases with temperature


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viscousity unit engineering

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