MEL1(2)

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MEL 411:

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The cours e involv e s t he study andm e asur e m e nts of t he prop e rtie s of liquid fu e ls.It d e als wit h the m e asur e m e nt fu e ls pr e ssur e, te mp e ratur e le ve l, flow , sp ee d , we ig h t , ar e a , volum e, viscosity , st e am quality and products of combustion. It also includ e s t he study and

analysis of fu e ls and lubricants.

virn e_ dalisay@ya h oo.com

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VISCOSITY - the fluid r e sistanc e to s he ar or flow- a m e asur e of t he ad he siv e/ co he siv e or frictionalfluid prop e rty

APPLICATION:

- nee de d for prop e r d e sign of r e quir e dte mp e ratur e s for storag e, pumping or inj e ction of fluids


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TWO RELATED MEASURES OF FLUID VISCOSITY

ABSOLUTE (D Y NAMIC) VISCOSITY - is a m e asur e of t he int e rnal r e sistanc e- is t he tang e ntial forc e pe r unit ar e a r e quir e d tomov e on e h orizontal plan e with re sp e ct to t he

ot he r at unit v e locity w he n maintain e d a unitdistanc e apart by t he fluid- the ratio of s he ar int e nsity to v e locity gradi e nt


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Formula:

= dc/dy where:

shearing stress dynamic viscosity

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UNITS OF MEASUREMEN TSSI syst e mN-s / m 2

Pa -skg / m -s

CGS syst e m g/cm-sdyne - s/cm 2

poise (p)


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Conv e rsion:1 poise = dyne-s/cm 2

= g/cm-s

= 1 / 10 Pa-s= 100 cp (centipoise)

Constant:absolute viscosity of water (68.4F = 2 0 .2C)

= 1 cp


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K INEMATIC VISCOSI TY - is t he ratio of absolut e or dynamic viscosity to t he mass d e nsity of fu e ls

Formula: = /

where:

- kinematic viscosity - absolute or dynamic viscosity - density


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SI syst e mm 2 / sS toke ( S t)1 S t = 10 -4 m 2 /s

= 100 cS t (centistokes)1 cS t = 10 -6 m 2 /s

Constant:

kin e matic viscosity of wat e r (68.4 oF) - for all practicalpurpos e s= 1 .0 cS t.


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Othe r Commonly us e d Viscosity Units

Saybolt Univ e rsal S e conds ( SSU )

- is us e d to m e asur e viscosity- The e fflux tim e is Saybolt Univ e rsal S e conds ( SUS ) re quir e d for 60millilit e rs of a p e trol e um product to flow t h roug h the calibrat e d orific e of aSaybolt Univ e rsal viscom e te r

Re lations h ip of kin e matic and dynamic viscosity = 4.63 / SG

where:

v kinematic viscosity, SSU

dynamic viscosity, CpSG

specific gravity


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VISCOSITY OF COMMON LIQUIDS


Typical liquid Saybolt S e condUniv e rsal( SSU )

ce ntiStok e s(cS t)

Wat e r (20 oC) 31 1

MilkSAE 20 Crankcas e OilSAE 75 G e ar Oil

40 4.3

# 4 FUEL OIL 80 15.7

SAE 30 crankcas e oilSAE 85 GEAR OIL

500 110

SAE 90 GEAR OIL 1000 220

SAE 140 GEAR OIL 2000 440

SAE 250 GEAR OIL 5000 1100

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Probl e m:

Calculat e the absolut e viscosity of air at 1 bar and 40C , kin e matic viscosity of 16.97cSt.

Give n:P = 1 bar

T = 40C

cSt = 16.97

Solution:

= p / R T

= ( 10 5 N /m 2 ) / ((287 J/kg/K) (273 oC + 33 0 C)

= 1 .11 3 kg/m 3

Absolute viscosity is,

= ( 1 .11 3 kg/m 3 ) ( 1 6.97 10 -6 m 2 /s)

= 1 .88 10 -5 kg/m s


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Conv e rt kin e matic viscosity from SSU tocSt.

cS t = 0 .226 SSU - 1 9 5 / SSU

SSU < 100


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cS t = 0 .22 0 SSU - 1 3 5 / SSU SSU > 100


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For liquids - viscosity d e cr e as e s wit h te mp e ratur e

for gas e s viscosity incr e as e s wit h te mp e ratur e


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Probl e mA solid circular cylind e r slid e s insid e a v e rtical smoot h pip e .The spac e be twee n t he cylind e r and t he pip e is lubricat e dwith an oil film. Calculat e the te rminal v e locity of t he cylind e r.


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Solution

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BOARD WORK

Probl e mA cylindrical tank mad e of st ee l is 6 ft long and 1.5 m in diam e te r. Ane ngin e h as fu e l rat e consumption of 1000 g / min at 27 API fu e lsp e cific gravity. D e te rmin e the numb e r of days t he tank can supplythe e ngin e?

Give nm fu e l = 1000 g / minAPI = 27h = 6 ftd = 1.5 m

Re quir e m e ntNo.of days


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BOARD WORK

SolutionVfu e l = m fu e l / de nsity fu e l

Vf = Vt = 3.23 cu.m

d e nsity fu e l = SG 15.6 C (d e nsity wat e r)

= 0.893 (1000 kg / cu.m)

= 893 kg / cu.m

Vfu e l = 60 kg /h r / 893 kg / cu.m

= 0.067 cu.m /h r

# of h rs = 3.23 cu.m / 0.067 cu.m /h r

= 48.21 h rs

# of days = 2 days


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H ydrom e te r

- a d e vice us e d for m e asuring som e ch aract e ristics of a liquid suc h as itsde nsity and sp e cific gravity.


Application

The d e vice consist of a w e ig h te d , s e al e d , and long -n e ck e d glass tub e th at is imm e rs e d in t he liquidbe ing m e asur e d (www.britannica.com) .

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MEL1(2)

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