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Unformatted text preview: EML4304C Concept questions:
812C. How does the wall shear stress 1w vary along the ﬂow direction in the fully developed region in (a) laminar ﬂow and (b) turbulent ﬂow?
The can” shear stress (TM, VCMQiWS werml‘ «level We “NJ ollreclwn .‘A H»: Lila alewalofd reﬁt” 4L); lmirk lawnware
QWOL ‘l‘wf‘AWl9/%+ ‘Clow. 813C. What ﬂuid property is responsible for the development of the velocity boundary layer?
For what kinds of ﬂuids will there be no velocity boundary layer in a pipe? The {ilwa V;S(9Cll3 l5 {Cgrms;L\e ﬁr +M XeyqlaPWLQH ‘7; ﬁlm valdtila luauALILVJ 1L1zr, There MN be M we;th ‘0U(€f (5 Jrl/xﬁ ~Cla~d l5 {AI/Chat , 8l4C. In the fully developed region of ﬂow in a circular pipe, will the velocity proﬁle change
in the ﬂow direction?
Mo 815C. How is the friction factor for ﬂow in a pipe related to the pressure loss? How is the
pressure loss related to the pumping power requirement for a given mass ﬂow rate?
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2 Milka/£31, 1 WV“? 2 NAP“ “ /0 8—16C. Someone claims that the shear stress at the center of a circular pipe during fully developed laminar ﬂow is zero. Do you agree with this claim? Explain. \1 a 5
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atp ’\ 0E ( 0 at, i / Gettier : 0 8l7C. Someone claims that the shear stress at the center of a circular pipe during fully
developed turbulent ﬂow is zero. Do you agree with this claim? Explain. «as We ska» sluss off W9. SM‘QLcea Di 0»)?th ohm“: tuna oleuelprxnf
hamlet/d Elm.) is mud/hum 5mg w ska.» aims; :3 Prafarf.wl(
+0 ‘HAZ Velociillr j/dxje‘tf LQLLWC/l/k i5 Maxiiﬂum m‘l' “Hus, +«AQ SWI‘CILP? / 818C. Consider fully developed ﬂow in a circular pipe with negligible entrance effects. If the
length of the pipe is doubled, the head loss will (a) double, (b) more than double, (0) less than
double, (d) reduce by half, or (e) remain constant. 3‘wcer. \AL ; E12352 ) dpkhlsﬁ ‘HAQ [walla ciao.th
{fl/re, M US; 8l9C. Someone claims that the volume ﬂow rate in a circular pipe with laminar ﬂow can be
determined by measuring the velocity at the centerline in the fully developed region, multiplying
it by the crosssectional area, and dividing the result by 2. Do you agree? Explain. %e5~ ‘V‘ : Vm‘A . FW 37/” (6“18/ (‘L/VHX 7 ll/du3. “m” OCCU§ ot'i confer Ive, ’ ’;\/MQ\{
V :A, 820C. Someone claims that the average velocity in a circular pipe in fully developed laminar
ﬂow can be determined by simply measuring the velocity at R/2 (midway between the wall
surface and the centerline). Do you agree? Explain. N07. “(4'): ZVWB (\—%\ I [ref “0) ; VAUS aqaﬁ r.
vyﬁriv/ﬂlLét) Lzzci '_ﬁ HER ) :2 R7. ) 2 K7. ) TlMA/S Vow/3 ocgufs ml J}: L . 821C. Consider fully developed laminar ﬂow in a circular pipe. If the diameter of the pipe is
reduced by half while the ﬂow rate and the pipe length are held constant, the head loss will (a) double, (b) triple, (c) quadruple, (d) increase by a factor of 8, or (e) increaser by a factor of 16. k“; LEV”??? lLZVTLE: 14" D 15 (dwelt,
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’ P 3 M ‘ 3/10 822C. What is the physical mechanism that causes the friction factor to be higher in turbulent
ﬂow? IA thrloe‘\€n‘l' New) fl 3; ﬂag ikadmlv am;45 4kg +0 CAMwL£<£ Wilkins? ‘Hml (tuft? ‘llne £r:clﬁm father”
+0 lﬂQ lQV‘TXV‘ 823C. What is turbulent viscosity? What is it caused by?
Tamale/mt Vieoojhlng la; :5 Cwsex 95 ‘Ig/‘(ItclP/M'l‘ wares; am! ML. accau/ulé flat" wwwﬂm lrczmjfd/‘l lurblel 2106(85. it {s exWKﬁycaé k5 (Ti: 3 ~/0 UJVI =At if whgre (I E, He main Vqlqe gC V5lo(.‘%] [‘4
HM: “glow cllreclﬁm anal» Uv/ ckqu V’ “Ye. .{le‘I‘M‘l‘qu Wéomekﬁ ap V&[a(.¥7‘
824C. The head loss for a certain circular pipe is given by
92
hL=O.0826ﬂ;35— where f is the friction factor (dimensionless), L is the pipe length, ‘6’ is the volumetric ﬂow rate,
and D is the pipe diameter. Determine if the 0.0826 is a dimensional or dimensionless constant.
Is this equation dimensionally homogeneous as it stands? in MS (“uh of +kereFgre) RHS Musl’ MS tank's al‘ ClCck.‘
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SWLQ LH5 "3 Mi ollm;m01\¢llq CQ’KSZE'l‘OMT EH9} 1062.9 Mus‘l have Jilmwsims] w QKP/‘e $5.9,A \3 Vlo‘l‘ axiwtwsl‘d‘ﬂcf“? M‘LOCSWEO‘LJ, 825C. Consider fully developed laminar ﬂow in a circular pipe. If the viscosity of the ﬂuid is
reduced by half by heating while the ﬂow rate is held constant, how will the head loss change? __... ’— ’ L D Re. D D 11* fab; it a :5 mlmd t3 a m l... W ‘09 “Bird ‘13 Vii \ﬁ_QL—.!:,Q;LL~..V7’ ,CjiuLvy_ szaLV / 826C. How is the head loss related to pressure loss? For a given ﬂuid, explain how you would
convert head loss to pressure loss? inﬁll
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Allﬂiku 827C. Consider laminar ﬂow of air in a circular pipe with perfectly smooth surfaces. Do you
think the friction factor for this ﬂow will be zero? Explain. No, Due +0 46* uo_g(.'(\ ~HM241 will be A
VC\"CA{’8 if’wgum‘l‘ ad “We WOLHJWWOQ~ HMS a. shear" gifts;
in 'ku; ‘plw I 828C. Explain why the friction factor is independent of the Reynolds number at very large
Reynolds numbers. [Hr Vevg lapogg keTml£5 “WIMBGP5) 15 Marla cud the @Lcllm Qaciwr is Mia/JonaQewi" a“?
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HAL law/MIMI failvuler decreases w'd’k Marmara] Mm”;
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HMS Cage am ff‘ovhccmi M ﬂee Wtch ﬂaw Vim“AV la a WWW WW: «mm M m cm: Mm )
0% % law/«Mar éw‘o lat/(12$ \«LWKS Reﬂux;th Other problems 1. (837, C&C) Consider an air solar collector that is 1 m wide and 5 m long and has a constant
spacing of 3 cm between the glass cover and the collector plate. Air ﬂows at an average
temperature of 45 °C at a rate of 0.15 m3/s through the lmwide edge of the collector along the
5mlong passageway. Disregarding the entrance and roughness effects, determine the pressure
drop in the collector. Answer: 32.3 Pa 5
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.05925/ M“; QWV M35212; M, :15 gr PM
M/‘f' Jﬁw’ $3: ) APL : 32.25 FKJ 2. (841, C&C) Air enters a 7mlong section of a rectangular duct of cross section 15 cm x 20
cm made of commercial steel at 1 atm and 35 °C at an average velocity of 7 m/s. Disregarding the entrance effects, determine the fan power needed to overcome the pressure losses in this
section of the duct. Answer: 4.9W d/y/‘VW
20 ——~— A 7MB f LHS ﬁ/ﬁ
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W = Lt m w) 4/10 7/I0 3. (846, C&C) Glycerin at 40 °C with p = 1252 kg/m3 and ,u = 0.27 kg/ms is ﬂowing through a “he San—Wm horizontal smooth pipe with an average velocﬁ'WT‘ﬁj m/s. Determine the
pressuréxiglgpjper 10 m of the pipe. Ra: Pig 1 [mrzﬁxaﬁﬂénwﬂ I .2?! 93/5”?
RNA.) LG i02er mu) 5:3 {1: aki/tC—y ’ 07%€'7 Z Foi‘lbm) :Q'Lsk f 2 21: (315m/Sjl
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Ar 110,103 MA ’61?“ )6 (3% 4. Water ﬂows in a horizontal constantarea pipe. The pipe diameter is 40 mm and the average
ﬂow speed is 2.0 m/s. At the pipe inlet the gage pressure is 450 kPa, and the outlet is at
atmospheric pressure. a) Determine the head loss in the pipe. Frm 61.46111 whom, him»? 1 Mai/[4,711 : 0 (Em f‘ol> , 1
f3 ""+%I“/T;)"*'°‘zvl~_+gz. +l\i Mét=0 ) “‘6' tr? “ié’ 84°C., f: m:
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“L: _ “50% 10009.: )0“ 5w ikh : b) If the pipe is now aligned so that the outlet is 30 m above the inlet, what will the inlet
pressure need to be to maintain the same ﬂow rate? J.“ ‘lkl‘l’ 0)) lL ‘5 £RQ ‘l'n vl5w3:¥o_:¥ 'IS QMG) hL JJVL‘i’o VlScaSX‘i‘g L5 5M€r LL : P41; '22
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If the pipe is now alig®o that the outlet is 30 m below the inlet, what will the inlet pressure
need to be to maintain the same ﬂow rate? For Y110 7‘ : (Lg at)“ :05. 7éy~3ﬂﬂ)* tﬁtﬁﬂmg, M 24.? ﬁt if tea/id my
zRT lSéSkQL ‘ d) How much lower than the inlet must the outlet be so that the same ﬂow rate is maintained if
both ends of the pipe are at atmospheric pressure? \>\‘—‘?1
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$1: ’kL ‘7/0 5. At the inlet to a constantdiameter section of the Alaskan pipeline, the pressure is 8.5 MPa
and the elevation is 45m; at the outlet the elevation is 115 m. The head loss in this section of
pipe is 700 m. Calculate the outlet pressure. Use 0.9 for the speciﬁc gravity of crude oil. f? ~‘l/7Ma " .‘Tt CH? “3&3 Fm emern when? kfuuiqaz Limit” " °<«Ul : “2U; L+‘Z:E’L/+2Z+L\L m ' M.
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(g’i “11;: 433..) ‘( HOV235 * gagf'x’lr 77am @‘MW :5» or Plus and Gait/m: @uaéiwadvj ﬂow 01" watt/ 793m {amt ﬁhown. AO“ 05. 1.11:2 :A2. T Raid: (0.) Fiona rate: at {40.57‘62/11" show/3, (A) Howl Could deafrm x'mpm ued :9 I L Assmph'aas: (I) 19, 279,: spam “'3. Eur mm Cow/ﬂaw, {2,4, = 12,4le 0;: L7: (gatmd p: .afz‘szzﬁﬂag a = Vzm = wagerd prim, . .... .. ._ (2.) ..
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a 793 .s _ 149m} 1" fwtal #318! . (14.29pm) a How; EML4304C 1. Water ﬂows through a 60 mm diameter tube that suddenly contracts to 30 mm diameter. The
pressure drop across the contraction is 3.4 kPa. Determine the volume ﬂow rate. M59, $31) 5LLL£€M coni’rocc+:m 40 $61. KL
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W 22 “3}” 2/7 ‘Q: 0.0m “75‘ 2. A pipe friction experiment is to be designed, using water, to reach a Reynolds number of
125,000. The system will use 2.5 inch smooth PVC pipe from a constanthead tank to the ﬂow
bench and 50 ft of smooth 1 inch PVC line mounted horizontally for the test section. The water
level in the constanthead tank is 2.0 ft above the entrance to the 2.5 in PVC line which is
connected to the 1 inch line. Determine the required average speed of the water in the 1 inch pipe. Assume T = 70°F.
Calculate the pressure difference expected between taps 12 feet apart in the horizontal test
section. Please work this problem using English units. Do not convert to SI. Comment on the
feasibility of using a constanthead tank. A «NW2 1:
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M 2.x. 511 M, qm 19+ ff: mm; he, Jr.” M 3. A hydraulic press is powered by a remote highpressure pump. The gage pressure at the
pump outlet is 22 MFA, whereas the pressure required for the press is 21 MPa (gage), at a ﬂow
rate of 0.029 m3/min. The press and pump are connected by 55 In of stainless steel tubing. The
ﬂuid is SAE 10W oil at 40 C. Determine the minimum tubing diameter that may be used. ) 7MP ‘._mmwm_m.ri:rm——m_w,_::ﬁm :th Eﬂ€'&a 86.1 P; w? hr + ,+£1 >3 ELAN/L +"(nf +‘n
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 Summer '09
 ABBITT
 Velocity, head loss, circular pipe

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