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8/3/2019 J Du Preez-15063518-Review of Li Et Al
1/7
Rou
Heat
hness
ransfe
Depar
Enhanc
ment of
ed Mec
i Xiao-wei,
Jacqu
1
echanic
Stellenb
13
eview
hanism
eng Ji-an,
es du Pr
063518
l and M
sch Uni
ay 2011
for Tur
Li Zhi-xin
ez
chatroni
ersity
bulent
Enginee
onvec
ring
ive
8/3/2019 J Du Preez-15063518-Review of Li Et Al
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R
The recenhance
roughne
This viscfluid whemaintain
The condimensiThree sdependiFigure 1being e,the four t
Figure 1:
Table 1: R
The frictReynold
changinis followreferencwhere aindicatiorelationmaximuas illustr
ughness
ntly publisment at the
s to two or
ous sublayre turbulentthe fluid in l
clusion wanal roughnts of experig on the tshows theroughnessubes are gi
wo dimensio
oughness di
ion factorsnumbers
the workind for the fofor the ra
ter the diffof the rat
to the smratio for a
ted in Figu
nhanced
hed articlesame pum
three times
r is in the vifluctuationsaminar moti
s establishss tubes w
ments weremperatureeneral formidth, w anden in Table
nal roughnes
ensions of t
and Nussel(by changi
g fluid tempur differenttios of theerence in
of changeoth tube cspecific Re 2, Li et al.
mechanis
by Li etping power
that of the v
cinity of theare dampe
on.
ed by expith dissimilaconducted
of the workof the tworoughness1.
s tube (Liet
e four tubes
t numbersg the flow
erature speroughness triction factagnitudefor the Nusase and thynolds num(2011:177
1
for turb
l. (2011) ccould be a
iscous subl
wall of theby viscou
rimentallyr roughnesswith differeing fluid. Fimensional
pitch is illus
l. 2011:1776)
(Li et al. 2011
were firstrate) for th
cified in Liubes. The rrs and Nuan easilyselt numbeerefore, onber. Plottin) a conclusi
lent conv
oncluded tchieved by
yer thickne
pipe whereshear forc
determininheights att Prandtl nur tubes w
l roughnesstrated by th
:1776)
easured ine three dif
t al. (2011:esults of thselt numbee observe
rs of the dife could e
these ratiion can be
ective he
at maximuincreasing
ss.
there is vers becomin
the heatdifferent Reumbers forere used intube. The re letter P. T
a smoothferent Pran
1777)). Thesmooth tu
rs for the r. This is
ferent rougsentially ds to its Rerawn, that
t transfer
m heat trahe height
thin layerlarge enou
transfer inynolds numhe workingthe experiughness h
he dimensi
tube at diffdtl number
same proce are used
oughness tlso a signiness casetermine aynolds numor tubes nu
nsferf the
f thegh to
twobers.fluid,ent.ight,
ns of
erent(by
dureas abes,icantwith
localbers,mber
8/3/2019 J Du Preez-15063518-Review of Li Et Al
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1, 2 and80000,3numberquickly
Figure 2:
Using thdeterminthat of th170% met al. 201
Figure 3:
Li et al. (the rougbeen imwith reg
3, there exi000 and 24, the Nusith the incr
usselt numb
same mete the amoue smooth tre for num1:1779).
riction facto
2011:1779)hness heigroved andrd to the us
ists a maxi0000 for roselt numbease of Rey
er ratios at di
od, frictionnt of timesbe. The floer 2, 360%
ratios at diff
furthermoret, at a setenhancede of alterna
um Nusselghness tuis initially
olds numb
ferent Reyno
factor ratioby which thw friction infor number
rent Reynold
comparedReynolds nby includinive Reynol
2
t number raes numberhigh, at lor.
lds numbers
were alsoe friction facrements w3 and appr
s numbers (L
he Nusseltumber (Re
an additios numbers
tio at differ1,2 and 3er Reynol
Li et al. 2011
plotted in thctor of the ras found toximately 1
i et al. 2011:1
number rati= 20000).nal discussthat also re
nt Reynoldrespectivelds number
:1778)
e same maoughness tbe 50% mtimes mor
779)
os and frictihis compa
ion and illuulted in a
numbers () whilst for, but decr
ner (Figurebes differsre for numfor number
n factor ratrison couldtrations thaximum N
Re =tubeases
3) tofromer 1,4 (Li
ios tohavereof,sselt
8/3/2019 J Du Preez-15063518-Review of Li Et Al
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numberand Figobservata greate
The pres
From thfactor inthe presbetweenopposed
by usingevaluateratio to t
Figure 4:
ratio, as isre 5. Wh
ion can bechange in
sure drop r
above eqreases. Thi
sure drop.enhancingto a decrea
a Performat the sae power of
usselt numb
pparent inn the rateade, that
he friction f
lation is giv
ation, it iss is an undTherefore, tthe heat trse in the pr
ance Evalue pumpinga third.
r ratios for di
Figure 2. Tof variation increasinctor than in
en by:
evident thasired outc
here existsansfer to assure drop,
ation Criterpower, by d
fferent rough
3
he two diffn of bothg roughnesthe heat tr
2
t the pressme, becauthe necescertain deor vice ver
ion (PEC) iividing the
/
ness heights
rent compaigures is theight fro
nsfer enha
ure drop wie more enity for a c
gree (by ina. Li et al. (
n which husselt num
at Re = 20,00
risons areaken into
0.37mm tcement.
ll increasergy is requrtain trade
creasing th2011) appr
at transferber ratio by
(Li et al. 201
iven in Figccount, a0.68mm,
hen the frired to overoff to be
roughnesached this
enhancemthe friction f
1:1778)
ure 4clearields
ictionomeade,
s) asissue
nt isactor
8/3/2019 J Du Preez-15063518-Review of Li Et Al
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Figure 5:
The comparithe exepfrom the
UndoubtconclusiThis mean increbelow. Tof the he
Figure 6:
With turthicknestransferis smalleproducetimes thpressuresublayersubstant
Roughn
easily uundergris used,more suf
The metparamoureached,
riction facto
is plottedon, the opttion of tubee measure
edly, then that thens that these of the P
his occuranat conducti
EC variance
ulent flow,of the heill not be e
r than the van optimalviscous sudrop. Whethickness,
ially.
ess Enhan
derstandaduate heatfor examplficiently.
hods of thnt way in w
is appare
ratios for dif
against theimum Reynnumber 4,
ents.
ost importPEC doesre is an optrandtl numce can be an layer.
with roughne
the Prandt conducti
nhanced aniscous sublperformancblayer thick
the roughheat transf
ed Mechan
le style, wtransfer cla, viscous
authors,hich to apprnt from th
erent roughn
Reynoldslds numbehich had a
nt figure cot neccessimum rougher also en
scribed to t
ss height for
l number in layer is
the pressyer thickn
e when theess. This eess heightr is hardly
ism for Tu
hich makes, althoughublayer a
y which thoach the reeir work.
4
ess heights a
umber atrs are founsmall optim
ontained inarily increaness heighances heate fact that
ifferent Pr at
always gmaller thare drop willss. Li et al.roughness
nhances heis approximenhanced f
bulent Con
it accessiit is my cond the hea
ey reachedlevant problhis means
t Re = 20,000
ifferent Prfor the dif
um Reynol
the articlee with rout for a settransfer, whe Prandtl
Re = 20,000
reater thanthe visco
not increas(2011) conheight is
at transferately five tiurther and
vective He
ble and ctention thatconductio
their findiem and the
that any
(Li et al. 2011
ndtl numbeerent roughs number a
is Figurehness heigeynolds nu
ich is illustrnumber affe
Li et al. 2011:
unity. Thiss sublayer.
e when thecluded thatqual to apithout a noes greater
he pressur
t Transfer
mprehendisome of thelayer sho
gs are, inultimate coperson wi
:1779)
rs and froness tubes,nd was excl
6, in whicht, was reamber. Moreted in the f
cts the thic
1780)
entails thaTherefore,
oughness hroughnessroximatelyiceable effthan the vi
drop incr
is written
le, even fterminologuld be expl
my opinionnclusion whh an aca
this, withuded
thehed.
over,igureness
t theheateightubesthreect oncousases
in an
r anthatined
, theich isemic
8/3/2019 J Du Preez-15063518-Review of Li Et Al
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5
background, knowledge or experience in the field of heat transfer who may assess the datawhich that Li et al. (2011) procured, would come to make the exact same conclusion.
Although this work builds upon the work of Nikuradse (1950) and there exist various similararticles, such as that of Ceylan & Kelbaliyev (2003). This article is useful for the satisfaction ofan enquiry regarding the optimum roughness height for utilization in practical applications to
increase the heat transfer without losing too much pressure head, for example, in a car radiatordesign or an industrial heat exchanger. Therefore, this article makes a valuable contribution tothe field of heat transfer.
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6
References
Ceylan Kadim & Kelbaliyev Gudret, The roughnesseffects on friction and heat transfer in thefully developed turbulent flow in pipes, Applied Thermal Engineering 23 (2003) 557570
Li Xiao-wei, Meng Ji-an, Li Zhi-xin, Roughness enhanced mechanism for turbulent convectiveheat transfer,International Journal of Heat and Mass Transfer 54 (2011) 17751781
Nikuradse, J., 1950, Law of Flow in Rough Pipes,Technical memorandum 1292, NationalAdvisory Committee for Aeronautics; Translation of Stromungsgesetze in rauhen Rohren, VDI-Forschungsheft 361. Beilage zu Forschung auf dem Gebiete des Ingenie urwesens AusgabeB Band 4,July/August 1933.