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Astract
"his stud& e%aluates the %ehicle e>haust ?aste heat reco%er& (@H) otential using a
anine c&cle (C)0 "o this end, oth a C thermod&namic model and a heat e>changer
model ha%e een de%eloed0 Both models use as inut, e>erimental data otained 'rom
a %ehicle tested on a chassis d&namometer0 "he thermod&namic anal&sis ?as er'ormed
'or ?ater, 124 and 2-7'a and re%ealed the ad%antage o' using ?ater as the ?oring
'luid in alications o' thermal reco%er& 'rom e>haust gases o' %ehicles euied ?ith a
sar/ignition engine0 Moreo%er, the heat e>changer e''ecti%eness 'or the organic
?oring 'luids 124 and 2-7'a is higher than that 'or the ?ater and, conseuentl&,
the& can also e considered aroriate 'or use in %ehicle @H alications through
Cs ?hen the e>haust gas temeratures are relati%el& lo?0 changer,
the simulations re%ealed increases in the internal comustion engine thermal and %ehicle
mechanical e''iciencies o' 10-/4072 and 1013/170.7, resecti%el&, ?hile 'or a
shell and tue heat e>changer, the simulations sho?ed an increase o' 087/102 in the
thermal e''icienc& and an increase o' 203-/30.3 in the mechanical e''icienc& 'or an
e%aorating ressure o' 2 M+a0 "he results con'irm the ad%antages o' using the thermal
energ& contained in the %ehicle e>haust gases through Cs0 ander
de%ices allo?ing 'or higher e%aorating ressures are reuired to otain the ma>imum
@H otential 'rom %ehicle C s&stems0
!ey"ords5 ?aste heat reco%er&: anine c&cle: ?oring 'luid: thermod&namic
e''icienc&: heat e>changer0
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#o$enclature
A area m2F
A/F airG'uel ratiob long side o' a rectangular cross section mFcp heat caacit& g/1 I /1Fd diameter mFDh h&draulic diameter mF´ E e>erg& 'lo? rate @F
f Darc& 'riction 'actor F imosed load JFh seci'ic enthal& g/1F: heat trans'er coe''icient @ m/2 I /1F
́I e>erg& destruction rate @F
k thermal conducti%it& coe''icient @ m/1 I /1FL e%aorator tue length mFLHV lo? heating %alue M g/1F
ḿ mass 'lo? rate g s/1F
N engine seed rmFNt tues numerNu Jusselt numer p ressure +aFP %ehicle e''ecti%e o?er @FPr +randtl numer
Q́ heat rate @F
Rd 'ouling 'actors m2
I @/1
FRe e&nolds numer T temerature IFU o%erall heat trans'er coe''icient @ m/2 I /1Fv seci'ic %olume m4 g/1FV %ehicle seed m h/1F
Ẃ o?er @F
Greek symbols
α ¿ asect ratio o' rectangular ducts, ratio o' a small to large side length β sur'ace area densit& m2 m/4Fδ distance et?een tues mF∆ p ressure dro +aFε heat e>changer e''ecti%enessη e''icienc& μ d&namic %iscosit& J s m/2F ρ densit& g m/4F
Subscripts
o initial
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1,2,3,4 anine c&cle rocessamb amientc thermod&namic c&clecond condensationcrit critical
e e''ecti%eevap e%aoratingexp e>ansionext e>ternalf ?oring 'luidg e>haust gasesh h&draulici internalin inletm materialout outletp umpp inch/ointpump umings isentroict turinew ?all
Superscripts
m %iscosit& ratio e>onent
Abbreviations
BME+ rea mean e''ecti%e ressure
EK e>haust gas recirculation
E"C electrical turo/comounding
HC
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%& 'ntroduction
!nternal comustion engines (!CEs) are the maLor source o' moti%e o?er in the
?orld, and this is e>ected to continue 'or some decades0 Kreenhouse e''ects and
deleted etroleum sulies are crucial issues that the de%eloed ?orlds economies are
'acing0 Because o' this, go%ernments in industrialiNed countries ha%e introduced strict
regulations 'or !CE emissions and 'uel econom& standards0 !n the last t?o decades,
manu'acturers ha%e imro%ed signi'icantl& !CE e''iciencies & al&ing a numer o'
ne? technologies 1F0 !n recognition o' the need to 'urther reduce %ehicle e>haust
ollutant emissions (C=, J=>, h&drocarons and articulate matter) and, more recentl&,
also C=2 emissions, there has een a lot o' interest in the de%eloment o' cleaner and
more e''icient %ehicle o?ertrains 2F0
!n !CEs onl& aout 1G4 o' the 'uel comustion energ& is con%erted into use'ul
?or to dri%e the %ehicle and its accessor& loads0 "he remainder is engine ?aste heat
dissiated & the engine e>haust s&stem, coolant s&stem, and con%ection as ?ell as
radiation 'rom the engine loc 4F0 Jearl& - o' the heat energ& is ?asted ?ith the
engine e>haust gases -F0 !' the ?aste heat o' an !CE can e reco%ered, the engine
e''icienc& ?ill e imro%ed 4F0
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ased on the steam generation in a secondar& circuit, ?hich reresents an indirect
method o' @H0 "his techniue has ad%antages comared ?ith the so/called direct
@H techniues (e.g., E"C, M"C and "!KES) that use a o?er turine 'itted to the
%ehicle e>haust, ?hich has a much higher imact on the engine uming losses0 !n
addition, a C allo?s 'or high ?aste energ& utiliNation and it is cheaer than other
@H techniues such as thermo/electric generators 7F0
"he choice o' the ?oring 'luid to e used in the C deends on a numer o'
'actors, namel&, thermod&namic, en%ironmental, sa'et&, rocess/related and economic
issues0 !n articular, ?hen imlementing such a s&stem on a mo%ing %ehicle ?ith li%e
occuants, the choice must consider ?orse case scenarios lie leaages or crashes0 =n
that e%ent the 'luid must e harmless to the %ehicle occuants0
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conditions o' an =C comaring h&drochloro'luorocaron (HCtra 'uel, oth the
seci'ic 'uel consumtion and the ollutant emissions o' the %ehicle are reduced
8, .F0 "he er'ormance anal&sis o' %arious s&stem con'igurations ased on Cs is
romising0 According ?ith Boretti 3F imro%ements in 'uel econom& u to 19 ma&
e ossile, ?hich can ser%e as a re'erence asis 'or the assessment o' the current
otential o' this technolog&, ?hose maLor do?n'alls are the increase o' ?eight, the
acaging comle>it&, the transient oeration and the costs0 =' course, the
imlementation o' a C on a %ehicle reuires detailed in%estigations o' all these issues0
"o reco%er the e>haust ?aste heat, the C needs to utiliNe a heat e>changer to
e>tract energ& 'rom the e>haust gases0 A heat e>changer used in such an alication has
to e ale to ro%ide an adeuate sur'ace area in order to achie%e high e>change
e''icienc&, ?hile using a small/siNe and light?eight arrangement0 cessi%e uming losses that ?ill ha%e a
negati%e imact on the !CE e''icienc& 13F0 Ma%idrou et al0 13F e>amined the e>haust
gas heat e>changer design rolem, 'ocusing on the usage o' di''erent heat e>changer
con'igurations and di''erent t&es o' heat trans'er sur'aces0
"his article resents an anal&sis o' a comined C (o?er c&cle) and heat
e>changer 'or %ehicle @H alications, ?hich, to the est o' our no?ledge, is
currentl& lacing in the literature0
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e%aluates e>erimentall& the e>haust thermal energ& contained in a %ehicle euied
?ith a sar ignition !CE0 Suseuentl&, the data otained are used as inut in t?o
de%eloed models5 a C thermod&namic model, ?hich includes oth energ& and e>erg&
anal&ses, and a heat e>changer model0 Among other 'eatures, the C thermod&namic
model allo?s assessing the C e''icienc& and the net o?er as 'unction o' the
e%aorating ressure o' the three ?oring 'luids0 "he heat trans'er model ermits to
er'orm heat e>changer siNing calculations and to assess the di''erent heat e>changer
e''iciencies and ressure dro0 changer models ?ere used together to e%aluate the %ehicle e>haust @H otential
using di''erent Cs0
"he e%aorator and the e>ander are the most critical comonents o' a C s&stem0
"he resent stud& considers a%ailale comonents (e%aorator and e>ander) that allo?
uilding a short term C rotot&e 'or @H in %ehicle alications0 Based on the
measured %alues in the chassis d&namometer e>eriments and on the simulation results,
the otential o?er outut o' the roosed C rotot&e is assessed and comared 'or
di''erent %ehicle oerating conditions0
(& Experi$ental approach
"his section descries the e>erimental aroach 'ollo?ed to gather the data used
as inut in the C thermod&namic and heat e>changer models0 !t also uanti'ies the
e>haust ?aste heat as a 'unction o' the %ehicle oerating conditions0
Chassis d&namometer measurements ?ere carried out on a %ehicle euied ?ith
a 208 liter 3 sar ignition engine in order to measure the e>haust gases mass 'lo?
rate and temerature 'or se%eral stead& state oerating conditions (i0e0, a'ter engine
?arm/u)0
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%arious loads0 "ale 1 resents the %ehicle test conditions considered in this ?or0 !n the
tale, N is the imosed engine seed, F is the imosed load, BME+ is the rea mean
e''ecti%e ressure, V is the %ehicle seed, P e is the %ehicle e''ecti%e o?er (or rae
o?er) measured at the chassis d&namometer, ḿg is the %ehicle e>haust mass 'lo?
rate, T g,in is the e>haust gases temerature measured do?nstream o' the three ?a&
catal&st ("@C), and Q́available is the heat a%ailale in the e>haust gases0 "he test
conditions originated e>haust gases mass 'lo? rates and temeratures ranging 'rom 1208
gGs to 7.09 gGs and 940. I to 17204 I0
All measurements ?ere otained a'ter oth the engine and the "@C reached their
stead& states0 "o %alidate the stead& states the coolant temerature ?as controlled to .7
PC Q 1 PC0 !n addition, controlled temeratures had to remain stale ?ithin Q 7 PC 'or,
at least, 1 minute0 !n the resent stud&, the recorded measurements ?ere al?a&s the
a%erage o' the readings o%er a eriod o' time o', at least, 2 minutes0
!n order to e%aluate the reeatailit& o' the torue and engine seed
measurements, si> tests ?ere er'ormed 'or each stead& state oerating condition0 !n the
torue measurements, the comined uncertaint& ranged 'rom Q 201 to Q 20.9 and
no relationshi et?een the uncertaint& and the torue magnitude ?as identi'ied0 !n the
engine seed measurements, it ?as 'ound that the comined uncertaint& decreases
monotonicall& as the engine seed increases0 Conseuentl&, the ma>imum uncertaint&
occurred at idle (Q 202-) and the minimum uncertaint& at - rm (Q 10-1)0 "he
BME+ deends on the torue measurement0 As a result, gi%ing that the dislacement
%olume is no?n, the e>erimental uncertainties associated ?ith the BME+ calculations
are those o' the torue measurements0
!n the resent stud& the e>haust gases mass 'lo? rate ?as calculated ased on the
inlet air mass 'lo? rate and stoichiometric air 'uel ratio0 "he inlet air mass 'lo? rate ?as
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measured using the engine air mass 'lo? rate sensor0 eeatailit& tests &ielded
ma>imum uncertainties o' Q 4020 "he uncertainties associated ?ith the temerature o'
the e>haust gases ?ere e%aluated to e ?ithin Q 1 I o' the mean %alue0
"he e>haust gases roerties ha%e een calculated using the euations sho?n in
"ale 2, ?hich ?ere deri%ed using the so't?are e'ro .0 19F0 "he comosition
(mass 'ractions) o' the e>haust gases ?as assumed to e 20- C= 2, 908 H2= and
9108 J2 (minor comonents ha%e een neglected)0
!n the resent stud&, the heat a%ailale in the e>haust gases ?as calculated through
the 'ollo?ing euation5
g ,∈¿−T ambT ¿
Q́available= ḿ g∙ c pg¿
(1
)
?here ḿg is the e>haust gases mass 'lo? rate,g ,∈¿
T ¿ is the e>haust gases
temerature e'ore the C heat e>changer (i0e0, the e>haust gases temerature a'ter the
"@C) and T amb is the amient temerature, taen eual to 27 PC in the resent stud&0
"ale 1 includes the %alues o' Q́available 'or all the oerating conditions0 !t is seen that
the a%ailale e>haust ?aste heat changes signi'icantl& 'rom lo? loads and seeds to
high loads and seeds0
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ideal thermod&namic c&cle includes the 'ollo?ing rocesses5 an isentroic comression
rocess in a um (1/2), an isoaric heat trans'er rocess in a heat e>changer (2/4), an
isentroic e>ansion rocess through a turine (or other e>ansion machine) (4/-), and
an isoaric heat trans'er rocess in a condenser (-/1)0
"he um sulies the ?oring 'luid to the heat e>changer, ?here the ?oring
'luid is heated and %aoriNed, remo%ing heat 'rom the e>haust gases0 "he ?oring 'luid
lea%es the heat e>changer in saturated or suerheated state0 "he high enthal& %aor is
then e>anded in the e>ander (usuall& a turine), ?hich is couled to a generator that
deli%eries the C o?er outut0 A'ter the e>ander, the ?oring 'luid enters the
condenser ?here it condensates0
"he mathematical model o' the simle C uses the thermod&namic energ&
conser%ations euations 18F0 "he model considers a stead& state oeration ?ith
negligile inetic and otential energ& e''ects0 "aen these considerations into account,
the um o?er is gi%en &5
Ẃ p= ḿf (h2−h1 )(2
)
"he heat asored 'rom the e>haust gases & the ?oring 'luid in the heat e>changer is
gi%en &5
Q́¿=ḿf (h3−h2 ) (4)
"he turine o?er is calculated &5
Ẃ t = ḿf (h3−h4 ) (-
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)
and the heat reLected 'rom the condenser is gi%en &5
Q́out = ḿf ( h4−h1 ) (7)
"he C e''icienc& can e de'ined as the net o?er roduced re'erred to the heat
recei%ed at the heat e>changer as 'ollo?s5
ηc=Ẃ t − Ẃ p
Q́¿(3)
E>erg& is a use'ul concet 'or e%aluating the er'ormance o' %arious energ&
s&stems0 E>erg& is the ma>imum amount o' ?or that can e done & a rocess as it
aroaches the thermod&namic euilirium ?ith its surroundings & a seuence o'
re%ersile rocesses 7, 18, 1.F0 "he e>erg& o' a sus&stem is a measure o' its Rdistance
'rom euilirium and, thus, it can classi'& the energ& ualit& o' the sus&stem0 E>erg&
destruction rate laels the loss o' e>erg& during the rocess 7F0 "he e>erg& destruction
is due to irre%ersiilities occurring inside the s&stem or the comonents o' the s&stem, a
control mass 'or the s&stem or, as in this ?or, a control %olume 'or each comonent
and it can e caused & internal or e>ternal 'actors 2F0 As in the re%ious studies e.g.,
2/22F, in this ?or, the contriutions o' the internal and e>ternal irre%ersiilities are
not recogniNed searatel&, eing calculated as a ?hole0
"he e>erg& destruction rate 'or each rocess in the c&cle (e%aoration, e>ansion,
condensation and uming) can e e>ressed as 'ollo?s5
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T g, ∈¿T g,out
¿ḿf (s3−s2)+ ḿg c pgln ( ¿ ]
´ I evap=T amb¿
(9a)
́I exp=T amb ḿf (s4−s3 ) (9)
́I co!+!ischa"ge!=T amb ḿf (s1−s4−h1−h4T amb ) (9c)
́I pump
=T amb
ḿf (
s2−s1)
(9d)
Jote that at the condenser the e>erg& destruction rate e>resses the sum o' the
irre%ersiilit& o' the condenser and the e>erg& discharged ?ith the cooling air that 'lo?s
across the condenser0
Aart 'rom the simle C, there are other C con'igurations that ermit to
increase the reco%ered thermal energ&0 amle, the thermal e''icienc& o' a C can
e augmented & adding a reheater or a regenerator 9F0 Mago et al0 21F resented an
anal&sis o' regenerati%e =Cs using dr& 'luids, ?here the& demonstrated that
regenerati%e =Cs not onl& ha%e higher 'irst and second la? e''iciencies than asic
=Cs, ut the& also ha%e lo?er irre%ersiilities and lo?er heat reuirements to roduce
the same o?er0 ecentl&, @ang et al0 22F studied the characteristics o' a dual loo
=C s&stem ?hich reco%ers the ?aste heat 'rom the e>haust and the coolant o' a sar
ignition !CE0 "he high temerature (H") loo reco%ers the e>haust ?aste heat using
2-7'a as the ?oring 'luid and the lo? temerature (") loo reco%ers the coolant
?aste heat and the residual heat 'rom the H" loo using 14-a as the ?oring 'luid0
"he results re%ealed that ?ith this con'iguration the net o?er o' the " loo is higher
than that o' the H" loo0
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Ho?e%er, Cs ?ith regeneration, reheating rocesses or dual loo s&stems
reuires more iing (increased ressure losses) and more comle> de%ices 9F0
icit& and non/'lammailit& are
a 'e? re'erale h&sical and chemical characteristics 18F0 Se%eral organic 'luids 'or
use in Cs ha%e een roosed in the literature 11/17, 2/22, 2-/29F0 Among them, the
organic 'luids 124 and 2-7'a aear to e the most romising ones 'or the oerating
conditions used in this ?or, mainl& due to its non/'lammale eha%ior and
thermod&namic er'ormance0 "here'ore, the organic 'luids 124 and 2-7'a ha%e een
1-
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selected 'or the resent stud&0 !n addition, ?ater has een also considered as ?oring
'luid in this ?or ecause it is non/to>ic and due to its aundant a%ailailit&0 "ale 4
resents the main thermoh&sical roerties o' the ?oring 'luids studied in this ?or
(124, 2-7'a and ?ater)0
haust gases0 Considering the oerational conditions o' a simle C assemled on the
!CE e>haust s&stem o' a %ehicle, the resent model constraints are as 'ollo?s5
(i) e%aorating ressure %ar&ing et?een condensation ressure, pco! , and
critical ressure, pc"it :
(ii) dr& e>ansion 'or all 'luids:
(iii) isentroic e>ander e''icienc&, ηt =0.7 9F:
(i%) isentroic um e''icienc&, η p=0.8 9F:(%) negligile ressure losses in the heat e>changers and ies:
(%i) 'or oth organic 'luids (124 and 2-7'a) the condensation temerature is
T cond 424 I, ?hich corresonds to the condensation ressures gi%en in "ale
4: 'or ?ater, the condensation temerature is T cond 494 I, ?hich corresonds
to a condensation ressure o' 1 ar 28F:
(%ii) the suerheating temerature is set as the minimum to guarantee a dr&
e>ansion0
A sensiti%it& assessment ?as er'ormed 'or the %alues o' the e>ander and um
isentroic e''iciencies, ?ater e%aorating and condensation ressures and organic 'luids
e%aorating and condensation temeratures0 "ale - summariNes the results otained0 !t
is seen that the e>ander e''icienc& a''ects signi'icantl& the C net o?er outut0
Moreo%er, it is interesting to note that the C net o?er outut is more sensiti%e to the
condensation conditions o' the ?oring 'luids than to the e%aorating conditions0
changer
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characteristics0 !n the resent stud&, ?e used a T g,out 2 PC in all C
thermod&namics calculations er'ormed0 !t is seen that onl& in the case o' ?ater the
temerature di''erence et?een the e>haust gases and the ?oring 'luid at the eginning
o' the e%aoration rocess (the so/called inch/oint temerature di''erence ++"D)
ma& e rolematic0
changer0 "he ++"D is the smallest temerature di''erence in
the C heat e>changer, estalishing the ma>imum allo?ale e%aoration ressure and,
thus, limiting the C e''icienc&0 !t is necessar& to guarantee a minimum ++"D o' 4 PC
8F, ?hich is articularl& challenging at lo? loads and lo? engine seeds0
!n the resent stud&, a C thermod&namic model, ?hich includes oth energ& and
e>erg& anal&ses, ?as de%eloed to e%aluate the %ehicle e>haust @H otential using a
C0 "he reuired thermod&namic and transort roerties 'or the ?ater and the organic
?oring 'luids ?ere calculated ?ith the aid o' the e'ro .0 19F0 haust gases at the heat e>changer outlet0
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*& Heat exchanger $odel
"he heat e>changer (e%aorator) is an essential comonent in %ehicle @H
alications0 "he 'ollo?ing characteristics are desirale in an heat e>changer 'or such
alications5
i) high heat e>changer e''ecti%eness:
ii) lo? ressure dro trough the heat e>changer, ?hich minimiNes the negati%e
imact o' the e>haust ac ressure on the !CE:
iii) comactness0
!mro%ements in the heat e>changer e''ecti%eness can e otained & increasing
the heat trans'er area or the heat trans'er coe''icient 'rom the e>haust gases side0 !n a
tuular heat e>changer, the heat trans'er area is usuall& increased & increasing the
numer o' tues andGor & using 'ins inside the tues0 !t is ?ell no?n that the e>haust
gases heat trans'er coe''icient is much smaller than the C ?oring 'luid heat trans'er
coe''icient0 As a result, 'inned sur'aces are usuall& laced on the e>haust gases side to
increase the heat trans'er area 13F0
A literature sur%e& e0g0, 13, 2.F re%ealed that shell and tue heat e>changers are
the most aroriate to e used as e%aorator in Cs 'or %ehicle e>haust alications0
"he heat e>changer model de%eloed in the resent stud& allo?s accessing the thermal
and h&draulic characteristics o' %arious duct geometries (suare, rectangular and
circular) as 'unction o' the numer o' tues o' the heat e>changer0
"he resent heat e>changer model is ased on the e''ecti%eness/J"$ (ε/J"$)
method0 "he o%erall heat trans'er coe''icient U is calculated according to the 'ollo?ing
euation 4F5
# = 1
!e$t
! i hg+
!e$t %! , i
! i +
! e$t
2& m ln(!e$t
!i )+ %! ,e$t +
1
hf
(8
)
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!n the resent stud& the tue ?as assumed to e made o' Aluminum, ?ith
& m=225W m−1
' −1
4F0 haust gases 41F0 "he o%erall heat trans'er
coe''icientU is little a''ected & the 'ouling resistances 13F0 "he 'ouling resistance on
the gas side is higher than that on the 'luid side0 "he articulate matter resent in the
e>haust gases are the rincial resonsile 'or the 'ouling resistance on the gas side0
Jote that the resent stud& e>amines an e%aorator laced a'ter a "@C (see
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2100 , the Jusselt numer is e%aluated ?ith the aid o' the Knielinsi
correlation 4F5
(u!=( f /8 ) (ℜ!−1000 ) ( *" )
1+12.7 (f /8 )1/2 ( *"2/3−1 ) [1+( )h + )
2
3 ] ( μ/ μ )m , ℜ!>2100 (11)
!n es0 (1) and (11), μ is the 'luid %iscosit& at the ul 'luid temerature, μ? is the 'luid
%iscosit& at the heat trans'er oundar& sur'ace temerature, m 01- 'or
e U 8 and m 027 'or e V 80 !n e0 (11), f is a logarithmic 'unction o' the
e&nolds numer5
f =(0.79 ∙ ln ( ℜ! )−1.64)−2
(12
)
"he heat e>changer e''ecti%eness, ε, is calculated 'rom5
ε =1−e− (T# =1−e−hg -ḿg c pg (14)
considering onl& the e>haust gases 'lo?0 Jote that this relation is %alid onl& 'or
condensers and e%aorators0
"he sur'ace area densit&, β , 'or suare, rectangular and circular cross 'lo?
geometries is calculated through the 'ollo?ing euations 42F5
β= 4b
( b+δ )2(1-a)
β= 2 (α ¿
+1 ) b(b α ¿ +δ ) (b+δ )(1-)
1.
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β= 2.b
√ 3 (b+δ )2 (1-c)
"he ressure dro through shell and tue heat e>changers consisting o' suare,
rectangular and circular cross 'lo? geometries is calculated as 'ollo?s 42F5
/ p=4 f+ ( ḿ / -0 )
2
2 ρg )h ( t (17)
"he heat e>changer considered in the resent stud& is a shell and tue counter
'lo? t&e, ?ith the hot 'luid (e>haust gases) in tues and the cold 'luid (C ?oring
'luid) in the shell0 !n order to stud& the e''ect o' the imortant thermal and h&draulic
characteristics o' the heat e>changer as a 'unction o' the numer o' the tues 'or
di''erent cross 'lo? geometries, 'irst ?e had to de'ine the main dimensions o' the heat
e>changer0 Hussain and Brigham 2.F demonstrated that the heat e>changer
e''ecti%eness decreases 'or larger shell diameters, ?hich deend on the cross 'lo? area
o' the heat e>changer0 =n the other hand, it is ?ell no?n that the e>haust gases
ressure dro decreases 'or larger cross 'lo? areas o' the heat e>changer tues0
Considering this trade/o'' and the limited sace a%ailale 'or the installation o' the heat
e>changer, the cross 'lo? area o' the heat e>changer tues in the resent stud& ?as set
eual to the %ehicle e>haust duct cross 'lo? area0 "he %ehicle e>haust duct under stud&
has a cross 'lo? area eual to -0=2.561010−3
m2
0 "o calculate the cross 'lo? area
o' each tue, -0 ?as di%ided & the numer o' tues in the e%aorator0 !n regard to
the heat e>changer length, it ?as assumed tue lengths o' 07 m o?ing to the
dimensions o' %ehicle under stud&0 !n this case ?e ha%e also er'ormed a sensiti%it&
anal&sis & considering %ariations in the heat e>changer length o' Q01 m0 "he
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calculations indicated %ariations in the C net o?er outut o' Q17, re%ealing the
signi'icant imact o' this arameter in the resent stud&0
changer is to e installed in the
e>haust duct o' the %ehicle0 !n such an alication, the minimiNation o' the e>haust
gases ac ressure on the !CE is o' critical imortance0 "he heat e>changer ?ith
circular tues ro%ides the lo?est e>haust gases ac ressure (see changer costs0 As a result, in site o' the heat e>changer e''ecti%eness
enalt&, the con'iguration ?ith circular tues ?as selected 'or this stud&0
As alread& ointed out,
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the heat e>changer e''ecti%eness 'or a large numer o' tues (- to 1) is
comarati%el& small0 "hese results estalish the ma>imum 'or the numer o' tues in
the heat e>changer5 -4 tues in the resent stud&0 Considering the cross 'lo? area and
the he>agonal shell and tue heat e>changer arrangement, -4 tues corresonds to a
tue diameter o' 1 mm, ?ith a distance et?een the tues o' - mm, and a shell inside
radius o' .- mm0
"he heat e>changer ?as di%ided into three Nones 'or modeling uroses, as sho?n
in changer0
+& Results and discussion
22
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+&%& RC ther$odyna$ic analysis
"his section resents a comined 'irst and second la? anal&sis0 "he main
oLecti%e o' this section is to assess the C e''icienc&, η , the turine outletGinlet
e>ansion ratio, v-Gv4, the ?oring 'luid mass 'lo? rate, ḿf , and C net o?er,
Ẃ et , as 'unction o' the e%aorating ressure 'or the ?oring 'luids studied0 "o this
end, an adiaatic heat e>changer ?as considered so that the ma>imum %ehicle e>haust
@H otential, assuming a T g,out 2 PC (see section 4) ?as assessed0 "he
thermod&namic anal&sis reorted elo? has een er'ormed 'or the e>haust conditions
corresonding to the %ehicle oerating conditions 4, . and 14 (see "ale 1), ?hich
reresent lo?, intermediate and high engine seed and load stead& state %ehicle
oerating conditions, resecti%el&0 "his allo?s the assessment o' the er'ormance o' the
C 'or di''erent e>haust mass 'lo? rates and temeratures0
ansion ratio (v-Gv4), regardless o' the e%aorating
ressure0 "his is mainl& due to the higher 2-7'a condenser ressure (-012 ar) as
comared to that o' the ?ater (1 ar)0 "he turine outletGinlet e>ansion ratio (v-Gv4) is
an imortant arameter as it indicates ho? much the 'luid %olume increases through the
e>ansion rocess0 !t should e noted that the e>ansion ratio (v-Gv4) can change
signi'icantl& according ?ith the characteristics o' the ?oring 'luid0 "he e>ansion ratio
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is also %er& imortant 'or the e>ander selection0 @hen the e>ansion ratio (v-Gv4) is
smaller than 7, e>ansion e''iciencies higher than 08 can e achie%ed using a single
stage a>ial turine as e>ander 9F0
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chosen a condensation temerature o' 424 I 'or the organic 'luids (124 and 2-7'a)
and 494 I 'or ?ater0 Desite the higher ?ater condensation temerature, haust @H alications
that needs to e care'ull& considered in 'uture =C studies0
"he higher temerature di''erence et?een the e>haust gases and the ?oring
'luid in the heat e>changer 'or 124 and 2-7'a (see erg&
destruction rate decreases0 !ncreasing the e%aorating ressure is a good method to
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a%oid second la? losses0 High e%aorating ressures also increase the C 'irst la?
e''icienc&, as sho?n in ture ?oring 'luids is still %er& limited and more ?or is necessar& to otain a etter
understanding o' their in'luence on the er'ormance o' Cs0
"he resent results (not sho?n here) re%ealed also that the entro& generation rate
in the condenser is signi'icantl& lo?er than that in the e%aorator mainl& ecause o' the
smaller temerature di''erences that occur in the condenser0 "he entro& generation rate
in the e>ander and um are related to the isentroic e''icienc& o' these de%ices0 =ur
results indicated that the e>ander entro& generation rate is much higher than that in
the um, ut consideral& lo?er than those in the e%aorator and condenser0
Consistentl& ?ith re%ious studies e0g0, 2F, the resent anal&sis demonstrates that the
e%aorator maes the iggest contriution to the o%erall entro& generation rate in the
C s&stem0
"o comlement the resent second la? anal&sis, the e%aorator e>erg& e''icienc&
?as also determined0 "o this end, the dead state ?as seci'ied as T amb=2512 and
pamb=1atm 0
"he e>erg& 'lo? rate o' the e>haust gases (assumed to e an ideal gas) entering
and lea%ing the C can e calculated as5
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´ E 3= ḿg[c pg (T g, 3−T amb)−(c pg ln( T g , 3T amb )− % g ln( p 3 pamb ))] (13)
"he e>erg& 'lo? rate o' the ?oring 'luid at an& oint o' the C can e
determined as5
´ Ei= ḿf [ (hi−hamb )−T amb ( si−samb ) ] (19)
"he e%aorator e>erg& e''icienc& can e e>ressed as5
´ Eg ,∈¿− ´ Eg,out
ηe$e"g4 ,evap=´ Euseful
´ Eavailable=
´ E3− ´ E
2
¿(18)
?here ´ Euseful and ´ Eavailable are the actual e>erg& used and the theoreticall&
a%ailale e>erg& at the e%aorator, ´ E2 and ´ E3 are the e>erg& 'lo? rates o' the
?oring 'luid entering and lea%ing the e%aorator, resecti%el&, andg ,∈¿´ E ¿
and
´ Eg,out are the e>erg& 'lo? rates o' the e>haust gases entering and lea%ing the
e%aorator, resecti%el&0
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comared to the organic 'luids0 "he results 'rom the comined 'irst and second la?
anal&sis sho? that ?ater &ields higher thermod&namic e''icienc& as comared to the
organic 'luids0
"he thermod&namic anal&sis demonstrates that the ?ater is an adeuate ?oring
'luid 'or use in an e>haust heat reco%er& s&stem ?ith a C 'or the 'ollo?ing reasons5 as
comared to the organic 'luids, ?ater (i) &ields higher thermod&namic e''icienc& and
net o?er outut: (ii) reuires lo?er uantities o' ?oring 'luid in the C (less ?eight):
(iii) condenses easil& at atmosheric ressure: (i%) has lo?er rice and higher
aundance: and (%) resents no en%ironmental riss0 !t should e stressed, ho?e%er, that
the use o' ?ater as the ?oring 'luid in cold regions ma& e rolematic0 !n case o'
'rost, ?ater e>ands at 'reeNing and this can destro& the euiment in a single cold
night0
+&(& Heat exchanger analysis
"his section e>tends the C thermod&namic anal&sis resented in the re%ious
section, & considering also the heat e>changer model0 !t e>amines t?o shell and tue
counter 'lo? t&e heat e>changers ?ith the e>haust gases assing through the tues,
re'erred herea'ter as e%aorator 1 and e%aorator 20 E%aorator 1 maintains the cross
'lo? area o' the %ehicle e>haust duct under stud& ?ith tue diameters o' 1 cm0 Seci'ic
heat e>changers 'or @H alications are currentl& not a%ailale, so a shell and tue
counter 'lo? t&e e>haust gas recirculation (EK) cooler 'rom a MAJ diesel truc ?as
selected as e%aorator 20 A similar aroach ?as considered in re%ious studies e0g0,
29F0 "ale 7 summariNes the main characteristics o' e%aorators 1 and 20 "he main
oLecti%e o' this section is to assess the in'luence o' the heat e>changer on the C net
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o?er outut, Ẃ et , as a 'unction o' the e%aorating ressure 'or the ?oring 'luids
studied0
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!t should e noted that ?hen e%aorator 1 is considered in the simulations, the
temerature o' the e>haust gases decreases onl& & aout 2 PC0 !n this case the %alue
o' T g,out ?as ?ell ao%e that (2 PC) considered in the C thermod&namic anal&sis
in the re%ious section0
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e>isting e>haust duct in the %ehicle), ?hich increases the 'lo? %elocit& o' the e>haust
gases0
!n regard to the heat trans'er characteristics o' the ?oring 'luids, "ale 3
demonstrates that the o%erall heat trans'er coe''icient is higher 'or ?ater 'ollo?ed & the
organic 'luids 2-7'a and 1240 Jote that "ale 3 e>amines the oerating condition 14,
?hich corresonds to a high %ehicle load and high engine seed (see "ale 1)0 "his
means that the oor ?ater e%aorator e''ecti%eness oser%ed 'or the oerating condition
4 (see haust @H otential0
"he results 'rom the C thermod&namic and heat e>changer models ?ere used to
calculate imro%ements in e''iciencies0 "he !CE thermal e''icienc& ?as calculated
through the 'ollo?ing euation5
ηth=Ẃ et
ḿfuel ∙ +56 =
Ẃ et
ḿai"
-
7
∙ +56 (1.)
?here H ?as taen eual to -- MGg 44F0
"he %ehicle mechanical e''icienc& ?as de'ined as the ratio o' the use'ul ?or
roduced & the C, Ẃ et , and the e''ecti%e o?er roduced & the !CE, P e5
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ηm=Ẃ et
*e(2)
"he calculations ?ere er'ormed 'or three oerating conditions: seci'icall&,
oerating conditions 4, . and 14 in "ale 10 !n addition, three distinct Cs ?ere
e%aluated5
i) C1 that considers an adiaatic heat e>changer and an e%aorating ressure
o' 2 M+a:
ii) C2 that considers e%aorator 1 (see "ale 7) and an e%aorating ressure o'
2 M+a:
iii) C4 that considers e%aorator 2 (see "ale 7) and an e%aorating ressure o'
072 M+a0 !n this case a commercial a%ailale e>ander (Kreen "urine "M)
that ?ors onl& ?ith ?ater as a ?oring 'luid is considered0
Jote that the C4 case e%aluates the er'ormance o' a C rotot&e s&stem that
uses e>isting comonents5 e%aorator 2 and the Kreen "urine"M
, ?hich is currentl&, to
the est o' our no?ledge, the most aroriate e>ander 'or a C %ehicle alication0
"he main characteristics o' the Kreen "urine"M are inlet steam ma>imum ressure o'
702 ar, inlet steam ma>imum temerature o' 2 PC, o?er o' 207 @, ?eight o' 9 g,
length o' 27 cm and diameter o' 1. cm 4-F0 "he reduced mass and dimensions maes
this turine suitale 'or %ehicle e>haust @H alications0
"he control o' the C in a %ehicle alication is articularl& comle> due to the
(o'ten) transient regime o' the heat source0 As a result, otimiNing the C control is
crucial to ma>imiNe the er'ormance o' the s&stem0
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"ale 9 resents the increase in the !CE thermal and %ehicle mechanical
e''iciencies 'or the three Cs studied0 @ater is the ?oring 'luid ?ith the greatest
otential to e used in @H 'rom e>haust gases in %ehicles through C1 as comared
to the organic ?oring 'luids 124 and 2-7'a0 Seci'icall&, at an e%aorating ressure
o' 2 M+a, 'or oerating condition ., the increase in the %ehicle mechanical e''icienc&
using the C1 is 170.7, 140-4 and 103- 'or ?ater, 124 and 2-7'a,
resecti%el&0
!n the case o' C2, "ale 9 sho?s that the organic 'luid 124 is more suitale to
e used in @H 'rom e>haust gases in %ehicles through Cs, eseciall& at lo?er
e>haust gases temeratures0 Ho?e%er, 'or higher temeratures and higher e>haust gas
'lo?s, C2 resents higher thermal and mechanical e''iciencies i' ?ater is used as the
?oring 'luid0
"ale 9 re%eals that the C4 resents thermal and mechanical e''iciencies o'
04/087 and 2019/4089, resecti%el&0 As comared ?ith the C1 (see "ale 9)
these %alues are rather modest0 Ho?e%er, note that the C4 accounts 'or the ractical
constrains introduced & the e>isting C comonents0
"he C4 allo?s assessing the thermal and mechanical e''iciencies o' a short term
C rotot&e0 "he results 'ound demonstrate that 'uture C rotot&es reuire
imro%ed e%aorator designs and e>ander de%ices allo?ing 'or higher e%aorating
ressures0
"he oeration o' the e%aorator at higher ressure allo?s increasing the C 'irst
and second la? e''iciencies and ermits reducing the temerature di''erences across the
heat e>changer sur'aces, ?hich minimiNe the 'ilm oiling e''ect in ?hich rates o' heat
trans'er 'all sharl& 47F0
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"he oen literature e.g., 9/., 17F generall& anal&sis the ma>imum @H otential
o' a C 'itted to the %ehicle e>haust0 !n the resent stud& the ma>imum @H otential
?as e%aluated through the C10 "he !CE thermal e''iciencies otained in this stud& 'or
the C1 are in agreement ?ith those resented & Oamada and Mohamad .F, ?ho
reorted increases in thermal e''iciencies o' 20./409, as comared ?ith 10-/4072
in this stud& (see "ale 9)0 !n regard to the increase in %ehicle mechanical e''icienc&
('uel econom&), aLa and Kamarotta 9F reorted %alues around 12, as comared
?ith 1013/170.7 in this stud& (see "ale 9)0 Srini%asan et al0 8F e>amined the
e>haust ?aste heat reco%er& otential o' a high e''icienc&, lo? emissions, dual/'uel, lo?
temerature comustion engine using an =C0 "heir results sho?ed that %ehicle
mechanical e''icienc& imro%ed & an a%erage o' 9 'or all inLection timings and loads
?ith hot EK0 changer model0 Both models used as
inut, e>erimental data otained in a %ehicle tested on a chassis d&namometer0 "he
thermod&namic anal&sis ?as er'ormed 'or ?ater, 124 and 2-7'a and re%ealed the
ad%antage o' using ?ater as the ?oring 'luid in alications o' thermal reco%er& 'rom
e>haust gases o' %ehicles euied ?ith a sar/ignition engine0 Moreo%er, the heat
e>changer e''ecti%eness 'or the organic ?oring 'luids 124 and 2-7'a is higher than
that 'or the ?ater and, conseuentl&, the& can also e considered aroriate 'or use in
4-
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%ehicle @H alications through Cs ?hen the e>haust gas temeratures are
relati%el& lo?0
changer the simulations re%ealed increases in !CE thermal
e''icienc& and %ehicle mechanical e''icienc& o' 10-/4072 and 1013/170.7,
resecti%el&, ?hile 'or a shell and tue heat e>changer, the simulations sho?ed an
increase o' 087/102 in the thermal e''icienc& and an increase o' 203-/30.3 in the
mechanical e''icienc& 'or an e%aorating ressure o' 2 M+a0 Ho?e%er, it is imortant to
note that the thermal and mechanical e''iciencies can e enhanced ?ith the increase in
the e%aorating ressure o' the ?oring 'luid0
"he resent anal&sis con'irms that Cs ha%e high otential 'or %ehicle e>haust
?aste heat reco%er&0 Ho?e%er, imro%ed e%aorator designs and aroriate e>ander
de%ices allo?ing 'or higher e%aorating ressures are reuired to otain the ma>imum
@H otential 'rom %ehicle C s&stems0 Considering increasing 'uel rices and
en%ironmental issues, this technolog& ?ill ermit to achie%e 'urther reductions in engine
seci'ic 'uel consumtion and C=2 seci'ic emissions0
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-& References
1F Iatsanos C=, Hountalas D", +ariotis EK0 "hermod&namics anal&sis o' a anine
c&cle alied on a diesel truc engine using steam and organic medium0 Energ&
Con%ersion and Management 212:3:38/930
2F @ang ", Xhang O, +eng X, Shu K0 A re%ie? o' researches on thermal e>haust heat
reco%er& ?ith anine c&cle0 ene?ale and Sustainale Energ& e%ie?s
211:1752832/910
4F He M, Xhang Y, Xeng I, Kao I0 A comined thermod&namic c&cle used 'or ?aste
heat reco%er& o' internal comustion engine0 Energ& 211:4353821/.0
-F Ou C, Chau I"0 "hermoelectric automoti%e ?aste heat energ& reco%er& using
ma>imum o?er oint tracing0 Energ& Con%ersion and Management
2.:75173/120
7F @ang EH, Xhang HK, haust and coolant heat
reco%er& through organic anine c&cles0 !nternational ournal o' H&drogen
Energ& 211:435127.1/30
9F aLa !, Kamarotta A0 !nternal comustion engine (!CE) ottoming ?ith organic
anine c&cles (=Cs)0 Energ& 21:47518-/.40
8F Srini%asan II, Mago +, Irishnan S0 Anal&sis o' e>haust ?aste heat reco%er&
'rom a dual 'uel lo? temerature comustion engine using an organic anine
c&cle0 Energ& 21:4752489/..0
43
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.F Oamada J, Mohamad MJA0 E''icienc& o' h&drogen internal comustion engine
comined ?ith oen steam anine c&cle reco%ering ?ater and ?aste heat0
!nternational ournal o' H&drogen Energ& 21:4751-4/-20
1F Miller E@, Hendrics ", +eterson B0 Modeling energ& reco%er& using
thermoelectric con%ersion integrated ?ith an organic anine ottoming c&cle0
ournal o' Electronic Materials 2.:485123/140
11F Saleh B, Ioglauer K, @endland M, haust gas heat e>changer 'or truc alications ?ith
con%entional and state o' the art heat trans'er enhancements0 Alied "hermal
Engineering 21:45.47/-90
19F emmon E@, Mcinden M=, Huer M0 J!S" re'erence 'luid thermod&namic
and transort roerties / E
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1.F Cengel OA, Boles MA0 "hermod&namics an engineering aroach0 3th ed0
ondon5 McKra?/Hill: 280
2F @ei D, u Y, $ X, Ku 0 +er'ormance anal&sis and otimiNation o' organic
anine c&cle (=C) 'or ?aste heat reco%er&0 Energ& Con%ersion and Management
29:-851114/111.0
21F Mago +, Chamra M, Srini%asan I, Soma&aLi C0 An e>amination o' regenerati%e
organic anine c&cles using dr& 'luids0 Alied "hermal Engineering
28:285..8/190
22F @ang EH, Xhang HK, Xhao O,
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28F iming ian Y0 Heat reco%er& 'rom internal comustion
engine ?ith anine c&cle: 210 +roceedings o' +o?er and Energ& Engineering
Con'erence, 0 1/-, March 28/41, 21, Chengdu, China0
2.F Hussain Z, Brigham D0 =rganic anine c&cle 'or light dut& assenger %ehicles0
Directions in Engine/E''icienc& and Emissions esearch (DEE) Con'erence:
2110 +resentation a%alaile at
htt5GG???10eere0energ&0go%G%ehiclesand'uelsGd'sGdeer\211G?ednesda&Gresentat
ionsGdeer11\hussain0d' , =ctoer 4/3, 211, Detroit, Michigan, $SA0
4F !ncroera
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.igure captions
.igure %0 Schematic o' a simle C0
.igure (0 Schematic o' a t&ical C ?aste heat reco%er& s&stem 'rom !CE e>haust
gases0
.igure )0 T-s rocess diagrams0 a) @ater, ) 124 and c) 2-7'a0
.igure *0 Schematic o' the T- Q́ diagram used 'or the inch/oint anal&sis in the C
heat e>changer0
.igure +0 Algorithm 'or the C thermod&namic model0
.igure ,0 "hermal and h&draulic characteristics o' the e>haust gases as a 'unction o' the
numer o' tues in the e%aorator 'or di''erent cross 'lo? geometries0 a) e,
) Ju, c) h, d) ε , e) β , ') W p0
.igure -0 "he three Nones o' the heat e>changer considered 'or modeling uroses0
.igure /0 Algorithm 'or the heat e>changer model0
.igure 00 C e''icienc& as a 'unction o' the e%aorating ressure 'or the ?oring 'luids
studied0
.igure %10 "urine outletGinlet e>ansion ratio (v-Gv4) as a 'unction o' the e%aorating
ressure 'or the ?oring 'luids studied0
.igure %%0 @oring 'luid mass 'lo? rate as a 'unction o' the e%aorating ressure 'or
the ?oring 'luids studied0
.igure %(0 C net o?er outut as a 'unction o' the e%aorating ressure 'or the
?oring 'luids studied0
.igure %)0 C e%aorator e>erg& destruction rate as a 'unction o' the e%aorating
ressure 'or the ?oring 'luids studied0
.igure %*0 C e%aorator e>erg& e''icienc& as a 'unction o' the e%aorating ressure
'or the ?oring 'luids studied0
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2ale %0 ehicle test conditions0
=erating
condition
( ["pm]
7 [ ( ]
89E¿̄¿
6 [&m/h]
*e[&W ]
ḿg[g /s ]
g ,∈¿T ¿
[ ' ]
Q́available[&W ]
1 2 1208 940. 3024
2 2 7 0.1 4109 -023 190 9.0 .0-9
4 2 1 1097 401 8018 210 82.09 12091
- 2 17 2047 2303 10.3 240. 8709 1709
7 2 2 2098 2407 120.3 270. 83802 1308.
3 4 1904 8904 10
9 4 7 0.8 702 3088 2708 8.90. 19099
8 4 1 10.7 -.09 14039 4107 .4.03 2404-
. 4 17 2087 -802 1.0.9 490. .3809 2.0-9
1 4 2 4099 -902 2304. -40 .8.08 4-07.
11 - 270- 83.0- 1303
12 - 1 10.8 390 180-7 -40 1108 47027
14 - 2 40.8 390 49019 7.09 17204 72081
2ale (0 Euations used to calculate the e>haust gas roerties (a)0
Seci'ic heat caacit&
g/1 I /1F c
pg=956.0+0.3386 ∙ T
g−2.476010
−5∙ T
g
2
D&namic %iscosit&
J s m/2F μg=10
−60 (3.807+4.731010−2∙ T g−9.945010
−6∙T g
2 )
+randtl numer *"=0.774+1.387010−4
∙T g+1.863010−7
∙ T g2+7.695010
−11∙T g
3
"hermal conducti%it&
@ m/1 I /1F & g=10
−30 (4.643+6.493010−2 ∙T g )
Densit& g m/4F ρg=1.665−2.404010−3
∙ T g+1.121010−6
∙T g2
(a)"he euations are %alid 'or 400:T g:1200 ' 0
-2
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2ale )0 Main thermoh&sical roerties o' the ?oring 'luids studied (124, 2-7'a
and ?ater)0
@oring'luid
Categor& p
c"
[ 9*a ]
T c"
[ ' ]
Jormal oiling
temerature[℃ ]
pcond, T 424 I
¿̄¿
Sloe o' thesaturation %aor line
@ater / 2203 9-30.7 1 0124 Jegati%e
124 HCander e''icienc&, ηt 6G/ 1 6G/ 13
+um e''icienc&, η p 6G/ 1 6G/ 01
@ater e%aorating
ressure, pe%a6G/ 01 ar 6G/ 1
@ater condensation
ressure, pcond6G/ 01 ar /G6 -
=rganic 'luids e%aorating
temerature, T e%a6G/ 1 PC 6G/ 7
=rganic 'luidscondensation temerature,
T cond
6G/ 1 PC /G6 .
2ale +0 Main characteristics o' e%aorators 1 and 20
Characteristic E%aorator 1 E%aorator 2
Jumer o' tues, ( t -4 48
"ues diameter, ! i (m) 01 03
Distance et?een tues, δ (m)(a)
0- 02
"ues length, + (m) 07 09
"hicness, e (mm) 07
E>ternal diameter, !e$t (m) 011
(a) "ues in an euidistant he>agonal arrangement0
-4
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2ale ,0 Heat e>changer characteristics 'or e%aorators 1 and 2 (oerating condition 14,
see "ale 1)0
E%aorator @oring
'luid
"hermal resistance,
1#-
I @/1F
Area
m2F
=%erall heat trans'er
coe''icient,U @ m/2 0I /1F
1
@ater 029
0397
7707
124 04. 480-
2-7'a 04- -403.
2 @ater 02- 071 97019
2ale -0 !ncrease in the !CE thermal and %ehicle mechanical e''iciencies 'or the three
Cs studied0
C@oring
'luid
!ncrease o' thermal e''icienc& F !ncrease o' mechanical e''icienc& F
(4) (.) (14) (4) (.) (14)
1
@ater 2011 20.8 4072 1702- 170.7 170.-
124 1099 2071 20.9 12084 140-4 140-4
2-7'a 10- 10.. 2047 1013 103- 1034
2
@ater 043 0.3 102 203- 701- 70-1
124 0.3 1017 1017 30.3 3017 7024
2-7'a 087 104 103 3018 7074 -09.
4 @ater 04 092 087 2019 4084 4089
--
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Heat exchanger
Turbine
Condenser Pump
Qin
Qout
W t
W p
(2)
(3)
(4)
.igure %0 Schematic o' a simle C0
Heat exchanger
Condenser
PumpTurbine
TWC
Generator
Air
Air + ue!
"xhaust gases
2 3
4#
.igure (0 Schematic o' a t&ical C ?aste heat reco%er& s&stem 'rom !CE e>haust
gases0
-7
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T
( $ )
T
( $ )
T
( $ )
2%%
3%%
4%%
&%%
'%%
%%
%%
'%% %% #%%% #2%% #4%% #'%% #%%
s (*,g$)
2%%
3%%
4%%
&%%
'%%
%%
%%
'%% %% #%%% #2%% #4%% #'%% #%% 2%%%
b) -#23
a) Water
c) -24&a
% #%%% 2%%% 3%%% 4%%% &%%% '%%% %%% %%% .%%%2%%
3%%
4%%
&%%
'%%
%%
%%
.%%
#%%%
/dea!-ea!
.igure )0 T-s rocess diagrams0 a) @ater, ) 124 and c) 2-7'a0
-3
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Wor,ing !uid
T
( $ )
Q (,W)
T g0out
T g0pp
T 2x
T g0in
T 2
T 3
1T pp
T
.igure *0 Schematic o' the T- Q́ diagram used 'or the inch/oint anal&sis in the C
heat e>changer0
-9
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/nput ariab!es
Thermodnamicconditions
!o5 ba!ance ineaporator
or eachexperimenta!condiction
Ca!cu!ateeicienc andthermophsics
properties
Ca!cu!ate po5er output and
5or,ing !uid !o5
6ho5 resu!ts
or eacheaporatingpressure
7atabaseinterace
-eprop .8%
Wor,ing !uid0
T cond0 pcrit
.igure +0 Algorithm 'or the C thermod&namic model0
-8
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#% 2% 3% 4% &% '% % % .% #%%
N t N t
#% 2% 3% 4% &% '% % % .% #%%
#% 2% 3% 4% &% '% % % .% #%% #% 2% 3% 4% &% '% % % .% #%%
#% 2% 3% 4% &% '% % % .% #%% #% 2% 3% 4% &% '% % % .% #%%
%
&%%%
#%%%%
#&%%%
2%%%%
2&%%%
3%%%%
- e
'%
%
%
.%
#%%
##%
#2%
h ( W m
9 2 $
9 # )
( : )
( m 2 m
9 3 )
&%
#%%
#&%
2%%
2&%
3%%
%
#%
2%
3%
4%
&%
'%
%
; u
#%
2%
3%
4%
&%
'%
%
%
.%
#%%
%
%8&
#
( x # %
& P a )
#8&
a) b)
c) d)
e) f)
6
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"aporating=one
Preheating=one
6uperheating=one
T 2
T g0out T g0pp T g0pp2 T g0in
T 3T 3x
.igure -0 "he three Nones o' the heat e>changer considered 'or modeling uroses0
7
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-esu!ts o thethermodnamic
mode!
/nterace 5ith-eprop .8%
-ununti!
conergence
7einegeometrica!
characteristics
/nitia! conditions>
temperature and!enght
or each sub9component
"xhaust gascharacteristics
-epeatca!cu!ations
or eachsub9component
9;?T method
Ca!cu!ate!o5 ba!ance
or eachsub9component
Ca!cu!ate
exhaust gasestemperature andsub9component
!enght
Ca!cu!ateheat exchanger
po5er outputand eicienc
.igure /0 Algorithm 'or the heat e>changer model0
71
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%
%8%2
%8%4
%8%'
%8%
%8#
%8#2
%8#4
%8#'
%8#
%82
% # 2 3 4 &"aporating pressure (@Pa)
Water -#23-24&a
.igure 00 C e''icienc& as a 'unction o' the e%aorating ressure 'or the ?oring 'luids
studied0
%
&
#%
#&
2%
2&
3%
v 4 + v 3
% # 2 3 4 &
"aporating pressure (@Pa)
Water -#23-24&a
.igure %10 "urine outletGinlet e>ansion ratio (v-Gv4) as a 'unction o' the e%aorating
ressure 'or the ?oring 'luids studied0
72
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W o r , i n g ! u i d ! o 5 ( , g + s )
"aporating pressure (@Pa)
%
%8%&
%8#
%8#&
%82
%82&
% # 2 3 4 &
Water -#23-24&a
Ap8 condition #3Ap8 condition .Ap8 condition 3
.igure %%0 @oring 'luid mass 'lo? rate as a 'unction o' the e%aorating ressure 'or
the ?oring 'luids studied0
;
e t p o 5 e r o u t p u t ( , W )
"aporating pressure (@Pa)% # 2 3 4 &
%
#
2
3
4
&
'
Water -#23-24&a
p8 condition #3p8 condition .p8 condition 3
.igure %(0 C net o?er outut as a 'unction o' the e%aorating ressure 'or the
?oring 'luids studied0
74
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"aporating pressure (@Pa)
" x e r g d e s t r u c t i o n r a t e ( , W )
3
4
&
'
.
#%
##
% # 2 3 4 &
Water0 op8 condition .-#230 op8 condition .-24&a0 op8 condition .
.igure %)& C e%aorator e>erg& destruction rate as a 'unction o' the e%aorating
ressure 'or the ?oring 'luids studied0
"aporating pressure (@Pa)
% # 2 3 4 &
"
a p o r a t o r e x e r g e i c i e n c ( B )
%8%&
%8#
%8#&
%82
%82&
%83
%83&
%84
%84&
Water0 op8 condition .
-#230 op8 condition .-24&a0 op8 condition .
.igure %*& C e%aorator e>erg& e''icienc& as a 'unction o' the e%aorating ressure
'or the ?oring 'luids studied0
7-
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W o r , i n g ! u i d ! o 5 ( ,
g + s )
"aporating pressure (@Pa)
%8& # #8& 2 28& 3 38&%
%8%2
%8%4
%8%'
%8%
%8#
%8#2
%8#4
Water -#23-24&a
p8 condition #3p8 condition .p8 condition 3
.igure %+0 @oring 'luid mass 'lo? rate as a 'unction o' the e%aorating ressure 'or
the ?oring 'luids studied using e%aorator 10
%
#%2%
3%
4%
&%
'%
%
%.%
#%%
( : )
%8& # #8& 2 28& 3 38&
"aporating pressure (@Pa)
Water
-#23-24&a
p8 condition #3
p8 condition .p8 condition 3
.igure %,0 Heat e>changer e''ecti%eness as a 'unction o' the e%aorating ressure 'or
the ?oring 'luids studied using e%aorator 10
77
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# #8& 2 28& 3 38&"aporating pressure (@Pa)
; e t p o 5 e r o u t p u t ( , W )
%8&%
%8&
#
#8&
2
28&
3
Water -#23-24&a
p8 condition #3p8 condition .p8 condition 3
.igure %-0 C net o?er outut as a 'unction o' the e%aorating ressure 'or the
?oring 'luids studied using e%aorator 10