Art Antonio

8/9/2019 Art Antonio

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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

2


21/56

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,


22/56

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


23/56

+&%& 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

24


24/56

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


25/56

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

27


26/56

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

23


27/56

´ 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


28/56

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

28


29/56

o?er outut, Ẃ et , as a 'unction o' the e%aorating ressure 'or the ?oring 'luids

studied0


30/56

!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


31/56

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

41


32/56

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


33/56

"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

44


34/56

"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-


35/56

%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

47


36/56

-& 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


37/56

.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


38/56

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,


39/56

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


40/56

.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


.igure %*0 C e%aorator e>erg& e''icienc& as a 'unction o' the e%aorating ressure

'or the ?oring 'luids studied0

-


41/56


42/56

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


43/56

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


47/56

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


48/56

/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


51/56

-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


52/56

%

%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


72


53/56

W o r , i n g ! u i d ! o 5 ( , g + s )


%

%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


54/56


" 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



% # 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-


55/56

W o r , i n g ! u i d ! o 5 ( ,

g + s )


%8& # #8& 2 28& 3 38&%

%8%2

%8%4

%8%'

%8%

%8#

%8#2

%8#4

Water -#23-24&a


.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&


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


56/56

# #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


.igure %-0 C net o?er outut as a 'unction o' the e%aorating ressure 'or the

?oring 'luids studied using e%aorator 10

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Art Antonio