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8$oatin! Head STHE TEMA T
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A Ne) 9art/+ 7n$# for SHTE
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Cross Baff$es
' Baff$es ser,e t)o *ur*oses5
' Divert (direct) the flow across the %und$e to o%tain a
hi!herheat transfer coefficient+' Support the tubes for structura$
ri!idit#0 *re,entin! tu%e
,i%ration and sa!!in!+
' When the tube bundle employs baffles 0' the heat transfer
coefficient is hi!her than the coefficient for
undistur%ed f$o) around tu%es )ithout %aff$es+' 8or a %aff$ed
heat e chan!er the hi!her heat transfer
coefficients resu$t fro( the increased turbulence +' the
velocity of fluid fluctuates %ecause of the constricted area
%et)een ad1acent tu%es across the %und$e+
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T#*es of Baff$e 9$ates 5 Se!(enta$ Cut Baff$es
' The sin!$e and dou%$e se!(enta$ %aff$es are (ost frequent$#
used+
' The# di,ert the f$o) (ost effecti,e$# across the tu%es+
' The %aff$e s*acin! (ust %e chosen )ith care+
' 7*ti(a$ %aff$e s*acin! is so(e)here %et)een :;< - =;< of
the
she$$ dia(eter+' Baff$e cut of >?
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T#*es of Baff$e 9$ates
Tri*$e Se!(enta$ Baff$es
Dou%$e Se!(enta$ Baff$es
The triple segmental bafes are used or lowpressure
applications.
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T#*es of Baff$e 9$ates
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T#*es of Baff$e 9$ates
Disc and ring bafes are composed o alternating outerrings and
inner discs, which direct the ow radially
across the tube eld. The potential bundle-to-shell bypass stream
is
eliminated
This bafe type is very e ective in pressure drop toheat trans er
conversion
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T#*es of Baff$e 9$ates
n an ori ce bafe shell-side- uid ows through theclearance
between tube outside diameter andbafe-hole diameter.
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Therm-!ydraulic "nalysis o !eat#$changer
' nitia$ Decisions+' Tu%e side Ther(a$ Ana$#sis+
' Ther(a$ ana$#sis for She$$ side+' 7,era$$ Heat Transfer
coefficient+' H#drau$ic Ana$#sis of Tu%e side+' H#drau$ic Ana$#sis
of She$$ side+
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"luid Allo#ation $ %ube Side
' Tu%e side is *referred under these circu(stances5' 8$uids
)hich are *rone to fou$' The hi!her ,e$ocities )i$$ reduce %ui$du*'
Mechanica$ c$eanin! is a$so (uch (ore *ractica$ for tu%es than
for
she$$s+' Corrosi,e f$uids are usua$$# %est in tu%es' Tu%es are
chea*er to fa%ricate fro( e otic (ateria$s' This is a$so true for
,er# hi!h te(*erature f$uids requirin! a$$o#
construction' To ic f$uids to increase contain(ent' Strea(s )ith
$o) f$o) rates to o%tain increased ,e$ocities and
tur%u$ence' Hi!h *ressure strea(s since tu%es are $ess e *ensi,e
to %ui$d stron!+
' Strea(s )ith a $o) a$$o)a%$e *ressure dro*
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8$uid A$$ocation 5 She$$ Side
' She$$ side is *referred under these circu(stances5' iscous
f$uids !o on the she$$ side0 since this )i$$ usua$$#
i(*ro,e the rate of heat transfer+
' 7n the other hand0 *$acin! the( on the tu%e side )i$$usua$$#
$ead to $o)er *ressure dro*s+ ud!(ent is needed+
' Low heat transfer coefficient: ' Strea( )hich has an
inherent$# $o) heat transfer coefficient
such as $o) *ressure !ases or ,iscous $iquids 0 this strea(is
*referentia$$# *ut on the she$$-side so that e tendedsurface (a# %e
used to reduce the tota$ cost of the heate chan!er+
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Options for Shell-Side Thermal nalysis
' !ern"s inte#ral method
' $ell-Delaware method
' Stream analysis method
' %ecent ðods
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!ern ðod ofS' LL- D-T*$ ' T +,' % nalysis
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no)$ed!e for So$,in! True ndustria$ 9ro%$e(s 5Dona$d F ern
' True %e$ie,er of *ro,idin! 2no)$ed!e for use of
so$,in!run-of-the-(i$$ *ro%$e(s+
' Donald ./ !ern ward: 0,h /' n honor of Dona$d F+ ern0 *ioneer
in *rocess heat
transfer0 the Di,ision reco!ni.es an indi,idua$ s e *ertise ina
!i,en fie$d of heat transfer or ener!# con,ersion+
' There is no true f$o) area %# )hich the she$$-side
(ass,e$ocit# can %e co(*uted+
' 8ictitious ,a$ues for equi,a$ent dia(eter and (ass ,e$ocit#are
to %e defined+
' These are %orne out %# e *eri(ent+
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8$o) 9ast Tu%e Bund$es 5 7utside 8i$( Coefficient
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ern s nte!ra$ Method
' The initia$ atte(*ts to *ro,ide (ethods for ca$cu$atin!
she$$-side *ressure dro* and heat transfer coefficient )ere %ased
one *eri(enta$ data for t#*ica$ heat e chan!ers+
' 7ne of these (ethods is the )e$$-2no)n ern (ethod0 )hich)as an
atte(*t to corre$ate data for standard e chan!ers %# asi(*$e
equation ana$o!ous to equations for f$o) in tu%es+
' This (ethod is restricted to a fi ed %aff$e cut >?<
andcannot adequate$# account for %aff$e-to-she$$ and tu%e-to-
%aff$e $ea2a!es+
' A$thou!h the ern equation is not *articu$ar$# accurate0 it
doesa$$o) a ,er# si(*$e and ra*id ca$cu$ation of
she$$-sidecoefficients and *ressure dro* to %e carried out
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Ma1or Ste*s in Desi!n
' nitia$ Decisions+' Tu%e side Ther(a$ Ana$#sis+
' Ther(a$ ana$#sis for She$$ side f$o)+' 7,era$$ Heat Transfer
coefficient+' H#drau$ic Ana$#sis of Tu%e side+' H#drau$ic Ana$#sis
of She$$ side+
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nitia$ Decisions
' S*atia$ a$$ocation of f$uid+' Deter(ination of f$o)
,e$ocit#+
' nitia$ !uess for nu(%er of tu%es+' Correction for standard
tu%e dia(eter+' Effect of nu(%er of tu%es on tu%e $en!th/+
