Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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There are numerous situa-tions wherein i-t is necessary
to hea~ large flows of a process stream and wherein low
pressure losses are mandated. Cases in point are air pre-
heaters, particularly those employed in incineration sys-
tems. Such heating of large flows a-t low pressure losses
has been difficult to achieve by prior art installations in
terms of capital costs~ thermal efficiency and the like.
BRIEF STATEMENT OF INVENTION
The present disclosure solves problems of prior art in-
stallations in a parti~ularly use~ul, novel, unobvious and
facile way, A heater is fabricated having a cylindrical s ;~
sleeve, with a first end and a second end, mounted in a
cylidrical shell. The shell has a first end and a second
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end each corresponding with that of the sleeve. The first
ends converge to form a convection input passage therebetween,
-the second ends diverge to form a radiant zone therebetween.
Hot gas passes between the shell and the sleeve through the
radiant zone and then the convection input zone, while -the
process stream passes through an inner flow space disposed
inward of the sleeve. A baffle is mounted within the sleeve ~
in its first end to channel the process stream into a convec `
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tion output passage boardéred inwardly by the baffle and out-
wardly by the sleeve. Extended surface projects from the
sleeve into the convection input zone and additionallextended
surface projects from the sleeve into the convec-tion output
passage.
Accordingly, one object of this invention is to heat
large flows at low pressure drops.
Another object of this invention ig to improve thermal
efficiency.
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Still ~nother object o~ this invention is to ~abricate a
heater of the type here contemplated and employing inexpensive
~aterials.
Still another object of this invention is to fabricate a
heater of the type here contemplated which accommodates either con-
ventional burners or an external source as a means to provide the
hot gas.
S~ill another object of the invention i5 to fabricate a
heater of the type here contemplated which can operate either co-
currently or countercurrently.
` Still another object of this invention is to fabricate a
heater of the type here conkemplated wherein allowance can be made
conveniently for differential thermal expansion of parts of the
heater.
Still another object of this invention is to fabricate a
heater of the type here contemplated whlch is particularly well
adapted to incineration systems wherein the process stream is com-
bustion air and the hot gas is derived from the material being in-
cinerated. Fuel requirements needed to achieve incinerakion tem-
peratures are reduced drastically thereby.
Still another object o~ this invention is to provide a
heater o~ the type here contemplated wherein the hot gas space is
operable at a superatmospheric pressure so that structural re~uire-
ments of the sleeve can be reduced.
Still another object of this invention is to fabricate a
heater of the type here contemplated which is simple to de,ign, build
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and maintain.
Still another object of this inventi.on is to fabricate a
hea~er of the ty~e here contemplated which is suited well otherwise
to its intended Eunctions. ' .
DESCRIPTION OF DRAWINGS
The foregoing and other objects, features and advantages
- will appear more fully from detailed descriptions of preferred embodi-
ments of the in~ention which follow along with claims which also
follow, all viewed in conjunction with accompanying drawings wherein:
Fig~ 1 is a vertical view in section of a heater according
to this invention with longitudinal fins mounted on the sleeve to
serve as the extended surface.
Fig. 2 is a vertical view in section of another embodiment
of the heater according to the present invention with fins wound
splrally on the sleeve to serve as theextended surface.
; Fig~ ~ l S a broken sectional view of a portion of the
sleeve with studs serving as the extended surface.
Fig. 4 is an enlarged detail view partly in section showing
fins of Fig. 2.
DESCRIPTION OF PREFERRE~ EMBODIMENTS
As seen in Fig. 1 a heater generally designated 11 includes
a vertical cylindrical shell 12 supported by a suitable structural
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~ system. A sleeve 13 is mounted in the shell 12 to separate a cylindri~
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cal innsr flow space 14 from an annular outer flow space 15. The
sleeve 13 has a flrst end 16 and a second end 17 each of which
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corresponds with a flrst end 18 and a second end 19 respectively of
the shell 12. The first ends 16, 18cvnverge to form a convection
input passage 21 therebetween, while the second ends 17, 1.~ di.verge
to form a radiant zone 22 therebetween. To effect the foregoing,
~i the sleeve 1~ includes a duct 23 which penetrates into the shell 12
and is connected in sealed engagement with a hood 24, which in turn
: is connected in sealed engagement with a cylindrical portion 25,
which in turn is connected in sealed engagement with a disk like .
partition section 26, which in turn is connected in sealed engage-
) ment with another duct portion 27 which also penetrates the shell
12. The sleeve 1~ can be supported at its top, in which case di-
: ferential thermal expansion between the sleeve 1~ and the shell 12
can be taken care of by providing a bellows 28 between the duct 27
; and the bottom 29 of the shell 12. Altexnately the sleeve 13 can be
i supported anywhere along its length with expansion being accommo~
dated phrtially in each direction, in which case another bellows
~L could be provided between a top 32 of the shell 12 and the duct 2~
~ccording to this invention the process stream 33 is passed
;. thxough the inner flow space 14. Flow of the process stream 33 is :
) shown here to be downward in countercurrent heat exchange relationship
with upward ~low of the hot gas 34, but it is ~ometimes desirable to
flow the process stream 3~ cocurrently with the hot gas 34 and this
cocurrent flow also can be accomplished by means of the heater 11 of
this invention as will be understood by those skilled in heater design.
~ The process stream is shown to enter via the duct 23, and the hood 2~ ::
and to be diverted by a baffle ~5 disposed in the first end 16 o~ the
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sleeve 13 to conduct the prccess stream 33 into an annular convection
output passa~e ~6 which is boarAered inwardly by the baffle 35 and
outwardly by the sleeve 13. From the convection output passage 36
the process stream ~ passes through the duct 27 to exit the sleeve
1 5 .
The hot gas 34 may be provided by burning a ~uel in thP
radiant zone 22 of the outer flow space 15 using one or more burners
37 (which penetrate the bottom 29 o the shell 1~) or some other
source of the hot gas ~4 may be employed. Usually the hot gas 34
will give up some of its heat by means of radiant transfer in the
radiant zone 22. The size of the radiant zone 22 is a function of
the temperature and constitution of the hot gas 34 and/or the com-
bustion space required. At very low radiant temperatures or low heat
input rates, the xadiant zone 22 required could be practically nil,
in which case the heater 11 would operate on substantially convec-
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tion principles.
From the radiant zone 22 the hot gas 34 passes throughthe convection input passage 21 boardered inwardly by the first end
16 of the sleeve 13 and outwardly by the first end 18 o~ the shell
12. From ths convection input passage 21 the hot gas 34 is collected
in a plenum 38 boardered by the hood 24 and the top 32 o the shell
12 whence the hot gas 34 exits via a line ~9.
The shell 12 is lined with an insulating refractory 41 to
reduce heat losses to the surroundings. This re~ractory 41 can be
~pplied internally (as shown~ ore~ternally of the shell 12, depending
upon circumstances. If the refractory ~1 is applied externally of
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the shell 12, the shell 12 will run hotter~ thus reducing
temperature differentical between the shell 12 and the
sleeve 13.
It is important to extrac-t heat Erom the hot gas 34 by
means of convective heat transfer as well as by radiant
heat transfer. Toward -this objective the disk like parti-
tion 26 channels the hot gas 34 into the convection input
passage 21 which is boardered between the sleeve 13 and the
shell 12 and is in flow series with the plenum 38.
Extended surface used in this heater may be in the form
of longitudinally organized fins 42 as shown in Fig. 1, hel~
ically organized fins ~3 ~ ~hown in Fig. 2, studs 44 as
shown in Fig. 3 or any other commerically available system
of like kind. As shown in Fig. 1 the longitudinal fins 42 ~ ;
extend from the sleeve 13 outwardly into the convection in- ;
put passage 21 ~o provide a large metal surface area in heat
exchange relationship with the hot gas 34 so as to take heat
therefrom. The longitudinally organized fins 42 al50 ex-
tend inwardly from the sleeve 13 into the convection output
passage 36 so ~s to conduct heat to the process stream 33
without need for passing the process stream 33i through tubes
(at a consequent pressure loss penal~y). Heat transfer
to the sleeve 13 via the disk like partition section 26 and
the duct 27 at the second end 17 is substantially by means
0!~ radiant heat transf~r. The same priciples are involved
inthe embodiments of Figs. 2 and 3 with the only differeces
being that the extended surfaces used therein are the
helically organized fins 42 and studs .~44 respectively.
If desired the outer flowspace 15 may be operated at
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superatmospheric pressure to reduce pressure differential between
the inner 1~ and the outer lS flow spaces, thereby reducing wall
~hi-kness requiremen.ts of the sleeve 1~.
It will be understood by those familiar with heater design
that various deviations may be made from the described preferred em-
bodiments, without departing from a main theme of invention set
forth in a claim which follows.
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