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Патент USA US2404826

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July 30, 1946.
P_ R, gAsslDY
‘ 2,404,826
Filed June 3,1942
'V/ll///////////!////////// I
. Cassz'dy
Patented July 30, 1946
l’erry R‘. Cassidy, Darien, Conn-‘i, assignor ‘to ‘The
Babccck & Wilcox Company, Jersey City, No.1 .-,
aucorporation of New J ersey
Application June 3, 1942, Serial No. 445,588
11 Claims;
(Cl. 122-235) ‘
The invention" herein disclosed relates to heat'
exchange apparatus particularly adapted to the ,
transfer of heat between ?uids through the wall
contemplated ' ‘whereby a plurality of ‘such-1 units
of a metallic tubular element.
When heat is to be transferred from a fluidout
side of a tube to a ?uid inside of a tube, or vice
versa, there is a resistance to the ?ow‘ of heat at
surface swept by the movingfluid‘at ‘minimum
fora given temperature excess of one ?uid over
source of heat.
may be disposed in the ‘path' ofra moving ?uid,
either gaseous or liquid, witlrthe entire‘extension
resistance to the ?ow 'of‘such‘ ?uid; Other *em
bodiments utilizing di?erentz‘forms of ‘extensions 7
may conveniently “be arranged to form an‘ inr
pervious' wall structure; associated'with'a fur
the boundary of each fluid and in the material
nace for example, where ordinarily ‘only‘a-iportion
of the tube, the cumulative e?ect of these thermal
resistances determining the heat transfer rate 10 of the extension surface is exposed directly to'a
the other. In manycascs of practical importance,
For "any condition of ‘ service; the‘ arrangement
heat is transferred from a gaseous fluid outside
of the tube to a liquid within the tube, the liquid
remaining as such’ or boiling to, a vapor; and
exposed outer ‘surface, forexample, is conducted‘
of the extension ‘is such‘v that-heat received 'at‘its;
through the material of ' the extension to its
juncture ‘with the tubular member- without‘ ex-,
under these‘ conditions, the boundary of gas out
side of the tube affords a much greater resistance
to heat flow than the tube metal and-inside?uid
boundary combined, andacts to control and limit
the rate of heat transfer.
cessive temperature differential betweenthe ex-v
treme outermost portion of ‘the extension ‘and its
innermost ‘ portion -or root: This involves suitable ~
20 attachment: of 'the'extension‘ to ~ the tubular - base '
sistance isin the boundary of a gas outside of a
portion‘ to provide thermal contact of su?icient'
area and conductivity to avoid'overheating the
tube, and it is desiredto increase the rate of heat
part farthest from-the. tube, the attachment be
transfer, ‘it is common practice to increase the ex~
ternal surface area of the tube, and thus the gas
ing also made'in such ‘manner as to'prevent ex‘- '
Therefore, when the controllingwthermal re~
cessive stresses-being setup in“ the 'tub‘e‘ldue ‘to
differential thermal ‘expansion and contraction of‘
themetal of the tube and'that of ‘the'extension.
In the furtherance of these objects'it‘is' pro
posed to providela composite form of extension
boundary area, by providing‘ metallicextensions
on the outside of the tube
the form of fins,
studs or pins; the manner oflconstructing such
extended surface units generally involving the
attachment of a solid piece of metal, to the tube 30 wherein differentimaterialscare combined,“ both
of which are conductors otheat'butusually‘in‘
by means of a pressure joint or bythe continuous
di?erent degrees, with one more‘reiractory-to
heat and serving as a‘shieldbr‘jacket‘for‘the
brazing or welding.
When fluid carrying tubes are used in the walls'
In most instances, it'will probably be found‘
of furnaces as outside boundaries or partitions, 35
most suitable to form theouter shield Qr'jacket
especially those, of steam boilers, they areycom
of ‘relatively thin metal; the selection of‘the'kind
monly spaced apart in a‘ row with their ends
metallic juncture such as results from, soldering,
of metal being determ'inedinpart ‘by-the char
similarly spaced and suitably connected tohead
acter of service for which the heat "exchange unit
ers for the desired ligament strength.- The‘spaces,
between such wall tubes
generally been
closed by metallic extensions on individual tubes,
with or without the addition of refractory mate
rial,,to provide an exposed surface bridging the
metal of the tube and thence to the ?uid within,
is intended, and in part‘by‘ its :cost: Accordingly
it is desirable to form thesheath or'jacket ‘of a‘
metal of relatively high resistance to,corr0sion,
with‘ reference to itheltemperatures, and-‘to the
character of ?uid,‘ to which it may be exposed.
The other portion of ‘the composit‘e'extension
is disposed between ‘the metal ‘shield or jacket and
the tube. ,
the metal ‘of the tubular member as a heat trans
space between tubes, from which surface ,heat is ,
conducted through the, extension, met-alto the
A purpose ‘of the present invention is to‘pro
vide a heat exchange unit especially adapted to
the transfer of heatbetw-cen fluids of different,
temperatures, one ?uid being carriedwithin a:
metallic tubular memherand the exterior stirface ‘of the member being extended to provide in~
creased area of exposure to the other ?uid.‘ Cer
tain particular embodiments of ‘the invention are
fer medium, for the transfer of heat‘irom the
jacket to the tubularmember or from the tubular
member to the jacket‘depending ‘on the relative
? temperatures inside‘and‘outside of‘the tubular
member as affecting the direction of *heat ‘flow.
As a heat transfer medium it is proposed to use
a material diiferent‘from that of the sheet metal
q jacket, selected for ease or economy of applica
tion, and of suitable heat carrying capacity for
pansion to the same end. . To avoid excess stresses
the temperature conditions under which it must
without compensating coe?icients of expansion
function in service.
the sheet metal jacket may be so formed as to
yield under stresses within the elastic limit.
The filler material may be solid at ordinary
temperatures and remain solid during operation
at higher temperatures, metallic or non-metallic,
and may be shaped to ?t the jacket and the tube
before the jacket is attached to the tube, or it
When a liquid is used as the ?ller and it re
mains liquid, or when a solid is used that be
comes liquid, in operation, the expansion and con
traction conditions may be met, by forming the
‘sheet metal jacket so that it yields to changes
after the jacket is attached to the‘ tube. It may 10 in the volume of the ?ller while keeping its metal
may be molten and poured into the jacket space '
have metallic fusion or alloy attachment'to'the -'
‘stress within the elastic limit.
jacket, or to both jacket and tube, according
be left un?lled above the liquid to reduce the
maximum pressure exerted by the ?ller at its
highest temperature excess over that of the jacket,
to conditions of cost in relation to thermal car
Also, a space may
rying capacity. For example, a sheet steel jacket,
with copper ?lling would be suitable for steel 15 when thermal conditions are such as will not
overheat the jacket around the un?lled space.
tube water walls, the copper being ?tted as a’
With a filler that is liquid in operation the heat
solid block or poured molten.
transfer between the tube and the jacket is not
The ?ller material may be solid at ordinary
limited to pure conduction as is the case of a
temperatures and become molten during opera
tion at higher temperatures,’ and metallic such 20 solid ?ller, or packed solid particles submerged
in a liquid, because convection circulation is set
as lead, or non-metallic, organic or inorganic, in
up in the liquid causing upward flow next to the
cluding diphenyl and such substances known as
hotter metal face and downward ?ow next to the
bath salts for immersion‘ heat treatment of metals
to‘ and at a given high temperature.
" colder one, to carry the heat in the moving liquid
vThe ?ller material‘may be liquid at ordinary 25 from the hotter to the colder face. The jacket
may also be formed so as tobe ?exible to limit
temperatures and remain liquid during operation
internal pressures.
at higher or lower temperatures, such as mercury
A ?ller material that vaporizes duringopera
for example, or an oil, or for very low tempera
tion, a liquid that boils, or a solid that sublimes,
The ?ller material may be liquid at ordinary 30 also conducts heat from a hotter to a colder face
of its enclosure, the vapor forming on the hotter
temperatures and freeze to‘ a solid during opera~
tures abrine. "
face and condensing on the colder face. A space
above the liquid may preferably be left in this ‘
tio'n'at lower temperatures or boil to ‘a vapor dur
ing' operation at higher temperatures.
casev to limit maximum pressures and for the
' The ?ller material may also be composite, for
examplaa liquid in which solid particles are 35 same purpose the jacket form may be a yielding
submerged, the liquid being any one of the liquid
Those skilled in the art are referred to the
media heretofore described and the solids having
accompanying drawing for a more detailed dis»
generally a'higher thermal conductivity as in
- closure of the manner in which the invention ,
the case of metals, especially copper and alumi
num, and preferably being in such form as to 40 may be utilized in certain speci?c forms for
provide‘ a compact mass with relatively little liq
various conditions of service. The embodiments
shown have-been selected by way of example
uid'betweein the solid particles‘when the jacket
and with a view to illustrating a numbervof dif
ferent constructions which may be followed in
space is ?lled. ‘Solids for this purpose include
metal balls; ‘or metals inrgranular form such as
?lings or cutting tool chips, or non-granular par
the practice of this vinvention. These embodi
ticles of metals that cutting tools do notchip.
Such metallic or even non-metallic solid particles
of "greater conductivity than that of the liquid
around'them increase the heat carrying capacity
of ‘the ‘.iacket ?ller over that of liquid alone.
ments it will be noted are of simple construc
tion, thus facilitating manufacture of the ap- ’
paratus and contributing to low cost of produc
tion either in small or large quantities. The
method of their manufacture is also pertinent
to the installation and/or replacement of such
apparatus in the ?eld, the latter being a factor
of considerable importance in reducing the time
is less than for a ?lling of the same metal alone
but cheaper‘ and easier to apply.
The difference in the materials of the sheet
required for restoring normal operating condi
metal jacket and its ?ller, results in differences
in physical properties includingthat of thermal 55 tions, particularly when the installation is remote
from, the place of’original manufacture.
expansion,‘ and in addition, their‘ relative posi—
The accompanying drawing, and the struc'
tions result in'di?'ere'nces intemperature, mean
tures shown therein, may be briefly described as
and" actual local values. My construction makes
it possible to avoid damage due to such differences
Fig. 1, in sectional elevation, shows a steam
and ‘in some cases to advantageously utilize the 60
boiler unit embodying certain features of the
When the ?ller is a material that remains solid
in operation, and the heat flow is inward, the
filler material may be selected to have a suffi
line 2—2, for example, of Fig. 1;
ciently higher coefficient of thermal expansion 65
than that of the jacket so that in spite of a lower
mean temperature. it will expand more than the
iacket and insure close contact between the ?ller
and tube on one side and between the ?ller and
jacket elsewhere for good thermal conduction and
without imposing excess stresses.
On the con
trary, when the heat ?ow is outward, and the
mean’ temperature of the filler is higher than
that'of the jacket, .a different material may be
used with the same or a lower coefficient of ex
Fig. 2 is a fragmentary transverse section along
Fig. 3 is a front elevation of parts shownrin
Fig. 2;
FigsJl and 5 are fragmentary transverse sec
tions similar to Fig. 2 showing modi?cations;
Fig. 6 is a fragmentary transverse section along
‘line 6~6, for example, utilizing parts shown in
Fig.2; and
Fig. '7 shows an, additional modified form of '
the invention, in section along line 1-1, for ex
ample, of Fig. 1.
In detail, the boiler unit of Fig. 1 includes a
combustion'chambersAtrepi-esented as bein'gf?red
with pulverized fuel iburners B ‘and ide?ne‘d by
of “steel might bepréferable, with alower or
higherlcoef?cie'nt of expansion, ‘as required,
wallscC, each or ‘which is illustrative ‘of an :em
The jacket M’may be formed ‘as'a box‘ with one
bodirnent'utilizing ?u-i'd cooling ‘elements con
side open and‘ with edges 48‘ and?ilat the perim
structed and ' arranged '3 as more ‘speci?cally de
eter of? the'sid'e' opening ‘adapted’ to be ‘welded’to
scribed ‘hereinafter. “The ‘hot-‘gaseous products
theiwalllof the tube? 26'as shown. Plates 52’for1n
of combustion resulting from the ‘combustion of
ing‘ the ends'oi the box‘ provide edges 54 'at the
fuel within ‘the ‘chamber ‘A ‘are discharged
perimeter‘ of the'side'opening. also’for welding to
through the opening 1D 'formed between'spa'ced
the‘tube’wall. ‘After the'box has been formed,
?uid'cooling elements 'oi'the‘ inner wall C‘ ‘which 10 irom'a'single plate or from‘ a plurality‘ of1 plates
partitions the combustion ichamber A ‘from the
joined‘ togethenthe box‘ may be ?lled‘with: scrap
up?ow‘ open gas pass E, the gases continuing in
their “?ow through the opening '1" vabovev the
upperendiof avsecond ?uid cooled partition wall
ooppenpreierably- of high purity, andithecopper
integrallybrazed with vthe insidesurfa‘ce ‘of 'the
box and fusedto form? afsolid blocki'of metal with
G downwardly through a second open gas pass 145 in the box‘p'rojectin'g beyond the edges 48, 50,54 'a
Hidisposed :between the ?uid cooled walls Gand
siiilicient 'di'stance"to.allowffor ‘machining to a
concave surface ‘accurately ‘?tting the outside ‘di
Kc Gases leaving the lower portionof pass. H
ameter vof the‘tube'EB, the ?ller material still
areLdirected' across a; row of‘ spaced tubes in and
extending‘asmall 'distancebeyond the welding
thence ‘upwardly through the ‘gas passage M
across other rows of spaced fluid heating tubes 20 edges. The contact'a'rea of the tube maybe thor
oughly cleaned, by brushingior‘bysand-blasting,
forming: for example, ‘the superheater -l‘2, .econ
and the composite extension ls‘uitably clamped
' omizer Miand boiler? section l6; In the arrange
against the tube in‘ position for ‘welding. The as_
ment shown, all of the ‘fluid cooling elements
sembly with the tube 25 may be completed by ?llet
associated ‘ with the combustion ‘chamber A "and
welding'aIo-ng the edges 48, 50, 54 as ‘shown, the
with the ‘gas passes E andiH'are'so constructed
slight shrinkage of the welds tending to draw
and. arranged‘ ast'o constitute a'considerable por
the‘block iof'?ller material 46 against the tube
tion of the boiler heating'surface available'for
wall and‘ to ‘maintain close thermal contact
the generationofisteam or other vapor.
throughout ‘the entire area of contact.
‘The. walls. I8, 20 ‘and '22 constituting ‘outer
'It will’be noted that the walls of the jacket are
boundaries'of the furnace chamber A may be
constructed as shownin ‘Figs. ‘2 and 3 to'include
relatively thin‘and of substantially uniform thick
afplllra‘lityiof wall cooling elements-524 arranged
at suitable "spacings in a, rowracross the ‘width
ness throughout, ‘a‘thic'kness not exceeding the
thickness of thetube‘ metal generally being suffi
ofithe wa1l,‘each element‘comprisin'g a tubular
member ‘2T6 l having. its. ends‘ suitably connected to
relatively small cross-section of jacket metal in
cient. ‘As seen in 'Fig. 2, such walls ‘represent ‘a
comparison with cross-section of the entire e'x
tension, the'cros's-sectional area ‘of jacket metal
being‘less than the cross-sectional area of the
_ element 24 is vpreferably compositely formed to
space within 'the jacket and consequently less
provide a 'greateria'rea ‘of exterior surface {than
is afforded by the tubular base member 25.
Ll i) than the cross-sectional area/of the heat con
shown 'in‘Fi’g. .2; for-an outer‘. furnace wall
Various ?ller materials ‘43, and methods of‘ap
l8, foriexample,‘a plurality of extensions v32 may
plication'have already been discussed. For ex
be’secured to ‘each tubular member'26 insym
ample, it ‘has been stated that a'rnetal such as
metrical arrangement'to provide a substantially
copper could be'poure'd into the box in'a molten
continuous planar surface 34 offset from the
condition, in which case the box or jacket 46
center line of ‘ the row, I preferably ini substantially
coul‘d'be'welded to the tube in an upright posi
tangential relation to'the convex-cuter surfaces
tion,‘with its upper‘endopen, ‘and ‘the molten
of the tubes 26. A small clearance space ‘35¢may
copper poured‘ into the box through its‘ open end,
be left between adjacent extensions 32 on‘ ad
jacent tubes. The spaces‘toithe 'rear ofi‘the ex- ‘ whereupon if'desired- the upper ‘end plate 52 could
be welded to the sides of the box and to the tube
tensionslmay conveniently be ?lled'with afsuit
to complete the assembly. The same general
able ceramic refractory material 3%"app1ied in a
method of procedure may be followed for other
plastic or'semi-plastic condition withafsuitable
molten metals, ‘and ‘for such ‘other materials as
backing of heat insulating material 49. Indi
vidual extensions 32 can be made in relatively f 5 have" been mentioned of a iiuid‘or semi-?uid char
acter. It will be understood that when the. ?ller
short lengths so that a plurality zcan be?tted
material is .a'solid at ordinary temperatures, a
to ‘a -' single ‘tube ‘ length, with ‘a small ‘expansion
block of the material may be preformed and then‘
space 42‘between adjacent extensions, ‘as indi
assembled with a jacket ‘of conforming contour
cated in ‘Fig. v3. ‘ Each extension ‘32 is'in itself
a ‘composite structure, being formed, ofanfouter , against the'tube, the ?ller block preferably pro
jecting beyond the edges ‘of the jacket and the
metallic portion“ serving as an enclosure;for
jacket edges being Welded to the/tube as‘before.
an'inner heat conducting portion 46. For a tube
The extension ‘3'2 is of ‘desirable, form‘in that it
25 of low carbon steel, of about 3%" outside
presents a smooth ‘surface toward the heating
diameter, the material of the jacketM may also
beef low carbon steelfpreferably in plate 'form " zone andin conjunction-with adjacent similar
extensions forms avclosure for the space between
of about 1A" thickness, and the ?ller material
tubes ‘28 and provides aisubstantially' continuous
ll?oficopper, as one example of a suitable ?ller
planar wall surface. The edge portions'et of the
as heretofore described.
box are bent out of the plane ofithe surfaceM to
If the operating temperatures should‘be such
provide an angular‘ recess 58 of‘ at least 909 with
that a different relationship is desired. ‘between
the wall‘ of the‘ tube 25 ‘to accommodates, deposit
the ‘thermal expansion of the jacket andthat of
of-‘weld metal sufficiently largeii'or strength with
the. ?ller, an adjustment'could be made by modi
fying the composition of one or the other of the
at forming a projection beyond the‘ plane of the
materials, for example, instead .of using a low
surface 134. 'The‘rearward surface-16d of the Fox
carbon steel‘forthe'jacket as describedjan alloy " tension ‘32 divergessuf?ciently from‘ the plane of
headers 281 and 30, for example, for'the circu
lation of boiler '?uid ,therethrough. Each wall
the forward surface-34 to form a similar welding
structure as in the case of outside boundary walls»
Fig. '7 illustrates compositely formed extended‘
recess 62 of at least 90° between the longitudinal '
edge portions 50 and the tube wall. Thus from
its extreme outer edge portion 56 advancing in
wardly toward the tube wall, the cross section of
extension 32 is expanded so that the ?ller ma
terial 45 engages the tube‘ throughout an are
greater than 30°, with a total are of engagement
of at least 45°, and preferably from about 50° to
surface elements particularly adapted for ' the
transfer of heat by convection, a. suitable ‘applica
tion of such elements being in the gas ?ue M as
the tubular heating surface of a unitsuch as a
superheater, reheater or economizer, wherein
heat is transferred from a hot gaseous ?uid ex
ternally of the element to a ?uid, either gaseous‘
60°, for the entire composite extension 32 includ 10 or liquid, within the tubular base member,‘ 84'.
ing the welds along longitudinal edges 48 and 50.
However, in other instances, the direction of heat;
According to Fig. 4, each composite extension
?ow may be reversed as previously explained from
64 presents a planar surface 34 preferably ar
ranged‘ in tangential relation to the exterior wall
of tube 26 as in Fig, 2, the edge portions 48, 50
and 54 of the jacketing member 66 being similarly
arranged and'welded to the tube wall. The rear
ward ‘portion 63 of the jacket, normally the un
heated portion, is formed with one or more bends
or corrugations 10 to provide ?exibility, such cor
rugations being also formed if desired in the por
tion 12 of the jacket on the side adjacent a_simi
lar block on the adjacent tube. The pocket 14
formed between complementary corrugations on
adjacent blocks may be utilized to retain plastic
refractory material for sealing the joint between
adjacent blocks. The heat conducting filler 46
may be one of the several‘ materials heretofore
a hot ?uid within the tubular member 84 to a
cooler ?uid, ‘either gaseous or liquid, externally of V
the element.
Fig, 7 shows tubes 84 spaced apart in a rowto
provide for ?uid ?ow‘therebetween, each tube‘
having its exterior surface'extended by means of: .
composite extensions 86 each comprising a metal
jacket 88 welded to the tube 84 and containing
a suitable heat conducting ?ller 46 in intimate
thermal contact with the tube wall. The jacket
88 is generally V-shaped in cross section and may
be formed as a box in the manner described for
previous embodiments, with the side toward the
tube open, and with longitudinal edges 90 and
other free edges welded to the tube wall. There
may be a plurality of separate extensions 86 along
each tube as shown for extensions 32 in Fig. 3.
sistency being especially suitable because of its 30 The composite extensions 86 are shown attached
ability to yield to whatever form is required by
to each tube in pairs, at diametrically opposed lo
the flexing of the corrugated wall of the jacket 66.
cations, at the upstream and downstream sides,
A plurality‘of extended surface elements such as
although other arrangements of a plurality ofex
shown in Fig. 4 may be associated in a wall struc
tensions may be used as well as a single extension
ture, if desired, with suitable refractory and back 35 circumferentially of each tube.‘ It will be under
ing materials 38 and 40 applied as in Fig. 2.
stood also that the tubes in successive rows may
In Fig. 5,‘each composite extension 18 has a
be in alignment relative to ?uid ?ow thereover, or‘
jacket portion 18 of exterior form similar to the
may be in staggered relation, as desired.
' ‘
jacket 44 of Fig, 2, and similarly welded to the
While in accordance with the provisions of the
tube 26 along edges 48, 50 and 54. In this em 40 statutes I have illustrated and described herein
bodiment, metallic projections 89 are provided
the-best forms of my invention now known to me,
within the jacket 18 and secured either to the tube
those skilled in the art will understand that
26, or to the jacket as shown, to project a sub
changes may be made in the form of the appa-i
stantial distance into the mass of ?ller material
ratus disclosed without departing from the spirit
46 as a means of increasing its heat conducting 45
of the invention covered by my claims, and that
capacity, Such projections 80 in the form of bars
certainfeatures of my invention may sometimes
or rivets, for example, may be conveniently welded
be used to advantage without a corresponding use
described, a material of fluid or semi-?uid con
to a selected area of the jacket 18 when made of
sheet metal before. the jacket is shaped to ?nal
form. The elements of Fig. 5 may also be in
corporated in a wall structure similar to Figs. 2
and 3, as will be understood.
Fig. 6 illustrates an embodiment utilizing com
posite extensions 32 to form a Wall structure hav
of other features.
I- claim:
1. The method of extending the external sur
face-of a tubular element of circular cross section
which comprises, forming relatively thinmetal
into a hollow, box-like jacket having one side open
to extend partially around said element, ?lling
the space within said jacket with molten metal
to provide a molecular bond between said ?ller
metal and the metal of said jacket, suf?cient
example, dividing the combustion chamber A
molten metal being introduced to over?ll the
from the adjacent open gas pass E. Individual
jacket space to an extent providinggan extension
extensions 32 may be the same as described as 60 of the ?ller metalbeyond the edges of the jacket
for Fig. 2, or may be of the form shown in either
surrounding the open side after complete solidi
Fig. 4 or Fig. 5, with a suitable ?ller 46 within
?cation, shaping said ?ller metal extension to a
the jacket 44 as already indicated. With the
surface conforming to the external contour of the
blocks 32 attached to'both faces of the partition
tubular element,‘ clamping the ?lled jacket
wall in this manner, the spaces between oppo 65 against said tube'with the shaped extension sur
sitely arranged series of blocks 32 may be ?lled
face in contact with the conforming tube wall '
with a suitable refractory cement-38 to provide
surface and with the jacket edges spaced there
ing exposed planar surfaces 34 at opposite sides,
suitable for use where heat is applied to both sur
faces as in the case of the partition wall C’, for
a seal against gas leakage from one face of the
wall to the other.
'When the extended surface elements are ar -70
ranged in a row to form a wall, as in Figs. 2 to 6
from, and welding said jacket edges to the tube '
wall to maintain close thermal contact between
the ?ller metal and tube.
I .
~ 7
2. A furnace ‘wall unit comprising a ?uid-con
inclusive, it will be understood that suitable pro
ducting metal tube having means integral vthere
vision may be rnade to maintain them in their
with forming extended heating surface for ex
relative positions, either by tying adjacent tubes
posure toward said furnace, said means compris
together or by tying the tubes to some stationary 75 ing extensions arranged oppositely on said- tube
and 2 providing. heat absorbing. surface substan
‘ tially in a plane tangent to said tube, each exten
sion {being compositely-tformcd to include a .sheet
metal .j ackethavingoppositely disposed uniform
lycthinwalls in diverging relation towardsaid
tube ; and ; terminating in edges. spaced L circum
ferentially adjacentsaid tube through an ;arc _ of
at-leastBO‘f, one oflsaid. walls having an exposed
surfaceportion in saidplane and havingits >ad~=
joining inner edge portion bent to,extend ap
proximatelyradially of saidtube. to form a weld.
‘therewith providing ; extended heat . transfer sur
face; said means. comprising extensions arranged
oppositely onsaidgtub'e, and providingheat trans
fernsurface substantialdy in aplane. tangentv to
said’ tube, each’ extension being compositely
formed to include a sheet metal jacket; having
oppositely; disposed uniformly. thin. wallsin di
verging {relation toward said tube andterminat
ing. in’; edges.‘ spaced :circumferentially. adjacent
ll) saidtube; one. oflsaid wallsilhavingga-n exposed
surfacerportionin said plane _and..havirrg . its ad:
ing. recess below the. plane; of said exposed jacket .
joining: inner ., edge; portion; bent .to; extend . ap
surface,.?ller.materialwithin said j acket-having a
heat ¢ transfer capacity. greater than .the;material
ofsaidjacket, said ?llermaterial having. a..cir-=.
cumferential .dimension of engagement. with said
proximately radially-of, said :tube ,tojorm .a weld
inggreces'sbelowthe planeof saidexposedjacket
-. surface;..?llery material. within. said, jacket having
a; heat; transfer; capacity, greater than; the . ma
terial ;of said jacket, .said .?ller ; material having
a. circumferential dimension of engagement with
saidtube; several. times the thickness. of said
jacket. walls-and an average circumferential di
tube '. several . times the thickness. of : said‘. jacket
walls. and . an average. circumferential dimension
throughout. its radial extent: also greater than
said wall thickness, andmeans for unitingsaid
edgerportions with said tube including weld-metal
fused-within said recess to approximately thetan
_ mension throughout its radial extent also greater
than said. wall thickness-and means for uniting
3;: The method of extendingv the. external sur
said 1edge portionswith said .tubeinclucling weld
metal fused._within said recess. to approximately
faceof atubular elementsofcircular cross. sec
. .the “tangential position‘. of‘ said exposed heat
gential position . of . said. exposed heating surface.
tion which comprises, forming.- relatively; thin
metal ,into a hollow box-like jacket. having one
side... open. to. extend. partially; around.;said._e1e
ment. introducingimctalin asolidstateinto the
6.~ A heattransferunit comprisinga ?uidacon
ducting. metal. .tube havinggneans integral there
with ; providing extended ~j heat . transfer ;_ surface,
-said means comprising an extension .on said tube
spacewithin said jacket, transforming said .metal . -.
into; a .molten mass.- having. fusion engagement .
providing‘. heat transfer. surface substantially, in
a-plane tangent to said tube, said, extension be
ing-,compo-sitely formed .to include a sheet metal
with‘ the Walls of said jacket; effecting solidi?ca
tion of said mass ‘to provide a block of metalcom
pletely ?lling .saidjacket space While maintain
ing‘its metallicbondwith said Walls, said .filler
block providingan exposed‘ surface displaced out
wardly from the surrounding edges of said jack
jacket havinggoppositely disposed uniformly‘ thin
walls-in .divergingrelation toward said, tube and
terminating inedgesspaced circumferentially ad
jacent said'tube, one of saidwalls having“ an
exposed‘surface portion in said, plane ‘and hav
et,‘~ shaping ‘theexposedsurface'of saidfillerblock
of the tubular element, , assembling the ?lled
ingqits adjoining inner ‘edge portion bent to ex
tend approximately radially vof said tube to form
jacket adjacent said tube with said shaped sur
face‘incontact ‘throughout with the adlQining
tube wall surface and with __said__jacket. edges
spaced therefrom. and welding said jacket-edges
jacket surface, filler material within said jacket
having a heat transfer capacity, greater than the
material ofsaid jacket, said l?llerlmateriahhav
to the tube Wall to maintain. close thermal con
tact between the filler metal and tube.
4. The method ‘of extendingtheexternal sur
‘ with said tube several times the-thickness of said
face of a tubular element which com-prises,.f0rm
ing relativelymthin sheet metal of ferrous compo
mension throughoutitsradial extent also greater
than said wall thickness, andlmeans for uniting
‘said edge portions with saidtube including weld
to. a surface conforming to the external contour
a welding recess below the plane ofsaid exposed
inga circumferential dimension of engagement
jacketswalls and an. average circumferential di
sition into a box-likejacket having its walls ar- '
adapted to embrace an arcuate area of saidtu
metal fused Within .said recess to approximately
the tangential position of said expcsedheat trans
bularelement, the space within said jacket being
fer surface.
ranged tode?nean openingin a side thereof
'7. A heat transfer unit comprising a ?uid-con
of minimum cross section, at a. location farthest
from said opening‘ and of progressivelylgreater -' ‘ ductingtmetal tube having means integral there
with providing extended heat transfer surface,
cross section toward its maximum cross section
said means comprising extensions arranged oppo
adjacent said opening, effecting solidi?cation of
sitely on said tubeand each providing heat trans
molten metal ,within- said jacket to form a metal
?ller having a substantially continuous metallic
juncture with the walls of. said jacket and pro
viding; an exposed surface beyond. the surround
fer surface substantially in a plane tangent to
said tube,‘ each extension. being compositely
formed to include asheet metal jacket having
oppositely disposed uniformly thin walls in di
ing jacket edges, said ?ller metal having a heat
verging relation toward. said tube and terminat
conductivity of the order of copper and thereby
greater than the heat conductivitylof thejacket
metal, shaping said exposed surface to a- surface
ing in edges spaced circumferentially adjacent
conforming to the contour of said arcuate area,
surface portion in said plane and having its ad
joining inner edge portion bent toextend ap
proximately radially of said tube to form a weld
ing recess below theplaneof said exposed jacket
surface,-.?ller.material .within said. jacket having
said tube, one ofsaidwalls having an exposed
positioning said. jacket adjacent said tubular
element * with said shaped surface in contact
throughout ‘with said arcuate area and with said
jacket edgesspaced therefrom, and welding; said‘
jacket edges to said tubular member to main
5, heat transfer capacitygreater than the ma
tain said metal ?ller in close thermal engagement
terial of-said jacket, said. ?ller. material having
with said member.
5. A heat transfer wall unit comprising a ?uid
a circumferential dimension of engagement with
said tube several times the thickness of said
conducting metal tube having means integral
jacket walls and an average circumferential di
ine‘ns'i'on throughout its radial extent also’ greater
gential position of said exposed heat transfer sur
than said wall thickness, and means for uniting
said edge portions with said tube including weld
10. A heat transfer wall unit‘ comprising a?uid
conducting metal tube having an extension there
on providing heat transfer surface substantially
in a plane tangent to said tube, said extension
metal fused within said recess to approximately
the tangential position of ‘said exposed heat trans
fer surface.
8. A furnace wall unit comprising a ?uid-con
ducting metal tube having an extension thereon
comprising a sheet metal jacket formed as a box
having one side open and having edges surround
ing said open side secured to said tube to de?ne
10 a closed compartment adjacent said tube, said
providing extended heat transfer surface substan
tially in a plane tangent to said tube at the fur
jacket having oppositely disposed uniformly'thin
nace side thereof, said extension comprising a
side walls extending in diverging ‘relationtoward
said tube and terminating ‘in circumferentially
‘side secured to said tube to de?ne a closed com
spaced edges adjacent said tube, one of said side
partment adjacent said tube, the enclosing walls 15" walls having an exposed surface portion'i'n said
of said compartment thereby including the por
plane-and having its'adjoim‘ng inner edge'portion
tion of said tube‘ embraced‘ by said jacket, said
bent' to extend approximately radially of said
jacket having oppositely disposed uniformly thin
tube to form a welding recess below the plane of
side walls extending in diverging relation toward
said exposed jacket surface, the other of- said
said tube and terminating in circumferentially 20 walls having corrugations therein‘ throughout its
spaced edges adjacent said tube, one of said side
thickness, a heat conducting medium fluid at op- '
-» walls having an exposed surface portion in said
erating temperatures substantially ?lling said
plane and having its adjoining inner edge por
compartment, said heat conducting medium hav
tion bent to extend approximately radially of said
ing a circumferential dimension of engagement
sheet'metal jacket formed'as a box having one "
side open and having edges surrounding said open
tube to form a welding recess below the plane 25 with said tube several times the thickness of said ’
of said exposed jacket surface, a heat conducting
diverging side walls and an average circumferen
medium ?uid at operating temperatures substan
tial dimension throughout its radial extent corre
tially ?lling said'compartment, and heat conduct
ing projections extending into said medium from
one of said compartment enclosing walls and ter
spondingly greater than said side wall thickness,
and means for uniting said edge portion with ‘said
minating in spaced relation with respect to all
other said Walls, said heat conducting medium
tube including weld metalfuse'd‘within said recess
to approximately the tangential position of said
exposed heat transfer surface.
having a circumferential dimension of engage
11. In a furnace wall adapted for exposure to
ment with said tube several times the thickness
heating gas zones of different pressures atoppo
of said ‘diverging side walls and an average cir 35 ‘site sides, a row of spaced elongated heat transfer
* cumferential dimension throughout its radial ex
tent correspondingly greater than said side wall
thickness, and means for uniting said edge por
tion with said tube including weld metal fused
within said recess to approximately the tangen
tial position of said exposed heat transfer sur
units each comprising a metal tube of curvilinear
cross section for conducting ?uid to be heated,
and means for extending the exterior surfaces of
said tubes to provide substantially continuous
heat absorbing surfaces in planes substantially
tangent to said tubes at opposite sides of said row,
said means at each side comprising metal jackets
9. A heat transfer wall unitcomprising a ?uid
secured in pairs to each of said tubes and a heat
conducting metal tube having an extension there
conducting material substantially ?lling said
on providing heat transfer surface substantially 45 ‘jackets, said jackets each having uniformly thin
in a plane tangent to said tube, said extension
side Walls extending in diverging relation toward
comprising a sheet metal jacket formed as a box
one of said tubes and terminating in circumfer
having one side open and having edges surround
entially spaced edges adjacent said tube, said
ing said open side secured to said tube to de?ne
jackets having certain of said side walls in said
a closed compartment adjacent said tube, and a 50 "tangent planes for substantially bridging the
heat conducting medium ?uid at operating tem
spaces between adjacent tubes while the remain
peratures substantially ?lling said compartment,
said jacket having oppositely disposed uniformly
ing side walls diverging therefrom de?ne substan
tially closed intertube spaces intermediate said
thin side walls extending in diverging relation to
ward said tube and terminating in circumferen
tially spaced edges adjacent said tube, one of said
side walls having an exposed surface portion in
said plane and having its adjoining inner edge
planes, one of said walls of each jacket having an
exposed surface portion in one of said planes and
portion bent to extend approximately radially of
said tube to form a welding recess below the plane 60
of said exposed jacket surface, said side wall be
ing formed with projections thereon extending
having its adjoining inneredge'portion bent to
extend approximately radially of said tube to
form a welding recess below the plane of said ex
posed jacket surface, means for uniting said edge
portions with said tubes including weld metal
fused within said recesses to approximately the
tangential positions of said exposed heat absorb
into said medium partially across the space to
ing surfaces, and refractory material ?lling said
ward the opposite of said walls, said heat con
intertube spaces for sealing said wall against gas
ducting medium having a circumferential dimen 65 leakage from one of said zones to the other, said
sion of engagement with said tube several times
heat conducting material having a circumferen
the thickness of said diverging side walls and an
‘ tial dimension of engagement with each tube sev
average circumferential dimension throughout its
eral times the thickness of said side walls and an
radial extent correspondingly greater than said
average circumferential dimension throughout its
side wall thickness, and means for uniting said 70 radial extent correspondingly greater than said
edge portion with said tube including weld metal
side wall thickness.
fused within said recess to approximately the tan
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