United States Patent (19) (11) 4,236,578

Kreith et al. ". 45) Dec. 2, 1980

(54) HEAT EXCHANGE ENHANCEMENT 3,333,317 8/1967 Shockley ........................ 29/157.3 A
STRUCTURE FOREIGN PATENT DOCUMENTS
(75) Inventors: Frank Kreith, Boulder, Colo.; 843236 8/1960 United Kingdom ..................... 165/184
Richard C. Cornelison, Hiram, Ohio 188998 11/1966 U.S.S.R. ................................... 165/183
(73 Assignee: Condar, Co., Hiram, Ohio Primary Examiner-Samuel Scott
(21) Appl. No.: 902,848 Assistant Examiner-Theophil W. Streule, Jr.
Attorney, Agent, or Firm-Fay & Sharpe
(22) Filed: May 4, 1978
(51) Int, C. ................................................ F28F 1/20 57 ABSTRACT
(52) U.S. C. ................................... 165/181; 29/157.3; A passive heat exchange enhancement structure which
113/118 A; 165/185 operates by free convection includes a flat mounting
(58 Field of Search .................. 403/304,344; 165/77, portion having a plurality of integral fins bent out
165/181-184, 55; 29/157.3 AH, 313; 113/118 wardly from one side edge thereof. The mounting por
A, 118 B tion is securable around a stovepipe, to a flat surface or
56) References Cited the like for transferring heat from the pipe through the
U.S. PATENT DOCUMENTS fins to the surrounding air by rotation-enhanced free
convection.
1,932,610 10/1932 Tilley ........ ... 165/184
2,400,737 5/1946 Brown, Jr. .... ... 165/182
2,625,804 1/1953 Patch et al. ........................ 165/77 X 14 Claims, 12 Drawing Figures
U.S. Patent Dec. 2, 1980 Sheet 1 of 3 4,236,578

FIG.
U.S. Patent Dec. 2, 1980 Sheet 3 of 3 4,236,578
 4,236,578 2
1.
fins both longitudinally and transversely to the mount
HEAT EXCHANGE ENHANCEMENT STRUCTURE ing portion.
The mounting portion has opposite ends and integral
BACKGROUND OF THE INVENTION mounting means formed on the mounting portion in
wardly from its opposite ends. The mounting means
This application relates to the art of heat exchange 5 may include bosses formed outwardly of the mounting
enhancement structures and, more particularly, to portion in the same general direction in which the fins
finned heat exchange enhancement structures which
operate by free convection using fins having a large extend outwardly
therefrom. The bosses have openings facing
opposite from the ends of the mounting por
surface area for transferring heat and making contact 10 tion. End coils on a coil spring may be received directly
with a quiescent fluid. through the openings for location beneath the bosses for
The heat exchange enhancement structure of the
present application is particularly applicable for use in providing a very quick mounting for the heat exchange
transferring heat from a hot stovepipe, fluepipe or the enhancement structure on a stovepipe, fluepipe or the
like by rotation-enhanced free convection to the quies like. The spring places the mounting portion in tension
cent air of a room in which the stovepipe is located. 15 so it firmly engages the pipe around which it is
However, it will be appreciated by those skilled in the mounted. The end coils of the coil spring may be re
art that the improved heat exchange enhancement ceived through openings in hook brackets which are
structure has broader aspects and may be used for trans hooked to the bosses.
ferring heat in other environments. Elongated stiffening ribs are formed in the mounting
It is known to be advantageous to utilize heat energy 20 portion along opposite sides of the bosses forming the
from hot gases passing through a stovepipe or the like to mounting means. These stiffening ribs extend outwardly
assist in heating a room or other associated space. How from the mounting portion in the same direction as the
ever, such energy is ordinarily substantially lost to the bosses and inhibit creasing or undesirable deformation
atmosphere and performs very little in the way of any of the mounting portion in the area of the bosses.
useful heating function during the passage of the hot 25 An optional variation includes a plurality of equidis
gases through the pipe. If heat could be more efficiently tantly-spaced screw receiving holes formed along the
communicated from the pipe to the space which is to be length of the mounting portion for receiving screws
heated, the associated stove or furnace would be more which extend well into a stovepipe, fluepipe, flat sur
energy efficient. This result is deemed to be particularly 30 face or the like. These screws firmly hold the mounting
advantageous and significant due to the fact that the portion in contact with the stovepipe or other surface to
availability of some types of fuels is decreasing while provide good heat conduction. The screws themselves
the costs therefor are ever increasing. are in contact with the hot gases flowing through the
BRIEF DESCRIPTION OF THE INVENTION stovepipe and transfer heat to the heat exchange en
In accordance with the present new development, 35 hancement
into the
structure for outward dissipation by the fins
surrounding air of a room. The screws are
there is provided a free convection type heat exchange preferably of a high heat transfer material such as steel
enhancement structure operable by rotation-enhanced or aluminum.
free convection. The heat exchange enhancement struc In one arrangement, the fins are bent to extend at an
ture includes an elongated flat mounting portion having included
opposite side edges. A plurality offins integral with the of betweenangle
40
60'
with the plane of the mounting portion
and 85. More specifically, the fins pref.
mounting portion extend outwardly from at least one of erably extend at an included
said side edges thereof. The fins are bent adjacent the with the mounting portion angle after
of between 70 to 85
being bent through
one side edge to extend transversely to the plane of the combined angles of approximately 95 to 110'. With this
mounting portion.
In one arrangement, the heat exchange enhancement mounting portion outwardly thereof awhen
45 arrangement, the fins overlay at least portion of the
the heat
structure is made of sheet aluminum which is covered
with a black coating to render it a very good infrared pipe. exchange enhancement structure is installed on a stove
emitter. The aluminum sheet is obtained in a coil and is ,
then uncoiled to present a flat sheet on which cutting straight The fins are preferably bent along a plurality of
and forming operations are performed. 50 lines in order to provide them with the desired
The fins of the heat exchange enhancement structure to form theshape.
twist and
fins
This arrangement makes it much easier
and no compound bends are necessary.
preferably have a substantially uniform width along At least one of the straight line bends is effective to turn
their entire length. the fins about their axes at an angle less than 90 so that
The plurality of adjacent fins which extend from a the projection areas of the opposite faces of the fins
predetermined longitudinal length of the one side edge 55 toward the opposite side edges of the mounting portions
on the mounting portion have a combined width which
is substantially equal to the predetermined longitudinal are less than the actual width of the fins.
length of the one side edge. With this arrangment, there from The heat exchange enhancement structure is made
is little or no waste of material in making the improved from a substantially rectangular metal sheet unwound
a coil. The sheet is worked by forming a plurality
heat exchange enhancement structure from a flat sheet 60 of equidistantly-spaced
of metal which is uncoiled from a coil. parallel cuts, slits or lances in
The fins have opposite fin edges and are twisted or the sheet extending from one longitudinal edge thereof
turned about their longitudinal axes so as to locate one toward the other and terminating short of the other to
fin edge facing outwardly in the same general direction define the mounting portion. Each slit extends at an
as the one side edge of the mounting portion and to 65 angle to the mounting portion of preferably between
locate the other fin edge facing outwardly in the same 45 to 70°. Each fin has a fin span or base along the one
general direction as the other side edge of the mounting side edge of the mounting portion and has an acute fin
portion. This arrangement exposes the flat faces of the edge intersecting the one side edge of the mounting
 3
4,236,578
4.
portion at an acute angle. Each fin includes an opposite It is a further object of the development to provide an
obtuse fin edge intersecting the one side edge of the improved method of manufacturing a finned heat ex
mounting portion at an obtuse angle. Each fin is bent change enhancement structure.
along a first bend line extending generally from the Still further objects and advantages for the subject
intersection of the acute fin edge with the span or base new development will become apparent to those skilled
to an intersection point with the obtuse fin edge spaced in the art upon a reading and understanding of the speci
outwardly from the span. Each fin is bent along a sec fication.
ond bend line defined by the span and also preferably BRIEF DESCRIPTION OF THE DRAWING
bent along the first bend line to position the fin edges O
substantially perpendicular to the span or to the one side The invention may take form in certain parts and
edge of the mounting portior, as viewed in plan view. arrangements of parts, a preferred embodiment of
The intersection point between the first bend line and which will be described in detail in this specification
the obtuse fin edge is located generally toward the and illustrated in the accompanying drawings which
midpoint area of the span or base of each fin outwardly 15
form a part hereof and wherein:
along the obtuse fin edge. The fins are bent about the FIG. 1 is a perspective illustration of a stove pipe
second bend lines through an angle of approximately having the improved heat exchange enhancement struc
55° to 85. ture of the present application installed thereon;
In its installed form on a stovepipe or the like, the FIG. 2 is a partial plan view of a flat metal sheet
heat exchange enhancement structure has a substan 20 having cuts formed therein in an intermediate stage of
tially flat cylindrical mounting portion with opposite manufacturing the improved heat enhancement struc
circular edges and a longitudinal axis. A plurality of fins ture;
are integrally formed with the mounting portion and are FIG. 3 is an enlarged partial plan view showing the
bent outwardly from at least one of the circular edges. portion of the sheet in FIG. 2 after fins have been bent
The fins are bent to have opposite fin edges lying gener 25 in successive stages;
ally on the surfaces of cones having axes coincidental FIG. 4 is an end elevational view taken generally
with and spaced along the longitudinal axis of the along lines 4-4 of FIG. 3;
mounting portion. The structure is mounted on a gener FIG. 5 is a plan view of a completed heat exchange
ally vertically disposed cylindrical pipe such as a stove enhancement structure;
pipe, fluepipe or the like with the apices of the cones 30 FIG. 6 is a partial cross-sectional elevational view
pointing upwardly. The cones preferably slope up taken generally along lines 6-6 of FIG. 5;
wardly from their bases toward their apices at an angle FIG. 7 is a cross-sectional elevational view taken
of approximately between 5' and 30' from a horizontal generally along lines 7-7 of FIG. 6;
plane passing through the generally vertical pipe. FIG. 8 is a partial edge elevational view taken gener
In its installed position on any surface, the heat ex 35 ally on lines 8-8 of FIG. 5;
change enhancement structure has a substantially flat FIG. 9 is an edge elevational view showing one
mounting portion with a plurality of integral fins bent means for joining the opposite ends of the heat ex
outwardly from at least one of the edges on the mount change enhancement structure together;
ing portion. The fins are turned about their axes so the FIG. 10 is a plan view taken generally along lines
projection area of one face of the fins generally out 40 10-10 of FIG. 9;
wardly of one edge is generally the same as the projec FIG. 11 is an elevational view of a heat exchange
tion area of the opposite face of the fins generally out enhancement structure showing the relationship of the
wardly of the other edge. The fins are turned or twisted fin edges to a pair of cones and the longitudinal axis of
about their longitudinal axes approximately 45 to 70° in the cylindrical mounting portion on the heat exchange
order to accomplish this desirable arrangement which 45 enhancement structure; and,
induces maximum air flow between and over the fins. FIG. 12 is a partial view similar to FIG. 9 and show
Hot air swirls outwardly between the fins so cold air is ing a modified arrangement for joining together the
induced to flow in toward the stovepipe, fluepipe, flat opposite ends of the heat exchange enhancement struc
ture.
surface or the like as well as toward the heat exchange 50
enhancement structure. DESCRIPTION OF A PREFERRED
It is a principal object of the present development to EMBODIMENT
provide an improved finned heat exchange enhance Referring now to the drawings wherein the showings
ment structure which operates by free convection, and are for purposes of illustrating the preferred embodi
provides an improved free convection air flow pattern 55 ment of the invention only and not for purposes of
which swirls hot air into the surroundings, induces limiting same, FIG. 1 shows a heat exchange enhance
colder air from the surroundings and thereby increases ment structure A constructed in accordance with the
heat transfer performance from a pipe or other surface present application installed on a generally vertically
containing or associated with a heated fluid. disposed cylindrical stovepipe, fluepipe or the like B
It is also an object of the development to provide an 60 which would normally be connected to a wood burning
improved finned heat exchange enhancement structure stove or any other apparatus producing heat and hot
which is very simple to manufacture and install. gases which are exhausted through pipe B. As shown in
. It is an additional object of the development to pro FIG. 1, the hot gases flow in the direction of arrows a.
vide an improved finned heat exchange enhancement Although shown and hereinafter described with refer
structure which maximizes free convection air flow 65 ence to a cylindrical stovepipe or the like, it will be
between and over the fins while also maximizing heat appreciated that the concepts of the subject develop
transfer by radiation from the fins to the surroundings ment are equally applicable to use with other types and
which may include people, walls and the like. styles of surfaces.
 4,236,578 6
5.
Heat exchange enhancement structure A includes a Fins D have fin spans or bases 30 defined along line 22
flat mounting portion Chaving a plurality of integral between each adjacent pair of holes 28 or between the
fins D bent outwardly from one edge thereof. Mounting inner terminal ends of cuts 20 along the one side edge of
portion Chas a generally cylindrical configuration with mounting portion C.
a longitudinal axis coincidental with longitudinal axis 12 5 Although the length of spans 30 may vary, it has been
of cylindrical pipe B. Fins D are circumferentially found desirable to space cuts 20 so that the bases or
spaced and extend outwardly from mounting portion C spans are approximately equal to 0.410" or 0.440". This
for transferring heat to a room in which pipe B is lo arrangement allows for the accommodation of the num
cated. In the preferred arrangement, heat exchange ber of fins required to surround the pipe with substan
enhancement structure A is constructed of sheet alumi O tially the same spacing between the fins at each end of
num which is painted or otherwise coated with a black mounting portion C as is found between all the other
coating, although other materials and arrangements fins when the heat exchange enhancement structure is
could be advantageously employed without in any way installed and does not require any change or variation in
departing from the overall intent or scope of the present the span length to properly accommodate the most
development. The aluminum sheet is unwound from a 15 common stovepipe or fluepipe diameters of 6', 8' and
coil of sheet aluminum during the manufacturing proce 10'. Merely by way of example, and when spans 30 are
dure. Hot gases inside the pipe transfer heat by convec 0.410' in length, the heat exchange enhancement struc
tion and radiation to the interior surfaces of the pipe, ture will have forty-six (46) fins when used on a 6'
thence through the pipe to the enhancement structure diameter pipe, sixty-one (61) fins when used on an 8'
mounting portion and fins. Heat is finally transferred to 20 diameter pipe and seventy-seven (77) fins when used on
the air by convection and to people, objects and walls in a 10" diameter pipe to achieve the above noted ulti
the room by radiation. Heat exchange enhancement mately desired spacing between the end fins. Thus, it is
structure A is a very good emitter of infrared radiation not necessary to adjust or have separate dies for manu
and a plurality of series of heat exchange enhancement facturing the subject heat exchange enhancement struc
structures are preferably used and mounted similar to 25 ture for adoption to use with at least the most com
the one heat exchange enhancement structure shown in monly
FIG. 1 at longitudinally-spaced apart locations or inter the likeused of the conventional stovepipe, fluepipe and
vals along a vertical length of pipe B. When so installed, the preferred span Moreover,
diameters. and in conjunction with
lengths, these lengths are such that
each enhancement structure is preferably positioned intimate heat transfer contact between the pipe and
along the pipe relative to the next adjacent enhance 30 enhancement structure is substantially maintained at the
ment structure in a manner such that the mounting span areas. It is, however, possible to vary the afore
portions are closely adjacent each other or are spaced
apart from each other up to a distance which is gener mentionedway
dimensional characteristics without in any
departing from the overall intent or scope of the
ally equal to the length offins D. Therefore, hot, buoy subject development.
ant air swirls upwardly and outwardly between fins D 35 Fins D are bent along straight first bend lines 34
on the lower positioned heat exchange enhancement which extend at an angle 36 in the range of 50 to 80 to
structure A. This induces the flow of cooler air toward
the heat exchange enhancement structures by free con consideredline 22 or a span 30. An acute edge of each fin D may be
vection. Moreover, it may also be desirable from a heat cluded acutetheangle. edge which intersects line 22 at an in
The opposite edge of each fin may
transfer point of view to mount the enhancement struc be considered as intersecting side edge 22 of mounting
tures A in a manner such that the fins of each structure
portion C at an obtuse included angle. The included
are offset relative to the fins of the next adjacent struc acute
ture by up to one half pitch. While the description ap and obtuse angles are supplementary to each
pearing hereinafter relates to a single heat exchange other. Thus, one edge of each fin D may be considered
enhancement structure A, it will be appreciated that the 45 as an acute fin edge 42, while the opposite parallel fin
edge may be considered as an obtuse fin edge 44. Each
others in the series are substantially identical thereto.
FIG. 2 shows a flat metal strip having opposite paral bend line 34 extends from the intersection of the acute
lel longitudinal edges 14,16 and a longitudinal axis 18. A fin edge with a span 30 toward the obtuse fin edge to
plurality of equidistantly-spaced parallel cuts, slits or intersect
wardly
same at an intersecting point 40 spaced out
from span 30. In the particular arrangement
lances 20 are formed in the strip extending from longitu shown in the FIGURES,
50
angles 26,36 are equal to each
dinal edge 14 toward longitudinal edge 16 and terminat
ing short thereof generally along a line 22 extending other so that each intersecting point 40 also bisects a
parallel to longitudinal edge 16. That portion of the span 30. In other words, an isosceles triangular area 48
metal strip between edge 16 and line 22, which is sub is defined by span 30, line 34 and that portion of a cut 20
stantially smaller then the portion between line 22 and 55 between intersection point 40 and a hole 28. However,
edge 14, defines a mounting portion C. Line 22 repre it is not necessary to have angles 26.36 equal to each
sents one ultimate side edge of mounting portion C and other within the preferred ranges therefor as set forth
longitudinal edge 16 of the metal strip defines the other above. In the event they are not equal, intersecting
side edge. point 40 would then only fall generally toward the
In a preferred arrangement, cuts 20 extend at an in 60 midpoint area of the associated span 30.
cluded angle 26 with longitudinal axis 18. This angle The left side of FIG. 3 shows a fin D after it has been
may vary between 30 and 80 and most preferably will bent along first bend line 34 to a position in which acute
generally be in the range of 45° and 70. In the arrange fin edge 42 and opposite obtuse fin edge 44 extend sub
ment shown, each terminal end of a cut 20 at line 22 is stantially perpendicular to side edge 22 of mounting
provided with a small circular hole 28 for ease in de 65 portion C as viewed in plan view. Depending upon the
forming the metal in a manner to be described. Fins D particular angle selected from within the preferred
have a uniform width along their entire length and are range set forth above for angle 36, the fin will be bent
defined between each adjacent pair of parallel cuts 20. along bend line 34 at an angle generally in the range of
 7
4,236,578
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45°-75° relative to the plane of triangular area 48 in in a close fitting relationship with pipe B to enhance the
order that the fin will assume this particular position. heat transfer characteristics therebetween. However,
Subsequent to the bending of each fin D along first and if desired, it is possible to dispense with using the
bend lines 34, they are then bent about spans 30 through hole 64 and screw arrangement.
an angle of approximately 55-85 to assume a final Separate mounting means is also formed integrally
position as shown at the right side of FIG. 3. In FIG. 4, with mounting portion C for mounting same in a cylin
the left-most fin is in the final position, and the right drical configuration around pipe B of FIG. 1. This
most fin is in the intermediate position after bending mounting means is in the form of bosses 68 formed
only along first bend line 34 of FIGS. 2 and 3, Triangu outwardly of mounting portion C in the same general
lar areas 48 remain adjacent spans 30 as best shown in 10 direction in which the fins extend outwardly from
FIG. 3 after complete bending of the fins. mounting portion C. Bosses 68 are spaced inwardly
The final bending of each fin leaves acute fin edge 42 from opposite ends 60,62 and as best shown in FIG. 6,
spaced from mounting portion C at an included angle 50 have openings 70 which face in a direction opposite
of between 60-85. Triangular area 48 lies in plane 52 from the most adjacent end 60 or 62. For example, boss
intersecting a line 54 perpendicular to mounting portion 15 68 adjacent end 60 has an opening 70 which faces
edge 22 at an angle 56 generally in the range of 5'-35. toward end 62 and boss 68 adjacent end 62 has an open
Preferably, each fin is bent through combined angles so ing 70 which faces toward end 60. As shown in FIG. 5,
that angle 50 is between approximately 70' and 85. three bosses 68 are spaced along mounting portion C.
Bending of each fin D along first bend line 34 to The middle one of these bosses is spaced more closely to
locate the fin edges substantially perpendicular to 20 end 60 and has its opening facing toward end 62. This
mounting portion C in the manner described above has boss is employed as an alternate mounting boss for less
the affect of turning or twisting each fin about its longi common pipe diameters of, for example, 5'', 7' and 9'.
tudinal axis. Each fin remains planar so that there is no When used, that material of the enhancement structure
curving of the metal and the bend is carried out in a located between the middle boss and end 60 as viewed
manner such that the projected areas of the flat faces of 25 in FIG. 5 is simply cut off and discarded. This then has
each fin parallel to axis 12 is reduced. Also, the opposite the advantage of allowing a relatively few basic sizes of
flat faces of each fin D face both longitudinally and mounting portions C to be readily adapted to fit all
transversely of mounting portion C. Although each fin common, standard pipe sizes.
may be turned or twisted about its longitudinal axis to Small elongated stiffening ribs 74 are also deformed
differing degrees by varying angle 36 within the 50-80 30 outwardly from mounting portion C on opposite sides
set forth above and then adjusting the angle of bend of bosses 68. Ribs 74 extend only generally along bosses
about bend line 34 within the 45-75 range as also set 68 and not along the entire length of mounting portion
forth above in order that the fin edges will be located C. Ribs 74 stiffen mounting portion C in the area of
substantially perpendicular to mounting portion C, the bosses 68 to prevent wrinkling or undesirable deforma
preferred degree or angle of twist is approximately in 35 tion of the mounting portion when a mounting device is
the range of 60-65". This preferred range takes into full attached to bosses 68. With this construction, the rear
account the optimum convection heat transfer fin twist side of mounting portion C which is visible in FIG. 5 is
angle of 45-70 for inducing the maximum air flow and completely flat for positioning against pipe B of FIG. 1
transferring maximum heat by means of convection to and obtaining a good heat transfer relationship.
the air flow on either side of the fins. 40 FIGS. 9 and 10 show a coil spring E which is in
In the finished heat exchanger, the projected area of tension and has opposite end coils 80 and 82 positioned
the fin flat faces which face toward side edge 22 is beneath bosses 68 by extending through the outwardly
approximately the same as the projected flat face area facing openings 70 therein. Coil spring E is tensioned so
which faces generally outwardly of side edge 16. In that it urges opposite ends 60,62 toward one another
addition, the ratio of the projected area of the fins to the 45 thereby placing mounting portion C under tension
total projected area of the fins and spaces therebetween around pipe B. Coil spring E in the form of an adjust
for the particular angular ranges set forth above has able tensioning mounting device can take other forms if
been found to optimize heat transfer and air flow be so desired.
tween the fins. Of all the various angular range relation FIG. 11 shows the heat exchanger enhancement
ships specified above for the subject heat exchange 50 structure configuration when it is positioned around a
enhancement structure, the most important ones from cylindrical pipe such as a stovepipe, fluepipe or the like.
an advantageous operational point of view are cut angle Mounting portion C is shaped to a substantially cylin
26, the fin twist angle as defined by angle 36 about bend drical configuration having a longitudinal axis corre
line 34 and the fin downward bend angle about span 30. sponding to axis 12 for pipe B of FIG. 1. The opposite
The other angles are primarily construction angles 55 side edges 16,22 of the mounting portion may also be
which allow for practical and easy manufacture of the considered opposite circular edges when it is in its cy
overall structure by conventional metal working tech lindrical configuration. Fins D are integral with mount
niques such as, for example, in a progressive type die. ing portion C and bent outwardly therefrom about one
FIG. 5 shows a mounting portion C which has been circular edge 22 in the manner previously described.
cut to a predetermined longitudinal length between 60 With this arrangement, opposite fin edges 42 and 44 lie
opposite ends 60,62. A plurality of longitudinally on the surfaces of axially-spaced cones 92,94 having
spaced screw receiving holes 64 are formed through apices 96.98 coincidental with longitudinal axis 12. Due
mounting portion C generally centrally thereof. This to the twisting of the fins about their longitudinal axes,
feature allows a plurality of elongated heat conductive cones 92,94 are axially spaced from each other along
screws to be inserted through the mounting portion and 65 longitudinal axis 12 a distance less than the actual face
into pipe B for enhancing the heat transfer characteris width of the fins. Cones 92,94 slope upwardly toward
tics from the heated gases to the heat exchanger device. their apices 96.98 from their bases at angles generally in
These screws also aid in retaining mounting portion C the range of 5-30 and more preferably in the range of
 4,236,578
9 10
5-20. Here also, heat conductive screws are employed ferred embodiment which transfers heat by rotation
to affix the heat exchanger to pipe B as discussed enhanced free convection. Obviously, modifications
hereinabove. One such screw 100 is shown in FIG. 11 and alterations will occur to others upon the reading
passing through an associated hole 64 in mounting and understanding of this specification. It is intended to
portion C and penetrating pipe B. A plurality of similar include all such modifications and alterations insofar as
screws are spaced peripherally around and similarly they come within the scope of the appended claims or
penetrate the pipe. In the mounted position, good heat the equivalents thereof.
transfer results are obtained by conduction alone be Having thus described the development, it is now
tween the outside surface of the stovepipe and the claimed:
inside surface of mounting portion C. In addition, some 10 1. A free convection type heat exchange enhance
portion of the heat transfer between the two surfaces ment structure comprising: an elongated flat mounting
may also take place by radiation. portion having opposite side edges; a plurality of fins
The arrangement shown and described for making integral with said mounting portion and extending out
heat exchange enhancement structure A results in little wardly from at least one of said side edges thereof; each
or no waste of material. For a given predetermined 15 said fin having a longitudinal fin axis, opposite fin faces,
longitudinal length of side edge 22 on mounting portion opposite fin edges and a substantially uniform width
C, a plurality of fins D occupying that predetermined along its length; each said fin adjacent said one side
longitudinal length have an actual total fin width which edge of said mounting portion having a plurality of
is the same as the predetermined longitudinal length. straight line bends therein about which each said fin is
This is because the fins are formed by cutting, slitting or 20 positioned extending transversely of the plane of said
lancing and then bending so that no material is removed mounting portion and turned about said axis through an
and wasted during manufacture. This also results in angle substantially less than 90 for positioning said flat
optimum area for heat transfer along with optimum faces with the projected area thereof toward said oppo
spacing between fins for enhanced air flow. site side edges of said mounting portion being substan
The ultimate position of each fin D is preferably as 25 tially greater than the thickness of each said fin but
shown in FIG. 11. Due to the preferred upward slope of substantially less than the width of each said fin; each
cones 92,94, fins D will, to some extent, overlay mount said fin, prior to bending thereof about said plurality of
ing portion C outwardly thereof to receive heat there straight line bends, having said fin edges thereof in
from. However, it will be recognized that a number of clined substantially out of perpendicular relationship to
modifications are possible. For example, and with refer 30 said one side edge of said mounting portion; and, each
ence to FIG.4, instead of bending each fin D from the said fin being bent about each said bend in the same
right position shown to the left position shown, it is direction with respect to said mounting portion.
possible to bend each fin so that it extends to the right of 2. The heat exchange enhancement structure as de
line 54 at the preferred angle. In such an arrangement, fined in claim 1 wherein said mounting portion has
heat exchange enhancement structure A would be in 35 opposite ends and includes integral mounting means
stalled in an inverted position with fin D still extending spaced inwardly from said ends, said mounting portion
downwardly but spaced outwardly from the pipe itself being curved to a generally cylindrical configuration
and with mounting portion C above the fins instead of for positioning around a cylindrical pipe, and adjustable
beneath them. The preferred arrangement, however, is tensioning means cooperating with said mounting
that the fins extend downwardly from the upper circu 40 means for tensioning said mounting portion around a
lar edge of the mounting portion. In the final installed plpe.
position of the heat exchanger, the lower edges of the 3. The heat exchange enhancement structure as de
fins make an included angle with the pipe of approxi fined in claim 1 wherein said mounting portion has
mately 60-85. m opposite ends and including integral mounting bosses
FIG. 12 shows an example of another mounting ar 45 formed outwardly of said mounting portion in the same
rangement. Hook bracket 112 has an opening 116 re general direction in which said fins extend from said
ceiving end portion 82 of coil spring E, and a hook 114 mounting portion, each said boss having an opening
is positioned beneath boss 68. A corresponding hook facing outwardly in a direction opposite from the end
bracket on the other end of spring E is similarly at adjacent which it is located, and said bosses being en
tached to the other end portion of the heat exchange 50 gageable by tensioning means for tensioning said
enhancement structure. mounting portion in a curved position around a pipe.
The heat exchange enhancement structure can also be 4. The heat exchange enhancement structure as de
secured to pipes and other structures by other mounting fined in claim 3 including elongated stiffening ribs in
arrangements than those disclosed. For example, the said mounting portion extending at least along opposite
heat exchange enhancement structure could be welded 55 sides of said bosses substantially parallel to said opposite
to a pipe or other structure or could be placed thereon edges of said mounting portion, and said ribs being
in a continuous spiral. The heat exchange enhancement formed outwardly from said mounting portion in the
structure could also be secured directly to barrel stoves same direction as said bosses.
and other structures instead of being secured to pipes. It 5. The heat exchange enhancement structure as de
is not necessary that the heat exchange enhancement 60 fined in claim 1 wherein said plurality of straight line
structure extend 360 around the pipe, stove or other bends include a first bend extending along said one side
structure. The heat exchange enhancement structure edge of said mounting portion, each said fin being posi
can also be used on heat exchange elements, pipes and tioned about said first bend at an included angle with
the like of the type used in power plants and process the plane of said mounting portion of between 60 and
plants as well as in other environments where heat dissi 65 85.
pation is necessary and/or desirable. 6. The heat exchange enhancement structure as de
The new heat exchange enhancement structure and fined in claim 5 wherein each said fin is bent approxi
method has been described with reference to the pre mately 95 to 10° about said first bend and extends at
 4,236,578 12
11
an included angle with said mounting portion of be fin; said location of said fins, when said mounting por
tween 70 to 85. tion is in heat transfer relationship to a pipe with said
7. The heat exchange enhancement structure as de longitudinal mounting portion axis extending substan
fined in claim 1 wherein said plurality of straight line tially vertically, providing each said fin with a position
bends include a first bend extending along said one side downwardly inclined and rotated about said longitudi
edge of said mounting portion and about which each nal fin axis whereby air flowing upwardly through said
said fin is positioned extending transversely of the plane fins is imparted with rotation and outward movement
of said mounting portion and a second bend extending relative to said mounting portion axis.
from one end of said first bend across said fin at an 10. The heat exchange ehancement structure as de
included acute angle with said first bend of substantially 10 fined in claim 9 wherein said mounting portion has
less than 90. opposite ends and integral mounting means on said
8. The heat exchange enhancement structure as de mounting portion spaced inwardly from said ends for
fined in claim 1 wherein said structure is made from a cooperation with a mounting device for holding said
substantially rectangular metal sheet by forming a plu mounting portion in tension around a pipe.
rality of equidistantly spaced parallel slits in said sheet 5
11. The heat exchange enhancement structure as de
extending from one longitudinal edge thereof toward fined in claim 9 wherein each said fin is bent along two
the other and terminating short of the other to define different straight lines.
said mounting portion, each said slit extending at an 12. The heat exchange enhancement structure as de
angle to said mounting portion of between 45 to 70, fined in claim 9 including a generally vertically dis
each said fin having a fin span along said one side edge 20 posed cylindrical pipe on which said mounting portion
of said mounting portion, each said fin further having an is received with the apices of said cones pointing up
acute fin edge intersecting said one side edge at an acute wardly.
angle and an opposite obtuse fin edge intersecting said 13. The heat exchange enhancement structure as de
one side edge at an obtuse angle, each said fin being bent fined in claim 12 wherein said cones slope upwardly
along a first bend line extending generally from the 25 from their bases toward their apices at angles between
intersection of said acute fin edge with said span to an 5 and 30'.
intersection point with said obtuse fin edge which is 14. A free convection type heat exchange enhance
spaced outwardly from said span, and each said fin ment structure comprising: an elongated flat mounting
being bent along a second bend line defined by said portion having opposite side edges; a plurality of fins
span. 30
9. A free convection type heat exchange enhance integral with said mounting portion and extending out
ment structure comprising: a substantially flat cylindri wardly from at least one of said side edges thereof; each
cal mounting portion having opposite circular edges said fin having a longitudinal axis and opposite fin
and a longitudinal mounting portion axis; a plurality of edges, each said fin being bent across the width thereof
fins integral with said mounting portion, each said fin 35 between said fin edges along a substantially straight line
having a longitudinal fin axis, opposite substantially bend which extends at an included acute angle to said
straight and parallel fin edges, a predetermined thick one side edge of between 50-80; each said fin having.
ness, and a predetermined width across said fin edges a first fin portion on the side of said bend toward said
perpendicular to said longitudinal fin axis; said fins mounting portion and a second fin portion on the oppo
being bent outwardly from at least one of said circular site side of said bend; said second fin portion being bent
edges of said mounting portion to have said opposite fin through an angle of 45'-75 with respect to said first fin
edges lying generally on the surfaces of different cones portion; and, each said first fin portion being bent along
having cone axes coincidental with said longitudinal said one side edge of said mounting portion through an
mounting portion axis and having cone apices spaced angle of 55'-85 in the same direction with respect to
from one another along said longitudinal mounting 45 said mounting portion as the direction in which said
portion axis a distance substantially greater than said second fin portion is bent with respect to said mounting
predetermined thickness of each said fin and substan portion.
k xx sk t sk
tially less than said predetermined width of each said
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55

60

65