Note: Descriptions are shown in the official language in which they were submitted.
1 ~63792
- This invention relates to a method o producing a
multiple coil, multiple tube heat exchanger, and particularly
such a method in which the tubes are generally circular in cross
section.
BACKGROUND OF THE INVENTION
With the advent of the energy crisis, there has been
considerable interest in the recovery of energy which might
otherwise be lost, such as the heat contained in the fluid dis-
charged from a dishwasher or the like. An important part of
a method and apparatus for this purpose is a liquid to liquid
heat exchanger, through which waste water, such as discharged
from a dishwasher, is passed in order to heat fresh water, such
as the incoming feed water for a hot water heater. Such heat
exchange avoids the heat being lost in the used wash water through
its being discarded through a conventional drain. However, the
temperature differential between the warmer liquid, such as waste
water, and the cooler liquid, such as hot water heater makeup
water, may be relatively slight, so that the heat exchanger
must necessarily be highly efficient to transfer the maximum
amount of heat from the warmer liquid to the cooler liquid.
An effective and efficient heat exchanger may consist of sets
of multiple tubes, such as three, in spaced, spiral relation
between thin cylinders. For more effective heat transfer, the
warmer liquid is circulated through the tubes, while the cooler
liquid is forced to follow a circuitous path between the turns
of the respective spiral csils, to achieve maximum contact time
of the cooler liquid with the exterior walls of the coils. In
such a heat exchanger, the tubes of the coils abut to force the
liquid to be heated to follow such a spiral path. However, in
such a heat exchanger, if a leak occurs in any tube of the coil,
the contaminated water will leak out into the fresh water being
heated. Since a hot water heater, in many instances, not only
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supplies a dishwasher but also wash basins, certain plumbing
codes reduce considerably the use of such a heat exchanger.
Thus, it is desirable to provide an efficient and effective heat
exchanger in which the warm liquid and cool liquid each flow in
separate tubes.
In U. S. patent No. 1,965,553, a series of rectangular
or triangular tubes in concentric cylindrical coils are wound
in spiral relation from the inside out, so that heat will be
transferred between different liquids, such as a refrigerant
in one tube forming alternating turns of a coil, with other
liquids in different tubes, such as liquids to be cooled, in
the alternating turns of different coils. The heat exchange
between the tubes is effected by metal to metal contact of the
tubes. When the tubes are rectangular, two sides of each tube
are in metal to metal contact with the abutting sides of ad-
joining turns of the same coil, while the top and bottom of each
turn is in metal to metal contact with the bottom and top, respec-
tively, of the turns of adjacent inner and outer coils. When the
tubes are triangular in cross section, the apices of the triangles
point outwardly in a toothed arrangement in alternating cylin-
drical coils with the apices of the tubes pointing inwardly to
intersect the preceding apices. Thus, there is theoretically
produced metal to metal contact of each side of a triangular
tube with the sides of the triangles in adjacent turns of the
same coil. Also the base of each triangular tube in the respec-
tive coils will face alternately inwardly and outwardly, so that
the base of a triangle in one coil will be in metal to metal
contact with the base of a triangle of a tube turn of the next
inner or outer row. Although the metal to metal contact of the
rectangular or triangular tubes is conducive to heat exchange,
the turns, due to deformation, misalignment, twisting or other
conditions, may reduce the heat exchanged. There are also
7 ~ 2
numerous problems involved in the construction of such a heat
exchanger, particularly since both the rectangular and triangu-
lar tubes must always be kept in essentially perfect alignment
with the turn whose side, top or bottom walls are to be engaged.
Since tubing is generally wound in a coil, the unwinding and re-
wincling in a specific relationship often produces a tendency
for the tube to twist, such twisting often causing difficulty
in rewinding. In addition, the cost of producing rectangular
or triangular tubes is much greater than that of circular or
cylindrical tubes, with the result that the cost of a heat ex-
changer having rectangular or triangular tubes may exceed the
value of the energy which might be recovered within a reasonable
time.
It is generally known to use a heat conductive mastic,
i.e. a resin having heat conducting properties to improve heat
conductivity between metals, as in U. S. patents Nos. 3,554,275
and 3,666,006 and British patent 938,372. Also, in U. S. patent
4,123,837, the use of a heat conductive mastic to improve heat
transfer between a pipe and a much larger conduit or vessel is
proposed, with an angular cover for the mastic to retain the
mastic in position. It is also suggested that the mastic may
be applied to the larger vessel and the heating pipe pushed into
the mastic. Nevertheless, these prior patents do not disclose
the novel features of the present invention.
It will also be noted that a coil can be coated by
dipping in a liquid, such operation normally being used for water-
proofing or insulation purposes. However, the heat conductive
mastic must be heated to a relatively high temperature before
it becomes a liquid, and even a dipping operation will not insure
that the interstices between all the coil turns, particularly
those deep within the coils, will be filled.
Among the objects of this invention are to provide a
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1 lS379~
novel method of producing a multiple coil, multiple tube liquid
to liquid heat exchanger; to provide such a method which is par-
ticularly adapted to be utilized with tubing having a circular
cross section; to provide such a method which enables a heat
conductive mastic to transfer heat between a warmer liquid in
one or more turns of a coil and a cooler liquid in one or more
turns of the same or adjacent coils; to provide such a method
which will produc~ an effective contact of mastic with essentially
the entire surface of each tube for the length of each coil to
insure that the mastic will fill the spaces between adjacent
turns of each coil, as well as to insure that the mastic will
fill the spaces between the turns of successive coils; to provide
such a method which will insure that the mastic will remain in
essentially compressed position between the turns of the respec-
tive coils; to provide such a method which will be simple andeffective in operation; and to provide such a method which may
be carried out without undue expense.
SUMMARY OF THE INVENTION
In accordance with this invention, a heat exchanger
is produced from a plurality of cylindrical coils, each formed
from multiple tubing of essentially circular cross section and
through which different liquids are to be passed, with the usual
number of tubes being two, i.e. a first tube through which a
warmer liquid is passed and a second tube through which a cooler
liquid is passed. A mastic layer is provided in the interstices
between the turns of the tubes forming adjacent cylindrical
coils, and also on the inside and outside of the turns of the
inner and outer coils. Preferably, the turns of each coil are
generally in contact with the adjacent turns of the same coil
and also with the turns of the adjacent coil, both beneath and
above. A principal feature of this invention is the placement
of a mastic layer on the outside of each coil, after winding,
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1 1637g~
and winding the turns of the next coil against the preceding
coil, so as to squeeze the mastic layer into the interstices
between the coil turns. The mastic layer may be applied to the
outside of one coil, after its completion, to the entire length
of the coil before winding the next coil. Or the mastic layer
may be applied in the form of beads or ribbons from a pressure
gun or the like, as the next coil is being wound, so that the
mastic is applied only as the turns of the next coil are wound
against the previous coil. In order to minimize flattening or
kinking, the tubes are merely subject to sufficient force to
bend them, but this produces sufficient compression to insure
that the mastic will be pushed into all of the desired inter-
stices. In further accordance with this invention, a first
cylindrical coil of dual tubes may be wound on a mandrel, mastic
applied, then a second coil wound around the first coil, mastic
applied and additional coils wound around each previous coil
and mastic applied until a desired number of coils has been ob-
tained. In addition, the first turn of each coil is preferably
made in the groove between two turns of the preceding coil, such
as the first two, not only to provide a desirable position for
each turn of the next coil to compress the mastic, but also to
reduce the cross sectional area of the interstices between the
coils. Since it is preferable that the rate of flow of the
liquid through each coil be substantially the same, the diameter
of the coils may be increased as the coils progress outwardly,
in order to provide a greater volume for the longer path of
flow through an outer coil and thus insure that the liquid which
enters the alternating tubes of the several coils will arrive
at the exit at approximately the same time. It is also possible,
through a proper proportioning of the inside diameter of the inner-
Most coil and winding each coil to an appropriate position, such
as between the second and third to last turns of the preceding
1 ~379~
coil, to use the same diameter tubing for each coil, i.e. each
tube thereby having the same total volume as other tubes of the
same or ano~her coil. In addition, the turns of the first coil
are preferably attached together, as by soldering, to prevent
the coil from unwinding when released from a winding mechanism.
Also, the first and last turn of each coil, outwardly from the
first coil, is attached, as by soldering, to the exposed adjacent
turn of the previous coil. Another advantage of winding the turns
of the next coil as nearly as possible into the grooves between
turns of the preceding coil is that, with the turns of the first
coil secured together, there is much less tendency for the next
and additional coils to unwind after release from the winding
mechanism.
The winding operation may be carried out by machine or on
a rotating mandrel, to which may be attached special jigs for
holding the initial ends of the tubes of the respective coils
during winding.
THE DRAWINGS
The foregoing and additional features wili become more
readily apparent from the following description, taken in conjunc-
tion with the accompanying drawings, in which:
Fig. 1 is a side elevation of a heat exchanger produced
in accordance with the method of this invention.
Fig. 2 is a cross section, on an enlarged scale, of the
heat exchanger of Fig. 1 taken along line 2-2 of Fig. 1 but in-
cluding a top plan view of the coils inside.
Fig. 3 is a fragmentary vertical section, on a further
enlarged scale, taken at the position of line 3-3 of Fig. 2.
Fig. 4 is a cross section, on a further enlarged scale,
of a tube fitting, taken along line 4-4 of Fig. 2.
Fig. 5 is a fragmentary side elevation illustrating a dual
coil winding operation of the method of this invention, the
~ 1637~2
application of a heat conductive mastic being omitted for clar-
ity of illustration.
Fig. 6 is a front view of a jig used in the dual coil
winding operation of Fig. 5.
Fig. 7 is a fragmentary view, in side elevation but
partly in section, illustrating the application of mastic to
each dual coil after winding.
Fig.i8 is a fragmentary end view also showing the mas-
tic application of Fig. 7.
Fig. 9 is a fragmentary side elevation similar to Fig.
7, but illustrating an alternative application of mastic.
Fig. 10 is a fragmentary end view also showing the
alternative application of mastic.
Fig. 11 is a side elevation of a first dual tube coil
of an alternative arrangement, after winding on a mandrel and
the application of a mastic layer to the outside thereof.
Fig. 12 is a side elevation showing a second dual tube
coil of larger tubing, wound on the first coil of Fig. 11 and
a layer of mastic applied to the outside thereof.
Fig. 13 is a side elevation showing a third dual tube
coil, of still larger tubing, after winding on the coil of Fig.
12, removal of the mandrel, application of mastic to both the
inside and outside and installation of sets of corresponding
tubing ends.
PREFERRED EMBODIMENT OF THE INVENTION
A heat exchanger produced by the method of this inven-
tion may be installed, as in Fig. 1, within a housing H from
which connections 10, 11, 12 and 13 extend, in opposite direc-
tions, from the upper and lower portions thexeof. It will be
understood that the housing H may be installed in a vertical
position, as shown, or in a horizontal position, or in any appro-
priate angular position. Also, the housing H may be supported
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~63~9~
b-~ a ~edestal, stand ! or the like, or ma~r be sus~ended from a
su~?ort above it, or mounted on a wall, ~artition or the li~e,
as bv an a~Pro~riate bracket. The heat exchanqer in housinq H,
as ln Fiq. 2, maY include a series of concentric coils, such as
inner coil Cl, intermediate coils C2 throuqh C7, res~ectivelv,
and an outer coil C8. The o~osite ends of the tubes forminq these
coils extend to the a~ro'~riate connection 10, 11, 12 or 13.
Each of these coils is a dual tube coil, i.e. a first tube for
one liquid, such as hot or warmer, and a second tube for another
liquid, such as cold or cooler. It will be understood, of course,
that two or more liquids to be heated or cooled may be circu-
lated separately from each other in additional tubes of the
respective coils. As indicated, such heat exchanger is partic-
ularly adapted for use in the method of and apparatus for re-
covery of waste energy, such as from a dishwasher previouslyreferred to.
As in Figs. 2 and 3, coil C1 is formed by a pair of
tubes 15 and 16 of substantially circular cross section, the first
of which extends between the connections 10 and 11, while the
other extends between the connections 12 and 13. Thus, tube
15 carries warmer liquid, from top to bottom as indicated by
the arrows at connections 10 and 11, while tube 16 carries cooler
liquid, from bottom to top, as indicated by the arrows at con-
nections 12 and 13. The tubes 15 and 16 are wound simultaneously
about the same radius, to form the coil, with the turns of the
respective tubes 15 and 16 alternating. Similar tubes 17 and
1~ form the second coil C2, again extending between the respec-
tive connections 10, 11 and 12, 13, and being wound longitudin-
ally about essentially the same radius, so that the turns of
the tubes 17 and 1~ again alternate. Coil C3 is formed from
similar tubes 19 and 20, again extending between the respective
connections 10, 11 and 12, 13 and being wound about essentially
, . .; ,~
~fi37~s~
the same radius in longitudinal relation, so that the turns of
tubes 19 and 20 will again alternate. The tubes 15, 16, tubes
17, 18 and tubes 19, 20 are shown as being the same diameter,
while tubes 21 and 22 of the fourth coil C4 are shown as of a
larger diameter, but again extend between the respective con-
nections 10, 11 and 12, 13 and also may be wound about essen-
tially the same radius, again in longitudinal, alternating re-
lationship. Similar tubes 23 and 24 forming coil C5, tubes 25
and 26 forming coil C6, tubes 27 and 28 forming coil C7 and
tubes 29 and 30 forming coil C8 may have the same diameter as
the tubes 21, 22 of coil C4. The tubes of each of these coils
are again wound in longitudinal relation, so that the turns of
the tubes will alternate in the coil, with the turns of each
coil being wound about essentially the same radius so that the
diameter of each turn will be essentially the same as the other
turns of that coil. In accordance with this invention, the
first turn of each coil may also, during winding, be connected
to the first turn of the previous coil, as by solder or the like
connections 31 of Fig. 2. Other connections will be described
later. The tubes forming the coil are conveniently formed of
annealed copper or a copper alloy in sufficiently soft condition
to permit bending into coil shape, copper being advantageous
because of its high heat conductivity and also facilitates con-
nections, as by soldering. However, a suitable aluminum or
aluminum alloy, although having a slightly less thermal conduc-
tivity than copper, may be a sufficiently less expensive metal
to result in a lesser total cost of installation and use. Other
heat conductive materials may also be found suitable.
The preferred construction of the heat exchanger in-
cludes a layer 33 of a heat conductive mastic on the inside of
coil Cl and a similar layer 34 of heat conductive mastic on the
outside of coil C8. Also, mastic 35 extends between the turns
1 ~637~.~
of each coil and also between the turns of the adjacent coils.
In accordance with this invention, the mastic is placed under
compression during the winding operation, so as to squeeze out
any air, insure a contact of the mastic with the entire surface
of each tube for the length of each coil, insure that the mastic
will fill the spaces between adjacent turns of each coil and also
insure that the mastic will fill the spaces between the turns of
each coil and the turns of the next outer and inner coil.
The mastic may be a heat conductive mastic, such as that
supplied by Virginia Chemicals, Inc. of Portsmouth, Virginia,
U. S. A., which is composed of synthetic resins, plasticizers and
a thermal conductive filler, such as aluminum particles. Among
the specifications for this mastic are that it has little or no
odor, adheres well to clean, dry surfaces, has a shrinkage of nil,
is not absorptive of water vapor and is resistant to vapor trans-
fer. This mastic also is specified as having a reading under
ASTB Test D217-526 of 25.0 to 32.0 mm, a rheometer reading, based
upon a 0.104 orifice at 20 psi and 77F, of 75-175 seconds, a
minimum flash point of 450F, no slump of a 1/4 inch bead at 850F.
It is further specified that this mastic will not melt or run at
220F, will not become brittle at -50F and has a pH of 7.0+. It
is possible that other mastics may be utilized, such as those
referred to as "heat transfer cements" in U. S. patent No.
4,123,837, i.e. those commercially available under the trade marks
25 $"Konduct", obtainable from John L. Lord & Sons, Ltd. of Bury,
Lancashire, England, "Therman", obtainable from Therman ~anu-
facturing Company of Texas, U. S. A., and "Thermfas", obtainable
from Atlas Preservative Co., Ltd., of Erith, Kent, England and
Benjamin Foster Company of U. S. A.
Insulation 36, such as of the fiberglass and polyure-
thane or polystyrene type, to povide coil support, as for
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shipping, may be placed within the inner coil Cl and similar
insulation 37 may be placed outwardly of the outer coil C8 and
at 1:he ends of the coils, within the opposed sides 39 and 40 of
the housing H and conventional ends therefor. The sides of the
housing may be attached together in a suitable manner, as through
the use of flanges 41 on sides 40, for connection to the sides,
as by welding. The ends of the housing may be attached to the
sides in the same manner, or may be removable to provide access
to the coils inside the housing. Preferably, the connections
10, 11, 12 and 13 extend through the sides 40 of the housing,
each connected to a sheath or sleeve 42 or 43, respectively,
surrounding the ends of the tubes carrying the same liquid,
as in Fig. 2. Thus, sheath 42 may be attached to connection
10 and surrounding the ends of tubes 15, 17, 19, 21, 23, 25,
27, 29 carrying one liquid, such as the warmer liquid, while
sheath 43 I~ay surround the ends of tubes 16, 18, 20,/24, 26,
28, 30, carrying the other liquid, such as the cooler liquid.
As in Fig. 4, the ends of the tubes to be at~ached to the inside
of sheath 42, for instance, may be inserted in the sheath, as
with one tube at the center and the remainder surrounding it,
or any other suitable arrangement which will minimize the space
between the tubes and/or the sheath. Then, the outside of the
tube ends are attached to each other and to the inside of the
sheath, as by a suitable material 44, such as Sil-Fos, applied
by a soldering, brazing or similar operation. The position of
the heat exchanger is preferably vertical or upright, so that
drainage to prevent freezing may be accomplished. Countercur-
rent heat exchange is preferable, as indicated. If the heat
exchange is to take place between a heated liquid which is dis-
charged to the heat exchanger intermittently, such as from adishwasher, it may be desirable that the inlet for the warmer
liquid be at the bottom and the inlet for the cool liquid at
1 ~6~792
the top, as at connections 11 and 13, respectively, so that the
capacity of the coils carrying the warmer liquid may be equal
to the amount of liquid intermittently discharged from the dish-
washer, for instance. Thus, the warmer liq~id may stand in the
heat exchanger to permit the cooler liquid to extract the greatest
amount of heat from the warmer liquid.
As will be evident from Fig. 3, the tubes carrying
the warmer liquid, such as tubes 15, 17, 19, 21, 23, 25, 27,
29, alternate in each coil with the tubes carrying the cooler
liquid, such as tubes 16, 18, 20, 22, 24, 26, 28 and 30. Each
tube carrying warmer liquid further generally opposes tubes in
each adjacent coil carrying cooler liquid, but for approximately
the same area of each. Thus, there is not only transfer of
heat between tubes in the same coil, but also between tubes in
adjacent coils. Normally, the tubes of each coil will engage
adjacent tubes of that coil, as well as tubes of adjacent coils,
at an approximate point of tangency. Over the remainder of the
opposed areas, the mastic 35 between the tubes increases consid-
erably the amount of heat transferred across the spaces between
adjacent tubes of the same coil, as well as across the spaces
between tubes of adjacent coils.
In accordance with this invention and as illustrated
in Fig. 5, a method of producing a multiple coil, multiple tube
liquid to liquid heat exchanger includes the formation of an
inner coil Cl, conveniently by wrapping the separate tubes 15
and 16 in alternating relation about a mandrel 46, mounted in
a rotating chuck 47 having a clamping adjustment 48 and rotated
in a suitable direction, as in the direction of arrow 49. The
ends of the respective tubes 15 and 16 may be placed in a jig
J or J' in a position extending generally tangentially toward
the mandrel. Jigs J and J' are mounted at an opposite end of
a bracket 50 and each includes a plate 51 of Fig. 6 having a
~ ~379~
flange 52 for removable attachment to the bracket 50. Jigs J
and J' are essentially the same in construction and each jig
plate 51 is provided with holes of a suitable diameter arranged
in a position such that, after winding, the tubes may be more
readily placed in the sheath 42 or 43. As will be evident, the
arrangement of the holes fox receiving the tubes is within a gen-
erally circular outline so that, when the jig J or J' is removed,
the ends of the tubes may be squeezed together and fitted into
the corresponding sheath. Thus, the jig plate 51 may be provided
with a hole 53 for tube 15 or 16, a hole 54 for tube 17 or 1~,
a hole 55 for tube 19 or 20, a hole 56 for tube 21 or 22, a hole
57 for tube 23 or 24, a hole 58 for tube 25 or 26, a hole 59 for
tube 27 or 28, and a hole ~0 for tube 29 or 30. As will be
evident, the arrangement of the holes in jig J corresponds gen-
erally to the arrangement of the tubes in the sheath, as inFig.~. When the inner coil C1 is to be wound on the mandrel
46, the first tube to be wound, such as tube 15, may be placed
against an abutment 61 mounted on the mandrel 46, to stabilize
the turns of the coil and maintain them in an inclined position
during winding. In general, the tube 15 is inserted in the
appropriate hole 53 in jig J and started around the mandrel
against abutmentu61. Then, the tube 16 is placed in the appro-
priate hole 53 in jig ~' and placed against the mandrel along-
side tube 15, but on the opposite side of the mandrel from abut-
ment 61, as will be evident from Fig. 2. Then, the tubes 15and 16 are wound together about the mandrel in as closely abutting
relationship as possible. In order to maintain the relation-
ship of the turns of coil Cl, which forms the base for subsequent
coil winding, the turns of coil Cl are conveniently attached
together, as by solder 62, either as each double turn is wound
or after several double turns have been wound. This attachment
of the coil turns together guards against a tendency for the
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1 ~6~7~2
coil to unwind or the turns of the coil to be spread apart,
~hen the next coil is wound against it. The tubes 15 and 16
extend from opposite sides of the mandrel and may then be cut
at an appropriate position, if not precut, then the ends may be
bent: slightly toward the opposite end of the coil to assume a
position useful for insertion in a sheath 42 or 43. It will
be noted that while tube 15 provides the first turn of coil
Cl, tube 16 provides the last turn thereof, in order to equal-
ize the volume of the two tubes in the coil. The next coil C2
is wound on the first coil Cl,~ after or as a mastic has been or
is applied to the outside of coil Cl, so that when the second
coil C2 is wound onto the first coil, the mastic will be com-
pressed by the winding of tubes 17 and 18 against coil Cl and
squeezed into the spaces between the turns of coil Cl and also
coil C2, as well as into the spaces between coils Cl and C2.
In accordance with this invention, the second coil, after its
tubes 17 and 18 have been inserted in the appropriate holes in
jigs J and J', is wound against the initial coil by placing
the fi~st turn of the next coil between two turns of the pre-
vious coil, normally the first two turns. The first turn ofthe second coil, i.e. of tube 17, is also attached to the pre-
vious coil, as by solder 31 of Fig. 2, as the winding of the
next coil is begun against the mastic on the preceding coil.
This tends to maintain the position-of the next coil relative
to the previous coil. Also, particularly when the next coil
is formed of tubes of essentially the same diameter as the pre-
vious coil, the placement of each turn of a coil in the groove
between turns of the coil beneath it further stabilizes the
coil being wound and assists in preventing the coil turns from
unwinding or separating when the pressure of a succeeding coil
being wound is exerted against it. At the opposite end of the
coils, each tube 17 and 18 extends from opposite sides of the
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~ 1637~2
coil, and tangentially from between two turns of the preceding
coil, preferably between the second and third from last turns.
The last turn of the tube 18 of coil C2 is also attached to the
preceding coil, as by solder 63 of Fig. 5. The respective tubes,
afte!r winding and attachment to the previous coil, may be cut,
if rlot precut, and the ends bent to a configuration which will
facilitate their being placed in a sheath, as before, such as in
the configuration shown at the left in Fig. 5. Thus, the attach-
ment of the last turn of each coil to the previous coil main-
tains the tube in the position bent. Coil C3 is similarlywound on coil C2 by placing the end of tube 19 in hole 50 of
jig J, then wound a half turn into the mastic in the groove
between the first two turns of coil C2 and attached thereto,
while the end of tube 20 is placed in hole 50 of jig J' and
placed alongside tube 19 and the two tubes wound together against
the mastic to complete coil C3, the last turn of which is attached
to coil C2 beneath. Since tubes 17, 18 and 19, 20 may be of the
same diameter as tubes 15, 16, there is no difficulty.in en-
gaging the turns of coils C2 and C3 with the grooves between
the turns of the preceding coil, against the mastic, of course.
Also, the first turn of tube 21 of coil C4, after the end is
placed in hole 56 of jig J, is placed against the groove between
the first and second turns of coil C3 and will fit into the groove
even though tube 21 is larger in diameter than tubes 19 or
20. Also, tube 21 may, for its first half turn, follow in that
groove and be attached to preceding coil C3 beneath. Thus,
after the end of tube 22 is placed in hole 56 of ~ig J', the
tube 22 may be abutted against tube 21 and the two wound to-
gether, against the mastic, with tube 21 following the groove
for the first 360 of winding the coil C4. As will be evident
from Fig. 3, further turns of coil C4 do not necessarily fully
engage the grooves between turns of the preceding coil, but ride
onto the turns of the prior coil until the number of turns times
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the difference in diameter equals the diameter of the tubes of
the preceding coil, when one full turn of coil C4 will again fit
directly into a groove between turns of the preceding coil.
When the end of coil C4 is reached, tube 21 is extended tangen-
tially from the coil and tube 22 wound for an additional halfturn, then attached to the coil beneathl as by solder 63, and
extended;tangentially from the coil. Then the tubes may be cut
off, if not precut, and bent to an appropriate position for easier
insertion in a sheath 42 or 43. Since the tubes of coils C5
through C8 are shown as having the same diameter as the tubes
of coil C4, there should be little or no difficulty in fitting
the tubes of the respective coils into the grooves between turns
of the preceding coils, when winding against the mastic. Thus,
coils C5 through ~8 may be installed in essentially the same
manner as described for coil C4, it being noted that the last
turn of coil C4 should extend generally from between the second
and third from last turns of coil C3 but that the turns of coils
C5 through C8 may readily be extended from between the second and
third from last turns of the preceding coil. This relationship
is indicated at the left in Fig. 5, although the tube 22 of coil
C4 which is shown as abutting the third from last tube 20, in
the lower section, will be closer to the groove between tubes
19 and 20 of coil C3 when tube 20 actually extends from the coil
at a position approximately 90 from the section.
Copper or an alloy thereof is a preferred material for
the tubes for two reasons: first, copper tubes are readily bent
and tend to stay in the desired position, and second, parts of
such metal are more reasily attached together by a reasonably
low temperature operation, such as soldering. In applying mastic
to the coil which has been wound prior to winding the next coil
thereon, any suitable method may be usedl two of which are illus-
trated in Figs. 7-10. Thus, as in Fig. 7, a layer 65 of mastic
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~ ~3 f ~2
may be applied to the outside of the previous coil, such as coil
Cl, for its entire length, as by a trowel, prior to winding the
tubes of coil C2 onto the previous coil. The application of the
mastic layer 65 to the entire periphery of the previously wound
coil is convenient for a hand winding operation, in which the
tubes being wound are guided onto a rotating assembly by hand,
or by a jig which is hand operated. As will be evident, the
mastic is placed on the previous coil to a depth such that the
grooves between the previous coil and the next coil will be com-
pletely filled, as well as the spaces between the turns of theprevious coil and the next coil. As indicated in Fig. 7, the
mastic does not need to be forced initially into all of the cross
sectional areas of the grooves between the turns of the pre-
vious coil, since the pressure of the tubes of the next coil,
as it is wound, such as tubes 17 and 18, will squeeze the mastic
into the spaces as the tubes 17 and 18 are maintained in a tan-
gential relation to the previous coil, and the assembly is rotated
in the direction of arrow 49. The effect of this rotation is to
cause the tubes 17 and 18 to move into the grooves of tubes 15,
16 and to extrude the mastic into all of the spaces mentioned
above.
An alternative method of applying the mastic is illus-
trated in Figs. 9 and 10 in which a pair of mastic beads 66
are deposited in the respective grooves between the turns of
the previous coil and into which the tubes being wound are to be
forced. Such mastic beads may be discharged through nozzles
67 of a pressure gun 68 which may be of any suitable type. As
in Fig. 10, the winding of tubes 17 and 18 of coil C2, for in-
stance, onto coil Cl will force tubes 17 and 18 into engagement
with tubes 15 and 16 and thereby compress the mastic beads 66
into the grooves between tubes 15 and 16, as well as into grooves
between tubes 17 and 18. Such compression will also express any
~ 163~
air from the mastic and will also force the mastic, when applied
in appropriate quantity, into all of the interstices between
coils Cl and C2. As will be evident, excess mastic will tend to
be forced ahead of tubes 17 and 18 as they are wound onto coil
Cl. When nozzle 67 and gun 68 are used, it may be desirable
to change nozzles to those having a different spacing and dif-
ferent capacity when applying mastic to the grooves between
turns of tubes of a larger diameter, such as those of coils C4
through C7. The thermal mastic supplied by Virginia Chemicals,
previously referred to, is particularly adapted to be discharged
through a gun as a bead, ribbon or the like. Of course, such
a gun may also be utilized in connection with a hand operation,
although it is particularly adaptable for use in a machine opera-
tion, in which the respective coils are wound by a coil winding
machine. Of course, there may be some hand operations involved,
such as the initial setup of the tubes in the jig, the attach-
ment, as by soldering, of the turns of the initial tube together,
and the attachment, as by soldering, of the first and last turns
of each subsequent coil to the previous coil.
After the coils have been wound and the attachments
of the coil turns made, the ends of the respective tubes may
be placed in the respective sleeves and the tube ends attached
to the sleeve and to each other. This may be accomplished either
before or after the assembly is removed from the mandrel. The
mandrel is generally horizontal, as indicated, but may have a
slight taper to facilitate the removal of the coil assembly
after winding, or the mandrel may be the well known collapsible
type in which one or more segments are withdrawn inwardly and
the remaining segments collapsed slightly, or any other suitable
t~pe. After inner and outer mastic layers 33 and 34 of Fig. 2
are applied, as well as mastic layers on the ends of the coils,
the assembled coils may be placed in the housing H and connections
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10, 11, 12 and 13 attached to the respective sheaths. Prefer-
ably, the inner insulation 36 and outer insulation 37, as well
as the end insulation, are adapted to support the coils, for
shipping purposes. Although the inner and outer insulation may
be placed, then the end insulation ~laced and the respective
ends of the housing attached in position, it may normally be
found more convenient to utilize a foam insulation, as of a con-
ventional type. Thus, one end of the housing may be attached
and the foam introduced through the open end but the inside of
the housing may be more completely filled by providing one end
of the housing with a small hole through which the insulation
foam may be introduced after both housing ends are attached.
Such a hole may be tapped so that it may be closed with a plug
after the foam insulation has been introduced.
The winding of each coil in which each of the respec-
tive tubes leaves the assembly a distance from the end of the
preceding coil, such as from the groove between the second and
third to last turns of the preceding coil, not only facilitates
the attachment of the respective coils together and the bending
of the end of the tube into an appropriate position adjacent
the remaining tubes carrying the same liquid, but also permits
all of the coils to be formed of tubes of the same diameter
with an appropriate diameter of the inner coil. In addition,
a mandrel of an appropriate size, such as between 10 and 11
inches in diameter for 1/2 inch tubes and an appropriate length
of each tube, will permit each successive outer tube to have
one less turn and have approximately the same length from one
end of the coil to the other, such as within 5~, so that each
tube will have generally the same total volume. Thus, the flow
of the liquid through each tube will reach the opposite end at
approximately the same time.
The diameter of the tubes of successive coils may be
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increased, for each coil, in order to provide a total volume
in each tube corresponding to the length of a tube around its
spiral path, and at the same time, retain essentially the same
length for each of the coils, so that the liquid flowing through
each tube would require approximately the same time to reach
the opposite end. The method of producing such a construction
is illustrated in Figs. 11-13, it being understood that, al-
though only three coils are shown, additional coils may be added
with proper proportioning of the diameters of the tubes forming
the same. In addition, the ends of the tubes carrying the same
liquid may be positioned in the same manner or differently than
in connection with previous embodiments. Thus, the initial coil
may be wound on a rotating mandrel 74, with the first coil being
wound by bending tubes 75 and 76, so as to extend essentially
longitudinally of the mandrel, when wound onto the mandrel as
it rotates, until the end of the coil is reached, with each
end of tubes 75 and 76 being bent to extend substantially longi-
tudinally of the mandrel. As before, the adjacent turns of the
inner tube may be attached together, as by soldering. Then,
a layer 77 of mastic may be applied to the outside of the tubes
75 and 76. As in Fig. 12, a second coil may be wound by bending
the ends of tubes 78 and 79 to a position extending generally
longitudinally of the mandrel and adjacent the ends of tubes
75 and 76. As before, tubes 78 and 79 are wound against the
mastic layer 77 applied to the outside of the first coil, with
tubes 78 and 79 in abutting relation and the first turn of the
second coil being attached to the first turn of the preceding
coil and disposed merely outwardly thereof. The tubes 78 and
79, of course, have a slightly greater diameter than tubes 75
and 76. When the opposite end of the second coil is reached,
the last turn of the second coil is attached to the last turn
of the first coil. It will be noted that tubes 75 and 78 form
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1 ~ ~37~ ~
the first turn of each of the first and second coils, but that
tubes 76 and 79 form the last turn of the respective coils.
This arrangement is for the purpose of obtaining interleaved
coils from the tubes 75, 76 and from the tubes 78, 79 of the
same tube length, and therefore total volume. The ends of the
tubes 78 and 79, after attachment of the last turn of tubè 79,
are again bent to extend generally longitudinally of the lilan-
drel~ rather than tangentially. Also, a layer 80 of mastic
is applied to the outside of the second coil, as in Fig. 12,
after which the third coil comprising tubes 81 and 82 are wound
on the second coil, as in Fig. 13, with the first turn of the
third coil being placed atop the first turn of the second coil.
The tubes 81 and 82 are wound against the mastic layer 80, so
as to squeeze an~ air out of the mastic, push the mastic into
the interstices between the turns of the second coil and also
between the interstices of the third coil, as well as into the
interstices between the second and third coils. Again, after
the last turn of the third coil, i.e. of tube 82, has been wound
and attached to the turn of tube 79 beneath, the ends of tubes
81 and 82 are again bent, so as to extend generally longitudinally
of the mandrel. While still on the mandrel, the respective ends
of tubes 75, 78 and 81 may be inserted within a sleeve or sheath
43' and then the outside of the tubes attached to each other
and to the inside of the sleeve, such as by Sil-Fos, as described
previously in connection with sleeve 43 of Fig. 4. Similarly,
the respective ends of tubes 75~ 78 and 81 may be inserted within
and attached to the inside of a corresponding sheath or sleeve
43'. Then, the coil assembly may be removed from the mandrel
and an inside layer 33' of mastic applied to the inside of the
innermost coil and an outside layer 34' of mastic applied to
the outermost coil. Also, the mastic may be spread against the
ends of the coils, as at 83. The coil is then readily placed
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within a housing with insulation on the inside and the outside
and at the ends, but the connections for the respective sleeves
42' and 43' extending through the ends of the housing, rather
than the sides, as before.
Although a preferred embodiment of the method of this
invention has been illustrated and described, as well as cer-
tain variations indicated, it will be understood that other em-
bodiments may exist and additional variations made, all without
departing from the spirit and scope of this invention.
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