Low to medium pressure high temperature all-ceramic air to air indirect heat exchangers with novel ball joints and assemblies

What is disclosed herein deals with low to medium pressure, high temperature, all ceramic, air-to-air, indirect heat exchangers, novel ball joints; connecting slip ring collars for ceramic tubes, that are useful in such heat exchangers, systems comprising several heat exchangers or systems comprising heat exchangers that are fabricated such that they provide more efficient heat exchangers than has been possible heretofore.

The invention disclosed and claimed herein deals with low to medium 
pressure, high temperature, all ceramic, air-to-air, indirect heat 
exchangers, novel ball joints, high load-bearing ceramic tube sheets, and 
connecting slip ring collars for ceramic tubes that are useful in such 
heat exchangers. Systems utilizing several heat exchangers or systems 
comprising heat exchangers are fabricated such that they provide more 
efficient heat transfer than has been possible heretofore. 
The heat exchangers of this invention are not merely modified standard heat 
exchangers that are in use today, but are new and novel heat exchangers 
which require half the number of tube sheets of standard heat exchangers 
and which have outstanding efficiencies in operation, among other valuable 
benefits. Further, they have reduced tube to seal and tube sheet to shell 
leakage by a significant amount by use of the novel connector slip ring 
collars; novel ball joint assemblies and dense, interlocked, refractory 
tube sheets. The novel heat exchangers of this invention also reduce the 
tube to tube sheet leakage by a significant factor and reduce the tube 
sheet to tube shell leakage by a significant factor. The heat exchangers 
of this invention do not require air cooled tube sheets as does the prior 
art heat exchangers because of the novel low-heat conductive refractory 
shapes between the tube sheets and the shell of the heat exchanger. The 
entire manufacturing and assembly cost for tube sheets and tubes for these 
heat exchangers is reduced by over fifty percent as compared to the cost 
of manufacturing and assembly of the prior art heat exchangers. Further, 
the heat exchangers of the present invention do not lose any ability to 
replace individual tubes, nor do they lose the ability to use standard 
ceramic tubes. 
Thus, it is one object of this invention to provide heat exchangers having 
the advantage of significantly reduced leakage of air. This reduced 
leakage allows for usage of higher pressures and essentially prevents 
mixing of dirty air with clean air during the operation of the heat 
exchangers. 
It is yet another advantage of this invention to provide heat exchangers 
having the benefits of reduced cost of manufacturing and assembly, and it 
is still another object of this invention to provide heat exchangers which 
can be used with low to medium pressures and high temperatures where 
required. 
BACKGROUND OF THE INVENTION 
Indirect, air-to-air heat exchangers are devices that are used to extract 
thermal energy from dirty heated gas and provide that thermal energy to a 
wide variety of diverse application such as heating clean ambient air, 
liquids, chemical processes, and similar uses. The source from which the 
extraction is made is usually waste gas of some kind, such as hot waste 
fumes from an industrial furnace or the like. 
In general, conventional shell and tube heat exchangers utilize a series of 
tubes supported at their ends by what is known in the art as tube sheets. 
Ambient air flows through, or is forced through the tubes, and a cross 
flow of the hot gases, usually waste gases, is passed in a cross flow over 
the outside surface of the tubes to heat the air flowing through them. 
This is the concept of "heat exchange". It will be noted that the 
applicant contemplates that the cross flow can be air and the material 
flowing through the ceramic tubes can be hot or waste gases. 
Some conventional types of heat exchangers employ metal tubes which are 
welded at their ends to a supporting metal tube sheet. These metal heat 
exchangers are subject to deterioration from chemically corrosive or 
abrasive particles and further, they are subject to wide latitudes of 
expansion under operating conditions. 
Conventional heat exchangers employing ceramic components have been used in 
the past in these types of adverse environments. One type of heat 
exchanger in this category employs a sponge or matrix made of ceramic 
material. The particulates in the waste fumes have a tendency to plug the 
matrix after a period of time thereby decreasing the efficiency and, in 
some instances, creating a fire hazard. 
Yet another type of heat exchanger employs metallic springs pushing against 
one end of the ceramic tube or tube sheet in an effort to provide sealing 
engagement between the tube and the supporting tube sheet. Systems 
employing metal components to seal ceramics are subject to leakage 
problems since metal has a different rate of expansion than ceramic. In 
addition, the metallic components are still subject to deterioration under 
the above-mentioned adverse conditions in which these types of heat 
exchangers may be used. Also, in the likely event of power failure, the 
metallic components will fail when air side cooling stops. 
Most of the known heat exchanger designs employ straight sided tubes which 
empty into plenums formed between the supporting tube sheets and the inner 
wall of the external housing or casing. The plenums are designed to carry 
the ambient air to other zones in the internal heat exchanger construction 
employing another set of tubes for passing the air back through the 
central chamber through which the heated waste fumes flow. Thus, the heat 
exchangers are normally stacked or otherwise fastened together to increase 
the operating flow length of both the ambient air and the waste gas and 
the flow of the ambient air between the plenums and tubes creates a 
pressure loss within the system. These pressure losses must be overcome by 
an increase in the horsepower of the fans for moving the ambient air in 
order to maintain a given velocity of the ambient air flow. These pressure 
losses also make it difficult to operate at high pressures, and 
consequently, the heat exchangers of the prior art are not operated at the 
higher pressures, or if attempts are made to do so, there is severe 
leakage. These pressure losses also make it difficult to maintain an air 
tight seal from the ambient air side to the gas side subsystem. The 
resultant leakage which may occur not only decreases the flow of the 
ambient air, but also allows air to flow into the fumes to reduce overall 
heat transfer efficiency. Also, there is an acute operating temperature 
loss in the heat exchanger with this type of arrangement. Air Side 
temperatures at operation of the prior art heat exchangers range from 
about 800.degree. F. to about 1200.degree. F., while the temperatures 
permitted by the use of the heat exchanger of the instant invention can 
range from 800.degree. F. to 2400.degree. F. Further, the pressures at 
operation of the prior art heat exchangers range from 0.25 psig to 250 
psig, while the pressures permitted by the use of the heat exchanger of 
the instant invention can range from slightly above zero psig to 15 psig. 
Therefore, for purposes of this invention, what is meant by "low to medium 
pressure" are pressures in the range of slightly above zero psig to 15 
psig, and what is meant by "high temperatures" are temperatures in the 
range of 1800.degree. F. to 2800.degree. F. 
One of the most egregious forms of inefficiency in heat exchangers occurs 
in the connections of the tubes to the tube sheets, wherein leakage is 
usually of a high volume. Further, these prior art connections are 
machined to decrease the tolerances and to prevent high leakage and this 
adds to the overall cost of such systems. In addition, the tube sheet 
itself is subject to expansion and when it expands, it expands in an 
uncontrolled manner which causes the tube sheet to move out of alignment, 
and thus causing more leakage. The prior art tube sheets also have a 
problem in that the tiles are manufactured such that they contain only one 
half of a tube opening in them and thus, that means many tube tiles have 
to be mortared together to obtain a tube sheet. Since these mortared 
joints microcrack under operating conditions, the more mortar joints that 
are used in a heat exchanger, the more leaks that occur in the tube 
sheets. 
The heat exchangers of the prior art that are subject to many of the 
problems set forth above can be found in one or more of the following 
patents: U.S. Pat. No. 1,429,149, U.S. Pat. No. 1,974,402, U.S. Pat. No. 
3,019,000, U.S. Pat. No. 3,675,710, U.S. Pat. No. 3,923,314, U.S. Pat. No. 
4,018,209, U.S. Pat. No. 4,106,556, U.S. Pat. No. 4,122,894, U.S. Pat. No. 
4,449,575, and U.S. Pat. No. 4,632,181, and the United Kingdom patents, 
191,175, issued in January, 1923, and 2,015,146, issued in September of 
1979. 
One notable publication dealing with a flexible ball joint system for 
joining ceramic heat exchanger tubes to tube sheets is that entitled 
"FLEXIBLE BALL JOINT SYSTEM", dated Apr. 11, 1995 in which there is shown 
a flexible ball joint system sold by Sonic Environmental Systems, Inc. 
wherein there is shown in an exploded view, a plug, a ball seal, a collar 
and a ceramic tube. This assembly has a slip surface between the tube and 
the ball seal. When the tube slides in and out of the seal due to thermal 
expansion, it does not pull the ball seal against the inner surface of the 
inner tube sheet tile or the ceramic tube. This results in a situation in 
which, when the tube sheets move during operation, the ball seals do not 
maintain their compression and leakage occurs. Further, without an 
attachment to the ceramic tube, the seal cannot move, either in a linear 
direction, or a lateral direction, both of which are requirements in a 
good sealing system. Thus, there is needed a decidedly different heat 
exchanger to overcome the problems set forth above. 
THE INVENTION 
The invention disclosed and claimed herein deals with low to medium 
pressure, high temperature, all ceramic, air-to-air, indirect heat 
exchangers, novel ball joints and connecting slip ring collars for ceramic 
tubes that are useful in such heat exchangers, and systems comprising 
several heat exchangers or systems comprising heat exchangers that are 
fabricated such that they provide more efficient heat exchangers then has 
been possible heretofore. 
More specifically, this invention deals in one embodiment with a low to 
medium pressure, high temperature, all-ceramic, air-to-air, indirect heat 
exchanger which comprises in combination (A) a novel, all-ceramic ball 
joint, said ball joint comprising a spherical body having an outer surface 
and an inner surface and having a near side and a tube side. The near side 
has a truncated face to form a flat surface on the near side. The 
spherical body has a first opening through it from the near side through 
the tube side. The tube side has a truncated face to form a flat surface 
on the tube side and the tube side has a second opening in alignment with 
and larger than the first opening to form a shoulder within the second 
opening which accommodates a ceramic tube in it. The outer surface of the 
spherical body is covered with a smooth, refractory ceramified, frit 
glaze. 
(B) is an assembly comprising: (i) a tile; (ii) a closure ring; (iii) a 
plug, and (iv), at least one friable, crushable, alignment ring, wherein 
parts (i), (ii), and (iii) are ceramic bodies and wherein part (i) is a 
tile which forms part of a tube sheet. The tile has at least one round 
opening through it and has a plug side and a tube side and an inside 
surface. The tile has a discontinuous annular ring on the interior surface 
formed by the opening and near the plug side. 
Part (ii) is a closure ring having a length essentially one-half of the 
width of the tile and it has a top surface, a bottom surface, a near end 
and a distal end wherein the top surface is bonded to the interior surface 
of the tile near the tube side of the tile such that the distal end of 
(ii) is essentially vertically aligned with the tube side of the tile. The 
part (ii) has an arcuate notch in the near end and in the interior 
surface. The arcuate notch is covered with a coating of a smooth, 
refractory ceramified frit glaze and mates with the spherical body outer 
surface. 
Part (iii) is a plug. The plug has a plug top surface, a plug interior 
surface, a plug near end, a plug distal end, an opening through its 
center, and a horizontal midpoint, there is a discontinuous channel in the 
plug top surface to accommodate the discontinuous annular ring of the 
tile. The plug has a second arcuate notch in the plug near end and in the 
plug interior surface. The second arcuate notch is covered with a smooth, 
refractory ceramified frit glaze and mates with the spherical body outer 
surface. The plug has a curved face at its distal end which begins at the 
plug interior surface and near the horizontal midpoint and ends at the 
plug distal end near the top surface. The closure ring and the plug 
provide a channelled opening between them at their near ends. 
Part (iv) is a friable, crushable, alignment ring. The alignment ring is 
located in the channelled opening and Part C. are multiple ceramic heat 
exchanger tubes fitted with B. as set forth above. 
Another embodiment of this invention is a heat exchanger as set forth just 
above, wherein, in addition, the ceramic tubes are fitted with B. on one 
end, and their opposite ends are connected together in an end to end 
configuration with a like-fitted ceramic tube using an all-ceramic 
connecting slip ring collar. 
The ceramic tubes have an outside surface and the connecting slip ring 
collar has an outside surface and an inside surface. The connecting slip 
ring collar has an inside diameter such that the inside surface of the 
connecting slip ring collar is adaptable to and conforms with the outside 
surfaces of the ceramic tubes such that the connecting slip ring collar is 
closely, slidably mated with each of the ceramic tubes and supports such 
tubes. There is located within the connecting slip ring collar, and 
situated between the ends of the ceramic tubes, a friable, crushable, 
ceramifiable ring. 
Still another embodiment of this invention is a novel, allceramic ball 
joint, said ball joint comprising a spherical body having an outer surface 
and an inner surface and having a near side and a tube side. The near side 
has a truncated face to form a flat surface on the near side. The 
spherical body has a first opening through it from the near side through 
the tube side and the tube side has a truncated face to form a flat 
surface on the tube side. The tube side has a second opening in alignment 
with and larger than the first opening to form a shoulder within the 
second opening to accommodate a ceramic tube in it. The outer surface of 
the spherical body is covered with a smooth, refractory ceramified, frit 
glaze. 
Yet another embodiment of this invention is a novel allceramic ball joint 
assembly comprising the ball joint discussed supra in combination with (i) 
a tile; (ii) a closure ring; (iii) a plug, and (iv) at least one friable, 
crushable, alignment ring. 
Further embodiments of this invention are a novel closure ring, a novel 
plug, and a novel alignment ring, all of which are useful in an 
all-ceramic ball joint assembly used in a unitary, ceramic tile.

DETAILED DESCRIPTION OF THE DRAWINGS 
Turning now to the Figures, there is shown in FIG. 1 a full top view of a 
portion of one of the heat exchangers 1 of this invention with the top 
shell wall removed, wherein there is shown generally, an inlet plenum 2 
for introducing forced air into the tube end of the heat exchanger and an 
outlet plenum 3 for removing the forced air from the heat exchanger 1, 
tube sheets 4 and 4' which support the ends 9 (shown in the FIG. 3) of the 
ceramic tubes 5. There is also shown the two sides 6 and 6' of the shell 
7, which make up the outer walls of the housing of the heat exchanger 1. 
Also shown in FIG. 1 are the connections 8 which are non-heat conductive 
attachments of the shell 7 to the tube sheet and which prevent the shell 7 
from obtaining high heat by conduction. These connections 8 consist of 
constructing a channel frame about six inches from the main shell, in 
conjunction with the use of high alumina, dense refractory tile between 
the channel frame and the edge of the conventional tube sheet. In this 
manner, width is added to the tube sheet. The outer construction is then 
finished with a low K-factor refractory. The combination of the additional 
thickness owing to the extension of the tube sheet, with the low K-factor 
reduces the heat temperature sufficiently to permit a metal shell, strong 
enough to hold the tube sheet in place. Thus, no air cooling is required 
in such a heat exchanger as there is in prior art heat exchangers. It 
should be noted that the total housing and the plenums for controlling the 
hot gases are not shown in these Figures as they do not lend themselves to 
a clear description of the essence of this invention. This Figure of the 
invention shows the most fundamental embodiment of the heat exchanger 1. 
A portion of a more complex, but highly efficient heat exchanger 10 is 
shown in FIG. 2. Thus, there is shown the inlet plenum 2 for carrying 
forced clean air into the ceramic tubes 5. It should be noted that the 
outlet plenum 3 for removing the heated, forced clean air is located 
adjacent the inlet plenum 2, the reason for which will be abundantly clear 
upon further discussion infra. There is also shown the tube sheets 4 and 
4', the ceramic tubes 5, the two sides 6 and 6' and the connectors 8. 
In addition, the heat exchanger 10 also has an extra set of ceramic tubes 
designated 11, which are essentially equivalent to ceramic tubes 5, but 
are designated 11 in order to help clarify this invention, and a baffle 
wall 12, which is not a tube sheet. Finally, the heat exchanger 10 has a 
capping plenum 13 at the end of the heat exchanger 10 opposite the inlet 
plenum 2 and outlet plenum 3 to turn the hot clean air from the first set 
of ceramic tubes on the inlet side to the second set of ceramic tubes on 
the outlet side. It should be noted for those skilled in the art that the 
heat exchangers of this invention can handle the reverse order of passage 
of the air and gas. Thus, with reference to FIG. 2, where it is indicated 
"Air" on the right hand plenum of that Figure, the gas flow can be moved 
through these plenums, and the air can be moved according to the flow 
illustrated by "GAS FLOW" in FIG. 2 without creating excessive 
deterioration of the heat exchanger. 
The baffle wall 12 is designed to support the ends of the ceramic tubes 5 
(and 11 where used), within a connecting slip ring 60, shown in FIGS. 8, 
9, and 10 in more detail, but not visible in FIG. 2. The significance of 
the connecting slip ring 60 becomes more apparent when reference is made 
to FIG. 10, wherein an enlarged view of the connecting slip ring 60 is 
shown. This slip ring becomes important because the ceramic tubes being 
held by the connecting slip ring 60 can be removed when the connecting 
slip ring 60 is advanced on the ceramic tube 5 such that the connecting 
slip ring 60 and the ceramic tube 5 can be lifted out of alignment with 
the ceramic tube 11, and moreover, the assembly created by the connecting 
slip ring 60 and the ceramic tube 5 can be lifted from the baffle wall 12 
for removal of the ceramic tube 5 for replacement or repair. This 
construction allows for the tubes (and the heat exchanger) to be repaired 
or maintained without having to remove the plugs from the tube sheet 4, 
that is, the heat exchanger can be repaired from the interior of the heat 
exchanger without having to deal with the tube sheet 4. Thus, it is 
contemplated within the scope of this invention to provide a tube sheet 
which does not require the plugs 21 as it would not necessarily require 
that the ceramic tubes 5 need to be removed from the heat exchanger 
through the plug openings. The baffle wall 12 also helps define the zones 
for the hot gases that are passed over the ceramic tubes 5, it being noted 
that the hot gases move essentially in a perpendicular direction to the 
flow of the clean air through the ceramic tubes 5. It should be noted by 
those skilled in the art that the ceramic tubes of this invention are 
manufactured by standard slip cast or extruded methods, and do not require 
internal or external machining or special end dressing of the ceramic tube 
diameter as is required in the prior art ceramic tubes. 
Turning now to FIG. 3, there is shown an enlarged view in perspective of a 
portion of the ceramic tube arrangement including a tube sheet 4', a 
baffle wall 12, and the ceramic tubes 11 of the heat exchanger 10 of FIG. 
2. 
As noted above, the ceramic tubes 11 are supported and held by their ends 9 
(shown in FIG. 3) in the tube sheet 4' (shown at the left end of the 
Figure) with a novel ball joint assembly which will be discussed in detail 
infra. The opposite ends 15 of the ceramic tubes 11 (shown in FIG. 8) are 
inserted into and supported by the baffle wall 12 by the use of a novel 
connecting slip ring 60, shown in detail in FIG. 8. Thus, the ceramic 
tubes 11, and the ceramic tubes 5 (FIG. 2) are aligned end to end within 
the connecting slip ring 60 within the baffle wall 12, the detail of which 
can be found in the description below dealing with the connecting slip 
ring 60 and also in FIGS. 9 and 10. 
Also shown in the front surface 16 of the tube sheet 4, are the plugs 21 
which also are discussed in detail infra. 
Moving on to the consideration of FIG. 5, there is shown a portion of a 
tube sheet 4'. Since in most respects the tube sheets, including tube 
sheets 4 and 4' are essentially the same, the description of tube sheet 4' 
can suffice to describe all tube sheets used in the fabrication of the low 
to medium pressure heat exchangers of this invention. For purposes of this 
discussion, and with reference to FIG. 4, there is shown a novel tube tile 
17. It should be understood that the tube tiles 17 of this invention are 
novel because they have a novel, highly useful configuration and this 
allows for the low cost manufacturing of such tiles. The tube tiles 17 of 
the instant invention are made in a unitary construction by pressing the 
tube tile in a ram press without making fine threads, it being one object 
of this invention to eliminate the fine threads which are costly to cast 
into the piece. However, it should be noted that the tube tiles of this 
invention retain all of the plug locking potential that is required to 
hold the low to medium pressures of the heat exchangers of this invention. 
The prior art tube tiles have to be side rammed to get the fine threads 
into the surface. Further, the tube tiles of this invention, used with a 
rammed plug, and because of their unitary construction are stronger than 
the prior art tiles. Prior art tiles that use a cast plug and more shapes 
per assembly are of a two piece construction, that is, they are made in 
two halves to accommodate the aforementioned casting of the fine threads, 
and then they are cemented together to make a whole tube tile generally 
containing either one or two holes for the ceramic tubes. The fact that 
they have to be cemented together creates an additional problem because of 
the microcracking during operation of the heat exchanger, that takes place 
in the cement joints that hold the tube tile together. Such microcracking 
creates a site for leakage. The tube tiles of this invention are a nominal 
size of two inches thick by eight inches long, but can vary from this size 
within reason. 
Thus, the tube tiles 17 of this invention are unitary in construction and 
have one or more holes 18 through them. The number of holes 18 will depend 
on the desired construction of the particular heat exchanger that one 
desires to fabricate, but the tube tiles 17 have been fabricated by the 
inventor herein with up to seven holes 18 in a single tube tile 17. Most 
importantly, one can make a single tile with up to seven tube holes. This 
reduces the number of mortar joints by about 90%. That reduction, in turn, 
reduces leakage and cost of assembly. In addition, the holes can be held 
to a more accurate tolerance when there is not a mortar seam on each side. 
Shown in FIG. 4 is a tube tile 17 having five holes 18. It should be noted 
that the holes 18 are press fabricated with tabs 19 which are located on 
the interior surface 20 of the holes 18 such that they form a 
discontinuous annular ring within the hole 18 and on the interior surface 
20. The discontinuous annular ring configuration is one-half of a Luer 
Lock.RTM. mechanism for locking a plug 21 (shown in FIGS. 6 and 7) into 
the hole 18. The tabs 19 are located in the hole 18 such that they act as 
a coarse threaded configuration which allows the plug 21 to be locked into 
the hole 18, but also to allow for a slight tightening of the plug 21 into 
the hole 18 without having to resort to fine threads such as are used in 
prior art tube tiles. The pressed tube tiles and plugs of the instant 
invention have five times the crush strength of prior art castable tube 
tiles and plugs. The tube tiles 17, along with other configurations of the 
tube tiles 17 are used to fabricate tube sheets 4 and 4'. Thus, turning 
again to FIG. 5, there is shown an arrangement of tube tiles 17 to form a 
tube sheet such as 4 or 4' of this invention. It should be noted by those 
skilled in the art that no attempt was made in FIG. 5 to show a fully 
completed tube sheet such as 4 or 4', but rather to show how the tube 
tiles 17 can be arranged with regard to each other. Note for example the 
tiles 22 and 23 which are spacer tiles and are used to help configure the 
tube sheet 4 or 4'. It is desired that the tube sheets 4 and 4' have 
essentially a rectangular configuration, but square configurations can be 
used, and thus it is necessary that other configurations of the tube tile, 
some with holes 18 and some without, are needed to construct such tube 
sheets. Further, eventhough the tube tiles 17 are shown in one 
configuration does not mean that the invention is limited to just that 
configuration. It is contemplated within the scope of this invention to 
combine various configurations of tube tiles 17 to arrive at tube sheets 
useful in this invention. 
It should also be noted that the tube tiles such as 17, 22 and 23 are 
cemented together at cement joints 24 to form the tube sheets such as 4 
and 4'. By virtue of the use of the unique tube tiles 17 of this 
invention, the tube sheets such as 4 and 4' have far less cemented joints 
24, and therefore, the tube sheets such as 4 and 4' have significantly 
less leakage, in some instances, the inventor herein has observed up to 
ninety percent less leakage with such an arrangement. 
Turning now to FIG. 6, and the novel ball joint assembly 25 of this 
invention, there is shown a cross-section of a portion of the tube sheet 
4', of FIG. 3, through the points 200--200. 
With reference to FIG. 6, there is shown a tube tile 17 of this invention 
which is holding the ball joint assembly 25. The ball joint assembly 25 is 
comprised of a spherical body 24 having an outer surface 26 and an inner 
surface 27 and a near side 28, and a tube side 29. The near side 28 has a 
truncated face 30 to form a flat surface. The spherical body 24 has a 
first opening 31 through it from the near side 28, which extends through 
the tube side 29. The tube side 29 also has a truncated face 32 to form a 
flat surface on the tube side 29. The tube side 29 has a second opening 33 
in alignment with and larger than the first opening 32 to form a shoulder 
34 within the second opening 33 to accommodate a ceramic tube 5 therein. 
In addition, the outer surface 26 of the spherical body 24 has adhered-to 
and is covered with a smooth, refractory ceramified, frit glaze 55. 
Also with reference to FIG. 6, there is shown a closure ring 35 wherein the 
closure ring 35 has a width essentially one-half of the length of the tube 
tile 17. The tube tile 17 has a bottom surface 36, a plug side 37, and a 
tube side 38. The closure ring 35 has a top surface 39, a bottom surface 
40, a near end 41, and a distal end 42 and the inside diameter of the 
opening of the ring approximates the outside diameter of the ceramic tubes 
5 that are used in the fabrication of the heat exchanger. The top surface 
39 is intended to be cemented to the bottom surface 36 of the tube tile 
17, near the tube side 29 of the tube tile 17 such that the distal end 42 
of the closure ring 35 is essentially vertically aligned with the tube 
side 29 of the tube tile 17. The cemented interfaces are shown at 54. The 
closure ring 35 has an arcuate notch 43 in the near end 41 and at the 
bottom surface 40. The arcuate notch 43 is covered with, and has adhered 
thereto, a smooth, refractory ceramified frit glaze 44 intended to be 
mated with the outer surface 26 of the spherical body 24 contained in the 
ball joint 25. 
Also associated with the ball joint assembly 25 is a plug 21, shown in FIG. 
6 which is also shown in a full front view in FIG. 7. 
The plug 21 has a top surface 45, a bottom surface 46, a near end 47, a 
distal end 48, and a vertical midpoint shown as line 300--300. The plug 21 
has a discontinuous annular channel 49 in its top surface 45 to 
accommodate the discontinuous annular ring formed by the tabs 19 of the 
tube tile 17. The plug 21 has a second arcuate notch 50 in the near end 47 
and at the bottom surface 46, the second arcuate notch 50 having 
adhered-to and being coated with a refractory ceramified frit glaze 51. 
This coated arcuate notch 50 is intended to mate with the all-ceramic, 
ball joint outer surface 26. The plug 21 has a curved face at its distal 
end 48 which begins at the bottom surface 46 and near the vertical 
midpoint shown by line 300--300 and ends at the distal end 48 near the top 
surface 45. The plug 21 has an opening 56 through it which has an inside 
diameter approximating the inside diameter of the spherical body 24. As 
indicated supra, the plugs of this invention are obtained by ram pressing 
rather than by casting. 
Situated in the interfacial space between the closure ring 35 and the plug 
21 is at least one alignment ring 52, which alignment ring 52 is 
fabricated from a friable, crushable ceramifiable ceramic material. This 
alignment ring 52 is ceramified during the first heat up of the heat 
exchanger. 
Shown in FIG. 7 is a full front view of a plug 21 according to this 
invention, showing the indentions 53 that are fabricated in the face of 
the plug 21, in order to be able to grip the plug 21 for turning in and 
out of the tube tile 17 during repair, maintenance, assembling and 
disassembling. The indentions 53 can have any configuration that will 
allow a wrench, or some similar instrument to be inserted for the purpose 
of turning plug 21 in either direction. 
With regard to the novel expansion assembly of the invention and turning 
now to FIGS. 8 and 9, there is shown in FIG. 8, a cross sectional view 
through line 100--100 of FIG. 3, showing a portion of the baffle wall 12 
and the ceramic pipes 5 and 11 and the novel connector slip ring 60 along 
with a friable, crushable, ceramic gasket ring 58. FIG. 9 is a cross 
sectional side view of a larger portion of the baffle wall 12 through line 
400--400 showing several connector slip rings 60 cemented in place at 
cement lines 57. 
FIG. 10 is another embodiment of the configuration of the connector slip 
ring 60 mounting which is outside of the baffle wall 12, but is still 
supported by the baffle wall 12. 
Finally, with reference to FIG. 11, the inventor contemplates that the 
ceramic tubes 5 of this invention can contain a re-radiator bar 59 in 
those cases where it is required to maintain heat in the system. 
Re-radiator bars 59 are well-known to those skilled in the art and 
detailed information is not required herein regarding their composition, 
use and their assembly in the ceramic tubes. A lip 62 is shown in phantom 
in FIG. 11, which lip serves to prevent the re-radiator bar from moving 
out of the tube. 
Now, bringing all of these parts together so that those skilled in the art 
can appreciate the high level of novelty of this invention it should be 
noted that in the fabrication of the heat exchanger, tube tiles 17 are 
cemented together to form the desired configuration to accommodate the 
ceramic tubes 5, generally in a round, square or rectangular 
configuration. 
As indicated supra, the fabrication of the tube sheets 4' should not be 
lightly undertaken, as tube sheets 4' fabricated without paying attention 
to detail can result in extensive leakage. The tube tiles 17 of this 
invention allows fabrication of tube sheets in just about any 
configuration by using tube tiles 17 that can have up to seven holes in 
them. Prior art tube tiles usually contained only one or two holes in 
them, with a full mortar joint through every thread, which means that tube 
sheets had a lot of mortar joints in them, which joints microcrack during 
use, and which thus, leads to extensive leakage through the tube sheet. 
Since the tube tiles 17 of this invention provide many holes 18, with no 
mortar joints through the threads, and since the tube tiles 17 are of a 
unitary construction, less mortar joints need be used in the construction 
of the tube sheets 4', and hence, there is significantly less leakage. 
This fact is especially crucial when the heat exchangers of this invention 
are subjected to high temperature and medium pressures. Moreover, the tube 
tiles 17 of this invention lead to less costly construction of the tube 
sheets. 
Ball joint assemblies 25 are then used to construct the tube sheets 4', 
that is, the bundle of ceramic tubes 5 that will constitute the heat 
exchanging portion of the heat exchanger, by cementing, using mortar 61, 
one end of a ceramic tube 5 into the tube side of a spherical body 24 of 
the ball joint assembly 25. In each of the holes 18 of the tube sheet 4, a 
closure ring 35 is inserted such that its distal end 42 is in vertical 
alignment with the tube side 38 of the tube tile 17. The closure ring 35 
is cemented at its top surface 39 to the interior surface 27 of the tube 
tile 17. The end 15 of the ceramic tube 5 which does not have the 
spherical body 24 cemented on it is passed through the center of the 
closure ring 35 and the tube side 29 of the spherical body 24 is drawn up 
against the arcuate notch 43 in the interior surface 40 of the closure 
ring 35. The alignment ring 52 is then placed up against the closure ring 
35 near end 41, and around the spherical body 24, the plug 21 is inserted 
into the opening 18 in the plug side 37 of the tube tile 17, and the plug 
21 is turned to compress the alignment ring 52, and seat and lock the plug 
21 into place. 
It should be noted that the interior surface 40 of the closure ring 35 is 
beveled in a line from near its near end 41 to the distal end 42 thereof. 
This angle of bevel is on the order of about 2.degree. to about 6.degree. 
from a plane formed by the outside surface of the ceramic tube 5 placed 
therein, the actual angle being determined by the size of the spherical 
body 24 and the length of the ceramic pipe 5, from its contact with the 
spherical body 24 to the distal end 42 of the closure ring. The purpose of 
this bevel is to allow for the ceramic pipe 5 to move out of alignment and 
swivel to a limited degree during operation, as the ceramic parts of the 
assembly expand due to heating. This slight swivel effect allows a good 
seal to be retained on the ceramic tube 5, while preventing a fracture of 
the ceramic pipe 5 due to shear stress on it. 
Because the closure ring 35 is cemented to the interior of the tube tile 
17, and because the ceramic tube 5 is cemented to the spherical body 24, 
the ceramic tube 5 cannot move out of the tube sheet 4', but can move to 
alleviate stress on the ceramic tube 5, all the while keeping a positive 
seal on the closure ring 35 to prevent leakage. 
As noted above, the face of the spherical body 24 and the faces of the 
arcuate notches 43 and 50 in the interior surfaces of the closure ring 35 
and the plug 21 are coated with a smooth, refractory ceramified glaze 
which gives a good positive seal, but allows for the smooth rotation of 
the spherical body 24 within the notches 43 and 50 during heating up and 
cooling down of the apparatus. Such a coating is durable at the high 
temperatures used in the heat exchanger and thus, replacement of gaskets 
normally used in this part are not required resulting in less down time 
for the heat exchanger. 
Dense, high temperature refractory is difficult and expensive to machine. 
The refractory frit ceramified glaze gives a machined surface to 
conventionally manufactured ceramic shapes. 
The discontinuous annular ring on the interior of the tube tile 17 works in 
combination with the discontinuous annular channel 49 in the outside 
surface of the plug 21 to provide a Luer Lock.RTM. type of mechanism that 
draws the plug 21 in to compress the friable, crushable alignment ring 52 
between the near ends 41 and 47 of the closure ring 35 and plug 21. This 
alignment ring 52 not only allows for good alignment of the ceramic parts, 
but it also acts as a gasket between the parts so as to help reduce 
leakage through the tube tiles 17 and into the interior of the heat 
exchanger. Furthermore, if some maintenance has to be undertaken with a 
ceramic tube 5, the removal of the plug 21 and the ceramic tube 5 may not 
require another alignment ring 52, as the alignment ring 52 is crushed in 
the process of expansion during heating, and the alignment ring 52 takes 
on the configuration of the parts and allows for the parts to be 
conveniently re-assembled with the expectation that the parts will 
continue to provide a good, positive seal against leakage. Such 
flexibility in the use of material drives down the cost of the operation 
of such a unit. 
If one desires to fabricate just a one pass unit, or a small unit as shown 
in FIG. 1, then the opposite end of the ceramic tube 5 is treated just as 
is the first end. The heat exchanger then can be provided with the 
appropriate housing, plenums, fans, and the like to operate the unit. 
However, if one desires to increase the efficiency of such a unit and 
provide lower cost operation at high temperatures and low to medium 
pressures, then one would need to construct a unit based on that shown in 
either FIG. 2 or FIG. 12 (unit 600), wherein the reference numbers have 
the same meanings as in the other Figures. 
The heat exchanger 10 shown in that Figure is even more novel in that there 
is used a baffle wall 12 and a novel means of allowing for expansion of 
the ceramic tubes 5 in the heat exchanger that is unknown to those skilled 
in the art. 
The unit is constructed in a fashion similar to that described above, but, 
however, after the first tube sheet 4' is constructed and the novel ball 
assemblies 25 are in place, a second tube sheet 4 is constructed 
essentially identically to the first tube sheet 4' and then the two tube 
sheet assemblies are matched end to end on the ends that do not have any 
ball joint assembly 25. These matching ends are secured by inserting 
connector slip rings 60 into the holes 18 of a baffle 12 and then 
inserting the ends 15 of the ceramic tubes 5 and 11 into the connector 
slip rings 60 such that they do not meet each other inside the connector 
slip rings 60. Prior to insertion of the rings, there is inserted into the 
connector slip rings 60, an alignment ring 58, similar to that used in the 
novel ball joint assembly 25. The connector slip rings 60 are designed 
such that they mate with the interior surface 20 of the holes 18 in the 
baffle wall 12, and are cemented therein. The connector slip rings 60 have 
an inside diameter such that the ceramic tubes 5 and 11 will easily slip 
inside them, and upon heating, the ceramic tubes 5 and 11 expand to mate 
with the inside surface 20 of the connector slip rings 60, but will be 
slidable therein. Further, this design of the connector slip rings 60 
through the baffle wall 12 allows for the linear expansion of the ceramic 
tubes 5 and 11, which expansion will push the ceramic tubes 5 and 11 into 
the connector slip rings 60, and crush the alignment ring 58 therein. The 
ceramic tubes 5 and 11 thus will not expand greatly towards the ends that 
are secured by the novel ball joint assemblies 25 and by this means, a 
positive seal is maintained on the tube sheets 4 and 4', and the connector 
slip ring assemblies 60, further reducing the possibility of leakage in 
the system. In this type of design, all of the take-up for ceramic tube 
expansion is now in the connector slip ring 60. This means the seal in the 
tube sheets 4 and 4' only have to allow for tube to tube sheet movement 
and does not have to allow for tube expansion in length. As the tube 
expands, it will grow towards the connector slip ring 60. This means the 
leakage on the pan seal, if any will be constant regardless of 
temperature. 
Since the prior art ball joint device has a sliding ceramic tube inside the 
ball, the tube will not pull the ball against the seal and therefore, 
there is not a positive seal and heat exchangers provided with the prior 
ball joint assembly will not have the reduced leakage of the instant 
invention. 
It should be noted at this point, for those skilled in the art, that a 
further embodiment of this aspect of the invention such as shown in FIG. 
10 can be utilized. This embodiment shows the connector slip ring 60 being 
supported by the baffle wall 12, but its placement is on the outside of 
the wall such that the assembly is on the cooler side of the baffle wall 
12 as opposed to the hotter side of the baffle wall 12. The connector slip 
ring 60 is cemented to the baffle wall 12 only at 57, while the connector 
slip ring 60 is not cemented any place else and this allows the connector 
slip ring 60 to be held tightly to the baffle wall 12 for support in the 
coldest side, thereby reducing the deterioration of the parts on that 
side. By putting the ceramic tubes 5 and 11 in line in this manner and 
connecting the "coldest" tube to the "hottest" tube at the inlet and the 
outlet, respectively, and the medium temperature tubes connected to each 
other, one ends up with the opposing tube sheets 4 and 4' staying vertical 
as they expand. 
It should be noted that the use of the connector slip rings 60 allows the 
replacement of one ceramic tube 5 or 11 without requiring the replacement 
of the companion connecting tube. 
In prior art designs, the top row of ceramic tubes are colder than the 
bottom row of ceramic tube, so the tube sheets have a tendency to move 
apart at the bottom and stay closer together at the top. This created a 
tee pee effect and increased leakage. 
Further, by connecting the ceramic tubes in the center with a connector 
slip ring that is cemented to one tube and free sliding at the other end 
and connecting the tubes in a line, a two-pass exchanger that has four 
tube sheets becomes a two-pass exchanger with two tube sheets and the 
center wall, which is the baffle wall 12 acts as a baffle and, since it is 
in the heat exchanger proper, it is not subject to leakage from the air 
side of the heat exchanger. 
It should be understood by those skilled in the art that several such heat 
exchangers can be hooked together to form a system.