Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates generally to heat ex-
changers and, more particularly, to heat exchangers for boilers,
water coolers, air conditioners, and other equipments for the
transmission or reception of heat.
As is well known, a heat exchanger generally includes
means whereby two fluids separated by a wall and having differ-
ent temperatures are caused to transfer heat from one of thefluids to the other. A typical or conventional heat exchanger
includes one or more pipes, tubes, or other conduits through
which a fluid, such as water, flows and is intended to give up
to or receive heat from a second fluid. Each such conduit may
have, affixed to its outer surface, a plurality of fins, ribs,
pins or other hardware usually provided on or near the outer
surface thereof, so as to improve and increase the heat trans-
fer capability of the conduit and thereby improve the relative
efficiency of the heat transmission to or from the fluid flow-
ing through the conduit. ~b1e~
- 1-- ~,,~ ~.
f
`''`','.`',''' .''"~,.''.',' '"" " ` ~ ; ;'': ' ' ' '
1(~4~95 -
Heat exchangers usually include, in additiion to the
conduit or conduits which carry a fluid, such as water to be ~
heated or to give up heat, a second or gaseous medium which may ;
be derived from an adjacent burner or from a refrigerator or .
from any other source supplying the gaseous medium which is to
flow around the conduit or conduits, so as to change the temp-
erature of the fluid flowing through the conduits. A prior
typical boiler, for example, having such a heat exchanger for ;~
use in a residential or commercial building, even a small resi- ~ ~
dential building or an apartment of a large building, would be -
. .: .
relatively so large-and bulky that it would require considerable j;
space to house and shelter the heat exchanger. The heat ex- ;
changer would also be so complex that it would usually require
skilled manpower and considerable time to manufacture the struc~
ture and necessarily its costs would be relatively high. The
efficiency of transmission of heat between a gaseous medium and
a liquid medium in such a structure would be so poor that the
cost of operation would be quite large. These are some of the
adverse factors that suggest the serious problems facing indus- -`
try generally in meeting the needs for low cost residential and
commercial buildings requiring heat exchangers for boilers and
other heating or cooling structures.
In accordance with the present invention, a new form ;
of heat exchanger is provided, along with the necessary appur-
tenances required for building, for example, a boiler, the heat
exchanger being suitable for a miniature type of boiler system,
that is, a boiler structure much smaller than conventional -
boiler structures now made and sold for residential and commer-
cial establishments. The heat exchanger structure, and the
boiler systems of which it is a part, will be relatively easy
-2- `
446i~5
to manufacture, small in size, light in weight, relatively free
of serious or costly maintenance problems, and easily incorpor-
ated into small or mLniature boiler systems, and, if desired,
into larger boiler systems, whether ~or use in small individu-
alized city apartments or in large or small residential or
commercial buildings. `~
In general, the heat exchanger of this invention may
include, for example, a unitary cylindrical structure compris-
ing a plurality of circumferentially arranged parallel conduits
through which fluid, such as water, may flow and, between the
:. .,
conduits, there will be a matrix structure consisting of a
plurality of separate and independent matrices each composed
essentially of a plurality of pellets, preferably made of metal,
integrally bonded to each other and to the side walls of the
two adjacent conduits, so as to form the unitary substantially ,~
. . .
cylindrical structure. In the heat exchanger of this invention,
no one of the matrices of pellets will be positioned-on the
lower surface, nor on the upper surface, of the several parallel
circumferential conduits. In other words, none of the pellets
will~be positioned within the cylindrical tangential periphery
i i . :
; defining the innermost points of the several parallel conduits,
nor will any of the pellets of any matrix be positioned radial- ~ `
~ , . ': `.
ly beyond the cylindrical surface defining the outermost points
of the several parallel conduits. Thus, all of the pellets of ,~;
all of the æeveral matrices will be positioned between the two
designated tangential cylindrical peripheries defining the
uppermost and lowermost points of the several conduits. Hence,
the heat exchanger will comprisean hour-glass-shaped matrix ~ `;
structure in which each of the several matrices will be posi- -~
tioned between two adjacent parallel conduits. Such a composite
-3-
. ~ .
~ , , .
4 4 ~i 9 5 r
heat exchanger structure is easily and conveniently manufac-
tured and assembled within a cylindrical casing for use in a
boiler or other heat transfer apparatus.
In accordance with the present invention, a surface
combustion burner, preferably a pressurized surface combustion ~;
burner, may be positioned within the central or axial space
. . .
formed by the belt-shaped matrix structure above noted, which -i;-
includes the several matrices and the corresponding interspersed
.f. . ~ .
parallel conduits, so that heat generated by the surface com-
bustion burner may deliver heated gases, at relatively high '
temperatures and suitable pressure, directly againæt the inner
or under surfaces of the several conduits and also, simultane-
ously, directly against the several matrices of pel1ets. Some
; of the gaseous heat from the burner, upon striking the under
surfaces of the several parallel conduits, will deliver heat
efficiently to the fluid within the conduits. Some of the gas-
eous heat derived from the burner will, at the same time, be
delivered to the under surfaces of the several matrices of
pellets, 80 that the pellets will be heated and the heat trans- ';~
mitted to the pellets will be conducted to the sidewalls of the
parallel conduits for simultaneously heating the fluid flowing r
through the conduits. Moreover, the heated gases which are
deflected from the under surfaces of the several parallel con-
duits will necessarily traverse paths extending through the
.~ , . . .
~ several matrices of pellets to further aid in raising the tem- -
; .: -
perature of the pellets and of the fluid within the conduits.
Thus, the heat of the gaseous combustion products from the l -
~ burner will simultaneously and jointly attack the sides of the `-
parallel conduits along several different fronts, all cooperat-
ing to raise the temperature of the fluid flowing therethrough.
_4_
The gases, after traversing the paths of the several matrices,
may be discharged through a chimney or any other convenient
adjacent outlet which need not have, and need not produce, a
substantiàl draft.
The matrix structure above referred to, which may be
composed of a plurality of independent matrices as indicated,
each embodying a plurality of pellets bound to each other and
to the parallel adjacent conduits, will form what may be des-
cribed as a circularly cylindrical belt. The spacings of the
pellets of each matrix are randomly arranged and do not require
any predetermined formation. The spacings between the pellets
~ill render each matrix porous with respect to the heated gases ~`
supplied by the surface ~ombustion burner, but notwithstanding `~
these inherent spacings, the pellets will freely conduct heat
from one pellet to another and then to the walls of the adjacent
; conduits and, therefore, to the fluid transmitted through the
conduits. Because of the random spacings of the pell~ts and
their relative sizes, the combustion gases may rather freely
and efficiently traverse the various matrices so that a good
and predetermined rate of gaseous transmission f~om the burner
will be maintained through the circularly cylindrical belt -
structure. By means of this structure, a very high proportion
of the heat within the generated combustion gases will be trans~
lated into heat in the fluid continuously flowing through the
conduits to raise the temperature of the moving fluid to the ~;~
desired temperature. The pellets of the several matrices will
be fairly large so that only a few, and not too many, pellets ;~
will necessarily be interposed between the adjacent parallel
conduits. The random spacings of the pellets will allow the
free and efficient flow of the combustion gases through the
-5-
~, 1~44~i~95
matrix, thereby to dissipate heat to the several pellets which
,, . ,~ ,
will conduct the heat to the walls of the adjacent conduits.
The pellets are preferably constructed of the correct dimen-
sions, that is, the correct range of diameters if the pellet#
.;:, . .
are spheres, so that their random spacings will provide the
porous and optically transparent linkage between the several `~ ;
conduits for the conduction of heat to the fluid in the con-
duits. No part of any matrix of pellets is positioned on the
inner side of the inner cylindrical tangential surface of the
parallel conduits. Nor is any part of any matrix of pellets
positioned on the outerside of the outer cylindrical tangential
surface defining the parallel conduits. This results in a
considerable saving not only in the number of pellets used, but
also in the cost of the pellets and in the cost of the matrix.
At the same time, the combustion gases make direct contact with
the underside of the several parallel conduits so as to direct-
ly raise the temperature of the fluid travelling through the
conduits.
,.
Because of the spacings between the pellets of the
, :, .,
matrix, the matrix will be porous to the heated gases supplied
by the burner and porous also to any other rays which are nec- ;
essar~ly generated by the gases burned by the pressurized bur-
~ . ...
ner. In other words, the spacings of the pellets yield the
correct fluid velocities in the form of heated gases through
the several matrices. Some paths through each matrix will be ~ -
straight-line or uninterrupted 80 as to yield a desired low
pressure loss.
Thus, as already suggested, the heated and pressured
gases supplied by the surface combustion burner will direc~ly
and indirectly impinge upon the under surfaces of the several
-6-
;
1~4~95
parallel conduits so that a high proportion of the heat of the
gaseous products of combustion will be supplied against the
walls of the conduits for rapidly heating the fluid flowing
through the conduits. As already also suggested, the heated
gases reflected by the conduits must necessarily impinge upon
the matrix of pellets and hence the reflected gases will con-
duct heat to the side walls of the conduits to contribute im-
portantly to the heat supplied to the fluid within the conduit -
walls. A good part of the heated gases will also directly strike
the matrix of pellets independently of the reflected heat, to
further increase the supply of heat to the fluid traversing the
several parallel conduits. The several paths of the heated
gases in supplying heat, directly or indirectly after reflection, ;
to the fluid of the conduits, join together to quickly and
efficiently raise the temperature of the fluid. This process is
carried out ~uickly and, therefore, in a rather limited space. ~ ~
~his invention, together with its o~her objects and ~ ~ ;
features, will be better and more clearly understood from the
,, .
more detailed description and explanation hereinafter following
when read in connection with the accompanying drawing, in which
Fig. 1 illustrates a cross-sectional view of an elemental seg-
.
ment of a form of matrix structure according to this invention,
this figure illustrating a single conduit and parts of the two
adjacent matrices o~ pellets; Fig. 2 illustrates a fragmentary
plan view of a portion of a matrix structure according to this ~--
invention, this illustration including two conduits together
with the contiguous matrices; Fig~ 3A shows a cross-sectional
view of one form of pellet which may be used in the practice of
this invention together with a coaring therefore; Fig. 3B shows
a cross-sectional view of a cluster of three pellets adjacent to
-7-
~ .
44~i,95 ~:
part of a wall ~f a conduit; Fig. 4 shows a perspective view ,
of a heat exchanger according to this invention, this figure
illustrating a surface combustion burner partly remaved from
the heat exchanger;Fig.5 shows another perspec~v~ ~ew of a heat
exchanger according to this invention, illustrating the inter-
connected piping; Fig. 6 shows a schematic diagram of a com-
-: .
posite boiler system, including its heat exchanger, which is
suitable for providing heat to an apartment or to a building;
and Fig. 7 schematically shows a diagram illustrating one form
, ,
of conduit interconnection ~ystem for use in the heat exchanger
of this invention. ~`
Throughout the drawing, the same or similar reference
characters will be employed to designate the same or similar -
parts wherever they occur. ~ -
Referring particularly to Figs. 4 and 5 of the draw- ,J,.
ing for a general description of the layout of the heat exchan-
ger of this invention, there are shown two annular supports or
... . .
mounting plates designated MPl and MP2 which may be parallel to
each other and spaced from each other. Both plates MPl and MP2 -;~
20~ have a plurality of openings for receiving and supporting a
plurality of parallel conduits Tl to T24 which may be, for
example, conventional pipes of the same general diameter and
of the same general length. In the illustration furnished for
explanation, all of the 24 substantially parallel conduits Tl
to T24 are shown positioned be-tween, and perpendicular to, the
two mounting plates MPl and MP2. The parallel conduits Tl to
T24 may be grouped into four sets of 9iX conduits, Tl to T6,
T7 to T12, T13 to T18, and Tl9 to T24 or in any other arrange- `
ments of æeries or parallel or series-parallel groups. All of ` ~,
the conduits may or may not be encased within a common housing -
-8-
, . ~ .
. .
9S
HX as shown in Fig. 4. u-shaped couplers, to be presently
described, may be employed to interconnect pairs of the con~
duits.
In Fig. 4, for example, cold water may be supplied
~o the two entrance conduits TCl and TC2 and the cold water,
after it has been heated by the heat exchanger HX, will be dis-
charged from two discharge conduits THl and TH2 (see Figs. 5
and 7). The water supplied to the entrance conduit TCl is fed
simultaneously to two parallel conduits TCl and TC12, while the ~;
water supplied to the entrance conduit TC2 is supplied to two ~ .
other parallel conduits T13 and T24. conduit Tl is connected
by a u-shaped coupler U12 to the next parallel adjacent conduit
: T2, while a similar U-shaped coupler U23 interconnects parallel : :
conduits T2 and T3. Likewise, another u-shaped coupler U34 ; . ~.
interconnects parallel conduits T3 and T4. Similarly, coupler : :
U45 interconnects conduits T4 and T5, while another coupler U56
interconnects conduits T5 and T6. An elbow fitting L6 inter-
connects conduit T6 to discharge conduit THl through which the .; .:~ .
heated water will be discharged. Thus, the conduits Tl to T6, ~ :
:,,~ . ... ..
representing a quadrant of the parallel donduits of the heat ~.r.::. :
exchanger HX, are interconnected to feed water received through .
the entrance conduit TCl to the discharge conduit THl, so that
water flowing through the parallel conduits of this quandrant "~
: will receive heat furnished by the burning gases of the combus- ~ :
tion burner BU to raise the temperature of the water to a desired :~
thermal level to be discharged by the discharge conduit THl. .; .
Similarly, another quadrant of parallel conduits T12 to T7 will
be interconnected with each other in the heat exchanger HX and
., .
these conduits will allow the water flowing therethrough to be ~`
raised in temperature by the combustion gases furnished by the
_g_ -:
1~ 9S
combustion burner BU. Similarly, the other quadrants of
parallel conduits T13 to T18 and Tl9 to T24 are interconnected
and these other quadrants serve to raise the temperature of
the water entering the entrance conduit TC2 to a desired tem-
perature, the heated water then being discharged by the dis-
charge conduit TH2.
Fig. 7 sch~ematically shows, in perspective, the four
quadrants of parallel conduits interconnected between the two
entrance conduits TCl and TC2 and the two discharge conduits
THl and TH2 for the first fluid. The fluid discharged by the
latter conduits THl and TH2 is, as already explained, the water
raised considerably in temperature by the heated gases which
constitute the second fluid. The second fluid, supplied by the
burner BU, is impacted directly and indirectly against all of
the quadrants of parallel conduits above referred to and this
second fluid must traverse the matrices of pellets of the heat
exchanger HX.
As,shown more clearly in Figs. 5 and 6, the heat ex-
changer HX has an axial longitudinal cylindrical space for
receiving a surface combustion burner BU. The burner may be
partially or fully removed from the heat exchanger HX whenever
desired by being slid axially out of the heat exchanger HX for
repair or maintenance or replacement, and then returned to its
normal position within the heat exchanger HX for normal opera-
tion. The burner BU has an opening axially positioned therein
for receiving the gas to be ignited and the air to be mixed
therewith in predetermined proportions so as to be properly
ignited and burned by the burner BU for producing gaseous prod- `
ucts at a relatively high temperature at the surface of the
burner BU for heating the water circulated through the quadrants
--10--
4~ti95
of parallel conduits of the heat exchange HX. The efficient
and predetermined mixture of air and gas, and the maintenance
of the predetermined ratio of the two components are important
in preventing the formation of noxious components, such as
carbon monoxide, which, if produced in appreciable volume, may
be dangerous to persons in the building. ~-
Now coming to the matrix construction of this inven~
tion, Fig. ~A shows one form of an elemental pellet P which
may be used in the practice of this invention. The pellet may ;
be coated by a layer of metal designated C. As shown more
~, ,
clearly in Figs. 1 and 2, each conduit, such as T, has two ma- ;~
trices affixed to its opposite side walls. As is more clearly
;.. ..
shown in the schematic drawing of Fig. 7, all of the conduits ;
Tl to T24 are arranged circumferentially about the axial center ,
of the heat exchanger HX and they are located between the two
~ concentric tangential cylindrical peripheries or boundaries, ~
:... . ~
namely, the inner tangential cylindrical periphery TGl and the
outer tangential cylindrical periphery TG2, as shown in Fig. 1.
The overall matrix structure, which is composed of the plural- `~
... ~
ity of scparate and independent matrices M12, M23, M34, etc.,
is arranged so that each matrix, such as M23, is positioned ;~
between two adjacent conduits, such as T2 and T3. Thus, all of
the matrices of pellets are positioned on what may be referred ` ~`
to as the sides or side walls of the parallel conduits Tl to
T24 of the heat exchanger HX. No part of any matrix is posi-
tioned on the underside of the tangential cylindrical periphery
TGl (see Figs. 1 and 5) nor on the outer side of the tangential `~
cylindrical periphery TG2 which is further removed from the axis
of the heat exchanger HX. No matrix of pellets completely sur- i ;
rounds any of the several parallel conduits in order that, in
-11- ..... .
i95
accordance with this invention, there will be free access for
the heated combustion gases to the underside of the various
parallel conduits. There is, therefore, a considerable and
important saving in material and labor and costs by omitting
pellets both from the underside of the several parallel con-
duits and from the outerside of the several conduits.
The surface combustion burner BU is supplied with
sparks or with a pilot light and produces combustion gases at,
say, 2,000 to 2,500F. and higher in the vicinity of the outer
cylindrical surface of the combustion burner. The adiabatic
flame temperature for n~tural gas burned with air is approxi-
mately 3,600F. If natural gas i~ burned with oxygen, adia-
batic flame temperatures approaching 6,000F. may be attained. :~
Under such conditions, higher heat fluxes can be obtained with-
,
out any increase in the size of the equipment.
The outer surface of the heat exchanger HX i9 shown
. , ,
by a dotted line in the schematic drawing of Flg. 6. It may ~-
take the form of a porous woven fabric of a heat resistant fiber
.: :
which may be~cylindrical in shape~and through which the gases
are transmitted and ignited upon reaching close to the inner
, . .
circumferential p-riph-ry TGl. T e ignited gases are influ-
enced by air pres-ure developed by appropriate blower equipment `~ .
80 that the flaming ga~es reach the under surfaces of the sev-
ral parallel conduits Tl to T24 of the heat exchanger HX.
This direct contact with the under surfaces of the conduits is
a factor in the increased efficiency of the equipment. The -`
...
~ burning gas also directly impinges upon, and necessarily i~ ~-
:
passed through, the several matrices M12, M23, M34, etc. Very
little, if any, of the combustion gases will impinge upon the
outer walls of the parallel conduits Tl to T24 which are `'
-12 - ~
~ 9S
located on, or adjacent to, the outer cylindrical tangential -
periphery TG2 (see Fig. 1). In accordance with this invention,
no pellets are positioned beyond the outer periphery TG2 be-
cause the combustion gases are relatively cooler in that region.
The savings and improvements due to this significant omission
are considerable. ;~
By the proper choice of the size of the pellets with
respect to the diameter of the conduits, a desirably tortuous -
path for the flow of the combustion gases is achieved without
any excessive pressure loss through the ~atrices. By omitting
pellets from all but the sidewalls of the several conduits Tl -~
to T24, the small number of pellets employed will reduce the
~.i .,: .. .
weight of the structure, and the dimensions of the heat ex- ;
changer equipment will be relatively small.
In one embodiment of the heat exchanger HX of this
invention, the various parallel conduits Tl to T24 were employed
to transmit water to be heated. The conduits were made of steel
and they had an outside diameter of 5/8". The parallel conduits `~
were spaced apart, having a spacing of about 1" between their ;
centers. The pellets were steel balls having an outside dia-
meter of approximately 0.174 inches and each was coated with
copper. Although they were randomly arranged between the side `
walls of the various parallel conduits, the combination of the
pellets of the matrices and the adjoining conduits were brazed
to each other so that there was gcod thermal contact not only
between the steel balls, but also between the steel balls and
the several conduits to provide a belt-connected heat exchanger ,
HX. The copper coating on each pellet was about l/lOOOth of an
inch in thickness. It will be understood that any desired
pressure drop..................................................
-13-
can be achieved in the heat exchanger merely by changing the
diameter of the spherical pellet if a spherical pellet is
used or by changing the spacing between the conduits, or both.
It will be apparent that the spaces between the pel- -
lets allow the flue gases of the burner BU to be deflected in ;
their passage through the matrix. The spaces between the pel-
lets, because of the size of the pellets, are sufficient to
allow rays of light or luminous hot gaees to be observed through -
the matrix. Lack of opacity is a feature of the matrix. Thus,
linear openings permit the heated gases of the burner to move
rather rapidly through the matrix to the chimney or to any
other disposal point, thereby minimizing pressure loss commen-
surate with efficient heat transfer.
By brazing the composite structure of each matrix
with the adjacent parallel conduits, a unitary mass is estab-
lished for the heat exchanger HX exhibiting a thermal conduc-
tive property suitable for transferring heat efficiently from
heated gases to the fluid carried through the parallel conduits.
As shown in Fig. 3B, the brazing operation will cause the partly
molten copper to be accumulated or collected at the points of `~
contact of the several pellets and between the pellets and the
adjacent conduits. The brazing operation can be performed in
a container of dissociated ammonia, carbon dioxide or a vacuum
or any other suitable atmosphere maintained at a suitable tem-
perature for a sufficient time interval, after which the brazed
product may be removed from the container.
Referring now to Fig. 6 of the drawing, there is
shown a schematic diagram of the compact boiler system of this
invention. Natural gas, for example, may be supplied through a
conduit S which may be connected, through a solenoid valve 5V
-14-
... . -
:,~ ,, .
i~ 3S
and a gas regulator RG, to a mixing chamber MC. The mixing
chamber MC is also connected independently to a blower BL
which supplies air at a predetermined rate and at a predeter- ;
mined pressure into the mixing chamber MC. No venturi appara-
tus is required in the s~stem. The gas supply pipe is equipped
with a nozzle and pointed in the direction of the burner B~ so
that the emitted gas will be mixed with the air supplied by
the blower BL and the ratio of the volume of gas to the volume `
of air is maintained constant. The arrangement for mixing air
and gas, and for maintaining their proportions substantially
constant regardless of variations in the pressure of the air
supplied by the blower B~, is shown and described in Canadian
Patent Application ~o, 091,945 filed on August 19, 1970 in
the name of American Standard Inc. ~-
The output of the mixing chamber MC is fed through a ~ -
conduit MP to the input of the burner BU. The burner BU may
be, for example, any form of surface combustion burner but it
is preferably one of the type shown and described in a united
States Patent of W. J. Witten, No. 3,269,449, issued August
30, 1966 and assigned to the assignee of this application.
. .
The burner element of the surface combustion burner
BU may, if desired, comprise a hollow cylindrical structure o
a heat resistant porously woven fabric of heat resistant fibers,
preferably of alumina ceramic and nichrome wire. This fabric
may be about 1/8" thick and embody a weave density for dropping
the pressure of the gas by about 1/2" or less of water for a ~ `
gas-air flow velocity of about 20 cubic feet per minute per
square foot of the burner surface. A suitable fabric for the
burner surface is that marketed ùnder the trademark "Fiber-
Frax" by the Carborundum Co. Such a fabric can withstand a -`
-15-
, . .
1~ 5
temperature of about 2,000F. continuously. Such a fabric is
sufficient and appropriate even for the higher flame tempera-
tures that may be produced, because o~ the cooling effect of
the air supplied by the blower. The hollow cylinder of the
fabric may be positioned within a corresponding cylinder of a
wire mesh made, for example, of galvanized steel. The tubular -
structure of the burner may be supported and held rigid by a
steel wire or by any other appropriate or well known means.
As already noted, the burner BU is axially positioned -
within the heat exchanger HX which embodies the parallel con-
duits through which water flows, as already described. The
inlet water received from a city water supply system, for
example, a~nd flowing through a conduit W, travels through a
fill valve FV. The fill valve FV may be opened whenever de- ~ '
sired in order to supply water to the boiler system initially
or to supply water to replace water previously evaporated or
leaked from the boiler system, as may be required. The boiler
system includes a water loop which employs a pump circulator P, ;
the parallel conduits Tl to T24 of the heat exchanger HX, and
a baseboard heater BH, only one of which is shown in Fig. 6
for illustation. Naturally, any number of baseboard heaters
may be connected in series or in parallel with each other if
so desired. The pu~p P raises the pressure of the water sup-
plied to the water loop and maintains the pressure at a sub- -
stantially constant level. The same water may be recirculated
through the loop which, as already noted, would include both
the heat exchanger HX and the baseboard heater BH and this
recirculation of water may continue over and over again.
It will be also noted that the water loop of the
boiler system may be connected to an expansion tank ET and to
-16-
,. . , . - ~ .:- `, . -
16J 4~j9S ;~- ~
a conventional air eliminator AL. The expansion tank ET is
intended to take up any change in the volume of the water nec-
essarily resulting from changes in the temperature of the water.
The air eliminator AL will remove any surplus of air or oxygen
that may be developed or entrapped in the water line. `~
A miniature boiler system of the kind described above
may be fed water of a temperature of about 150F. and the water
may be raised in temperature by the system to about 180F. or
to a higher temperature. The size of the miniature boiler
may, for example, require gas capable of yielding about 100,000 ;~
. .
B.T.U. per hour. A desirable air-fuel weight ratio may be
about 20 to 1. The stack temperature of the exhaust gas may -
be about 240F. The carbon dioxide content of the exhaust gas
may be no more than about l~/o~ The carbon monoxide content is
virtually zero due to the combustion efficiency of the system.
The matrix volume in the sample used was apprGximately 47 cubic
inches and the weight of the pellets of each matrix was about
eight pounds. The matrix and the burner assembly together
weighed under about 20 lbs. and was, therefore, easily trans~
portable. The cylindrical heat exchanger sample had an approx-
imate overall diameter of 8~i" and a length of 6". When pack-
aged as a hydronic heating boiler, which included the heat --
exchanger, the pump, the controls and the accessories, the
overall dimensions were 19" in width, 17" in depth and 14" in
height. Smaller packages are readily designed and constructed.
For example, the pellets need not be spherical; they
may be ellipsoids or any other regular or irregular shaped
bodies, preferably made of metal, but plastic materials, pre- ,~
ferably metallized, may also be employed, if desired. Further-
more, t~e spherical pellets may be replaced by metallic scraps
-17-
.~j , .- . .
or metallized plastic scraps or ~ ms of saddles, etc. It is
important, however, to have the matrix exhibit good porosity `~
for the combustion gases and, in addition, some transparency
to light and other rays that may be generated ~y the combu8- .
tion gases. Furthermore, although the pellets have been des- ` -
cribed as made of steel and coated with copper, any other '~
materials may suffice for the pellets and their coatings, if
any. For example, the pellets may be made of aluminum, and
. : , .
the various pellets may be brazed to each other and to the
adjacent conduits with a brazing material of copper, aluminum
or any other metal so as to yield a unitary structure of rela- ;~
tively light weight. The term "pellet~', as used in the claims,
i,
is intended to include these variants and others.
Although twenty-four parallel conduits have been
shown in the illustrated heat exchanger of this invention, it
will be apparent that any number of parallel conduits may be
employed in the heat exchanger, whether in a circularly cylin-
drical assembly, or in a square or rectangular cylindrical
assembly, or in any other form, but, in any case, a corres-
, ,
ponding number of matrices of pellet~-of whatever shape may be
brazed between the side walls of the various conduits to pro-
vide a belt-shaped structure. The combustion burner should be
designed to match and coordinate with the axial space, what-
ever its shape, to provide a coordinated structure of minimal
dimensions. A miniaturized assembly is one of the main features
of this invention. Moreover, the conduits of the heat exchanger
need not be arranged in quads. They may be interconnected to
provide, if desired, a continuous unidirectional path for the
fluid flowing through all of the various parallel conduits
making up the heat exchanger, but any other circuital connec-
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.
`::
tions, whether parallel or series-parallel, may be employed.
The temperatures abovenoted which are developed by
the structure in a typical installation and the fuel require-
ments of the burner may be changed as desired. The geometry
of the conduits, the nature of the pellets and their random ~ ~ -
spacing, and the pressure of the combustion gases all contri-
bute to determine the temperaturesand pressure losses developed
in the apparatus, but they may be adjusted to meet any prede-
termined or desired magnitudes.
It will be understood that, although the invention ~
has been described in connection with the production of hot ;~- -
or heated water for illustrative purpose~ it is readily ad-
justable for the production of steam, whether saturated or - -
. . .
~upersaturated, or for heating or changing the state of any
fluid, whether gaseous or liquid. The heat exchanger HX may
ohviously be employed for cooling purposes, if so desired. , ~ ;
Furthermore, as will be apparent from a reading of this speci-
fication, the fluids employed in the heat exchanger may, if `~ --
desired, both be liquid or both be gaseous. ; ; -
The dimensions of the several components above re- ~;
ferred to in connection with an example for the practice of -
this invention were given merely for illustration and explana-
tion and are not intended to be limitations upon the invention.
" " '
obviously, these values may be changed, as desired, to meet any
`,t :'
conditions and to achieve any desired heat transfer relations
between fluids. Obviously, the conduits and their dimensions
are readily changed, either increased or decreased, to meet the ~
exigencies of any p~rticular problem in the practice of this r' " ~ '
invention. `~
While this invention has been shown and described
-19- , ~":
4~
in certain particular embodiments merely for illustration and
explanation, it will be apparent that it may be organiz~d in
many different arrangements within the scope of this invention.
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