U.S. patent application number 13/156679 was filed with the patent office on 2011-12-15 for counterflow heat exchanger.
This patent application is currently assigned to PB HEAT, LLC. Invention is credited to David A. SCEARCE.
Application Number | 20110303400 13/156679 |
Document ID | / |
Family ID | 44627544 |
Filed Date | 2011-12-15 |
United States Patent
Application |
20110303400 |
Kind Code |
A1 |
SCEARCE; David A. |
December 15, 2011 |
COUNTERFLOW HEAT EXCHANGER
Abstract
A counterflow heat exchanger having a plurality of heat
exchanger elements in a stacked, spaced-apart arrangement forming a
plurality of inter-element passages. Each element has fluid
passages formed between facing sections of a first plate and a
second plate. A first-fluid passage has an outer passage
circumscribing an inner passage in fluid communication with the
outer passage. An inlet-port traversing passage in fluid
communication with the outer passage, an outlet-port traversing
passage in fluid communication with the inner passage and a
second-fluid traversing passage circumscribed by the inner passage
traverse the first and second plates. A first-fluid inlet header
includes the inlet-port traversing passage of each element. A
first-fluid outlet header includes the outlet-port traversing
passage of each element. A second-fluid inlet passage in fluid
communication with the plurality of inter-element passages includes
the second-fluid traversing passage of each element.
Inventors: |
SCEARCE; David A.; (Reading,
PA) |
Assignee: |
PB HEAT, LLC
Bally
PA
|
Family ID: |
44627544 |
Appl. No.: |
13/156679 |
Filed: |
June 9, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61354943 |
Jun 15, 2010 |
|
|
|
Current U.S.
Class: |
165/164 |
Current CPC
Class: |
F24H 8/00 20130101; F28D
9/0043 20130101; Y02B 30/102 20130101; Y02B 30/00 20130101; F24H
1/32 20130101; Y02B 30/106 20130101; F28D 21/0007 20130101; F28D
9/0012 20130101; F24H 8/006 20130101 |
Class at
Publication: |
165/164 |
International
Class: |
F28D 7/00 20060101
F28D007/00 |
Claims
1. A counterflow heat exchanger comprising: a plurality of heat
exchanger elements in a stacked, spaced-apart arrangement forming a
plurality of inter-element passages, each element comprising: a
first plate adjacent a second plate; a first-fluid passage formed
between facing sections of the first plate and the second plate,
the first-fluid passage comprising an outer passage circumscribing
an inner passage in fluid communication with the outer passage; an
inlet-port traversing passage traversing the first and second
plates, the inlet-port traversing passage in fluid communication
with the outer passage; an outlet-port traversing passage
traversing the first and second plates, the outlet-port traversing
passage in fluid communication with the inner passage; and a
second-fluid traversing passage traversing the first and second
plates, the second-fluid traversing passage circumscribed by the
inner passage; a first-fluid inlet header comprising the inlet-port
traversing passage of each element; a first-fluid outlet header
comprising the outlet-port traversing passage of each element; and
a second-fluid inlet passage comprising the second-fluid traversing
passage of each element, the second-fluid inlet passage in fluid
communication with the plurality of inter-element passages.
2. The counterflow heat exchanger according to claim 1, wherein the
outer passage, the inner passage and the second fluid passage are
concentric.
3. The counterflow heat exchanger according to claim 1, wherein
each element has a generally circular shape and the outwardly
facing surfaces of each element have raised, radially-oriented
dimples arranged and configured to allow generally uniform radial
flow of a fluid over the surfaces.
4. The counterflow heat exchanger according to claim 1, further
comprising a plurality of transfer seals having a central passage
therethrough, the plurality of transfer seals coupling the
inlet-port traversing passages comprising the first-fluid inlet
header and the outlet-port traversing passages comprising the
first-fluid outlet header.
5. The counterflow heat exchanger according to claim 4, wherein
each transfer seal comprises: a generally cylindrical central
portion configured to make sealing contact with one of the
inlet-port traversing passages or the outlet-port traversing
passages when the plurality of heat exchanger elements are
assembled into the spaced-apart arrangement.
6. The counterflow heat exchanger according to claim 5, wherein
each transfer seal further comprises: a nipple extending axially
from each side of the generally cylindrical central portion; each
nipple having a nipple outer diameter sized for insertion in one of
the inlet-port traversing passages or the outlet-port traversing
passages with a clearance fit; the central portion of each transfer
seal having a transfer seal outer diameter sized to be greater than
the nipple outer diameter; a circumferential O-ring channel in an
outer surface of each nipple; an O-ring retained in the O-ring
channel and sized to make sealing contact between the nipple and
one of the inlet-port traversing passages or the outlet-port
traversing passages when the plurality of heat exchanger elements
are assembled into the spaced-apart arrangement.
7. The counterflow heat exchanger according to claim 5, wherein the
generally cylindrical central portion of each transfer seal has an
axial extent sufficient to provide a predetermined spacing for the
inter-element passages formed between the plurality of heat
exchanger elements of the spaced-apart arrangement.
7. The counterflow heat exchanger according to claim 1, wherein the
plurality of heat exchanger elements are spaced-apart by a
plurality of transfer seals coupled to the inlet-port traversing
passages and the outlet-port traversing passages.
8. The counterflow heat exchanger according to claim 1 wherein the
plurality of heat exchanger elements are housed in an enclosure
having a first-fluid inlet port in fluid communication with the
first-fluid inlet header, a first-fluid outlet port in fluid
communication with the first-fluid outlet heard, a second-fluid
inlet port in fluid communication with the second-fluid inlet
passage, an exhaust port in fluid communication with the
inter-element passages and a condensate drain in fluid
communication with the inter-element passages.
9. The counterflow heat exchanger according to claim 1 wherein the
stacked arrangement of heat exchanger elements is secured between a
first support plate and a second support plate connected by a
plurality of tie rods.
10. The counterflow heat exchanger according to claim 1 wherein the
second-fluid inlet passage has a first end coupled to a
second-fluid inlet port and a second end coupled to a closure
configured to seal the second-fluid transfer passage of a last
element of the plurality of heat exchanger elements in the stacked
arrangement.
11. A heat exchanger element comprising: a first plate adjacent a
second plate; a first-fluid passage formed between facing sections
of the first plate and the second plate, the first-fluid passage
comprising an outer passage circumscribing an inner passage in
fluid communication with the outer passage; an inlet port
traversing the first and second plates, the inlet port in fluid
communication with the outer passage; an outlet port traversing the
first and second plates, the outlet port in fluid communication
with the inner passage; and a second-fluid passage traversing the
first and second plates, the second-fluid passage circumscribed by
the inner passage.
12. The counterflow heat exchanger element according to claim 11,
wherein the outer passage, the inner passage and the second-fluid
passage are generally concentric.
13. The counterflow heat exchanger element according to claim 11,
wherein the element has a generally circular shape and the
outwardly facing surfaces of each element have raised,
radially-oriented dimples arranged and configured to allow
generally uniform radial flow of a fluid over the surfaces.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to U.S. Provisional Patent
Application No. 61/354,943, filed Jun. 15, 2010, and incorporated
herein by reference and claims the earlier filing date of the
provisional application.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a device and method for
transferring heat from flue (or combustion) gas through an
interposing wall (or plate) to a fluid without allowing the flue
gas and fluid to mix. More particularly, the present invention
relates to a counterflow heat exchanger and method for cooling flue
gas below a condensing temperature.
[0003] Most fossil fuels are combusted with ambient air in a
chamber, such as a boiler. The combustion product gas is exhausted
from the chamber through a flue. Typical flue gas from the
combustion of fossil fuels contains substantial amounts of
uncombusted nitrogen, and to a lesser degree carbon dioxide and
water vapor respectively formed by the combustion of carbon and
hydrogen with atmospheric oxygen. In volume, the water vapor can be
as much as seven to eleven percent of the flue gas. The water vapor
contains energy in the form of latent heat.
[0004] Absent a cost effective device and method for cooling the
hot flue gas below the condensing temperature of the water vapor to
recover the latent heat and to transfer the energy in the hot flue
gas to a working fluid, the flue gas energy would be exhausted
through the flue and wasted. Accordingly, a devise able to cost
effectively recover latent heat from hot flue gases is
desirable.
BRIEF SUMMARY OF THE INVENTION
[0005] Briefly stated, one embodiment of the present invention is
directed to a counterflow heat exchanger comprising a plurality of
heat exchanger elements in a stacked, spaced-apart arrangement
forming a plurality of inter-element passages. Each element
comprises a first plate adjacent a second plate. A first-fluid
passage is formed between facing sections of the first plate and
the second plate. The first-fluid passage comprises an outer
passage circumscribing an inner passage in fluid communication with
the outer passage. An inlet-port traversing passage traverses the
first and second plates. The inlet-port traversing passage is in
fluid communication with the outer passage. An outlet-port
traversing passage traverses the first and second plates. The
outlet-port traversing passage is in fluid communication with the
inner passage. A second-fluid traversing passage traverses the
first and second plates. The second-fluid traversing passage is
circumscribed by the inner passage. A first-fluid inlet header
comprises the inlet-port traversing passage of each element. A
first-fluid outlet header comprises the outlet-port traversing
passage of each element. A second-fluid inlet passage comprises the
second-fluid traversing passage of each element. The second-fluid
inlet passage is in fluid communication with the plurality of
inter-element passages.
[0006] Another embodiment of the present invention is a counterflow
heat exchanger element comprising a first plate adjacent a second
plate. A first-fluid passage is formed between facing sections of
the first plate and the second plate. The first-fluid passage
comprises an outer passage circumscribing an inner passage in fluid
communication with the outer passage. An inlet-port traversing
passage traverses the first and second plates. The inlet-port
traversing passage is in fluid communication with the outer
passage. An outlet-port traversing passage traverses the first and
second plates. The outlet-port traversing passage is in fluid
communication with the inner passage. A second-fluid traversing
passage traverses the first and second plates. The second-fluid
traversing passage is circumscribed by the inner passage.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0007] The foregoing summary, as well as the following detailed
description of preferred embodiments of the invention, will be
better understood when read in conjunction with the appended
drawings. For the purpose of illustrating the invention, there is
shown in the drawings embodiments which are presently preferred. It
should be understood, however, that the invention is not limited to
the precise arrangements and instrumentalities shown.
[0008] In the drawings:
[0009] FIG. 1 is a perspective view of the front, top and right
side of a preferred embodiment of a counterflow heat exchanger in
accordance with the present invention;
[0010] FIG. 2 is a partial exploded perspective view of the
counterflow heat exchanger of FIG. 1;
[0011] FIG. 3 is an assembly diagram of the counterflow heat
exchanger of FIG. 1;
[0012] FIG. 4 is a front perspective view of a heat exchanger
element of the counterflow heat exchanger of FIG. 1;
[0013] FIG. 5 is a side perspective view of a transfer seal of the
counterflow heat exchanger of FIG. 1;
[0014] FIG. 6 is an enlarged cross sectional view of the
counterflow heat exchanger of FIG. 1;
[0015] FIG. 7 is an enlarged partial view of the cross sectional
view of the counterflow heat exchanger of FIG. 6;
[0016] FIG. 8 is a schematic diagram of a cross sectional view of
the counterflow heat exchanger of FIG. 1;
[0017] FIG. 9 is a schematic diagram of a heat exchanger element of
the counterflow heat exchanger of FIG. 1; and
[0018] FIG. 10 is a front perspective view of another embodiment of
a counterflow heat exchanger element in accordance with the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Reference will now be made in detail to embodiments of the
invention, examples of which are illustrated in the accompanying
drawings. The terminology used in the description of the invention
herein is for the purpose of describing particular embodiments only
and is not intended to be limiting of the invention.
[0020] As used in the description of the invention and the appended
claims, the singular forms "a", "an" and "the" are intended to
include the plural forms as well, unless the context clearly
indicates otherwise. The words "and/or" as used herein refers to
and encompasses any and all possible combinations of one or more of
the associated listed items. The words "comprises" and/or
"comprising," when used in this specification, specify the presence
of stated features, integers, steps, operations, elements, and/or
components, but do not preclude the presence or addition of one or
more other features, integers, steps, operations, elements,
components, and/or groups thereof.
[0021] The words "right," "left," "lower" and "upper" designate
directions in the drawings to which reference is made. The words
"inwardly" and "outwardly" refer to directions toward and away
from, respectively, the geometric center of the structure to which
reference is made, and designated parts thereof. The terminology
includes the words noted above, derivatives thereof and words of
similar import.
[0022] Although the words first, second, etc., are used herein to
describe various elements, these elements should not be limited by
these words. These words are only used to distinguish one element
from another. For example, a first passage could be termed a second
passage, and, similarly, a second passage could be termed a first
passage, without departing from the scope of the present
invention.
[0023] The following description is directed towards various
embodiments of a counterflow heat exchanger in accordance with the
present invention.
[0024] Referring to the drawings in detail, where like numerals
indicate like elements throughout, there is shown in FIGS. 1-9 a
preferred embodiment of the counterflow heat exchanger generally
designated 10, and hereinafter referred to as the "heat exchanger"
10 in accordance with the present invention. In a preferred
application, the heat exchanger 10 is for cooling flue (or
combustion) gas below the condensing temperature of water vapor
contained in the flue gas. In other applications, the heat
exchanger 10 may used for cooling the hot fluid without producing a
condensate.
[0025] Referring to FIGS. 1-3 and 6, the heat exchanger 10
comprises an outer gas-tight wrapper 12 housing a plurality of heat
exchanger elements 100 in a stacked, spaced-apart arrangement 14
secured between a first support plate 16 and a second support plate
18 connected by a plurality of fasteners 20 such as tie rods with
threaded ends and corresponding nuts.
[0026] In the illustrated embodiment, the outer wrapper 12 is a
separable two piece shell having a generally rectangular
cross-sectional shape for conformance with the corresponding
rectangular shape of the support plates 16, 18. In another
embodiment (not shown), the outer wrapper 12 may have a cylindrical
cross-sectional shape for conformance with circular support plates
(not shown). In general, the outer wrapper 12 may have any desired
shape allowing the outer wrapper 12 to form a gas-tight enclosure
housing the arrangement 14 of heat exchanger elements 100.
[0027] In the illustrated embodiment, the outer wrapper has an
upper section 22 with an exhaust port 24 and a lower section 26
with a condensate drain 28 extending from a fluid collector (or
trap) 30 formed in the bottom of the lower section 26. In an
alternate embodiment, the trap 30 may be a component separate from
the outer wrapper 12 and part of a drainage system to which the
outer wrapper is plumbed.
[0028] In another embodiment (not shown), the outer wrapper 12 may
be more than two sections or may be separable into front and rear
sections instead of upper and lower sections depending on the form
factor desired for a particular installation.
[0029] The edges of the upper and lower sections 22, 26 forming the
outer wrapper 12 are configured to join each other and the first
(or front) support plate 16 and the second (or rear) support plate
18 in a manner able to form a gas tight enclosure for the
arrangement 14 of heat exchanger elements 100 enclosed therein. For
example, the outer edges of the upper and lower sections 22, 26 of
the outer wrapper 12 may be outwardly flanged to join the sections
to each other. Other outer edges may be inwardly flanged to join
the first and second support plates 16, 18 to the upper and lower
sections 22, 26 of the outer wrapper 12. The flanges may be
channeled to receive or support a gasket or elastomeric material
between adjoining surfaces and to receive a fastener releasably
joining the component parts.
[0030] The outer wrapper 12 may be fabricated from a wide variety
of heat resistant materials including, but not limited to,
polyphenylene sulfide, glass-filled polypropylene or similar
high-performance thermoplastics. The outer wrapper 12 may also be
fabricated from coated steel or high grade stainless steel.
[0031] Referring to FIGS. 2-4, in one embodiment, the heat
exchanger elements 100 comprising the arrangement 14 are formed by
circular plate pairs. Each element 100 comprises a first plate 102
adjacent a second plate 104. A first-fluid passage 106 is formed
between facing sections of the first plate 102 and the second plate
104 by opposing channels in the facing sections. The first-fluid
passage 106 comprises an outer passage 108 circumscribing an inner
passage 110 in fluid communication with the outer passage through
one or more interconnecting passages 112. In some embodiments, the
outer passage 108 may be spaced from the inner passage 110 by a web
109 through which the interconnecting passages 112 pass. An
inlet-port traversing passage 114 in fluid communication with the
outer passage 108 traverses the first and second plates 102, 104.
In some embodiments, each element 100 may have additional
port-traversing passages, such as a second (or alternate) port
traversing passage 114.sub.a, to provide the ability to accommodate
alternate uses and plumbing configurations. For example, the
alternate port traversing passage 114.sub.a may be used in some
embodiments as an additional inlet-port traversing passage or in
other embodiments as a drain port. An outlet-port traversing
passage 116 in fluid communication with the inner passage 110 also
traverses the first and second plates 102, 104. In addition to the
inlet-port and outlet-port traversing passages 114, 116, the first
and second plates 102, 104 of each element 100 are traversed by a
centrally-positioned, second-fluid traversing passage 118
circumscribed by the inner passage 110.
[0032] In some embodiments, the plates forming each element 100 may
have a generally circular shape and may have concentric outer and
inner passages as shown in FIG. 4. In other embodiments, the plates
may have a square or rectangular shape such as the heat exchanger
element 100' shown in FIG. 10. In general, the plates may have any
desired shape allowing the outer wrapper 12 to form a gas-tight
enclosure housing the arrangement 14 of elements 100.
[0033] Referring to FIG. 10, in some embodiments, a first-fluid
passage 106' of each heat exchanger element 100' may have one or
more generally concentric fluid passages 106.sub.n' between the
outer and inner passages 108', 110'. Interconnecting passages 112'
provide a fluid path between the one or more concentric fluid
passages 106.sub.n', the outer passage 108' and the inner passage
110'. The interconnecting passages 112' may be radially oriented or
may be angled with respect to a radius. Other embodiments may have
more than three concentric passages or less than three concentric
channels with one or more interconnect passages connecting adjacent
concentric passages. In still other embodiments, the passages need
not be concentric channels. Although circumscribing each other, the
passages may have a generally meandering shape. Each heat exchanger
element 100' may also have an inlet-port traversing passage 114',
outlet-port traversing passage 116' and a centrally-positioned,
second-fluid traversing passage 118' circumscribed by the inner
passage 110'.
[0034] In some embodiments, the outwardly facing surfaces of each
element may have raised, radially-oriented dimples 120 arranged and
may be configured to allow generally uniform radial flow of a fluid
over the surfaces (See, e.g., FIG. 4). In other embodiments, the
outwardly facing surfaces of each element may be smooth. (See,
e.g., FIG. 10.)
[0035] The material from which the heat exchanger elements are
fabricated is preferably a metal such as 316 stainless steel.
Alternatively, 304 or 400 series stainless may be used. Other
thermally conductive materials, titanium for example, compatible
with the combustion gas products and the cooling (or working) fluid
may also be used. The channels in the first and second plates 102,
104 forming the passages in each element 100, 100' are preferably
created by stamping or hydroforming. Alternatively, the plates and
the channels therein may be formed by casting.
[0036] Referring to FIGS. 2, 3 and 6, the stacked, spaced-apart
arrangement 14 into which the plurality of heat exchanger elements
100 are assembled has a first-fluid inlet header 32 comprising the
inlet-port traversing passage 114 of each element 100 and a
first-fluid outlet header 34 comprising the outlet-port traversing
passage 116 of each element 100. In some embodiments, a plurality
of transfer seals 36 described below couple the inlet-port
traversing passages 114 comprising the first-fluid inlet header 32
and the outlet-port traversing passages 116 comprising the
first-fluid outlet header 34. The plurality of heat exchanger
elements 100 are spaced-apart by the plurality of transfer seals 36
forming a plurality of inter-element passages 38 in the assembly
14.
[0037] Referring to FIGS. 3 and 5-7, in some preferred embodiments,
each transfer seal 36 may be a generally cylindrical component with
a central passage 40 extending axially therethrough. The transfer
seal 36 may have a generally cylindrical central portion 42
configured to make sealing contact with one of the inlet-port
traversing passages or outlet-port traversing passages when the
plurality of heat exchanger elements are assembled into the
spaced-apart arrangement. A nipple 44 extends axially from each
side of the generally cylindrical central portion 42. Each nipple
44 has a nipple outer diameter sized for insertion in one of the
inlet-port traversing passages 114 or outlet-port traversing
passages 116. In some embodiments, the nipple outer diameter may be
less than the inner diameter of the inlet-port or outlet-port
traversing passages 114, 116 allowing each nipple to be inserted in
the traversing passages with a clearance fit when the heat
exchanger elements 100 are assembled to form the spaced-apart
arrangement 14. Alternatively, in other embodiments, the nipple
outer diameter may be greater than the inner diameter of the
inlet-port or outlet-port traversing passages 114, 116 requiring
each nipple to be inserted in the traversing passages with an
interference (or press) fit. In some embodiments, the outer
diameter of the central portion 42 of each transfer seal 36 may be
sized to be greater than the outer diameter of the nipples 44. In
other embodiments (not shown), the outer diameter of the central
portion 42 of each transfer seal 36 may be sized to be less than or
equal to the outer diameter of the nipples 44. In some embodiments,
a circumferential O-ring channel 46 in the outer surface of each
nipple 44 retains an O-ring 48 sized to make sealing contact
between the nipples 44 and one of the inlet-port traversing
passages 114 or outlet-port traversing passages 116 when the
elements 100 are assembled into the arrangement 14. The generally
cylindrical central portion 42 of the transfer seal 36 may have an
axial extent sufficient to provide a desired predetermined spacing
for the inter-element passages 38 formed between the plurality or
heat exchanger elements 100 of the spaced-apart arrangement 14.
[0038] The transfer seals 36 may be fabricated from the same
material identified above for the plates 102, 104 forming the each
element 100. The O-ring 48 may be made from any elastomer
compatible with flue gas products and is preferably made for
ethylene propylene diene monomer (M-class) rubber or Viton.TM., a
brand of synthetic rubber and fluoropolymer elastomer made by
DuPont Performance Elastomers L.L.C.
[0039] When the plurality of heat exchanger elements 100 is
assembled together with the transfer seals 36 into the arrangement
14 in accordance with FIG. 3, a second-fluid inlet passage 50
comprising the second-fluid traversing passage 118 of each element
100 is formed. The second-fluid inlet passage 50 is in fluid
communication with the plurality of inter-element passages 38.
[0040] The second-fluid inlet passage 50 has a first end 50a
coupled to a second-fluid inlet port 52 in the first support plate
16. In some embodiments, the second end 50b of the second-fluid
inlet passage 50 may be coupled to a removable closure 54
configured to seal the second-fluid traversing passage 118 of a
last element of the plurality of heat exchanger elements 100 in the
stacked arrangement 14.
[0041] In some embodiments, the stacked arrangement 14 of heat
exchanger elements 100 is secured between the first support plate
16 and the second support plate 18 by a plurality of fasteners 20
connecting the two plates 16, 18. For ease of assembly and
disassembly, the fasteners 20 preferably are tie rods that
terminate in a threaded portion for receiving a threaded nut and
extend between and through penetrators 58 in the first and second
support plates 16, 18.
[0042] In some embodiments (not shown), the first and last elements
of the plurality of elements 100 may replace the first and second
support plates 16, 18. In such embodiments, each element, including
the first and last elements, may have penetrators (see, e.g., FIG.
10) through which the tie rods pass. Further, the last element may
not have a second-fluid traversing passage. Instead, the central
area circumscribed by the inner passage 110 remains a continuous
web. The internal surface of the last element may or may not be
provided with a thermally insulating insert.
[0043] In some embodiments, the second-fluid inlet port 52 may
traverse the first support plate 16 and the second support plate 18
may have a first-fluid inlet port 60 and a first-fluid outlet port
62. When the plurality of heat exchanger elements 100 are housed in
an enclosure formed by the outer wrapper 12, the first-fluid inlet
port 60 is in fluid communication with the first-fluid inlet header
32 and the first-fluid outlet port 62 is in fluid communication
with the first-fluid outlet header 34. The second-fluid inlet port
52 is in fluid communication with the second-fluid inlet passage
50. The exhaust port 24 is in fluid communication with the
inter-element passages 38. The condensate drain 28 also is in fluid
communication with the inter-element passages 38.
[0044] During operation, the internal pressure in the inlet and
outlet fluid headers 32, 34 acts circumferentially on the internal
surface of the nipples 44. Since the internal pressure serves to
reinforce the radial sealing surface, the transfer seals 36 do not
depend on the tie rods 20 to compress the O-rings 48. The stress in
the tie rods 20 is predominantly induced by the internal pressure
of the working (or first) fluid.
[0045] In one embodiment, the heat exchanger 10 may be designed to
be used in conjunction with a gas or liquid fuel combustion system,
such as a gas or oil burner. In another embodiment, the heat
exchanger 10 may be designed to be used with a solid fuel burner or
other source of hot gases. The method for manufacturing the heat
exchanger 10 and the materials from which the heat exchanger
elements are fabricated may be application specific. For example,
the elements could be stamped from aluminum or stainless steel for
condensing boilers, or from steel for non-condensing boilers.
Alternatively, the heat exchanger elements could be die-cast
aluminum for condensing boilers and die-cast steel for
non-condensing boilers or they could be cast aluminum for
condensing boilers or cast iron for non-condensing boilers.
[0046] FIGS. 8 and 9 are representative flow diagrams of the heat
exchanger 10 in use. Combustion gases enter the center cylindrical
opening or second fluid inlet passage 50 through a gas flue (not
shown) attached to the second-fluid inlet port 52 in the first
support plate 16. The gases flow axially through the second-fluid
inlet passage 50 and radially outwardly through the inter-element
passages 38 between the elements 100 of the arrangement 14. As the
gases flow radially outwardly, the gases successively contact the
concentric fluid passages (e.g., the inner passage 110 and then the
outer passage 108) comprising the first-fluid passage 106, and flow
over and in contact with the web 109 which acts as an extended
heating surface between the concentric fluid passages. When the
gases flow beyond the extent of the arrangement 14, the gasses are
captured by the outer, gas-tight wrapper 12 and exit through the
exhaust port 24.
[0047] In one embodiment a first fluid (e.g., a coolant or working
fluid) from a heating system enters the inlet header 32 of the heat
exchanger 10 through the first-fluid inlet port 60 of the second
support plate 18. The working fluid travels radially inwardly in a
counter flow direction to the flow of the combustion gasses from
the outermost concentric fluid passage 108 through the
interconnecting passage 112 (and intervening concentric fluid
passage ways, if any,) to the innermost concentric passage way 110
and into the outlet fluid header 34. The working fluid exits the
heat exchanger 10 through the first-fluid outlet port 62 in the
second support plate 18 and returns to the heating system.
[0048] As the combustion gas and the working fluid cross-flow
through the heat assembly 14, water vapor in the combustion
products condenses. The latent heat released during condensation
transfers to the plurality of heat exchanger elements 100
increasing the temperature of the working fluid. The condensate
drops to the bottom of the outer wrapper 12 and exits the heat
exchanger 10 through the condensate drain 28 in the outer wrapper
12.
[0049] The transfer of energy to the working fluid and the rise in
the temperature of the working fluid is diagrammatically
represented by the change in the stippling of the working fluid
from lightly stippled (a relatively cool inlet temperature) to more
heavily stippled (a relatively hot outlet temperature) as the
working fluid flows radially inwardly from the outer passage 108 to
the inner passage 110.
[0050] In typical combustion system applications, the following
operation conditions may occur. The maximum internal pressure may
be 160 psig and the maximum temperature may be 210-250.degree. F.
The liquid flow rates may vary with inlet rate to develop a
10-100.degree. F. temperature difference across the heat exchanger.
The gas flow rates are sufficient to provide reasonable combustion
at rated inlet (Gas CFH.times.9.5.times.1.5). Combustion side
pressure is usually less than 14 in of water but could be more.
[0051] The above disclosed embodiments may be modified to
accommodate a wide range of operating conditions more or less
demanding than the conditions set forth above. For example, in some
embodiments, the number of heat exchanger elements may be increased
or decreased to accommodate greater or lesser thermal loads.
Further, the elements may be designed to have more or less passages
(having a concentric or other circumscribing shape) to allow
scaling of the design to larger or smaller sizes. Still further,
although the embodiments disclosed above were directed to
combustion systems, the heat exchanger 10 is not limited to
combustion application. Rather, the heat exchanger 10 may be
implemented in various embodiments suitable for use in instances
where there is a desire to capture the latent energy associated
with the condensation of one or more vapors in a gas stream or,
stated more generally for non-condensing applications to capture
some of the thermal energy in a gas stream. Therefore, the
invention disclosed above is not limited to the particular
embodiments or applications disclosed. Rather, the disclosure is
intended to cover modifications within the spirit and scope of the
present invention as defined by the appended claims.
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