U.S. patent application number 13/877533 was filed with the patent office on 2013-09-05 for heat exchanger.
This patent application is currently assigned to JOHNSON & STARLEY LIMITED. The applicant listed for this patent is Tim Cooper, Tom Dee, Glenn Page, Ian Williams, Ken Worthing. Invention is credited to Tim Cooper, Tom Dee, Glenn Page, Ian Williams, Ken Worthing.
Application Number | 20130228318 13/877533 |
Document ID | / |
Family ID | 43243468 |
Filed Date | 2013-09-05 |
United States Patent
Application |
20130228318 |
Kind Code |
A1 |
Williams; Ian ; et
al. |
September 5, 2013 |
HEAT EXCHANGER
Abstract
A condensing heat exchanger of the kind having a primary heat
exchanger and a secondary heat exchanger connected downstream of
and in series with the primary heat exchanger. The secondary heat
exchanger is arranged to at least partially condense combustion
gases discharged from the primary heat exchanger. The primary heat
exchanger comprising a drum having a longitudinal axis and the
secondary heat exchanger comprising a plurality of small diameter
tubes arranged by the side of the drum and extending parallel with
the longitudinal axis of the drum.
Inventors: |
Williams; Ian; (Northampton,
GB) ; Page; Glenn; (Northampton, GB) ; Cooper;
Tim; (Northampton, GB) ; Worthing; Ken;
(Northampton, GB) ; Dee; Tom; (Northampton,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Williams; Ian
Page; Glenn
Cooper; Tim
Worthing; Ken
Dee; Tom |
Northampton
Northampton
Northampton
Northampton
Northampton |
|
GB
GB
GB
GB
GB |
|
|
Assignee: |
JOHNSON & STARLEY
LIMITED
Northampton
GB
|
Family ID: |
43243468 |
Appl. No.: |
13/877533 |
Filed: |
October 4, 2011 |
PCT Filed: |
October 4, 2011 |
PCT NO: |
PCT/GB2011/051881 |
371 Date: |
April 30, 2013 |
Current U.S.
Class: |
165/157 ;
165/177; 29/890.03 |
Current CPC
Class: |
F28F 9/04 20130101; F28F
1/105 20130101; Y02B 30/102 20130101; Y10T 29/4935 20150115; F24H
9/0026 20130101; Y02B 30/00 20130101; F28D 1/05333 20130101; F28F
9/16 20130101; B21D 53/02 20130101; F24H 8/00 20130101; F28D 7/1653
20130101; F28F 9/00 20130101; F28F 1/006 20130101; F28F 9/26
20130101; F28F 2225/02 20130101; F28F 1/36 20130101; F28D 21/0007
20130101; F28F 1/426 20130101; F28F 2275/122 20130101; F28F 2265/28
20130101; F24H 1/26 20130101; F24H 1/36 20130101; F28D 7/0083
20130101; F28F 2210/06 20130101; F24H 1/44 20130101 |
Class at
Publication: |
165/157 ;
165/177; 29/890.03 |
International
Class: |
F24H 8/00 20060101
F24H008/00; F28F 1/10 20060101 F28F001/10; B21D 53/02 20060101
B21D053/02; F28D 1/053 20060101 F28D001/053 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 4, 2010 |
GB |
1016673.4 |
Claims
1. A condensing heat exchanger of the kind having a primary heat
exchanger and a secondary heat exchanger connected downstream of
and in series with the primary heat exchanger, in which the
secondary heat exchanger is arranged to at least partially condense
combustion gases discharged from the primary heat exchanger,
wherein the primary heat exchanger comprises a drum having a
longitudinal axis and the secondary heat exchanger comprises a
plurality of tubes, wherein each tube has a longitudinal axis and
an outer surface which includes a spiral formation concentric with
the longitudinal axis of the tube, and wherein the tubes are
arranged to extend parallel with the longitudinal axis of the
drum.
2. (canceled)
3. A condensing heat exchanger according to claim 1 wherein the
spiral formation begins at a predetermined distance from one end of
the tube and stops at a predetermined distance from the opposite
end of the tube, so that the ends of the tube are plain.
4. A condensing heat exchanger according to claim 1 wherein the
tubes have a diameter in the range of approximately 4 mm to 8
mm.
5. (canceled)
6. A condensing heat exchanger according to claim 1 wherein the
tubes are provided between inlet and outlet plates, as a
subassembly of the heat exchanger.
7. A condensing heat exchanger according to claim 6 wherein the
inlet plate and outlet plate are preformed with tube apertures for
receiving the ends of the tubes in a pre-defined array.
8. A condensing heat exchanger according to claim 7 wherein each
tube aperture has a peripheral flange to provide a sleeve for
receiving part of the length of a respective tube.
9. A condensing heat exchanger according to claim 1 wherein the
primary heat exchanger comprises a subassembly including a
cylindrical drum sealingly attached to an outlet plate; wherein the
secondary heat exchanger comprises a subassembly including said
plurality of tubes sealing attached to an inlet plate; and wherein
the two subassemblies are united with one another by attachment
between the outlet plate and inlet plate.
10. A condensing heat exchanger according to claim 9, further
including a closure for connecting the two subassemblies and
defining a passageway for combustion gases to be channelled from
the primary heat exchanger to the secondary heat exchanger.
11. A condensing heat exchanger according to claim 10 wherein the
closure has a box-type configuration with four side walls and a
base wall, wherein the base wall has a pressed configuration in
which an outer surface of the base wall extends outwardly.
12. A condensing heat exchanger according to claim 10, further
including an array of concentric circles press-formed into a major
surface of the closure.
13. A method of assembling a condensing heat exchanger of the kind
having a primary heat exchanger and a secondary heat exchanger
connected downstream of and in series with the primary heat
exchanger, and in which the secondary heat exchanger is arranged to
at least partially condense combustion gases discharged from the
primary heat exchanger, comprising the steps of: providing the
primary heat exchanger in the form of a drum having a longitudinal
axis, providing the secondary heat exchanger in the form of a
plurality of tubes, and providing an inlet plate and an outlet
plate for the tubes, the inlet and outlet plates being preformed
with tube apertures for receiving the ends of the tubes in a
pre-defined array, wherein the method further includes the steps of
arranging the plates in a spaced array with said tubes arranged
between the plates with the tubes in alignment with the tube
apertures, and forcing the ends of the tubes into the respective
tube apertures by driving the plates in the direction of one
another, and then arranging the tubes to extend parallel with the
longitudinal axis of the drum.
14. (canceled)
15. A method according to claim 14 wherein each tube aperture is
provided with a peripheral flange projecting from the associated
plate to provide a sleeve for part of the length of a respective
tube.
16. A method according to claim 15 wherein the peripheral flange is
swaged to fixedly couple the flange to the tubes.
17. A method according to claim 13 wherein a spiral thread is
formed in the outer surface of each tube prior to incorporation in
the assembly.
18. A method according to claim 17 wherein each tube is drawn and
then the spiral thread is formed on the drawn tube, prior to a
second drawing operation, to remove any significant deformations
generated when the thread is formed.
19. A method according to claim 13 wherein: the primary heat
exchanger is formed as a subassembly including a cylindrical drum
sealingly attached to an outlet plate; the secondary heat exchanger
is formed as a separate subassembly including said plurality of
tubes sealing attached to an inlet plate; and the two subassemblies
are united with one another by attachment between the outlet plate
and inlet plate.
20. A method according to claim 19 wherein a closure is attached to
the united subassemblies to define a passageway for combustion
gases to be channelled from the primary heat exchanger to the
secondary heat exchanger.
21. A method according to claim 20 wherein an array of concentric
circles is pressed into a surface of the closure to reduce noise
during flexure of the closure under thermal expansion.
22. A method according to claim 20 wherein the closure is of
pre-formed box-type configuration having four side walls and a base
wall, wherein the base wall is pressed outwards, to reduce noise
during flexure of the closure under thermal expansion.
Description
[0001] This disclosure relates to a heat exchanger, more
particularly a condensing type heat exchanger. The disclosure also
relates to a method of assembling a heat exchanger, more
particularly a condensing type heat exchanger.
[0002] A known fuel-fired forced air heat exchanger is set forth in
U.S. Pat. No. 4,960,102. The heat exchanger includes a primary heat
exchanger and a secondary heat exchanger connected downstream of
and in series with the primary heat exchanger. Advantageously, the
secondary heat exchanger is arranged to condense the combustion
gases discharged from the primary heat exchanger, and so capture
latent heat from the available combustion gas. Such heat exchangers
are commonly referred to as "condensing" heat exchangers.
[0003] The increasing cost of fuel and materials means that there
is a need to improve the heating efficiency and assembly of such
heat exchangers.
[0004] According to one aspect of the invention, there is provided
a condensing heat exchanger of the kind having a primary heat
exchanger and a secondary heat exchanger connected downstream of
and in series with the primary heat exchanger, in which the
secondary heat exchanger is arranged to at least partially condense
combustion gases discharged from the primary heat exchanger,
wherein the primary heat exchanger comprises a drum having a
longitudinal axis and the secondary heat exchanger comprises a
plurality of tubes extending parallel with the longitudinal axis of
the drum.
[0005] In exemplary embodiments, the tubes are provided in an array
adjacent, e.g. to the side of, the drum.
[0006] In exemplary embodiments, a spiral formation is formed in
the outer surface of each tube, for promoting flow of combustion
gases through the tube.
[0007] In exemplary embodiments, the spiral formation begins at a
predetermined distance from one end of the tube and stops at a
predetermined distance from the opposite end of the tube, so that
the ends of the tube are plain.
[0008] In exemplary embodiments, the tubes have a small diameter
relative to the diameter of the drum.
[0009] In exemplary embodiments, the tubes have a diameter in the
range 4 mm to 8 mm. In another embodiment the tubes have a diameter
in the range 5 mm to 7 mm. In a further embodiment the tubes have a
diameter of 6 mm.
[0010] In exemplary embodiments, the tubes are arranged in
staggered rows.
[0011] In exemplary embodiments, the tubes are provided between
inlet and outlet plates, as a subassembly.
[0012] In exemplary embodiments, the inlet and/or outlet plates are
preformed with tube apertures for receiving the ends of the tubes
in a pre-defined array.
[0013] In exemplary embodiments, the tube apertures have a
peripheral flange projecting from the associated plate to provide a
sleeve for a section of the tubes.
[0014] In exemplary embodiments, the primary heat exchanger
consists of a subassembly including a cylindrical drum sealingly
attached to an outlet plate; wherein the secondary heat exchanger
consists of a subassembly including said plurality of tubes sealing
attached to an inlet plate; and wherein the two subassemblies are
united with one another by attachment between the outlet plate and
inlet plate.
[0015] In exemplary embodiments, a closure is attached to the
united subassemblies and defines a passageway for combustion gases
from the primary heat exchanger to the secondary heat
exchanger.
[0016] In exemplary embodiments, an array of concentric circles
pressed into a surface of the closure to reduce noise during
flexure of the closure under thermal expansion.
[0017] In exemplary embodiments, the closure is of box-type
configuration having four side walls and a base wall, wherein the
base wall is pressed outwards, to extend beyond the side walls, and
defines four generally triangular sloping surfaces.
[0018] According to another aspect of the invention, there is
provided a method of assembling a condensing heat exchanger of the
kind having a primary heat exchanger and a secondary heat exchanger
connected downstream of and in series with the primary heat
exchanger, and in which the secondary heat exchanger is arranged to
at least partially condense combustion gases discharged from the
primary heat exchanger, comprising the steps of: [0019] providing
the primary heat exchanger in the form of a drum having a
longitudinal axis, and providing the secondary heat exchanger in
the form of a plurality of tubes extending parallel with the
longitudinal axis of the drum.
[0020] In exemplary embodiments, the method includes the step of
providing an inlet plate and an outlet plate for the tubes, the
inlet and outlet plates being pre-formed with tube apertures for
receiving the ends of the tubes in a pre-defined array, arranging
the plates in a spaced array with said tubes arranged between the
plates with the tubes in alignment with the tube apertures, and
driving the plates together in the direction of one another to
force the ends of the tubes into the respective tube apertures.
[0021] In exemplary embodiments, each tube aperture is provided
with a peripheral flange projecting from the associated plate to
provide a sleeve for a section of a respective tube.
[0022] In exemplary embodiments, the peripheral flange is swaged to
fixedly couple the flange to the tubes.
[0023] In exemplary embodiments, a spiral thread is formed in the
outer surface of each tube prior to incorporation in the
assembly.
[0024] In exemplary embodiments, each tube is drawn and then the
spiral thread is formed on the drawn tube, prior to a second
drawing operation, to remove any significant deformations generated
when the thread is formed.
[0025] In exemplary embodiments, the primary heat exchanger is
formed as a subassembly including a cylindrical drum sealingly
attached to an outlet plate; the secondary heat exchanger is formed
as a separate subassembly including said plurality of tubes sealing
attached to an inlet plate; and the two subassemblies are united
with one another by attachment between the outlet plate and inlet
plate.
[0026] In exemplary embodiments, a closure is attached to the
united subassemblies to define a passageway for combustion gases
from the primary heat exchanger to the secondary heat
exchanger.
[0027] In exemplary embodiments, an array of concentric circles
pressed into a surface of the closure to reduce noise during
flexure of the closure under thermal expansion.
[0028] In exemplary embodiments, the closure is of pre-formed
box-type configuration having four side walls and a base wall,
wherein the base wall is pressed outwards, to extend beyond the
side walls, and defines four generally triangular sloping
surfaces.
[0029] In a further aspect of the invention, there is provided a
condensing heat exchanger of the kind having a primary heat
exchanger and a secondary heat exchanger connected downstream of
and in series with the primary heat exchanger, in which the
secondary heat exchanger is arranged to at least partially condense
combustion gases discharged from the primary heat exchanger,
wherein the primary heat exchanger comprises a drum having a
longitudinal axis and the secondary heat exchanger comprises a
plurality of tubes extending parallel with the longitudinal axis of
the drum, wherein a spiral formation is formed in the outer surface
of each tube, for promoting flow of combustion gases through the
tube.
[0030] Other aspects and features of the invention will be apparent
from the attached claims and the following description of preferred
embodiments, made by way of example only, with reference to the
accompanying drawings, in which:
[0031] FIG. 1 is a schematic perspective view of an outlet plate
for a secondary heat exchanger;
[0032] FIG. 2 is an enlarged view of encircled region A from FIG.
1;
[0033] FIG. 3 is a schematic perspective view of an inlet plate for
a secondary heat exchanger;
[0034] FIG. 4 is an enlarged view of encircled region B from FIG.
3;
[0035] FIG. 5 is a schematic perspective view of a secondary heat
exchanger subassembly incorporating the inlet and outlet plates of
FIGS. 1 and 3;
[0036] FIG. 6A is schematic side view of a heat exchanger tube for
use in the subassembly of FIG. 5;
[0037] FIG. 6B is an enlarged view of encircled region C from FIG.
6A;
[0038] FIG. 6C is schematic cross-section through the heat
exchanger tube of FIG. 6A;
[0039] FIG. 7 is a schematic perspective view of a primary heat
exchanger subassembly;
[0040] FIG. 8 is a schematic perspective view showing the
pre-assembly formed when the subassembly of FIG. 5 is united with
the subassembly of FIG. 7;
[0041] FIG. 9 is a schematic perspective view of the pre-assembly
of FIG. 8 prior to attachment of a cover element to provide a
passageway between the primary heat exchanger and the secondary
heat exchanger;
[0042] FIG. 10A is schematic side view of the closure from FIG. 9;
and
[0043] FIG. 10B is cross-sectional view of the closure from FIG.
10A taken along line D-D.
[0044] Referring firstly to FIG. 1, there is shown a plate 10 of
rectangular form. The plate includes an array of primary fixing
apertures 12 arranged about the periphery of the plate 10, e.g. one
at each corner 14 of the plate 10 and one positioned mid way along
each of the two longest sides 16 of the plate 10. The plate 10 also
includes a plurality of secondary fixing apertures 18 arranged in
two rows, each row being spaced inwardly of the primary fixing
apertures 12 and extending in a direction parallel with the
respective longest sides 16 of the plate 10.
[0045] The plate 10 further includes an array of tube apertures 20
arranged centrally on the plate 10 in a plurality of rows extending
in a direction parallel with line the longest sides 16 of the plate
10. Adjacent rows in the array of tube apertures 20 are staggered
relative to one another, e.g. so that the apertures do not align in
a transverse direction relative to the longest sides of the plate.
The tube apertures 20 are formed by a punching operation and so
define a peripheral flange 22 which projects upwardly from the
upper surface 24 of the plate 10, as viewed in FIG. 1 (and as seen
most clearly in FIG. 2).
[0046] Plate 10 is preformed to the configuration shown in FIG. 1,
ready for use as an outlet plate 10 for a secondary heat exchanger
assembly according to an exemplary embodiment of the invention. As
can be seen, the edges 26 of the plate 10 are turned to project
downwardly as viewed in FIG. 1, to form an open box type structure
(as would be apparent if viewed from below in FIG. 1).
[0047] Referring now to FIG. 3 there is a shown a plate 30 of
rectangular form, and including three fixing apertures 32 arranged
at predetermined locations along one of the longer sides 34 of the
plate 30.
[0048] Plate 30 also includes an array of tube apertures 36
arranged centrally on the plate 30 in a plurality of rows extending
parallel with the longest sides 34 of the plate 10. Again, adjacent
rows in the array of tube apertures 36 are staggered relative to
one another. The tube apertures 36 are formed by a punching
operation and so define a peripheral flange 38 which projects
downwardly from the lower surface 40 of the plate 30, as viewed in
FIG. 3 (and as seen most clearly in FIG. 4).
[0049] Plate 30 is pre-formed to the configuration shown in FIG. 3,
ready for use as an inlet plate 30 for a secondary heat exchanger
according to an exemplary embodiment of the invention.
[0050] Unlike the plate 10 in FIG. 1, plate 30 does not include
turned edges. However, the position of the tube apertures 36 on the
plate 30 matches the position of the tube apertures 20 on plate
10.
[0051] According to an exemplary method of assembly, the two plates
10 and 30 are arranged in a spaced array with a plurality of
stainless steel heat exchanger tubes 50 arranged therebetween, e.g.
as shown in FIG. 5. The plates 10 and 30 and tubes 50 are arranged
with the tubes 50 in alignment with the tube apertures 20, 36, e.g.
using a special purpose assembly machine. The plates 10 and 30 are
then moved in the direction of one another, to force the ends of
the tubes 50 into the respective tube apertures 20, 36. The
diameter of the tube apertures 20, 36 is selected to create an
interference fit between the associated flanges 22, 38 and the
respective ends of the tubes 50. In an exemplary method of
assembly, a swaging tool (not shown) may be used to swage the ends
of the tubes 50 in the flanges 22, 38 to securely couple the tubes
50 to the inlet/outlet plates 12, 30. The two ends may be swaged
simultaneously, to reduce process time.
[0052] An example of a heat exchanger tube 50 for use in the
secondary heat exchanger assembly and method of assembly described
above is shown in FIG. 6. The tube 50 is of seamless drawn
construction, having a predefined outer diameter (for providing on
an interference fit with the flanges 22, 38 on the plates 10, 30)
and a predefined internal diameter. In exemplary embodiments, the
tubes 50 are of small diameter.
[0053] Test results have shown a 6 mm diameter bore to provide
beneficial performance characteristics. In exemplary embodiments,
the diameter of the tubes is within the range 4 mm to 8 mm.
[0054] A spiral thread 52 is provided as a recessed formation in
the outer surface of the tube 50. The configuration of the thread
52 (in terms of pitch and depth relative to the length of the tube)
is configured to promote the flow of combustion gases though the
tube 50, in use.
[0055] Test results show that a pitch of the spiral formation in
the region of 6-12 mm (e.g.12 mm), at a depth of 0.69-0.7 mm, with
a wall thickness of 0.5.+-.0.03 mm provides optimum strength and
heat transfer characteristics for exemplary embodiments.
[0056] In exemplary embodiments, the tube 50 is drawn and then the
spiral thread 52 is formed on the drawn tube 50. A second drawing
operation is then carried out to remove any significant
deformations generated when the thread is formed, so as to maintain
the accuracy of the tube diameter axial alignment, to promote
optimum performance and avoid condensate being trapped within the
tube.
[0057] The spiral thread 52 does not extend to the ends 54 of the
tube 50; the thread 52 begins at a predetermined distance from one
end 54 of the tube 50 and stops at a predetermined distance before
the opposite end 54 of the tube 50, so that the ends 54 of the tube
are plain, to ensure a tight fit with the tube apertures 20, 36 on
the plates 10, 30.
[0058] A primary heat exchanger assembly 60 according to an
exemplary embodiment of the invention will now be described with
reference to FIG. 7.
[0059] The primary heat exchanger assembly 60 has a cylindrical
drum 62 of pre-selected diameter. An outlet plate 64 having a
central outlet aperture 66 is fitted to the lower end of the drum
62, as viewed in FIG. 7, and affixed thereto (e.g. by seam welding
to a peripheral flange 68) to form an airtight seal with the drum
62.
[0060] An inlet assembly 70 is fitted to the upper end of the drum
62, with a thermal insulation plate 72 fixed in place beneath the
inlet assembly 70. The inlet assembly 70 affixed to the drum (e.g.
by seam welding to a peripheral flange 68) to form an airtight seal
with the drum 62.
[0061] X-type strengthening formations 74 are formed adjacent each
of the corners 76 of the outlet plate 64. These serve as
strengthening braces and also allow the material to move during the
expansion and contraction cycles. Allowing the material to move
eliminates noise issues which would otherwise result, such as
`bonging` and `ticking`, due to the different expansion rates of
the mating materials.
[0062] Referring now to FIG. 8, it can be seen that the primary and
secondary heat exchanger assemblies 60, 40 form separate sub
assemblies of a condensing heat exchanger according to an exemplary
embodiment of the invention. The two sub assemblies 60, 40 are then
brought together (e.g. using a mechanical jig) and attached to one
another. In the illustrated embodiment, the two assemblies 60, 40
are affixed to one another by a seam weld 78 formed between
respective edges regions of the outlet plate 64 of the primary heat
exchanger assembly 60 and the inlet plate 30 of the secondary heat
exchanger assembly 40.
[0063] As can be seen from FIG. 9, a box closure 80 is then be
applied over the lower end of the united sub assemblies 40, 60. The
box closure 80 includes a peripheral flange 82 and a seam weld is
used to affix united plates 30, 64 to the peripheral flange 82, and
create an airtight seal between the closure 80 and the united sub
assemblies 40, 60.
[0064] FIGS. 10A and 10B show a box closure 80 of exemplary
configuration, having side walls 84 and a base wall 86. An array of
concentric circles 88 is pressed into the base wall 86 (on the
outer side of the box 80). The base wall 80 is then pressed
outwards, to extend beyond the side walls 84 (e.g. as viewed in
FIG. 10B), and bent so as to define four generally triangular
sloping surfaces 90. This configuration has been found to provide
reduced noise from flexure of the material (e.g. bongs and ticks)
and reduces the tendency for splitting, in use.
[0065] Once assembled, the finished assembly is ready for
incorporation in a condensing heat exchanger, e.g. with a fuel
burner (not shown) in communication with the inlet assembly 70 of
the primary heat exchanger 60, so that combustion gasses pass
through the drum 62, into the box closure 80 and out through the
tubes 50 of the secondary heat exchanger 40.
[0066] The provision of an array of small diameter tubes as the
secondary heat exchanger has been found to be particularly
effective, especially when incorporating a spiral thread and/or
when arranged in staggered rows. The arrangement of the tubes
between the pre-formed inlet and outlet plates provides a
convenient and efficient sub-assembly, which can be readily
incorporated with the primary heat exchanger sub-assembly described
herein.
* * * * *