U.S. patent application number 11/702793 was filed with the patent office on 2007-07-19 for brazed plate fin heat exchanger.
Invention is credited to David L. Davis, James R. Harris, Michael E. Heidenreich, David E. Lollar, Roger A. Loomis, Paul L. Mitchell.
Application Number | 20070163767 11/702793 |
Document ID | / |
Family ID | 34750171 |
Filed Date | 2007-07-19 |
United States Patent
Application |
20070163767 |
Kind Code |
A1 |
Mitchell; Paul L. ; et
al. |
July 19, 2007 |
Brazed plate fin heat exchanger
Abstract
A fin collar having a shape that enhances flux application and
brazing clad flow into the tube to fin joint to provide an improved
thermal and structural bond.
Inventors: |
Mitchell; Paul L.; (Scobey,
MS) ; Heidenreich; Michael E.; (Grenada, MS) ;
Loomis; Roger A.; (Hernando, MS) ; Harris; James
R.; (Grenada, MS) ; Davis; David L.; (Grenada,
MS) ; Lollar; David E.; (Grenada, MS) |
Correspondence
Address: |
HODGSON RUSS LLP;THE GUARANTY BUILDING
140 PEARL STREET
SUITE 100
BUFFALO
NY
14202-4040
US
|
Family ID: |
34750171 |
Appl. No.: |
11/702793 |
Filed: |
February 6, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10761448 |
Jan 20, 2004 |
|
|
|
11702793 |
Feb 6, 2007 |
|
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Current U.S.
Class: |
165/182 |
Current CPC
Class: |
F28F 2275/04 20130101;
F28F 21/084 20130101; F28F 21/085 20130101; F28F 2275/125 20130101;
F28F 1/32 20130101 |
Class at
Publication: |
165/182 |
International
Class: |
F28F 1/30 20060101
F28F001/30 |
Claims
1. A heat exchanger, comprising: at least one plate fin having a
first side, a second side, and at least one opening defined
therein; at least one fin collar disposed on the plate fin around
the at least one opening, the fin collar having an upstanding wall
extending from the plate fin, the wall having a plurality of slits
defined therein; and, at least one tube for conveying a pressurized
fluid, the tube being disposed through the at least one opening in
the plate fin.
2. The heat exchanger of claim 1, wherein the at least one tube has
a cross-sectional shape that is round.
3. The heat exchanger of claim 1, wherein the at least one tube has
a cross-sectional shape that is circular.
4. The heat exchanger of claim 1, wherein the at least one tube has
a cross-sectional shape that is oval.
5. The heat exchanger of claim 1, wherein the plurality of slits
are disposed substantially equidistantly around a perimeter of the
collar.
6. The heat exchanger of claim 1, wherein the plurality of slits
are defined by a pair of opposed walls that are angled such that
the slit is wider at a point distal to the plate fin than it is at
a point proximal to the plate fin.
7. The heat exchanger of claim 1, wherein the plurality of slits
have a rectangular shape.
8. The heat exchanger of claim 1, wherein the at least one fin
collar is constructed of an aluminum alloy.
9. The heat exchanger of claim 8, further comprising a cladding
layer.
10. The heat exchanger of claim 1, wherein the at least one tube is
constructed of an aluminum alloy.
11. The heat exchanger of claim 1, wherein the at least one plate
fin is attached to the at least one tube by brazing.
12. The heat exchanger of claim 1, wherein the at least one plate
fin is attached to the at least one tube by brazing in a controlled
atmosphere brazing oven.
13. The heat exchanger of claim 1, wherein the at least one tube is
constructed of copper.
14. The heat exchanger of claim 1, wherein the at least one plate
fin is constructed of copper.
15. The heat exchanger of claim 1, wherein the fin collar is
unclad.
16. A heat exchanger, comprising: at least one plate fin having a
first side, a second side and at least one opening defined therein;
at least one fin collar disposed on the plate fin around the at
least one opening, the fin collar having an upstanding wall
extending from the plate fin, the wall having a plurality of slits
defined therein; and, at least one tube for conveying a pressurized
fluid, the tube being disposed through the opening in the plate fin
and attached to the fin collar by brazing.
17. The heat exchanger of claim 16, wherein the at least one tube
has a cross-sectional shape that is round.
18. The heat exchanger of claim 16, wherein the at least one tube
has a cross-sectional shape that is circular.
19. The heat exchanger of claim 16, wherein the at least one tube
has a cross-sectional shape that is oval.
20. The heat exchanger of claim 16, wherein the plurality of slits
are disposed substantially equidistantly around a perimeter of the
collar.
21. The heat exchanger of claim 16, wherein the plurality of slits
are defined by a pair of opposed walls that are angled such that
the slit is wider at a point distal to the plate fin than it is at
a point proximal to the plate fin.
22. The heat exchanger of claim 16, wherein the plurality of slits
have a rectangular shape.
23. The heat exchanger of claim 16, wherein the at least one fin
collar is constructed of an aluminum alloy.
24. The heat exchanger of claim 23, further comprising a cladding
layer.
25. The heat exchanger of claim 16, wherein the at least one tube
is constructed of an aluminum alloy.
26. The heat exchanger of claim 16, wherein the at least one fin
collar is attached to the at least one tube by brazing.
27. The heat exchanger of claim 16, wherein the at least one plate
fin is attached to the at least one tube by brazing in a controlled
atmosphere brazing oven.
28. The heat exchanger of claim 16, wherein the at least one tube
is constructed of copper.
29. The heat exchanger of claim 16, wherein the at least one plate
fin is constructed of copper.
30. The heat exchanger of claim 16, wherein the fin collar is
unclad.
31. A method of forming a plate fin heat exchanger, comprising:
providing at least one plate fin having a first side, a second
side, and at least one opening; at least one fin collar disposed on
the plate fin around the at least one opening, the fin collar
having an upstanding wall extending from the plate fin, the wall
having a plurality of slits defined therein; and at least one tube
for conveying a pressurized fluid, the tube being disposed through
the at least one opening and attached to the fin collar by brazing;
providing a cladding material for brazing the plate fin-to-tube
joint; and, brazing the plate fin-to-tube joint in a controlled
atmosphere brazing oven.
Description
PRIOR RELATED APPLICATION
[0001] The present application is a continuation application based
on U.S. patent application Ser. No. 10/761,448 filed Jan. 20,
2004.
FIELD OF INVENTION
[0002] This invention is directed to heat exchanger fin collars,
and more particularly to an improved fin collar for use in a brazed
plate fin heat exchanger.
BACKGROUND OF THE INVENTION
[0003] Plate fin and tube heat exchangers are used in a wide
variety of applications including, but not limited to, air
conditioning and refrigeration where it is desired to exchange heat
between two fluids, usually a pure liquid or a liquid undergoing a
phase change to or from a gas, flowing in the heat exchanger tubes
and a gas, usually air, flowing around the heat exchanger plate
fins and tube exteriors. In such a heat exchanger, a plurality of
thin plate fins are arranged parallel to each other between two
tube sheets. Heat exchanger tubes pass through holes in the tube
sheets and plate fins. There is a firm fit between the tubes and
the plate fins so that the effective surface area, and thus the
heat transfer area, of the heat exchanger tubes is increased by the
area of the plate fins. Because of this increase in surface area, a
plate fin and tube heat exchanger offers improved heat transfer
performance over a plain tube type heat exchanger of the same
size.
[0004] A common method of manufacturing this type of heat exchanger
is to first assemble a plurality of plate fins between two tube
sheets, then lace a plurality of hair pin tubes through selected
holes in the plate fins and similar holes in each of the tube
sheets. Next, bells are formed in the end of hairpin tubes, then
the legs of the tubes are expanded to insure a tight mechanical fit
between the tubes and plate fins.
[0005] In order to improve the thermal and structural bond
resulting from mechanical joining of the tubes and plate fins,
there is a need for a brazed plate fin heat exchanger with an
improved braze joint at the tube-to-fin joint.
SUMMARY OF THE INVENTION
[0006] The present invention meets the above-described need by
providing a fin collar having a shape that enhances flux
application and brazing clad flow into the tube-to-fin joint to
provide an improved thermal and structural bond.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] The invention is illustrated in the drawings in which like
reference characters designate the same or similar parts throughout
the figures of which:
[0008] FIG. 1 is a perspective view of a plate fin heat exchanger
of the present invention;
[0009] FIG. 2 is a perspective view of a tube of the present
invention disposed through several plate fins;
[0010] FIG. 3 is a perspective view of a fin collar of the present
invention;
[0011] FIG. 4 is a perspective view of an alternate embodiment of
the fin collar of the present invention;
[0012] FIG. 5 is a perspective view of another alternate embodiment
of the fin collar of the present invention;
[0013] FIG. 6 is a perspective view of the fin collar of the
present invention shown with a representation of the air flow over
the collar; and,
[0014] FIG. 7 is a top plan view of the fin collar of FIG. 6.
DETAILED DESCRIPTION
[0015] FIG. 1 depicts a plate fin and tube heat exchanger 10
containing plate fins 12 that embody the present invention. Each
plate fin has a plurality of holes 16. A common method of
manufacturing heat exchanger 10 is to first assemble a plurality of
plate fins 12 between two tube sheets 18, then lace a plurality of
hairpin tubes 20 through selected holes 16 in the plate fins 12 and
similar holes 16 in each of tube sheets 18. The heat exchanger
assembly is completed by fitting up a plurality of return bends 22
to the ends of hairpin tubes 20 so as to form one or more closed
fluid flow paths through the tubes of the heat exchanger.
[0016] When installed and operating in a device such as an air
conditioner, a first fluid, such as a refrigerant, flows through
heat exchanger 10 via a fluid flow path or paths defined by
interconnected hairpin tubes 20 and return bends 22. A second
fluid, such as air, flows over and around plate fins 12 and tubes
20. If there is a temperature differential between the two fluids,
then heat transfer from the warmer to the cooler of the two takes
place through the tube walls and plate fins.
[0017] Turning to FIG. 2, a single tube 20 is shown disposed
through a plurality of plate fins 12. Each plate fin 12 is provided
with an upstanding fin collar 30 disposed around the openings 16.
As shown, the collar 30 may be curved so that a convex surface 31
faces the tube 20. The number of plate fins 12 that can be placed
around the tube 20 is determined by the height of the collar
30.
[0018] In order to manufacture the heat exchanger of the present
invention, the tube 20 to fin 12 joint is brazed in a controlled
atmosphere braze furnace. The brazing temperatures will range
between 1070.degree. F. and 1120.degree. F. depending on the clad
used.
[0019] The tube 20 may be constructed of an aluminum alloy that is
clad or unclad. The tube 20 may be roll formed with a welded seam
or a lock seam. As an alternative, the tube 20 may be extruded. The
tube 20 may have a wall thickness of 0.016'' to 0.05'' depending on
the tube diameter and the working pressure. The tube 20 may have a
cross-sectional shape that is round, circular, oval, or the like.
The tube material is a long life, high strength, corrosion
resistant alloy. For extruded tubes, a 3003 aluminum alloy may be
used. For roll formed tube an Alcan X-1000 may be used. The clad
alloys may be 4045 or 4343 aluminum alloys.
[0020] The fins 12 and fin collar 30 may be constructed out of an
aluminum alloy 3003 with a 4045 or 4343 alloy clad. If unclad, the
fin may be constructed from an 1100 aluminum alloy. The fins may be
constructed with a thickness of 0.003'' to 0.016''.
[0021] In addition to the aluminum alloys described above, the
present invention may be used for brazing a copper fin to copper
tubing or brazing an aluminum fin to copper tubing, as will be
evident to those of ordinary skill in the art.
[0022] In FIG. 3, a first embodiment of the fin collar 30 of the
present invention is shown. A plurality of slits 32 are disposed
around the circumference of the fin collar 30. The slits 32 may be
formed by removing material from the collar and may be disposed
equidistantly around the perimeter of the collar 30. The slit may
extend from the top 43 of the collar 30 and terminate at a point
approximately 0.02'' from the underside of the fin. The slit 32 is
defined by a pair of opposed walls 34 and 36. The walls 34 and 36
may be angled such that the width 40 across the slit 32 gradually
increases from the bottom 42 of the slit 32 to the top 43 of the
collar 30. The slit 32 may range from 0.015'' to 0.15'' in width
depending on the collar height and the number of slits. The slits
32 improve the tube-to-fin joint both thermally and
structurally.
[0023] With regard to structural properties at the joint, the fin
collar 30 of the present invention enhances the flux application
and the brazing clad flow because the slits 32 allow the cladding
to flow through on both sides of the collar 30.
[0024] With regard to heat transfer performance, the split fin
collar 30 increases heat transfer between the air and tube
surfaces. The slits 32 open access to a portion of the surface of
the primary tube 20 for the air flow allowing direct heat transfer
from air to the tube 20 without the resistance from secondary
sources. Ordinarily these portions of the primary tube 20 would be
covered by a solid fin collar.
[0025] Turning to FIG. 4, an alternate embodiment of the fin collar
of the present invention is shown. Fin collar 40 has a
rectangular-shaped slit 42. The slit 42 is defined by a bottom wall
44 and opposed side walls 46 and 48. The bottom wall 44 may extend
to a point approximately 0.02'' from the underside of the fin 12.
The collars 40 may have a curvature such that they have a convex
shape on the side that faces the tubes 20.
[0026] In FIG. 5, another alternate embodiment of the fin collar of
the present invention is shown. Fin collar 60 is elongated in the
longitudinal (tube axis) direction. The collar 60 has a plurality
of slits 62 defined therein. The slits 62 also have a rectangular
shape and are defined by a bottom wall 64 and a pair of opposed
side walls 66, 68. The bottom wall 64 may extend to a point
approximately 0.02'' from the underside of the fin 12.
[0027] In FIGS. 6 and 7, the fin collar 30 of the present invention
is shown with arrows 70 representing air flow around the collar 30
during use. The shape of the fin collar 30 provides interruptions
around the circumference of the fin collar 30 perpendicular to air
flow. The interruptions will provide turbulence, which is indicated
by curved lines 80, in the boundary layer of air along the fin
collar 30 which will increase the rate of heat transfer between the
air and the tube 20. The increased turbulence will also occur
around the area near the base of the fin collar 30 in the area of
highest fin efficiency, increasing heat transfer rates in that
area.
[0028] While the invention has been described in connection with
certain embodiments, it is not intended to limit the scope of the
invention to the particular forms set forth, but, on the contrary,
it is intended to cover such alternatives, modifications, and
equivalents as may be included within the spirit and scope of the
invention as defined by the appended claims.
* * * * *