U.S. patent application number 12/478643 was filed with the patent office on 2010-12-09 for firetube heat exchanger.
This patent application is currently assigned to Rocky Research. Invention is credited to Paul Sarkisian, Nicholas Tranquilli.
Application Number | 20100307729 12/478643 |
Document ID | / |
Family ID | 43262945 |
Filed Date | 2010-12-09 |
United States Patent
Application |
20100307729 |
Kind Code |
A1 |
Sarkisian; Paul ; et
al. |
December 9, 2010 |
FIRETUBE HEAT EXCHANGER
Abstract
A firetube having an elongated cylindrical shell is
characterized by a plurality of circular rows of elongated U-shaped
fins, each having a bottom surface, preferably curved along a
radius or flat, secured to the inner surface of the cylindrical
shell and two flat, planar, preferably parallel sides extending
upwardly from the bottom surface, with the fins in each row aligned
substantially parallel along the axis of the cylindrical shell.
Inventors: |
Sarkisian; Paul; (Boulder
City, NV) ; Tranquilli; Nicholas; (Henderson,
NV) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET, FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Assignee: |
Rocky Research
Boulder City
NV
|
Family ID: |
43262945 |
Appl. No.: |
12/478643 |
Filed: |
June 4, 2009 |
Current U.S.
Class: |
165/183 |
Current CPC
Class: |
F22B 37/06 20130101;
F28D 2021/0024 20130101; F28F 2215/04 20130101; F28F 13/14
20130101; F28F 1/40 20130101; F28F 13/06 20130101 |
Class at
Publication: |
165/183 |
International
Class: |
F28F 1/40 20060101
F28F001/40 |
Claims
1. A firetube heat exchanger comprising: an elongated cylindrical
shell having an inlet end and an outlet end; and a fin assembly
secured on the inner surface of said shell, said fin assembly
comprising a plurality of circular rows of elongated U-shaped fins,
each fin having a bottom surface secured to the inner surface of
said cylindrical shell and two flat, planar sides extending
upwardly from said bottom surface and defining an elongated
interior channel, wherein said fins in each row are aligned
substantially parallel along the axis of said cylindrical
shell.
2. A firetube heat exchanger of claim 1 wherein the bottom surface
of each of said fins comprises a generally flat, planar
surface.
3. A firetube heat exchanger of claim 1 wherein the bottom surface
of said fins is curved on a radius.
4. A firetube heat exchanger of claim 1 wherein the fins in each
row of fins, respectively, are substantially identical.
5. A firetube heat exchanger of claim 1 wherein the height of the
fins in the first row of fins adjacent to the inlet are lower than
the height of fins in other rows of fins.
6. A firetube heat exchanger of claim 5 comprising three or more
rows of fins and wherein the height of fins in the second row of
fins from the inlet end are higher than the fins of said first row
of fins and lower than the height of fins of one or more successive
rows of fins.
7. A firetube heat exchanger of claim 5 comprising between 2 and 20
rows of fins.
8. A firetube heat exchanger of claim 5 comprising between 4 and 12
rows of fins.
9. A firetube heat exchanger of claim 6 comprising between 4 and 12
rows of fins.
10. A firetube heat exchanger of claim 1 wherein fins of one or
more rows of fins are offset angularly from the fins of an adjacent
row of fins.
11. A firetube heat exchanger of claim 1 wherein the height of the
sides of all fins in a row of fins are equal.
12. A firetube heat exchanger of claim 1 wherein the width of all
fins in a row of fins are equal.
13. A firetube heat exchanger of claim 1 wherein the width of all
fins are equal.
14. A firetube heat exchanger of claim 11 wherein the width of all
fins are equal.
15. A firetube heat exchanger of claim 10 wherein the height of the
sides of all fins in a row of fins are equal.
16. A firetube heat exchanger of claim 10 wherein the width of all
fins in a row of fins are equal.
17. A firetube heat exchanger of claim 10 wherein the width of all
fins are equal.
18. A firetube heat exchanger of claim 13 wherein the fins of
adjacent rows of fins are offset angularly up to one-half of the
fin width.
19. A firetube heat exchanger of claim 18 wherein the height of the
sides of all fins in a row of fins are equal.
20. A firetube heat exchanger of claim 18 wherein the height of the
fins in the first row of fins adjacent to the fluid inlet are lower
than the height of fins in other rows of fins.
21. A firetube heat exchanger of claim 20 wherein the height of the
sides of all fins in a row of fins are equal.
22. A firetube heat exchanger of claim 1 wherein the length of all
fins in a row of fins are equal.
23. A firetube heat exchanger of claim 1 wherein the length of all
fins in a row are equal and the lengths of fins in two or more
different rows are different.
24. A firetube heat exchanger of claim 1 wherein the length of all
fins are equal.
25. A firetube heat exchanger of claim 24 wherein the height of the
sides of all fins in a row of fins are equal.
26. A firetube heat exchanger of claim 24 wherein the width of all
fins in a row of fins are equal.
27. A firetube heat exchanger of claim 24 wherein the width of all
fins are equal.
28. A firetube heat exchanger of claim 24 wherein the fins of
adjacent rows of fins are offset angularly up to one-half of the
fin width.
29. A firetube heat exchanger of claim 24 wherein the height of the
sides of all fins in a row of fins are equal.
30. A firetube heat exchanger of claim 24 wherein the height of the
fins in the first row of fins adjacent to the fluid inlet are lower
than the height of fins in other rows of fins.
31. A firetube heat exchanger of claim 4 wherein the height of the
fins in the first row of fins adjacent to the fluid inlet are lower
than the height of fins in other rows of fins.
32. A firetube heat exchanger of claim 31 comprising between 4 and
20 rows of fins and wherein the height of fins of row 3 and
subsequent rows of fins are equal.
33. A firetube heat exchanger of claim 32 wherein fins of one or
more rows of fins are offset angularly from the fins of an adjacent
row of fins.
34. A firetube heat exchanger of claim 32 wherein the fins of
adjacent rows of fins are offset angularly up to one-half of the
fin width.
35. A firetube heat exchanger of claim 1 wherein the two sides of
each of said fins are substantially parallel.
36. A firetube heat exchanger of claim 2 wherein the two sides of
each of said fins are substantially parallel and perpendicular to
the bottom surface.
37. A firetube heat exchanger of claim 2 wherein the two sides of
each of said fins extend upwardly from said bottom surface at acute
angles or obtuse angles.
38. A firetube heat exchanger of claim 3 wherein the two sides of
each of said fins are substantially parallel.
39. A firetube heat exchanger of claim 3 wherein the two sides of
each of said fins extend upwardly from said bottom surface at acute
angles or obtuse angles.
40. A firetube heat exchanger of claim 1 further comprising a heat
resistant insert positioned concentrically along a portion of the
length of said interior channel.
41. A firetube heat exchanger of claim 1 further comprising a
plurality of brazed thermally conductive rings forming a conductive
and ductile bond between the inner surface of said cylindrical
shell and adjacent rows of said fins.
42. A firetube heat exchanger of claim 41 comprising a said brazed
thermally conductive ring between all adjacent rows of said
fins.
43. A firetube heat exchanger of claim 41 comprising one or more
brazed thermally conductive rings along the inner surface of said
cylindrical shell between the last row of fins and said fluid
outlet end.
44. A firetube heat exchanger comprising: an elongated shell having
an inlet end and an outlet end; and a fin assembly secured on the
inner surface of said shell, said fin assembly comprising a first
and second row of U-shaped elongated fins, each fin having at least
one planar side extending upwardly from said inner surface and
defining an elongated interior channel, wherein said first row of
fins is adjacent said inlet end and wherein said second row of fins
is taller than said first row of fins.
45. A firetube heat exchanger of claim 44, wherein each row of
elongated fins are aligned substantially parallel along a central
axis of said cylindrical shell.
Description
BACKGROUND OF THE INVENTION
[0001] Firetube heat exchangers are well known for converting heat
from hot gases of combustion to a material, typically a liquid,
exposed to the outside surface of the firetube. Such heat
exchangers are described in U.S. Pat. Nos. 5,913,289 and 6,675,746.
These as well as other previously described firetube heat
exchangers have been relatively expensive or difficult to
manufacture. In addition, some firetube heat exchangers have been
less effective in transferring heat from the hot gases of
combustion passing through the interior of the firetube to the
outside surface for heating the liquid. It is to an improved,
highly efficient, and relatively economically manufactured firetube
design that the apparatus described herein is directed.
SUMMARY OF THE INVENTION
[0002] Embodiments of the firetube heat exchanger described herein
comprise an elongated cylindrical shell having a fluid inlet end, a
fluid outlet end and a fin assembly secured on the inner surface of
the shell. The fin assembly comprises a plurality of circular rows
of elongated U-shaped fins, each fin having a bottom surface
secured to the inner surface of the shell with two generally flat,
planar sides extending upwardly from the bottom fin surface. The
fins in each row are aligned substantially parallel along the axis
of the cylindrical shell, and the fins of one or more rows of fins
may be offset angularly from the fins of an adjacent row of fins.
In some embodiments, the flat, planar sides of the fins are
substantially parallel and the fins in each row of fins,
respectively, are substantially identical in fin height, length and
width. In other embodiments, the dimensions of fins in at least two
of the rows are different in height, and/or width, and/or length.
In yet another embodiment, three or more different fin heights are
used within the firetube heat exchanger. These as well as other
variations in designs and embodiments of the fins and the firetube
heat exchanger design will be described hereinafter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] FIG. 1 is an isometric view of one embodiment of a firetube
showing a semi-transparent cylindrical tube shell.
[0004] FIG. 2 is an cross-sectional isometric view taken across the
line 2-2 of one embodiment of a firetube that illustrates the
interior fin arrangement and design.
[0005] FIG. 3 is an end view of a fin and illustrates three
different fin heights.
[0006] FIG. 4 is a side view of a fin shown in FIG. 3, also
illustrating three different fin height designations.
[0007] FIG. 5 is a cross-sectional view of the split firetube of
FIG. 2 with an interior ceramic core plug installed.
DETAILED DESCRIPTION
[0008] One embodiment is a firetube heat exchanger that includes an
outer shell. Disposed along the interior surface of the shell is a
fin assembly having a plurality of circular rows of elongated
U-shaped fins. In one embodiment, each fin has a bottom surface
that is secured to an inner surface of said cylindrical shell. Each
fin may also have two sides extending upwardly from said bottom
surface and defining an elongated interior channel. The sides may
be planar and flat. In addition, in one embodiment, the fins in
each row may be aligned substantially parallel along the axis of
the cylindrical shell. In one embodiment, the sides of the fins in
different rows have differing heights.
[0009] In FIG. 1 a firetube heat exchange assembly 10 is
illustrated with the cylindrical shell 11 shown in
semi-transparency for viewing the interior fins. Reference is also
made to the cross-sectional view of FIG. 2 in which the cylindrical
shell has been sectioned to show more particular features of the
fin assembly.
[0010] As illustrated, the fin assembly is secured
circumferentially around the inner surface of the cylindrical shell
and comprises a plurality of circular rows of elongated U-shaped
fins. In the illustrated embodiment, the fins in each row,
respectively, are substantially identical and using fins of three
different heights in different rows of fins. The first row of fins
nearest to the fluid inlet end 13 of shell 11 comprises
substantially identical fins 12, the second row comprising
substantially identical fins 14 and the third row and the remaining
rows made up of substantially identical fins 16. In this
embodiment, the difference between fins 12, 14 and 16 is in the
height of their upwardly extending sides. In this embodiment, the
fin sides are lower in the front of the firetube where gas
temperatures are hottest.
[0011] The length of the fins of all the rows may be the same,
although different fin lengths in the different rows may be used.
However, all of the fins in any single row may have substantially
the same length. Similarly, the width of the fins in any row may be
the same, although different fin widths may be used. However, in
some embodiments, all of the fins in a row have substantially
identical widths. In other embodiment, all of the fins in all of
the rows of the firetube have substantially identical widths.
[0012] The difference in the heights of the sides of the fins of
the different rows is further illustrated in FIGS. 3 and 4. The
heights of opposite sides 22 and 24 of fin 20 are the same.
However, the upper edge 21 of all fins 12 in the first row of fins
is shorter than the height of the sides of the fins in rows 14 and
16. Specifically, the upper edge 23 of the sides 22, 24 of all
second row fins 14 is greater than the height of the fins in row 12
and shorter than the height of fins in the third row of fins 16 and
the remaining rows of fins all having an upper edge 25.
[0013] In one embodiment, the height of the fins differs by between
10% and 50%. In another embodiment, the height of the fins differs
by between 15% and 35%. In yet another embodiment, the height of
the fins differs by between 20% and 30%. In one embodiment, one row
of fins is 0.5 inches tall, the second row of fins are 5/8 inches
tall and the fins in the third and remaining rows are 0.75 inches
tall. In one embodiment, each row of fins from the first row to the
third row is 25% taller than the preceding row.
[0014] As previously described, and illustrated particularly in
FIG. 3, all of the fins have substantially the same width and are
U-shaped with a bottom surface 26. The bottom fin surface is
generally flat or is arched or curved preferably on a radius
(radiused) to better match the radius or curvature of the inner
cylindrical surface of the shell underlying the bottom fin surface.
Such a radiused bottom surface will also facilitate brazing of the
fin and cylinder surfaces. Such a flat or curved bottom also
provides a surface for tack welding or spot welding each fin in
place during assembly of the firetube heat exchanger.
[0015] In another embodiment, the opposite fin sides are parallel
and extend upwardly substantially perpendicular (normal) from the
bottom surface. However, the opposite sides may also be somewhat
angled at obtuse or acute angles from the bottom surface. Such
angles may be selected, depending on the desired number of fins in
each row, as well as the desired spacing of the fins in each row.
It will also be understood that the specific number of fins in each
row will depend on the width of the fins and the radial dimensions
or circumference of the cylindrical shell.
[0016] In this embodiment, the fins in each respective row are
aligned lengthwise with their upwardly extending sides aligned
substantially parallel along the axis of the cylindrical shell. As
previously noted, the shortest fins or fins in rows of fins are at
the inlet end of the firetube, and fins in succeeding rows have
higher sides. The specific number of different heights of fins in
the firetube may be selected, but at least two different heights
may be used. In another embodiment, at least three different
heights of fins are used, although more different heights may also
be used without departing from the invention. In the embodiment
illustrated, three different heights of fins are used, as
previously described and shown in FIGS. 1-4.
[0017] The fins in adjacent rows of fins may be aligned angularly
along the length of the firetube or fins of adjacent rows of fins
may be offset angularly from one another. Of course, if the fins of
adjacent rows of fins are of different widths, the upwardly
extending sides of the fins in adjacent rows will present an offset
of fin sides from inlet to outlet along the length of the firetube.
In one embodiment, with the fins being of substantially the same
width, the fins may be aligned angularly without offset, or they
may be offset angularly up to one-half of the fin width.
[0018] The specific number of rows of fins will depend on the
length of the firetube, and the length of the fins in the different
rows of fins. The number of rows of fins of between 2 and about 20
rows is preferred and more preferred is between about 4 and about
12 rows of fins, fewer fins results in more heat stress along the
firetube. By way of example, for a firetube of about 2 feet in
length, 10 rows of fins having an equal fin length in each row is
shown in the drawings.
[0019] The upper edges of the upwardly extending fins defines an
elongated interior channel in which is secured a heat resistant
insert, often referred to as a core plug, and which is typically
made of a heat resistant ceramic material. The length of the insert
may extend between the second row of fins from the inlet end and
the last rows of fins at the outlet end, as illustrated in FIG. 5.
The shape of the insert is such that the diameter gradually
increases from the forward end, closest to the fluid inlet of the
firetube, leaving a space between the surface of the insert and the
upper edges of the fin sides for a portion of its length in and
then contacting the fin edges along a successive portion of the
firetube length. Such shape of the insert, its dimensions, and
placement are well understood by those skilled in the art.
[0020] In another embodiment, the firetube heat exchanger assembly
includes copper rings extending between rows of fins and the
firetube surface. The copper rings may be mounted between all rows
of fins, with each ring contacting the interior of the surface of
the firetube as well as the ends of fins in adjacent rows. At least
one ring may be mounted at the end of the last row of fins. In
another embodiment, a plurality of copper rings is mounted at the
end of the last row of fins. In FIG. 2, copper rings 30, 31, 32,
33, 34, 35 are illustrated. The copper rings are shown only between
every other row of fins by way of example and for simplicity, but
again, a ring may be disposed between every row of fins. The copper
rings may be mounted using vacuum brazing or brazed in a hydrogen
furnace, or otherwise installed by brazing techniques known to
those skilled in the art.
[0021] In one embodiment, the rings comprise high purity (above
98%) copper because of its ductility and conductivity. However, the
use of mixtures of copper with another conductive metal, for
example nickel, is not precluded. It is to be understood that when
the copper ring is brazed, it will melt and flow to both rows of
fins and the tube interior surface creating a conductive and
ductile bond therebetween. Since the rings are to be brazed, their
cross-sectional shape prior to brazing is not critical.
[0022] The firetube heat exchanger described herein is useful in
any heat exchange apparatus for directing heat from hot gases of
combustion passing along the inside of the firetube to heat liquids
contacting the outside surface of the firetube. The firetube is
especially useful in a boiler or stripping section of the generator
of an aqua-ammonia absorption system, for example, a GAX absorption
system, such as described in U.S. Pat. Nos. 6,487,875, 6,427,478,
6,718,792, 6,735,963 and 6,748,752. The firetube heat exchanger
described herein has advantages of being cost effective to
manufacture, reliable, and efficient as compared to other firetubes
used and known in the prior art.
* * * * *