U.S. patent application number 14/666389 was filed with the patent office on 2016-09-29 for heat exchanger for a gas turbine engine.
The applicant listed for this patent is General Electric Company. Invention is credited to William Dwight Gerstler, James Michael Kostka, John William Moores, Jeffrey Douglas Rambo.
Application Number | 20160281532 14/666389 |
Document ID | / |
Family ID | 55650154 |
Filed Date | 2016-09-29 |
United States Patent
Application |
20160281532 |
Kind Code |
A1 |
Rambo; Jeffrey Douglas ; et
al. |
September 29, 2016 |
HEAT EXCHANGER FOR A GAS TURBINE ENGINE
Abstract
A heat exchanger apparatus for a gas turbine engine includes: a
plurality of heat exchanger pipes, each pipe having first and
second ends; wherein the heat exchanger pipes are disposed in a
repeating pattern such that each heat exchanger pipe is joined to
at least one other heat exchanger pipe.
Inventors: |
Rambo; Jeffrey Douglas;
(Mason, OH) ; Gerstler; William Dwight;
(Niskayuna, NY) ; Kostka; James Michael;
(Loveland, OH) ; Moores; John William;
(Cincinnati, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Family ID: |
55650154 |
Appl. No.: |
14/666389 |
Filed: |
March 24, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D 25/12 20130101;
F28F 1/26 20130101; F28D 1/0477 20130101; F02C 7/18 20130101; F02C
7/14 20130101; F05D 2260/213 20130101; F28D 2021/0026 20130101;
F05D 2250/71 20130101; F28D 2021/0021 20130101 |
International
Class: |
F01D 25/12 20060101
F01D025/12 |
Claims
1. A heat exchanger apparatus for a gas turbine engine, comprising
a plurality of heat exchanger pipes, each pipe having first and
second ends; wherein the heat exchanger pipes are disposed in a
repeating pattern such that each heat exchanger pipe is joined to
at least one other heat exchanger pipe.
2. The apparatus of claim 1 wherein each heat exchanger pipe is
joined to other heat exchanger pipes at two or more locations.
3. The apparatus of claim 1 wherein each heat exchanger pipe is
joined to other heat exchanger pipes at three locations.
4. The apparatus of claim 1 wherein the joints between neighboring
heat exchanger pipes are defined by mutually shared wall portions
of the heat exchanger pipes.
5. The apparatus of claim 1 further comprising a fluid manifold,
wherein the first and second ends of each heat exchanger pipe are
connected in fluid communication with the fluid manifold.
6. The apparatus of claim 5 wherein the fluid manifold includes at
least one inlet channel and at least one outlet channel, and the
first end of each heat exchanger pipe is connected to an inlet
channel and the second end of each heat exchanger pipe is connected
to an outlet channel.
7. The apparatus of claim 5 wherein: the inlet and outlet channels
are spaced-apart from each other; each heat exchanger pipe has a
shallow S shape with first and second ends; the first end of each
heat exchanger pipe is connected to the inlet channel; and the
second end of each heat exchanger pipe is connected to the outlet
channel.
8. The apparatus of claim 7 wherein each heat exchanger pipe
includes a straight central portion and first and second end bends
that are curved opposite each other.
9. The apparatus of claim 7 wherein tire heat exchanger pipes are
grouped in pairs, each pair of heat exchanger pipes being mutually
joined and forming an X shape.
10. The apparatus of claim 1 wherein each heat exchanger pipe has
at least one bend therein.
11. The apparatus of claim 1 wherein each heat exchanger pipe has a
shape including two spaced-apart, parallel legs interconnected by a
transverse bridge.
12. The apparatus of claim 11 wherein each leg includes a first
upright segment, an axial segment, and a second upright
segment.
13. The apparatus of claim 12 wherein the bridge of each heat
exchanger pipe is joined to the leg of a neighboring heat exchanger
pipe.
14. The apparatus of claim 11 wherein the heat exchanger pipes are
arranged in two spaced-apart rows, wherein the heat exchanger pipes
of the rows are disposed mirror-images acute angles to a reference
axis.
15. The apparatus of claim 13 wherein the heat exchanger pipes of
the first row are interlocked with the heat exchanger pipes of the
second row.
16. The apparatus of claim 1 wherein an exterior surface of at
least one of the heat exchanger pipes includes an area-increasing
structure.
17. The apparatus of claim 16 wherein the area-increasing structure
is made from a material different from the at least one heat
exchanger pipe.
18. The apparatus of claim 1 wherein flow channels defined between
the heat exchanger pipes having an approximately constant flow area
along a selected direction of flow.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to gas turbine engines and
methods for oil cooling in such engines.
[0002] Gas turbine engines are commonly provided with a circulating
oil system for lubricating and cooling various engine components
such as bearings, gearboxes, electrical generators, and the like.
In operation the oil absorbs a substantial amount of heat that must
be rejected to the external environment in order to maintain the
oil at acceptable temperatures. As engine designs evolve the amount
of heat to be rejected is increasing.
[0003] Known oil cooling systems for gas turbine engines typically
include one or more air-to-oil heat exchangers, referred to as "air
cooled oil coolers" or "ACOCs", and may also include air-to-air
heat exchangers. These heat exchangers can be heavy and have high
drag, and can require special inlet and outlet ducts and large,
heavy brackets.
[0004] The high weight is attributable partially to the need with
existing designs to use heavy, high-strength alloys and to designs
in which the structural and thermal functions are addressed
separately. Furthermore, these heat exchangers are used in a
challenging environment with high temperatures and pressures that
can cause low cycle fatigue ("LCF") problems and high vibration
levels that can cause high cycle fatigue ("HCF") problems.
[0005] Accordingly, there is a need for a gas turbine engine heat
exchanger having low weight, compact size and good strength and
fatigue life.
BRIEF DESCRIPTION OF THE INVENTION
[0006] This need is addressed by the present invention, which
provides a heat exchanger having a plurality of joined,
mutually-supporting heat exchanger pipes.
[0007] According to one aspect of the invention, a heat exchanger
apparatus for a gas turbine engine includes a plurality of heat
exchanger pipes, each pipe having first and second ends; wherein
the heat exchanger pipes are disposed in a repeating pattern such
that each heat exchanger pipe is joined to at least one other heat
exchanger pipe.
[0008] According to another aspect of the invention, each heat
exchanger pipe is joined to other heat exchanger pipes at two or
more locations.
[0009] According to another aspect of the invention, each heat
exchanger pipe is joined to other heat exchanger pipes at three
locations.
[0010] According to another aspect of the invention, the joints
between neighboring heat exchanger pipes are defined by mutually
shared wall portions of the heat exchanger pipes.
[0011] According to another aspect of the invention, the apparatus
further includes a fluid manifold, wherein the first and second
ends of each heat exchanger pipe are connected in fluid
communication with the fluid manifold.
[0012] According to another aspect of the invention, the fluid
manifold includes at least one inlet channel and at least one
outlet channel, and the first end of each heat exchanger pipe is
connected to an inlet channel and the second end of each heat
exchanger pipe is connected to an outlet channel.
[0013] According to another aspect of the invention, the inlet and
outlet channels are spaced-apart from each other; each heat
exchanger pipe has a shallow S shape with first and second ends;
the first end of each heat exchanger pipe is connected to the inlet
channel; and the second end of each heat exchanger pipe is
connected to the outlet channel.
[0014] According to another aspect of the invention, each heat
exchanger pipe includes a straight central portion and first and
second end bends that are curved opposite each other.
[0015] According to another aspect of the invention, the heat
exchanger pipes are grouped in pairs, each pair of heat exchanger
pipes being mutually joined and forming an X shape.
[0016] According to another aspect of the invention, each heat
exchanger pipe has at least one bend therein.
[0017] According to another aspect of the invention, each heat
exchanger pipe has a shape including two spaced-apart, parallel
legs interconnected by a transverse bridge.
[0018] According to another aspect of the invention, each leg
includes a first upright segment, an axial segment, and a second
upright segment.
[0019] According to another aspect of the invention, the bridge of
each heat exchanger pipe is joined to the leg of a neighboring heat
exchanger pipe.
[0020] According to another aspect of the invention, the heat
exchanger pipes are arranged in two spaced-apart rows, wherein the
heat exchanger pipes of the rows are disposed mirror-images acute
angles to a reference axis.
[0021] According to another aspect of the invention, the heat
exchanger pipes of the first row are interlocked with the heat
exchanger pipes of the second row.
[0022] According to another aspect of the invention, an exterior
surface of at least one of the heat exchanger pipes includes an
area-increasing structure.
[0023] According to another aspect of the invention, the
area-increasing structure is made from a material different from
the at least one heat exchanger pipe.
[0024] According to another aspect of the invention, channels
defined between the heat exchanger pipes having an approximately
constant flow area along a selected direction of flow.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The invention may be best understood by reference to the
following description taken in conjunction with the accompanying
drawing Figures in which:
[0026] FIG. 1 is a schematic cross-sectional view of a gas turbine
engine incorporating a heat exchanger system constructed according
to an aspect of the present invention;
[0027] FIG. 2 is perspective view of a single heat exchanger pipe
constructed according to an aspect of the present invention;
[0028] FIG. 3 is a perspective view of two of the heat exchanger
pipes shown in FIG. 2;
[0029] FIG. 4 is a perspective view of three of the heat exchanger
pipes shown in FIG. 3;
[0030] FIG. 5 is a perspective view of an array of the heat
exchanger pipes shown in FIG. 2;
[0031] FIG. 6 is a perspective view of two of the heat exchanger
pipes shown in FIG. 2, in an alternative arrangement;
[0032] FIG. 7 is a perspective view of four of the heat exchanger
pipes shown in FIG. 6;
[0033] FIG. 8 is a perspective view of an array of the heat
exchanger pipes shown in FIG. 6;
[0034] FIG. 9 is a perspective view of two alternative heat
exchanger pipes constructed according to an aspect of the present
invention;
[0035] FIG. 10 is a perspective view of four of the heat exchanger
pipes shown in FIG. 9;
[0036] FIG. 11 is a perspective view of six of the heat exchanger
pipes shown in FIG. 9;
[0037] FIG. 12 is a perspective view of an array of the heat
exchanger pipes shown in FIG. 9; and
[0038] FIG. 13 is a schematic cross-sectional view of a heat
transfer pipe incorporating area-increasing structures.
DETAILED DESCRIPTION OF THE INVENTION
[0039] Referring to the drawings wherein identical reference
numerals denote the same elements throughout the various views,
FIG. 1 depicts a gas turbine engine 10 incorporating a heat
exchanger apparatus constructed according to an aspect of the
present invention. while the illustrated example is a high-bypass
turbofan engine, the principles of the present invention are also
applicable to other types of engines, such as low-bypass, turbojet,
etc. The engine 10 has a longitudinal center line or axis 11 and an
outer stationary annular casing 12 disposed concentrically about
and coaxially along the axis 11. The engine 10 has a fan 14,
booster 16, compressor 18, combustor 20, high pressure turbine 22,
and low pressure turbine 24 arranged in serial flow relationship.
In operation, pressurized air from the compressor 18 is mixed with
fuel in the combustor 20 and ignited, thereby generating combustion
gases. Some work is extracted from these gases by the high pressure
turbine 22 which drives the compressor 18 via an outer shaft 26.
The combustion gases then flow into a low pressure turbine 24,
which drives the fan 14 and booster 16 via an inner shaft 28. The
engine 10 includes a bypass duct 32 into which the fan 14
discharges.
[0040] The engine 10 includes a known type of system for
circulating pressurized oil to various parts of the engine (for
example, bearings) for lubrication and cooling. In operation, the
oil absorbs a significant heat load which must then be rejected to
the external environment. The present invention provides a heat
exchanger apparatus for cooling that oil or other fluid. Generally
stated, the heat exchanger includes a plurality of slender heat
exchanger pipes which are exposed to a cooling air flow, and
through which the oil is circulated. The pipes are connected to
each other to form a mutually self-supporting structure. Numerous
physical configurations of the heat exchanger pipes are possible.
Several examples will be discussed in detail below.
[0041] FIGS. 2-5 illustrate an exemplary heat exchanger 40. More
specifically, FIGS. 2-4 illustrate portions of the heat exchanger
40 in various stages of assembly, while FIG. 5 illustrates the
complete heat exchanger 40.
[0042] The heat exchanger 10 includes a fluid manifold 42 which is
configured to receive a fluid (e.g. lubrication oil or another
liquid, or a gas) to be cooled from the engine 10, circulate it
through a plurality of heat exchanger pipes (described below), and
return the cooled fluid to be stored or used by the engine 10. In
the illustrated example, the fluid manifold 42 is shown as
including one or more inlet channels 44 and one or more outlet
channels 46 configured as side-by-side tubes.
[0043] The heat exchanger 40 includes a plurality of heat exchanger
pipes 48 which in operation are positioned to be exposed to a flow
of cooling fluid (e.g., air), depicted by arrow "F". For example,
the heat exchanger 40 could be positioned with the heat exchanger
pipes 48 exposed within the bypass duct 32 (see FIG. 1). In
general, in the embodiments shown in FIGS. 2-8, the bulk direction
of the cooling fluid flow F is parallel to a first axis or
direction "A" of the fluid manifold 12, and perpendicular to a
second axis or direction "B" of the fluid manifold 42, wherein axes
A and B are mutually perpendicular to each other.
[0044] Referring specifically to FIG. 2, each heat exchanger pipe
40 is a relatively long slender tube with at least one bend in it.
As a general principle it may be stated that for each bend added to
a pipe, heat transfer capability is improved, while vibrational
degree of freedom ("DOF") is also increased. In the illustrated
example, the heat exchanger pipe 40 is a single continuous member,
but for convenience may be described as having several segments. In
particular, each heat exchanger pipe has two identical, spaced
apart "legs" 50 which are generally parallel to each other. Each
leg 50 has a first end 52 and a second end 54, and the second ends
54 are connected by abridge 56 which extends transversely between
the two legs 50. Beginning at the first end 52, each leg 50
includes a first upright segment 58, an axial segment 60, and a
second upright segment 62. The entire structure may be described as
having a shape similar to a "chair frame". The first end 52 of one
leg 50 (also representing one terminal end of the entire heat
exchanger pipe 48) is coupled in fluid communication with the inlet
channel 44, and the first end 52 of the second leg 50 (also
representing a second terminal end of the entire heat exchanger
pipe) is coupled in fluid communication with the outlet channel 46.
Optionally, multiple heat exchanger pipes 48 could be
interconnected with each other, for example using U-bends (not
shown) so as to make multiple passes before terminating at the
fluid manifold 42. Similarly, multiple heat exchanger pipes 48
could be arranged to provide pipe-to-pipe flow in a direction along
reference axis B, in which case some or all of the fluid manifold
42 could be eliminated.
[0045] A single heat exchanger pipe 48 is relatively flexible and
could be subject to damage from vibration loads resulting from
engine operation or flow-induced vibrations caused by the
aerodynamic shedding of the external air flow, commonly referred to
as "fretting". To counter this, multiple heat exchanger pipes 48
may be assembled contacting each other at multiple locations so
that they can mutually support each other, providing additional
stiffness which raises the natural frequencies above the forcing
frequency.
[0046] For example, in FIG. 3 the fluid manifold 42 is shown
including two inlet channels 44, 44' respectively, and one outlet
channel 46. One heat exchanger pipe 48 is connected to the first
inlet channel 44 and the outlet channel 46, and the second heat
exchanger pipe 48' is connected to the outlet channel 46 and the
second inlet channel 44'. Referring to a reference axis B parallel
to the inlet channels 44, 44', the two heat exchanger pipes 48, 48'
are in approximately the same axial position but are laterally
offset from one another. The bridge 56 of the first heat exchanger
pipe 48 is shown contacting to a first leg 50' of the second heat
exchanger pipe 48'. The two heat exchanger pipes 48, 48' are joined
to each other at the contact point.
[0047] As used herein in referring to the heat exchanger pipes 48,
the term "joined" implies a solid, rigid structural connection of a
permanent nature between the two joined elements. For example, the
heat exchanger pipes 48 may be made separately and then joined
using a known bonding process such as welding or brazing or
diffusion bonding. Alternatively, the heat exchanger pipes 48 could
be made as part of an integral, unitary, or monolithic whole, where
the walls of the pipes are shared at the contact points.
[0048] FIG. 4 shows a further stage of assembly where a third heat
exchanger pipe 48'' has been added, connected to the first inlet
channel 44 and the outlet channel 46, and laterally in-line with
the first heat exchanger pipe 48 and axially offset therefrom. Each
leg 50 of the first heat exchanger pipe 48 contacts the
corresponding leg 50'' of the third heat exchanger pipe 48''. In
this arrangement the first heat exchanger pipe 48 is contacted by
and joined to other heat exchanger pipes 48', 48'' at three
locations.
[0049] Finally, FIG. 5 depicts the heat exchanger 40 where the
arrangement of heat exchanger pipes 48 shown in FIG. 4 is repeated
in both axial and lateral directions, and each heat exchanger pipe
48 is contacted by and joined to other heat exchanger pipes at
three locations. This arrangement provides significant additional
stiffness and strength to each of the heat exchanger pipe 48.
Stated another way, the heat exchanger pipes 48 are mutually
self-supporting. This gives the heat exchanger 40 good strength and
stiffness so that its natural frequencies can be made appropriately
high, while still being light weight. This configuration is
advantageous as compared to the prior art use of tie plates or
struts to stiffen heat exchanger tubes. The heat exchanger pipes 48
may also be described as being "interlocked". It is noted that the
individual heat exchanger pipes 48 need not be joined or
interlocked with immediately neighboring heat exchanger pipes 48 in
order to accomplish the mutual self-support effect. For example, a
first heat exchanger pipe 48 could be configured to joint or
interlock with another heat exchanger pipe 48 that is separated
from the first heat exchanger pipe 48 by one or more intervening
heat exchanger pipes 48. This is true for all of the embodiments
described herein.
[0050] FIGS. 6-8 illustrate an alternative heat exchanger 140. More
specifically, FIGS. 6 and 7 illustrate portions of the heat
exchanger 140 in various stages of assembly, while FIG. 8
illustrates the complete heat exchanger 140.
[0051] The heat exchanger 140 uses the heat exchanger pipes 148
which may be identical to the heat exchanger pipes 48 as seen in
FIGS. 2-5, but arranged in a different pattern. The heat exchanger
140 includes a fluid manifold 142 comprising two pairs of channels,
143A and 143B, Each channel pair 143A, 143B includes one inlet
channel 144 and one outlet channel 146, configured as side-by-side
tubes. The pairs 143A and 143B run parallel to each other and are
laterally separated by a space 145.
[0052] The heat exchanger pipes 148 are oriented with a line
running through their ends 152 set at an acute angle to a reference
axis B. A first end 152 of one leg 150 (also representing one
terminal end of the entire heat exchanger pipe) is coupled in fluid
communication with the inlet channel 144 of the first pair 143A,
and the first end 152 of the second leg 150 (also representing a
second terminal end of the entire heat exchanger pipe 148) is
coupled in fluid communication with the outlet channel 146 of the
first pair 143A.
[0053] A row of heat exchanger pipes 148 oriented as described
above are disposed along the first pair 143A of channels. Each heat
exchanger pipe 148 contacts and is joined to its neighboring heat
exchanger pipe 148 in the row at one location.
[0054] Another row of heat exchanger pipes 148' are disposed along
the second pair 143B of channels, and arranged similarly, but are
oriented as a mirror-image to the first row of heat exchanger pipes
148 (in other words, they are angled opposite relative to the axis
B). Each heat exchanger pipe 148' contacts and is joined to its
neighboring heat exchanger pipe 148' in the row at one
location.
[0055] As seen in FIG. 8, the heat exchanger pipes 148, 148' of the
two pairs 143A, 143B are interwoven with each other so that each
heat exchanger pipe 148, 148' is contacted by and joined to other
heat exchanger pipes 148, 148' at three locations.
[0056] FIGS. 9-12 illustrate an alternative heat exchanger 240.
More specifically, FIGS. 9-11 illustrate portions of the heat
exchanger 240 in various stages of assembly, while FIG. 12
illustrates the complete heat exchanger 240.
[0057] The heat exchanger 240 includes a fluid manifold. In the
illustrated example, the fluid manifold includes an inlet channel
244 spaced-apart from an outlet channel 246.
[0058] The heat exchanger 240 includes a plurality of heat
exchanger pipes 248 which in operation are positioned to be exposed
to a flow of cooling fluid (e.g. air), depicted by arrow "F". In
general, in the embodiment shown in FIGS. 9-12, the bulk direction
of the cooling fluid flow F is parallel to a first axis or
direction "A" of the fluid manifold, and perpendicular to a second
axis or direction "B" of the fluid manifold, wherein axes A and B
are mutually perpendicular to each other.
[0059] Referring specifically to FIG. 9, each heat exchanger pipe
248 is a relatively long slender tube with first and second ends
252, 254. Between the ends 252, 254, the heat exchanger pipe 248
has a straight central portion 256 with first and second end bends
258, 260 that are curved opposite each other. The complete heat
exchanger pipe 248 can be described as having a shallow "S" shape.
The first end 252 is coupled in fluid communication with the inlet
channel 244, and the second end 254 is coupled in fluid
communication with the outlet channel 246.
[0060] Each heat exchanger pipe 248 is paired with a neighboring
heat exchanger pipe 248 contacting and mutually joined at one point
and forming an "X" shape. As seen in FIGS. 10 and 11, these pairs
can be repeated in axial and lateral directions. Finally, FIG. 12
depicts the complete heat exchanger 240.
[0061] The heat exchanger pipes described above may be made from a
material \ suitable thermal conductivity and strength at expected
operating temperatures. Nonlimiting examples of suitable materials
include aluminum alloys, high-strength steels, and nickel-based
alloys (e.g. INCONEL).
[0062] In any of the configurations described above, the heat
exchanger pipes may be configured such that the open spaces or flow
channels for fluid flow between them are generally constant. Stated
another way, the area of each of the open spaces is approximately
the same for any given location along the direction of flow F. This
avoids repeated expansions or contractions in flow area that would
create a substantial pressure loss.
[0063] All or part of the heat exchangers described above,
including the manifolds and/or the heat exchanger pipes, or
portions thereof, may be part of a single unitary, one-piece, or
monolithic component, and may be manufactured using a manufacturing
process which involves layer-by-layer construction or additive
fabrication (as opposed to material removal as with conventional
machining processes). Such processes may be referred to as "rapid
manufacturing processes" and/or "additive manufacturing processes,"
with the term "additive manufacturing process" being term herein to
refer generally to such processes. Additive manufacturing processes
include, but are not limited to: Direct Metal Laser Sintering
(DMLS), Direct Metal Laser Melting (DMLM), Laser Net Shape
Manufacturing (LNSM), electron beam sintering, Selective Laser
Sintering (SLS), 3D printing, such as by inkjets and laserjets,
Sterolithography (SLS), Electron Beam Melting (EBM), Laser
Engineered Net Shaping (LENS), and Direct Metal Deposition
(DMD).
[0064] Alternatively, portions of the heat exchangers described
above could be made by processes such as rolling, extruding,
casting, or machining from blanks, or by using an additive
manufacturing process, and then bonded together, for example using
known welding or brazing methods, or diffusion bonding.
[0065] A significant feature of all of the heat exchanger
configurations described above is that the air flow spaces between
the heat exchanger tubes are of approximately uniform size. A
constant air flow area minimizes pressure drop by reducing
irreversible flow losses associated with flow acceleration and
deceleration. While the exemplary figures show this is achieved
using a repeatable tubular pattern, this is not a limiting feature
of the invention. The same constant air flow space can be achieved
through a combination of changing the number of heat exchanger
pipes and the shapes of the heat exchanger pipes along the air flow
path. Such an arrangement results in a non-uniform distribution of
heat exchanger pipes and pips sizes, while maintaining a uniform
air flow area. Manufacturing techniques such as additive
manufacturing allows realization of such designs.
[0066] The exterior surfaces of any of the heat exchanger pipes
described above may be provided with area-increasing structures to
enhance the air-side heat transfer. Nonlimiting examples of
area-increasing structures include fins, ribs, pin fins, grooves,
and dimples. FIG. 13 shows a short section of a heat transfer pipe
48 having a pipe wall 51 with an exterior surface 53. An array of
spaced-apart annular fins 57 extend outward from the exterior
surface 53. The fins 57 or other area-increasing structure could be
part of an integral, unitary or monolithic construction with the
pipe wall 51, for example being made by a conventional machining or
additive machining process, or they could be manufactured
separately and then attached to the pipe wall 51. The fins 57 or
other area-increasing structure could be of the same material as
the pipe wall 51 or a different material.
[0067] The invention described herein has several advantages over
the prior art. The integrated structural-thermal design allows for
improved LCF/HCF life, and improved heat exchanger packaging. For a
given set of temperature and pressure conditions, it can allow the
use of a material with higher thermal conductivity and lower
strength than would otherwise be required. For example, depending
on the specific application, it might allow a nickel-based alloy to
perform where no alloy would otherwise be suitable, or allow the
substitution of a steel alloy in place of a nickel alloy, or allow
the substitution of an aluminum alloy in place a steel alloy.
[0068] The foregoing has described a heat exchanger apparatus. All
of the features disclosed in this specification (including any
accompanying claims, abstract and drawings), and/or all of the
steps of any method or process so disclosed, may be combined in any
combination, except combinations where at least some of such
features and/or steps are mutually exclusive.
[0069] Each feature disclosed in this specification (including any
accompanying claims, abstract and drawings) may be replaced by
alternative features serving the same, equivalent or similar
purpose, unless expressly stated otherwise. Thus, unless expressly
stated otherwise, each feature disclosed is one example only of a
generic series of equivalent or similar features.
[0070] The invention is not restricted to the details of the
foregoing embodiment(s). The invention extends any novel one, or
any novel combination, of the features disclosed in this
specification (including any accompanying claims, abstract and
drawings), or to any novel one, or any novel combination, of the
steps of any method or process so disclosed.
* * * * *