U.S. patent application number 13/675744 was filed with the patent office on 2013-05-23 for heat exchanger.
This patent application is currently assigned to ROLLS-ROYCE PLC. The applicant listed for this patent is ROLLS-ROYCE PLC. Invention is credited to Jong-Rae CHO, Man Yeong HA, Ho Seung JEONG, Sang Hu PARK.
Application Number | 20130126141 13/675744 |
Document ID | / |
Family ID | 45475434 |
Filed Date | 2013-05-23 |
United States Patent
Application |
20130126141 |
Kind Code |
A1 |
CHO; Jong-Rae ; et
al. |
May 23, 2013 |
HEAT EXCHANGER
Abstract
A heat exchanger 302 comprising: an inlet manifold 304; an
outlet manifold 306; and a tube matrix 310 comprising a plurality
of tubes 308, each tube 308 being connected at one end to the inlet
manifold 304 and at the other end to the outlet manifold 306;
wherein each tube extends generally along a longitudinal axis
defined between the connection of the tube 308 with the inlet
manifold 304 and the connection of the tube 308 with the outlet
manifold 306; and wherein a single portion 314 of each tube 308 is
offset to one side of the longitudinal axis.
Inventors: |
CHO; Jong-Rae; (Busan,
KR) ; PARK; Sang Hu; (Seoul, KR) ; HA; Man
Yeong; (Busan, KR) ; JEONG; Ho Seung; (Busan,
KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ROLLS-ROYCE PLC; |
London |
|
GB |
|
|
Assignee: |
ROLLS-ROYCE PLC
London
GB
|
Family ID: |
45475434 |
Appl. No.: |
13/675744 |
Filed: |
November 13, 2012 |
Current U.S.
Class: |
165/173 |
Current CPC
Class: |
F28D 7/005 20130101;
F28F 2265/26 20130101; F28D 1/047 20130101; F28D 1/05333 20130101;
F28D 1/0471 20130101; F28D 1/0472 20130101; F28F 1/00 20130101;
F28F 9/02 20130101 |
Class at
Publication: |
165/173 |
International
Class: |
F28F 9/02 20060101
F28F009/02; F28F 1/00 20060101 F28F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 21, 2011 |
GB |
1120008.6 |
Claims
1. A heat exchanger comprising: an inlet manifold; an outlet
manifold; and a tube matrix comprising a plurality of tubes, each
tube being fixedly connected at one end to the inlet manifold and
at the other end to the outlet manifold; wherein each tube extends
generally along a longitudinal axis defined between the connection
of the tube with the inlet manifold and the connection of the tube
with the outlet manifold, wherein a single portion of each tube is
offset to one side of the longitudinal axis; and wherein the tubes
are arranged in one or more rows in a plane defined by a
longitudinal axis of the inlet and outlet manifolds and a plurality
of rows are disposed side-by-side to form columns.
2. A heat exchanger matrix as claimed in claim 1, wherein the tubes
are fixedly connected between the inlet manifold and outlet
manifold independently from each other.
3. A heat exchanger matrix as claimed in claim 1, wherein the tubes
are each separated from an adjacent tube by a substantially similar
gap at corresponding portions along the longitudinal axis.
4. A heat exchanger as claimed in claim 1, wherein the tubes are
generally C-shaped.
5. A heat exchanger as claimed in claim 1, wherein the offset
portion comprises a curved portion which curves away from the
longitudinal axis.
6. A heat exchanger as claimed in claim 5, wherein the curved
portion has a constant curvature.
7. A heat exchanger as claimed in claim 1, wherein the offset
portion comprises a straight portion and pair of angled portions
which offset the straight portion from the longitudinal axis.
8. A heat exchanger as claimed in claim 1, wherein the offset
portion is offset in a plane defined by a longitudinal axis of the
inlet and outlet manifolds.
9. A heat exchanger as claimed in claim 1, wherein a minimum gap
between adjacent tubes over the offset portion is greater than 2/3
of the maximum gap between adjacent tubes at the inlet and outlet
manifolds.
10. A heat exchanger as claimed in claim 1, wherein the offset
portion is 30-70% of the total length of the tube.
Description
[0001] The present invention relates to a heat exchanger, and
particularly but not exclusively to a heat exchanger having a tube
matrix which reduces thermal stress experienced by the heat
exchanger.
[0002] Heat exchangers are widely used to transfer heat from a
relatively hot fluid to a relatively cold fluid without direct
contact between the fluids.
[0003] A conventional tube heat exchanger is shown in FIGS. 1 and
2. The heat exchanger 2 comprises an inlet manifold 4 and an outlet
manifold 6. The inlet and outlet manifolds 4, 6 are fluidically
coupled by a plurality of tubes 8 which together form a tube matrix
10. The tubes 8 of the tube matrix 10 are coupled at one end to the
inlet manifold 4 and are coupled at the other end to the outlet
manifold 6.
[0004] The tubes 8 of the tube matrix 10 are arranged such that
their longitudinal axes are perpendicular to the longitudinal axes
of the inlet and outlet manifolds 4, 6. A plurality of the tubes 8
are aligned in a plane of the longitudinal axes of the inlet and
outlet manifolds 4, 6 to form a row, and several rows are disposed
side-by-side to form columns of the tube matrix 10.
[0005] As shown in FIGS. 1 and 2, the tubes 8 of the tube matrix 10
are straight. Each tube 8 therefore follows a direct path from the
inlet manifold 4 to the outlet manifold 6 without deviating from a
longitudinal axis between its connection point with the inlet
manifold 4 and its connection point with the outlet manifold 6.
[0006] The inlet and outlet manifolds 4, 6 and tube matrix 10 form
a conduit for the passage of a first fluid through the heat
exchanger 2. Accordingly, the first fluid flows into the heat
exchanger 2 via the inlet manifold 4, passes through the tubes 8 of
the tube matrix 10 and exits the heat exchanger 2 via the outlet
manifold 6.
[0007] A second fluid flows over exterior surfaces of the tubes 8
of the tube matrix 10. The first and second fluids have different
temperatures and therefore heat is transferred between the first
and second fluids.
[0008] FIG. 3 shows a simulated stress distribution for the heat
exchanger 2 under large thermal and pressure loads. In this
simulation, the ends of the inlet and outlet manifolds 4, 6 are
assumed to have a fixed position.
[0009] As shown in FIG. 3, the heat exchanger 2 experiences large
stresses throughout as a result of thermal expansion of the inlet
and outlet manifolds 4, 6 and the tubes 8 of the tube matrix 10.
Increased loads are seen across those tubes 8 which are located
towards the ends of the inlet and outlet manifolds 4, 6 due to the
fixed position of the inlet and outlet manifolds 4, 6 at these
locations.
[0010] Various tube matrix geometries have been proposed to reduce
the stress experienced by heat exchangers under large thermal and
pressure loads.
[0011] For example, FIGS. 4 and 5 show a heat exchanger 102 which
has a tube matrix 110 which is formed of two portions 110a, 110b
comprising U-shaped tubes 108. Each U-shaped portion 110a, 110b is
connected at one end to the inlet manifold 104 and at the other end
to the outlet manifold 106. The U-shaped portions 110a, 110b extend
in opposite directions from the inlet and outlet manifolds 104, 106
to form an oval.
[0012] FIG. 6 shows a simulated stress distribution for the
U-shaped heat exchanger 102 under large thermal and pressure loads.
As can be seen, the stress levels are far reduced for the tube
matrix 102, since the U-shaped tubes 108 are not constrained by the
inlet and outlet manifolds 104, 106. Accordingly, the U-shaped heat
exchanger 102 is insensitive to the displacement constraints.
[0013] However, the U-shaped heat exchanger 102 requires more space
and is heavier than the straight tube matrix 2.
[0014] FIGS. 7 and 8 show another example of a known heat exchanger
202. The heat exchanger 202 has an S-shaped tube matrix 210, with
the tubes 208 of the tube matrix 210 following a serpentine path
between the inlet manifold 204 and the outlet manifold 206.
[0015] Specifically, the tubes 208 of the S-shaped tube matrix 210
comprise first and second straight portions 212a, 212b adjacent the
inlet and outlet manifolds 204, 206 respectively, and first and
second curved portions 214a, 214b disposed between the first and
second straight portions 212a, 212b. The first and second curved
portions 214a, 214b deviate in opposite directions from the axis of
the first and second straight portions 212a, 212b in a plane
defined by the longitudinal axes of the inlet and outlet manifolds
204, 206 to form the S-shape.
[0016] The S-shaped nature of the tube matrix 210 acts to reduce
the thermal stress placed on the heat exchanger 202, without
considerably increasing the size and weight of the heat
exchanger.
[0017] However, as shown in FIG. 9, the gap between adjacent tubes
208 is reduced over the first and second curved portions 214a, 214b
of the S-shaped tube matrix 210. Consequently, the tubes 208 must
be spaced further from one another at the inlet and outlet
manifolds 204, 206 in order to prevent the tubes 208 from
contacting one another. This reduces the number of tubes 208 in the
tube matrix 210 for a fixed size heat exchanger 202 or increases
the size of the heat exchanger 202 for a fixed number of tubes 208.
Furthermore, the curved portions 214a, 214b increase the complexity
of the manufacturing process, thus increasing the cost of the heat
exchanger.
[0018] Further tube matrix geometries are known which use tubes
with additional curved portions; for example, see U.S. Pat. No.
5,058,663. However, although these matrices may reduce thermal
stress, they exacerbate the reduction in the gap between the tubes
and the increased complexity and cost of manufacturing.
[0019] Accordingly, it is desirable to provide a heat exchanger
with a tube matrix which overcomes some or all of the problems
described above.
[0020] In accordance with a first aspect of the invention there is
provided a heat exchanger comprising: an inlet manifold; an outlet
manifold; and a tube matrix comprising a plurality of tubes, each
tube being fixedly connected at one end to the inlet manifold and
at the other end to the outlet manifold; wherein each tube extends
generally along a longitudinal axis defined between the connection
of the tube with the inlet manifold and the connection of the tube
with the outlet manifold; and wherein a single portion of each tube
is offset to one side of the longitudinal axis.
[0021] The tubes may be fixedly connected between the inlet
manifold and outlet manifold independently from each other.
[0022] The tubes may each be separated from an adjacent tube by a
substantially similar gap at corresponding portions along the
longitudinal axis.
[0023] The tubes may be generally C-shaped.
[0024] The offset portion may comprise a curved portion which
curves away from the longitudinal axis.
[0025] The curved portion may have a constant curvature.
[0026] The offset portion may comprise a straight portion and pair
of angled portions which offset the straight portion from the
longitudinal axis.
[0027] The offset portion may be offset in a plane defined by a
longitudinal axis of the inlet and outlet manifolds.
[0028] The tubes may be arranged in one or more rows in a plane
defined by a longitudinal axis of the inlet and outlet
manifolds.
[0029] A plurality of rows may be disposed side-by-side to form
columns.
[0030] A minimum gap between adjacent tubes over the offset portion
may be greater than 2/3 of the maximum gap between adjacent tubes
at the inlet and outlet manifolds.
[0031] The offset portion may be 30-70% of the total length of the
tube.
[0032] The offset portion may allow deformation of the tubes during
thermal expansion, thereby reducing thermal stress experienced by
the heat exchanger. Furthermore, the offset portion does not
considerably affect the gaps between adjacent tubes. Consequently,
the size of the heat exchanger is not significantly increased, if
at all. This may make the heat exchanger of the present invention
particularly suitable for installation in an aero-engine, where
space is at a premium.
[0033] In addition, the manufacturing process for the single offset
portion is simple and requires only one bending process.
Accordingly, the manufacturing costs are minimised.
[0034] The present invention results in a high efficiency, high
temperature, high pressure, lightweight and compact heat exchanger
design.
[0035] According to another aspect of the invention there is
provided a heat exchanger comprising an inlet manifold, an outlet
manifold, and a tube array comprising a plurality of tubes, wherein
the tube array generally extends along a longitudinal axis between
the inlet manifold and the outlet manifold, and wherein the tube
array comprises an offset portion that is offset from the
longitudinal axis. There may be a single offset portion. Each tube
may comprise an offset portion that is offset to the same side. The
tube array may comprise at least one longitudinally extending
portion and an offset portion. The tube array may comprise first
and second longitudinally extending portions coupled to the inlet
and outlet manifolds respectively, with the offset portion disposed
between the first and second longitudinally extending portions. The
single offset portion may be directly between the first and second
longitudinally extending portions. The offset portion may be
generally C-shaped.
[0036] For a better understanding of the present invention, and to
show more clearly how it may be carried into effect, reference will
now be made by way of example to the accompanying drawings, in
which:
[0037] FIG. 1 is a cross-sectional view of a conventional heat
exchanger having a straight tube matrix in a plane defined by a
longitudinal axis of the tubes;
[0038] FIG. 2 is a cross-sectional view of the heat exchanger of
FIG. 1 in a plane defined by a longitudinal axis of the
manifolds;
[0039] FIG. 3 is a simulated stress distribution for the heat
exchanger of FIGS. 1 and 2;
[0040] FIG. 4 is a cross-sectional view through a conventional heat
exchanger having a U-shape tube matrix in a plane defined by a
longitudinal axis of the tubes;
[0041] FIG. 5 is a cross-sectional view of the heat exchanger of
FIG. 5 in a plane defined by a longitudinal axis of the
manifolds;
[0042] FIG. 6 is a simulated stress distribution for the heat
exchanger of FIGS. 4 and 5;
[0043] FIG. 7 is a cross-sectional view through a conventional heat
exchanger having a S-shaped matrix in a plane defined by a
longitudinal axis of the tubes;
[0044] FIG. 8 is a cross-sectional view of the heat exchanger of
FIG. 7 in a plane defined by a longitudinal axis of the
manifolds;
[0045] FIG. 9 is an enlarged view of a portion of FIG. 8;
[0046] FIG. 10 is a cross-sectional view through an embodiment of a
heat exchanger in a plane defined by a longitudinal axis of the
manifolds;
[0047] FIG. 11 is an enlarged view of a portion of FIG. 10;
[0048] FIG. 12 is a simulated stress distribution for the heat
exchanger of FIG. 11;
[0049] FIG. 13 is a comparative graph of thermal and
thermo-mechanical stress for conventional heat exchangers and the
heat exchanger of the present invention; and
[0050] FIG. 14 is a cross-sectional view through another embodiment
of a heat exchanger in a plane defined by a longitudinal axis of
the manifolds.
DETAILED DESCRIPTION
[0051] FIG. 10 shows a heat exchanger 302 according to an
embodiment of the invention. The heat exchanger 302 comprises an
inlet manifold 304 and an outlet manifold 306. The inlet and outlet
manifolds 304, 306 are fluidically coupled by a plurality of tubes
308 which together form a tube matrix 310. The tubes 308 of the
tube matrix 310 are fixedly connected, for example, by welding, at
one end to the inlet manifold 304 and are coupled at the other end
to the outlet manifold 306.
[0052] A plurality of the tubes 308 are aligned in a plane defined
by the longitudinal axes of the inlet and outlet manifolds 304, 306
to form a row, and several rows are disposed side-by-side to form
columns of the tube matrix 310 arranged along a common plane.
[0053] Each tube 308 comprises first and second straight portions
312a, 312b adjacent the inlet and outlet manifolds 304, 306
respectively, and a single curved portion 314 disposed between the
first and second straight portions 312a, 312b. The curved portion
314 deviates from a longitudinal axis of the tube 308 between its
connection point with the inlet manifold 304 and its connection
point with the outlet manifold 306. As shown in FIG. 10, the curved
portion 314 is offset in the plane defined by the longitudinal axes
of the inlet and outlet manifolds 304, 306. The size of the offset
from this longitudinal axis is defined as the offset length. The
curved portion 314 follows a single curvature between the first
straight portion 312a and the second straight portion 312b.
Accordingly, the tube matrix 310 is generally C-shaped. Further,
each of the tubes is separated from adjacent tubes by a similar gap
at corresponding portions along the length of the tubes and are
held between the manifolds independently of each other in the
present embodiment, although supporting members may be incorporated
between each of the tubes to help maintain a common gap
therebetween.
[0054] The inlet and outlet manifolds 304, 306 and tube matrix 310
form a conduit for the passage of a first fluid through the heat
exchanger 302. Accordingly, the first fluid flows into the heat
exchanger 302 via the inlet manifold 304, passes through the tubes
308 of the tube matrix 310 and exits the heat exchanger 302 via the
outlet manifold 306.
[0055] As shown in FIG. 11, whilst the gap between adjacent tubes
308 is reduced over the curved portion 314, the size of this
reduction is minimised. Consequently, the spacing between the tubes
308 at the inlet and outlet manifolds 304, 306 is not significantly
effected.
[0056] The curved portion 314 absorbs thermal expansion by
elastically deforming. Thus, the curved portion 314 reduces the
thermal stress experienced by the heat exchanger 302.
[0057] The geometry of the tube matrix 310 is optimised in order to
minimise the thermal stress experienced by the heat exchanger 302.
Accordingly, a design of experiment (DOE) analysis was performed
using the Central Composite Design method and sensitivity analysis
and response surface analysis was performed using the results of
the DOE analysis.
[0058] From the results of the sensitivity analysis it was shown
that the offset length and the length of the straight portions
312a, 312b (straight length) were found to be the most significant
factors in reducing the thermal stress.
[0059] The response surface analysis was performed in order to find
the optimum values for the offset length, the straight length and
the curvature of the curved portion 314 which minimise the thermal
stress, whilst maintaining a minimum gap between adjacent tubes
over the curved portion 314 of 2/3 the maximum gap at the inlet and
outlet manifolds 304, 306.
[0060] The result of this process showed that the thermal stress at
the ends of the heat exchanger 302 (i.e. adjacent the inlet and
outlet manifolds 304, 306) decreases as the straight length and the
offset length increase. Furthermore, the thermal stress at the
centre of the heat exchanger 302 (i.e. midway between the inlet and
outlet manifolds 304, 306) was shown to decrease with increasing
offset length and decreasing straight length.
[0061] The thermal stress was found to be at a minimum when the:
[0062] inside diameter of the tubes 308 is approximately 0.9 times
the outside diameter; [0063] the length of the tubes 308 is
approximately 107 times the outside diameter; [0064] the offset
length is approximately 13.3 times the outside diameter; [0065] the
length of the straight portions 312a, 312b is approximately 23.3
times the outside diameter; and [0066] the radius of curvature
between the straight portions 312a, 312b and the curved portion 314
is approximately 13.3 times the outside diameter.
[0067] Accordingly, the dimensions of the heat exchanger are
preferably as follows: [0068] the diameter of the tubes 308 is
approximately 1.0 to 5.0 mm; [0069] the length of the tubes 308 is
approximately 100-500 mm; [0070] the length of the curved portion
314 is approximately 30-70% of the total length; and [0071] the
offset length is approximately 10-100 mm.
[0072] FIG. 12 shows a simulated stress distribution for the heat
exchanger 302 under large thermal and pressure loads. As shown, the
heat exchanger 302 experiences larger stresses at its centre over
the portion 314 as a result of thermal expansion and deformation of
the tubes 308. However, as shown in FIG. 13, the stress experienced
at the centre and at the ends of the heat exchanger 302 is far
lower than for the straight tube heat exchanger 2, and comparable
to the U-shaped heat exchanger 102.
[0073] FIG. 14 shows a heat exchanger 402 according to another
embodiment of the invention. The heat exchanger 402 comprises an
inlet manifold 404 and an outlet manifold 406. The inlet and outlet
manifolds 404, 406 are fluidically coupled by a plurality of tubes
408 which together form a tube matrix 410. The tubes 408 of the
tube matrix 410 are coupled at one end to the inlet manifold 404
and are coupled at the other end to the outlet manifold 406.
[0074] A plurality of the tubes 408 are aligned in a plane of the
longitudinal axes of the inlet and outlet manifolds 404, 406 to
form a row, and several rows are disposed side-by-side to form
columns of the tube matrix 410.
[0075] Each tube 408 comprises first and second straight portions
412a, 412b adjacent the inlet and outlet manifolds 404, 406
respectively, and a single offset portion 416 disposed between the
first and second straight portions 412a, 412b. The offset portion
414 deviates from a longitudinal axis of the tube 408 between its
connection point with the inlet manifold 404 and its connection
point with the outlet manifold 406. As shown in FIG. 14, the curved
portion 414 is offset in a plane of a longitudinal axis of the
inlet and outlet manifolds 404, 406. The size of the offset from
this longitudinal axis is defined as the offset length. The offset
portion 416 comprises a third straight portion 418 which is
connected to the first and second straight portions 412a, 412b by
first and second angled portions 420a, 420b. The tubes 408 are
curved at the intersections between the first/second straight
portions 412a, 412b and the first/second angled portions 420a,
420b, and between the first and second angled portions 420a, 420b
and the third straight portion 418. The third straight portion 418
is arranged such that it is offset from, but parallel with, the
first and second straight portions 412a, 412b. Accordingly, the
tube matrix 410 is generally C-shaped.
[0076] Again, whilst the gap between adjacent tubes 408 is reduced
over the curved intersections of the offset portion 416, the size
of this reduction is minimised. Consequently, the spacing between
the tubes 408 at the inlet and outlet manifolds 404, 406 is not
significantly effected.
[0077] The offset portion 416 absorbs thermal expansion by
elastically deforming. Thus, the offset portion 416 reduces the
thermal stress experienced by the heat exchanger 402.
[0078] The first and second straight portions and the offset
portion may be integrally formed or may be separate components
which are subsequently joined together to form the tube 308,
408.
[0079] It should be noted that the tubes need not have a circular
cross-section and could have any other cross-section, so long as
they provide a conduit for the passage of a fluid from the inlet
manifold to the outlet manifold.
* * * * *