U.S. patent application number 12/311851 was filed with the patent office on 2010-12-02 for heat exchanger.
Invention is credited to Drummond Watson Hislop, Stephen David Joseph.
Application Number | 20100300666 12/311851 |
Document ID | / |
Family ID | 37491598 |
Filed Date | 2010-12-02 |
United States Patent
Application |
20100300666 |
Kind Code |
A1 |
Hislop; Drummond Watson ; et
al. |
December 2, 2010 |
Heat exchanger
Abstract
A heat exchanger is formed with tessellating conduits 4 passing
therethrough. The tessellating conduits having transverse
cross-sectional shapes which together substantially completely
cover the transverse plane to the heat exchange 2. The tessellating
conduits may be the outer conduits 18 within conduit pairs formed
of an outer conduit 18 and an inner conduit 22. The outer conduits
may have a cross-section that is a regular hexagon and the inner
conduits may have a cross-section that is a circle. The heat
exchanger can advantageously be formed by selective remelting of
material with an energy beam.
Inventors: |
Hislop; Drummond Watson;
(London, GB) ; Joseph; Stephen David; (Saratoga,
AU) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Family ID: |
37491598 |
Appl. No.: |
12/311851 |
Filed: |
October 16, 2007 |
PCT Filed: |
October 16, 2007 |
PCT NO: |
PCT/GB2007/003931 |
371 Date: |
August 27, 2009 |
Current U.S.
Class: |
165/173 ;
165/172; 29/890.031 |
Current CPC
Class: |
B22F 10/20 20210101;
F28F 7/02 20130101; Y10T 29/49352 20150115; F28D 7/0041 20130101;
B22F 10/00 20210101; B23K 1/0056 20130101; Y02P 10/25 20151101;
B23K 2101/14 20180801; F28D 7/106 20130101; F28F 1/04 20130101;
B22F 5/10 20130101 |
Class at
Publication: |
165/173 ;
165/172; 29/890.031 |
International
Class: |
F28F 9/02 20060101
F28F009/02; F28F 1/10 20060101 F28F001/10; B21D 53/02 20060101
B21D053/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 16, 2006 |
GB |
0620512.4 |
Claims
1. A heat exchanger comprising: a body with a portion having a
plurality of substantially parallel fluid carrying tessellating
conduits passing therethrough, wherein said tessellating conduits
have transverse cross-sections with one or more shapes that
substantially completely cover a plane through said portion of said
body transverse to said tessellating conduits by repeated use of
said one or more shapes.
2. A heat exchanger as claimed in claim 1, wherein said
tessellating conduits have transverse cross-sections with one shape
that regularly tessellates to cover said plane.
3. A heat exchanger as claimed in claim 2, wherein said
tessellating conduits have regular hexagonal transverse
cross-sections.
4. A heat exchanger as claimed in claim 1, wherein said
tessellating conduits are outer conduits of respective conduit
pairs, each conduit pair being an outer conduit and an inner
conduit disposed within said outer conduit over at least a part of
said outer conduit.
5. A heat exchanger as claimed in claim 4, wherein said outer
conduit and said inner conduit within a conduit pair are connected
to receive respective different fluids.
6. A heat exchanger as claimed in claim 4, wherein said inner
conduits have a substantially circular transverse
cross-section.
7. A heat exchanger as claimed in claim 4, wherein within a conduit
pair a plurality of arms extend from said inner conduit to said
outer conduit to hold said inner conduit in position.
8. A heat exchanger as claimed in claim 1, wherein said
tessellating conduits are arranged in concentric rings with
tessellating conduits in adjacent rings being connected to receive
respective different fluids.
9. A heat exchanger as claimed in claim 1, wherein neighbouring
tessellating conduits have polygonal transverse cross-sections and
walls between neighbouring tessellating conduits are shared such
that all walls of a tessellating conduit completely surrounded by
neighbouring tessellating conduits are shared walls.
10. A heat exchanger as claimed in claim 1, wherein an edge conduit
being a tessellating conduit not completely surrounded by other
tessellating conduits has a transverse cross-section differing from
said one or more shapes.
11. A heat exchanger as claimed in claim 10, wherein said edge
conduit has at least one wall shared with a neighbouring
tessellating conduit and at least one wall not shared with a
neighbouring tessellating conduit and thicker than said at least
one wall shared with a neighbouring tessellating conduit.
12. A heat exchanger as claimed in claim 1, wherein conduit walls
of said tessellating conduits thicken proximal to vertices of said
one or more shapes.
13. A heat exchanger as claimed in claim 12, wherein said conduit
walls are curved at said vertices.
14. A heat exchanger as claimed in claim 1, wherein said body is
formed of remelted material being layers of material remelted with
an energy beam to form part of said body prior to addition of a
successive layer.
15. A heat exchanger as claimed in claim 1, comprising one or more
fluid manifolds connected to said tessellating conduits, said one
or more fluid manifolds being formed of remelted material being
layers of material remelted with an energy beam to form part of
said manifold prior to addition of a successive layer.
16. A heat exchanger as claimed in claim 1, wherein said heat
exchanger has surface area to volume ratio of greater than one of:
5000 m.sup.2/m.sup.3; 10000 m.sup.2/m.sup.3; and 15000
m.sup.2/m.sup.3.
17. A method of making at least a portion of a heat exchanger, said
portion having a plurality of tessellating conduits passing
therethrough, said method comprising the steps of: providing a
plurality of successive layers of a material to be remelted; and
energy beam remelting predetermined regions of each layer in
accordance with a predetermined design, said energy beam remelting
of each layer being performed prior to addition of a successive
layer; wherein said predetermined regions of each layer subjected
to energy beam remelting form solid structures within said layer
and said energy beam remelting of each layer fuses said
predetermined regions of each layer to remelted regions of a
preceding layer; and said tessellating conduits have transverse
cross-sections with one or more shapes that substantially
completely cover a plane through said portion of said body
transverse to said tessellating conduits by repeated use of said
one or more shapes.
Description
[0001] This invention relates to the field of heat exchangers.
[0002] Published PCT Patent Application WO-A-2006/064202 describes
a compact heat exchanger and reactor (CHXR) that can be
manufactured by energy beam methods, such as selective laser
remelting (SLR). Compact heat exchangers formed in this way are
capable of providing large numbers of fine conduits with associated
complex manifolding arrangements in a way that produces a high heat
exchange surface area to volume ratio. However, a problem with such
heat exchangers is that the manufacturing process can be
disadvantageously slow and expensive. The remelting of material to
form the conduits takes a significant amount of time and
accordingly the greater the wall material requiring remelting that
is present within the heat exchanger design, the longer it will
take to manufacture that heat exchanger. A further problem is that
whilst it is desirable to have thin conduit walls so as to promote
high levels of heat transfer, significant pressure differentials
can exist between different sides of the walls resulting in it
being necessary to provide a greater wall thickness in order to
withstand the forces resulting from such pressure differences. Such
thickened conduit walls again take longer to manufacture and reduce
the level of heat transfer.
[0003] Viewed from one aspect the present invention provides a heat
exchanger comprising:
[0004] a body with a portion having a plurality of substantially
parallel fluid carrying tessellating conduits passing therethrough,
wherein
[0005] said tessellating conduits have transverse cross-sections
with one or more shapes that substantially completely cover a plane
through said portion of said body transverse to said tessellating
conduits by repeated use of said one or more shapes.
[0006] The present invention recognises that tessellating conduits
having cross-sections with shapes that fit together substantially
to completely cover a plane transverse to those conduits result in
a heat exchanger with a reduced amount of wall material. This makes
manufacturing quicker and less expensive as well as providing other
advantages. The tessellating shapes provide arrangements in which
at least some neighbouring conduits can have the same contained
fluid pressure and accordingly reduces the forces exerted on the
conduit walls in a way which enable such conduit walls to be
advantageously thinner.
[0007] Whilst it will be appreciated that there are many shapes,
and combinations of shapes, which have the property of tessellating
to cover a plane, design of the heat exchanger is advantageously
simplified when the tessellating conduits have one shape which
regularly tessellates to cover the plane.
[0008] Whilst regular tessellation can be achieved by a variety of
shapes, a particularly preferred shape is that of a regular
hexagon. Regular hexagons have internal angles which are not too
sharp (i.e. reducing potential stress risers) and tend toward a
circular cross-section which is able to provide a good degree of
strength against internal or external pressure.
[0009] The tessellating conduits may each form an outer conduit of
a conduit pair with an inner conduit being disposed within the
outer conduit along at least a part of the outer conduit. Such a
pipe-in-pipe arrangement is capable of providing a high level of
heat transfer area to volume ratio. The tessellating outer conduits
substantially completely fill the plane of a transverse
cross-section of the heat exchanger body in a way that avoids
redundant "dead spaces" which might reduce the heat transfer
surface area to volume ratio and might also reduce the surface
porosity. If these "dead spaces" were to be filled with material
that material would require remelting and increase manufacture
time. Simultaneously, the inner conduits are surrounded by the
fluid contained within the outer conduits in a way which gives a
high degree of heat transfer.
[0010] The inner conduits can have a variety of different shapes,
but a circular cross-section provides a good degree of strength for
the amount of material used.
[0011] The inner conduits may be held in position by arms extending
from the inner conduits to the outer conduits. This arrangement is
capable of providing a high degree of strength in the heat
exchanger body.
[0012] Returning to consideration of the tessellating conduits
themselves, the tessellating conduits may be arranged in concentric
rings with adjacent rings being connected to receive different
fluids. Thus, rings of tessellating conduits can together give rise
to a collection equivalent to a pipe-in-pipe arrangement, even
though conduit pairs are not being-used. It would also be possible
to use conduit pairs in combination with such a concentric ring
arrangement.
[0013] The efficiency of the present embodiments in reducing the
amount of material needed to form the body of the heat exchanger
are such that a tessellating conduit completely surrounded by
neighbouring tessellating conduits will share all of its walls with
respective tessellating conduits. These shared walls will be
monolithic (formed of a single piece of material).
[0014] It will be appreciated that at the edges of the heat
exchanger body, the tessellating conduits will not be surrounded by
neighbouring tessellated conduits. Such edge conduits can have a
different shape to those within the main body of the heat exchanger
and may also have thickened exterior walls to better resist
pressure differences.
[0015] The conduits may be further strengthened by having thickened
walls proximal to their vertices and having curved vertices rather
than sharp corners.
[0016] Whilst heat exchangers having the structural form described
above are advantageous however manufactured, they are particularly
well suited to manufacture from remelted material, that is layers
of material remelted with an energy beam to form part of the body
prior to addition of a successive layer of material that will be
remelted.
[0017] It will be appreciated that manifolds are needed to connect
to the conduits formed within the heat exchanger body and these
will have a complex form given the detailed and complex form of the
heat exchanger body. The use of remelted layers of material to
manufacture such manifolds is highly convenient.
[0018] Whilst the heat exchangers formed in accordance with the
present technique can have a high surface area to volume ratio
compared to conventional heat exchangers, this can in some
embodiments of the invention be made to exceed 5000
m.sup.2/m.sup.3, or in more preferred embodiments 10000
m.sup.2/m.sup.3 or in still more preferred to embodiments 15000
m.sup.2/m.sup.3. Some of these gains may be counteracted by an
associated increase in pressure drop through the heat exchanger,
although this may be addressed by the use of a larger number of
shorter conduits.
[0019] Viewed from another aspect the present invention provides a
method of malting at least a portion of a heat exchanger, said
portion having a plurality of tessellating conduits passing
therethrough, said method comprising the steps of:
[0020] providing a plurality of successive layers of a material to
be remelted; and
[0021] energy beam remelting predetermined regions of each layer in
accordance with a predetermined design, said energy beam remelting
of each layer being performed prior to addition of a successive
layer;
[0022] wherein said predetermined regions of each layer subjected
to energy beam remelting form solid structures within said layer
and said energy beam remelting of each layer fuses said
predetermined regions of each layer to remelted regions of a
preceding layer; and
[0023] said tessellating conduits have transverse cross-sections
with one or more shapes that substantially completely cover a plane
through said portion of said body transverse to said tessellating
conduits by repeated use of said one or more shapes.
[0024] Example embodiments of the invention will now be described,
by way of example only, with reference to the accompanying drawings
in which:
[0025] FIG. 1 schematically illustrates a transverse section
through a heat exchanger body formed of a plurality of tessellating
conduits;
[0026] FIGS. 2 and 3 illustrate further examples of shapes of
conduits which can completely cover a transverse plane;
[0027] FIG. 4 is a diagram schematically illustrating a
manufacturing process for a heat exchanger,
[0028] FIG. 5 is a section through a small number of conduit
pairs;
[0029] FIG. 6 is a cross-section through a heat exchanger formed of
conduit pairs with the outer conduit of each pair being a
tessellating conduit;
[0030] FIG. 7 is a longitudinal section through the heat exchanger
body of FIG. 6; and
[0031] FIG. 8 schematically illustrates the heat exchanger body
with manifolds attached at one face.
[0032] FIG. 1 schematically illustrates a transverse section
through a heat exchanger body 2. This heat exchanger body 2 is
formed of a plurality of tessellating conduits 4 in the form of
regular hexagons. Starting at the centre of the heat exchanger body
2 these tessellating conduits 4 are arranged in concentric rings.
The flow direction in alternate centric rings is opposite. Thus,
the centremost conduit has a flow direction corresponding to
upwards out of the Figure, the neighbouring six tessellating
conduits have a flow direction downwards in to the Figure and so
forth. The shared walls between the tessellating conduits 4 are
monolithic (integrally formed of solid material).
[0033] Within the body of the heat exchanger 2, a tessellating
conduit 4 will be completely surrounded by neighbouring
tessellating conduits. Each wall forming such a tessellating
conduit is shared with one of its neighbouring tessellating
conduits 4. The walls are thickened towards the vertices of the
cross-section so as to better resist stress. Furthermore, the
vertices are curved rather than having sharp corners so as to
reduce stress risers.
[0034] At the edge of the heat exchanger body 2 the tessellating
conduits 4 are not completely surrounded by neighbouring
tessellating conduits. Accordingly, the shapes of these edge
tessellating conduits 5 can differ from those within the main body
of the heat exchanger 2. Furthermore, the outermost walls of these
edge conduits may be thickened relative to the walls within the
main body of the heat exchanger so that these edge conduit 5 can
better resist higher pressure differences across the outermost
walls.
[0035] As previously mentioned, the alternating concentric rings
are connected by appropriate manifolds (not shown) to pass fluid in
different directions. These fluids may be different fluids, such as
a combusting air gas mixture in one set of rings and water to be
heated in another set of rings. The inner surfaces of the
tessellating conduits 4 containing the combusting air gas mixture
may be coated with an appropriate catalyst to promote such
combustion.
[0036] FIG. 2 illustrates another example form of a collection of
tessellating shapes which can be arranged to form tessellating
conduits 4 within a heat exchanger. It will be appreciated that the
view in FIG. 2 is a transverse cross-section through a portion of a
heat exchanger using such a conduit shape.
[0037] FIG. 3 illustrates a further example of tessellating
conduits 4, in this case using two different shapes which are
repeated so as to completely fill the plane, namely a square and a
triangle.
[0038] It will be appreciated that many other forms of tessellating
shapes and patterns are possible and that the use of such patterns
reduces the amount of wall material required since there will not
be "dead spaces" between the conduits needing to be filled with
excessive wall material.
[0039] FIG. 4 schematically illustrates a device for manufacturing
heat exchangers in accordance with the present techniques. The
manufacturing technique may be the same as described in
WO-A-2006/064202 (the entire content of which is incorporated
herein by reference, including the details of manufacturing
technique and the preferred conduit forms and features). In
particular, hoppers 6 of powdered material are used to successively
dispense that powdered material to distributed by a roller 8 across
the upper surface of a target body forming region 10. A partially
formed heat exchanger body 12 is illustrated. This partially formed
heat exchanger body 12 has a thin layer of powdered material spread
across its upper surface by the roller 8. A scanned energy beam
produced by, for example, a laser 14 and a scanning mirror 16 is
used to in selectively remelt portions of this powdered material at
desired points above the partially formed heat exchanger body 12 so
as to form the solid walled portions for that next layer. In this
way, the 3-dimensional shape of the heat exchanger body 12 is built
up on a layer-by-layer basis with the walls between conduits being
solid monolithic structures. This manufacturing technique allows a
great deal of flexibility to be achieved in the 3-dimensional form
of the shapes produced and accordingly permits complex and highly
detailed, as well as finely formed, shapes of the heat exchangers
described herein to be achieved.
[0040] FIG. 5 illustrates a small portion of a transverse section
through a heat exchanger body in accordance with one example
embodiment. In this example embodiment the tessellating conduits
have a transverse cross-section in the form of a regular hexagon
18, 20. Within each of these tessellating conduits there is
disposed an inner conduit 22, 24 having a substantially circular
transverse cross-section. Arms 26 extend between the outer conduits
18, 20 (tessellating conduits) and the inner conduits 22, 24. The
outer conduits 18, 20 and the inner conduits 22, 24 form conduit
pairs each having one outer conduit 18 and one inner conduit
22.
[0041] In the example shown, the outer conduits 18, 20 carry fluid
in one direction (e.g. up from the plane of the drawing), whereas
the inner conduits 22, 24 carry fluid in the opposite direction
(e.g. down into the plain of the drawing). As the outer conduits
18, 20 neighbour other outer conduits carrying the same fluid in
the same direction they will tend to have the same internal
pressure on either side of the walls forming the boundary between
those outer conduits 18, 20. This reduces the stress on these walls
an enables them to be thinner requiring less material to be used.
It will be appreciated that heat transfer also occurs due to heat
conduction through the walls and the arms 26, as well as directly
from the fluid within the conduits across the wall of the inner
conduits 22, 24.
[0042] The inner conduits 22, 24 are parallel with and pass along
at least a portion of the outer conduits so as to form a
pipe-in-pipe arrangement.
[0043] The dimensions given in FIG. 5 are for one example
embodiment and are in millimetres. It will be seen from this that
the heat exchange body of this example embodiment provides fine
conduits with wall thicknesses of 0.2 mm. This type of structure is
well suited to manufacture by the selective laser remelting
technique of FIG. 4.
[0044] FIG. 6 illustrates a transverse section through a heat
exchanger body 28 formed of a large number of the conduit pairs 18,
22 illustrated in FIG. 5. The conduit pairs at the outer edge of
the heat exchanger body 28 can have a different shape
(cross-section), or in this example embodiment are provided with
greatly thicker walls. Such a heat exchanger 28 can achieve a high
value for the ratio between the heat exchange surface area and the
volume of the heat exchanger. The present technique can be used to
obtain a value for this ratio of greater than 5000 metre squared
per cubic metre. More preferred embodiments can increase this to
greater than 10000 metre square per cubic metre or even 15000 metre
squared per cubic metre, although there may be an accompanying
increase in pressure drop.
[0045] FIG. 7 is a longitudinal section through the heat exchanger
28 showing the outer conduit 22 and the inner conduit 18 in one
example conduit pair.
[0046] FIG. 8 illustrates the heat exchanger body 28 with manifolds
30, 32 respectively provided to connect to the outer conduits 22
and the inner conduits 18. These manifolds, 30, 32 have a complex
form and are well suited to manufacture with the selective laser
beam remelting techniques since the manifold passages (including
many collectors) have to pass between one another and be gathered
and merged into the major inlets and outlets. It will be
appreciated that corresponding manifolds will be provided on the
opposite face of the heat exchanger body 28, although these are not
shown in FIG. 8.
* * * * *