Note: Descriptions are shown in the official language in which they were submitted.
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Heat Exchanger
The present disclosure relates to a shell and tube type heat exchanger and a
method of
operating such a heat exchanger. The heat exchanger may have applications in
aerospace
systems, such as gas turbine engines and hybrid rocket type engines.
Background
Known heat exchangers include shell and tube arrangements which typically
comprise a
bundle of tubes within a shell. One fluid passes through the bundle of tubes
and another fluid
passes through the volume of the shell around the bundle of tubes. With the
fluids initially at
different temperatures, heat transfer between the fluids results. Known
arrangements however
have limitations in their application due to materials and their associated
mass, which can
make them unsuitable for applications which call for a light weight and
efficient design.
The present disclosure seeks to address and/or at least ameliorate to a
certain degree the
problems associated with the prior art.
Summary
According to a first aspect of the disclosure, there is provided:
A shell and tube type heat exchanger comprising:
a shell;
a tube arrangement within said shell, said tube arrangement comprising a flow
tube, wherein
said flow tube furcates at a plurality of nodes along its length; and
a tube matrix fluidly coupled to said flow tube.
Advantageously, with successive furcation or branching of the flow tube, such
a tube
arrangement can provide for flow tubes with ultimately quite small cross-
sections, e.g.. less
than 100 m diameter, fluidly coupled to a single inlet at one end and fluidly
coupled to a tube
matrix at the other.
The node points are positions along the length of the flow tube at which the
tube furcates or
branches.
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Optionally, at a respective node or branching point, the flow tube furcates or
branches into a
plurality of sub-tubes.
The shell may be formed adjacent the tube matrix and the tubes of the matrix
may be coupled
to the shell with one or more webs or fins. Such an arrangement may
advantageously have
applications where only one matrix is required such as in low pressure heat
exchanger
applications. The shell may be formed integrally with the matrix for example,
by an additive
manufacturing technique. Materials may include metals, for example, 316L
stainless steel.
The sub-tubes may be relatively smaller in diameter to the preceding portion
of the flow tube
such that the diameter of the tubes progressively decrease in size with
subsequent furcation.
Such an arrangement can provide performance advantages with increasing overall
surface
area of the increasing number of sub-tubes.
The progressive furcation of the flow tubes into sub-tubes at node points
along the length of
the flow tube can have a quasi-fractal form. This means that the furcating
pattern repeats in
an identical or similar manner at each node.
Each respective sub-tube may further furcate or branch at nodes which are
aligned, for
example in a common flat plane extending generally perpendicular to the extent
of the sub-
tubes.
Optionally, the respective, corresponding nodes at which furcation or
branching occurs in each
sub-tube may be offset or may be aligned in a curved plane. Such an
arrangement can allow
for a more compact branching structure.
The internal cross-sectional area of the flow tube can optionally remain
constant or generally
constant through or in the region of a furcation or branching node. The means
that the total
cross-section of the flow tube through the node or branching point remains
constant or
generally constant as it subdivides. This can avoid pressure concentration in
the flow tube at
the node points.
The cross-section of the flow tube may be generally circular between the node
points. The
cross-section of the flow-tube may have a non-circular form, for example a
tear-drop shape.
The tubes can be configured such that the rounded nose of the tear-drop facing
into the flow
of the fluid within the volume of the shell. This can reduce press-drop of the
fluid passing
through the shell.
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The flow tube may be supported by webs which can serve as baffles in the
volume of the shell.
These can advantageously direct the flow or fluid within the shell and can
also avoid stagnant
flow regions.
The tube arrangement may have a fluid inlet or outlet for the introduction of
a heat transfer
medium.
Optionally, the flow tube further comprises a principal furcating node at
which the tube inlet
furcates into a plurality of sub-tubes.
At each node, the flow-tube may furcate or branch into, for example, two,
three or four sub-
tubes. At a subsequent node, each of the sub-tubes may each furcate or branch
into an equal
or different number of further sub-tubes. This furcating or branching pattern
may continue to
provide an ever-increasing number of sub-tubes.
Optionally, said tube arrangement is formed as a tube module. This can allow
for scaling of
the heat exchanger. In addition, a modular design allows for modules to be
serviced or
substituted during service.
The tube module may have a common inlet for all the sub-tubes of the module.
The tube
module may have a common outlet for all the sub-tubes of the module.
Optionally, the heat exchanger comprises a plurality of tube modules. In this
way, the heat
exchanger may be sized according to requirements by selecting a number of
modules.
Optionally, each of the plurality of tube modules are substantially identical.
Optionally, each of the plurality of tube modules are arranged about a
rotational axis of the
shell.
Optionally, each of the plurality of tube modules are arranged angularly
spaced about the
longitudinal axis of the shell.
Optionally, each tube module is connected to a common fluid inlet. The common
fluid inlet may
be fluidly coupled to a web of tubes which fluidly couple to each module.
Optionally, the plurality of tube modules form a generally ring shaped
structure.
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Optionally, the ring shaped structure comprises an aperture defined
therethrough.
Optionally, the aperture is located on the longitudinal axis of the shell.
Optionally, a plug is provided in said aperture in the ring shaped structure.
The plug may have
a surface area which is around 10% or less than the overall cross-sectional
area of the shell
at that point.
Optionally, said tube matrix is provided in said module. Each module may
comprise a tube
matrix. A tube matrix can provide for a relatively dense arrangement of tubes,
for example a
spacing less than twice the diameter of a tube within the tube matrix, such as
substantially
equal to or less than the diameter of a tube within the tube matrix, The flow
tubes may
progressively furcate into smaller sub-tubes which are in fluid communication
with the tube
matrix. The section of the module in which the flow tube furcates may provide
a manifold for
fluid delivery to the matrix. A tube matrix may comprise one hundred, a
thousand or more tubes
and be sized accordingly to application. The tubes of the matrix may be
equally spaced from
one another. The tubes of the matrix may be coupled to one another, for
example, along their
outer edges. The matrix may provide a mass of tubes, which may be arranged in
an array. The
matrix may be arranged with the tube arrangement within the shell.
The tube matrix may comprise tubes at their minimum diameter in the module.
The tube matrix
may provide the greatest surface area and hence the majority of heat transfer
in the heat
exchanger.
The outer profile of the matrix may be shaped dependent on application. For
example, the
matrix may have an outer profile or perimeter which is in the form of a
segment of a ring, a
quadrilateral, a circle, or any other shape. This allows the matrix to
advantageously to fit the
profile of the shell or the space or volume in which it is positioned.
The volumetric form of the matrix may be that of a cuboid, a cylinder or any
other shape.
Optionally, the tube matrix comprises a plurality of generally parallel tubes.
The tubes of the
matrix may be arranged spaced from one another, for example in an array. The
tubes of the
matrix may be arranged in substantially linear rows. The rows may be parallel.
The spacing of
the tubes of the matrix may be even. The tubes in adjacent rows may be offset
from one
another and/or aligned in alternate rows.
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Optionally, the tube matrix is aligned such that the tubes of the matrix
extend axially with
respect to the shell.
Optionally, the extent of the tube matrix is positioned generally on a plane
perpendicular to the
axis of the shell.
Supporting fins or ribs may be provided between adjacent tubes within the
matrix. The fins
may extend along the full length of a tube in the matrix.
Optionally, discrete supporting fins or ribs may be provided at spaced
intervals along the length
of the tubes of the matrix between adjacent tubes within the matrix. Such an
arrangement of
fins or ribs can assist with the accommodation of thermal gradients in the
matrix. The spacing
of the fins or ribs may be generally equal to the width of the fins or ribs.
The fins may be in the form of substantially planar strips.
Optionally, discrete support fins may be provided at staggered spacing
throughout the matrix
of tubes. Such an arrangement can reduce mass while still providing benefits
in the
accommodation of thermal gradients.
Optionally, the tube module may be manufactured using an additive
manufacturing process.
The matrix may be formed integrally with the furcating and/or consolidating
tube sections.
The material of the module may be chosen depending on application. Materials
may include
stainless steel, such as 316L stainless steel, aluminium and titanium.
Optionally, at the downstream side of the tube matrix each tube consolidates
at a plurality of
nodes along its length. This successive consolidation of the tubes may be
identical or
substantially identical in form to the furcation or branching form of the
module and those
features described in relation to the furcation may be equally applied to the
consolation of the
sub-tubes.
Optionally, the tube matrix is located between and fluidly connected to a
furcating tube section
or manifold and a consolidating tube section or manifold. The furcating tube
section and the
consolidating tube section may be positioned on opposite sides side of the
shell with the matrix
aligned generally centrally in the shell.
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The consolidating tube section or manifold may be coupled to a web of tubes.
The web of
tubes may couple to each of the tube modules. The web of tubes may have a
common fluid
inlet/outlet.
Optionally, each tube in the web of tubes may include a section arranged in a
spiral, for
example a helix. This spiral arrangement of tubes may provide accommodation
for thermal
expansion or contraction of the tube module or modules within the heat
exchanger, but allowing
axial movement of the tube.
The spiral may be arranged with its rotational axis aligned with the central
longitudinal axis of
the heat exchanger shell.
Optionally, the furcation tube section of a module is substantially identical
in form to the
consolidating section.
Optionally, the shell is rounded.
Optionally, the shell is generally spherical. This allows for a maximum
internal volume but with
minimum external surface area and thus material. Such a form can also provide
a structure
which is resistant to internal pressure.
The shell may be formed as a duct, for example, a cylindrical duct. The matrix
and flow tube
may be provided in said duct. An inlet and outlet to the tube arrangement may
extend non-
axially to the flow tube, for example, substantially perpendicular. The inlet
and outlet may
extend through a wall of the shell, for example, the duct, in which the matrix
and tube
arrangement is provided.
Optionally, the shell comprises a fluid inlet.
Optionally, the inlet of the shell is in fluid communication with the inner
volume of the shell via
a diffuser. The diffuser may be formed as a flow channel confirming generally
to the inner
surface of the shell.
Optionally, the shell comprises a thermal liner. Such an arrangement can allow
the shell to be
maintained at a uniform temperature and thus reduce thermal stresses.
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Optionally, the thermal liner substantially conforms to an inner surface of
the shell and spaced
apart therefrom to form a flow path therebetween. This can allow a small bleed
flow of the fluid
entering the shell via the inlet.
According to a further aspect of the disclosure, there is provided a method of
operating a shell
and tube type heat exchanger according to the first aspect and any optional
feature thereon,
including the steps of:
supplying a heatant or coolant to the shell to fill said shell;
supplying a fluid to the tube arrangement in said shell.
The heatant or coolant may be supplied via a diffuser.
A small bleed flow of the heatant or coolant may be supplied to the thermal
liner. This can
ensure the upstream and downstream sides of the shell are isothermal.
According to a third aspect of the disclosure, there is provided an engine or
vehicle comprising
a heat exchanger according to first aspect or any optional feature thereof.
Brief Summary of the Drawings
The present disclosure will now be described by way of example with reference
to the following
drawings, in which:
Figure 1 is a cross sectional view of an example heat exchanger showing a
shell and a tube
arrangement.
Figure 2 is a partial cutaway perspective view of the heat exchanger of Figure
1 showing a
plurality of tube modules.
Figure 3 is a cross-sectional view of the heat exchanger of Figure 1 showing a
diffuser.
Figure 4 is a diagram showing progressive layers of a branching manifold.
Figure 5A is a perspective view of a branching manifold.
Figure 5B is a two-dimensional view of a branching manifold.
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Figure 6 is a diagram showing an indication of a plurality of flat node planes
of a furcating tube
arrangement.
Figure 7 is a diagram showing an indication of a plurality of curved node
planes of a furcating
tube arrangement.
Figure 8 shows a first cross-section view of a node.
Figure 9 shows a series of second cross-section views of a node.
Figure 10A shows a cutaway perspective view of a tube matrix with a continuous
fin
arrangement.
Figure 10B shows a cutaway perspective view of a tube matrix with a spaced fin
arrangement.
Figure 10C shows a cutaway perspective view of a tube matrix with a staggered
spaced fin
arrangement.
Figure 11A shows a cutaway view of a tube matrix at a constant temperature.
Figure 11B shows a cutaway view of a tube matrix experiencing a thermal
gradient.
Figure 12A shows a cross-section view of the heat exchanger highlighting the
location of a
module mounting.
Figure 12B shows a zoomed-in cross-section view of the heat exchanger showing
a module
mounting.
Figure 13 shows a perspective view of a branching manifold and a matrix
section surrounded
by a matrix shell.
Figure 14 is a cross sectional view of an example heat exchanger showing a
shell and a tube
arrangement.
Figure 15 shows an example of an alternative matrix form.
Figure 16 shows an example of a teardrop tube cross-section.
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Figure 17 shows an example of baffle supports present within the shell of the
heat exchanger.
Description
Figure 1 shows a heat exchanger generally at 1. The heat exchanger comprises a
shell 2,
which in the example shown has a generally spherical form. The shell 2
comprises a shell inlet
3. The shell 2 also comprises a shell outlet 4. Both the shell inlet 3 and the
shell outlet 4 have
a generally circular cross-section. The shell comprises two hemispheres, an
inlet hemisphere
27 into which fluid is introduced into the volume of the shell 2 and an outlet
hemisphere 28.
The shell inlet 3 is located on the surface of the inlet hemisphere 27. The
shell outlet 4 is
located on the surface of the outlet hemisphere 28. The location of the shell
outlet 4 is directly
opposite the shell inlet 3.
Situated within the shell 2 is a tube arrangement 5. In the shown example, the
tube
arrangement 5 extends entirely through the shell 2. The tube arrangement 5
comprises a flow
tube 6. The flow tube 6 comprises a flow tube inlet web 29 and a flow tube
outlet web 30. The
flow tube inlet web 29 is located in the outlet hemisphere 28 of the shell 2,
and the flow tube
outlet web 30 is located in the inlet hemisphere 28 of the shell 2. The tube
arrangement 5
further comprises a tube inlet 7 into which heatant or coolant may be supplied
depending upon
application. The tube inlet 7 is located in the centre of shell outlet 4 and
has a smaller diameter
than the shell outlet 4. The tube inlet 7 is also fluidly connected to the
flow tube inlet web 29.
The flow tube 6 has a tube outlet 8. The tube outlet 8 is located in the
centre of shell inlet 3
and has a smaller diameter than the shell inlet 3. The tube outlet 8 is
fluidly connected to the
flow tube outlet web 30. Both the tube inlet 7 and the tube outlet 8 have a
generally circular
cross-section.
Referring now to Figures 1 and 2, the section of the flow tube 6 between the
flow tube inlet
web 29 and the flow tube outlet web 30 comprises a plurality of tube modules
9. In the example,
there are eight tube modules 9. The tube modules 9 are substantially
identical. The plurality of
tube modules 9 are arranged angularly about a longitudinal axis of the shell
2. This angular
arrangement of tube modules 9 forms a ring-shaped or generally toroidal
structure. When the
plurality of tube modules 9 are placed together, they form a generally
circular outer profile. The
surface of this circular outer profile is generally equidistant at all points
from the longitudinal
axis of the shell 2. The tube modules 9 are located in a central plane of the
shell 2 such that
they are spaced substantially equidistant between the shell inlet 3 and the
shell outlet 4. The
ring-shaped structure of tube modules 9 has an aperture defined therethrough.
The aperture
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is generally circular in shape and is located on the longitudinal axis of the
shell. The aperture
is covered or sealed by a centreline plug 16 which blocks the aperture. This
prevents the
aperture from fluidly connecting the shell inlet 3 and the shell outlet 4. In
example, the aperture
is around one-ninth the cross-section of the shell 2 equidistant between the
shell inlet 3 and
the shell outlet 4. Another tube module (not shown) may be used in place of
the centreline plug
16.
Each tube module 9 comprises a furcating tube section or manifold 18. Each
tube module 9
further comprises a tube matrix 13. Each tube module 9 also comprises a
consolidating tube
section or manifold 19. The furcating manifold 18 is fluidly connected to the
tube matrix 13.
The tube matrix 13 is fluidly connected to consolidating manifold 19. Thus,
the furcating
manifold 18 is fluidly connected to the consolidating manifold 19. The tube
arrangement 5
furcates at a plurality of nodes into a plurality of sub-tubes in the
furcating manifold 18. The
tube arrangement 5 consolidates at a plurality of nodes into a single sub-tube
in the
consolidating manifold 19. In this way, the surface area of the tube
arrangement 5 increases
substantially in the furcating manifold 18. The surface area of the tube
arrangement 5 is
substantially constant in the tube matrix 13. In the consolidating manifold
19, the surface area
of the tube arrangement 5 decreases substantially.
The tube module 9 comprises a tube module inlet 10. The tube module inlet 10
is located in
the outlet hemisphere 28. Located at the tube module inlet 10 is a node at
which the flow tube
6 begins furcating. This node may be known as the principal furcating node.
The tube module
9 further comprises a tube module outlet 11. Located at the tube module outlet
ills a node at
which the sub-tubes of the consolidating manifold consolidate to one singular
tube. This node
may be known as the principal consolidating node. The tube module outlet 11 is
located in the
inlet hemisphere 27. The tube module inlet 10 and the tube module outlet 11
are fluidly
connected to one another. The tube module inlet 10 and tube module outlet 11
are aligned on
an axis generally parallel with the longitudinal axis of the shell 2. The tube
module inlet 10 is
fluidly connected to the furcating manifold 19 and the consolidating manifold
18.
A flow tube inlet web 29 comprises the length of the flow tube 6 from the tube
inlet 7 to the
tube module inlet 10. The flow tube inlet web 29 is initially a singular tube.
The flow tube inlet
web 29 then branches into a plurality of module feed tubes at branching point
12.
The flow tube inlet web 29 further comprises an expansion helix 31. The
expansion helix 31
allows for axial thermal expansion or contraction of the supported tube
modules 9. In other
words, the expansion helix 31 allows the heat exchanger to cope with thermal
expansion of
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tube modules 9 relative to the shell 2. Extreme temperature gradients across
the heat
exchanger 1 can occur during the start-up of an associated engine, and thus it
is important the
tube arrangement 5 can accommodate such extreme temperature gradients without
undue
thermal strain. In the inlet web, each of the module feed tubes is arranged in
a helical form.
Depending on the number of module feed tubes 6, a double helix, triple helix,
may be formed.
The expansion helix is located entirely within the outlet hemisphere 28. The
expansion helix
31 is also equidistant throughout its length from the longitudinal axis of the
shell. After the
expansion helix 31, the flow tube inlet web 29 connects to the tube module
inlet 10.
Referring to Figure 1, the tube module inlet 10 is fluidly connected to the
tube matrix 13. The
tube matrices 13 of each tube module 9 are all located in a central plane of
the shell 2 such
that they are spaced substantially equidistant between the shell inlet 3 and
the shell outlet 4.
The tube matrix 13 further comprises a tube matrix inlet 14. In this example,
the tube matrix
inlet 14 is located in the outlet hemisphere 28.
The furcating manifold 18 comprises the length of the tube from the tube
module inlet 10 to the
tube matrix inlet 14. In the furcating manifold 18, the flow tube of the tube
arrangement 5
furcates at a plurality of points along its length into an increasing number
of sub-tubes. Each
time the tube arrangement 5 splits or branches, the subsequent sub-tubes are
each of a
smaller diameter than the tube they have split from. In the furcating manifold
18, the angle at
which the sub-tubes furcate or branch is substantially regular. The tube
arrangement 5 furcates
repeatedly from the tube module inlet 10 until it reaches the tube matrix
inlet 14. The pattern
of furcating sub-tubes substantially repeats itself at decreasing scales of
size. The pattern can
be considered to be akin to a fractal pattern.
The tube matrix 13 also comprises a tube matrix outlet 15. The tube matrix
outlet is located in
the inlet hemisphere 27. The tube matrix inlet 14 and the tube matrix outlet
15 are fluidly
connected to one another. The tube matrix inlet 14 and tube matrix outlet 15
are aligned on an
axis generally parallel with the longitudinal axis of the shell.
The manifold sections 18 and 19 may be formed using an additive manufacturing
technique.
Materials can be chosen depending on application, such as 316L stainless
steel, aluminium
and titanium depending on application. This allows for the intricate form of
the tube
arrangement. The aspect ratio of the tubes, i.e. their internal diameter
compared with their
external diameter, is limited by the manufacturing tolerances available, in
particular the wall
thickness.
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If additive manufacturing is used, the manifold sections and the tube matrix
13 may be formed
as one continuous piece, or produced separately and joined, for example by
brazing the
manifold sections to the matrix tubes.
The tube matrix 13 comprises a plurality of generally parallel tubes. The
tubes of the tube
matrix are the smallest-diameter tubes of the tube arrangement 5. The tube
matrix 13 is aligned
such that its tubes are generally parallel with the longitudinal axis of the
shell 2. Between the
tube matrix inlet 14 and the tube matrix outlet 15, the tubes of the tube
matrix do not furcate
nor consolidate. In the example, the matrix of a module comprises over a
hundred matrix tubes.
At the tube matrix outlet 15 there are a plurality of sub-tubes. The
consolidating manifold 19
comprises the length of tube arrangement 5 between the tube matrix outlet 15
to the tube
module outlet 11. The consolidating manifold 19 consolidates the tube
arrangement 5 at a
plurality of nodes. In this way, the tube arrangement 5 consolidates from a
plurality of sub-
tubes into a singular tube at each tube module outlet 11. Each time the tube
arrangement 5
consolidates, the subsequent sub-tubes are each of a larger diameter than the
tubes which
consolidated to form them. In the consolidating manifold 19, the angle the sub-
tubes
consolidate at is substantially regular. The angle the sub-tubes consolidate
at is substantially
the same angle the sub-tubes furcate at. The tube arrangement 5 consolidates
repeatedly from
the tube matrix outlet to the tube module outlet 11. The pattern of
consolidating sub-tubes
substantially repeats itself at increasing scales of size.
The flow tube outlet web 30 comprises the length of the flow tube 6 from the
tube module outlet
11 to the tube outlet 8. In the flow tube outlet web 30, the flow tube 6 is
initially a plurality of
module exit tubes. Each tube module outlet 11 corresponds to one module exit
tube. In other
words, each module exit tube corresponds to one tube module outlet 11. The
flow tube outlet
web 30 then joins the plurality of module exit tubes into one single tube at a
joining point 17.
In the example, this single tube does not branch nor join with any other tube
before it reaches
the tube outlet 8.
Referring to Figures 1, 2 and 3, the shell 2 further comprises a diffuser 20.
The diffuser 20 is
located in the inlet hemisphere 27. The diffuser 20 creates a passage between
the inner
surface of the shell 2 and the diffuser skin 21. This diffuser is for
efficiently decelerating the
inlet flow with low pressure loss. The diffuser skin 21 substantially follows
the curvature of the
shell 2. The diffuser skin 21 covers the shell inlet 3. The diffuser passage
79 created between
the inner surface of the shell 2 and the diffuser skin 21 is of a generally
constant width for the
majority of its length. The diffuser passage 79 created between the inner
surface of the shell
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2 and the diffuser skin 21 is thicker at the shell inlet 3. This is due to the
shell 2 at the shell
inlet 3 extending out in the longitudinal direction. The diffuser passage 79
between the inner
surface of the shell 2 and the diffuser skin 21 is divided by diffuser fins
22. These diffuser fins
split the diffuser passage 79 into diverging channels. These diverging
channels have a
rectangular cross-section. In the example, the inlet-outlet area ratio of the
channels is 1:4.
The diffuser 20 further comprises a diffuser outlet 80. The diffuser outlet 80
is located at the
end of the diffuser passage 79. The shell 2 further comprises an inlet plenum
23. The diffuser
20 is fluidly connected to the inlet plenum 23 via the diffuser outlet 80. The
shell 2 further
comprises an outlet plenum 24. The inlet plenum and outlet plenum are fluidly
connected. The
inlet plenum 23 and outlet plenum 24 are fluidly connected through the spaces
between the
tubes of the tube matrices 13. The outlet plenum 24 is fluidly connected to
the shell outlet 4.
Reference is now made to Figures 1 and 2. The shell 2 further comprises a
thermal liner 25.
The thermal liner 25 fluidly connects the inlet plenum 23 with the shell
outlet 4. The thermal
liner 25 maintains the temperature of the outer surface of the shell. The
thermal liner 25
ensures the two hemispheres 27 and 28 are reasonably isothermal, by the
provision of a small
bleed flow of the inlet fluid. This eliminates the high thermal stresses which
would result
otherwise. The majority of the thermal liner 25 is located in the outlet
hemisphere 28 of the
shell 2. The thermal liner 25 creates a passage between the inner surface of
the shell 2 and
the thermal liner skin 26. The thermal liner skin 26 substantially follows the
curvature of the
shell 2. A first section of the passage extends into the inlet hemisphere 27.
A second section
of the passage is between the outer surface of the structure of tube modules 9
and the inner
surface of the shell 2. The second section of the thermal liner skin 26 is
directly adjacent the
generally circular outer profile of the tube modules 9. A third section of the
thermal liner skin
26 is fluidly connected to the shell outlet 4.
In one typical operation of the heat exchanger 1, the tube arrangement 5 is
filled with a heatant
fluid. The heatant fluid enters the tube arrangement 5 through the tube inlet
7, and exits the
tube arrangement 5 through the tube outlet 8. This heatant fluid can for
example be helium.
This heatant fluid enters the tube arrangement 5 at around 600K. The shell 2
is filled with a
coolant fluid. This coolant fluid enters the shell through the shell inlet,
and exits the shell
through the shell outlet. The coolant fluid may for example be liquid
hydrogen. The coolant
fluid enters the shell 2 at a temperature of around 50K and with a flow
velocity of around Mach
2 for example. The heatant fluid is at a higher pressure than the coolant
fluid. The heatant fluid
flows in an opposite direction to the shell fluid providing a counter flow
arrangement. This
increases the rate of heat exchange compared with if the fluid flows were in
the same direction.
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Typically, the heatant fluid flows slowest through the tube matrix to increase
the amount of
heat exchange which can occur.
The furcating and consolidating manifolds 18 and 19 can be considered as forms
of branching
manifolds. Reference is now made to Figures 4, 5A, and 5B. Figure 4 displays
progressive
cross-sectional layers of a branching manifold 32, which can be seen in
Figures 5A and 5B. In
its simplest form, the branching manifold 32 takes the inlet or outlet tube
and branches it into
four smaller tubes, then each of these branches is divided into four, and so
on in progressive
layers. The branching is continued until the tube diameter of a tube matrix 44
is reached.
Specifically, the first layer 33 of the branching manifold 32 shows a single
inlet or outlet tube.
The second layer 34 of the branching manifold 32 shows how this single tube,
shown by the
dotted line, is split into four sub-tubes. These four sub-tubes are of equal
diameter. The third
layer 35 of the branching manifold 32 divides each of these four sub-tubes
into four sub-tubes
of their own, generating sixteen sub-tubes in total. These sixteen sub-tubes
are of equal
diameter. The fourth layer 36 then goes on to divide each of these sixteen sub-
tubes into four
sub-tubes of their own, generating 64 sub-tubes in total. The fifth layer 37
shows how each of
these sixty-four sub-tubes is divided into four, producing two-hundred-and-
fifty-six sub-tubes.
These two-hundred-and-fifty-six sub-tubes are each of equal diameter. The
sixth layer 38
shows how each of these two-hundred-and-fifty-six sub-tubes is further divided
into four,
producing one-thousand-and-twenty-four sub-tubes. These one-thousand-and-
twenty-four
sub-tubes are each of equal diameter. In each layer, the sub-tubes are spaced
regular
distances from one another and form a grid-like pattern. For example, in the
first layer 33, the
single inlet or outlet tube is drawn as a circle in the centre of a
hypothetical square. In the
second layer 34, the hypothetical square is split into four sub-squares, and
each of the sub-
tubes is drawn as a circle in the centre of each sub-square. The branching
pattern is repeated
for each of the subsequent layers 35-38. This means the diameter of the tubes
is constant in
each layer. A branching pattern repeated at different scales may be known as a
'fractal'. The
tube can be considered as furcating when viewing the layers in sequential
order from 33 to 38.
Alternatively, the tube can be considered as consolidating when viewing the
layers in reverse
order, from 38 to 33. The surface area of the tubes increases as tube furcates
in sequential
order from first layer 33 to sixth layer 38. Alternatively, the surface area
of the tube reduces as
the tube consolidates in reverse order from sixth layer 38 to first layer 33.
Reference is now made to Figure 6. The branching manifold 32 described above
produces
sets of 2D (x,y) coordinates for each layer of the branching manifold 32 on
which the branching
or furcating/consolidating nodes are located. These layers can be assumed to
be located on a
series of planes, 39-42. The first plane 39 can be considered as corresponding
to first layer 33
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of Figure 4. The second plane 40 can be considered as corresponding to second
layer 34 of
Figure 4. The third plane 41 can be considered as corresponding to third layer
35 of Figure 4.
The fourth plane 42 can be considered as corresponding to fourth layer 36. The
remaining
planes 43 can be considered as corresponding to the fifth layer 37 and beyond.
The planes
39-43 are flat. At the first plane 39, there is one singular inlet or outlet
tube. This tube furcates
into a plurality of sub-tubes, two of which can be seen in this two-
dimensional cross-section.
The branching continues at each plane, until the tube diameter of the tube
matrix 44 is reached.
As can be seen in Figure 6, the spacing of the nodes between each layer
becomes
progressively smaller. A divergence angle is the angle at which sub-tubes
furcate from a tube.
Divergence angle may also be known as turn angle or furcation angle. The
branching at each
plane occurs at a constant divergence angle.
Reference is now made to Figure 7. It is desirable to seek ways in which the
total volume and
tube length of the branching manifold 32 is reduced, reducing the total
manifold mass. This
can be achieved by minimising the distances between the nodes. The branching
manifold
section of a heat exchanger is typically heavier than the tube matrix with
increased surface
area it feeds. One way of reducing the distance between the nodes is to
manipulate the node
coordinates. The lateral distance between the nodes can be reduced with this
in mind, which
in turn reduces the axial distance of a node for a given divergence angle.
This can be achieved
by re-shaping the coordinate planes of the nodes into a series of curved
surfaces. These
curved surfaces may be curved in two or three dimensions. In other words,
reducing the
distances between each plane of nodes reduces the tube length of the branching
manifold 32.
Curving the planes of nodes reduces the lateral distance between each plane of
nodes.
Reducing the tube length between each node by curving the node planes reduces
total
manifold mass without requiring an increased divergence angle. Not all of the
node planes
must be curved for the heat exchanger to benefit from their curvature. In the
example shown
in Figure 7, first plane 35 remains flat. The second plane 46, the third plane
47, a fourth plane
48, and the remaining planes 49 are all curved. The second plane 46 is the
most curved, with
curvature decreasing in the third plane 47 through to the remaining planes 49.
This
configuration minimises the divergence angles at each node. This configuration
also shortens
the early branch stages, which otherwise require the most space to
accommodate. This
configuration reduces tube length by around one third when compared with a
equivalent flat-
plane node system with similar divergence angles. The curved-plane technique
may be
utilised to reduce tube length in both furcating manifolds and consolidating
manifolds.
Reference is now made to Figures 8 and 9. A node is a point or location at
which a tube
subdivides into further sub-tubes. Figure 8 shows a cross-section view of a
node 51. Figure 9
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shows several cross-sections of the node 51 as one tube splits into several
sub-tubes. The
nodes must be designed to withstand high internal pressures and to optimise
the internal flow
conditions which may occur when in use. The ability to manufacture the nodes
using an
additive manufacturing process is also important.
Pressure drop throughout a tube
arrangement is increased if its cross-sectional area is increased at nodes
compared with a
gradual increase in cross-sectional area between the nodes.
The node can be considered as being split into two phases, phase one and phase
two. Phase
one is a single straight pressure vessel before the branches split. Phase two
is a number of
pressure vessels that diverge from the original centreline of the node 51.
These two phases
ensure stress concentrations in the node's walls are limited. In phase 1, a
set of fins gradually
extend from the internal walls of the node 51 to meet in the centre. This
splits the flow into a
plurality of sectors. In this example, there are four sectors. During this
phase, the overall
diameter of the tube must increase to account for the cross-sectional area
taken up by the fins.
The section remains circular because all of the pressure loads are taken by
the walls of the
node 51. In phase 2, which occurs once the fins are merged at the centre, the
now separates
flow sectors now diverge. In geometric terms, the centroid of each channel
follows a circular
path away from the node's original centreline. This causes the cross-section
to adopt a lobed
shape as the outer radius shrinks. During this phase, pressure loads are
transferred to the fins.
This allows the node wall thickness to decrease. The node thus allows a
transition from a
single circular section tube to multiple circular section tubes.
The node cross-sections depicted in Figures 8 and 9 are scaled such that the
flow area remains
constant through the node. If the cross-section of a manifold increases from
its inlet to its matrix
section, this means that the total cross sectional increase between an inlet
and a beginning of
a matrix of a heat exchanger is accommodated in the straight tube sections
between the nodes.
Alternatively, the cross sectional area of the whole manifold can be scaled
linearly from its inlet
to the beginning of the matrix.
Sections 52-57 correspond to phase 1 of the node 51. The cross-section of
section 52 is
circular with a relatively thin node wall 64 around the perimeter of the
section. The cross-
section of section 53 has four fins 65 beginning to protrude from four corners
of the node wall
64. The nodes continue to grow from section 54 through section 55 and section
66, until they
join in the middle of the node at section 57. The joined fins 65 form an 'x'
shape in the centre
of the node 51, with four empty sections closed off from one another between
the joined fins
65 and the node walls 64. At 57, the joined fins 65 are of greater thickness
than the node wall
64. Sections 58-63 correspond to phase 2 of the node 51. The cross-section of
58 of the node
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51 features a thinner node wall 64 than previous cross-sections. The node wall
64 reduces
through cross-sections 59 and 60, before a central, circular cavity is formed
in the middle of
the "x" of joined fins 65 enclosing four cavities in cross-section 61. In
cross-section 62 the four
cavities are separated, forming four separate circular tubes. The node walls
of each of these
four circular tubes are thinner than the node wall 64 of initial section 52.
These four circular
tubes are located further away from each other in cross-section 63. Each of
the cross-sections
52-63 are symmetrical in two perpendicular axes.
Reference is now made to Figures 10A, 10B, and 10C. To facilitate
manufacturing and to assist
with regular tube spacing, a plurality of matrix tubes 68 are supported along
their length. In the
most basic implementation, this can be achieved by continuous fins 65 in all
regular grid
directions, shown in Figure 10A. With continuous fins, assuming a similar fin
thickness to the
tube wall thickness, there can be an increase in the overall matrix mass. The
pressure drop of
a fluid within the shell passing through the tube matrix from an inlet
hemisphere to an outlet
hemisphere can also increase due to the reduction in flow area.
The mass of the fins can be further reduced by replacing the continuous
support fins 65 with
discrete support fins spaced at regular intervals, known as spaced fins 65
seen in Figure 10B.
This reduces the volume and mass of material needed to be used for the
construction of the
support fins. In the example shown in Figure 10B, the spaced fins are of a
broadly rectangular
shape. Around 50% of each tube's length is used by the spaced fins.
This principle of weight reduction can be implemented further by staggering
the support fins to
support along a single grid direction at each point along each tube's length.
The staggered
support fins 67, shown in Figure 10C, cycle through the grid-directions
sequentially along each
tube's length. In the example shown, only one spaced fin is required when
staggered where
six were previously. The staggered support fins have the potential to reduce
the volume and
mass of the matrix section supports by five-sixths, or 83%, compared with
spaced fins 65.
The use of spaced fins 66 also allows for the easier accommodation of thermal
gradients. This
is particularly valuable with respect to non-linear starting transients. Being
able to
accommodate thermal expansion is of high importance with respect to a tube
matrix section to
prevent features from breaking up. Figure 11A shows a two-dimensional cross-
section of a
matrix section, with the plurality of matrix tubes 68 running substantially
parallel with one
another, connected by spaced fins 66. Figure 11B shows a two-dimensional cross-
section of
the same matrix section, but with a non-linear thermal gradient 69. The non-
linear thermal
gradient 69 shows an increase in temperature in the indicated direction. As
the temperature
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increases, the spaced fins 66 between the matrix tubes 68 grow in size. The
spaced fins 66
being allowed to expand in this way results in lower thermal stresses compared
with a
continuous fin arrangement 65. This causes the spacing between the tubes 68 to
be increased
by the support fins 66 of higher temperature.
The fins can be formed integrally with the matrix tubes 68 using an additive
manufacturing
technique.
Reference is now made to Figures 12A and 12B. The heat exchanger 1 is of the
same structure
as shown in Figure 1. Figure 12A shows a cross-section of the heat exchanger
1. Figure 12B
shows an enlarged view of the section encircled at 78 in Figure 12A. At a
corner of a tube
matrix 13 of one of the plurality of tube modules 9, the tube module 9 is
mounted on the inside
surface of the shell 2. Figure 12B shows the tubes 70 of the furcating
manifold 18. These
furcating manifold tubes 70 then enter the tube matrix 13. The furcating
manifold tubes 70
continue in the tube matrix 13 as a plurality of tube matrix tubes 71. The
tube matrix 13 features
a spaced fin configuration 72. The spaced fins 72 support the tube matrix
tubes 71. At the
outside edge of the tube module 9, the spaced fins join a module jacket 76.
This module jacket
allows the tube module 9 to be mounted to the shell 79 of the heat exchanger
1. The tube
module 9 is surrounded by the module jacket 76 for the full length of the tube
matrix 13. This
ensures the flow through the shell 2 is constrained to being through the tube
matrix 13. The
module jacket 76 features a module jacket flange 73. The module jacket flange
73 extends
perpendicularly from the tube matrix 13. The module jacket flange 73 has a
thicker wall than
the section of the module jacket 76 running the full length of the tube matrix
13. The angle
between the module jacket flange 73 and the module jacket 76 is ninety
degrees. A module
mount frame 75 extends from the inside surface of the shell 79. The module
jacket flange 73
is adjacent the module mount frame 75. There is a gap between the module
jacket flange 73
and the module mount frame 75. This gap is filled by a gasket 74 or a similar
seal. This seal is
gas-tight.
Reference is now made to Figure 13, which shows an alternative branching
manifold 132
having a similar branching structure to the furcating manifold 18 and
consolidating manifold 19
of the example shown in Figure 1 and in more detail in Figure 5A. In contrast
though, the
arrangement shown in Figure 13 is a heat exchanger 100 with a single module
and may have
low pressure applications.
A tube matrix 113 comprises a plurality of matrix tubes, which in the example
are generally
parallel arranged tubes. The matrix tubes located around the outer edge, or
periphery, of the
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tube matrix 113, are considered outer matrix tubes. The tube matrix 113 is
surrounded by a
matrix shell 181. The matrix shell 181 substantially conforms to the outer
edge or profile of the
tube matrix 113. This ensures a coolant fluid entering a first side of the
matrix shell 181 and
exiting a second side of the matrix shell 181 remains substantially within the
outer limits of the
tube matrix 113 when flowing from the first side to the second side of the
matrix shell 181,
between the tubes of the tube matrix 113. The matrix shell 181 is a relatively
thin layer of
material, and has a corrugated outer surface 182 with a plurality of
substantially parallel ridges
183 and grooves 184 running parallel to the tube matrix 113. The corrugated
outer surface 182
gives the matrix shell 181 added rigidity and strength over a matrix shell
example having a
smooth outer surface.
The matrix shell 181 is connected to the tube matrix 113 via a plurality of
webs or fins. The
matrix shell 181 may be connected to the outer matrix tubes via the plurality
of webs or fins.
The webs or fins may be in continuous, spaced, and/or staggered
configurations. The matrix
shell 181 may also be used in shell and tube heat exchanger configurations
limited to one tube
matrix. As with the matrix of Figure 1, the tube matrix 113 can be
manufactured using an
additive manufacturing technique. In addition, the shell 181 can be integrally
formed using the
additive manufacturing technique with the tube matrix 113.
Figure 14 shows a further heat exchanger arrangement generally at 201
comprising a single
matrix heat exchanger module with a generally cylindrical tube matrix 213. The
heat exchanger
comprises a shell, 202, which in the example shown has a generally cylindrical
form. The shell
202 comprises a shell inlet 203 into the volume of the shell 202, and a shell
outlet 204, located
at opposite ends of the shell 202. The shell inlet 203 and the shell outlet
204 are aligned
substantially axially at the opposite ends of the shell 202.
The arrangement of Figure 14 has a similar branching configuration as the
arrangement of
Figure 1. The tube arrangement 205 comprises a tube inlet 207, a tube module
inlet 210, a
furcating manifold 218, a tube matrix 213, a consolidating manifold 219, a
tube module outlet
211, and a tube outlet 208. The furcating manifold 218, the tube matrix 213,
and the
consolidating manifold 219 are similar in form to the furcating manifold 18,
the tube matrix 13,
and the consolidating manifold 19 of the example of Figure 1. The tube inlet
207 is fluidly
connected to the tube outlet 208. This example comprises only one tube matrix,
and therefore
there is no joining point or branching point as seen in the first example. As
such, the tube inlet
207 is directly connected to the tube module inlet 210, and the tube outlet
208 is directly
connected to the tube module outlet 211. The tube inlet 207 and tube outlet
208 are axially
aligned with respect to the tube matrix 213. The tube inlet 207 enters the
shell 202 through a
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side wall of said shell 202 which is a cylindrical with semi-elliptical ends.
The tube outlet 208
also exits the shell 202 through a side wall of said shell. The tube inlet 207
and tube outlet 208
may enter and exit respectively the shell 202 through the same side wall of
said shell. The tube
matrix 213 is mounted to the shell 202. This mounting may be in a similar
manner to that
discussed in relation to the example of Figures 12A and 12B, and ensures the
flow through the
shell 202 is constrained to being through the tube matrix 213. Although not
shown, the heat
exchanger 201 may have all of the optional features discussed in this
application, for example
the expansion helix, node structure, and matrix support fins.
Reference is now made to Figure 15 which shows an example tube matrix of
cylindrical form.
This example shows a tube arrangement comprising three sections: a furcating
manifold 318,
a tube matrix 313, and a consolidating manifold 319. For clarity, the parts
are showed in
exploded form although it should be understood that the parts would be
adjoining to provide a
fluid coupling between the parts. The furcating manifold 318, tube matrix 313,
and
consolidating manifold 319 are similar in structure to the furcating manifold
18, tube matrix 13
and consolidating manifold 19 of the example of Figure 1. The tube matrix 313
further
comprises a tube matrix inlet 314 and tube matrix outlet 315. The tube matrix
313 may be
shaped such that it can conform to any defined space, as required, allowing it
to effectively fill
it. For example, the tube matrix 313 may be shaped to conform to a duct,
filling the duct profile.
The tube matrix 313, when viewed axially, may have a profile with curved
sides, a straight-
sided profile, or a profile which is a combination of straight and curved. In
this example, the
tube matrix 313 has a substantially cylindrical form. The furcating manifold
318 is in fluid
communication with the tube matrix 313. The consolidating manifold 319 is in
fluid
communication with the tube matrix 313. Thus, the furcating manifold 318 is in
fluid
communication with the consolidating manifold 319 via the matrix 313. The
furcating manifold
318 and consolidating manifold 319 are located on opposite sides of the tube
matrix 313. The
furcating manifold 318 comprises a plurality of sub-tubes. The furcating
manifold sub-tubes at
a minimum diameter are adjacent to and in fluid communication with the tube
matrix 313, and
form a matrix inlet face 385. The consolidating manifold 319 comprises a
plurality of sub-tubes.
The consolidating manifold sub-tubes at a minimum diameter are adjacent to and
in fluid
communication with the tube matrix 313, and form a matrix outlet face 386.
Reference is now made to Figure 16 which shows a tube cross-section with a
teardrop-shaped
perimeter. The teardrop shape has a first portion which is generally semi-
circular in form and
adjoins second portion which converges at a point. A teardrop shape typically
has one line of
symmetry upon which the point of the second portion lies.
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It is desirable to seek ways in which the pressure drop of a shell fluid
through a shell is reduced.
The branching manifolds of previous examples discussed, e.g. the furcating
manifolds 18 and
318 and the consolidating manifolds 19 and 319, comprise a plurality of tubes
and are typically
situated within a shell through which a shell fluid flows when the associated
heat exchanger is
in operation. The branching manifolds can generate drag which contributes to
pressure drop
of the shell fluid.
The tubes of the branching manifolds may have teardrop (or aerofoil) shaped
cross-sectional
perimeters. These tubes may be oriented with respect to the direction of the
shell fluid flow
within the volume of the shell such that drag is reduced, thereby reducing
pressure drop of the
shell fluid.
The concept of branching manifolds with teardrop-shaped tubes is not limited
to any shape of
shell.
Reference is now made to Figure 17, which shows the heat exchanger of Figure
1, but with a
plurality of baffle supports 88.
The plurality of baffle supports 88 extend into the volume of the shell and
may be attached to
the inner surface of the shell. The plurality of baffle supports 88 may be
located between or
attached to the branching manifolds (furcating manifold 18 and consolidating
manifold 19) of
each tube module 9. Although in the example, the baffle supports 88 are
generally linear strips,
the baffle supports 88 may have alternative shapes and forms to direct the
flow of the fluid
within the shell. Preferably, the plurality of baffle supports is shaped to
provide minimal
resistance to, and thus pressure drop of, the shell fluid flow. In this
example, each baffle
support 88 is substantially planar, and extends through the volume of the
shell until the central
aperture. The plurality of baffle supports 88 act as turning vanes for the
shell fluid.
Applications of the heat exchanger can include such as gas turbine engines and
hybrid rocket
type engines for example for aerospace uses.
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