Note: Descriptions are shown in the official language in which they were submitted.
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A method of producing multiple channels for use in a device
for exchange of solutes or heat between fluid flows
FIELD OF INVENTION
The present invention relates generally to exchange of
solutes or heat between fluid flows, and more specifically
to a method of producing multiple channels for use in a
device for exchange of solutes or heat between fluid flows.
The invention further relates to a device for exchange of
solutes between at least two fluid flows.
BACKGROUND
Today there are many different applications where diffusion
is used to enrich a fluid flow with solutes from another
fluid flow, or to remove unwanted solutes or substances from
the fluid flow. One example is in HVAC (Heating, Ventilation
and Air Conditioning) where water vapour can be removed from
a gas stream in order to reduce power consumption by reduced
condensation in a cooler unit or to recycle energy from
exhaust air in e.g. a building. Another example is reverse
osmosis for desalinating water.
Different methods are used when it comes to separating water
vapour from a fluid; such as rotating wheels with moisture
capture or plate heat exchangers with semi permeable
membranes. In gas drying technologies bundles of tubing,
made of materials like NafionTM, are used.
However, these different methods of removing water vapour
from fluids do have certain disadvantages; rotating
exchangers are provided with moving parts which cause extra
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costs for maintenance. Further, rotating exchangers
increases the risk of contamination between airstreams.
Plate exchangers show low efficiency in regards to enthalpy
and Nafiohn tubing is expensive.
Producers of these technologies all try to find the most
cost efficient way of producing these effects, and therefore
different methods are developed. In conventional plate-based
heat- or moisture exchangers, the layers of the exchanger
are often made up with spacers or distancing members or a
support structure, onto which a membrane is laid. Such
structures are common but fail to achieve high cost
efficiencies due to their need for spacers, which can become
expensive depending on the material used.
Further, the spacers also raise the total weight of the
exchanger. Due to the weight, more supports are needed when
mounted, and increased weight also increases risks due to
handling during maintenance. Also the costs for
transportation increase with heavy weight.
In some gas drying technologies a multitude of small tubes
are used in order to provide a high moisture exchange
surface area coupled with good flow characteristics through
the bundles of tubing, while the gas flow characteristics on
the outside of the bundle are largely neglected, often
without adequate spacing for flow between the tubes.
Tubes in a bundle are usually used in conjunction with
another fluid stream that goes in counter- or cross-current
to the tubes, but on the outside, between the many tubes.
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When using individually made tubes of very small diameter,
production cost will become high since small tubes are
technically complicated to manufacture and refine into a
product, and, as a consequence, the final product will
become expensive. Another drawback is when tubes are packed
into a bundle; in current contemporary products, no
satisfactory space allowance is provided for the flow
characteristics in between the tubes.
SUMMARY OF THE INVENTION
The present invention relates to a method of producing
multiple channels for use in a device for exchange of
solutes between at least two fluid flows overcoming the
disadvantages and drawbacks mentioned above. A first and a
second sheet are comprised in the device. The method
comprises the steps of providing at least one of the first
and second sheets with at least one profiled surface, and
joining the first and second sheets together. Thereby,
channels are formed by the shape of the profiled surface.
The present invention provides a method enabling production
of multiple thin channels to a very low production cost.
Further, the method provides for an alternative way of
manufacturing multiple channels of infinite variation using
favourable flow patterns.
According to another embodiment, the method may comprise the
further step of providing each of the first and second
sheets with at least one profiled surface and joining the
first and second sheets together with the profiled surfaces
facing against each other, whereby channels are formed by
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the shape of the profiled surfaces.
According to another embodiment, wherein a plurality of
sheets are comprised, the method may comprise the further
step of joining the plurality of sheets together, whereby
channels in multiple layers are formed by the shape of the
profiled surfaces.
According to another aspect of the present invention, a
device for exchange of solutes between at least a first and
a second fluid flow is provided. The device comprises at
least a first and a second sheet wherein the first sheet
being provided with at least one profiled surface. The first
and second sheets are joined together whereby channels are
formed by the shape of the profiled surface.
The device according to the present invention is
particularly useful for exchanging a substance from a first
fluid flow to a second fluid flow, in order to remove or
separate the substance from the first fluid flow.
According to another embodiment, each of the first and
second sheet may be provided with profiled surfaces, and
the first and second sheet are joined together with the
profiled surfaces facing against each other.
According to another embodiment, the sheets may be provided
with profiled surfaces mirrored to each other.
According to another embodiment, the cross section of the
channels may vary along the length of the device.
According to another embodiment, the number of the channels
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along the length of the device may vary.
According to another embodiment, the device may further
comprise a plurality of sheets stacked in multiple layers.
According to another embodiment, the sheet material may have
5 a high solubility to water.
According to another embodiment, the sheet material may have
a pore size between 0.1-50 nanometers.
According to another embodiment, the sheet material may have
a pore size of 50-500 nanometers.
According to another embodiment at least one of the sheets
may be hydrophobic.
According to another embodiment at least one of the sheets
may be hydrophilic.
According to yet another embodiment at least one of the
sheets may be a metal.
In one embodiment, each of said first and second sheet may
have a first end portion and a second end portion, said
first and second end portions having sloping intermediate
surfaces between each channel, said sloping intermediate
surfaces being inclined in a direction towards a middle
portion of the respective sheet.
In one embodiment, each sheet may have a first lateral end
portion and a second lateral end portion opposite said first
lateral end portion, said first lateral end portion having a
greater lateral extension than said second lateral end
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portion.
The high exchange surface area provided by a multitude of
channels, coupled with good flow characteristics between
layers provides an ideal situation for diffusion transfer or
heat transfer between fluid streams.
The present design allows for any distance between layers
according to needs. The flow characteristics between layers
can also be adjusted by increasing the distance between
layers or staggering the layer layout.
A further advantage is, for example in the case that a fluid
is to be dried, that a larger stream of air may be flowing
outside the channels, or between layers in the embodiments
provided with more than one layer, whereby the fluid inside
the channels is more effectively dried. By suitable design
of the distance between layers, the amount of flow between
layers may be optimised for the application.
The present invention provides a device allowing for a
counter current design with a tight configuration and no
need for separate spacer material to allow flow across the
sheets. Further, the device provides exceptionally good flow
characteristics between layers due to its design with
multiple channels and stacked layer design with adjustable
distance between layers. Also, the integrated channels
provide low maintenance and low risk of tear since there is
no wear due to vibrations of the sheets against support
structures.
Yet a further advantage is that the device is cheap to
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manufacture with automatic separation of individual channels
and with good and independently adjustable outside flow
characteristics. Further, the present invention provides a
device for solute exchange that eliminates the need for
additional support structures between sheets while at the same
time providing a means for counter current flow, which
improves the efficiency significantly compared to conventional
technology.
In one particular embodiment there is provided a method of
producing multiple channels for use in a device for exchange
of solutes or heat between at least a first and a second fluid
flow, wherein the device comprises at least a first and a
second sheet, the method comprising: providing each of said
first and second sheets with at least one profiled surface,
joining said first and second sheets together with the at
least one profiled surface facing each other, whereby channels
having a constant height along their entire longitudinal
extension are formed by the shape of the at least one profiled
surface, wherein each of said first and second sheet has a
first end portion and a second end portion, said first and
second end portions having sloping intermediate surfaces
between each channel, wherein the sloping intermediate
surfaces are level with an outer top surface of the channels
at a first end of the first end portion and a second end of
the second end portion, wherein each sloping intermediate
surface is inclined relative to the longitudinal extension of
the channels until reaching a planar longitudinally extending
portion between the first end portion and the second end
portion, and wherein the sloping intermediate surfaces have a
greatest lateral extent at the first and second ends and
I
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narrow to a lesser lateral extent at the planar longitudinally
extending portion between the first and second end portions.
Further preferred embodiments are set out below.
BRIEF DESCRIPTION OF DRAWINGS
The invention is now described, by way of example, with
reference to the accompanying drawings, in which:
Fig. 1 shows a device for exchange of water vapour according
to prior art.
Fig. 2 shows a sheet with a profiled surface according to
one embodiment of the present invention.
Fig. 3 shows a sheet with a profiled surface according to
another embodiment.
Fig. 4 shows two sheets with profiled surfaces joined
together according to one embodiment of the present
invention.
Fig. 5 shows a plurality of sheets with profiled surfaces
joined together.
Figs. 6 and 7 show sheets with alternative profiled
surfaces.
I
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Fig. 8 shows a plurality of sheets joined together in
staggered layers.
Fig. 9 shows two sheets with profiled surfaces joined
together according to yet another embodiment of the present
invention.
Fig. 10 shows one sheet with profiled surfaces joined
together with a sheet with a smooth surface according to one
embodiment of the present invention.
Fig. 11 shows a sheet with yet another alternative profiled
surface.
Fig. 12a shows a perspective view of an example of a sheet
for use in an exchange device according to the invention.
Fig. 12b shows a perspective view of a stack of sheets as
shown in Fig. 12a, forming part of an exchange device
according to the invention.
Fig. 13 shows a front view of the sheet in Fig. 12a.
Fig. 14 shows a perspective view of a stack of sheets
forming part of an exchanging device according to another
example of the invention.
Fig. 15 shows a cross-sectional view of a stack of sheets,
illustrating the flow of a fluid in a direction
perpendicular to the longitudinal extension of the sheets.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Fig 1 shows a device for exchange of water vapour according
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to prior art. In conventional technology, a corrugated
material or a flow distribution member is used between plain
sheets of permeable material to define channels and flow
direction and to provide a uniform spacer for separating
layers. In some examples the sides of the sheets are turned
down to provide spacers. This design is always limited to a
cross flow configuration.
Fig 2 shows a sheet 3 with a profiled surface 5 according to
the present invention. To create the shape of the profiled
surface 5 several different methods may be used in
manufacturing. For example, the sheet can be a corrugated
plate. As a further example, a sheet of a material can be
heated to a degree where it is deformable and then cooled
after shaping it over a mould/body and thereby letting the
shape set. Once deformed permanently, the shape will stay.
Another way is to let a lot of extremely thin threads fall
randomly over a mould/body e.g. through electro spinning, to
produce a shape that, once it sets, keeps its shape even
when deformed. Yet another way to create the shape of the
profiled surface 5 is to cut channels with favourable flow
patterns into one side, or both sides, of a sheet of a solid
or porous material. The material of the sheets 3, 4 may be
semi permeable, or permeable to certain substances or
solutes. The material of the sheets may be either porous or
solid or both.
The methods described above are especially suitable when the
dimension of the channels 1 Is small. With those methods
small channels with a cross section of only a few
millimetres may be produced easily and cost efficiently.
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The shape of the profiled surface, and thus the cross
section of the channels formed by the surfaces, may vary,
depending on desired flow characteristics. The cross section
of the channels may for example be circular, hexagonal,
5 square or triangular. A first and a second fluid may flow
counter-current to each other, inside and outside of the
channel 1 respectively.
The fluids in the channels may be a gas or a liquid.
Fig 3 shows another sheet 3 with a profiled surface 5
10 according to one embodiment of the invention. The sheet is
further provided with openings to facilitate flow between
layers 7 when a plurality of sheets are joined together in
multiple layers 7.
Fig. 4 show two sheets 3, 4 with profiled surfaces 5 joined
together according to the present Invention. By providing a
sheet of a base material with a profiled surface 5, for
example as shown in Fig. 1, and by joining two such sheets
3, 4 of opposite and preferably mirrored configured profiled
surfaces 5 to each other, a multiple of small channels 1 can
be formed by an easily automated process. Joining the sheets
3, 4 together may be achieved by for example welding, gluing
or fusing, or any other suitable adhesive process that would
join the two profiled plates hermetically together. The
sheets 3, 4 are provided with a profiled surface 5 whereby
channels 1 with circular cross-sections are achieved. The
channels 1 may have any other suitable shape, for example
oval, hexagon or square.
Fig. 5 shows a plurality of sheets 3, 4 joined together.
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When stacked, as shown in the figure, the sheets 3, 4 form
multiple layers 7. Such a configuration results in a low
pressure drop when fluids flow from one side to the other,
thereby securing and maintaining the flow characteristics of
the channels and an unobstructed fluid flow between the
layers 7, outside the channels 1.
Fig. 6 and 7 show sheets 3 with alternative profiled
surfaces 5.
Fig. 8 shows a plurality of sheets 3, 4 joined together in
multiple layers 7. The layers 7 are displaced in relation to
each other whereby a device with plurality of layers 7 with
a staggered configuration is provided. A staggered formation
reduces distance between layers 7 and thus increases the
total surface area per volume unit of the configuration, and
the unit can thus be made more compact while maintaining the
same surface area.
Fig. 9 shows two sheets with profiled surfaces joined
together.
Fig. 10 shows one sheet 3 with profiled surfaces 5 joined
together with a sheet with a smooth surface. Thereby,
channels 1 showing a half-circular cross-section is
provided.
Fig. 11 shows a sheet with an alternative profiled surface
5. The sheet is also provided with a plurality of openings 6
to facilitate flow between layers 7 when a plurality of
sheets 3, 4 are joined together in multiple layers 7.
In order to separate the entry of flows, openings can be cut
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between the channels. This provides entry channels
perpendicular to the main direction of the channels, thereby
separating the flow outside the channels, or, in the case of
multiple layers, between layers, from the entry point of the
flow inside the channels. If the configuration of multiple
layers 7 is staggered, the same method may be used for a
diagonal channel, perpendicular to the channels to feed the
flow between layers 7.
The profiled surfaces 5 may be formed by any suitable
method, for example by heating the sheets, deforming them
whereby the surfaces are profiled, and then cooling them
whereby the shape of the profiled surfaces stay in their
deformed shape. Another example is letting a plurality of
thin threads fall randomly over a body with a profiled
surface, whereby a sheet with a profiled surface 5 is
created that, once set, will keep its shape. Further
alternative may be cutting channels into one side, or both
sides, of a first and a second sheet of a solid or porous
material. Yet further the profiled surface may be provided
by applying a pattern of a plastic or other suitable
material on sheets.
Further, openings 6 can be cut between the channels 1 in
order to provide an inlet that distributes flow from a
direction perpendicular to the channels 1, in between layers
7. This provides unobstructed flow perpendicular to the main
direction of the channels, thereby separating the flow
between the channels from the entry point of the flow inside
the channels. If the configuration of layers 7 is staggered,
the same method may be used for a diagonal channel,
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perpendicular to the channels to feed the flow between
layers 7.
In order to distribute flows evenly and easily between
layers 7, openings 6 can be cut either between the ends of
the channels (primarily for flow distribution), or in
intervals along the whole length of the channels, providing
a simple means for pressure equalization and easy flow path.
In order to provide a bundle of channels for cross flow or
counter current flow, uniformly spaced openings can be cut
between channels to provide for an unobstructed flow between
channels between channels from two directions (top to bottom
or side to side), both perpendicular to the main direction
of flow inside the channels.
Any of the above described embodiments may be utilized in
either moisture exchange applications, for exchange of
solutes or alternatively, in heat exchange applications. The
functionality of an embodiment depends on the material in
which the sheets are manufactured.
For heat exchange applications, a material with high heat
conductivity may typically be used. Such materials include
metals such as aluminium and stainless steel, or
thermoplastics such as polypropylene or polyethylene
terephthalate (PET). For applications involving exchange of
solutes, typically a permeable or semi-permeable material as
described hereabove may be utilized.
Fig. 12 a shows a perspective of a sheet 10 according to an
example of the present invention. The sheet 10 may be
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manufactured in any way as already described above. The
sheet may be used in either moisture exchange applications,
for exchange of solutes or alternatively, in heat exchange
applications. As mentioned above, the particular application
depends on the material of the sheet 10.
The sheet 10 has a first end 10-1 and a second end 10-2
opposite the first end 10-1. The sheet 10 has a plurality of
channels 12 presenting a profiled surface of the sheet 10.
The sheet 10 further has a first lateral portion 14-1 and a
second lateral portion 14-1 opposite the first lateral
portion 14-1. The first lateral portion 14-1 and the second
lateral portion 14-2 form outer boundaries of the sheet 10
in the longitudinal direction thereof.
Sheets 10 may pairwise be joined together with corresponding
channels 12 facing each other, wherein corresponding
channels 12 thereby form closed channels or tubes.
Sheets 10 may pairwise be assembled to form a stacked sheet
assembly 16, as shown in Fig. 12b and schematically shown in
Fig. 15. The stacked sheet assembly forms multiple channels
12 through which a first fluid may flow. In layers between
each pair of sheets 10, a second fluid may flow. The second
fluid is typically provided into the stacked sheet assembly
16 from a side defined by the first lateral portion 14-1.
The second fluid flow typically exits the stacked sheet
assembly 16 from a side defined by the second lateral
portion 14-2. While the second fluid is flowing through the
stacked sheet assembly 16, it may flow both parallel with
the channels 12, and perpendicular to the channels 12.
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In case the stacked sheet assembly is arranged such that it
allows for fluid flow of the second fluid parallel with the
channels 12, the flow direction is typically in a direction
opposite the flow direction of the first fluid which flows
5 through the channels 12. However, the fluid flow of the
first and the second fluids may also be in the same
direction in some applications.
The first lateral portion 14-1 and the second lateral
portion 14-2 present substantially planar surfaces.
10 The first lateral portion 14-1 may have a greater lateral
extension di from an outmost channel 12 from which it
extends, compared to a lateral extension d2 of the second
lateral portion 14-1 with respect to the extension of the
second lateral portion 14-2 from an outmost channel 12 from
15 which it extends, as shown in Fig. 15.
By providing a sheet 10 with a configuration where the first
lateral portion 14-1 has a greater lateral extension di from
an outmost channel than the lateral extension d2 of the
second lateral portion 14-2, pairs of joined sheets 10 may
be stacked such that the channels 12 for each pair of sheet
is arranged in an alternating manner. This way, every second
layer of sheet pairs have their channels in mutual planes.
Thereby, fluid flow may pass between each pair of sheet 10
in a direction from the first lateral portion 14-1 to the
second lateral portion 14-2.
The sheet 10 shown in Fig. 12a has a first end portion 11-1
at its first end 10-1. The sheet 10 has a second end portion
11-2 at its second end 10-2. The first end portion 11-1 and
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second end portion 11-2 have a plurality of sloping
intermediate surfaces 13. A sloping intermediate surface 13
is provided between each adjacent channel 12. The sloping
intermediate surfaces 13 are substantially level with an
outer top surface 15 of the channels 12 at the first end 10-
1 and the second end 10-2.
The sloping intermediate surfaces 13 have a downwardly
inclination from the first end 10-1 and the second end 10-2
in a direction towards a middle portion 17 of the sheet 10.
Between the first end portion 11-1 and the second end
portion 11-2, the intermediate surfaces between the channels
12 are substantially parallel with the channels 12.
The sloping intermediate surfaces 13 provide open ends for
each pair of joined sheet 10 as no channels are formed at
the first end 10-1 and second end 10-2. Thereby, the first
end portion 11-1 and the second end portion 11-2 act as flow
distribution members, evenly distributing incoming fluid
flow 18 into the plurality of joined channels 12 at the
first end 10-1, and collecting the flow from each channel 12
at the second end 10-2. This process is schematically
illustrated in Fig. 12a.
Further, the sloping intermediate surfaces which are
substantially in level with the top surfaces 15 of channels
12 at the first end 10-1 and the second end 10-2 provide a
distancing element so that stacked pairs of sheets 10 may be
properly distanced. Thereby fluid flow between each layer of
joined pair of sheets 10 may be obtained. The distancing
will appear only at the first end portion 11-1 and the
second end portion 11-2. Fluid flow may hence be provided
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unobstructed in the area between the first end portion 11-1
and the second end portion 11-2. However, it is envisaged
that other separating means may be provided along the axial
extension of the sheet, if the sheet are very long, in order
to separate pairs of sheet from each other.
Fig. 13 shows a front view of the sheet 10. A flat surface
19 allows the stacking of multiple pairs of sheet 10 while
distancing each pair properly from its two adjacent pairs of
sheet 10.Fig. 14 shows a stacked sheet assembly 16', which
is a variation of the stacked sheet assembly 16. Generally,
the stacked sheet assembly 16' has similar design as that of
stacked sheet assembly 16. However, sheet 10' utilizes other
techniques than the above-described sloping intermediate
surfaces for distancing each pair of joined sheet 10'. In
particular, each pair of joined sheets 10' may be stacked
with other joined pair of sheets 10' by e.g. providing a
string of hot-melt adhesive transversally across an outer
surface 15' of a first and a second end of each sheet 10'.
Another alternative is to provide distancing members at each
end.
Fig. 15 illustrates how fluid flows transversally across a
part of the stacked sheet assembly 16. A fluid flow F
between only two pairs of joined sheet 10 is shown for
illustrative purposes.
As the fluid flow F enters the stacked sheet assembly 16,
laminar flow becomes turbulent. This effect is partly due to
the downwardly protruding channel portions 12-1 which direct
the fluid flow F towards the upwardly protruding channel
portions 12-2. The fluid flow will thereby have a more even
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velocity gradient, resulting in turbulent flow and a low
pressure fall across the stacked sheet assembly 16. Hence,
the flow speed may substantially be maintained throughout
the stacked sheet assembly 16. Further, due to the nature of
resulting turbulent flow, the reduced boundary layer
resistance result in more efficient exchange with the first
fluid flowing in the channel 12. Thereby very efficient
cooling or heating may be provided.
It is to be noted that words such as "upwardly" and
"downwardly" only reflect the geometrical layout of the
stacked sheet assembly in Fig. 15 and is not to be construed
as limiting said features in this manner. In reality, the
directions in which the channels protrude depend on the
orientation of the stacked sheet assembly.
The fluids flowing through the stacked sheet assembly 16 may
be any gas, or any liquid suitable for applications
exchanging solutes and/or heat. The sheet may be constructed
from any suitable material, depending on the application,
e.g. for exchanging solutes, or for cooling or heating
purposes.
The invention has mainly been described above with reference
to a few embodiments. However, as is readily appreciated by
a person skilled in the art, other embodiments than the ones
disclosed above are equally possible within the scope of the
invention, as defined by the appended patent claims. For
instance, a sheet may have a first end and a second end
which are not opposite each other; the sheet may have other
shapes than being rectangular. For instance, the sheet may
have a rhomboid shape, or being formed as a 'U'.
