U.S. patent application number 17/430608 was filed with the patent office on 2022-04-14 for open cell foam metal heat exchanger.
The applicant listed for this patent is ERG Aerospace Corporation. Invention is credited to Mark BENSON, Mitchell HALL, Denver SCHAFFARZICK.
Application Number | 20220113097 17/430608 |
Document ID | / |
Family ID | |
Filed Date | 2022-04-14 |
United States Patent
Application |
20220113097 |
Kind Code |
A1 |
BENSON; Mark ; et
al. |
April 14, 2022 |
Open Cell Foam Metal Heat Exchanger
Abstract
A method of enhancing an open celled foam metal heat exchanger
is presented where the structure uses fluid channels that
distribute fluid and/or air across a continuous flow field. The
heat exchanger not only improves heat transfer properties given a
required pressure drop but also takes into consideration the need
to manufacture low cost solutions that may be mass produced to meet
high capacity throughput requirements for the air and space
industries.
Inventors: |
BENSON; Mark; (Carmel,
CA) ; HALL; Mitchell; (Reno, NV) ;
SCHAFFARZICK; Denver; (Pacifica, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ERG Aerospace Corporation |
Oakland |
CA |
US |
|
|
Appl. No.: |
17/430608 |
Filed: |
February 12, 2020 |
PCT Filed: |
February 12, 2020 |
PCT NO: |
PCT/US2020/018009 |
371 Date: |
August 12, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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62805168 |
Feb 13, 2019 |
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International
Class: |
F28F 13/00 20060101
F28F013/00; F28F 21/08 20060101 F28F021/08 |
Claims
1. An open celled foam metal counter flow heat exchanger comprising
a. an impermeable housing container; and b. a combination of at
least two adjacent panels, each panel comprising i. an impermeable
base; ii. a field of open celled foam metal comprising cells
comprised of ligaments and pores; iii. a fluid inlet; iv. a fluid
outlet; and v. optionally, at least one fluid channel.
2. The open celled foam metal counter flow heat exchanger according
to claim 1, wherein each panel has the fluid inlet located on the
same end as the adjacent panel.
3. The open celled foam metal counter flow heat exchanger according
to claim 1, wherein each panel has the fluid outlet located on the
same end as the adjacent panel.
4. The open celled foam metal counter flow heat exchanger according
to claim 1, wherein each panel has the fluid inlet located on the
opposite end as the adjacent panel.
5. The open celled foam metal counter flow heat exchanger according
to claim 1, wherein each panel has the fluid outlet located on the
opposite end as the adjacent panel.
6. The open celled foam metal counter flow heat exchanger according
to claim 1, wherein the field of open celled foam metal has
ligament geometry to enhance turbulent and laminar fluid flow.
7. The open celled foam metal counter flow heat exchanger according
to claim 1, wherein the open celled foam metal has 40 pores per
inch (PPI) and 7-8% relative density and is compressible.
8. The open celled foam metal counter flow heat exchanger according
to claim 1, wherein the open celled foam metal is DUOCEL.RTM..
9. A method of making the open celled foam metal counter flow heat
exchanger according to claim 1 comprising combining fluid flow
fields to create improved heat transfer performance.
10. A method of using the open celled foam metal counter flow heat
exchanger according to claim 1 comprising a. inserting a first
liquid into a first panel of the combination; b. moving the first
liquid through the field of open celled foam metal and removing the
first liquid from the first panel; c. inserting a second liquid
into a second panel of the combination; d. moving the second liquid
through the field of open celled foam metal; and e. removing the
second liquid from the second panel, wherein the flow of the second
liquid is in the opposite direction as the flow of the first liquid
and wherein heat has been exchanged between the first liquid and
the second liquid.
11. The method of using the open celled foam metal counter flow
heat exchanger according to claim 10, wherein the combination
comprises the first panel adjacent to the second panel.
12. The method of using the open celled foam metal counter flow
heat exchanger according to claim 10, wherein the combination
comprises a series of first and second panels.
13. The method of using the open celled foam metal counter flow
heat exchanger according to claim 10, wherein the first liquid is a
cool liquid and the second liquid is a hot liquid.
14. The method of using the open celled foam metal counter flow
heat exchanger according to claim 10, wherein the first liquid is
fuel and the second liquid is oil.
Description
TECHNICAL FIELD
[0001] Embodiments of the present invention relate to the technical
field of heat exchangers. More particularly, the embodiments of the
present invention are directed toward low cost--high performance
heat exchangers that utilize open celled foam metal.
BACKGROUND OF THE INVENTION
[0002] Open celled foam metal materials have many uses. These
materials have been engineered and manufactured as heat exchanger
solutions. The primary use for open celled foam metal heat
exchanger applications primarily resides within the air and space
market segments due to the need for high performance and low weight
requirements. Examples of where the product has been used as a heat
exchanger includes satellite mirrors, computer heat sinks on
aircraft, commercial space expeditions, powered electronics
cooling, and the European Mars Rover, NASA.
[0003] Open celled foam metal materials have structures that
generally take on the characteristics of a base alloy. These base
alloys typically consist of low temperature alloys such as
aluminum, copper, zinc, and other refractory metals. The advantages
of an open celled foam structure is that the material offers high
surface areas and outstanding strength to weight ratios. Unlike
closed cell foams, gases, liquids, and other mediums may pass
through the open pores of the material. This enables the material
to be ideal for use as a phase change heat exchanger, air/liquid
cooled heat exchanger, air to air heat exchanger, liquid to liquid
heat exchanger, cold plates, and a number of other heat transfer
applications that take advantage of the high surface area and the
permeable lattice structure.
[0004] Open celled foam materials that are manufactured using a
chemical vapor deposition (CVD) type processes utilize a host
structure as a base for additive materials. These host structures
are typically plastic or other materials that do not have the same
composition as the CVD additive. The result is that CVD type
manufactured foams are considered hollow and therefore result in
lower thermal reduction properties due to significantly lower
cross-sectional area. This material disadvantage reduces the
performance of CVD type materials and presents limitations that are
not encountered by open celled foam metals produced without CVD
type processes.
[0005] Other additive manufacturing processes, including 3-D
printing, have similar disadvantages. Most 3-D printing techniques
create slip planes in between layers. Consequently, inconsistent
temperature profiles during the additive manufacturing process
create such degraded boundary layer effects. These factors cause
lower thermal performance.
[0006] DUOCEL.RTM., produced by ERG Aerospace since 1967, is an
example of an open celled foam metal produced without CVD or other
such additive manufacturing processes. As described in U.S. Pat.
No. 3,616,814, production begins with a commercially available
conventional foam, such as reticulated polyurethane having the
desired pattern for the end product, that serves as a form. The
conventional foam is embedded in mold material, such as plaster of
paris, which sets to form a solid structure in and around the
plastic foam. The structure is then heated to volatilize and expel
the plastic foam, leaving voids in the mold corresponding to the
original configuration of the foam. Molten metal is then cast
through the voids in the mold and permitted to cool and set prior
to washing away the mold structure. The resulting foam metal is a
reticulated structure of integrally formed solid metal ligaments
and open cells with pores connecting adjacent cells. The solid
metal ligament structure provides improved properties compared to
the hollow ligaments formed from additive manufacturing processes.
Open celled foams can also be compressed further increasing the
surface area to volume ratio. This type of compression is not
possible with CVD or additive manufactured foam structures
[0007] Open celled foam metal materials, including DUOCEL.RTM., are
manufactured in a range of pore sizes. These sizes include 5 pores
per inch (PPI), 10 PPI, 20 PPI, and 40 PPI. The advantage of having
different pore sizes is that the material may be optimized for
different applications based on the pressure drop requirements of a
heat exchanger and the thermal performance. As an example, if high
pressure drop is a primary requirement of an end user, then the 40
PPI material can be chosen to provide adequate pressure drop given
the higher surface area. Conversely, a 5 PPI material may provide
less pressure drop but have less thermal heat transfer leading to
lower performance. Therefore, there is a pressure drop and heat
transfer performance consideration for the specific open celled
foam metal material chosen.
[0008] It is also possible to control the relative density of an
open celled foam metal material, including DUOCEL.RTM., for each of
the pore sizes referred to above. In other words, it is possible to
add material to the individual ligaments of the open celled foam
metal to create relative density ranges. As an example, a 5 PPI
piece of open celled foam metal may be modified at the individual
ligament level to achieve relative density ranges anywhere from 3
to 20 percent relative density (relative to the weight of the solid
alloy, or volume fraction of the metal). The relative density, much
like the PPI, may be modified as a design parameter to meet end
user requirements. This design customization further enables an
open celled foam metal to meet precise customer pressure drop and
thermal performance criteria.
[0009] While some open celled foam metal materials, such as
DUOCEL.RTM., have been available for a number of years, and allow
customization to create high performance heat exchangers, costs
associated with designing and manufacturing such improved heat
exchangers has made the product less desirable compared to cheaper
pin-fin style heat exchange systems.
BRIEF SUMMARY OF THE INVENTION
[0010] Therefore, there is a need to develop heat exchangers from
suitable open celled foam metal materials, such as DUOCEL.RTM.,
that are both high performance and affordable to manufacture. Doing
so expands the use of such materials to include jet engines, cars,
and electronic cooling structures where high demand may be achieved
through optimum manufacturability. Doing so also enables such
materials the ability to directly compete with 3-D printed
structures, CVD type, and pin fin type heat exchangers currently
available to the air and space market segments where high demand
throughput may be achieved.
[0011] Furthermore, there is a need for improved heat transfer
performance that is modular in design, given pressure drop for
different energy level requirements. In other words, the heat
exchanger design is scalable to meet a wide variety of different
energy levels for both fluids and air. This includes a design for 1
kilowatt energy removal systems, 2 kilowatt energy removal systems,
3 kilowatt energy removal systems, and more.
[0012] It is a further objective of the present invention to create
heat exchangers from open celled foam metal materials, such as
DUOCEL.RTM., that may be mass manufactured using vacuum brazing,
dip brazing, or casting techniques. These standard techniques may
be used for aluminum, copper, stainless steel, titanium, and other
common and emerging heat transfer alloys.
[0013] It is yet a further objective of the present invention to
provide methods of manufacturing flow channels that allow fluid
distribution across a flow field of an open celled foam material,
such as DUOCEL.RTM.. These flow channels ensure enhanced material
coverage while reducing pressure drop but are designed to address
pressure drop over length considerations.
[0014] It is a further objective of the present invention to use
cross channel flow fields where each flow field includes the use of
an open celled foam metal material, such as DUOCEL.RTM., specific
for a given pressure drop and heat transfer requirement.
[0015] It is a further objective of the present invention to
consider the geometry of the individual ligament structures to
improve flow across each individual ligament where turbulent and
laminar flow fields differ given viscosity and Reynolds
numbers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The present invention will become more fully understood from
the detailed description given herein below and the accompanying
drawings which are given by way of illustration only, and thus are
not limitative of the present invention.
[0017] FIG. 1A is a perspective view of an open celled foam metal
counter flow heat exchanger (1) for heat transfer given pressure
drop. FIG. 1B is a perspective view showing a combination of open
celled foam metal panels (4) where a combination of hot panels (2)
and cold panels (3) are combined to create a counter flow heat
exchanger.
[0018] FIG. 2A is a top view of the open celled foam metal counter
flow heat exchanger (1) showing one embodiment of the direction of
fuel and oil input and output. FIG. 2B is a top view of an
individual hot panel (2) where the hot fluid inlet (5) and outlet
(6) are shown.
[0019] FIG. 2C is a top view of an individual cold panel (3) where
the cold fluid inlet (7) and outlet (8) are shown.
[0020] FIG. 3 is a perspective view of a single cell (15) of a
relative density continuous one-piece insoluble reticulated open
celled foam material prior to densification showing the ligament
(16) and pore (17) structures.
[0021] FIG. 4 is a perspective view of a cell (15) from a relative
density continuous one-piece insoluble reticulated open celled foam
material after densification that has improved heat transfer given
a certain pressure drop showing the ligament (16) and pore (17)
structures.
[0022] FIG. 5 is a chart that shows the different geometries of
individual ligaments that are considered for fluid flow given
laminar and turbulent options; size bar is 1 mm.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0023] The present invention will now be described in detail with
reference to the accompanying drawings, wherein the same reference
numerals will be used to identify the same or similar elements
throughout the several views. It should be noted that the drawings
should be viewed in the direction of orientation of the reference
numerals.
[0024] In addition, while the embodiments illustrate liquid flow,
heat exchange between hot and cool gases is also envisioned and
encompassed by the invention. Therefore, the invention should not
be viewed as limited to liquids.
[0025] FIG. 1A illustrates an open celled foam metal counter flow
heat exchanger (1) for heat transfer given pressure drop. FIG. 1B
illustrates a vertical cross section of the structure of the heat
exchanger (1), which is comprised of a combination (4) of at least
one hot panel (2) and at least one cool panel (3) enclosed in an
impermeable container (10). The impermeable container (10) can be
made of appropriate heat stable substances. In some embodiments the
impermeable container (10) of the open celled foam metal counter
flow heat exchanger (1) is made of heat stable substances that have
insulating properties, including, but not limited to, A.B.S.
(acrylonitrile, butadiene, and styrene), acetates, acrylics (e.g.
ACRYLITE.RTM., LUCITE.RTM., plexiglass, etc.) ceramics (e.g.
MACOR.RTM., alumina, etc.), DELRIN.RTM., epoxy/fiberglass, FEP,
fiberglass laminates, high impact polystyrene (HIPS), KAPTON.RTM.,
KAPTREX.RTM., KYNAR.RTM., melamine, MELDIN.RTM. 7001, mica,
neoprene, NOMEX.RTM., NORYL.TM., nylon, PEEK (polyether ether
ketone), PET (polyethylene terephthalate), P.E.T.G., phenolics, PFA
(perfluoroalkoxy), polycarbonate, polyester, polyolefins,
polystyrene, polysulfone, polyurethane, TEFLON.RTM.,
polyvinylchloride, REXOLITE.RTM. 1422 &2200, RYTON.RTM.,
silicone/fiberglass, silicone rubber, TECHTRON.RTM., ULTEM.RTM.,
and VESPEL.RTM. SP-1. In some embodiments, materials capable of
efficient heat transfer such as metals and metal alloys (e.g.
aluminum, copper, brass, steel, bronze, etc.) are preferred. In yet
other embodiments, however, metals such as stainless steel, alloys
of iron and chromium, lead, and titanium are preferred.
[0026] In the embodiment shown, a cool liquid, such as fuel, enters
a channel (12) along the outer edge of the cool panel (3) that is
separated from the hot panel (2) by an impermeable barrier (11) and
then passes through an open celled foam metal structure (9) before
exiting into a channel (13) located on the other side of the open
celled foam metal structure (9). Simultaneously, or in temporal
proximity, a hot liquid, such as oil, enters a channel (12) along
the outer edge of the hot panel (2) and passes through an open
celled foam metal structure (9) in the opposite direction as the
liquid flowing through the cool panel (2) before exiting into a
channel (13) located on the other side of the open celled foam
metal structure (9).
[0027] FIG. 2 A illustrates the liquid flow of one embodiment of
the impermeable container of the open celled foam metal counter
flow heat exchanger (1) as seen from the top. Here, the hot liquid
(e.g. oil) enters the open celled foam metal counter flow heat
exchanger (1) at the outside corner of one end of the heat
exchanger (1) and exits at the opposite side and opposite end of
the heat exchanger (1). Similarly, the cool liquid (e.g. fuel),
enters the open celled foam metal counter flow heat exchanger (1)
from the opposite corner of the same end as the inlet for the hot
liquid and exits from the opposite corner of the same end as the
outlet for the hot liquid. In other embodiments, the inlet for the
hot liquid is located at the opposite corner on the same side as
the outlet for the cool liquid and the outlet for the hot liquid is
located at the opposite corner on the same side as the inlet for
the cool liquid.
[0028] FIG. 2B illustrates an individual hot panel (2) while FIG.
2C illustrates an individual cold panel (3). Each of the hot panels
(2) and cool panels (3) have an impermeable base (12). Suitable
materials for the impermeable base include heat stable substances
capable of efficient heat transfer such as metals and metal alloys
(e.g. aluminum, copper, brass, steel, bronze, etc.). In some
embodiments, however, metals such as stainless steel, alloys of
iron and chromium, lead, and titanium are preferred. An open celled
metal foam material (9), such as DUOCEL.RTM. is located on the
impermeable base. The open celled metal foam material is heat
stable and capable of efficient heat transfer and is typically made
of a low temperature alloy including, but not limited to, aluminum,
carbon, copper, platinum, silicon carbide, and zinc. The open
celled metal foam material is placed on the impermeable base such
that fluid enters the panel through an inlet (5, 7), flows into and
must pass through the open celled metal foam material (9) prior to
exiting the panel at an outlet (6, 8). In some embodiments, the
open celled metal foam material (9) is centered on the impermeable
base such that an open space (12, 13) exists between the
impermeable base (11) of the panel, the impermeable container (10),
the open celled metal foam material (9), and either the impermeable
base (11) of the panel above or the top of the impermeable
container (10) encasing the open celled foam metal counter flow
heat exchanger (1) (see FIG. 1B). In other embodiments, the fluid
inlet (5, 7) enters the open celled metal foam material (9)
directly.
[0029] FIG. 3 illustrates the structure of a cell (15) of a
relative density continuous one-piece insoluble reticulated open
cell foam material (9) prior to densification. Typically, each cell
(10) is a three-dimensional 14-faceted polyhedral
(tetrakaidekahedron) structure. Each cell (10) is defined by
ligaments (16) which create a pore (17); however, because the
ligaments (16) are interconnected, each pore (17) is a component of
at least two cells (15). The resulting structure is there for
identical in all three directions and is considered isotropic.
Consequently, because all of the pores (17) are interconnected,
fluids are able to pass freely into and out of the open celled foam
material (9).
[0030] FIG. 4 illustrates a single cell (15) of a relative density
continuous one-piece insoluble reticulated open cell foam material
(9) after densification. The relative density controls the
cross-sectional shape of the ligaments (16), as shown in FIG. 5. As
can be seen in FIG. 5, while the number of pores of an open celled
metal foam material (9) remains constant, the cross-sectional shape
of the ligaments (16) varies depending upon the relative density.
Moving from a low density (e.g. 3-5%) to a higher density (e.g.
11-13%), the ligaments transition from a triangular prism shape
with sharp corners through an intermediate triangular prism with
rounded corners and culminating in almost a perfect cylindrical
shape.
[0031] Currently, managing pressure drop during thermal design of
heat exchangers is a significant problem. Ideally, the calculated
pressure drop is within and as close as possible to the allowable
pressure drop. In the invention, the fluid flow passes through a
field of open celled foam metal material, such as DUOCEL.RTM.,
which provides enhanced material coverage while reducing pressure
drop. The cross field flow of hot and cool fluids allows precise
selection of pore numbers and ligament geometry for enhanced
performance, especially in situations where turbulent and laminar
flow fields differ given viscosity and Reynolds numbers. For high
pressure systems, improved results are obtained with open celled
metal foam having 40 pores per inch (PPI) and 7-8% relative density
and is compressible
[0032] The open celled foam metal counter flow heat exchanger (1)
can be manufactured at low cost using standard vacuum brazing, dip
brazing and/or casting techniques known in the art. The open celled
foam metal counter flow heat exchanger (1) of the invention is
suitable for use in jet engines, car engines, and electronic
cooling structures.
* * * * *