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.

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®.

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

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®, LUCITE®, plexiglass, etc.) ceramics (e.g. MACOR®, alumina, etc.), DELRIN®, epoxy/fiberglass, FEP, fiberglass laminates, high impact polystyrene (HIPS), KAPTON®, KAPTREX®, KYNAR®, melamine, MELDIN® 7001, mica, neoprene, NOMEX®, NORYL™, nylon, PEEK (polyether ether ketone), PET (polyethylene terephthalate), P.E.T.G., phenolics, PFA (perfluoroalkoxy), polycarbonate, polyester, polyolefins, polystyrene, polysulfone, polyurethane, TEFLON®, polyvinylchloride, REXOLITE® 1422 &2200, RYTON®, silicone/fiberglass, silicone rubber, TECHTRON®, ULTEM®, and VESPEL® 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® 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®, 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.