JP2022520789A - Open cell foam metal heat exchanger - Google Patents

Abstract

A method of strengthening an open-cell foam metal heat exchanger using a fluid channel in which the structure distributes fluid and / or air throughout a continuous flow field is presented. Heat exchangers not only need to improve heat transfer characteristics to account for the required pressure drop, but also need to manufacture low cost solutions that can be mass-produced to meet high capacity throughput requirements for the aviation and space industries. Take into account.

Description

Embodiments of the present invention relate to the technical field of heat exchangers. More specifically, embodiments of the present invention are directed to low cost high performance heat exchangers that utilize open cell foam metal.

Open cell foam metal materials have many uses. These materials are designed and manufactured as heat exchanger solutions. The main applications of open cell foam metal heat exchanger applications are mainly within the aviation and space market divisions due to the high performance and lightweight requirements. Examples of products used as heat exchangers include satellite mirrors, aircraft computer heatsinks, commercial space expeditions, powered electronics cooling, and NASA's European Mars rover.

The open cell foam metal material generally has a structure that inherits the characteristics of the base alloy. These base alloys usually consist of low temperature alloys such as aluminum, copper, zinc, and other refractory metals. The advantage of the open cell foam structure is that the material provides a large surface area and a good strength-to-weight ratio. Unlike closed cell foam, gases, liquids, and other media can pass through the open pores of the material. This makes this material a phase change heat exchanger, an air / liquid cooling heat exchanger, an air to air heat exchanger, a liquid to liquid heat exchanger, a cooling plate, and a large surface area and permeability. It can be ideal for use as many other heat transfer applications utilizing the lattice structure.

The open cell foam material produced using a chemical vapor deposition (CVD) type process utilizes a host structure as the base for the additive material. These host structures are usually plastic or other materials that do not have the same composition as CVD additives. As a result, the foam produced by the CVD type is regarded as hollow, and the cross-sectional area is significantly reduced, so that the heat reduction characteristics are deteriorated. Disadvantages of this material reduce the performance of CVD type materials and exhibit limitations that open-cell foamed metals manufactured without a CVD type process do not encounter.

Other laminated modeling processes, including 3D printing, have similar drawbacks. Most 3D printing techniques create slip surfaces between layers. As a result, inconsistent temperature profiles during the layered build process produce such a degraded boundary layer effect. Due to these factors, the thermal performance deteriorates.

DUOCEL®, manufactured by ERG Aerospace since 1967, is an example of open cell foam metal manufactured without CVD or other such laminated molding processes. As described in Patent Document 1, production begins with a commercially available conventional foam, such as reticulated polyurethane, which acts as a foam and has the desired pattern in the final product. The conventional foam is embedded in a mold material such as gypsum and fixed 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 that correspond to the original configuration of the foam. Next, the molten metal is poured into the voids in the mold and cooled and hardened before the mold structure is washed away. The obtained foam metal has a network structure of an integrally formed solid metal mesentery and open cells having pores connecting adjacent bubbles. The solid metal mesentery structure provides improved properties compared to the midspace membrane formed from the laminated molding process. The open cell foam can also be compressed to further increase the surface area to volume ratio. This type of compression is not possible with CVD or laminated foam structures.

Open cell foam metal materials, including DUOCEL®, are manufactured in a variety of pore sizes. These sizes include 5 pores / inch (PPI), 10 PPI, 20 PPI, and 40 PPI. The advantage of having different pore sizes is that the material can be optimized for a variety of applications based on the pressure drop requirements and thermal performance of the heat exchanger. As an example, if high pressure drop is a major end-user requirement, a material of 40 PPI can be selected to provide a suitable pressure drop in view of the larger surface area. Conversely, with a 5 PPI material, the pressure drop is less, but with less heat transfer leading to lower performance. Therefore, the particular open cell foam metal material selected has considerations for pressure drop and heat transfer performance.

It is also possible to control the relative density of the open cell foam metal material, including DUOCEL®, for each of the above pore sizes. In other words, it is possible to add material to the individual interstitial membranes of open cell foam metal to create a relative density range. As an example, 5 PPI open cell foamed metal pieces can be varied at the individual interstitial level to increase the relative density range anywhere (relative to the weight of the solid alloy or the volume fraction of the metal) to a relative density of 3-20%. Can be achieved. Relative density, like PPI, can be changed as a design parameter to meet end-user requirements. With this design customization, open cell foam metal can also meet customer's precise pressure drop and thermal performance standards.

Some open cell foam metal materials such as DUOCEL® have been available for many years and can be customized to create high performance heat exchangers, such improved heat exchanger designs. And due to manufacturing costs, the product has become less desirable than the cheaper pin fin style heat exchange systems.

U.S. Pat. No. 3,616,814

Therefore, it is necessary to develop heat exchangers from open cell foam metal materials suitable for both high performance and affordable manufacturing such as DUOCEL®. In doing so, the use of such materials will be expanded to include jet engines, automobiles, and electronic cooling structures where high demand can be achieved with optimal manufacturability. In doing so, such materials can also directly compete with the 3D printed structures, CVD type, and pin fin type heat exchangers currently available in the aviation and space market segments where high demand throughput can be achieved.

In addition, the heat transfer performance, which is modular in design, needs to be improved, taking into account pressure drops for different energy level requirements. In other words, the heat exchanger design is extensible to accommodate a wide variety of different energy levels, both fluid and air. This includes the design of 1 kW energy removal systems, 2 kW energy removal systems, 3 kW energy removal systems, and more.

A further object of the present invention is to create a heat exchanger from an open cell foam metal material such as DUOCEL® that can be mass-produced using vacuum brazing, immersion brazing, or casting techniques. be. These standard techniques can be used for aluminum, copper, stainless steel, titanium, and other common and new heat transfer alloys.

Yet another object of the present invention is to provide a method of making a flow path that allows distribution of fluid over the entire flow field of an open cell foam material such as DUOCEL®. These channels are designed to address pressure drop considerations across length, while reliably improving material coverage while reducing pressure drop.

A further object of the present invention is to use a crossroad flow field, wherein each flow field comprises the use of an open cell foamed metal material such as DUOCEL®, which is specific to a given pressure drop and heat transfer requirements. That is.

A further object of the present invention is to improve the flow of turbulent and laminar flow fields across individual membranes, taking into account the viscosity and Reynolds number, taking into account the shape of the individual membrane structures.

The present invention is given only as a detailed description and illustration given below herein and will therefore be more fully understood from the accompanying drawings which are not limiting the invention.

It is a perspective view of the open-cell foamed metal countercurrent heat exchanger (1) for heat transfer in consideration of a pressure drop. It is a perspective view which shows the combination of the open cell foam metal panel (4) which combined the combination of the high temperature panel (2) and the low temperature panel (3) for making a countercurrent heat exchanger. It is a top view of the open-cell foamed metal countercurrent heat exchanger (1) which shows one embodiment of the input and output directions of fuel and oil. It is a top view of the individual high temperature panel (2) which shows the inlet (5) and outlet (6) of a hot fluid. It is a top view of the individual cold panel (3) showing the inlet (7) and the outlet (8) of the cold fluid. It is a perspective view of a single cell (15) of a relative density continuous one-piece insoluble reticulated open cell foam material before densification, showing the intermembrane (16) and pore (17) structures. Bubbles (15) from densified relative density continuous one-piece insoluble reticulated open-cell foam material showing intermembrane (16) and pore (17) structures and improved heat transfer in view of specific pressure drops. It is a perspective view of. It is a chart showing different shapes of individual mesentery considered for fluid flow considering laminar and turbulent options, with a size bar of 1 mm.

The present invention is now described in detail with reference to the accompanying drawings in which the same reference numerals are used to identify the same or similar elements throughout several figures. It should be noted that the drawings should be viewed in the orientation of the sign.

Further, although the embodiment shows the flow of a liquid, heat exchange between a high temperature gas and a low temperature gas is also assumed and is included in the present invention. Therefore, the invention should not be considered limited to liquids.

FIG. 1A shows an open-cell foamed metal countercurrent heat exchanger (1) for heat transfer in consideration of pressure drop. FIG. 1B shows a vertical cross section of the structure of the heat exchanger (1), where the heat exchanger (1) has at least one high temperature panel (2) and at least one enclosed in an impermeable container (10). It is composed of a combination (4) of two low temperature panels (3). The impermeable container (10) can be made of a suitable heat stable material. In some embodiments, the impermeable vessel (10) of the open cell foamed metal countercurrent heat exchanger (1) is A. B. S. (Acrylonitrile, butadiene, and styrene), acetate, acrylic (eg ACRYLITE®, LUCITE®, plexiglass, etc.), ceramics (eg MACOR®, alumina, etc.), DELRIN®. , Epoxy / glass fiber, FEP, glass fiber laminate, impact resistant polystyrene (HIPS), KAPTON (registered trademark), KAPTREX (registered trademark), KYNAR (registered trademark), melamine, MELDIN (registered trademark) 7001, mica, neoprene , NOMEX (registered trademark), NORYL (trademark), nylon, PEEK (polyether ether ketone), PET (polyethylene terephthalate), P. et al. E. T. G. , Pphenol, PFA (Perfluoroalkoxy), Polycarbonate, Polyester, Polyester, Polysulfone, Polysulfone, Polyurethane, TEFLON®, Polyvinyl Chloride, REXOLITE® 1422 and 2200, RYTON®, Silicone / Glass It is made from heat-stabilizing materials with thermal insulation properties including, but not limited to, fiber, silicone rubber, TECHTRON®, ULTEM®, VESPEL® SP-1. In some embodiments, materials capable of efficient heat transfer, such as metals and metal alloys (eg, aluminum, copper, brass, steel, bronze, etc.) are preferred. However, in still other embodiments, metals such as stainless steel, iron-chromium alloys, lead, and titanium are preferred.

In the illustrated embodiment, the cold liquid, such as fuel, enters the channel (12) along the outer edge of the cold panel (3), which is separated from the hot panel (2) by the impermeable barrier (11), and then enters the channel (12). After passing through the open-cell foamed metal structure (9), they exit into a channel (13) located on the other side of the open-cell foamed metal structure (9). Simultaneously or in close proximity, hot liquids such as oil enter the channel (12) along the outer edge of the hot panel (2) and continue in opposite directions as a liquid flowing through the cooling panel (2). It passes through the bubble foam metal structure (9) and then exits into the channel (13) on the other side of the open cell foam metal structure (9).

FIG. 2A shows the flow of the liquid of one embodiment of the impermeable container of the open cell foamed metal countercurrent heat exchanger (1) when viewed from above. Here, the hot liquid (eg, oil) enters the open cell foamed metal countercurrent heat exchanger (1) at the outer corner of one end of the heat exchanger (1) and is on the opposite side of the heat exchanger (1). It comes out at the opposite end of the face. Similarly, the cold liquid (eg, fuel) enters the open cell foamed metal countercurrent heat exchanger (1) from the opposite corner of the same end as the hot liquid inlet and has the same end as the hot liquid outlet. It comes out from the opposite corner of the part. In another embodiment, the hot liquid inlet is located at the opposite corner of the same surface as the cold liquid outlet, and the hot liquid outlet is located at the opposite corner of the same face as the cold liquid inlet. Is placed in.

FIG. 2B shows the individual high temperature panels (2) and FIG. 2C shows the individual low temperature panels (3). Each of the high temperature panel (2) and the low temperature panel (3) has an impermeable substrate (12). Suitable materials for impermeable substrates include heat-stabilizing materials capable of efficient heat transfer, such as metals and metal alloys (eg, aluminum, copper, brass, steel, bronze, etc.). However, in some embodiments, metals such as stainless steel, iron-chromium alloys, lead, and titanium are preferred. The open cell metal foam material (9), such as DUOCEL®, is located on an impermeable substrate. Open cell metal foam materials are thermally stable, capable of efficient heat transfer, and are usually made of low temperature alloys including, but not limited to, aluminum, carbon, copper, platinum, silicon carbide, and zinc. .. The open-cell metal foam material is such that the fluid enters the panel through the inlet (5, 7), flows into the open-cell metal foam material (9), and exits the panel at the outlet (6, 8). It is placed on an impermeable substrate so that it must pass through the material (9). In some embodiments, the open-cell metal foam material (9) is an impermeable substrate (11) for the panel, an impermeable container (10), a foam metal foam material (9), and an impermeable material for the upper panel. Not such that there is an open space (12, 13) between the sex substrate (11) or the upper part of the impermeable container (10) accommodating the open cell foamed metal countercurrent heat exchanger (1). Placed in the center of the permeable substrate (see Figure 1B). In another embodiment, the fluid inlets (5, 7) enter directly into the open cell metal foam material (9).

FIG. 3 shows the structure of the bubbles (15) of the relative density continuous one-piece insoluble reticulated open-cell foam material (9) before densification. Usually, each bubble (10) has a three-dimensional 14-faceted polyhedron (tetracaideca hedron) structure. Each bubble (10) is defined by a mesentery (16) that creates pores (17). However, because the mesentery (16) is interconnected, each pore (17) is a component of at least two bubbles (15). Therefore, the resulting structure is identical in all three directions and is considered isotropic.
As a result, since all the pores (17) are interconnected, the fluid can freely enter and exit the open cell foam material (9).

FIG. 4 shows a single cell (15) of the relative density continuous one-piece insoluble reticulated open cell foam material (9) after densification. The relative density controls the cross-sectional shape of the mesentery (16), as shown in FIG. As can be seen in FIG. 5, the number of pores in the open cell metal foam material (9) remains constant, but the cross-sectional shape of the interstitial membrane (16) changes with relative density. When transitioning from low density (eg 3-5%) to high density (eg 11-13%), the membranous transitions from the shape of a triangular prism with sharp corners and finally through an intermediate triangular prism with rounded corners. It becomes almost a perfect cylindrical shape.

Currently, managing the pressure drop during heat design of heat exchangers is an important issue. Ideally, the calculated pressure drop is within the permissible pressure drop and is as close as possible. In the present invention, the fluid flow passes through a region of open cell foamed metal material such as DUOCEL®, which provides improved material coverage while reducing pressure drop. Due to the cross-field flow of hot and cold fluids, the number of pores and the shape of the interstitial membrane are accurately selected to improve performance, especially in situations where the turbulent flow field and the laminar flow field are different, especially considering the viscosity and Reynolds number. Can be made to. For high pressure systems, using a compressible open cell metal foam with 40 pores / inch (PPI) and a relative density of 7-8% gives improved results.

The open cell foam metal countercurrent heat exchanger (1) can be manufactured at low cost using standard vacuum brazing, immersion brazing, and / or casting techniques known in the art. .. The open cell foam metal countercurrent heat exchanger (1) of the present invention is suitable for use in jet engines, automobile engines, and electronic cooling structures.

Claims (14)

a. Impermeable housing container and
b. A combination of at least two adjacent panels, each panel
i. Impermeable substrate and
ii. A region of open-cell foamed metal containing bubbles composed of mesentery and pores,
iii. With the fluid inlet,
iv. With fluid outlet,
v. An open-cell foamed metal countercurrent heat exchanger, optionally comprising a combination of at least two adjacent panels, including at least one fluid channel. The open-cell foamed metal countercurrent heat exchanger according to claim 1, wherein each panel has the fluid inlet located at the same end as the adjacent panel. The open-cell foamed metal countercurrent heat exchanger according to claim 1, wherein each panel has the fluid outlet located at the same end as the adjacent panel. The open-cell foamed metal countercurrent heat exchanger according to claim 1, wherein each panel has the fluid inlet located at an end opposite to the adjacent panel. The open-cell foamed metal countercurrent heat exchanger according to claim 1, wherein each panel has the fluid outlet located at an end opposite to the adjacent panel. The open-cell foam metal countercurrent heat exchange according to any one of claims 1 to 5, wherein the open-cell foam metal region has a membranous shape for enhancing turbulent and laminar fluid flow. vessel. The open cell foam metal according to any one of claims 1 to 6, wherein the open cell foam metal has 40 pores / inch (PPI) and a relative density of 7 to 8% and is compressible. Flow heat exchanger. The open-cell foamed metal countercurrent heat exchanger according to any one of claims 1 to 7, wherein the open-cell foamed metal is DUOCEL (registered trademark). The method for manufacturing an open-cell foamed metal countercurrent heat exchanger according to any one of claims 1 to 8, comprising a step of combining fluid flow fields to produce improved heat transfer performance. a. The step of inserting the first liquid into the first panel of the combination,
b. A step of moving the first liquid through the region of the open-cell foamed metal and removing the first liquid from the first panel.
c. The step of inserting the second liquid into the second panel of the combination,
d. The step of moving the second liquid through the region of the open cell foam metal,
e. Including the step of removing the second liquid from the second panel.
One of claims 1 to 9, wherein the flow of the second liquid is in the opposite direction to the flow of the first liquid, and heat is exchanged between the first liquid and the second liquid. A method of using the open cell foam metal countercurrent heat exchanger according to item 1. The method of using the open cell foamed metal countercurrent heat exchanger of claim 10, wherein the combination comprises the first panel adjacent to the second panel. The method of using the open cell foamed metal countercurrent heat exchanger of claim 10 or 11, wherein the combination comprises a series of first and second panels. The method using the open cell foamed metal countercurrent heat exchanger according to any one of claims 10 to 12, wherein the first liquid is a low temperature liquid and the second liquid is a high temperature liquid. The method of using the open-cell foamed metal countercurrent heat exchanger according to any one of claims 10 to 13, wherein the first liquid is a fuel and the second liquid is an oil.

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