Corrugated Micro Tube Heat Exchanger

Abstract

A heat exchanger device having a plurality of substantially parallel tubes. Each tube has an outer diameter which is less than or equal to one millimeter and further includes a first end portion and a second end portion. A first manifold forms an inlet for the first fluid and further forms a plurality of first openings, whereby each of the first end portions of the parallel tubes is attached in a sealed manner to the first manifold so that each tube is in fluid communication with a respective one of the first openings. A second manifold spaced from and opposing the first manifold forms an outlet for the first fluid and further forms a plurality of second openings, whereby each of the second end portions of the parallel tubes is attached in a sealed manner to the second manifold so that each tube is in fluid communication with a respective one of the second openings. The plurality of substantially parallel tubes are laterally disposed relative to one another so that they form at least one corrugated pattern when viewed in an imaginary plane which intersects and is perpendicular to the longitudinal axes of the tubes.

Description

TECHNICAL FIELD

This invention relates to a heat exchanger device comprising corrugated micro tubes.

BACKGROUND

Heat exchangers transfer energy from one fluid to another. Heat exchangers are typically characterized by heat transfer rates and corresponding pressure drops of the fluid(s) across the heat exchanger. In many cases though, volume constraints are provided and, in these cases, heat exchanger performance may be characterized by heat transfer/flow area and corresponding pressure drops. For example, in the case of a liquid-gas heat exchanger, a typical design challenge is to minimize the face area associated with the gas side duct, while simultaneously meeting given specifications relating to allowable pressure drop of the gas across the heat exchanger, and, of course, heat transfer requirements.

Heat exchangers typically consist of cores and headers. The cores provide two sets of intertwining fluid passages that allow good thermal coupling between the two fluids without actual mixing of the fluids. Upon entering the volume occupied by the intertwining fluid passages, the fluid velocity typically increases because the hardware within the core that defines the two sets of fluid channels and promotes heat transfer between the two fluids necessarily occupies volume and restricts the area available for flow of both fluids.

Pressure drop across the core is a function of the drag associated with the shape of the “heat exchanger hardware” (i. e. tubes, fins, rectangular channels, etc.), the total distance of flow through this hardware, and the specific kinetic energy of the fluid (pV²). Good heat exchanger design is essentially a search for an optimum geometry which provides an excellent ratio of heat transfer/pressure drop within given envelope restraints. A need exists for heat exchangers with small flow areas (small duct size) that provide specified rates of heat transfer and specified low pressure drop.

SUMMARY OF THE INVENTION

The present invention provides an efficient, simple, and cost-effective device and/or methodology to provide high heat transfer/pressure drop ratios that are needed by heat exchanger end users.

The present invention addresses a means to simultaneously achieve high heat transfer/unit duct area and low pressure drop by the use of a corrugated or serpentine field of closely packed micro tubes. The width of the corrugated field is much less than the total length of the serpentine. The serpentine provides effectively a frontal area much larger than the duct area for one fluid to pass through the heat exchanger. Because the area is larger, the velocity of the fluid passing over the serpentine tube bank is reduced compared to cases involving the same flow rate, same duct size, but no corrugation. The lower fluid velocity combined with the short flow length (equal to the width of the serpentine) results in low pressure drop of the fluid passing over the outside of the tube bank.

As noted above, the present invention comprises tightly packed micro tubes. Micro channel heat exchangers, in general, provide high heat transfer rates/volume compared to heat exchangers with larger, more conventional scale, heat exchange passageways. Heat transfer/unit area is a function of the product hA, where h is the convection coefficient and A is the area available for heat transfer. Because both h and A increase as the characteristic passageway dimension (width or diameter) decreases, the product of hA/unit volume for micro channel heat exchangers is much greater than heat exchangers with larger scale. Because micro channel heat exchangers need less volume to achieve a given rate of heat exchange, it becomes geometrically feasible to “reshape” this reduced volume into a thin, serpentine shape that affords advantages with respect to reducing pressure drop. The advantages associated with the serpentine shape simply disappear as the characteristic dimensions of the heat exchanger hardware are increased.

It should further be noted that fields of tightly packed micro tubes offer another advantage with respect to corrugated or serpentine hardware that dictate a specific flow direction (such as normal to the local tangent along the serpentine). As the depth of each crease of a serpentine increases for a given crease width, the need for the flow direction through the heat exchanger hardware to be nonspecific becomes more important. Heat exchangers that use a tube bank, which allow flow in any direction, tend to offer substantial advantages in corrugated arrangements over flow passage geometries that do not.

One particular embodiment of the present invention comprises a plurality of substantially parallel tubes, each tube having an outer diameter which is less than or equal to one millimeter. Each parallel tube comprises a first end portion and a second end portion. The device further comprises a first manifold forming an inlet for the first fluid, the first manifold further forming a plurality of first openings, each of the first end portions of the parallel tubes being in sealing relation to the first manifold so that each tube is in fluid communication with a respective one of the first openings. In addition, the device comprises a second manifold spaced from and opposing the first manifold, the second manifold forming an outlet for the first fluid. The second manifold further forms a plurality of second openings, each of the second end portions of the parallel tubes being in sealing relation to the second manifold so that each tube is in fluid communication with a respective one of the second openings. The plurality of substantially parallel tubes are laterally disposed relative to one another so that they form at least one corrugated pattern when viewed in an imaginary plane which intersects and is perpendicular to the longitudinal axes of the tubes, the corrugated pattern having a thickness. The device is adapted so that the first fluid exchanges heat with the second fluid as the first fluid passes through the parallel tubes and the second fluid passes between the first and second manifolds and between but outside of the parallel tubes in a direction of flow which is generally perpendicular to the direction of flow of the first fluid through the tubes.

Another embodiment of the present invention is a method of exchanging heat between a first fluid and a second fluid. The method comprises providing a housing which defines a passageway through which the second fluid may flow and across which extends a plurality of substantially parallel tubes arranged in a corrugated pattern, when viewed along their longitudinal axes, and spaced apart from one another so that the plurality of tubes is substantially porous from any fluid flow direction nonparallel to the longitudinal axis of the tubes. The method further comprises. feeding the first fluid through the tubes and feeding the second fluid between and through the corrugated bank of parallel tubes, so that heat is transferred between the first fluid and the second fluid. In certain embodiments, the housing comprises a first manifold and second manifold, wherein the parallel tubes are sealingly attached to the first manifold and second manifold.

These and other features of this invention will be still further apparent from the ensuing description, drawings, and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a corrugated micro tube heat exchanger consistent with one embodiment of the present invention.

FIG. 2 is a perspective view of a plurality of corrugated micro tubes consistent with another embodiment of the present invention.

FIG. 2A is a perspective view of a prior art heat exchanger.

FIG. 3 is an exploded view of a corrugated micro tube heat exchanger in accordance with the embodiment of FIG. 1.

FIG. 4 is perspective view of a corrugated micro tube heat exchanger consistent with another embodiment of the present invention.

FIG. 5 is a top plan view of a plurality of corrugated micro tubes in accordance with the embodiment of FIG. 1.

FIG. 5A is a top plan view of a plurality of corrugated micro tubes in accordance with another embodiment of the present invention.

Like reference numbers or letters are used in the figures to reference like parts or components amongst the several figures.

FURTHER DETAILED DESCRIPTION OF THE INVENTION

The present invention enables the exchange of energy from one fluid to another in a heat exchanger without a significant reduction in pressure across the core while offering high heat transfer to weight ratio and reduced volume of the core. It does so by employing a device and/or methodology which is cost-effective and offers a relative ease of manufacture.

Referring now descriptively to the drawings, the attached figures illustrate one particular embodiment of the invention, in which a heat exchanger device 10 comprises corrugated micro tubes 12. As seen in FIG. 1, the illustrated embodiment has a plurality of substantially parallel tubes 12 in fluid communication with a first manifold 18 and a second manifold 22. Each parallel tube 12 has an outer diameter D (see FIG. 5) of less than or equal to one millimeter and further comprises a first end portion 14 and a second end portion 16.

First manifold 18 forms an inlet (not shown) for the first fluid A. First manifold 18 further forms a plurality of first openings 20 (See FIG. 3), whereby each of the first end portions 14 of the parallel tubes 12 is in sealing relation to the first manifold 18 so that each tube 12 is in fluid communication with a respective one of the first openings 20. The second manifold 22 is spaced from and opposes the first manifold 18 and forms an outlet (not shown) for the first fluid A. Second manifold 22 further forms a plurality of second openings 21, whereby each of the second end portions 16 of the parallel tubes 12 is in sealing relation to the second manifold 22 so that each tube 12 is in fluid communication with a respective one of the second openings.

The plurality of substantially parallel tubes 12 are laterally disposed relative to one another so that they form at least one corrugated pattern 26 when viewed in an imaginary plane which intersects and is perpendicular to the longitudinal axes of the tubes 12. The corrugated pattern 26 has a thickness T (See FIG. 2). The device 10 is adapted so that the first fluid A exchanges heat with a second fluid B as the first fluid A passes through the parallel tubes 12 and the second fluid B passes between the first manifold 18 and second manifold 22 and between but outside of the parallel tubes 12 in a direction of flow which is generally perpendicular to the direction of flow of the first fluid through the tubes 12.

Turning now to FIG. 2, in an alternate embodiment of the present invention, plurality of substantially parallel tubes 12 are illustrated in a corrugated pattern 26. The section of the corrugated heat exchanger is shown to fit within volume length L₁×width W by height H. The length L₂ of the corrugated heat exchanger is the length along the midplane of the bank of tubes having a value greater by virtue of its serpentine shape than length L₁. The thickness T of the tube bank may vary along the length L₂ of the plurality of substantially parallel tubes 12. Thickness T may vary based on the flow stream through the corrugated pattern 26 and may be varied to correct non-uniform or uneven flow. The corrugated pattern in any given embodiment of the present invention may vary to form any serpentine array. The thickness of the plurality of tubes also may vary at any point along the length of the serpentine array.

The corrugated heat exchanger can be compared to a similar tube-based solid block heat exchanger 34 where the entire volume L₁×H×W is occupied by a field of tubes 36 as shown in FIG. 2A. For the case where fluid flows through the two heat exchangers in a direction substantially perpendicular to the H-L₁ plane, the flow length across the tube bank for the case of the corrugated heat exchanger is T while the flow length through heat exchanger 34 shown in FIG. 2A is W. Also, the area available for normal flow through the tube banks is L₂×H for the corrugated heat exchanger and L₁×H for the solid block heat exchanger. The larger flow area associated with the corrugated heat exchanger and the shorter flow length across the tube bank associated with the corrugated heat exchanger make it possible to design heat exchangers with lower pressure drop for given heat transfer rates and given frontal areas.

In at least some embodiments of the invention, the corrugated pattern may be further defined by a grouping of segments. As shown in FIG. 1, the segment ends 32 are formed at the juncture of at least two segments 30. The angle Θ is the angle formed from the juncture of at least two segments 30 at the segment end 32. Segments ends may be porous and permeable to flow so as to reduce the restriction to flow typically found when angle Θ is small.

Looking now at FIG. 3, the embodiment as illustrated in FIG. 1 is shown from a different perspective. Previously described features will only be repeated as necessary. First manifold 18 is shown separated from the plurality of substantially parallel tubes 12. The plurality of first openings 20 formed from first manifold 18 is in a substantially similar corrugated pattern to the corrugated pattern 26 of the plurality of substantially parallel tubes 12. The corrugated pattern 26 of the first openings 20 is substantially similar to the corrugated pattern 26 of the plurality of substantially parallel tubes 12 so that the each of the first end portions 14 of the parallel tubes 12 may be in sealing relation to the first manifold 18 so that each tube 12 is in fluid communication with a respective one of the first openings 20. It should be appreciated that the corrugated pattern 26 of the second openings 21 is substantially similar to the corrugated pattern 26 of the plurality of substantially parallel tubes 12 so that the each of the second end portions 16 of the parallel tubes 12 may be in sealing relation to the second manifold 22 so that each tube 12 is in fluid communication with a respective one of the second openings.

As shown in FIG. 4, an alternate embodiment of the present invention further comprises two support plates 28 disposed between the first manifold 18 and second manifold 22. The plurality of parallel tubes 12 extend through the support plates 28 and are supported thereby. While two support plates 28 are illustrated, the number of support plates may vary. The number of support plates needed may depend upon, e.g., the diameter of the tubes, the number of tubes, the distance between the first and second manifold, and/or the fluids used in the energy transfer. The support plates may comprise support plate openings substantially similar in size to the first openings and the second openings. Spacing between each adjacent pair of first openings of the plurality of first openings may be substantially similar to the spacing between each adjacent pair of support plate openings, and spacing between each adjacent pair of second openings of the plurality of second openings may be substantially similar to the spacing between each adjacent pair of support plate openings.

Looking now at FIG. 5, an exploded top plan view of the embodiment of FIG. 1 is shown wherein the spacings S_L,S_T between each adjacent pair of parallel tubes 12 of the plurality of parallel tubes 12 are substantially uniform and each tube 12 of the plurality of tubes 12 has substantially the same outer diameter D. The spacing between the centers of each adjacent pair of parallel tubes 12 may be less than three times the outer diameter D of each parallel tube and the outer diameter D of each parallel tube may be less than or equal to one (1) mm. In an alternate embodiment of the invention illustrated in FIG. 5A, spacings S_L, S_T between each adjacent pair of parallel tubes of the plurality of parallel tubes may be non-uniform. Optionally, spacing S_L and/or spacing S_T may be uniform in a segment of the corrugated pattern of the plurality of parallel tubes but non-uniform with respect to another segment of the corrugated pattern. The spacing between adjacent pairs of parallel tubes may be uniform in at least one segment and non-uniform in at least one other segment along the length of the corrugated pattern. The spacing of the parallel tubes may be intentionally varied to control various fluid properties, including the flow rate of the second fluid between the first and second manifolds and between but outside of the parallel tubes in a direction of flow which is generally perpendicular to the direction of flow of the first fluid through the tubes. Spacing S_L may be greater than or less than spacing S_T. Spacing S_L and/or spacing S_T between each adjacent pair of parallel tubes of the plurality of parallel tubes may be less than or equal to one millimeter.

In at least one particular embodiment, as illustrated in FIG. 3, the spacing between each adjacent pair of first openings of the plurality of first openings is substantially equal to the spacing between each adjacent pair of second openings of the plurality of second openings.

Each of the first end portions of the parallel tubes is in sealing relation to the first manifold so that each tube is in fluid communication with a respective one of the first openings. Similarly, each of the second end portions of the parallel tubes is in sealing relation to the second manifold so that each tube is in fluid communication with a respective one of the second openings. The sealing relation between the tube end portions and their respective manifolds may be formed by welding, gluing, braising, or the like between the end portion of the tube and its respective opening in the first or second manifold, as the case may be.

As noted earlier, in some embodiments of the invention, one or more support plates may be disposed between the first and second manifold. Support plate openings may vary in size from the first and second openings. The plurality of substantially parallel tubes may be attached to the support plate openings by gluing, welding, braising, or the like. The plurality of substantially parallel tubes also may be inserted through the support plate openings without being fixably attached to the support plates. The methodology employed to attach the plurality of substantially parallel tubes to the support plates, if any, may vary depending on, for example, the number of support plates disposed between the first manifold and second manifold.

Manifolds and mid plates typically will be made of one or more lamina of thin sheets, for example either metal or polymer, each having the desired opening pattern. These lamina typically are made via lithographic etching, or stamping, and either process can produce the required lamina from a variety of metal alloys including steel, nickel alloy, aluminum, titanium, or from a polymer. Micro tubes typically may also be made from polymer or metal alloys. Such metal alloys may include, e.g., steel, nickel alloy, aluminum, or titanium. The manifold, midplates, and micro tubes of the heat exchanger device can be made from the same material or, for example, the device may comprise manifolds and midplates made out of one material and micro tubes made from a different material. The material used in making the heat exchanger may be selected based on performance standards or physical requirements. For example, the heat exchanger may be composed of stainless steel in high temperature operations or environments requiring high tensile strength. Aluminum may be chosen as a suitable material in order to decrease the weight of the heat exchanger. Such examples are nonlimiting and it should be apparent that one of ordinary skill in the art may choose the heat exchanger materials for a desired result based on the applicable factors.

Except as may be expressly otherwise indicated, the article “a” or “an” if and as used herein is not intended to limit, and should not be construed as limiting, the description or a claim to a single element to which the article refers. Rather, the article “a” or “an” if and as used herein is intended to cover one or more such elements, unless the text expressly indicates otherwise.

This invention is susceptible to considerable variation within the spirit and scope of the appended claims.

Claims

1. A device for transferring heat from a first fluid to a second fluid, the device comprising: a plurality of substantially parallel tubes, each tube having an outer diameter which is less than or equal to one millimeter, each parallel tube comprising a first end portion and a second end portion;a first manifold forming an inlet for the first fluid, the first manifold further forming a plurality of first openings, each of the first end portions of the parallel tubes being in sealing relation to the first manifold so that each tube is in fluid communication with a respective one of the first openings; anda second manifold spaced from and opposing the first manifold, the second manifold forming an outlet for the first fluid, the second manifold further forming a plurality of second openings, each of the second end portions of the parallel tubes being in sealing relation to the second manifold so that each tube is in fluid communication with a respective one of the second openings;

2. A device of claim 1 wherein the spacing between each adjacent pair of first openings of the plurality of first openings is substantially equal to the spacing between each adjacent pair of second openings of the plurality of second openings.

3. A device of claim 1 wherein the spacing between the centers of each adjacent pair of parallel tubes of the plurality of parallel tubes is less than three times an outer diameter of each parallel tube and the outer diameter of each parallel tube is less than or equal to one millimeter.

4. A device of claim 1 wherein the corrugated pattern has a length and the thickness of the corrugated pattern varies along the length.

5. A device of claim I wherein the spacings between each adjacent pair of parallel tubes of the plurality of parallel tubes are substantially uniform and each tube of the plurality of tubes has substantially the same outer diameter.

6. A device of claim 1 wherein the spacings between each adjacent pair of parallel tubes of the plurality of parallel tubes is not uniform.

7. A device of claim 1 further comprising one or more support plates disposed between the first and second manifold, the plurality of parallel tubes extending through the support plates and being supported thereby.

8. A method of exchanging heat between a first fluid and a second fluid, the method comprising providing a housing which defines a passageway through which the second fluid may flow and across which extends a plurality of substantially parallel tubes arranged in a corrugated pattern, when viewed along their longitudinal axes, and spaced apart from one another so that the plurality of tubes is substantially porous from any fluid flow direction nonparallel to the longitudinal axis of the tubes;feeding the first fluid through the tubes; andfeeding the second fluid between and through the corrugated pattern of parallel tubes, so that heat is transferred between the first fluid and the second fluid.

9. A method of claim 8, the method further comprising disposing the parallel tubes relative to one another so that the corrugated pattern has a thickness and a length, and the thickness varies along the length.