WO2013163398A1

WO2013163398A1 - Additive manufactured lattice heat exchanger

Info

Publication number: WO2013163398A1
Application number: PCT/US2013/038175
Authority: WO
Inventors: Andrew SCHEVETS
Original assignee: Flowserve Management Company
Priority date: 2012-04-25
Filing date: 2013-04-25
Publication date: 2013-10-31

Abstract

A heat exchange tube, a heat exchanger using such a tube and a method of making such a tube. Additive manufacturing is used to form at least a portion of the tube. Augmented heat exchange features, such as external and internal lattice structure may be built up along with the remainder of the tube to form an enhanced heat exchange region with intermittent, repeating shapes. Such shapes maximize heat-dissipating surface area of the tube while reducing or eliminating large external dimensions associated with traditional tube manufacture.

Description

ADDITIVE MANUFACTURED LATTICE HEAT EXCHANGER

This application claims priority to US Provisional Application 61/638,281, filed April 25, 2012.

BACKGROUND OF THE INVENTION

[0001] This invention relates generally to a heat exchanger and heat exchanger components produced by additive manufacturing technology that results in the component having a lattice structure in the heat exchange region for improved heat transfer properties.

[0002] Heat exchange equipment is used to adjust the balance of heating and cooling between two or more components within a particular process or environment to provide enhanced creature comfort, improved operation of various mechanical processes, or the like. Examples of where such equipment is used include climate control systems in homes and vehicles, as well as those in commercial and industrial settings. One particular example involves mechanical systems (for example, pumps, motors or the like) that require cooling for moving parts, as well as those support parts used to facilitate relative movement between adjacently-moving parts; such support parts may include bearing housing oils and seal chamber fluids.

[0003] Regardless of the nature of the equipment being treated, one common way heat exchangers are employed is to convey the heat generated by temperature- sensitive components to an external heat sink for thermal dissipation. Numerous heat exchanger configurations are available, including double pipe arrangements, shell-and-tube arrangements, cross-flow arrangements or the like. In one conventional form, the fluids subject to the heat exchange operation are separated to avoid fluid mixing or direct contact. By way of example, the shell and tube heat exchanger - where a pressure vessel acts as a shell that contains a bundle of tubes inside it - is well-suited for this type of thermal communication between isolated fluids. In such construction, one fluid flows through the inside of the tubes while another flows within the shell and over the outside of the tubes in order to promote the transfer of heat between them. Regardless of the heat exchanger configuration, fluids that may be may be subjected to one or more heat exchange operations include liquids and gases the latter of which includes air or the like.

[0004] To maximize efficiency, it is preferable to have the surface area of the wall between the two fluids be as large as possible in order to maximize the conductive thermal contact between the relatively hot and cold fluids, while simultaneously avoiding undue flow resistance in order to promote the convective removal of excess heat. In one traditional form, tubes used in heat exchange systems fins or other externally-projecting surfaces to increase the surface area of the tube. It is additionally preferable to keep the overall size of the heat exchangers as compact as possible; however, this tends to significantly increase the cost of their manufacture, and can be at odds with the aforementioned desire to increase heat-transmissive surface areas. Complex joining schemes - such as machining, drilling, cutting, soldering, welding, brazing or related approaches - exacerbates the cost. Thus, while such known approaches may work well for producing such heat exchange components, inefficiencies arise. Moreover, there may be geometric shapes that are either impractical or impossible to make using conventional fabrication approaches.

[0005] Additive manufacturing (also known as solid free form fabrication (SFF) or free form fabrication (FFF), rapid prototyping, rapid manufacturing, layered manufacturing or three-dimensional printing) involves joining materials to make objects from 3D model (such as computer-aided design (CAD)) data. In a common form, the object is built up layer upon layer as part of a printing process. In this way, it differs from traditional (also known as subtractive) manufacturing where the process starts with a larger part that has excess material subsequently stripped away. With additive manufacturing, the fabrication machine reads in the model data and then lays down successive layers of liquid, powder or related material such that it builds up the object from a series of cross sections. The properties of the materials of the individual layers are such that they are joined or fused to create the final shape. One significant advantage to additive manufacturing is its ability to create almost any shape or geometric feature, while another is the potential for reduction in waste. The present inventor is unaware of the use of additive manufacturing as a way to produce heat exchange components in general, and with a lattice-like structure for the heat exchange region in particular.

BRIEF SUMMARY OF THE INVENTION

[0006] According to a first aspect of the present invention, a method of manufacturing a heat exchange tube is disclosed. The method includes defining data corresponding to a geometric configuration of the tube in a computer-readable form such that upon processing or related computer-based manipulation of the data, a forming device (for example, a 3D printer or the like) receives such processed data and builds up the tube through deposition of a precursor material. Depending on whether enhanced heat transfer attributes are needed in one or more portions of the tube's heat exchange region, the method preferably results in the formation of a lattice structure for a corresponding interior or exterior part of the tube. In the present context, the lattice (or lattice-like) nature of the tube structure is such that its respective interior or exterior dimensions that correspond to the fluid flowpath are defined by a network of intermittent structure within a partly or largely hollow flow volume. Such intermittent structure may be of any construction that will promote the thermal or related heat exchange performance needs of the heat exchange tube; one such form may be that of a regularly-repeating geometric nature on one or both of the tube interior and exterior surfaces. Even more particularly, the regularly-repeating geometric formations may be pin-like (or post-like) structure that extends normal to the direction of the fluid flow in the tube interior, as well as a mesh-like array of interconnected members formed along a diagonal pattern along the tube exterior surface. Other intermittent structure for either the interior or exterior surfaces may also be used that exhibit irregular-shaped or spaced features; all such variants are deemed to be within the scope of the present invention, so long as it satisfies the thermal performance criteria mentioned above and related structural attributes. By such structure, the present invention demonstrates multiple increases in heat dissipation relative to conventional finned tubes or related heat exchange devices. Such significant increases could allow air cooling rather than liquid cooling in certain applications, thereby greatly simplifying heat exchanger design. For example, it could be used for cooling of a seal injection fluid, regardless of whether such design is liquid-to-liquid or liquid-to-air. The use of the forming device in conjunction with the tube- specific data would allow a tube or related heat exchanger component to effectively be grown or built-up in one piece, thereby reducing or eliminating some or all of the complex assembly operations discussed with traditional manufacturing approaches discussed above.

[0007] According to another aspect of the invention, a method of making a heat exchange tube with lattice structure from a metal powder precursor material is disclosed. The method includes using a computer-based system to operate upon data that corresponds to a tube geometric configuration that defines a lattice structure that is part of the heat exchange region on one or both of a tube interior surface and exterior surface. The method also includes configuring a forming device to deposit the metal powder and receive instructions related to the data. Receipt of the forming instructions causes the forming device to use the metal powder to build up the tube with the lattice structure in the tube's heat exchange region. In a particular form, the lattice structure formed on the tube interior surface may be defined by numerous repeating pins, posts or similar projecting members that extend across a fluid flowpath formed on at least a portion of the interior surface. In a related way, the lattice structure formed on the tube exterior surface may be made up of a mesh-like array of one or more built-up interconnected layers. A particular shape of the exterior lattice may define a diamondlike diagonal pattern along the length (i.e., fluid flowpath) of the tube, although patterns of other shapes and regular or irregular geometric configurations - as well as patterns made up of multiple layers - may also be created.

[0008] According to another aspect of the invention, a heat exchange tube is disclosed that is made up of a first fluid flowpath defined along an interior surface of the tube, and a second fluid flowpath defined along an exterior surface of the tube such that the first fluid flowpath and the second fluid flowpath are in thermal communication with one another to define a heat exchange region within the tube. In particular, additive manufacturing is employed to produce the tube. Additive manufacturing would allow the use of more complex geometries in the tube in general and the heat exchange region in particular.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0009] The following detailed description of the preferred embodiments of the present invention can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

FIGS. 1A through ID show various views and forms of a heat exchanger tube with internal and external repeating lattice structure according to an aspect of the present invention;

FIGS. 2A and 2B show respectively end and perspective views of an embodiment of the heat exchanger tube highlighting an embodiment of external multilayered lattice structure according to an aspect of the present invention; and

FIG. 3 shows a system used to perform additive manufacturing in order to produce the tube of FIGS. 1A through ID, 2A and 2B.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Various forms of heat exchanger tubes that employ a lattice (or mesh) structure can be made by additive manufacturing. Significantly, the present structure is such that the largely open construction inherent in the lattice structure results in enhanced dissipation of heat passing from the fluid that is in or around the tube to the ambient environment. The present inventor has observed that the present lattice-based construction contributes to significant increase in cooling improvement over conventional heat exchangers with tube with radial fin-based designs. [0011] Referring first to FIGS. 1A through ID, a first embodiment of a heat exchange tube 10 is shown with the lattice-based intermittent structure formed on an interior surface and an exterior surface of the tube 10. FIGS. 1A and IB show respectively a cutaway view taken down the length of tube 10, where FIG. 1A in particular reveals a bifurcated internal fluid flowpath 12 along the substantial length thereof, where a first portion 12F and a second portion 12S correspond to the individual flowpaths defined by the bifurcation. Although not shown, it will be appreciated by those skilled in the art that other configuration for flowpath 12 (including those of a concentric nature, as well as those of a series of compartmentalized segmented nature, depending on the need) may also be employed, and that such configurations are within the scope of the present invention. In one notional (i.e., non-limiting) form, the tube 10 is approximately 12 inches in length with a bifurcated set of fluid flowpaths running the substantial length thereof of and possessive of about a 0.1 inch channel height and a 0.2 inch overall (i.e., including wall thicknesses) channel height.

[0012] Each of the bifurcated portions of flowpath 12 includes an interior lattice structure 14 that may be made up of pins, posts, baffles or related projecting structure, as well as an exterior lattice structure 18. FIG. IB shows a top-down partial cutaway view of the first portion 12F of flowpath 12 in order to better see the interior lattice structure 14 that is made up of a series of pins or posts 16 that may extend from an inwardly-projecting surface 10A of the outer wall of tube 10 to an outwardly-projecting surface 10B of one or more inner walls. Such lattice structure 14 promotes enhanced interaction of the fluid present in the flowpath 12 with the adjacent walls of the tube 10, but does so in a way that keeps the flowpath from become too tortuous. FIG. 1C shows a perspective view the portion of tube 10 with the exterior lattice structure 18 of FIGS. 1A and IB removed to give a more clear view of one possible form of the exterior surface of tube 10. Such form generally resembles two trapezoidal shapes stacked on top of one another at their adjacent narrow ends. FIG. ID shows an end view aligned along the axial dimension of tube 10 to emphasize the lateral dimension across the tube 10, as well as the general shape thereof and the placement of the exterior lattice structure 18.

[0013] Referring next to FIGS. 2A and 2B, while the internal flowpath 12 forms one portion (specifically, the interior lattice structure 14 portion) of the overall heat exchange region of tube 10, the other portion (specifically, the exterior lattice structure 18 portion) can be used to better highlight with specificity the lattice-like nature of the heat exchange structure. The perspective view of FIG. 2A highlights the placement of the exterior lattice structure 18 on the tube 10 exterior surface, while FIG. 2B highlights the repeating nature of the built-up layered structure of the exterior lattice structure 18 where numerous individual layers extend from the bottom 18B to the top 18T. Each built-up layers may be made of a series of horizontal members 18H and vertical members 18V, where such members may be generally similar in size, construction, aspect ratio and other properties to the pins, rods and posts 16 shown above in conjunction with FIGS. 1A through IE. As with the interior lattice structure 14, the exterior lattice structure 18 is particularly amenable to the additive manufacturing approach discussed herein where numerous layers of a predetermined pattern may be built up one on top of another through the deposition and subsequent curing of a generally fluid precursor material. In a most comprehensive form, the 3D formation of such a tube 10 includes a layer-by-layer formation of one or all of the exterior lattice structure 18, interior lattice structure 14 and the tubular wall.

[0014] The present invention is particularly advantageous in producing varying tube geometries that are not possible with conventional methods. For example, a high aspect ratio passage can be used to increase surface area as a way to increase the amount of heat being exchanged. Optimized forms of tube 10 can be generated for a specific application based on packaging constraints, pressure loss requirements, fluid dynamic effects or the like. Likewise, interior features of tube 10 can be included to further promote the exchange of heat through increased fluid flow boundary layer effects. [0015] The generally axial shape of tube 10 need not be the sole shape for heat exchange applications. As such, the present invention may also be configured of tubes of other irregular shapes, such as coils or the like. Additionally (as mentioned above), numerous different lattice shapes or geometries may be designed, and each is deemed to be within the scope of the present invention. Thus, while FIG. 2A depicts with particularity a generally diamond- shaped diagonal pattern for the exterior lattice structure 18 other patterns are also possible, depending on the heat exchange needs of the application.

[0016] Referring with particularity to FIG. 3, a diagram generally depicting a tube manufacturing system 20 is shown. The system 20 includes a computer-based controller and a forming (i.e., material-dispensing) device in the form of a 3D printer, where particular forms are known as stereolithography or stereolithographic printing, or the like. With particular regard to 3D printing of metal powder precursors, two general approaches may be employed. The first involves laser sintering, while the second involves a combination of using a printing binder with sintering and infiltration or impregnation. An example of the second approach includes a substantially uniform deposition of metal powder particles at a preferred density in a layer-by-layer fashion. Each layer of deposited powder also receives a layer of binder material. This process is repeated until the desired geometric pattern is attained. Sintering or related thermal process heat treatment causes the powder to fuse together and the binder to evaporate. After this, the infiltration/impregnation material is added into the pores to more fully form the built-up structure.

[0017] Regardless of the form, complex parts such as the heat exchange tubes of the present invention can be produced in an additive fashion directly from data (such as computer-aided design (CAD) or related data) without the need for intermediate tooling, instead relying upon the forming device being able to deposit one or more layers of a generally curable material, such as a metal powder, as well as from a plastic or related synthetic resin where such resin may be either a liquid or a solid, the latter configured to be heated near its melting temperature. Examples of such plastics include acrylonitrile butadiene styrene (ABS), polycarbonate and nylon (and nylon-based) plastics. As mentioned above, in situations where the precursor material is a metal powder, sintering or related thermal processing may be the vehicle by which such curing takes place. Examples of such metals include steel and steel-based alloys (including stainless steel), in addition to alloys containing significant amounts of cobalt, chromium or both, as well as titanium alloys.

[0018] It will be appreciated by those skilled in the art that the locus for the computer-based operations is not critical; in this way, regardless of whether the 3D printer (or related apparatus) acts as a stand-alone device (i.e., is a separate entity from the primary computing or other data-processing activities), or is integral with - or configured to perform such - data processing and control functions, such a printer is considered to receive the processed data as part of the tube manufacture. Either form is deemed to be within the scope of the present invention. The data (for example, CAD data) used to instruct the forming device to make the heat exchange tube represents the geometric configuration of the tube, including tube, fin, aperture shapes and other structural dimensions. In this way, the data acts much like a blueprint that is used for the assembly or related fabrication of tube 10. The approach of the present invention enables geometric configurations of tube 10 that may be impossible to achieve with conventional manufacturing approaches.

[0019] In a preferred form, system 20 operates in an automated manner where a digital computer 22 or related electronic device may be programmed (through a code or related algorithm) in order to produce CAD data representation of the desired tube configuration. From there, the computer (which may act like a controller) cooperates with a 3D printer 40 in order to send instructions representative of the desired tube configuration to the printer. In a preferred form, the computer 22 preferably includes one or more of an input 24, an output 26, a processing unit 28 (often referred to as a central processing unit (CPU)) and memory 30 that can temporarily or permanently store such a code, program, program module or algorithm such that the instructions contained in the code are operated upon by the processing unit 28 based on CAD or related input data such that output data generated by the code and the processing unit can be conveyed to the printer 40 via electrical interconnect 32 between the two. Such input 24 (as well as the memory 30) may accept data structures (such as one or more CAD files as discussed above) pertaining to a particular tube 10 geometry or configuration. If needed, output 26 may be used to convey particular processing information to a computer operator, designer, fabrication supervisor or other user. In one form, a data-containing portion of the memory (also called working memory) is referred to as random access memory (RAM) 30A, while an instruction-containing portion of the memory (also called permanent memory) is referred to as read only memory (ROM) 30B. The electrical interconnect 32 may be part of a data bus or related set of wires and associated circuitry to form a suitable data communication path that can interconnect one or more of the input 24, output 26, processing unit 28 and memory 30, as well as the printer 40 or any other peripheral equipment in such a way as to permit the system 20 to operate as an integrated whole. In situations where system 20 is computer-based in the manner discussed above (as well as suitable variants thereof), it is referred to as having a von Neumann architecture (also referred to as a general purpose or stored-program computer). Likewise, a particularly-adapted computer or computer- related data processing device that employs the salient features of a von Neumann architecture in order to perform at least some of the data acquisition, manipulation or related computational functions, is deemed to be within the scope of the present invention, as are such computers where memory and related data storage may be effected in a remote location such as those of a cloud-based architecture.

[0020] It will be appreciated by those skilled in the art that computer-executable instructions (such as the aforementioned programs and program modules) are suitably written and designed to perform functions pertaining to size, shapes and related geometric attributes of tube 10, and that the particular nature of such code or its means of integration into the system 20 mentioned above is beyond the scope of the present invention. Suffice to say that such tube-generating software may reside in RAM memory 30A, flash memory 30C, ROM memory 30B, EPROM memory, EEPROM memory, registers, cloud, hard disk (which may also be the basis for the aforementioned RAM memory 30A and ROM memory 30B), removable disk 30D, CD-ROM, or any other form of storage medium known in the art. In this regard, an exemplary storage medium can be coupled to processing unit 28 such that the processing unit 28 can read information from, and write information to, the storage medium that may make up memory 30. In the alternative, the storage medium may be integral to the processing unit 28. As an example, the processing unit 28 and the storage medium may reside in an ASIC (application- specific integrated circuit such as a chip designed solely to run a cell phone such that instructions sent to the printer 40 may come from a remote source not otherwise physically coupled to such printer 40.

[0021] In one form, printer 40 employs an applicator or related material dispenser with a print head 42 that operates in a Cartesean three degree-of-freedom movement along x, y and z axes. A moveable platform 44 can be made to translate in the horizontal (i.e., x-y) plane; as each layer L of a desired workpiece W is printed, the platform 44 can be made to translate along the z-axis relative to the print head 42 such that the next layer L may be formed. Although not shown, additional support structure may be placed along portions of the platform 44 in order to reduce leakage or spillage of the precursor material. In the present context, workpiece W is preferably tube 10 that is discussed in detail above. Depending on the precursor material being used, the specific deposition process will vary. For example, stereolithographic processes dispense a liquid-based curable plastic, while fused deposition dispenses materials by extruding heated material through a nozzle that in turn cools and forms the workpiece W. Likewise, laser sintering methods may be used to produce plastic or metal parts by depositing material with the thermal aid of a laser, while sintered and infiltrated parts can be produced by first building part from metal particles with aid of binder, then sintering the part and infiltrating it with an impregnating material; such material may be the same or different from the base (i.e., precursor) powder.

[0022] Having described the invention in detail and by reference to preferred embodiments thereof, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims. More specifically, although some aspects of the present invention are identified herein as preferred or particularly advantageous, it is contemplated that the present invention is not necessarily limited to these preferred aspects of the invention.

Claims

1. A method of manufacturing a heat exchange tube, said method comprising: using a computer-based system to operate upon data that corresponds to a geometric configuration of said tube; and

configuring a forming device to deposit a material and receive instructions related to said data such that upon said receipt, said forming device builds up said tube with said material.

2. The method of claim 1, wherein said forming device is a 3D printer such that said 3D printer builds up said tube in a layer-by-layer deposition of said material.

3. The method of claim 2, wherein said material comprises a metal powder.

4. The method of claim 3, wherein said metal is selected from the group consisting essentially of steel, stainless steel, steel-based alloys, cobalt-chrome alloys and titanium alloys.

5. The method of claim 3, wherein said 3D printer employs at least one of (a) laser sintering and (b) printing binder, sintering and infiltrating to cure said deposited layers of metal powder.

6. The method of claim 2, wherein said material comprises a plastics-based synthetic material.

7. The method of claim 6, wherein said a plastics-based synthetic material is selected from the group consisting essentially of ABS, polycarbonate and nylon.

8. The method of claim 1, wherein said data being operated upon by said computer- based system is CAD data.

9. The method of claim 1, wherein said geometric configuration of said tube comprises a lattice structure formed within at least one internal fluid flowpath thereof.

10. The method of claim 1, wherein said geometric configuration of said tube comprises a lattice structure formed on an exterior surface thereof.

11. The method of claim 1, wherein said geometric configuration of said tube comprises a lattice structure formed on both an interior surface and an exterior surface thereof.

12. A method of manufacturing a metal-based heat exchange tube, said method comprising:

using a computer-based system to operate upon data that corresponds to a geometric configuration of said tube, said geometric configuration defining at least a portion of a heat exchange region within said tube as containing lattice structure; and configuring a forming device to deposit a metal powder and receive instructions related to said data such that upon said receipt, said forming device builds up said tube with said lattice structure with said metal powder.

13. The method of claim 12, wherein said geometric configuration corresponding to said heat exchange region defines at least a portion of a heat exchange fluid flowpath on at least one of an interior and exterior surface of said tube.

14. The method of claim 12, wherein said geometric configuration corresponding to said heat exchange region defines at least a portion of a heat exchange fluid flowpath on both said interior and exterior surfaces of said tube.

15. The method of claim 14, wherein an interior surface of said tube that corresponds to said lattice structure comprises intermittent structure made up of a plurality of repeating members that extend across at least a portion of a fluid flowpath formed on said interior surface.

16. The method of claim 14, wherein an interior surface of said tube that corresponds to said lattice structure comprises a mesh-like array formed over at least a portion of a fluid flowpath formed on said interior surface.

17. The method of claim 14, wherein an exterior surface of said tube that corresponds to said lattice structure comprises a mesh-like array formed over at least a portion of a fluid flowpath formed on said exterior surface.

18. The method of claim 17, wherein said mesh-like array comprises at least one layer of interconnected structure formed along a diagonal pattern.

19. The method of claim 18, wherein said mesh-like array comprises a plurality of layers stacked upon one another on said exterior surface.

20. A heat exchange tube comprising:

a first fluid flowpath defined along an interior surface of said tube; and a second fluid flowpath defined along an exterior surface of said tube such that said first fluid flowpath and said second fluid flowpath are in thermal communication with one another to define a heat exchange region within said tube, said tube formed using additive manufacturing.

21. The heat exchange tube of claim 20, wherein at least one of said primary fluid flowpath and said secondary fluid flowpath define a lattice structure.

22. The heat exchange tube of claim 21, wherein said tube is made from a metal powder deposited by said additive manufacturing.

23. The heat exchange tube of claim 22, wherein said additive manufacturing comprises a computer-based system cooperative with a 3D printer such that upon receipt of data that corresponds to a geometric configuration of said tube, said system forms said tube from said metal powder.