Heating element having open cell structure

Abstract

To provide a heating element that provides enhanced structural and mechanical properties, and particularly bending strength, to withstand vibration and movement of the heating element.SOLUTION: A heating element 23 includes a main body having a three-dimensional matrix with an open structure including openings extending throughout the main body and internal voids, cavities 15 and / or pores. The three-dimensional matrix is arranged as a lattice with repeating unit cells extending in three dimensions. The present heating element 23 is designed to maximize surface area to provide an effective and efficient thermal energy transfer medium.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heating element for the transfer of thermal energy. [Background technology]

[0002] Electric heaters typically include an electrical resistance heating element for heating a fluid or solid. Conventionally, a relatively thin alloy wire, strip, or tube is used as the heating element, with the heating effect being achieved by the passage of an electric current and the electrical resistance of the wire or tube.

[0003] Existing heating elements have limited energy transfer effectiveness, primarily due to their relatively small area-to-volume ratio. Larger heating elements can also be heavy and structurally weak, and therefore prone to deformation, sagging, and creep after repeated high-temperature operation.

[0004] It is also difficult to adapt conventional heating elements to the voltage / current sources available at the time of use and to achieve uniform heating of irregular solids in the case of heating by radiation.

[0005] Therefore, there is a need for more effective and efficient heating elements for transferring thermal energy in heating devices and the like.

[0006] U.S. Patent No. 3,244,860 discloses a gas heater including a metal mesh electrical resistance heating element disposed within a casing. A plurality of concentrically arranged individual mesh strips form the heating element. Gas flows through the casing and mesh strips and is thereby heated.

[0007] U.S. Patent Application No. 2018 / 0274817 discloses an inline fluid heater. The heater body is indirectly heated by an electrically heated heating element. The body includes an inlet and an outlet for the fluid to be heated. 3D printing of aluminum is proposed as a method for manufacturing the body, along with a tubular conduit extending through the body. Summary of the Invention

[0008] It is an object of the present invention to provide a heating element, which can be configured for use in a heating device, assembly, or apparatus, that provides enhanced thermal energy transfer from the body of the heating element to a receiving phase, such as a fluid flowing in contact with the heating element, or to a solid that is heated by radiation. A further specific object is to provide a heating element that provides enhanced structural and mechanical properties, and in particular bending strength, to withstand vibration and movement of the heating element relative to other components of the heating assembly, such as a surrounding or sealing ceramic block or other sub-body (optionally containing additional heating wire).

[0009] A further specific object is to provide a heating element having both structural and mechanical properties that allow it to withstand the stresses and general physical demands that arise during use as a result of large pressure differentials, gravity, and repeated heating gradients. In particular, one specific object is to provide a high strength, lightweight heating element that is adapted to resist deformation, sagging, and creep after repeated high temperature operation.

[0010] A further object is to provide a heating element that can be configured as a primary or active heating element through which current flows predominantly or preferentially. A further object is to provide a heating element that can be configured as a passive heating element for one or more sub-bodies through which current flows predominantly or preferentially, or for a sub-body that is heated by the combustion of a gas. In such implementations, the presented three-dimensional matrix can first provide structural support to the sub-body, such as a thin wire, strip, plate, or tube, and second significantly improve the heat transfer effectiveness of the sub-body, such as by increasing the surface area of ​​the sub-body.

[0011] These objectives are achieved by a heating element including a main body that is a three-dimensional matrix having an open structure defining openings, voids, and / or pores extending therethrough. The three-dimensional matrix is ​​provided as a lattice having repeating unit cells that define at least a portion of the main body. The main body includes at least two unit cells positioned adjacent to each other in a first direction, at least two unit cells positioned adjacent to each other in a second direction, and at least two unit cells positioned adjacent to each other in a third direction. The first, second, and third directions are disposed at angles to each other. This configuration maximizes the surface area-to-volume ratio of the heating element, thereby improving thermal energy transfer.

[0012] The three-dimensional lattice matrix has a regular structure. Therefore, irregular structures such as foam or nonwoven mesh are not three-dimensional lattice matrices. Therefore, the unit cells of the lattice of the three-dimensional matrix are regularly arranged in the main body. The unit cells of the lattice of the three-dimensional matrix may be symmetrically arranged in the main body. In the lattice of the main body, the first, second, and third directions defining adjacent positions of the unit cells extend at the same angle to each other. That is, the angle between the first direction and the second direction is equal to the angle between the second direction and the third direction and the angle between the first direction and the third direction.

[0013] The presented three-dimensional matrix / open structure is further advantageous for withstanding the thermal, physical, and mechanical demands within heating devices, heaters, ovens, furnaces, and the like. The presented heating elements are further advantageous because they can be formed into any shape and configuration. This is achieved because they are lightweight, strong, and manufacturable through techniques such as 3D printing and additive manufacturing. The open structure of the lattice matrix allows fluid to pass through the element without the need for dedicated openings within the structure. Such open structures can also provide structural support for solid heating elements. Thus, such solid heating elements can be designed in new ways that would not be possible without the lightweight structural support provided by the lattice matrix. Furthermore, such lattice matrix structures can also serve to increase the surface area of ​​the solid heating elements.

[0014] A further advantage of the present open-structure heating elements is the availability and freedom of choice to design almost any configuration of current and fluid flow paths through the matrix when the present elements are employed for direct resistive heating, i.e., active, if the matrix comprises a conductive material. Alternatively, the elements may be implemented for passive heating, i.e., in combination with at least one sub-body through which current is directed to flow predominantly or preferentially relative to the three-dimensional matrix portion of the element.

[0015] A relatively dense lattice matrix structure provides higher fluid flow resistance and lower electrical resistance than a less dense lattice matrix structure. Therefore, the present heating elements, when formed as, for example, a 3D printed structure, allow for the design of different paths for electrical current flow and fluid flow. Furthermore, the paths for electrical current flow may have different cross-sectional areas, thereby creating structural regions that may differ in material density, matrix pattern, type and / or shape, etc. The different paths for fluid flow may also have different cross-sectional areas throughout the heating element.

[0016] These considerations apply to both the main body matrix portion and / or the sub-body of the element. Optionally, the sub-body, e.g., at least one thin rod, wire, strip, plate, or tube, may be integrally formed with the main body open structure matrix. Optionally, the sub-body may be an integrally formed body with the main body, having a denser grid than the main body. Thus, the presented grid may be used as a passive reinforcing structure for the sub-body or as an element that serves / functions as a primary active conductor. Optionally, the sub-body has a lower electrical resistance than the main body.

[0017] Thus, the heating element may include an electrically conductive sub-body and a main body positioned adjacent to the sub-body.

[0018] The presently presented open structure configuration promotes stability of the heating element when mounted adjacent to other components of the heating device, such as a surrounding ceramic jacket block, additional heating elements, or an outer casing / housing. Specifically, the open structure matrix may be branched or include radial protrusions adapted for physical attachment or abutment to potentially adjacent components of the heating device. Such radial attachments may be integrally formed as part of the presently presented structure. For example, such stabilizing components may include stabilizing discs, rods, blocks, fins, braces, or flanges.

[0019] The present open structure matrix including the grid structure may be manufactured, for example, by additive manufacturing. The open structure matrix may include "terminals" at opposite ends of the grid structure, which allow connection of the grid structure to appropriate electrical connections / conduits for applying voltage to the heating element. Such terminals may be manufactured together with the grid structure, for example, by additive manufacturing, so as to be formed as a single unit. This is advantageous for providing a structurally strong element. Such a configuration would provide a heating element having an open grid structure region and respective terminal end regions that correspond to an overall denser or more solid body portion, for example, as a layer, plate, disc, or other generally solid body without the same type of openings, voids, or pores of the open matrix.

[0020] According to a first aspect of the present invention, there is provided a heating element, as defined in claim 1, comprising a main body that is a three-dimensional matrix having an open structure defining openings, voids and / or pores extending through the main body.

[0021] The present heating elements may be adapted to transfer heat to a fluid by conduction or convection, or to a solid by radiation. Of course, the present heating elements are suitable for use with a variety of different energy-receiving phases, including various fluids, such as gases or liquids, and solids.

[0022] The heating element may be configured for the transfer of heat in a heating device, assembly or apparatus.

[0023] A particular advantage of the present heating elements when employed to heat solid bodies by radiation is that the lattice open structure can be configured to provide a structural framework to structurally support and add strength to sub-bodies, e.g., generally denser or solid body portions, optionally formed integrally with the lattice main body or being separate sub-body heating elements positioned adjacent the present matrix. That is, the present open structural lattice structures provide desired stiffness and / or bending strength to the sub-bodies, especially when formed as relatively thin wire, strip, filament, or tubular-type bodies or elements that may be prone to deformation over time.

[0024] The heating elements described herein having an open structure are formed as a three-dimensional lattice structure matrix with openings and internal voids, pores, cavities, and grooves. This open structure is referred to herein by different terms such as three-dimensional structure, three-dimensional matrix, matrix lattice-like structure, lattice matrix structure, open structure of lattice matrix, lattice matrix, lattice matrix, open lattice structure, skeleton matrix, three-dimensional matrix open structure, three-dimensional open cell structure formed as a lattice structure, etc. Accordingly, the same type of structure may be referred to by these terms.

[0025] As used herein, the term "three-dimensional matrix" or "three-dimensional matrix" encompasses an ordered array, repeating unit cell arrangement, or lattice framework. That is, a three-dimensional matrix, lattice matrix, or the like, is a three-dimensional ordered structure having nodes and strands extending between the nodes in three dimensions, i.e., strands connecting at least some of the nodes to other nodes in three dimensions. Thus, a three-dimensional matrix forms a main body having a volume. Furthermore, the term also encompasses three-dimensional matrices having distinct regions of regular, aligned repeating units, where such regions differ in any one or combination of shape, pattern, apparent material density, thickness of the matrix "strands," e.g., cross-sectional area or width in a plane perpendicular to the flow of electric current and / or fluid. As used herein, matrix "strands" encompass main body portions that are branched or skeletonized to define a network and internal pores, voids, cavities, or openings. The three-dimensional strands of the matrix can be viewed as a skeleton, branched, or interconnected structure that defines internal pores, voids, or openings of regular size, shape, and distribution within specific regions. Thus, the strands can include threads, filaments, wires, rods, strips, and the like, which form the unit cell structure. The strands are connected at the nodes of the three-dimensional matrix. In other words, the nodes are formed at the connection points between at least three strands, or at least four strands, or at least six strands.

[0026] As used herein, the terms "lattice" and "lattice" refer to a framework comprising strands of a matrix.

[0027] Thus, the lattice comprises strands.

[0028] The strands also connect to each other at nodes to form a three-dimensional matrix lattice.

[0029] Reference herein to a matrix having an "open" structure encompasses a generally porous, rigid main body configuration that defines a porous or open-cell heating element. As an example, if the present heating elements are elongated in a cross-section perpendicular to the longitudinal axis, the cross-section will include material forming the strands / skeleton in addition to vacant, open, or unoccupied areas, referred to herein as pores, cavities, voids, etc.

[0030] The present heating elements may be formed as a body in which the skeletal matrix extends throughout the heating element body from the innermost region, section or core to the outermost surface.

[0031] However, the presently presented heating elements may be formed to include any shape and configuration of three-dimensional lattice structures that are pre-formed as an ordered array of repeating unit cells. Such structures include regular lattices that may include uniform, identical repeating cell structures throughout the heating element.

[0032] Alternatively, the present heating element may comprise regions of different lattice structures that define a uniform lattice structure. For example, the main body of the heating element may include at least a first region having a first lattice type and at least a second region having a second lattice type different from the first region. Optionally, the first and second regions may differ in one or a combination of the following: lattice shape or geometry; lattice density (i.e., lattice weight divided by total lattice space); cross-sectional area; thickness or width of the strands forming the lattice; size, shape, or number / quantity of openings, voids, and / or pores extending throughout the main body; or overall pattern in a particular region. Optionally, the first and second regions are positioned to extend longitudinally of the heating element between the respective terminal ends. Optionally, the first and second regions are positioned to extend transversely across the heating element relative to the longitudinal direction extending between the respective terminal ends. Optionally, the first and second regions are positioned to extend in a combination of longitudinal and width directions between opposite ends of the heating element relative to a longitudinal direction extending between the respective terminal ends. Optionally, the first and second regions are positioned to extend perpendicular to both the longitudinal and width directions.

[0033] The matrix is ​​provided as a lattice having repeating unit cells to define a main body having a pattern. Optionally, the pattern may be uniform in the main body, with openings, voids, and / or pores of generally uniform size and shape (i.e., generally equal dimensions) throughout the main body. Such a uniform main body configuration may be produced by additive manufacturing or other common manufacturing methods, in which the unit cells are repeated throughout the length and thickness of the body. Thus, the main body may be the result of an additive manufacturing process.

[0034] Optionally, the heating element main body may be elongated, i.e., the heating element comprising the lattice matrix may include what may be recognized as respective longitudinal ends, which may be configured as terminal ends for connection to suitable electrical conduits for the transmission of electrical current through the heating element and through the main or sub-body of the heating element.

[0035] Optionally, the diameter or width of one of the repeating cell elements of the matrix may be in the range of at least 0.1 mm, making it suitable for use in fixed or mobile heating devices, including electric heaters, ovens, furnaces, atomizers for electronic cigarettes, and the like.

[0036] Optionally, the main body may be formed as an elongated cylindrical structure.

[0037] Optionally, the heating element, particularly the main body, may be configured for passive or active heating. Specifically, a main body comprised of lattice structure repeating unit cells may be provided in combination with a sub-body, the sub-body being configured for active heating. Such a sub-body, optionally not integrally formed with the main body, may include a heating element positioned adjacent to, in close contact with, in partial close contact with, or in non-close contact with the three-dimensional main body of the present disclosure.

[0038] Thus, the main body, also called the primary body, in the form of a three-dimensional matrix may be active in the sense that it is heated directly by an electric current conducted through it, thereby heating it. The main body transfers its heat to the fluid. Alternatively, the main body in the form of a three-dimensional matrix may be passive in the sense that it is heated indirectly by secondary bodies. Again, it is the main body that transfers heat to the fluid.

[0039] When the present heating element includes a secondary body, the secondary body is preferably an active element with a lower electrical resistance than the primary body. In such a configuration, a small current is passed through the primary body lattice structure to provide a passive configuration. In such a configuration, the lattice structure primary body can be considered, first, to provide structural reinforcement to the secondary body (as the primary medium through which the current flows). Second, the lattice structure primary body provides an increased surface area to the secondary body, thereby improving heat transfer from the secondary body. Optionally, the primary body and secondary body may be integrally formed or manufactured by the same additive manufacturing process, such as 3D printing.

[0040] The secondary body is therefore active in the sense that it is heated by an electric current. The secondary body may be a wire, strip, filament, or tubular element. Alternatively, the secondary body may be a three-dimensional matrix of a different kind than the primary body.

[0041] Optionally, the main body may be provided as a core positioned within the secondary body. Optionally, the main body may be provided to at least partially surround a secondary body positioned at or near the core of the heating element. Optionally, the main body may be provided as a lateral extension of the secondary body, for example extending or protruding from one or more sides. Optionally, if the main body is elongate, it extends across all or most of the length, width or thickness of the secondary body so as to provide structural support between the respective ends of the secondary body.

[0042] The sub-body may be configured for primary electrical conduction. In such a configuration, the present three-dimensional matrix main body is adapted to be heated by direct intimate contact when an electric current is passed through the sub-body. The three-dimensional matrix main body thereby effectively provides the sub-body with increased surface area and improved bending strength. The sub-body may be denser or more solid than the main body, with a reduced degree of or no openings, voids, and / or pores extending therethrough. The sub-body may be made of the same material as the main body, or the main body and the sub-body may comprise different respective materials. If the material is an alloy, such "difference" may include the relative concentrations of the various elements of the alloy, or the alloys may differ in elemental composition.

[0043] Optionally, the heating element may further include a secondary body, which may be recognized as a frame or an open three-dimensional main body having at least one frame portion extending within and / or between regions of the frame portion. Specifically, the secondary body frame portion may define end regions, edges, and / or corners of the structure with an open matrix extending within and / or between denser or solid frame portions. The frame portion may be integrally formed with the open-cell main body; that is, the frame portion may be formed together with the open matrix by the same process, e.g., additive manufacturing. Optionally, the frame may be connected or attached to the main body of the present material. A denser or solid frame is advantageous for providing an optional primary path for current flow. Such a configuration is advantageous for minimizing the voltage applied to achieve a desired current. The denser or solid frame portion may be located at or near the center of the main body. Optionally, the frame portion may be located around the periphery of the heating element. Optionally, the frame may extend along the entire length of the heating element together with the three-dimensional open structure of the main body. The frame portion corresponds to a sub-body that is generally denser or solid compared to the open three-dimensional matrix. That is, preferably, the frame portion is generally solid, with significantly less or no internal voids, pores, or openings. If the frame portion is provided as a terminal end of the heating element, the matrix may extend between the terminals. Optionally, the frame portion may extend between the terminals relative to the open matrix to provide a primary path for current flow, and in such a configuration, the open matrix is ​​heated for passive heating, i.e., indirectly by heat conduction through the frame portion. Optionally, at least one frame portion may be provided within the three-dimensional lattice structure. Optionally, the heating element may include multiple frame portions that correspond to sub-bodies that are denser or made of solid material substantially free of openings, pores, and voids compared to the lattice structure of the main body.

[0044] Thus, the secondary body may comprise the same material as the main body and / or may be integrally formed with the main body.

[0045] According to an embodiment, the sub-body may extend longitudinally with the main body between respective terminals of the heating element.

[0046] According to an embodiment, the sub-body may extend widthwise or orthogonally to the length of the heating element.

[0047] Optionally, the presently presented heating elements may be manufactured by an additive manufacturing process. A variety of different additive manufacturing processes suitable for use with the presented types of materials may be employed.

[0048] As discussed above, the three-dimensional lattice structure matrix of the main body provides an advantageously large surface area to volume ratio for the heating element, thereby enhancing thermal energy transfer.

[0049] According to embodiments, the main body may include a surface area to volume ratio of 95:1 or less, such as 1:1 to 95:1.

[0050] According to embodiments, the conductive material may be selected from the group consisting of iron-chromium-aluminum alloys, nickel-chromium alloys, copper-nickel based alloys, iron-nickel-chromium alloys, nickel-iron-chromium-aluminum alloys, ceramic materials, and intermetallic materials. In this way, a conductive material can be provided that has a resistivity suitable for providing an active heating element when an electric current is passed through the three-dimensional matrix structure of the main body. Such materials are also suitable for additive manufacturing, thereby providing a suitable method for producing the main body.

[0051] According to an embodiment, the conductive material has a resistance of 0.1 Ωmm 2 / m to 1000Ωmm 2 The material may have a resistivity in the range of 1 / m.

[0052] According to an embodiment, the main body may be formed by an additive manufacturing process, i.e. the main body may be the result of an additive manufacturing process.

[0053] According to a further aspect of the present invention, there is provided a method of manufacturing a heating element of any one of the aspects and / or embodiments described herein by an additive manufacturing process.

[0054] According to a further aspect of the present invention, there is provided an electric heater comprising a heating element as described and claimed herein. According to a further aspect of the present invention, there is provided a furnace or oven comprising a heating element as described and claimed herein. According to a further aspect of the present invention, there is provided an atomizer for an electronic cigarette having a heating element as described and claimed herein. According to a further aspect of the present invention, there is provided an electronic cigarette comprising an atomizer as described and claimed herein.

[0055] Specific implementations of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0056] [Figure 1] 1 is a cross-sectional side view illustrating an electric heater incorporating a heating element according to a particular implementation of the present invention. [Figure 2] 1A-1C are diagrams illustrating various different grid configurations forming the main body of a heating element, according to certain implementations. [Figure 3] 2 is a perspective view showing a heating element for incorporation into an electric heater of the type of FIG. 1 according to one particular implementation. FIG. [Figure 4] 10A-10C show further embodiments of a heating element having a grid structure extending between regions of the frame. [Figure 5] 1 is a perspective view illustrating a heating element assembly including a main body and a secondary body, where the main body is formed as a lattice extending outwardly around the perimeter of a solid secondary body, according to a particular implementation. [Figure 6]FIG. 10 is a perspective view showing a further embodiment of the present invention formed as an assembly having a main body formed as a lattice structure corresponding to a core surrounded by generally tubular secondary bodies. [Figure 7a] FIG. 10 is a schematic diagram illustrating a unit cell configuration suitable for forming a lattice structure main body by a manufacturing process such as additive manufacturing, showing a face-centered cubic configuration. [Figure 7b] FIG. 10 is a schematic diagram illustrating a unit cell configuration suitable for forming a lattice structure main body by a manufacturing process such as additive manufacturing, showing a body-centered cubic configuration. [Figure 7c] FIG. 10 is a schematic diagram illustrating unit cells arranged adjacent to one another to form part of a lattice structure main body. [Figure 8] FIG. 1 is a perspective view showing a heating element formed as a single body, including a main body lattice structure extending between two terminal ends, with a frame portion sub-body extending longitudinally adjacent to the lattice structure main body between the terminal ends, according to a specific implementation. [Figure 9] FIG. 9 is an enlarged perspective view showing an end region of the heating element of FIG. 8 with the main lattice structure body removed for illustrative purposes. DETAILED DESCRIPTION OF THE INVENTION

[0057] Referring to Figure 1, electric heater 10 includes a casing in the form of a tubular sheath or housing 11 defining an internal chamber 17. Electric heater 10 includes a fluid inlet tube 21 and a fluid outlet nozzle 14 with an outlet tube 13. A fixing flange 20 is attached to a current supply flange 19, which is coupled to an external electrical connection 18. A centering extension 22, which may be part of the internal heating element, projects into tube 16 to help stabilize the heating assembly.

[0058] A jacket block 41 is mounted in place within the chamber 17 and includes an interior cavity 15 extending generally through the center of the electric heater 10 aligned on the longitudinal axis 12. The elongated cavity 15 is separated from the outer housing 11 via the jacket block 41, which is made of a suitable insulating ceramic material. A heating element 23 is mounted within the cavity 15.

[0059] According to the proposed configuration, the heating element 23 includes a three-dimensional open cell structure formed as a lattice structure.

[0060] The heating element 23 is generally elongated and includes a first longitudinal end 23a positioned at the outlet nozzle 14 and a second longitudinal end 23b positioned at or near the terminal end of the fluid inlet tube 21. The heating element 23 is connected to the external electrical connection 18 via an appropriate intervening electrical conduit (not shown). Thus, a voltage can be applied to the heating element 23 via the conduit and the electrical connection. In use, a fluid, such as a gas, is supplied into the electric heater 10 via the inlet tube 21 so that it flows over, through, and in contact with the three-dimensional lattice of elements 23 within the cavity 15. Because the heating element 23 is formed from an electrically resistive material, the fluid is heated as it flows from the tube 21 into contact with the heating element 23 and is then discharged from the device 10 via the nozzle 14 and the discharge tube 13.

[0061] To maximize the efficiency and effectiveness of thermal energy transfer between the heating element 23 and the fluid flowing within the cavity 15, the present heating element 23 includes an open three-dimensional matrix with openings, internal voids, pores, cavities, channels, etc. extending across and defined by the lattice structure matrix of its main body. That is, the present heating element 23 can be considered to include a solid / rigid skeleton-like configuration. The lattice structure provides a significantly increased heating surface to fluid volume ratio compared to conventional heating elements.

[0062] Referring to FIG. 1, the present heating element 23 may be formed as a regular repeating unit cell with openings, voids, and pores of generally uniform size and shape, i.e., of approximately equal dimensions, throughout its main body. Such a uniform, regular lattice structure provides control over the efficiency and effectiveness of thermal energy transfer to the flowing fluid. Furthermore, such a configuration minimizes temperature gradients across the heating element both longitudinally and radially relative to axis 12. Of course, the relative shape, size, and overall dimensions of the lattice structure, as shown in FIG. 2, can vary depending on the particular implementation.

[0063] The presently presented open cellular configuration of the heating element 23 can be fabricated by techniques such as additive manufacturing and computer model-based engineering manufacturing methods adapted to provide a repeating unit cell configuration in which the main body 25 of the heating element 23 forms a skeletal framework that defines the opening 26 and the interior cavity 27.

[0064] 2 schematically illustrates various different lattice configurations that form the main body 25 of the heating element 23. More specifically, the main body 25 includes at least a first region 60 having a first lattice type and a second region 62 having a second lattice type that is different from the first region 60.

[0065] In these embodiments, the main body 25 includes six distinct regions 60-70. The first region 60 and two additional regions 64, 68 have a first lattice type. The remaining three regions have different lattice types. As previously described, the second region 62 has a second lattice type. The third region 66 has a third lattice type, and the fourth region 70 has a fourth lattice type. In this manner, for example, the three regions 60, 64, 68 having the first lattice type may be positioned adjacent to an electrically heated secondary body (not shown). The first lattice type may provide favorable heat transfer from the secondary body to the main body 25, while the second, third, and fourth regions 62, 66, 70 may provide optimal heat transfer to a fluid passing through the main body 25. Optionally, the second, third, and fourth regions 62, 66, 70 may provide different pressure drops to fluid passing therethrough, with, for example, the highest pressure drop provided by the second region 62, the third region 66 providing an intermediate pressure drop, and the fourth region 70 providing the lowest pressure drop. According to another embodiment, all six regions 60-70 of the main body 25 may have different lattice types. According to a further embodiment, the regions 60-70 of the main body 25 may have only the first lattice type and the second lattice type.

[0066] Referring to FIG. 3 , the heating element 23 may be formed as a hollow cylinder in which the lattice structure of the main body 25 defines a cylindrical wall having an opening 26 and an internal void 27. Specifically, the lattice structure cylinder is hollow and defined by the cylindrical wall, and the cylindrical wall is also open to the opening 26 and the internal void 27. The cylindrical wall includes a three-dimensional lattice structure matrix structure. First and second longitudinal terminal ends 30 a, 30 b of the heating element 23 are provided as solid disks. The terminal ends 30 a, 30 b may be integrally formed with the main body 25 or may be welded or attached to the main body 25. First and second connectors 28, 29 extend axially from each of the respective heating element terminal ends 30 a, 30 b. Thus, an electric current can be applied to the heating element 23, as described with reference to FIG. 1 . The increased surface area of ​​contact between the heating element 23 and the flowing fluid as a result of the three-dimensional open lattice structure results in more efficient and effective heating of the fluid compared to conventional solid heating elements. The size and shape of the internal voids, pores, and cavities defined by the skeleton structure can be varied to achieve a desired overall / total surface area, thereby affecting the flow rate and path of the fluid through the heating element 23.

[0067] According to a more specific implementation of the embodiment of Figure 3, the main body 25 may extend across the entire cylinder as a lattice structure extending from the axial center to the outer surface of the cylinder. As in the embodiment of Figure 3, electrical current is then applied to the lattice structure main body 25, which is then configured to be "active" to provide a primary body with electrical current flowing between its terminal ends. In this implementation, fluid is preferably applied to the main body in a manner transverse to the axial extension.

[0068] According to a further implementation of the configuration of FIG. 3 , a secondary body, such as a solid rod, strip, or wire (not shown), of the same material as the lattice structure main body 25 or of a different suitable material, may extend axially inwardly within the lattice structure main body 25 and between the terminal ends 30 a, 30 b. In such a configuration, the secondary body provides a primary current path, which would be considered “active,” while the lattice structure main body 25 can be considered to provide structural reinforcement for the secondary body and would be considered “passive,” providing indirect heat transfer from the current flow through the secondary body. The lattice structure main body provides the secondary body with an increased surface area, which effectively increases heat transfer from the secondary body.

[0069] According to certain implementations, the heating element 23 may extend continuously from the axial center to its radially outermost surface region (furthest radially from the axis 12). However, as shown in FIG. 3 and described above, the heating element 23 may be formed macroscopically as a hollow body, where the lattice structure of the main body 25 may define a cylindrical wall. According to one embodiment, a fluid may be injected into the center and / or outer region of the cylinder and / or may be directed to flow throughout the entire area of ​​the heating element 23, including the internal bore and the outer surface. Optionally, various embodiments according to FIG. 3 and other embodiments described herein may be configured and operable as a radiating element to radiate thermal energy in response to the flow of electrical current directly or indirectly through the main body 25.

[0070] A further embodiment of the presently disclosed heating element will be described with reference to FIG. 4. According to this further embodiment, the heating element is formed as an assembly including a frame portion 32 into which extends a lattice structure of a main body 25 having an open three-dimensional structure. The frame portion 32 is a minor body. The frame 32 includes longitudinally extending edge supports 33 and widthwise extending cross braces 34. The frame 32 further includes first and second longitudinal ends 31 a, 31 b. The longitudinally extending edge supports 33 and the cross braces 34 define an opening 35 through which the lattice structure main body 25 extends. Suitable terminal connections 28, 29 (not shown in FIG. 4) are connectable to the first and second longitudinal ends 31 a, 31 b to allow voltage and current to be applied to the heating element 23. According to the embodiment of FIG. 4 , current flows primarily through the frame 32, i.e., the secondary body, and in particular through the solid longitudinal support portion 33. However, some current will / may flow through the lattice structure main body 24. Thus, the lattice structure body 25 generates heat due to the current flow and / or may be heated by thermal conduction through direct contact with the frame 32 or by radiation from the frame 32. Such a configuration may be advantageous in minimizing the risk of short circuits or unstable current flow due to operation at high voltages. That is, the incorporation of the frame portion 32 facilitates current flow through the heating element 23 compared to a heating element having only the lattice structure body 25, which has a higher electrical resistance, thereby allowing for a reduced applied voltage.

[0071] Traditionally, heating elements may be formed by electrically resistive cylindrical rods. According to the configuration of FIG. 4, the edge supports 33 can be considered to be four quarters of such cylindrical rods. The spatial separation of the supports 33 enhances the structural strength of the heating element compared to conventional cylindrical rods. However, the cross-sectional area of ​​the supports 33 is the same as that of the cylindrical rods. Thus, the overall resistance of the supports 33 is maintained from the rods, while the structural strength of the heating element is significantly increased. At the same time, the heating effect is maintained. Naturally, the main body 25 in the configuration of FIG. 4 is considered "passive" (not a primary current path), while the supports 33 are considered "active." In such an embodiment, the main body 25 provides additional structural reinforcement for the supports 33 and an increased heating surface area contacted by the fluid passing through the heating element 23.

[0072] A further embodiment in which the lattice structure main body is formed as a cylindrical hollow tube is described with reference to FIG. 5 . A secondary body 37 extends through an internal elongated bore 36 defined by the cylindrical wall of the main body 25. The secondary body 37 may be, for example, a wire, rod, or tube. The secondary body 37 comprises a non-porous, denser, or solid material specifically adapted for use as a heating element. According to the embodiment of FIG. 5 , the secondary body 37 is positioned within the bore 36 and may or may not be in direct contact with the interior-facing surface area of ​​the main body 25. The main body 25 and secondary body 37 may be in direct intimate contact with each other through further configurations or may be integrally formed. In use, a voltage can be applied directly to the secondary body 37 to function as an active conductor. While some electrical conductivity may occur in the main body 25, in some embodiments, the main body 25 is not directly adapted to carry electrical current and is considered passive. In either case, the secondary body 37 may be heated by an applied voltage, and the primary body 25 may be heated by direct contact, radiation and / or conduction.

[0073] The present heating element can be adapted for use as a conductive heating element, in which a fluid is induced to flow through the main body 25, functioning in either an active or passive mode. Additionally, fluid can flow through the secondary body 37, such as when the secondary body is a tube. Alternatively, the present heating element may be employed as a radiator, transferring thermal energy to, for example, a nearby or adjacent solid object / mass. When operated as a conductive heating element, fluid flowing in contact with the main body 25 can be allowed to flow through and within the main body lattice structure, as described above, for efficient and effective thermal energy transfer. In the configuration of FIG. 5, the lattice structure main body 25 surrounds the conductive secondary body 37, forming a sleeve or exterior that provides structural reinforcement and increased surface area.

[0074] According to a further embodiment shown in FIG. 6, the lattice structure main body 25 may be formed as the core of a heating element assembly similar to the embodiment of FIG. 5 having the sub-body 37. However, according to the embodiment of FIG. 6, the sub-body 37 is provided as a hollow, elongated cylinder or tubular body with the main body 25 extending through a central interior hole 40 of the sub-body 37. As described with reference to FIG. 5, a voltage can be applied directly to the sub-body 37, which results in direct or indirect heating of the main body 25 by direct contact and / or conduction. As described with reference to the electric heater of FIG. 1, a fluid can be injected into the central hole 40. In such an embodiment, the main body 25 provides a high surface-to-volume ratio compared to an "empty" sub-body. The main body 25 also provides structural reinforcement for the sub-body 37. The main body 25 also creates turbulence in the fluid flowing through the lattice structure, resulting in improved heating efficiency.

[0075] The matrix or main body 25 comprises at least one electrically conductive material.

[0076] The three-dimensional lattice structure main body 25 of the present invention may be made of any conventional material designed for use as a heating element, such materials being generally recognized as electrically resistive materials, and resistant to high temperature creep and corrosion, oxidation, and carbonization.

[0077] Such conductive materials may be selected from the group consisting of iron-chromium-aluminum alloys, nickel-chromium alloys, copper-nickel-based alloys, iron-nickel-chromium alloys, nickel-iron-chromium-aluminum alloys, ceramic materials, and intermetallic materials. For example, iron-chromium-aluminum alloys exhibit corrosion resistance and high-temperature creep strength. Nickel-chromium alloys and iron-nickel-chromium alloys exhibit corrosion resistance, but also high-temperature mechanical strength and good processability. Copper-nickel-based alloys also exhibit good thermal conductivity and good wet corrosion properties. Furthermore, iron-nickel-chromium-aluminum alloys exhibit overall mechanical strength, corrosion resistance, and metal dusting resistance. The ceramic materials or intermetallic materials exhibit stability at high temperatures exceeding 1300°C.

[0078] The presented open-cell three-dimensional structure provides a further advantageous structure for enhancing the physical and mechanical strength of the heating element and / or increasing the heating area of ​​the heating element. Due to the lightweight and structurally strong lattice-structured main body 25, the presented heating element can be formed with an unlimited number of high-strength structures having one or more repeating cell contours that define a regular lattice structure. Specifically, the presented open-cell three-dimensional structure may include regions with different repeating cell structures, which further provide regions that provide different structural support to the sub-body and / or current paths with different resistances and therefore different magnitudes of energy transfer by conduction and / or radiation. Specifically, the bending strength of the heating element may be enhanced compared to conventional solid-body heating elements. Furthermore, the open structure may facilitate the attachment of position-stabilizing components, rods, braces, or flanges for mounting and / or securing the heating element 23 in place within a heating device of the type shown in FIG. 1. According to a further specific implementation, the grid may be designed to include position support protrusions that are integrally formed as part of the main body 25 and extend radially outward from the shaft 12 towards and into contact with the jacket block 41 and / or the housing 11. Such protrusions may be attached to suitable mounting locations to positionally stabilize the heating elements 23 in place.

[0079] The three-dimensional open structure may be designed to achieve a desired surface area in contact with the volume of flowing fluid. Such a surface-to-volume ratio may be defined, based on the unit cell (see below) of the lattice structure main body 25, as the ratio of the total surface area of ​​the unit cell to the total volume of the solid portion of the unit cell. That is, the surface area of ​​the strands and nodes of the lattice structure relative to the volume of the strands 45 and nodes. According to one embodiment, the surface area-to-volume ratio is 95:1 or less, such as 1:1 to 95:1. Such a configuration of the heating element 23 may be provided as a single main body 25 having regions of a single repeating unit cell or different unit cells, and / or as an assembly having the main body 25 combined with sub-bodies 37. Specifically, the heating element 23 may be formed as a main body 25 that is a continuous skeletal framework as described in FIGS. 2 and 3, a framed structure / assembly as shown and described with reference to FIG. 4, or a multi-component assembly as described with reference to FIGS. 5 and 6.

[0080] Referring to FIGS. 7a and 7b, the main body 25 can be seen as consisting of repeating unit cells, each consisting of solid strands 45 connected or branched to define a three-dimensional matrix. The strands 45 are connected at nodes to form the three-dimensional matrix. The main body 25 may include a single type of unit cell that repeats throughout the entire volume of the lattice structure, or it may include multiple different unit cell configurations to form distinct regions, e.g., first and second regions 60, 62, as described above with reference to FIG. 2, that differ in surface area-to-volume ratio and, therefore, size, shape, and multiplicity of internal cavities / pores 27. According to the unit cell configuration of FIG. 7a, the main body 25 may be composed of, for example, face-centered cubic (fcc) unit cells, or, referring to FIG. 7b, body-centered cubic (bcc) cells, or a combination thereof. The unit cells may have a diameter or width of at least 0.1 mm. The strands 45 may have a diameter of at least 0.05 mm.

[0081] In some embodiments, the lattice may include strands 45 having a diameter or mean diameter greater than 0.05 mm, such as between 0.05 mm and 4 mm. The diameter and mean diameter of the strands 45 are measured perpendicular to the longitudinal extension of the strands 45. If the strands 45 do not have a circular cross section, the mean diameter is the average diameter.

[0082] Figure 7c shows a number of unit cells 72 of a portion of the main body 25 of the heating element. Each unit cell 72 is shown schematically as a cube and may be one of the types described in relation to Figures 7a and 7b. However, the unit cells 72 are not limited to the illustrated embodiment and may have any suitable internal structure of the strands, and may have any other suitable external shape, such as, for example, a tetrahedral shape.

[0083] The unit cells 72 are positioned adjacent to one another in three dimensions, i.e., strands of adjacent unit cells 72 share nodes. More specifically, at the corners of each unit cell 72, strands from adjacent unit cells 72 connect to one another, thus forming nodes. The unit cells are positioned adjacent to one another in three dimensions because each unit cell 72 is surrounded by other unit cells 72 except for the outer surface of the main body 25. Thus, the main body 25 includes at least two unit cells 72, 72' positioned adjacent to one another in a first direction d1, at least two unit cells 72, 72'' positioned adjacent to one another in a second direction d2, and at least two unit cells 72, 72''' positioned adjacent to one another in a third direction d3, the first, second, and third directions d1, d2, d3 being disposed at angles to one another. For example, if the unit cell 72 has a cubic shape as shown, the three directions d1, d2, and d3 are orthogonal, and if the unit cell 72 has a tetrahedral shape, the three directions extend at angles of 120 degrees relative to each other.

[0084] A further embodiment of the heating element is described with reference to FIG. 8 . According to this embodiment, the lattice structure main body 25 extends axially between two terminal ends 46 a, 46 b. Each terminal end 46 a, 46 b is formed as a solid sub-body from the same material as the lattice structure 25. The sub-body includes a frame portion 47 that extends axially between the terminal ends 46 a, 46 b that are directly adjacent to the lattice structure main body 25. The frame portion 47, the terminal ends 46 a, 46 b, and the main body 25 are integrally formed, preferably by a process such as additive manufacturing. The frame portion 47 includes slots 48 to modify the current flow characteristics and, in particular, the electrical resistance of the frame portion 47. In this configuration, the main body 25 provides structural support to the frame portion 47, and the main body 25 is considered passive, while the frame portion 47 is considered active as the primary current path. The main body 25 is therefore responsible for the thermal energy transfer, this heat being provided indirectly from the active heating element, ie, the flow of electrical current primarily through the frame portion 47 .

[0085] FIG. 9 is an enlarged end view of the heating element of FIG. 8 with the lattice structure main body removed for illustrative purposes. As shown, terminal end 46a comprises a relatively short plate positioned orthogonally to the elongated heating element, i.e., main body 25, and to the active current frame portion 47. Terminal ends 46a, 46b have a significantly larger cross-sectional area in a plane perpendicular to the direction of current flow between terminal ends 46a, 46b than either frame portion 47 or main body 25. Therefore, the larger cross-sectional size of terminal ends 46a, 46b prevents terminal ends 46a, 46b from radiating heat. The cross-sectional area of ​​lattice structure main body 25 is relatively small so that only negligible current flows through the lattice of main body 25. Therefore, lattice main body 25 is provided as a passive component. As shown in FIG. 9, the cross-sectional area of ​​frame portion 47 is smaller than that of terminal ends 46a, 46b, resulting in higher electrical resistance and, therefore, a greater heating effect. As shown in the embodiment of FIGS. 8 and 9, frame portion 47 includes a serpentine path extending longitudinally between terminal ends 46a, 46b with slots 48 therethrough.

[0086] As can be seen, the frame portion 47 includes a wider current path area 49 compared to a narrower flow path area 50. Therefore, the electrical resistance in the narrow area 50 is greater, resulting in increased thermal energy transfer. The active frame portion 47 therefore includes areas 49, 50 along its length (between terminal ends 46 a, 46 b) that provide a selective heating effect, which may be advantageous for providing selective heating zones within a heating device. Such a configuration may be used for heating irregular solid objects, for example, to obtain uniform heating of the irregular object by selective heating of different zones / zones of the irregular object.

[0087] Depending on the particular implementation, the terminal ends 46 a, 46 b may have different cross-sectional areas in both their width and length directions, such that the cross-sectional area in a plane perpendicular to the direction of current flow, i.e., between the ends 46 a, 46 b, may taper outward from the lattice structure main body 25 toward the outer casing of the heating device.

[0088] With reference to the summary of the invention above and the detailed description of the preferred embodiments, an itemized listing of the invention is provided. - Item 1. A heating element in a heating device, assembly or apparatus, the heating element comprising: Includes a main body, A heating element wherein the main body is a three-dimensional matrix having an open structure defining openings, voids and / or pores extending through the main body. Item 2. The heating element of item 1, wherein the matrix is ​​provided as a lattice having repeating unit cells to define a main body having a pattern. Item 3. The heating element of item 2, wherein the pattern is uniform and the main body includes openings, voids and / or pores of generally uniform size and shape throughout the main body. Item 4. The heating element of item 1 or 2, wherein the main body includes at least a first region having a first lattice type and at least a second region having a second lattice type different from the first region. Item 5. The first area and the second area are - the shape or profile of the grid; - density of the lattice, - the cross-sectional area, thickness or width of the strands forming the lattice; - the size, shape or number of openings, voids and / or pores extending through the main body, and any one or combination thereof. Item 6. The heating element according to item 4 or 5, wherein the first region and the second region are positioned to extend in the lengthwise direction and / or widthwise direction between opposite ends of the heating element, relative to the longitudinal direction extending between the respective terminal ends. Item 7. The heating element according to any one of items 1 to 6, wherein the matrix comprises a corrugated, skeletal, or cage-shaped framework or structure. Item 8. The heating element according to any one of items 1 to 7, wherein the matrix comprises at least one electrically conductive material. Item 9. The heating element of item 6, wherein the main body extends radially from a center of the heating element to an outer surface of the heating element. Item 10. The heating element of any one of items 1 to 9, including an electrically conductive sub-body, the main body being positioned adjacent to the sub-body. Item 11. The heating element according to item 10, wherein the secondary body comprises the same material as the primary body and / or is integrally formed with the primary body. Item 12. The heating element of item 10 or item 11, wherein the secondary body is denser or more solid than the primary body and has fewer or no openings, voids and / or pores extending through the primary body. Item 13. The heating element according to any one of items 10 to 12, wherein the sub-body extends longitudinally with the main body between respective terminals of the heating element. Item 14. The heating element of any one of items 10 to 13, wherein the sub-body extends across the width of the heating element or perpendicular to the length of the heating element. Item 15. The heating element of any one of items 10 to 14, wherein the sub-body comprises a uniform or varying cross-sectional area, width or thickness. Item 16. A method for manufacturing a heating element according to any one of items 1 to 15 by an additive manufacturing process.

Claims

1. A heating element (23), It includes a main body (25), said main body (25) being a three-dimensional matrix having an open structure defining openings, voids and / or pores extending through said main body (25); the three-dimensional matrix is ​​provided as a lattice having repeating unit cells (72) so as to define at least a portion of the main body (25); the main body (25) includes at least two unit cells (72, 72') positioned adjacent to each other in a first direction (d1), at least two unit cells (72, 72'') positioned adjacent to each other in a second direction (d2), and at least two unit cells (72, 72''') positioned adjacent to each other in a third direction (d3); The heating element (23), wherein the first, second and third directions (d1, d2, d3) are arranged at an angle to each other.

2. 2. The heating element of claim 1, wherein the grid comprises strands (45).

3. 3. The heating element of claim 2, wherein the strands (45) are connected to one another at nodes to form the lattice of the three-dimensional matrix.

4. 4. The heating element (23) of claim 1, wherein the repeating unit cells (72) defining the main body (25) have a pattern, the pattern being uniform, and the main body (25) includes openings, voids and / or pores of generally uniform size and shape throughout the main body (25).

5. 4. The heating element (23) of claim 1, wherein the main body (25) includes at least a first region (60) having a first lattice type and at least a second region (62) having a second lattice type different from the first region (60).

6. The first region and the second region (60, 62) are the shape or contour of the lattice; the density of the lattice; and The cross-sectional area, thickness or width of the strands forming the lattice; the size, shape or number of openings, voids and / or pores extending through the main body (25); 6. The heating element (23) of claim 5, wherein any one or combination of:

7. 7. A heating element (23) as described in claim 5 or 6, wherein the first and second regions (60, 62) are positioned to extend longitudinally and / or widthwise between both ends of the heating element, with respect to a longitudinal direction extending between the respective terminal ends.

8. A heating element (23) according to any one of claims 1 to 7, wherein the matrix comprises at least one electrically conductive material.

9. 9. The heating element (23) of claim 8, wherein the electrically conductive material is selected from the group consisting of iron-chromium-aluminum alloys, nickel-chromium alloys, copper-nickel based alloys, iron-nickel-chromium alloys, nickel-iron-chromium-aluminum alloys, ceramic materials, and intermetallic materials.

10. The conductive material has a resistance of 0.1 Ωmm ２ / m to 1000 Ωmm ２ 10. The heating element (23) according to claim 8 or 9, having a resistivity in the range of up to 1 / m.

11. 11. The heating element (23) of any one of claims 1 to 10, wherein the main body comprises a surface area to volume ratio of 95:1 or less, such as from 1:1 to 95:

1.

12. 12. The heating element (23) of any one of claims 1 to 11, wherein the grid comprises strands (45) having a diameter or average diameter greater than 0.05 mm, such as from 0.05 mm to 4 mm.

13. The heating element (23) according to any one of claims 1 to 12, wherein the main body is the result of an additive manufacturing process.

14. 14. A heating element (23) according to any one of claims 1 to 13, comprising an electrically conductive sub-body, said main body being positioned adjacent said sub-body.

15. 15. A heating element (23) according to claim 14, wherein the sub-body comprises the same material as the main body and / or is integrally formed with the main body.

16. 16. A heating element (23) according to claim 14 or 15, wherein the secondary body is denser or more solid than the main body and has fewer or no openings, voids and / or pores extending through the main body.

17. 17. A heating element (23) according to any one of claims 14 to 16, wherein the sub-body extends longitudinally with the main body between respective terminals of the heating element.

18. 17. A heating element (23) according to any one of claims 14 to 16, wherein the sub-body extends across the width of the heating element or perpendicular to the length of the heating element.

19. A method for manufacturing a heating element (23) as claimed in any one of claims 1 to 18 by an additive manufacturing process.

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