HEATING ELEMENT WITH OPEN-CELL STRUCTURE

Abstract

A heating element comprises a main body having a three-dimensional matrix with an open structure including openings and internal voids, cavities and/or pores extending throughout the main body. The three-dimensional matrix is provided as a lattice having a repeating unit cell extending in three directions. The present heating element is adapted for maximised surface area so as to provide an effective and efficient thermal energy transfer medium.

Claims

1. A heating element comprising: a main body, the main body being a three-dimensional matrix having an open structure defining openings, voids and/or pores extending through the main body, wherein the three-dimensional matrix is provided as a lattice having a repeating unit cell to define at least part of the main body), wherein the main body comprises at least two unit cells positioned adjacent to each other in a first direction (d1), at least two unit cells positioned adjacent to each other in a second direction (d2), and at least two unit cells positioned adjacent to each other in a third direction (d3), and wherein the first, second, and third directions are arranged at an angle to each other.

2. The heating element as claimed in claim 1, wherein the lattice comprises strands.

3. The heating element as claimed in claim 2, wherein the strands connect to each other in nodes to form the lattice of the three-dimensional matrix.

4. The heating element as claimed in claim 1, wherein the repeating unit cell defining the main body has a pattern and the pattern is uniform and the main body comprises openings, voids and/or pores of a size and shape that are generally homogenous throughout the main body.

5. The heating element as claimed in claim 1, the main body comprising at least a first region having a first lattice type and at least a second region having a second lattice type different to the first region.

6. The heating element as claimed in claim 5, wherein the first and second regions differ by any one or a combination of: a shape or geometry of the lattice; a density of the lattice; a cross-sectional area, thickness or width of strands that form the lattice; a size, shape or number of openings, voids and/or pores that extend throughout the main body.

7. The heating element as claimed in claim 5, wherein the first and second regions are positioned to extend in a lengthwise and/or widthwise direction across the heating element relative to a lengthwise direction extending between respective terminal ends.

8. The heating element as claimed in claim 1, wherein the matrix comprises at least one electrically conductive material.

9. The heating element as claimed in claim 8, wherein the electrically conductive material is selected from the group of iron-chromium-aluminium alloy, nickel-chromium alloy, copper-nickel based alloy, iron-nickel-chromium alloy, nickel-iron-chromium-aluminium alloy, ceramic material, and intermetallic material.

10. The heating element as claimed in claim 8, wherein the electrically conductive material has a resistivity within a range of from 0.1 to 1000 Ωmm.sup.2/m.

11. The heating element as claimed in claim 1, the main body comprises a surface area-to-volume ratio not greater than 95:1.

12. The heating element as claimed claim 1, wherein the lattice comprises strands having a diameter or a mean diameter which is greater than 0.05 mm.

13. The heating element as claimed in claim 1, wherein the main body is a result of an additive manufacturing process.

14. The heating element as claimed in claim 1, comprising an electrically conductive secondary body, the main body positioned adjacent the secondary body.

15. The heating element as claimed in claim 14, wherein the secondary body comprises the same material as the main body and/or is formed integrally with the main body.

16. The heating element as claimed in claim 14, wherein the secondary body is more dense, or solid, relative to the main body, having a lower degree of, or being devoid of openings, voids and/or pores that extend through the main body.

17. The heating element as claimed in claim 14, wherein the secondary body extends lengthwise with the main body between respective terminals of the heating element.

18. The heating element as claimed in claim 14, wherein the secondary body extends widthwise or orthogonal to a length of the heating element.

19. A method of manufacturing a heating element as claimed in claim 1 via an additive manufacturing process.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0055] A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which:

[0056] FIG. 1 is a cross-sectional side view of an electric heater incorporating a heating element according to a specific implementation of the present invention;

[0057] FIG. 2 illustrates schematically various different lattice configurations forming a main body of the heating element according to specific implementations;

[0058] FIG. 3 is a perspective view of a heating element for incorporation within an electric heater of the type of FIG. 1 according to one specific implementation;

[0059] FIG. 4 is a further embodiment of a heating element having a latticework extending between regions of a frame;

[0060] FIG. 5 is a perspective view of a heating element assembly comprising a main and a secondary body with the main body formed as a lattice extending externally around a solid secondary body according to a specific implementation;

[0061] FIG. 6 is a perspective view of a further embodiment of the present invention formed as an assembly having a main body formed as a latticework representing a core that is surrounded by a generally tubular secondary body;

[0062] FIGS. 7a and b illustrate schematically unit cell configurations suitable to form the latticework main body via a manufacturing process such as additive manufacturing in which FIG. 7a represents a face-centred-cubic configuration and FIG. 7b represents a body-centred-cubic configuration;

[0063] FIG. 7c illustrates schematically unit cells arranged adjacent to each other to form part of a latticework main body.

[0064] FIG. 8 is a perspective view of a heating element formed as a unitary body including a main body latticework extending between two terminal ends, with a frame part secondary body extending lengthwise with and adjacent to the latticework main body between the terminal ends according to a specific implementation;

[0065] FIG. 9 is a magnified perspective view of an end region of the heating element of FIG. 8 with the latticework main body removed for illustrative purposes.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

[0066] Referring to FIG. 1, an electric heater 10 comprises a casing in the form of a tubular sheath or housing 11 that defines an internal chamber 17. Heater 10 comprises a fluid inlet tube 21 and a fluid outlet nozzle 14 with exhaust tube 13. A fixing flange 20 is mounted to a current feed flange 19 that is in turn coupled to external electrical connections 18. A centering extension 22 that may be part of an internal heating element projects into a tube 16 to assist stabilisation of the heating assembly.

[0067] A jacket block 41 is mounted in position within chamber 17 and comprises an internal cavity 15 extending generally centrally through heater 10 aligned on a longitudinal axis 12. Elongate cavity 15 is separated from the external housing 11 via jacket block 41 formed from a suitable thermally insulating ceramic material. A heating element 23 is mounted within cavity 15.

[0068] According to the present arrangement, heating element 23 comprises a three-dimensional open-cell structure formed as a latticework.

[0069] Heating element 23 is generally elongate and comprises a first lengthwise end 23a positioned at outlet nozzle 14 and a second lengthwise end 23b positioned at or towards a terminal end of the fluid inlet tube 21. Heating element 23 is connected via suitable intermediate electrical conduits (not shown) to the external electrical connections 18. Accordingly, a voltage may be applied to heating element 23 via the conduits and electrical connections 18. In use, a fluid, such as a gas, is supplied into the electric heater 10 via inlet tube 21 to flow over, through and in contact with the element three-dimensional lattice 23 within cavity 15. As heating element 23 is formed from the electrical resistance material, the fluid is heated as it flows from tube 21 in contact with heating element 23 and exhausted from the device 10 via nozzle 14 and exhaust tube 13.

[0070] To maximise efficiency and effectiveness of thermal energy transfer between the heating element 23 and the fluid flowing within cavity 15, the present heating element 23 comprises an open three-dimensional matrix provided with openings, internal voids, pores, cavities and channels etc. extending throughout and defined by the latticework matrix of its main body. That is, the present heating element 23 may be considered to comprise a solid/rigid skeleton-like configuration. The latticework structure provides a greatly increased heating surface to volume of fluid ratio, as compared to conventional heating elements.

[0071] Referring to FIG. 1, the present heating element 23 may be formed as a regular repeating unit cell in which the openings, voids, pores comprise a size and shape that are generally uniform, i.e. of approximate equal dimensions, throughout its main body. Such a uniform regular latticework provides control of the efficiency and effectiveness of the thermal energy transfer to the flowing fluid. Additionally, such a configuration minimises any thermal gradient across the heating element both in the longitudinal axis direction and in a radial direction relative to axis 12. As will be appreciated and as illustrated in FIG. 2, the relative shapes, sizes and general dimensions of the latticework may be achieved according to various specific implementations.

[0072] The present cellular open configuration of heating element 23 may be manufactured via techniques such as additive manufacturing and computer-model based engineering manufacturing methods. Such techniques are adapted to provide a repeating unit cell configuration in which a main body 25 of heating element 23 forms a skeleton-like framework defining openings 26 and internal cavities 27.

[0073] FIG. 2 illustrates schematically various different lattice configurations forming a main body 25 of the heating element 23. More specifically, the main body 25 comprises at least a first region 60 having a first lattice type and at least a second region 62 having a second lattice type different to the first region 60.

[0074] In these embodiments, the main body 25 comprises six different regions 60-70. The first region 60 and two more regions 64, 68 have the first lattice type. The remaining three regions have differing lattice types. As already mentioned, the second region 62 has the second lattice type. A third region 66 has a third lattice type and a fourth region 70 has a fourth lattice type. In this manner, for instance the three regions 60, 64, 68 having the first lattice type may be arranged in abutment with a secondary body (not show), which is electrically heated. The first lattice type may provide favourable heat transfer from the secondary body to the main body 25, whereas the second, third, and fourth regions 62, 66, 70 may provide for 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, e.g. the highest pressure drop of the these regions may be provided by the second region 62, the third region 66 providing medium pressure drop, and the fourth region 70 providing the lowest pressure drop. According to alternative embodiments, all six regions 60-70 of the main body 25 may have different lattice types. According to further embodiments, the regions 60-70 of main body 25 may have only the first and second lattice types.

[0075] Referring to FIG. 3, heating element 23 may be formed as a hollow cylinder in which the latticework of the main body 25 defines the wall of the cylinder having openings 26 and internal voids 27. In particular, the latticework cylinder is both internally hollow as defined by the cylinder walls and the walls of the cylinder are also open via the openings 26 and internal voids 27. The walls of the cylinder contain the 3-dimensional latticework matrix structure. First and second lengthwise terminal ends 30a, 30b of heating element 23 are provided as solid discs. The terminal ends 30a, 30b may be formed integrally with the main body 25 or may be welded or attached to main body 25. First and second connections 28, 29 extend axially from each of the respective heating element terminal ends 30a, 30b. Accordingly, as described with reference to FIG. 1, a current may be applied through the heating element 23. Due to the increased surface area contact between the heating element 23 and the flowing fluid, resultant from the three-dimensional open latticework structure, the fluid is heated efficiently and effectively relative to conventional solid body heating elements. The size and shape of the internal voids, apertures and cavities as defined by the skeleton structure may be variable to achieve a desired global/total surface area and in turn effect the flow velocity and pathway of the fluid flowing through the heating element 23.

[0076] According to further specific implementations of the embodiment of FIG. 3, the main body 25 may extend throughout the cylinder as a latticework extending from an axial centre to the outer surface of the cylinder. As with the embodiment of FIG. 3, a current would then be passed through the latticework main body 25 that will be configured ‘active’ to provide the primary body through which current passes between the terminal ends. In this implementation, a fluid is preferably flowed through the main body, such as transversely to the axial extension.

[0077] According to a further implementation of the arrangement of FIG. 3, a secondary body such as a solid rod, strip or wire (not shown) of the same material as the latticework main body 25 or of a different suitable material may extend axially and internally within the latticework main body 25 between the terminal ends 30a, 30b. In such an arrangement, the secondary body provides the primary current flow pathway so as to be regarded as ‘active’ whilst the latticework main body 25 may be considered to provide structural reinforcement of the secondary body and would be regarded as ‘passive’ so as to provide heat transfer indirectly from the current flow via the secondary body. The latticework main body provides the secondary body with an increase surface area which efficiently increases the heat transfer from the secondary body.

[0078] According to specific implementations, the heating element 23 may extend continuously from an axial centre to a radially outermost surface region (radially furthest from axis 12). However, as illustrated in FIG. 3 and as discussed above, heating element 23 may be formed macroscopically as a hollow body in which the latticework structure of the main body 25 may define the wall(s) of the cylinder. According to an embodiment, a fluid may be introduced into the centre of the cylinder, and/or at the external region and/or directed to flow over the entire region of the heating element 23 including an inner bore and the outer surface. Optionally, the various embodiments based on FIG. 3 as well as other embodiments as described herein, may be configured and operational as radiating elements to radiate heat energy in response to the flow of current directly or indirectly through the main body 25.

[0079] A further embodiment of the present heating element is described referring to FIG. 4. According to the further embodiment, the heating element is formed as an assembly comprising a frame part 32 within which extends the latticework of the main body 25 having the open three-dimensional structure. The frame part 32 is a secondary body. Frame 32 comprises lengthwise extending edge struts 33 and widthwise extending cross braces 34. Frame 32 further comprises lengthwise first and second ends 31a, 31b. The lengthwise extending edge struts 33 and the cross braces 34 define openings 35 within which extend the latticework main body 25. Suitable terminal connections 28, 29 (not shown in FIG. 4) may be coupled to the first and second lengthwise ends 31a, 31b so as to allow a voltage to be applied to, and a current to be passed though, the heating element 23. According to the embodiment of FIG. 4, electrical current flows primarily through the frame 32, i.e. through the secondary body, and in particular the solid lengthwise extending supporting struts 33. However, some current will/may flow through the latticework main body 25. As such, the latticework body 25 may generate heat due to the current flow and/or be heated by thermal conduction via direct contact with the frame 32, or by radiation from the frame 32. Such an arrangement may be advantageous to minimise any risk of short circuiting or unstable current flow by operation at high voltages. That is via incorporation of frame part 32 current flow through the heating element 23 is facilitated relative to a heating element having exclusively the higher electrical resistance latticework body 25 and as such the applied voltage may be reduced.

[0080] Conventionally, a heating element may be formed by an electrically resistive cylindrical rod. According to the arrangement of FIG. 4, edge struts 33 may be seen as four quarters of such a cylindrical rod. Due to the spatial separation of the struts 33, the structural strength of the heating element is enhanced as compared to the conventional cylindrical rod. However, the cross-sectional area of the struts 33 is the same as the cylindrical rod. An overall resistance of the struts 33 is thus retained from the rod, while the structural strength of the heating element is greatly increased. At the same time the heating effect is also retained. As will be appreciated, the main body 25 of the arrangement of FIG. 4 is regarded as ‘passive’ (not the primary current pathway) whilst the struts 33 are ‘active’. In such embodiments, the main body 25 provides a further structural reinforcement of the struts 33, as well as an increased heating surface to be contacted by a fluid passing through the heating element 23.

[0081] A further embodiment is described referring to FIG. 5 in which the latticework main body is formed as a cylindrical hollow tube. A secondary body 37 extends through an internal elongate bore 36 defined by the cylindrical wall that is formed from main body 25. The secondary body 37 may for instance be a wire, a rod or a tube. Secondary body 37 comprises a non-porous, more dense, or solid material specifically adapted as a component suitable for use as a heating element. According to the embodiment of FIG. 5, secondary body 37 is positioned within bore 36 and may, or may not, be in direct contact with an internal facing surface region of main body 25. The main and secondary bodies 25, 37 may be provided in direct touching contact according to further arrangements and may also be formed integrally. In use, a voltage may be applied directly to the secondary body 37 to act as the active electrical conductor. Some electrical conduction may occur through the main body 25 although in some embodiments main body 25 is not adapted for direct current flow and is regarded as passive. In any event, as secondary body 37 is heated by the applied voltage, main body 25 may be heated via direct contact, radiation and/or conduction.

[0082] The present heating element is adaptable for use as a conducting heating element in which a fluid is directed to flow through the main body 25, acting in either active or passive modes. Additionally, the fluid may 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 radiating body to transfer heat energy for example to a neighbouring or adjacent solid body/mass. When operated as a conducting heating element, a fluid flowing in contact with main body 25 is allowed to flow through and within the main body latticework as described for efficient and effective thermal energy transfer. In the arrangement of FIG. 5, latticework main body 25 forms a sleeve or sheath to surround the electrically conducting secondary body 37 and provide structural reinforcement and an increased surface area.

[0083] According to a further embodiment illustrated in FIG. 6, latticework main body 25 may be formed as a core of a heating element assembly similar to the embodiment of FIG. 5 having secondary body 37. However, according to the embodiment of FIG. 6, secondary body 37 is provided as a hollow elongate cylinder or tubular body in which the main body 25 extends through the central internal bore 40 of secondary body 37. As described referring to FIG. 5, a voltage may be applied directly to the secondary body 37 which provides a direct or indirect heating of the main body 25 via direct contact and/or conduction. A fluid may be introduced into the central bore 40 as described referring to the electric heater of FIG. 1. In such an embodiment, the main body 25 provides a high surface-to-volume ratio relative to an ‘empty’ secondary body. The main body 25 also provides structural reinforcement of the secondary body 37. Further, the main body 25 creates a turbulent flow of fluid flowing through the latticework, which results in an increased heating efficiency.

[0084] The matrix, i.e. the main body 25 comprises at least one electrically conductive material.

[0085] The present three-dimensional latticework main body 25 may be formed from any conventional material designed for use as a heating element. Such materials are generally regarded as electrical resistance materials and resistant to high temperature creep and corrosion, oxidation and carbonisation.

[0086] Such electrically conducting material may be selected from the group of: iron-chromium-aluminium alloy, nickel-chromium alloy, copper-nickel based alloy, iron-nickel-chromium alloy, nickel-iron-chromium-aluminium alloy, ceramic material, and intermetallic material. For instance, the iron-chromium-aluminium alloy will provide for corrosion resistance, and high temperature creep strength. Also, the nickel-chromium alloy and the iron-nickel-chromium alloy will provide for corrosion resistance but also high temperature mechanical strength and good workability. Further the copper-nickel based alloy will provide for a good thermal conductivity and also good wet corrosion property. Additionally, the iron-nickel-chromium-aluminium alloy will provide an overall mechanical strength, corrosion resistance and resistance to metal dusting. The ceramic material or the intermetallic material will provide for stability at high temperature above 1300° C.

[0087] The present open-cell, three-dimensional, construction provides a structure that is further advantageous to enhance the physical and mechanical strength of the heating element, and/or to increase the heating area of the heating element. Due to the light-weight and structurally strong latticework main body 25, the present heating element may be formed according to an unlimited number of high strength structures having one or a plurality of repeating cell geometries to define an ordered latticework. In particular, the present open-cell, 3-dimensional structure may comprise regions that differ in repeating cell structure that, in turn, provide regions offering different structural support to a secondary body and/or provide different current flow pathways of different resistance and hence magnitude of energy transfer via conduction and/or radiation. In particular, the flexural strength of the heating element may be enhanced relative to conventional solid body heating elements. Additionally, the open structure may facilitate attachment of positional stabilisation components, rods, braces or flanges to mount and/or secure heating element 23 in position within a heating device of the type of FIG. 1. According to further specific implementations, the latticework structure may be designed so as to comprise positional support projections formed integrally as part of the main body 25 and extending radially outward from axis 12 towards and in contact with jacket block 41 and/or an outer housing 11. Such projections may be attached to suitable mounting locations so as to positionally stabilise the heating element 23 in position.

[0088] The three-dimensional open structure may be designed so as to achieve the desired surface area contact with the flowing fluid volume. Such surface-to-volume may be defined based on a unit cell (see below) of the latticework main body 25 as the ratio of the total surface area in the unit cell versus the total volume of solid parts of the unit cell, surface area-to volume ratio. That is, the surface area of the strands 45 and nodes of the latticework in relation to the volume of the strands and nodes. According to one embodiment, the surface area-to-volume ratio is not greater than 95:1, such as 1:1 to 95:1.

[0089] Such arrangements of heating element 23 may be provided as a single main body 25 having a single repeating unit cell or regions of different unit cells and/or as an assembly having a main body 25 in combination with a secondary body 37. In particular, heating element 23 may be formed as a main body 25 being a continuous skeleton-like framework as described in FIGS. 2 and 3, a framed structure/assembly as illustrated and described referring to FIG. 4 or a multicomponent assembly as described referring to FIGS. 5 and 6.

[0090] Referring to FIGS. 7a and b, main body 25 may be regarded as being formed from repeating unit cells with each cell formed from solid strands 45 that are joined or branched to define the 3-dimensional matrix. The strands 45 joined at nodes to form the 3-dimensional matrix. Main body 25 may comprise a single type of unit cell repeating over the entire volume of the latticework or may comprise a plurality of different unit cell geometries to form distinct regions that differ in their surface area-to-volume ratio and hence the size, shape and multiplicity of the internal cavities/pores 27, such as e.g. the first and second regions 60, 62 discussed above with reference to FIG. 2. According to the unit cell configuration of FIG. 7a, the main body 25 may be formed for example of face-centred-cubic (fcc) unit cells or referring to FIG. 7b, may be formed of body-centred-cubic (bcc) cells, or a combination thereof. The unit cell may have a diameter, or width of at least 0.1 mm. The strand 45 may have a diameter of at least 0.05 mm.

[0091] According to some embodiments, the lattice may comprise strands 45 having a diameter or a mean diameter which is greater than 0.05 mm, such as 0.05 to 4 mm. The diameter and mean diameter of a strand 45 is measured perpendicularly to a longitudinal extension of a strand 45. The mean diameter is the average diameter in case the strand 45 does not have a circular cross section.

[0092] FIG. 7c illustrates a number of unit cells 72 of a portion of a main body 25 of a heating element. Each unit cell 72 is schematically shown as a cube and may be of one of the kinds discussed in connection with FIGS. 7a and b. However, the unit cells 72 are not limited to the shown embodiments but may have any suitable internal structure of strands and any suitable other outer shape, such as e.g. a tetrahedron shape.

[0093] The unit cells 72 are arranged next to each other in 3 dimensions, i.e. strands of adjacent unit cells 72 share nodes. More specifically, at corners of each unit cell 72, strands from adjacent unit cells 72 are connected to each other and thus, form nodes. Since each unit cell 72, except at outer surfaces of the main body 25, is surrounded by other unit cells 72, the unit cells are positioned next to each other in three dimensions. Accordingly, the main body 25 comprises 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, wherein the first, second, and third directions d1, d2, d3 are arranged at an angle to each other. For instance, if the unit cells 72 have cubic shape, as illustrated, the three directions d1, d2, d3 are orthogonal, if the unit cells 72 have tetrahedron shape, the three directions extend at an angle of 120 degrees to each other.

[0094] A further embodiment of the heating element is described referring to FIG. 8. According to this embodiment, the latticework main body 25 extends axially between two terminal ends 46a, 46b. Each terminal end 46a, 46b is formed as a solid, secondary body from the same material as that forming the latticework 25. A frame part 47 comprised in the secondary body extends axially between terminal ends 46a, 46b immediately adjacent to latticework main body 25. The frame part 47, terminal ends 46a, 46b and main body 25 are formed integrally preferably via a process such as additive manufacturing. Frame part 47 is provided with slots 48 to alter the electrical current flow characteristics and in particular the electrical resistance of the frame part 47. In such a configuration, the main body 25 provides structural support to the frame part 47 with the main body 25 being considered passive and the frame part 47 being considered active as the primary current flow pathway. Main body 25 accordingly, provides heat energy transfer, which heat is provided indirectly from the current flow passing primarily through the active heating element, i.e. frame part 47.

[0095] FIG. 9 is a magnified end view of the heating element of FIG. 8 with the latticework main body removed for illustrative purposes. As shown, the terminal ends 46a are formed from relatively short plates positioned orthogonal to the elongate heating element, i.e. the main body 25, and to active current flow frame part 47). The terminal ends 46a, 46b comprise a much larger cross-sectional area than the frame part 47 or the main body 25, in a plane perpendicular to the direction of current flow between terminal ends 46a, 46b. Accordingly, the larger cross-sectional size of the terminal ends 46a, 46b provides that they do not radiate heat. The cross-sectional area of the latticework main body 25 is relatively small such that only negligible current would pass through the lattice of main body 25. Accordingly, the lattice main body 25 is provided as the passive component. As illustrated in FIG. 9, the cross-sectional area of the frame part 47 is smaller than the terminal ends 46a, 46b to provide higher electrical resistivity and in turn a greater heating effect. As illustrated in the example of FIGS. 8 and 9, the frame part 47 via the slots 48 comprises a lengthwise extending meandering pathway between terminal ends 46a, 46b.

[0096] As will be appreciated, frame part 47 comprises wider current flow path regions 49 relative to narrower flow path regions 50. Accordingly, the electrical resistivity in the narrow regions 50 will be greater to provide increased heat energy transfer. As such, the active frame part 47 is provided with regions 49, 50 offering differential heating effects along its length (between terminal ends 46a, 46b) which may be advantageous to provide differential heating zones within a heating device. Such an arrangement may be used for heating irregular solid objects, for example to obtain uniform heating of an irregular object by differential heating of the different zones/regions of the irregular object.

[0097] According to specific implementations, the terminal ends 46a, 46b may also be provided with different cross-sectional areas both in the widthwise direction and lengthwise direction. For example, the cross-sectional area in the plane perpendicular to the current flow direction, i.e. between ends 46a, 46b, may be tapered so as to decrease in a direction outward from latticework main body 25 and towards an outer casing of the heating device.

[0098] With reference to the summary of the invention and the detailed description of preferred embodiments above, an itemised list related to the present invention is presented: [0099] Item 1. A heating element in a heating device, assembly or apparatus, the heating element comprising: [0100] a main body; [0101] the main body being a three-dimensional matrix having an open structure defining openings, voids and/or pores extending through the main body. [0102] Item 2. The heating element as per item 1, wherein the matrix is provided as a lattice having a repeating unit cell to define a main body having a pattern. [0103] Item 3. The heating element as per item 2, wherein the pattern is uniform and the main body comprises openings, voids and/or pores of a size and shape that are generally homogenous throughout the main body. [0104] Item 4. The heating element as per item 1 or 2, the main body comprising at least a first region having a first lattice type and at least a second region having a second lattice type different to the first region. [0105] Item 5. The heating element as per item 4 wherein the first and second regions differ by any one or a combination of: [0106] a shape or geometry of the lattice; [0107] a density of the lattice; [0108] a cross-sectional area, thickness or width of strands that form the lattice; [0109] a size, shape or number of openings, voids and/or pores that extend throughout the main body. [0110] Item 6. The heating element as per item 4 or 5 wherein the first and second regions are positioned to extend in a lengthwise and/or widthwise direction across the heating element relative to a lengthwise direction extending between respective terminal ends. [0111] Item 7. The heating element as per any preceding item, wherein the matrix comprises a corrugated, skeletal or caged framework or structure. [0112] Item 8. The heating element as per any preceding item, wherein the matrix comprises at least one electrically conductive material. [0113] Item 9. The heating element as per item 6, wherein the main body extends radially from a centre to an outer surface of the heating element. [0114] Item 10. The heating element as per any preceding item comprising an electrically conductive secondary body, the main body positioned adjacent the secondary body. [0115] Item 11. The heating element as per item 10, wherein the secondary body comprises the same material as the main body and/or is formed integrally with the main body. [0116] Item 12. The heating element as per item 10 or 11, wherein the secondary body is more dense, or solid, relative to the main body, having a lower degree of, or being devoid of openings, voids and/or pores that extend through the main body. [0117] Item 13. The heating element as per any one of items 10 to 12, wherein the secondary body extends lengthwise with the main body between respective terminals of the heating element. [0118] Item 14. The heating element as per any one of items 10 to 13, wherein the secondary body extends widthwise or orthogonal to a length of the heating element. [0119] Item 15. The heating element as per any one of items 10 to 14, wherein the secondary body comprises a cross-sectional area, width or thickness that is uniform or is variable. [0120] Item 16. A method of manufacturing a heating element as per any preceding item via an additive manufacturing process.