heating element

Abstract

A heating element and heating assembly are disclosed, which, as part of a heating device, heat a fluid. The heating element is formed of a high-resistivity material, such as a FeCrAl-based material. The heating device includes a heating block having a high heating surface area to volume ratio (HTVR) to achieve high heating density under low surface load.

Description

Technical Field

[0001] This disclosure relates to an electric heater for heating a fluid flow, and particularly, but not exclusively, to a heating element that can be mounted within an electric heater formed of a high-resistivity conductive material. Background Technology

[0002] Electric heaters used to heat gases to high temperatures typically comprise a ceramic block or jacket with longitudinally extending orifices through which a relatively thin heating wire extends to heat the gas as it flows through the ceramic block. The effectiveness and efficiency of converting electrical energy into heat (via the heating wire) depends, for example, on the applied available voltage, the resistance of the heating wire, the maximum operating temperature achievable by the heating wire, fluid flow resistance, and the surface area of ​​the heating element in contact with the flowing fluid. Typically, the highest gas temperature achievable by conventional electric process heaters is around 700°C to 900°C.

[0003] Different types of electric heaters include one or more heating channels that form an element for heating a fluid. WO 2009 / 071590, US 2007 / 189741, EP 2784049, US 2013 / 287378, and DE10012675 disclose various such heating systems that include ceramic resistance heating elements forming one or more channels through which the fluid to be heated flows.

[0004] US 2007 / 189741 and EP 2784049 each disclose heating elements comprising multiple channels arranged for a fluid to be heated to flow through them in parallel. Current for heating these heating elements is applied in parallel across these channels. Summary of the Invention

[0005] One object of this disclosure is to provide a heating element, heating assembly, and / or electric heater configured to enhance heat transfer between the device and a fluid by having a high heating surface area per unit volume. Another specific object is to provide a heating element arrangement having enhanced structural and mechanical properties, particularly flexural strength, to withstand vibration and movement relative to other components of the heating assembly / device, and the heating arrangement being operable in any orientation. Yet another specific object is to provide a heating element and an electric heater that are not prone to "short circuits" due to undesirable movement of the conductive heating element and are not prone to contact with themselves or other conductive components within the heating device.

[0006] These objectives are achieved via a heating element and an electric heating device in which the heating block is formed of a conductive material, thus eliminating the need for additional heating filaments extending within the fluid flow orifices of the heating block (according to existing arrangements). Therefore, the heating block formed of conductive material represents a stable structure and is suitable for fluid flow and direct / effective heating via internal orifices or channels. Thus, the internal hollow material structure can withstand the stresses and general physical requirements encountered in use, caused by large pressure differentials, gravity, and cyclic heating gradients. In particular, this arrangement provides a high-strength heating assembly, thus eliminating the need for additional filament-type heating elements and ceramic channel-like structures. Thus, this arrangement is more compact and lighter than conventional arrangements and is characterized by a higher heating surface area per unit volume compared to conventional heating devices.

[0007] This heating element is suitable as an active heating element via a conductive material forming / defining a heating block, which in turn defines a) a path through which current flows exclusively, primarily, or preferentially relative to any other conductive body within the electric heater, and b) fulfills the function of defining a structure for fluid flow. However, this heating block can operate in conjunction with additional structural elements such as ceramic components, sheaths, stabilizing bars, or spacers, which provide auxiliary and passive heating elements relative to this heating element. These auxiliary and passive heating elements are non-conductive to allow for extended operating conditions.

[0008] Unless otherwise specified, the term “block” as used in the context of a heating block herein is not limited to a specific cross-sectional geometry, but may also refer to any relevant structural shape.

[0009] This heating element further facilitates freedom of design choice regarding the shape and construction of the heating block, which can also be referred to as a heating structure. For example, this heating element can be manufactured using additive manufacturing (such as 3D printing), in which the conductive heating block is formed as a single entity or as an assembly / set of multiple individual heating elements printed by additive manufacturing, which are electrically coupled and mechanically assembled to form the heating block. Advantageously, the heating element and / or heating block and / or heating structure can be formed by additive manufacturing printing along with the integral manufacturing of additional features and components, such as terminals for connection to a current supply, stabilizing disks, rods, blocks, struts, supports, flanges, and / or fluid flow guiding fins / surface area extensions and fluid flow disturbances for disrupting fluid flow through holes or channels. Alternatively, additional features and components, such as terminals for connection to a current supply, stabilizing disks, rods, blocks, struts, and / or supports, can be manufactured separately and assembled with the heating element and / or heating block and / or heating structure.

[0010] According to a first aspect of this disclosure, an electric heater for heating a fluid flow is provided, the electric heater comprising:

[0011] At least one heating element, the at least one heating element defining an axially elongated heating block having a first longitudinal end and a second longitudinal end;

[0012] Multiple longitudinal holes or channels extend internally through the axially elongated heating block and open at each corresponding first and second longitudinal end;

[0013] The at least one heating element is composed of a conductive material for active resistance heating or more than one conductive material for active resistance heating; and

[0014] A first terminal and a second terminal are disposed at the heating block for connection to a current supply. The conductive material, or more than one conductive material, is selected from the group consisting of: iron-chromium-aluminum alloys; nickel-chromium alloys, copper-nickel-based alloys, or iron-nickel-chromium alloys, and intermetallic compounds.

[0015] Therefore, high power density can be achieved in the electric heater, and the additional resistance heating of the heating element will allow the heating block to be heated to temperatures up to 1300 degrees Celsius. Thus, the fluid flow through the electric heater can be heated to high temperatures in a single step, such as from ambient temperature (e.g., 20°C) to a range of 1000 to 1250°C. Furthermore, the current supply to the heating block can be provided by a common line voltage.

[0016] The at least one heating element will guide the fluid flow and heat the fluid flow as it passes through the electric heater.

[0017] According to an embodiment, the heating element can be manufactured using additive manufacturing, in which a conductive heating block is formed as a single body or as an assembly / set of multiple individual heating elements printed by additive manufacturing. These heating elements are electrically coupled and mechanically assembled to form the heating block. This allows for the efficient manufacture of the heating element. Specifically, the materials that can be used are selected from one or more of the group consisting of: iron-chromium-aluminum alloys, nickel-chromium alloys, copper-nickel-based alloys, or iron-nickel-chromium alloys, and intermetallic compounds. These materials are those that may be difficult or impossible to form using conventional manufacturing methods such as machining. Furthermore, complex geometries (e.g., within channels) can be achieved using additive manufacturing.

[0018] According to one embodiment, the heating surface area to volume ratio (HTVR) of the heating block as defined above or below is defined by equation (1):

[0019] Σ(A) / V≥1m -1 (1)

[0020] Wherein, Σ(A) is the sum of the heating surface areas of the holes or channels extending at least between the first longitudinal end and the second longitudinal end, and V is the total envelope volume of the conductive material, wherein the total envelope volume of the conductive material is the sum of the volumes of all holes and channels and the conductive material.

[0021] According to one embodiment, at least 80% of the electric heater as defined above or below may also satisfy condition (2):

[0022] [Wetting perimeter or surrounding area] / [Envelope cross-sectional area] ≥ 1m -1 (2)

[0023] Wherein, the wetting perimeter or circumference is the total length of all edges of the heating block that are in direct contact with the fluid flow at a given cross section; and wherein, the envelope cross-sectional area is the sum of the cross-sectional areas of the heating block or heating structure and the holes or channels in the same longitudinal direction.

[0024] According to the embodiments, for the heating block as defined above or below, HTVR and / or condition (2) are between 1.0 and 4.0 m. -1 1.0 to 3.0m -1 Or 1.0 to 2.5m -1 Within the range.

[0025] According to this disclosure, the at least one heating element is made of a conductive material for active resistance heating, but the at least one heating element may also be made of more than one conductive material for active resistance heating. The conductive material may have a homogeneous composition. As described above, the conductive material for active resistance heating is selected from the group consisting of: iron-chromium-aluminum (FeCrAl) alloys; nickel-chromium (NiCr) alloys, iron-nickel-chromium (NiCrFe) alloys, copper-nickel (CuNi) based alloys, and intermetallic compounds. The intermetallic compounds should also generate heat. Therefore, the at least one heating element may be made of one of the above materials or a combination of the above materials. Furthermore, the heating structure may include heating elements made of different materials. If additive manufacturing is used as the production method, the above materials are provided in the form of powder or wire.

[0026] According to an embodiment, the surface load of the heating element can be 1 to 3 W / cm² under atmospheric conditions. 2Within a certain range, the outlet temperature of the fluid flow can be between 1000 and 1250°C. This allows for achieving high outlet temperatures while providing a relatively low surface load on the heating element during operation. Compared to conventional electric heaters using thinner, high-resistance heating wires, this provides a longer service life.

[0027] Optionally, the heater may include multiple heating elements assembled together as a heating block, each heating element comprising the material and having a hole or channel that partially defines the hole or channel of the heating block. Specifically, each heating element may include only one hole or channel extending therethrough.

[0028] According to one embodiment, the heater further includes a plurality of stabilizing bars or spacers positioned between the heating elements and abutting against them along their respective lengths. The heating elements are spaced apart from each other and indirectly contact each other via the bars or spacers. With this arrangement, the heater advantageously provides both the inward-facing and outward-facing surfaces of the heating block as effective heating surfaces that contact the fluid (such as gas) flowing between the respective longitudinal ends of the heating block. The heating block may include an insulating material positioned adjacent to the outward-facing surface. Such insulating material may be configured to directly contact the outward-facing surface or may be spaced apart from the outer surface such that the outer surface is exposed to the flow of the fluid / gas to be heated, thereby increasing the total effective heating surface area within the device.

[0029] Therefore, according to an embodiment comprising multiple heating elements assembled together, the multiple longitudinal holes or channels extending internally through the axially elongated heating block may include channels formed in the gap region between the outward-facing surfaces of adjacent heating elements. In this way, fluid flow can flow not only through the interior of the multiple heating elements but also along the outer surfaces of the heating elements. Thus, the heating block can provide a high HTVR.

[0030] According to an embodiment, these stabilizing bars or spacers are sized to create the gap region between the heating elements. This allows for the convenient provision of the gap region while simultaneously providing stabilization for the heating elements. For example, these bars or spacers may only abut against the outward-facing surfaces of the heating elements.

[0031] According to embodiments, at least one of these stabilizing rods or spacers can be arranged abutting three or four of the heating elements. In this way, one rod or spacer can support three or four heating elements while also at least contributing to providing a gap area between the three or four heating elements. For example, if each heating element has a substantially square cross-section, the rod or spacer can be arranged abutting the four corner portions of each of the four adjacent heating elements. Corresponding positions of the rods or spacers associated with the four heating elements can be provided for heating elements having circular cross-sections. Alternatively, the rod or spacer can abut against three heating elements having circular cross-sections.

[0032] According to an embodiment, each stabilizing bar or spacer can be non-conductive. This ensures that the applied current will not be short-circuited through any bar or spacer, but will flow only through the heating element. For example, these bars or spacers can be made of a non-conductive ceramic material. Therefore, these bars or spacers can withstand the high temperatures within the electric heater.

[0033] According to an embodiment, the heating elements among the plurality of heating elements can be electrically connected in series. This allows for a suitable total resistance of the heating block for an applicable voltage. Furthermore, such an applicable voltage can be one of the common line voltages, such as 230, 400, 480, or 690V. This simplifies the connection of the electric heater to the power grid. In particular, this allows for the use of materials selected from the group consisting of: iron-chromium-aluminum alloys, nickel-chromium alloys, copper-nickel-based alloys, or iron-nickel-chromium alloys, as well as intermetallic compounds.

[0034] Alternatively, the heater may include a single heating element that defines a heating block having multiple holes or channels. In such a configuration, the inward-facing surfaces defining the holes or channels primarily provide an effective heating surface for the fluid (gas). According to some embodiments, this effective heating surface is the sum of the surface areas of the inward-facing surfaces of the holes or channels.

[0035] This heating block is formed of a high-resistivity material and is the main or sole component. Current flows through this component by applying voltage to its terminals. This heating block or structure serves the primary purposes of generating and transferring heat and guiding fluid (gas) flow.

[0036] Alternatively, the heater may include fins or protrusions that project radially into the holes or channels. These fins or protrusions help to increase the effective surface area for heating gas / fluid in the region between the first and second longitudinal ends of the heating block.

[0037] Optionally, the heating block may include a disturbance portion protruding radially into the hole or channel to disrupt the fluid flow through it. This disturbance portion may be formed of nodes, protrusions, flanges, ribs, ridges, crossbars or beams, meshes, etc., which are positioned within the hole or channel and restrict fluid flow from the original longitudinal flow path. This disturbance portion can simultaneously increase the surface area of ​​the heating element and the fluid mixing characteristics in the boundary layer, and thus correspondingly increase the heat transfer rate.

[0038] Alternatively, these holes or channels are defined by the walls of the heating block, which include any one or a combination of holes, notches, grooves, or pawls that reduce the material volume at the wall. This provides a construction that increases the HTVR, surface load, and heating density of this heater.

[0039] Optionally, in a plane perpendicular to the longitudinal axis of the heating block, the cross-sectional area of ​​these walls is non-uniform between the first and second ends and / or decreases between the first and second ends. This configuration can facilitate the provision of a longitudinal differential or heating gradient at the heating block. In particular, the heating block can be provided with a tube wall that is relatively thinner towards the first, cooler end of the heating block relative to the relatively thick downstream end where the gas / fluid is heated and discharged from the device, to maximize / optimize HTVR and surface load (providing a relatively cool inlet gas flow to this region of the heating block). Thus, HTVR, surface load, and heating density can vary longitudinally between the first and second ends of the heating block.

[0040] According to one embodiment, the at least one heating element is axially elongated. In this configuration, the length of the heating element in the fluid flow direction is greater than the width perpendicular to the fluid flow alignment.

[0041] According to this disclosure, the heating device, and particularly the internal heating assembly, does not have any heating elements based on coiled wire or longitudinally extending wire within holes or channels of the heating block. Specifically, the current providing the heating effect is supplied solely through the walls of the heating block, which is formed of a high-resistivity material.

[0042] According to one embodiment, the heater further includes: a housing positioned at least partially around the heating block; and at least one mounting base extending radially from the housing to contact the heating block and secure the heating block within the heater. According to another embodiment, the heater may further include thermal insulation material radially positioned between the housing and the heating block.

[0043] Optionally, the first and second terminals are positioned at at least one of the first and second ends of the at least one heating element, or positioned toward at least one of the first and second ends of the at least one heating element. According to one embodiment, these terminals are integrally formed with the at least one heating element and / or the heating block. Optionally, these terminals are not integrally formed with the at least one heating element and / or the heating block, and are chemically or mechanically attached to the heating assembly.

[0044] According to another aspect of this disclosure, a modular electric heater assembly is provided, comprising a plurality of heating blocks as described and claimed herein, the plurality of heating blocks being electrically connected in series and / or in parallel. Attached Figure Description

[0045] Specific embodiments of this disclosure will now be described by way of example only and with reference to the accompanying drawings, in which:

[0046] Figure 1 This is a side sectional view of an electric heater including a heating element according to a specific embodiment of the present disclosure;

[0047] Figure 2 It is formed Figure 1 A three-dimensional view of a heating component of an electric heater;

[0048] Figure 3a yes Figure 2 An enlarged view of one end of the heating component / heating block;

[0049] Figure 3b Through formation Figure 2 A cross-sectional view of the heating element AA of the heating block;

[0050] Figure 4 This is a perspective view of the end of a heating block according to another specific embodiment of the present disclosure;

[0051] Figure 5 This is a cross-sectional view of a heating element having inwardly protruding fins according to another embodiment of the present disclosure;

[0052] Figure 6 This is a partial cross-sectional perspective view of a heating element according to another specific embodiment, which has a portion with reduced wall thickness according to the specific embodiment;

[0053] Figure 7 This is a partial cross-sectional perspective view of a heating element according to another specific embodiment, the heating element including an internal disturbance portion to disrupt the fluid flow through the heating element;

[0054] Figure 8This is a perspective view of another embodiment of the present disclosure, wherein the heating block is formed as a single body via a single heating element. Detailed Implementation

[0055] Reference Figure 1 The electric heater 10 includes a housing in the form of a tubular sheath or outer shell 11, which defines an internal chamber 17. The heater 10 includes a gas / fluid inlet pipe 21 and a gas outlet nozzle 14 with an exhaust pipe 13. A retaining flange 20 is mounted to a power supply flange 19, which is coupled to an external electrical connection 18. Thermal insulation material 37 is internally mounted within the chamber 17, abutting against or facing the inward-facing surface of the outer shell 11. The insulation layer 37 further defines an inner cavity 15 within the chamber 17 to receive a heating block, generally indicated by reference numeral 23. The heating block 23 is mounted within a pair of hollow disks 40 extending radially between the outer surface of the heating block 23 and the inner surface of the outer shell 11.

[0056] The heating block 23 is formed of a plurality of elongated heating elements 26, which are assembled together to form a single heating assembly. An assembly of generally linear heating elements 26 defines a generally elongated heating block 23 having a first longitudinal end 23a and a second longitudinal end 23b. The heating block 23 further includes a first terminal 22a and a second terminal 22b disposed at / connected to the second end 23b for connection to an external electrical connection 18 (via conduit 16) for supplying current to the heating elements 26 and thus to the heating block 23.

[0057] Reference Figure 1 , Figure 2 , Figure 3a and Figure 3b Each heating element 26 is formed as an internally hollow elongated tube, in which an inner hole or channel 25 is defined by an inwardly facing surface 28 of a wall 32, which represents the body of each heating element 26. The inner hole or channel 25 forms a unique hole or channel 25 through each heating element 26. The wall 32 further includes an outwardly facing surface 29 and is defined between the respective inwardly facing surface 28 and the outwardly facing surface 29. Each heating element 26 and thus the heating block 23 is elongated, wherein the heating block 23 is centered on the longitudinal axis 12, and each respective heating element 26 is centered on its own respective longitudinal axis 31.

[0058] The heating element 26 is preferably formed of a high-resistivity material such as iron-chromium-aluminum (FeCrAl). Examples of materials are those marketed under trade names. APM or The alloys sold by APMT, or if additive manufacturing is used as the manufacturing method, are exemplified by trade name. The powders sold by PM100, all of which are available from Kanthal AG in Sweden, are incorporated herein by reference in their chemical composition and physical and mechanical properties. Depending on the fluid composition, other resistive materials such as nickel-based or molybdenum-based alloys may also be preferred.

[0059] With the heating element 26 connected to the external electrical connection 18 via terminals 22a, 22b, voltage / current can be applied to block 23. Thus, gas / fluid can be heated as it flows from pipe 21 into chamber 17 and through the block. Specifically, the gas is adapted to flow through the inner bore 25 to exit from device 10 via nozzle 14 and exhaust pipe 13. According to a particular embodiment, block 23 (via the wall 32 of each heating element 26) is directly heated by the applied current to provide direct and effective heating (to the gas flow) within the bore 25 and gap region 38. Therefore, this heating assembly eliminates the need for internally mounted heating wires or conduits extending within the bore 25 (common in conventional fluid electric heaters). This arrangement facilitates maximizing the efficiency and effectiveness of heat transfer between the heating element 26 and the fluid flowing within the inner chamber 17. In particular, this arrangement provides a large heating surface area to volume ratio (HTVR), which can be defined as the effective surface area (wetting surface area) of the heating material divided by the envelope volume of the heating element 32.

[0060] Within block 23, heating elements 26 can be connected in series. That is, the voltage applied to block 23 via terminals 22a and 22b causes current to flow through the heating elements 26 in series. For this purpose, the heating elements 26 are connected via... Figure 1 Connect them one after another to the conductive elements not shown in Figure 3c. (Refer to...) Figure 4 Examples and discussion of conductive element 41.

[0061] According to a particular embodiment, the insulating material 24 may be positioned to encapsulate or at least partially surround the outward-facing surface of the heating block 23 (as defined by the region of the outward-facing surface 29 of each heating element 26). In such an arrangement, these covered regions of the outward-facing surface 29 are inactive for the flow of heating fluid, such that the inward-facing surface 28 can be the primary effective heating surface. However, other unhidden / blocked regions of the outward-facing surface 29 may be considered active when gas flows between adjacent heating elements 26.

[0062] In particular, and referring to Figure 3a and Figure 3bHeating elements 26 are positioned and held as a single unit via intermediate extension rods 27 that extend between and abut against the edge / surface regions of adjacent heating elements 26. The rods 27 are sized to create a gap region 38 via the available effective heating surface defined by the inner surface 28 and the outer surface 29, which effectively increases the HTVR. The rods 27 may extend over the entire axial length of the heating elements 26, or only over a portion of their total length. Therefore, the rods 27 can be formed as relatively short bushings or spacers to further maximize the available effective heating surface area, which in turn improves the HTVR.

[0063] Therefore, the HTVR of heating block 23 can be defined as the sum of the effective / exposed heating surfaces (including both the inward-facing surface 28 and the outward-facing surface 29) divided by the total envelope volume of the forming / creating walls 32 of the heating block. Thus, this heating assembly (heating block 23) includes a high heating surface area per unit volume, i.e., a high heating density. Therefore, such an arrangement provides a heating density with a W / m²... 2 The heating arrangement described features a relatively low surface load. Advantageously, in addition to the higher outlet temperatures at exhaust zones 13 and 14, the heating arrangement / device of the present invention is also suitable for a relatively long service life. The heating element 26 is manufactured under the trade name... APM or APMT sells high-resistivity materials formed in the case of materials used in manufacturing, or if additive manufacturing is used as the manufacturing method, the materials can be sold under the trade name. The PM100 powder (all of which are available from Kanthal AG in Sweden) can reach a maximum heating temperature of around 1300°C in air. For atmospheric conditions, the surface load of the heating element can range from 1 to 3 W / cm². 2 Within this range, for systems operating at 100 bar pressure, the surface load of the heating element can reach up to 30 W / cm². 2 The electric heater according to this disclosure can include an HTVR (1 / m) of 1 to 2.5 via the construction described herein. This contrasts with conventional process electric heaters, in which a thinner, high-resistance heating wire is mounted and screwed through the inner hole of a ceramic heating block. This conventional arrangement typically achieves a maximum heating temperature of 1100°C in air, where the element surface load is 3 to 20 W / cm². 2 HTVR is 0.2 to 0.5.

[0064] Figure 4 It shows Figures 1 to 3b Another embodiment of the heating block 23, in which, relative to Figure 3bThe rectangular cross-sectional profile shown is such that each heating element 26 is formed as a tube with a circular cross-sectional profile. As will be noted, the cross-sectional profile of AA is defined in a plane perpendicular to the longitudinal axes 12, 31.

[0065] Furthermore, the heating elements 26 are electrically connected in series. For this purpose, an appropriate number of conductive elements 41 are provided, each conductive element connecting two heating elements 26, such that the heating elements 26 are connected in series throughout the heating block.

[0066] Therefore, such a conductive element 41 can connect one end portion of the first heating element 26 to the end portion of the second heating element 26. The opposite end portion of the second heating element 26 is connected to the end portion of the third heating element, and thus connected to the entire heating block 23. The first and last heating elements 26 in this series of interconnected heating elements 26 are provided with terminals 22a, 22b for each.

[0067] The conductive element 41 can be manufactured together with the heating element 26 during the manufacturing of the heating block 23 using an additive manufacturing process. Thus, the entire heating block 23 can be manufactured in a single manufacturing step. If stabilizing bars 27 are used, these bars can be inserted after the manufacturing of the heating block 23. Alternatively, see also... Figure 2 Terminals 22a and 22b can also be manufactured during additive manufacturing.

[0068] Alternatively, the conductive element 41 can be manufactured separately from the heating element 26 and can be connected to the heating element 26 in a separate manufacturing step.

[0069] Furthermore, in this embodiment of the heating block, the heating elements 26 can be positioned and held as a single unit via an intermediate extension rod (not shown) that extends between and abuts the edge / surface areas of adjacent heating elements 26. In this embodiment, each rod will abut against three adjacent heating elements 26. Again, a gap area will be maintained / formed between the individual heating elements.

[0070] Figure 5 Another embodiment of this disclosure is shown, in which each heating element 26 includes radially inwardly projecting fins 30. Each fin 30 extends from the wall 32 toward the axial center 31 of the inner bore 25. The fins 30 facilitate a further increase in effective surface area at a constant fluid outlet temperature, thereby increasing the HTVR, heating density, and correspondingly the available output operating temperature of the heated gas from the exhaust pipes 13, 14, or smaller heater feature sizes.

[0071] Reference Figure 6HTVR can be further improved by reducing the volume of the high-resistivity material forming the wall 32. Specifically, the thickness of the area of ​​wall 32 can be reduced via recesses 33 or channels 34 in the outer surface 29 of each or at least some of the heating elements 26. Additionally or alternatively, wall 32 may include through-holes 39 extending between the outward-facing surface 29 and the inward-facing surface 28 to further reduce the mass of the conductive material and thus increase HTVR. The above features also allow for an artificial increase in the total resistance of the entire flow heater, which would make the flow heater 10 of the present invention even more suitable for direct connection to line voltage.

[0072] Reference Figure 7 According to another alternative embodiment, at least some of the heating elements 26 may be provided with disturbance portions 35, 36, which are in the form of obstacles protruding radially inward from the inward-facing surface 28 facing the wall. Such disturbance portions 35, 36 are positioned in the flow path of the orifice 25 and are effectively used to disrupt the gas flow and thereby generate eddies, thereby enhancing the mixing effect in the boundary layer and thus increasing heat transfer to the fluid. For the above reasons, such disturbance portions can further increase the effective heating surface area.

[0073] Reference Figure 8 Another embodiment of the heating block 23 is formed as a single monolithic body, in which a single heating element 26 includes a plurality of inner holes 25 extending between a first longitudinal end 23a and a second longitudinal end 23b (see reference). Figure 1 (As shown). Electrical terminals 22a and 22b (refer to...) Figure 1 (As shown) is connected to or positioned at or toward one or both longitudinal ends 23a, 23b for electrical connection to an external current supply. In this alternative embodiment, the heating block 23 is also formed of a high-resistivity material such as FeCrAl alloy. Figure 8 All other features and functions of the heating block 23 are consistent with those of the heating block 23. Figures 1 to 7 As described in the embodiments, in Figures 1 to 7 In one embodiment, the gas is adapted to flow within the orifice 25 and be heated by passing an electric current through a resistive material forming the heating block wall 32.

[0074] The heating block 23 / heating element 26 can be easily manufactured using conventional techniques such as 3D printing and other computer-based modeling engineering methods. This technology enables the production of products like... in a single manufacturing process. Figures 5 to 8 The heating elements shown have complex shapes and structures, including fins 30, grooves and channels 33, 34, holes 39, and disturbance portions 35, 36.

[0075] This embodiment is described with reference to high-resistivity materials such as FeCrAl-based alloys. However, these embodiments can be formed from any suitable conductive material, including NiCr-based alloys, NiCrFe-based alloys, CuNi-based alloys, or Mo-based alloys. All configurations can be formed using powder-based materials and processes.

[0076] Electrical terminals 22a and 22b may be integrally formed with the heating element 26 and / or the heating block 23. According to another embodiment, terminals 22a and 22b may be attached or connected to corresponding areas of the heating block 23 via chemical or mechanical attachment. Preferably, terminals 22a and 22b are integrally formed at one longitudinal end of the heating block 23.

Claims

1. An electric heater (10) for heating a fluid flow, the electric heater comprising: At least one heating element (26) defines an axially elongated heating block (23) having a first longitudinal end (23a) and a second longitudinal end (23b); Multiple longitudinal holes or channels (25) extend internally through the axially elongated heating block (23) and open at each corresponding first longitudinal end (23a) and second longitudinal end (23b); The at least one heating element (26) is composed of a conductive material for active resistance heating or more than one type of conductive material for active resistance heating; and A first terminal (22a) and a second terminal (22b) are disposed at the heating block (23) for connection to a current supply; wherein, The conductive material, or more than one of the conductive materials, is selected from the group consisting of: iron-chromium-aluminum alloys; nickel-chromium alloys, copper-nickel-based alloys, or iron-nickel-chromium alloys, and intermetallic compounds. Its features are, The electric heater (10) includes a plurality of heating elements (26) assembled together into the heating block (23). Each heating element (26) comprises the material and has a hole or channel (25) that partially defines the hole or channel (25) of the heating block (23). The plurality of longitudinal holes or channels (25) extending internally through the axially elongated heating block (23) include channels (25) formed in the gap region between the outward-facing surfaces (29) of adjacent heating elements (26).

2. The electric heater (10) according to claim 1, wherein, The heating element (26) is manufactured by using additive manufacturing, in which the heating block (23) is formed as a single body or as an assembly / set of multiple individual heating elements (26) printed by additive manufacturing, the multiple individual heating elements being electrically coupled and mechanically assembled to form the heating block (23).

3. The electric heater (10) according to claim 1 or 2, wherein, The electric heater (10) satisfies the heating surface area to volume ratio (HTVR) per unit length of the heating block (23) as defined by the following equation: Σ(A) / V≥1m -1 Wherein, Σ(A) is the sum of the heating surface areas of the holes or channels extending at least between the first longitudinal end (23a) and the second longitudinal end (23b), and V is the total envelope volume of the conductive material.

4. The electric heater (10) according to claim 3, wherein, HTVR ranges from 1.0 to 4.0m -1 1.0 to 3.0m -1 Or 1.0 to 2.5m -1 Within the range.

5. The electric heater (10) according to claim 1 or 2, wherein, The surface load of the heating element is 1 to 3 W / cm under atmospheric conditions. 2 Within the range, and the outlet temperature is in the range of 1000 to 1250°C.

6. The electric heater (10) according to claim 1 or 2, comprising a plurality of stabilizing rods or spacers (27) positioned between the heating elements (26) and abutting against the heating elements (26) along their respective lengths, the heating elements (26) being spaced apart from each other and indirectly in contact via the rods or spacers (27).

7. The electric heater (10) according to claim 6, wherein, Each of the stabilizer bars or spacers (27) is sized to create the gap region between the heating elements (26).

8. The electric heater (10) according to claim 6, wherein, At least one of the stabilizer bars or spacers (27) is arranged adjacent to three or four of the heating elements (26).

9. The electric heater (10) according to claim 6, wherein, Each of the stabilizer bars or spacers (27) is non-conductive.

10. The electric heater (10) according to claim 1 or 2, wherein, The heating elements (26) of the plurality of heating elements (26) are electrically connected in series.

11. The electric heater (10) according to claim 1 or 2, wherein, The heating block (23) includes fins or protrusions (30, 35, 36) that radially protrude into the hole or channel (25).

12. The electric heater according to claim 1 or 2, wherein, The hole or channel (25) is defined by the wall (32) of the heating block, the wall (32) including any one or combination of a hole (39), notch, groove or pawl (33, 34) that reduces the volume of material at the wall (32).

13. The electric heater (10) according to claim 1 or 2, comprising: A housing (11) positioned at least partially around the heating block (23); as well as At least one mounting base, which extends radially from the housing (11) to contact and fix the heating block (23) in position within the electric heater (10).

14. The electric heater (10) according to claim 13, further comprising a heat insulation material positioned between the housing (11) and the heating block (23).

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