GB2613777A

GB2613777A - Heating unit

Info

Publication number: GB2613777A
Application number: GB2117514.6A
Authority: GB
Inventors: David Seaton John; Paul Kinder Christopher
Original assignee: Amphenol Thermometrics Inc
Current assignee: Amphenol Thermometrics Inc
Priority date: 2021-12-03
Filing date: 2021-12-03
Publication date: 2023-06-21
Also published as: GB202117514D0

Abstract

A heating unit 20 includes a housing 22 and a plurality of heating elements 36 disposed in the housing and spaced along an axis X. Each of the plurality of heating elements includes at least one major surface 38, 40. The at least one major surface of at least one of the plurality of heating elements is arranged orthogonal to the axis. The heating elements may have a flat, generally planar or disc-like configuration and may be arranged in an array, stacked or arranged one on top of the other along the length of the axis, perimetric surfaces 35 of the heating elements being mutually aligned. The heating elements may be formed from a positive temperature coefficient (PTC) material, such as a PTC ceramic. A biasing member, such as a coil spring 60 may be provided to exert a biasing force to the heating elements to limit movement thereof. Conductors 42 may be disposed between the heating elements, the major surfaces of the heating elements being identical in shape to major surfaces of the conductors.

Description

BEATING UNIT

FIELD

[0001] The disclosure relates generally to a heating unit, and more particularly to a heating unit employing a plurality of heating elements.

BACKGROUND

[0002] Positive temperature coefficient (PTC) heating elements are typically flat, plate-like elements, that in use are arranged longitudinally in a housing. In this longitudinal, side-by-side configuration, the top surfaces of each PTC heating element may be arranged in a plane, with the bottom surface of each PTC heating element being connected to a conductor.

[0003] In such an arrangement, heat can be non-uniformly transmitted from the PTC heating elements to the surrounding housing, resulting in cool spots thereon due to suboptimal thermal transfer. In addition, in extreme conditions, the heat generated by a heater having longitudinally oriented PTC heating elements may be insufficient to de-ice or anti-ice a fluid adjacent to the heater. Such arrangements can also be difficult to easily customize.

BRIEF DESCRIPTION

[0004] According to an embodiment, a heating unit includes a housing and a plurality of heating elements disposed in the housing and spaced along an axis. Each of the plurality of heating elements includes at least one major surface. The at least one major surface of at least one of the plurality of heating elements is arranged orthogonal to the axis.

[0005] In addition to one or more of the features described herein, or as an alternative, in further embodiments at least one of the plurality of heating elements includes a positive temperature coefficient material.

[0006] In addition to one or more of the features described herein, or as an alternative, in further embodiments each of the plurality of heating elements are spaced apart from another of the plurality of heating elements along the axis [0007] In addition to one or more of the features described herein, or as an alternative, in further embodiments a plurality of conductors are thermally coupled to the plurality of heating elements, wherein at least one conductor of the plurality of conductors are interposed between adjacent heating elements of the plurality of heating elements [0008] In addition to one or more of the features described herein, or as an alternative, in further embodiments multiple conductors of the plurality of conductors are interposed between adjacent heating elements of the plurality of heating elements [0009] In addition to one or more of the features described herein, or as an alternative, in further embodiments each of the plurality of heating elements includes a perimetric surface, each perimetric surface of the plurality of heating elements being aligned with at least one additional perimetric surface of the plurality of heating elements.

[0010] In addition to one or more of the features described herein, or as an alternative, in further embodiments at least one major surface of each of the plurality of heating elements is arranged orthogonal to the axis.

[0011] According to an embodiment, a heating unit includes a housing and a plurality of heating elements disposed in the housing. The plurality of heating elements includes a first heating element and a second heating element. The first heating element includes a perimetric surface extending about a perimeter of the first heating element and the second heating element includes a perimetric surface extending about a perimeter of the second heating element. The perimetric surface of the first heating element is aligned with the perimetric surface of the second heating element.

[0012] In addition to one or more of the features described herein, or as an alternative, in further embodiments at least one conductor of the plurality of conductors includes a perimetric surface extending about a perimeter of the at least one conductor, the perimetric surface of the at least one conductor being aligned with the perimetric surface of the first heating element and the perimetric surface of the second heating element [0013] In addition to one or more of the features described herein, or as an alternative, in further embodiments a thickness of at least one of the plurality of heating elements are different than a thickness of at least one of the plurality of conductors.

[0014] In addition to one or more of the features described herein, or as an alternative, in further embodiments a thickness of at least one of the plurality of conductors is different from a thickness of another of the plurality of conductors.

[0015] According to an embodiment, a heating unit includes a housing having a first end, a second end, and a hollow interior, and a plurality of heating elements arranged in an array is positioned in the hollow interior of the housing. A biasing member is positioned proximate the second end and is positioned to exert a biasing force on the plurality of heating elements in a direction of the first end.

[0016] In addition to one or more of the features described herein, or as an alternative, in further embodiments a cap is arranged at the second end, wherein the biasing member is positioned between the cap and the plurality of heating elements.

[0017] In addition to one or more of the features described herein, or as an alternative, in further embodiments the biasing member is a coil spring and the coil spring is compressed when mounted between the cap and the plurality of heating elements.

[0018] In addition to one or more of the features described herein, or as an alternative, in further embodiments each of the plurality of heating elements has at least one major surface in contact with at least one of the plurality of conductors [0019] In addition to one or more of the features described herein, or as an alternative, in further embodiments the plurality of heating elements and the plurality of conductors are arranged along an axis, the axis being coaxial with an axis of the housing.

[0020] In addition to one or more of the features described herein, or as an alternative, in further embodiments each of the plurality of heating elements includes at least one major surface arranged orthogonal to the axis, the plurality of heating elements being aligned about a periphery of the array.

[0021] According to an embodiment, a heating unit includes a housing and at least one heating element disposed in the housing. The at least one heating element has at least one major surface. At least one conductor is thermally coupled to the at least one heating element. The at least one conductor has at least one major surface. The at least one major surface of the at least one heating element is identical in shape to the at least one major surface of the at least one conductor.

[0022] In addition to one or more of the features described herein, or as an alternative, in further embodiments the at least one heating element and the at least one conductor are arranged along an axis.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: [0024] FIG. 1 is a partially cut away perspective view of a heating unit according to an embodiment; [0025] FIG. 1A is an exploded view of a portion of the array of the heating unit according to an embodiment; [0026] FIG. 2 is a cross-sectional view of a heating unit according to an embodiment; [0027] FIG 3 is a partially cut away perspective view of the heating unit of FIG. 2 according to an embodiment; [0028] FIG. 4 is a partially cut away perspective view of a heating unit having distinct heating zones according to an embodiment; [0029] FIG. 5A is a cross-sectional view of a heating element of FIG. 1 according to an embodiment; [0030] FIG. 5B is a cross-sectional view of a conductor of FIG. 1 according to an embodiment; [0031] FIG. 6A is a side view of the heating element of FIG. 5A according to an embodiment; [0032] FIG. 6B is a side view of the conductor of FIG. 5B according to an embodiment; [0033] FIG 7A is a perspective view of a heating unit arranged in a fluid heating application according to an embodiment; [0034] FIG. 7B is an end view of the heating unit of FIG. 7A according to an embodiment; [0035] FIG. 8A is a side schematic view of heating elements configured with conductors and electrodes according to an embodiment; and [0036] FIG. 8B is a side schematic view of a heating element configured with a conductor and electrodes according to an embodiment.

DETAILED DESCRIPTION

[0037] A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures.

[0038] With reference to FIG. 1, an example of a heating unit 20, such as used to heat a fluid medium adjacent thereto, is illustrated. As shown, the heating unit 20 includes a generally elongated housing 22 having a closed first end 24, a closable second end 26, and at least one sidewall 28 extending at least partially between the first end 24 and the second end 26 to define a cavity or hollow interior 30 of the housing 22. In an embodiment, at least the first end 24 and a portion of the sidewaIl 28 of the housing 22 are formed from a thermally conductive material, such as, for example, stainless steel or another thermally conductive metal. A heating array 32, to be described in more detail below, is contained within the hollow interior 30 via the housing 22 and a cap 34 connected to the second end 26 of the housing 22. The heating array 32 may extend over the substantially entire length of the hollow interior 30, or alternatively, may extend over only a portion of a length thereof [0039] With continued reference to FIG. 1 and further reference to FIGS. 2-5, a heating unit 20 having various configurations of the heating array 32 are illustrated. The heating array 32 includes one or more heating elements 36. In an embodiment, the heating array 32 includes a plurality of heating elements 36 arranged along an axis X. Although each of the various embodiments of the heating array 32 shown in the FIGS. includes at least five heating elements 36, it should be understood that a heating array 32 having any number of heating elements 36, including but not limited to one heating element, two heating elements, three heating elements, four heating elements, or more than ten heating elements for example, are contemplated herein.

[0040] In an embodiment, each of the plurality of heating elements 36 within the array 32 is identical or substantially identical to each additional heating element 36 in the array 32. As used herein, the term "identical" is intended to include a degree of error, such as commonly associated with manufacturing tolerances. Accordingly, in an embodiment all of the heating elements 36 within the array 32 are the same size and have the same shape or geometry. In such embodiments, each of the plurality of heating elements 36 has a perimetric surface 35 extending about a perimeter (an entire perimeter) of the heating element 36 (see FIG. IA and FIG. 6A). Further, the heating elements 36 are aligned with each other about a periphery of the array 32. For example, a first heating element and a second heating element of the plurality of heating elements 36 may each include a perimetric surface, with the perimetric surface 35 of the first heating element being aligned with the perimetric surface 35 of the second heating element. In an embodiment, along with the conductors discussed below, an entire periphery of aligned perimetric surfaces 35 of the heating elements 36 may provide a combined length of dissipation surface configured to transfer heat to the adjacent housing 22 [0041] In other embodiments, each of the plurality of heating elements 36 within the array 32 may not be identical or substantially identical to each additional heating element 36 in the array 32 Accordingly, in an embodiment some of the heating elements 36 within the array 32 may have different sizes, different shapes, different geometries, or some combination of the foregoing. In other embodiments, some of the heating elements 36 may be identical to other heating elements 36 in some respects (for example, identical perimetric surfaces 35) while also being different from other heating elements 36 in some respects (for example, different thicknesses Tti). h) other embodiments, some of the heating elements 36 may have different dimensions in respective perimetric surfaces 35 and/or widths/diameters WH. For example, the heating elements 36 may have different dimensions in respective perimetric surfaces 35 and/or widths/diameters Wu to account for or to align with variations in the shape or geometry of a housing with a non-uniform geometry. In still further embodiments, the array 32 may include a first grouping of heating elements 36 that are identical to each other, as well as one or more additional groupings of heating elements 36 that are identical to each other but different from the first grouping in any respect such as size, shape, geometry, or some combination thereof, including one or more of thickness TH, dimensions of the perimetric surfaces 35, and/or width/diameter

WH

[0042] A cross-sectional view of the heating unit 20 illustrated in FIG. 5A includes an example of a heating element 36 representative of each of the plurality of heating elements within the array 32. As shown, the cross-section is taken in a plane oriented substantially perpendicular or orthogonal to the axis X. The configuration of the heating element 36, such as the cross-sectional size and shape of the heating element 36 for example, may be complementary or similar to the cross-sectional size and shape of the hollow interior 30 of the housing 22. In the illustrated, non-limiting embodiment, the housing 22 has a generally circular shape, while the heating elements 36 have a truncated circular, or generally oval or elliptical shape. As shown, the cross-sectional shape of the heating element 36 has two arcuate ends 37 connected by two linear sides 39. However, it should be understood that embodiments where the hollow interior 30 of the housing 22 and/or the heating elements 36 are circular, rectangular, square, polygonal, or another suitable shape are also within the scope of the disclosure. Likewise, embodiments where the housing 22 has other cross-sectional shapes (for example, rectangular, oval, etc.) or configurations (for example, arcuate or circular shapes) are also within the scope of the disclosure. The housing 22 may be couplable to or integrally formed with another element, such as a fluid tank or fluid conduit.

[0043] As used herein, the term "similar" is intended to describe embodiments where the cross-sectional shape of the heating element 36 is identical to the cross-sectional shape of the hollow interior 30. Alternatively, or in addition, the term "similar" may be used to describe embodiments such as shown in FIG. 5A, where at least a portion of the perimetric surface 35 of the heating element 36 is identical in shape to an adjacent portion of the hollow interior 30. However, the dimensions of the heating elements 36 at that portion may of course be different in size than those of the hollow interior 30 (for example, the dimensions of the heating elements 36 may be slightly smaller than the dimensions of the hollow interior 30 to allow the heating elements 36 to fit within the hollow interior 30 of the housing 22). For example, as shown in FIG. SA, the width or diameter WH of the heating element 36 at the arcuate ends 37 is smaller than the width or diameter W of the hollow interior 30 at the same location.

[0044] With reference now to FIG. IA and FIG. 6A, in the illustrated, non-limiting embodiment, the heating element 36 has at least one major surface, such as a first major surface 38 and a second major surface 40 arranged at opposing ends of the body of the heating element 36. As used herein, the first major surface 38 and the second major surface 40 are defined as the surfaces of the heating element 36 having the greatest surface area. In an embodiment, the first and second major surfaces 38, 40 have a planar configuration, but one or more major surfaces may have other, non-planar shapes in some embodiments (for example, a curved surface).

[0045] The thickness TH or height of the heating element 36, measured parallel to the axis X, may be substantially uniform over the cross-sectional area of each of the heating elements 36. Further, the thickness TH may be dependent on the maximum voltage to be applied to the heating element 36. In an embodiment, the thickness TH of the heating element 36 is between about lmm and 2mm for voltages between by and 250V. However, a heating element 36 having another thickness TH, such as greater than 2mm for example, is also within the scope of the disclosure. For example, a heating element 35 having a thickness TH of up to 3mm, 4mm, 5mm, lOmm, 20mm, 30mm, 40mm or 50mm is contemplated herein. It should be understood that the thickness TH of the heating element 36 may vary based on the application of the heating unit 20, the shape of the heating element 36, and/or the configuration of the conductors 42 and electrodes 50 used to deliver power to the heating element 36, as will be described in more detail below.

[0046] As best shown in FIG. 6A, the thickness TH of the heating element 36 may be substantially smaller than the diameter or width WH of the heating element 36 (measured in a plane containing the first major surface or the second major surface) such that the heating element 36 may be considered to have a flat, generally planar or disc-like configuration. In an embodiment, the thickness TH of the heating element 36 is less than or equal to 1/5 of the width WH of the heating element 36, and in some embodiments, the thickness TH of the heating element 36 is less than or equal to 1/8, 1/9, or even 1/10 of the width WH of the heating element 36. However, embodiments where the thickness TH of the heating element 36 is equal to or greater than the width WH of the heating element 36 are also within the scope of the disclosure.

[0047] In an embodiment, adjacent heating elements 36 within the axially oriented array 32 are spaced apart from one another along the axis X. The spacing between each pair of adjacent heating elements 36 within the array 32 may be uniform, as shown in FIGS. 1-3, such that heat generated by the heating array 32 is substantially homogenous over the axial length of the heating array 32. However, in other embodiments, as best shown in FIG. 4, the spacing between pairs of adjacent heating elements 36 in the array 32 may vary. This variation in the spacing may be used to form separate or distinct zones within the heating array 32, with each zone achieving a different heating output.

[0048] For example, in the illustrated, non-limiting embodiment of FIG. 4, the heating array 32 includes a first zone (Zone 1) and a second zone (Zone 2). As shown, the first zone is arranged proximate the first end 33 of the array 32 and includes three heating elements 36a separated from one another by a first distance Dl. The second zone extends from the first zone to an opposite end 62 of the array 32 and includes eight heating elements 36b separated from one another by a second distance D2. Because the second distance is greater than the first distance, the heat output from the array within the second zone is less than within the first zone. It should be understood that a heating array such as array 32 having any number of zones and any configuration of those zones is within the scope of the disclosure. Embodiments where the heating elements 36 are non-uniformly distributed within the array 32 may be particularly advantageous in applications where the first end 24 of the housing 22 is in direct contact with a fluid flow.

[0049] To maintain the desired spacing between the plurality of heating elements 36, the array 32 further includes a plurality of conductors 42 arranged in contact with the first and/or second major surface 38, 40 of each heating element 36 in the array 32. Accordingly, at least one conductor 42 of the plurality of conductors is interposed between adjacent heating elements 36. Each of the conductors 42 has at least one major surface, such as a first major surface 43 and a second major surface 45 arranged at opposite ends of the conductor 42 (see FIG. IA and FIG. 6B). In an embodiment, the major surfaces 38, 40 of each of the heating elements 36 are positioned adjacent to, affixed to, or both positioned adjacent to and affixed to at least one major surface 43,45 of one or more of the conductors 42. In some embodiments, the major surfaces 38, 40 of each of the heating elements 36 are affixed to at least one major surface 43, 45 of one or more of the conductors 42 by an adhesive, a potting material (described in more detail below) or other material. In some embodiments, the adhesive or other material has a high thermal conductivity, such as a silver-loaded conductive epoxy system, or an electrically conductive solder paste, such as, but not limited to lead-free solder, lead-based solder, and flux-core solder. In other embodiments, another component, such as an electrode 50 for example, may be positioned between adjacent heating elements 36 and conductors 42, in contact with one or both major surfaces 38, 40 of one or more heating elements 36 and one or both major surfaces 43, 45 of one or more conductors 42 (please see FIG 8A for example) The conductors 42 are formed from a material having a high thermal conductivity. Examples of such materials include, but are not limited to brass, copper, aluminum, and silver.

[0050] In the non-limiting embodiment of FIGS. 2-4, a single conductor 42 is positioned between adjacent heating elements 36. In such embodiments, the major surfaces 43, 45 of the conductors 42 are arranged in thermal communication with respective major surfaces 38, 40 of two adjacent heating elements 36. In another embodiment, such as that shown in FIG 1, multiple conductors 42, such as two conductors for example, may be positioned between adjacent heating elements 36. In such embodiments, only one major surface 43 or 45 of each conductor 42 is in thermal communication with a major surface 38 or 40 of a heating element 36. Accordingly, the major surface 43 of a first conductor 42 may be in contact with an adjacent major surface 45 of a second conductor 42. Despite this example, a heating array 32 having more than two conductors 42 arranged between one or more pairs of heating elements 36 is also within the scope of the disclosure.

[0051] Because the spacing between pairs of adjacent heating elements 36 may be uniform or may vary, as previously described, the configuration of the one or more conductors 42 arranged within the spacing between each pair of adjacent heating elements 36 may be the same or may vary to occupy the spacing between the heating elements 36. Further, different numbers of conductors 42 may be arranged in the spacing between different pairs of heating elements 36.

[0052] It should be understood that the total number of heating elements 36 within the heating array 32, the spacing between adjacent heating elements 36, and the number and configuration of the conductors 42 arranged within the spacing between adjacent heating elements 36, may vary based on one or more parameters of the specific application in which the heating array 32 is configured for use. These parameters may include but are not limited to the size requirements of the heating unit 20 and/or array 32, the temperature of the medium to be heated by the heating unit 20 and/or array 32, and the current provided to heating unit 20 and/or array 32.

[0053] In an embodiment, each of the conductors 42 has a configuration similar to the configuration of the heating elements 36 within the array 32. More specifically, the cross-sectional size and/or shape of the conductor 42, taken in a plane oriented perpendicular or orthogonal to the axis X, may be identical or substantially identical to the cross-sectional size and/or shape of the heating elements 36. For example, in the non-limiting embodiment of FIG. 1 and FIG. 5B, the conductors 42 have a truncated circular, oval, or elliptical shape with two arcuate ends 49 connected by two linear sides 51 as described with respect to FIG. 5A. In such embodiments, the major surfaces 43, 45 of the conductors 42 are identical to the major surfaces 38, 40 of the heating elements 36.

[0054] In other embodiments, each of the conductors 42 may not have a configuration similar to the configuration of the heating elements 36 within the array 32. Likewise, each of the conductors 42 may not have a configuration similar to the other conductors 42. Accordingly, in an embodiment some of the conductors 42 may have different sizes, different shapes, different geometries, or some combination of the foregoing, as compared to each other and/or the heating elements 36. In yet other embodiments, some of the conductors 42 may be identical to other conductors 42 and/or the heating elements 36 in some respects (for example, identical perimetric surfaces) while also being different from other conductors 42 or the heating elements 36 in some respects (for example, different thicknesses Tc). In other embodiments, some of the conductors 42 may have different dimensions in respective perimetric surfaces 47 and/or widths/diameters Wc as compared to each other and/or the heating elements 36. For example, the conductors 42 may have different dimensions in respective perimetric surfaces 47 and/or widths/diameters Wc as compared to each other and/or the heating elements 36 to account for or to align with variations in the shape or geometry of a housing with a non-uniform geometry. In still further embodiments, the array 32 may include a first grouping of conductors 42 that are identical to each other, as well as one or more additional groupings of conductors 42 that are identical to each other but different from the first grouping in any respect such as size, shape, geometry, or some combination thereof, including one or more of thickness, dimensions of the perimetric surfaces, and/or width/diameter.

[0055] Further, each of the plurality of conductors 42 has a perimetric surface, illustrated at 47 in FIGS. 1A, 5B, and 6B, extending about a perimeter (an entire perimeter) of the conductor 42. Accordingly, in embodiments where the major surfaces 43, 45 of the conductors 42 are identical to the major surfaces 38, 40 of the heating elements 36, the perimetric surfaces 35 of the heating elements 36 are aligned with the perimetric surfaces 47 of the conductors 42. However, embodiments where a diameter or width Wc of at least one of the conductors 42 is different from a diameter or width WH of at least one of the heating elements 36 are also within the scope of the disclosure.

[0056] Further, each of the conductors 42 may have a configuration similar to the hollow interior 30 of the housing 22. In an embodiment, best shown in FIG. 5B, at least a portion of the perimetric surface 47 of the conductors 42 is identical in shape to an adjacent portion of the hollow interior 30. However, the dimensions of the conductors 42 at that portion may of course be different in size than those of the hollow interior 30. For example, the width or diameter Wc of the conductor 42 at the arcuate ends 49 may be smaller than the width or diameter W of the hollow interior 30 at the same location. The above being said, it should be understood that embodiments where the cross-sectional shape of the conductor 42 is identical to the cross-sectional shape of the hollow interior 30 are also contemplated herein. By making the heating elements 36 and the conductors 42 similar in size and shape to the hollow interior 30, the housing 22 is heated by the heating array 32 generally uniformly about the periphery of the housing 22.

[0057] The thickness Tc or height of a conductor 42, measured parallel to the axis X, may be substantially uniform over the cross-sectional area of each of the conductors 42. The thickness or height Tc of each conductor 42 is determined by the size of the spacing between adjacent heating elements 36 and/or the total number of conductors 42 to be arranged between adjacent heating elements 36. In an embodiment, the thickness Tc one or more of the conductors 42, and in some embodiments all of the conductors 42, is greater than the thickness TH of the heating elements 36 [0058] As previously described, the plurality of heating elements 36 and the plurality of conductors 42 are mounted within the array 32 in a coaxial configuration. As shown, the axis X extends through a center of each of the of heating elements 36 and each of the conductors 42. In an embodiment, the first major surface 38 of each heating element 36 is arranged within a different or distinct plane from a first major surface 38 of another heating element 36 (i.e., the first major surfaces 38 are not coplanar) and the second major surface 40 of each heating element 36 is arranged within a different or distinct plane from a second major surface 40 of another heating element 36 (i.e., the second major surfaces 40 are not coplanar). As shown, at least one of the first major surface 38 and the second major surface 40 of at least one heating element 36, and in some embodiments of each heating element 36, is oriented substantially orthogonal to the axis X. Accordingly, the heating elements 36, or the heating elements 36 and the conductors 42 in combination, may be considered to be "stacked" or arranged one on top of the other along the length of the axis X. [0059] An electrode 50 (see FIG. 1) and the associated wiring may be soldered onto a portion of each of the conductors 42, such as near an end located adjacent to a heating element 36 for example, to electrically couple each of the conductors 42 to a power source (not shown) by a plurality of wires 52 (see FIGS. 25). Alternatively, or in addition, one or more of the electrodes 50 may be positioned adjacent to or may be affixed to a surface of a heating element 36. As shown in FIG. 8A, electrodes 50 may be attached to one or both major surfaces 38, 40 of a heating element 36. In another embodiment, as shown in FIG. 8B, electrodes 50 may be attached to at least one side surface, such as a portion of the parametric surface 35 for example, of the heating element 36. In such embodiments, the electrode 50 may be substantially identical in size and shape to the surface of the heating element 36 to which the electrode 50 is connected. However, embodiments where the electrode 50 does not cover an entire surface of the heating element 36 are also within the scope of the disclosure. Configurations where an electrode 50 is directly connected to the heating element 36, and in particular connected to a side surface thereof, may be particularly suitable in applications where the heating elements 36 include a quadrilateral shape, such as a square or rectangle.

[0060] In an embodiment, the heating elements 36 are connected to the power source in parallel. In the illustrated, non-limiting embodiment, best shown in FIGS. 1 and 5, the wires 52 are arranged about an exterior surface of the array 32. As will be discussed in more detail below, by using an array of heating elements 36 and conductors 42 having an oval or truncated circular shape, these wires 52 can easily be arranged in a gap G defined between the linear sides 39 of the array 32 and the interior surface 54 of the housing 22 where the gap G is largest. However, embodiments where one or more of the wires 52 is arranged at another location relative to the array 32 are also contemplated herein. For example, in an embodiment, the heating elements 36 and conductors 42 may have one or more through holes (e.g., a central through hole aligned with the axis X and/or one or more through holes offset from the axis X), and the plurality of wires 52 may be mounted at or near a center of the array, within these through holes.

[0061] When the heating array 32 is installed within the hollow interior 30 of the housing 22, the axis X of the heating array 32 is coaxial with an axis of the elongated housing 22. A gap G (see FIG. 5) is formed between the interior surface 54 of the housing 22 and a surface of heating array 32, as formed by the perimetric surfaces 35 of heating elements 36 or the perimetric surfaces 47 of conductors 42. This gap G extends about at least a portion, and in some embodiments about the entire periphery or perimeter of the array 32 to facilitate insertion of the array 32 into the hollow interior 30 without interference. In embodiments where the cross-sectional shape of the array 32, defined by the cross-sectional shape of the heating elements 36 and the cross-sectional shape of the conductors 42, is different than the cross-sectional shape of the hollow interior 30, the width of the gap G measured perpendicular or orthogonal to the axis X, varies about the perimeter or perimetric surface of the array 32. For example, the gap G is greater between the interior surface 54 of the housing 22 and the linear sides 39 of the cross-sectional shape of the array 32 than between the interior surface of the housing 22 and the arcuate ends 37 of the cross-sectional shape of the array 32. However, it should be understood that embodiments where the cross-sectional shape of the array 32 is identical to the cross-sectional shape of the hollow interior 30 are also contemplated herein. In such embodiments, the gap G defined between the interior surface 54 of the housing 22 and the perimetric surface of the array 32 is substantially uniform about the entire perimeter of the array 32.

[0062] To further minimize the thermal resistance between the housing 22 and the heating array 32, a potting material, such as a thermal polymer for example, illustrated at 56 in FIG. 5, encapsulates and seals the heating elements 36, the conductors 42, the electrodes 50, and the wires 52. In the illustrated, non-limiting embodiment, the potting material 56 has an annular configuration extending about the entire periphery of the heating array 32. The potting material 56 is thermally conductive such that the heat from the heating elements 36 and the conductors 42 is transmitted to the housing 22 via the potting material 56. The heating elements 36 and the conductors 42 may be in direct contact with one another, or the potting material 56 may be interspersed between adjacent heating elements 36 and conductors 42. In other embodiments, another material (e.g., an electrically conductive solder) may be positioned between adjacent heating elements 36 and conductors 42 while the potting material 56 surrounds the heating elements 36 and conductors 42 in a substantially annular configuration. In some embodiments, the heating array 32 is absent a potting material, an adhesive, or both of a potting material and an adhesive. For example, in some embodiments, the heating elements 36 and the conductors 42 of the heating array 32 are held in position by a biasing member 60, to be described in more detail below, without the use of adhesives, potting material, or both. In other embodiments, the heating array 32 includes one or more of a potting material, an adhesive and a biasing member 60.

[0063] In an embodiment, a load is applied to the heating array 32 mounted within the housing 22. With reference again to FIG. 1, a biasing member 60, such as a coil spring for example, may be arranged between the cap 34 and the adjacent second end 62 of the heating array 32, which may be a conductor 42 or a heating element 36.

In an embodiment, the natural or undeformed length of the biasing member 60 is greater than the distance between the end 62 of the heating array 32 and the interior surface of the cap 34. As a result, when the cap 34 is connected to the housing 22 to close the hollow interior 30, the biasing member 60 is compressed and therefore applies a biasing force or load to the heating array 32 in the direction of the first end 24 of the housing 22. This force may dampen any vibrations transmitted to the heating unit 20 by limiting movement of the array 32 within the hollow interior 30. As noted above, this force applied to the array 32 by the biasing member 60 may be sufficient to retain the conductors 42 and the heating elements 36 in position within the array 32, thereby eliminating the need for an adhesive or other material to affix the heating elements 36 to the conductors 42. However, embodiments where the biasing member 60 is applied to an array 32 where the heating elements 36 and the conductors 42 are affixed to one another via an adhesive or other material are also within the scope of the disclosure. Although the biasing member 60 is described herein as being connected to the cap 34, it should be understood that embodiments where another component arranged at the second end of the housing 22 is operable to compress the biasing member 60 to generate the load on the array 32 are also contemplated herein.

[0064] In an embodiment, the heating elements 36 within the array 32 include or are formed from a positive temperature coefficient (PTC) material, such as a positive temperature coefficient ceramic. However, it should be understood that a heating element 36 having any suitable configuration, including a resistive heating element or a heating element formed from any suitable self-heating material, self-regulating material or positive temperature coefficient (PTC) material is within the scope of the disclosure. A positive temperature coefficient material is a material having a resistance that varies based on the temperature of the material When the heating elements 36 are electrically connected, the positive temperature coefficient material of the heating elements 36 will self-regulate to maintain the temperature of the heating array 32 near the predetermined temperature. As the positive temperature coefficient material of the heating element 36 reaches the predetermined temperature, small changes in temperature result in largo changes in the resistance of We positive temperature coefficient material. By using a self-regulating positive temperature coefficient material, the temperature of the heating array 32 will automatically adjust to changes in the ambient temperature to maintain a substantially constant surface temperature without the need for external controls.

[0065] With reference now to FIGS. 7A and 7B, an example of the heating unit 20 installed relative to a fluid flow to be heated in a fluid heating application is illustrated. In the illustrated, non-limiting embodiment, a secondary housing 70 is arranged concentrically about at least a portion of the housing 22 of the heating unit 20. An annular clearance 72 is defined between an exterior surface 74 of the housing 22 and an interior surface 76 of the secondary housing 70. The secondary housing 70 may have an axial length less than or equal to the length of the housing 22, and in some embodiments the axial length of the heating array 32. Accordingly, an inlet 78 of the annular clearance 72 may be positioned adjacent to the first end 24 of the housing 22, and an outlet 80 of the annular clearance 72 may be positioned upstream from the second end 26 of the housing 22.

[0066] In an embodiment, the outlet 80 is located at a point along the length of the heating unit 20 proximate the end 62 of the array 32 closest to the second end 26. As shown, a fluid F to be heated flows from the inlet 78 of the annular clearance 72 along the exterior surface 74 of the heating unit 20 to the outlet 80 of the annular clearance 72. At the outlet 80, the heated fluid F may be directed away from the heating unit 20 at an angle to the axis X of the heating array 32 and the housing 22. Although the fluid F is illustrated as turning approximately ninety degrees at the outlet 80, it should be understood that any suitable direction is within the scope of the disclosure. Within the annular clearance 72, the annular flow of the fluid F to be heated surrounds the heating unit 20 such that heat is transferred from the heating unit 20 to the fluid F about an entire periphery of the housing 22.

[0067] By stacking the heating elements 36 and conductors 42 along an axis X as described herein, an entire periphery of the heating array 32 formed by the perimetric surfaces 35 of the plurality of heating elements 36 and the perimetric surfaces 47 of the plurality of conductors 42 may provide a dissipation surface configured to transfer heat to the adjacent housing 22. Because this dissipation surface is significantly increased compared to existing heaters, the thermal transfer efficiency of the heating unit 20 is also improved relative to existing heaters. Further, the power output per heating element 36 may be doubled relative to an existing heating unit having the same number of heating elements 36 and the same current provided thereto, resulting in more effective heating, even in extreme conditions.

[0068] A heating unit 20 having a heating array 32 as described herein may be configured to heat a fluid medium, such as to perform active de-icing or anti-icing of the fluid medium in a low temperature environment. Accordingly, the heating unit 20 is suitable for use in a plurality of different de-icing and anti-icing applications Examples of these applications include, but are not limited to, water injection systems such as for emission reduction systems associated with gasoline powered engines, and fuel or other fluid heating systems such as used in automotive or aerospace applications. In an embodiment, the heating unit 20 is used to heat the water byproduct resulting from hydrogen fuel cell energy generation. As an example, the heating unit 20 may be coupled to a fluid tank such that at least a portion of the housing 22 is in contact with the fluid, or the heating unit 20 may be coupled to a fluid line or conduit such that at least a portion of the housing 22 is positioned in the pathway of a fluid through the fluid line or conduit. The housing 22 may be coupleable to (and, in some embodiments, removable from) a separate element (for example, a tank or fluid conduit) or the housing 22 may be integral with the fluid-containing element, such as being integral with a fluid tank or fluid conduit However, it should be understood that the heating unit 20 is not limited to de-icing and anti-icing applications or the specific applications listed above, and rather may be used in any application requiring a fluid to be heated.

[0069] The term -about" is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.

[0070] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms "a-, "an' and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof [0071] While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims

Claims

What is claimed is: 1. A heating unit comprising: a housing; a plurality of heating elements disposed in said housing and spaced along an axis, wherein each of said plurality of heating elements includes at least one major surface, and wherein said at least one major surface of at least one of said plurality of heating elements is arranged orthogonal to said axis.
2. The heating unit of claim 1, wherein at least one of said plurality of heating elements includes a positive temperature coefficient material.
3. The heating unit of claim 1, wherein each of said plurality of heating elements is spaced apart from another of said plurality of heating elements along said axis.
4. The heating unit of claim 1, further comprising a plurality of conductors thermally coupled to said plurality of heating elements, wherein at least one conductor of said plurality of conductors is interposed between adjacent heating elements of said plurality of heating elements.
5. The heating unit of claim 4, wherein multiple conductors of said plurality of conductors are interposed between adjacent heating elements of said plurality of heating elements.
6. The heating unit of claim 1, wherein each of said plurality of heating elements includes a perimetric surface, each perimetric surface of said plurality of heating elements being aligned with at least one additional perimetric surface of said plurality of heating elements.
7 The heating unit of claim 1, wherein said at least one major surface of each of said plurality of heating elements is arranged orthogonal to said axis.
8. A heating unit comprising: a housing and a plurality of heating elements disposed in said housing, said plurality of heating elements including a first heating element and a second heating element, wherein said first heating element includes a perimetric surface extending about a perimeter of said first heating element, and said second heating element includes a perimetric surface extending about a perimeter of said second heating element; wherein said perimetric surface of said first heating element is aligned with said perimetric surface of said second heating element.
9 The heating unit of claim 8, further comprising a plurality of conductors thermally coupled to said plurality of heating elements.
10. The heating unit of claim 9, wherein at least one conductor of said plurality of conductors is interposed between adjacent heating elements of said plurality of heating elements.
11. The heating unit of claim 9, wherein at least one conductor of said plurality of conductors includes a perimetric surface extending about a perimeter of said at least one conductor, said perimetric surface of said at least one conductor being aligned with said perimetric surface of said first heating element and said perimetric surface of said second heating element 12 The heating unit of claim 9, wherein a thickness of at least one of said plurality of heating elements is different than a thickness of at least one of said plurality of conductors.13 The heating unit of claim 9, wherein a thickness of at least one of said plurality of conductors is different from a thickness of another of said plurality of conductors.14. The heating unit of claim 8, wherein at least one of said plurality of heating elements includes a positive temperature coefficient material 15. A heating unit comprising: a housing having a first end, a second end, and a hollowinterior; a plurality of heating elements arranged in an array in said hollow interior; and a biasing member positioned proximate said second end to exert a biasing force on said plurality of heating elements in a direction of said first end.16. The heating unit of claim 15, further comprising a cap arranged at said second end, wherein said biasing member is positioned between said cap and said plurality of heating elements.17. The heating unit of claim 16, wherein said biasing member is a coil spring, and said coil spring is compressed when mounted between said cap and said plurality of heating elements.18. The heating unit of claim 15, further comprising a plurality of conductors thermally coupled to said plurality of heating elements, wherein at least one conductor of said plurality of conductors is interposed between adjacent heating elements of said plurality of heating elements.19 The heating unit of claim 18, wherein each of said plurality of heating elements has at least one major surface in contact with at least one of said plurality of conductors The heating unit of claim 18, wherein said plurality of heating elements and said plurality of conductors are arranged along an axis, said axis being coaxial with an axis of said housing.21. The heating unit of claim 20, wherein each of said plurality of heating elements includes at least one major surface arranged orthogonal to said axis, said plurality of heating elements being aligned about a periphery of said array.22. The heating unit of claim 15, wherein said plurality of heating elements includes a positive temperature coefficient material 23. A heating unit comprising: a housing; at least one heating element disposed in said housing, said at least one heating element having at least one major surface; and at least one conductor thermally coupled to said at least one heating element, said at least one conductor having at least one major surface; wherein said at least one major surface of said at least one heating element is identical in shape to said at least one major surface of said at least one conductor.24. The heating unit of claim 24, wherein said at least one heating element and said at least one conductor are arranged along an axis.25. The heating unit of claim 24, wherein a thickness of said at least one heating element measured parallel to said axis is different than a thickness of said at least one conductor.26. The heating unit of claim 23, wherein said at least one heating element includes a positive temperature coefficient material.