EP4681501A1

EP4681501A1 - High-power electrical heater

Info

Publication number: EP4681501A1
Application number: EP24717522.7A
Authority: EP
Inventors: Raul Ricardo Rico; Uwe Juretzek
Original assignee: Siemens Energy Global GmbH and Co KG
Current assignee: Siemens Energy Global GmbH and Co KG
Priority date: 2023-04-17
Filing date: 2024-03-15
Publication date: 2026-01-21
Also published as: CN121312249A; KR20260003729A; WO2024220181A1

Abstract

An electric heater includes a core and a primary winding positioned adjacent the core and operable at a power level greater than 1 MW to produce a flow of primary current. A first flow member extends around a first portion of the core and defines an inlet, a second flow member extends around a second portion of the core and defines an outlet. A third flow member is disposed adjacent the first surface and is connected to the first flow member and the second flow member to complete a continuous flow path between the inlet and the outlet. The first flow member, the second flow member, and the third flow member cooperate to define a portion of a secondary winding. A flow of fluid is delivered to the inlet and collected from the outlet, the flow of fluid is heated in response to a flow of secondary current in the secondary winding which is induced by the flow of primary current.

Description

HIGH-POWER ELECTRICAL HEATER

BACKGROUND

[0001] Many industrial processes or other processes require a source of high temperature heat. The heat is often provided using water or another fluid that is heated via a combustion process such as in a boiler, furnace, or other heating device. Often, these heating devices are fueled using fossil fuels such as coal, oil, or natural gas.

[0002] From an environmental perspective, a replacement heat source that does not use fossil fuels but is capable of providing the necessary level of heat, generally in the form of hot water or steam, or any other fluid would be desirable. However, currently available conventional electrical heating means are not scalable to the high-power levels needed for most industrial processes.

BRIEF SUMMARY

[0003] In one aspect, an electric heater includes a core oriented to define a first surface and a second surface opposite the first surface. A primary winding is positioned around the core and is operable at a power level greater than 1 MW to produce a flow of primary current. A first flow member extends around a first portion of the core and defines an inlet, a second flow member extends around a second portion of the core and defines an outlet, the second portion is different than the first portion. A third flow member is disposed adjacent the first surface and is connected to the first flow member and the second flow member to complete a continuous flow path for the process fluid between the inlet and the outlet. The first flow member, the second flow member, and the third flow member cooperate to define a portion of a secondary winding. The secondary winding is completed (closed) by a power conducting connection piece between the first and the second flow member. A flow of fluid is delivered to the inlet and collected from the outlet, the flow of fluid is heated in response to a flow of secondary current in the secondary winding which is induced by the flow of primary current.

[0004] In another aspect, an electric heater includes a core oriented to define a first surface and a second surface opposite the first surface. A primary winding is positioned in between the core surfaces and is operable at a power level greater than 1 MW to produce a flow of primary current. A first flow member extends around a first portion of the core and defines an inlet, a second flow member extends around a second portion of the core and defines an outlet, the second portion is different than the first portion. A third flow member is disposed adjacent the first surface and is connected to the first flow member and the second flow member to complete a continuous flow path for the process fluid between the inlet and the outlet. The first flow member, the second flow member, and the third flow member cooperate to define a portion of a secondary winding. The secondary winding is completed (closed) by a power conducting connection piece between the first and the second flow member. A flow of fluid is delivered to the inlet and collected from the outlet. The flow of fluid is heated in response to a flow of secondary current in the secondary winding which is induced by the flow of primary current.

[0005] The electric heater may also contain a core that has a plurality of laminations stacked in a first direction, and where each lamination is formed from a magnetic material.

[0006] The electric heater may also include a core in which the magnetic material is wound from a continuous strip of magnetic material.

[0007] The electric heater may also operate at a power level between 1 MW and 1000 MW.

[0008] The electric heater may also include a third flow member having a first tube arranged along a serpentine path that extends between the first flow member and the second flow member.

[0009] The electric heater may also include a plurality of tubes and a plurality of end caps, where each tube of the plurality of tubes is straight, and where the plurality of tubes and plurality of end caps cooperate to define a serpentine path that extends between the first flow member and the second flow member.

[0010] For most even fluid flow distribution the plurality of tubes of the third flow member every single tube can stay completely separated. This can be combined with a first and a second flow member comprised of a single larger diameter tube connecting to the plurality of single tubes of the third flow member via a connecting piece.

[0011] The electric heater may also include an inlet manifold and an outlet manifold, and where the inlet of the first flow member is connected to the inlet manifold and the outlet of the second flow member is connected to the outlet manifold.

[0012] The electric heater may also include a third flow member that is removable from the first flow member and the second flow member without disassembly of the core and the primary winding.

[0013] The electric heater may also include a core that defines three core bars and two core apertures, where the primary winding includes a first phase winding that extends around a first core bar, a second phase winding that extends around a second core bar, a third phase winding that extends around a third core bar, and where the secondary winding includes a first continuous flow path that extends around the first core bar, a second continuous flow path that extends around the second core bar, and a third continuous flow path that extends around the third core bar.

[0014] The electric heater may also include a first, a second and a third phase primary winding which is enclosed by a first, second and third core.

[0015] The electric heater may also be comprised of a single phase or two-phase electrical arrangement. The two-phase arrangement can be operated as a 3-phase system.

[0016] The electric heater may also include a first surface that is a top surface and a second surface that is a bottom surface, and where the first direction extends between the bottom surface and the top surface and is vertical.

[0017] The electric heater may also include a first surface that is a right surface and a second surface that is a left surface, and where the first direction extends between the right surface and the left surface and is horizontal.

[0018] The electric heater may also include a first flow member that is one of a plurality of first flow members, each first flow member including an inlet that is connected to the inlet manifold, and where the second flow member is one of a plurality of second flow members, each second flow member including an outlet that is connected to the outlet manifold.

[0019] The electric heater may also include a third flow member that is one of a plurality of third flow members, each third flow member connected to a corresponding one of the first flow members and one of the second flow members to define one of a plurality of continuous flow paths, each of the continuous flow paths being fluidly isolated from the other of the continuous flow paths between but not including the inlet manifold and the outlet manifold. Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

[0020] The primary winding, core, and secondary winding of at least a single phase are installed adjacent to each other providing that the connection between the aforementioned items is purely by a magnetic field. This gives the advantage that the high temperature secondary winding is not physically connected to the other parts of the electric heater, which operate at a lower temperature and thus can avoid high stresses and allow for a high lifetime.

[0021] In another aspect, a method of heating a flow of fluid includes applying a primary winding to a core, positioning a secondary winding around the core, the secondary winding defining a continuous flow path between an inlet and an outlet, and directing the flow of fluid to the inlet, through the continuous flow path, and out the outlet. The method also includes directing a flow of primary current to the primary winding, the flow of primary current having a primary voltage that results in a power level of at least 1 MW. The method also includes inducing a flow of secondary current in the secondary winding in response to the flow of primary current, heating the secondary winding in response to the flow of secondary current, and heating the flow of fluid in response to the heating of the secondary winding.

[0022] The method of heating a flow of fluid further includes stacking a plurality of laminations in a first direction, and where each lamination is formed from a magnetic material.

[0023] The method of heating a flow of fluid may also include operating at a power level between 1 MW and 1000 MW. [0024] The method of heating a flow of fluid may also include a third flow member that includes a first tube arranged along a serpentine path that extends between the first flow member and the second flow member.

[0025] The method of heating a flow of fluid further includes a plurality of tubes and a plurality of end caps, and where each tube is straight, the method further includes connecting one quarter of the plurality of tubes to the first flow member and to a first end cap, connecting a second quarter of the plurality of tubes to the first end cap and a second end cap, connecting a third quarter of the plurality of tubes to the second end cap and a third end cap, and connecting a fourth quarter of the plurality of tubes to the third end cap and the second flow member, the plurality of tubes and plurality of end caps cooperating to define a serpentine path between the first flow member and the second flow member.

[0026] The method of heating a flow of fluid may also include a first flow member that is one of a plurality of first flow members and the second flow member is one of a plurality of second flow members, each first flow member including an inlet and each second flow member including an outlet, the method further includes connecting each inlet of each of the first flow members to an inlet manifold and connecting each outlet of the second flow members to an outlet manifold.

[0027] The method of heating a flow of fluid further includes removing the third flow member from the first flow member and the second flow member without disassembly of the core and the primary winding.

[0028] The method of heating a flow of fluid may also include utilizing a core that defines three core bars and two core apertures, and where the primary winding includes a first phase winding, a second phase winding, and a third phase winding, and the secondary winding includes a first continuous flow path, a second continuous flow path, and a third continuous flow path, the method further includes extending the first phase winding around a first core bar, the second phase winding around a second core bar, the third phase winding around a third core bar, the first continuous flow path around the first core bar, the second continuous flow path around the second core bar, and the third continuous flow path around the third core bar.

[0029] The method of heating a flow of fluid may also include a third flow member that is one of a plurality of third flow members, the method further includes connecting each third flow member to a corresponding one of the first flow members and one of the second flow members to define one of a plurality of continuous flow paths each of the continuous flow paths being fluidly isolated from the other of the continuous flow paths between but not including the inlet manifold and the outlet manifold. Other technical features may be readily apparent to one skilled in the art from the following figures, descriptions, and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.

[0031] FIG. 1 is a perspective view a high-power electric heater operable to heat a flow of fluid.

[0032] FIG. 2 is a perspective view of a core for use in the electric heater of FIG. 1.

[0033] FIG. 3 is a section view of the electric heater of FIG. 1.

[0034] FIG. 4 is a schematic illustration of the electric heater of FIG. 1.

[0035] FIG. 5 illustrates an arrangement of a high-power electric heater operable to heat a flow of fluid.

[0036] FIG. 6 illustrates another arrangement of a high-power electric heater having a toroidal core and operable to heat a flow of fluid.

[0037] FIG. 7 illustrates an aspect of the subject matter in accordance with one embodiment.

DETAILED DESCRIPTION

[0038] Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in this description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Furthermore, while multiple embodiments or constructions may be described herein, any features, methods, steps, components, and the like described with regard to one embodiment are equally applicable to other embodiments absent a specific statement to the contrary.

[0039] Various technologies that pertain to systems and methods will now be described with reference to the drawings, where like reference numerals represent like elements throughout. The drawings discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged apparatus. It is to be understood that functionality that is described as being carried out by certain system elements may be performed by multiple elements. Similarly, for instance, an element may be configured to perform functionality that is described as being carried out by multiple elements. The numerous innovative teachings of the present application will be described with reference to exemplary non-limiting embodiments.

[0040] While terms such as “first”, “second”, “third” and so forth may be used herein to refer to various elements, information, functions, or acts, these elements, information, functions, or acts should not be limited by these terms. Rather these numeral adjectives are used to distinguish different elements, information, functions or acts from each other. For example, a first element, information, function, or act could be termed a second element, information, function, or act, and, similarly, a second element, information, function, or act could be termed a first element, information, function, or act, without departing from the scope of the present disclosure.

[0041] In addition, the term “adjacent to” may mean that an element is relatively near to but not in contact with a further element or that the element is in contact with the further portion, unless the context clearly indicates otherwise. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise. Terms “about” or “substantially” or like terms are intended to cover variations in a value that are within normal industry manufacturing tolerances for that dimension. If no industry standard is available, a variation of twenty percent would fall within the meaning of these terms unless otherwise stated.

[0042] Many industrial processes require heat which is typically provided in the form of hot water or steam, a hot gas, oil, or another hot fluid such as a brine, a molten salt, air, supercritical CO2, helium, hydrogen, hydrocarbons, molten metal, a particle-laden gas stream and the like. To date, most of that heat has been provided by boilers or furnaces that combust fossil fuels such as coal, oil, or natural gas, to produce steam or to heat another fluid directly. In many cases, the energy required to produce the necessary heat is in excess of one MW and as high as several hundred or even one thousand MWs.

[0043] FIG. 1 illustrates an arrangement of a high-power electric heater 100 that is capable of operating in the 1-1000 MW range, and preferably in the 10-100 MW range, and at induction frequencies between 30 and 400 Hz to provide heat for any desired process. Of course, other arrangements can operate in different power ranges including from 10 to 1000 MW. The electric heater 100 includes a core 200, a primary winding 102, and a secondary winding 104. The core 200, best illustrated in FIG. 2 includes a plurality of laminations 202 stacked in a stackwise or first direction 204. In the illustrated construction, the first direction 204 extends from a bottom surface 206 of the core 200 to a top surface 208 of the core 200 and is vertical with other orientations and arrangements being possible. Each of the laminations 202 includes a desired shape and is formed from a magnetic of ferromagnetic material such as iron, electrical steel, or carbon steel.

[0044] The core can be laminated in one direction, but we are proposing a certain kind of toroidal cores that are cheaper to "stack" because they are wound. We also want to claim ferrite or powdered cores since these may offer low quality, but large low-cost alternatives.

[0045] In the illustrated construction, each lamination 202 has a shape that when stacked with the other laminations 202 cooperates to define a first core bar 210, a second core bar 212, and a third core bar 214. Core apertures 216 are defined between adjacent core bars. This results in a core 200 suitable for use as a three-phase core. The lamination 202 can be formed as a single continuous piece or multiple pieces aligned to form the desired final lamination shape.

[0046] Returning to FIG. 1, the primary winding 102 includes a first phase winding 106 that is arranged around the first core bar 210, a second phase winding 108 that is arranged around the second core bar 212, and a third phase winding 110 that is arranged around the third core bar 214. When operating with three-phase power, the first phase directs current through the first phase winding 106, the second phase directs current through the second phase winding 108, and the third phase directs current through the third phase winding 110. In other constructions, a different arrangement may be used. For example, a single-phase power supply may include a single winding around a single core bar.

[0047] The secondary winding 104 includes a plurality of first continuous flow paths 112 arranged around the first core bar 210, a plurality of second continuous flow paths 114 arranged around the second core bar 212, and a plurality of third continuous flow paths 116 arranged around the third core bar 214.

[0048] Each of the first continuous flow paths 112, second continuous flow paths 114, and third continuous flow paths 116 include a first flow member 118, a second flow member 120, and a third flow member 122, that connect to an inlet manifold 124, and an outlet manifold 126. For each continuous flow path, each of the first flow members 118 includes an inlet opening that is coupled to the inlet manifold 124 and a second end opposite the inlet opening. In the illustrated construction, each of the first flow members 118 are vertically oriented, are substantially straight, and are normal to a central axis of the inlet manifold 124. The first flow members 118 are arranged along a first side of one of the respective core bars 210, 212, 214.

[0049] In the illustrated construction, the inlet manifold 124 is a cylindrical pipe or tube that is closed at one end and defines an inlet 128 at the opposite end. Each of the first flow members 118 for a particular phase joins the inlet manifold 124 for that particular phase at a point along the outer wall of the inlet manifold 124. In other arrangements, other shapes or arrangements are used for the inlet manifold 124 as may be desired.

[0050] For each continuous flow path, each of the second flow members 120 for a particular phase includes an outlet opening that is coupled to the outlet manifold 126 for that particular phase and a second end opposite the outlet opening. In the illustrated construction, each of the second flow members 120 are vertically oriented, are substantially straight, and are normal to a central axis of the outlet manifold 126. The second flow members 120 are arranged along a second side of one of the respective core bars 210, 212, 214 opposite the first side. [0051] In the illustrated construction, the outlet manifold 126 is a cylindrical pipe or tube that is closed at one end and defines an outlet 130 at the opposite end. Each of the second flow members 120 joins the outlet manifold 126 at a point along the outer wall of the outlet manifold 126. In other arrangements, other shapes or arrangements are used for the outlet manifold 126 as may be desired.

[0052] While the construction illustrated in FIG. 1 includes first flow members 118 and second flow members 120 arranged in a vertical straight orientation parallel to one another, other arrangements are possible.

[0053] For each continuous flow path, each of the third flow members 122 includes a first end that connects to the second end of the first flow member 118 and a second end that connects to the second end of the second flow member 120. Thus, each set of one of the first flow members 118, second flow members 120, and third flow members 122 completes a continuous flow path that extends between the inlet 128 and the outlet 130.

[0054] In another arrangement, the first flow member 118 and the second flow member 120 are formed as a single member with a single inlet 128 and outlet 130. This single member connects to the ends of the third flow member 122 to form a continuous flow path. The inlet and outlet manifolds for the fluid connections would move to one of the connections between this single member and flow member 122.

[0055] To provide the most even flow distribution in the plurality of tubes of the third flow member, each tube can be completely separate from the other tubes. The flow from or to the various tubes can be combined using a first flow member 118 and/or a second flow member 120 a that includes a single larger diameter tube that receives or directs the flow to all of the tubes of the plurality of tubes.

[0056] As illustrated in FIG. 3, each third flow member 122 includes one or more pipes or tubes 132 arranged in a serpentine path 302 (also shown in FIG. 4) that extends between the first flow member 118 and the second flow member 120. In the construction illustrated in FIG.

3 and FIG. 4, each tube 132 (only one shown in FIG. 4) follows a serpentine path 302 that includes three 180-degree turns with other numbers of turns being possible (e.g., one, five, seven, etc.). An end cap 304 is positioned at each 180-degree turn and operates like a manifold to receive the flow from the tubes 132 traveling in one direction and to redirect that flow into the tubes 132 flowing in the opposite direction. This arrangement allows for the use of straight tubes 132 rather than tubes 132 with actual bends formed therein. However, both straight and bent tube arrangements are possible.

[0057] As should be apparent, other arrangements of the tubes 132 and the serpentine path 302 may include different turns (e.g., 45-degree, 90-degree, etc.), fewer than three 180-degree turns, or more than three 180-degree turns, or any combination thereof. In addition, bent tubes 132 could be employed rather than straight tubes 132. It should be clear that the serpentine path 302 can be any length or arrangement desired and is selected to achieve the desired level of current flow and heat transfer as will be discussed in greater detail. In addition, the first flow members 118, second flow members 120, and/or third flow members 122 may be surrounded by thermal insulation (not shown) to direct the generated heat into the process fluid and improve the thermal efficiency.

[0058] Returning to FIG. 1, the primary winding 102, including the first phase winding 106, the second phase winding 108, and the third phase winding 110 includes a number of primary coils that each extend around their respective core bars. Similarly, the secondary winding 104, including the first continuous flow path 112, the second continuous flow path 114, and the third continuous flow path 116 includes a number of first flow members 118, second flow members 120, and power connectors 306 that cooperate to define secondary coils in the form of continuous flow paths. The number of primary coils and the number of secondary coils are selected to allow for the passage of the desired current, at the desired voltage in the primary winding 102 as well as the generation of the desired current and voltage in the secondary winding 104.

[0059] For example, in one arrangement there are significantly more primary coils than there are secondary coils resulting in a step-down transformer arrangement. Thus, the secondary voltage of the secondary winding 104 is significantly reduced when compared to the primary voltage of the primary winding 102. Similarly, the secondary current in the secondary winding 104 is greatly increased when compared to the primary current in the primary winding 102.

[0060] With reference to FIG. 3 and FIG. 4, the operation of the electric heater 100 will be described in greater detail. It should be noted that FIG. 3 illustrates a three-phase arrangement while FIG. 4 illustrates only one phase of the arrangement of FIG. 1. The description of FIG. 3 is applicable to each phase in arrangements that employ a multi-phase arrangement.

[0061] A flow of fluid 402 is introduced into the secondary winding 104 via the inlet 128.

The flow of fluid 402 can include any suitable fluid including, but not limited to water, brines, or molten salts and is selected based on the desired process being supported. The flow of fluid 402 flows through the secondary winding 104 by first entering the inlet manifold 124 and then entering one of the first flow members 118. From the first flow members 118, the flow of fluid 402 enters the third flow member 122 associated with the particular first flow member 118 and flows through one of the tubes 132 to one of the uppermost end caps 304 where the flow of fluid 402 makes a 180-degree turn and enters another tube 132 flowing downward. The flow of fluid 402 is once again turned 180 degrees in a lowermost end cap 304, returned upward via another set of tubes 132, turned again 180 degrees via another end cap 304 before finally entering a set of tubes 132 that direct the flow of fluid 402 downward and into the second flow member 120 of the particular continuous flow path associated with the first flow member 118. The flow of fluid 402 passes through the second flow member 120, enters the outlet manifold 126 and ultimately exits the secondary winding 104 via the outlet 130.

[0062] The primary winding 102 includes a plurality of coils or windings with each coil wrapped around one of the first core bar 210, the second core bar 212, or the third core bar 214. An electrical power is applied to the primary winding 102 at a primary voltage and current. As noted, the power level of the electrical power applied to the primary winding 102 is in the range of 1 MW to 1000 MW.

[0063] In operation, power is applied to the primary winding 102 to induce a similar power via the core 200 in the secondary winding 104. The number of coils in the primary winding 102 and the number of first flow members 118 and second flow member 120 are selected to arrive at the desired voltage and current levels in the secondary windings 104 for a given voltage and current in the primary winding 102. For example, if the primary winding operates at 45 kV and passes a primary current of 25 A, the power level would be about 1.1 MW. If the ratio of coils between the primary winding 102 and the secondary winding 104 is 100 to 1 the resulting voltage of the secondary winding 104 would be about 450 volts with a secondary current flow of about 2500 A, with the current divided between the various parallel continuous flow paths. The large current passing through the continuous flow paths of the secondary winding 104 heats the first flow member 118, the second flow member 120, and the third flow member 122 which in turn heats the flow of fluid 402 within the continuous flow paths. The extra length of the third flow member 122 produced by including multiple bends (three 180- degree bends in the illustrated example) results in additional heating of the flow of fluid 402. In addition, different lengths, tube counts, tube sizes, number of tube bends, and the like can be used to select the level of heating provided to the flow of fluid 402 for a particular electric heater 100. Thus, the electric heater 100 can be sized to produce a desired quantity of fluid at a desired temperature.

[0064] To assemble the electric heater 100, the core 200 is first assembled by stacking a plurality of laminations 202 in a stackwise direction. For the illustrated construction, the stackwise direction is vertical but other arrangements are possible. The laminations are formed and stacked as is well known in the art of large electric machines and transformers. The primary winding 102 is then positioned around the core as desired. If a single-phase heater is employed, a single primary winding 102 is applied to the core 200. In multi-phase arrangements, the primary winding 102 may include multiple phase windings such as a first phase winding, a second phase winding, and a third phase winding. The number of coils in each phase winding is selected in conjunction with the number of coils (continuous flow paths) in the secondary winding 104 to achieve the desired secondary voltage and secondary current at the secondary winding 104.

[0065] The first flow members 118 and the second flow members 120 are next positioned around the core 200 and around the primary winding 102. The first flow members 118 are connected to the inlet manifold 124 and the second flow members 120 are attached to the outlet manifold 126. In some constructions, the inlet manifold 124 and the outlet manifold 126 are connected to one another to allow the first flow members 118, the second flow members 120, the inlet manifold 124, and the outlet manifold 126 to be installed as one piece with the inlet manifold 124 and the outlet manifold 126 positioned below the core 200 and the open second ends of the first flow members 118 and the second flow members 120 positioned near or above the top of the core 200.

[0066] The third flow members 122 are assembled separately with two open ends (an inlet and an outlet near there lowermost end. The third flow members 122 are then attached to the open ends of the first flow members 118 and the second flow members 120 to complete the continuous flow paths and the secondary winding 104.

[0067] The arrangement illustrated herein is advantageous from a service perspective for a number of reasons. The tubes 132 of the third flow members 122 are the most likely components to wear and require periodic maintenance. These items are placed at the top of the electric heater 100 in a position that allows for their easy removal. The next most likely components that might require maintenance would be the first flow members 118, the second flow members 120, the inlet manifold 124, and the outlet manifold 126. These are also easily removable with minimal disassembly of other components. Finally, the more difficult to access components, namely, the core 200 and the primary winding 102 are the only components that would require disassembly of other components to access and repair or replace. Thus, the illustrated arrangement is easy to maintain and repair.

[0068] FIG. 5 illustrates a flow- through electric heater 500 that is similar to the constructions described with regard to FIG. 1 through FIG. 4. The flow-through electric heater 500 includes a primary winding 502 formed around a core 522 much like that described with regard to FIG. 4 and a secondary winding 504 positioned adjacent the primary winding 502 and the core 522.

[0069] The secondary winding 504 includes a first flow-through member 506, a second flow- through member 508, an upper connector 510, and a lower connector 512 that cooperate to form a complete winding. In the illustrated construction, the first flow-through member 506 and the second flow-through member 508 are substantially the same and include one or more inlets 514 at a first end of the flow- through electric heater 500, and one or more outlets 516 at the opposite end of the flow-through electric heater 500. In the illustrated construction, the inlets 514 are located at the lowermost end of the flow-through electric heater 500 but they could be positioned at the upper end if desired. Similarly, the position of the outlets 516 could be reversed if desired.

[0070] Each of the first flow-through member 506 and the second flow-through member 508 are surrounded by thermal insulation 518 to improve the efficiency of the heating process. In addition, support members 520 are positioned periodically along the vertical direction to provide additional support for the components of the flow-through electric heater 500. A cover 524 may also be provided to protect the internal components from the environment. [0071] The flow-through electric heater 500 operates in a manner similar to that described for the electric heater 100 described previously. When power is applied to the primary winding 502 a current is induced in the secondary winding 504. The current flows through the first flow-through member 506 and the second flow-through member 508, causing them to be heated with the current flowing between the first flow-through member 506 and the second flow- through member 508 via the upper connector 510 and the lower connector 512.

[0072] A fluid to be heated is introduced into the first flow- through member 506 and the second flow-through member 508 through the inlets 514. As the fluid passes through each of the first flow-through member 506 and the second flow-through member 508 it is heated by the heat generated by resistance to the current passing through the secondary winding 504. The fluid then exits the first flow-through member 506 and the second flow-through member 508 through the outlets 516. In the illustrated construction, each of the first flow-through member 506 and the second flow-through member 508 includes two inlets 514 that feed four individual pipes within each of the first flow-through member 506 and the second flow-through member 508 before exiting through four separate outlets 516. It should be noted that the number of inlets 514, number of pipes, and number of outlets 516 can vary and are not critical to the invention. Rather, the quantity of inlets 514, outlets 516, and pipes is selected for convenience, efficiency, and other parameters.

[0073] The flow-through electric heater 500 includes a complete secondary winding 504 without any pipes or other components attached to the top of the first flow- through member 506 and the second flow-through member 508. Thus, serpentine pipes, as illustrated in FIG. 1 through FIG. 4 could be included if desired. In addition, pipes that may not be electrically conductive could be attached if desired as these pipes form no part of the secondary winding 504. Additionally, the outlets 516 could be connected to various other components or pipes where the flow of current is undesirable.

[0074] FIG. 6 illustrates another arrangement of a toroidal electric heater 600 that operates in a manner similar to the stacked lamination core constructions described in FIG. 1 through FIG. 5. In the arrangement of FIG. 6, a magnetic core 606 is constructed by winding one or more strips of magnetic laminations to form an oval, rounded rectangle or “racetrack” shape. The wound core 606 has a length direction oriented parallel to the long axis of the pipes 610, (i.e. into the plane of FIG. 6). The length of the core 606 for each lamination into the plane of FIG. 1 can be 50 to 150 cm with other lengths being possible. Several core modules 612, each defined by stacking one or more laminations in the length direction, can be stacked to extend the length of the core 606 as may be required for the particular application.

[0075] With continued reference to FIG. 6, two core modules 612 are positioned adjacent one another with a long side of one of the core modules 612 positioned adjacent a similar long side of the other core module 612 to define a central core bar 614 with two apertures 616; one on either side of the core bar 614.

[0076] A primary winding 602 extends around the central core bar 614 to form a closed primary winding 602. A secondary winding 604, in the form of flow piping 604 also forms a closed electrical circuit around the central core bar 614.

[0077] Thermal insulation 608 is positioned around the secondary winding 604 to thermally separate the secondary winding 604 from the primary winding 602 and the laminations that make up the core modules 612. During operation, electrical current in the primary winding 602 induces a current in the secondary winding 604 and in particular in the pipes 610. The current in the secondary winding 604 heats the pipes 610 and any fluid flowing therethrough. The thermal insulation 608 protects the primary winding 602 and the core modules 612 from this heat.

[0078] The electric heaters described herein are well-suited to efficient operation at very high power levels greater than 1 MW and up to about 1000 MW. In addition, the arrangements are inexpensive to produce and are such that maintenance is easy.

[0079] FIG. 7 illustrates another arrangement of an electric heater in the form of a singlephase heater 700. Before proceeding, it should be noted that the term “single-phase heater” means that the primary winding is provided as a single phase that is connected to a single-phase power supply or a single phase of a multi-phase power supply. Thus, a single-phase heater 700 such as the one illustrated in FIG. 7 could be used with a single-phase power supply. In addition, if a three-phase power supply is available, three single-phase heaters 700 such as the one illustrated in FIG. 7 could be employed with each single-phase heater 700 having a primary winding 706 fed by one of the available phases of power. Thus, multiple independent singlephase heaters 700 can be used in conjunction with a single multi-phase or three-phase power supply. Of course, a single core having three phase windings similar to that illustrated in FIG. 1 could also be employed with a multi-phase or three -phase power supply.

[0080] With reference to FIG. 7, the single-phase heater 700 includes a core 702, a primary winding 706, and a secondary winding 708. The core 702 includes a plurality of laminations stacked in a stackwise direction 716 to a desired height or length. The core 702 defines a core envelope 704 which surrounds the laminations and may extend slightly beyond the laminations. Generally, the core envelope 704 is the area that contains the laminations and may extend to a point at which the core's magnetic field remains strong enough to function as a magnetic core. The shape of the laminations and thus the core 702 is selected for the desired design with the illustrated core 702 having a central bar 726 and two outside bars 728. Each outside bar 728 cooperates with the central bar 726 to define a core aperture 730 therebetween. Thus, the core 702 looks much like the core 200 and is capable of operating as a single-phase core or a three- phase core as may be desired.

[0081] The primary winding 706 includes a plurality of wires, bars, or other conductors capable of carrying the desired amount of power (e.g., 1-1000 MW and preferably 10-100 MW) in the form of a flow of primary current 732. As illustrated in FIG. 7, the primary winding 706 includes one or more loops that extend around the central bar 726 such that a portion of each loop is disposed within each of the core apertures 730 and most if not all the primary winding 706 is disposed within the core envelope 704. As discussed, the primary winding 706 is connected to a power supply that operates to provide the desired power.

[0082] The secondary winding 708 includes a core flow member 710 and an external flow member 712 that connect to one another to define a continuous flow path 724 for both a flow of fluid 714 and a flow of secondary current 734. The core flow member 710 includes one or more pipes arranged in a U-shape such that most, if not all of the core flow member 710 is disposed within the core envelope 704. Specifically, the core flow member 710 includes two lengths of pipe that extend in the stackwise direction and are disposed within the core apertures 730.

[0083] The external flow member 712 includes one or more pipes or tubes arranged in a serpentine pattern. The number, size, length, and arrangement of the pipes of the external flow member 712 are selected to achieve the desired level of heating of the flow of fluid 714. [0084] One end of the external flow member 712 connects to the core flow member 710 via a power connector 722. The power connector 722 allows for the flow of fluid 714 to pass and also acts as a conductor to assure that the core flow member 710 and the external flow member 712, when connected form a closed circuit. A second end of the external flow member 712 connects to the core flow member 710 and defines an inlet 718 and an outlet 720. Each of the inlet 718 and the outlet 720 may be formed as part of the core flow member 710 or the external flow member 712 or may be formed as a single part, or two separate parts that attach to the core flow member 710 or the external flow member 712. While the flow of fluid 714 does not flow past the outlet 720 and back to the inlet 718, the inlet 718 and the outlet 720 must be electrically connected to one another to allow for the formation of a closed circuit and the flow of secondary current 734.

[0085] In operation, the single-phase heater 700 of FIG. 7 receives power from a single-phase power supply or receives a single phase from a multi-phase power supply and directs that power to the primary winding 706 which results in the flow of primary current 732.

[0086] The flow of primary current 732 in the primary winding 706 produces a magnetic field in the core 702 which in turn, induces a flow of secondary current 734 in the secondary winding 708. Thus, the only interaction between the primary winding 706 and the secondary winding 708 occurs as a result of the magnetic interaction between the primary winding 706, the secondary winding 708, and the core 702.

[0087] The flow of secondary current 734 flows along the closed circuit or continuous flow path 724 defined by the inlet 718, the core flow member 710, the power connector 722, the external flow member 712, and the outlet 720 and heats the pipes that define the core flow member 710 and the external flow member 712.

[0088] The flow of fluid 714 is introduced into the secondary winding 708 at the inlet 718 and flows through the core flow member 710, the power connector 722, and the external flow member 712 before exiting the secondary winding 708 at the outlet 720. As the flow of fluid 714 flows through the secondary winding 708 it is heated by the various pipes in which it flows.

[0089] Although an exemplary embodiment of the present disclosure has been described in detail, those skilled in the art will understand that various changes, substitutions, variations, and improvements disclosed herein may be made without departing from the spirit and scope of the disclosure in its broadest form.

[0090] None of the description in the present application should be read as implying that any particular element, step, act, or function is an essential element, which must be included in the claim scope: the scope of patented subject matter is defined only by the allowed claims.

Moreover, none of these claims are intended to invoke a means plus function claim construction unless the exact words "means for" are followed by a participle.

Claims

CLAIMS What is claimed is:

1. An electric heater comprising: a core having a first end and a second end spaced apart from the first end in a stackwise direction to define a core envelope; a primary winding positioned around and magnetically coupled to the core, the primary winding operable at a power level greater than 1 MW to produce a flow of primary current; a core flow member magnetically coupled to and positioned to surround a portion of the core; an external flow member positioned outside of the core envelope and connected to the core flow member to define a continuous flow path between an inlet and an outlet, the core flow member and the external flow member cooperating to define a secondary winding; a flow of fluid delivered to the inlet and collected from the outlet, the flow of fluid being heated in response to a flow of secondary current in the secondary winding which is induced by the flow of primary current.

2. The electric heater of claim 1, wherein the core includes a plurality of laminations stacked in the stackwise direction, the laminations arranged to define a central bar, a first outside bar, and a second outside bar, and wherein the primary winding surrounds the central bar and passes through a first core aperture between the central bar and the first outside bar and a second core aperture between the central bar and the second outside bar.

3. The electric heater of claim 2, wherein the core flow member surrounds a portion of the central bar and extends through the first core aperture and the second core aperture.

4. The electric heater of claim 1 , wherein the inlet and the outlet are disposed outside of the core envelope.

5. The electric heater of claim 1, wherein the external flow member includes a plurality of continuous pipes, each pipe arranged along a serpentine path.

6. The electric heater of claim 1 , wherein the core defines a first core bar, a second core bar, and a third core bar, and wherein the first core bar and the second core bar cooperate to define a first core aperture and the second core bar and the third core bar cooperate to define a second core aperture, and wherein the primary winding includes a first phase winding that extends around the first core bar, a second phase winding that extends around the second core bar, a third phase winding that extends around the third core bar, and wherein the secondary winding includes a first continuous flow path that extends around the first core bar, a second continuous flow path that extends around the second core bar, and a third continuous flow path that extends around the third core bar.

7. The electric heater of claim 1, wherein the power level is between 10 MW and 100 MW.

8. The electric heater of claim 1, wherein the core includes a first core portion that defines a first core aperture and a second core portion separate from the first core portion that defines a second core aperture, the first core portion and the second core portion positioned adjacent one another, a portion of the first core portion and a portion of the second core portion cooperating to define a central bar, the primary winding positioned to surround the central bar.

9. The electric heater of claim 1 , wherein the first core portion is made from a continuous strip of magnetic material wound to form an oval first core portion.

10. The electric heater of claim 1 , wherein the core includes a central bar, a first outside bar, and a second outside bar, and wherein the primary winding surrounds the central bar and passes through a first core aperture between the central bar and the first outside bar and a second core aperture between the central bar and the second outside bar, and wherein the core flow member surrounds a portion of the central bar and extends through the first core aperture and the second core aperture, the core, the primary winding, and the secondary winding cooperating to define a single-phase heater.

11. The electric heater of claim 10, wherein the single-phase heater is a first singlephase heater, the electric heater further comprising a second single-phase heater separate from the first single-phase heater and a third single-phase heater separate from the first single-phase heater and the second single-phase heater, and wherein a first phase of a three-phase power supply delivers power to the primary winding of the first single-phase heater, a second phase of the three-phase power supply delivers power to the primary winding of the second single-phase heater, and a third phase of the three-phase power supply delivers power to the primary winding of the third single-phase heater.

12. The electric heater of claim 1, wherein the sole interaction between the primary winding and the secondary winding is a result of a magnetic interaction with the core.

13. A method of heating a flow of fluid, the method comprising: applying a primary winding to a core having a core envelope; positioning a secondary winding adjacent the core, the secondary winding including a core flow member that surrounds a portion of the core and an external flow member positioned outside of a core envelope, the core flow member and the external flow member cooperating to define a continuous flow path between an inlet and an outlet; directing the flow of fluid to the inlet, through the continuous flow path, and out the outlet; directing a flow of primary current to the primary winding, the flow of primary current having a primary voltage that results in a power level of at least 1 MW; inducing a flow of secondary current in the secondary winding in response to the flow of primary current; heating the secondary winding in response to the flow of secondary current; and heating the flow of fluid in response to the heating of the secondary winding.

14. The method of claim 13, further comprising stacking a plurality of laminations in a stackwise direction, and wherein each lamination is formed from a magnetic material.

15. The method of claim 13, further comprising forming the core from a continuous strip of magnetic material wound in a toroidal shape. 1

16. The method of claim 13, further comprising providing a core that includes a first core bar, a second core bar, and a third core bar, and wherein the first core bar and the second core bar cooperate to define a first core aperture and the the second core bar and the third core bar cooperate to define a second core aperture, winding a first phase winding of the primary winding around the first core bar, a second phase winding of the primary winding around the second core bar, a third phase winding of the primary winding around the third core bar, and positioning a first continuous flow path of the secondary winding around the first core bar, a second continuous flow path of the secondary winding around the second core bar, and a third continuous flow path of the secondary winding around the third core bar.

17. The method of claim 13, further comprising forming the core to include a central bar, a first outside bar, and a second outside bar, and wherein the applying the primary winding step includes surrounding the central bar and passing the primary winding through a first core aperture between the central bar and the first outside bar and a second core aperture between the central bar and the second outside bar, and wherein the positioning the secondary winding step includes surrounding a portion of the central bar and extending the secondary winding through the first core aperture and the second core aperture, the core, the primary winding, and the secondary winding cooperating to define a single-phase heater.

18. The method of claim 17, further comprising connecting the single-phase heater to a first phase of a three-phase power supply, connecting a second single-phase heater to a second phase of the power supply, and connecting a third single-phase heater to a third phase of the power supply, the single-phase heater, the second single-phase heater, and the third singlephase heater separate from one another.

19. The method of claim 13, operating the electric heater at a power level between 10 MW and 100 MW.

20. The method of claim 13, wherein the secondary winding includes a core flow member and an external flow member, and wherein the positioning a secondary winding step includes positioning the core flow member to surround a portion of the core and attaching the external flow member to the core flow member to define the continuous flow path between the inlet and the outlet, the external flow member disposed outside of the core envelope.

21. The method of claim 20, further comprising forming the external flow member to include a serpentine path.

22. An electric heater comprising: a core oriented to define a first surface and a second surface opposite the first surface; a primary winding positioned adjacent the core and operable at a power level greater than 1 MW to produce a flow of primary current; a first flow member extending around a first portion of the core and defining an inlet; a second flow member extending around a second portion of the core and defining an outlet, the second portion different than the first portion; a third flow member disposed adjacent the first surface and connected to the first flow member and the second flow member to complete a continuous flow path between the inlet and the outlet, the first flow member, the second flow member, and the third flow member cooperating to define a portion of a secondary winding; and a flow of fluid delivered to the inlet and collected from the outlet, the flow of fluid being heated in response to a flow of secondary current in the secondary winding which is induced by the flow of primary current.

23. The electric heater of claim 22, wherein the primary winding, the core, and the secondary winding are arranged adjacent to one other and interact via a magnetic field.

24. The electric heater of claim 22, further comprising a power connector connected to the first flow member and the second flow member.

25. The electric heater of claim 22, wherein the core includes a plurality of laminations stacked in a first direction, and wherein each lamination is formed from a magnetic material.

26. The electric heater of claim 22, wherein the core is made from a continuous strip of magnetic material wound to form a toroidal core.

27. The electric heater of claim 22, wherein the core defines three core bars and two core apertures, wherein the primary winding includes a first phase winding that extends around a first core bar, a second phase winding that extends around a second core bar, a third phase winding that extends around a third core bar, and wherein the secondary winding includes a first continuous flow path that extends around the first core bar, a second continuous flow path that extends around the second core bar, and a third continuous flow path that extends around the third core bar.

28. The electric heater of claim 22, wherein the core includes a central core bar, a first outside bar and a second outside bar, the central bar cooperating with the first outside bar to define a first core aperture and cooperating with the second outside bar to define a second core aperture, and wherein the primary winding includes a single phase winding that extends around the central core bar, and wherein the secondary winding includes a first continuous flow path that extends around the central core bar, a portion of each of the primary winding and the secondary winding passing through each of the first core aperture and the second core aperture.

29. The electric heater of claim 22, wherein the power level is between 10 MW and 100 MW.

30. The electric heater of claim 22, wherein the third flow member includes a first tube arranged along a serpentine path that extends between the first flow member and the second flow member.

31. The electric heater of claim 22, wherein the third flow member further comprises plurality of tubes and a plurality of end caps, wherein each tube of the plurality of tubes is straight, and wherein the plurality of tubes and plurality of end caps cooperate to define a serpentine path that extends between the first flow member and the second flow member.

32. The electric heater of claim 22, further comprising an inlet manifold and an outlet manifold, and wherein the inlet of the first flow member is connected to the inlet manifold and the outlet of the second flow member is connected to the outlet manifold.

33. The electric heater of claim 32, wherein the first flow member is one of a plurality of first flow members, each first flow member including an inlet that is connected to the inlet manifold, and wherein the second flow member is one of a plurality of second flow members, each second flow member including an outlet that is connected to the outlet manifold.

34. The electric heater of claim 33, wherein the third flow member is one of a plurality of third flow members, each third flow member connected to a corresponding one of the first flow members and one of the second flow members to define one of a plurality of continuous flow paths, each of the continuous flow paths being fluidly isolated from the other of the continuous flow paths between but not including the inlet manifold and the outlet manifold.

35. The electric heater of claim 22, wherein the third flow member is removable from the first flow member and the second flow member without disassembly of the core and the primary winding.