A high power induction heater

Abstract

An electrical heating system includes a magnetic core at least partially surrounded by a primary winding sized to receive a quantity of power greater than 1 MW. A core secondary winding is formed from a material having a first electrical resistance, magnetically coupled to, and positioned to surround a portion of the core. An external secondary winding is positioned outside of the core and cooperates with the core secondary winding to define a secondary winding. The external flow member is formed from a material having a second electrical resistance that is higher than the first electrical resistance, and a flow of fluid passes over an outer surface of the external secondary winding, where the external secondary winding is heated in response to the receipt of the quantity of power, and in turn heats the flow of fluid.

Description

Docket No. 2024ID00776AEA HIGH POWER INDUCTION HEATERBACKGROUND

[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 electrical heating system includes a magnetic core at least partially surrounded by a primary winding sized to receive a quantity of power greater than 1 MW. A core secondary winding is formed from a material having a first electrical resistance, magnetically coupled to, and positioned to surround a portion of the core. An external secondary winding is positioned outside of the core and cooperates with the core secondary winding to define a secondary winding. The external flow member is formed from a material having a second electrical resistance that is higher than the first electrical resistance, and a flow of fluid passes over an outer surface of the external secondary winding, where the external secondary winding is heated in response to the receipt of the quantity of power, and in turn heats the flow of fluid.Docket No. 2024ID00776AEBRIEF DESCRIPTION OF THE DRAWINGS

[0004] 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.

[0005] FIG. l is a perspective view a high-power electric heater operable to heat a flow of fluid.

[0006] FIG. 2 is a perspective view of a core for use in the electric heater of FIG. 1.

[0007] FIG. 3 is a section view of the electric heater of FIG. 1.

[0008] FIG. 4 is a schematic illustration of the electric heater of FIG. 1.

[0009] FIG. 5 illustrates an arrangement of a high-power electric heater operable to heat a flow of fluid.

[0010] FIG. 6 illustrates another arrangement of a high-power electric heater having a toroidal core and operable to heat a flow of fluid.

[0011] FIG. 7 illustrates another arrangement of a high-power electric heater.

[0012] FIG. 8 illustrates an electric heater arranged to heat a secondary fluid flowing through a duct.

[0013] FIG. 9 illustrates an electric heater arranged to heat a secondary fluid in a reaction vessel.

[0014] FIG. 10 illustrates an electric heater arranged to heat a secondary fluid in a boiler.

[0015] FIG. 11 illustrates an electric heater arranged to heat a secondary fluid with a bypass connector.

[0016] FIG. 12 illustrates an electrical heating system arranged to heat an external flow of fluid.

[0017] FIG. 13 illustrates a heating system including three of the electrical heaters of FIG. 12.Docket No. 2024ID00776AE

[0018] FIG. 14 illustrates the heating system of FIG. 13 with multi-conductor core secondary windings and external secondary windings.DETAILED DESCRIPTION

[0019] 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.

[0020] 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.

[0021] 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 termedDocket No. 2024ID00776AE a first element, information, function, or act, without departing from the scope of the present disclosure.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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 aDocket No. 2024ID00776AE 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] In the illustrated construction, the inlet manifold 124 is a cylindrical pipe or tube that may be closed at one end and defines an inlet 128. 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.

[0030] 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 particularDocket No. 2024ID00776AE 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.

[0031] In the illustrated construction, the outlet manifold 126 is a cylindrical pipe or tube that may be closed at one end and defines an outlet 130. 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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 theDocket No. 2024ID00776AE 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.

[0037] 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.

[0038] 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.

[0039] 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 primaryDocket No. 2024ID00776AE 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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 operatesDocket No. 2024ID00776AE 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.

[0044] 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.

[0045] 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 secondDocket No. 2024ID00776AE ends of the first flow members 118 and the second flow members 120 positioned near or above the top of the core 200.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.Docket No. 2024ID00776AE

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.Docket No. 2024ID00776AE

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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 700Docket No. 2024ID00776AE 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.

[0060] 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.

[0061] 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.

[0062] 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 twoDocket No. 2024ID00776AE lengths of pipe that extend in the stackwise direction and are disposed within the core apertures730.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.Docket No. 2024ID00776AE

[0068] 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.

[0069] FIG. 8 illustrates an arrangement of a secondary fluid heater 800 that operates to heat a secondary fluid 814 using an electric heater similar to that described with regard to FIG. 1 through FIG. 7. Specifically, the electric heater includes a magnetic core 802, a primary winding 804, and a core flow member 806 and an external flow member 808 that cooperate to define a secondary winding. As discussed, the primary winding 804 includes an electrically conductive winding that partially surrounds the magnetic core. A current having a voltage that results in a power level of 1 MW or more passes through the primary winding 804 and induces a magnetic field in the magnetic core 802. The magnetic field in the core 802 induces a corresponding current in the secondary winding.

[0070] The secondary winding is formed from one or more pipes or tubes that define the core flow member 806 and a series of tubes or pipes that define the external flow member 808. The core flow member 806 and the external flow member 808 are manufactured from an electrically conductive material that allows for the flow of current induced by the operation of the primary winding 804. The material does provide a resistance to the flow of current which leads to heating of the core flow member 806 and the external flow member 808 in response to the flow of current.

[0071] A heating fluid 812 enters the core flow member 806 at an inlet 816, flows through a first side of the core flow member 806, flows through the external flow member 808, then flows through the remainder of the core flow member 806 before exiting at an outlet 818. The heating fluid 812 is heated during this process while simultaneously cooling the core flow member 806 and the external flow member 808. In some constructions, the heating fluid 812 includes water with other fluids such as air, molten salts and the like also being suitable.

[0072] Flow components 822 such as pumps, compressors, storage tanks, valves and the like may be positioned to deliver and recover the heating fluid 812 to and from the core flow member 806. For certain heating fluids 812 such as water or molten salts, a closed cycle mayDocket No. 2024ID00776AE be desirable. Thus, the flow components 822 may include some storage capacity, a pump, and various valving and controls. In other constructions, an open cycle may be possible. For example, the flow component 822 could include an air compressor that draws in atmospheric air and delivers it to the inlet 816. After being heated, the heated air may be discharged to the atmosphere from the outlet 818.

[0073] The external flow member 808 is positioned within a chamber 810 or duct such that a flow of secondary fluid 814 passes through, over, or around the external flow member 808 and is heated by the external flow member 808. In one construction, the secondary fluid 814 includes air or another gas, with suspended metallic particles including metallic and non- metallic particles. The suspended particles operate to carry away additional heat through contact with the external flow member 808 and the gas in which they are carried. The flow of secondary fluid 814 and the heating fluid 812 can be independent from each other such that each one can exist stand alone.

[0074] In one construction, the fluid used as the heating fluid 812 is the same or similar to the secondary fluid 814. For example, in one arrangement, the secondary fluid 814 is air and the heating fluid 812 is air. The heating fluid 812 is heated as it flows through the core flow member 806 and the external flow member 808 and is discharged via the outlet 818. However, rather than discharging the preheated air to the atmosphere, it is directed to the chamber 810 upstream of the external flow member 808. The preheated air mixes with any additional air and passes over the external flow member 808 to complete the heating process.

[0075] FIG. 9 illustrates another arrangement in which the chamber 810 is replaced with a reaction vessel 902. The reaction vessel 902 is positioned to contain most or all of the external flow member 808 and includes a reactant inlet 904, a product outlet 906, and a quantity of catalyst 912. One or more reactants 908 enter the reaction vessel 902 via the reactant inlet 904 with products 910 generated by a reaction exiting the reaction vessel 902 via the product outlet 906.

[0076] The electric heater of FIG. 9 operates in a manner similar to the electric heater described in FIG. 8 to heat the heating fluid 812 and the external flow member 808. The external flow member 808 in turn heats the catalyst 912 which facilitates the reaction betweenDocket No. 2024ID00776AE any reactants 908 to produce a desired product 910. The flow rate of the reactants 908 and the products 910 are selected to maintain a stable process at the desired temperature.

[0077] FIG. 10 illustrates another arrangement of a system for heating a secondary fluid 814 using an electric heater arrangement similar to that described with regard to FIG. 8. In the arrangement of FIG. 10, the external flow member 808 is positioned in a chamber in the form of a boiler 1002.

[0078] The boiler 1002 includes a bottom portion 1004 that receives a fluid in a liquid state via a liquid inlet 1008. The external flow member 808 heats the liquid to produce fluid in the vapor state. The fluid in the vapor state is contained in an upper portion 1006 of the boiler 1002 and exits the boiler 1002 via a vapor outlet 1010.

[0079] In some constructions, it is desirable to use an electric heater that does not provide heating fluid flow through the external flow member 808. FIG. 11 illustrates an arrangement of an electric heater similar to the one illustrated in FIG. 8 but including an external heating member 1102 in place of the external flow member 808 and a bypass channel 1104 disposed between the core flow member 806 and the external heating member 1102.

[0080] The bypass channel 1104 provides a flow path for the heating fluid 812 such that the core flow member 806 and the bypass channel 1104 cooperate to define a complete flow path for the heating fluid 812. Thus, the heating fluid 812 is able to cool the primary winding 804 and the core 802 but does not flow through the external heating member 1102.

[0081] The external heating member 1102 may include tubular or solid members arranged for the purpose of heating the secondary fluid. While heating fluid 812 does not flow to the external heating member 1102, electrical current from the core flow member 806 does flow to the external heating member 1102 such that the external heating member 1102 is heated by the electrical resistance. Thus, the bypass channel 1104 bypasses fluid flow but not electrical flow from the external heating member 1102.

[0082] For each of the constructions described herein and in particular those described with regard to FIG. 8 through FIG. 11, other features or enhancements could be provided to improve the desired performance. For example, heat transfer enhancements such as fins, ridges, and the like may be provided on internal or external surface to improve heat transfer.Docket No. 2024ID00776AE

[0083] In other constructions, systems or features may be included to provide internal cooling on the inside of the pipes or tubes of the external flow member 808 to control temperature.

[0084] It should be understood that FIG. 8 through FIG. 11 illustrate examples with a singlephase electric heater. However, other constructions could include two or more phases arranged adjacent one another to better heat the secondary fluid. In this arrangement, the sizing or arrangement of the various external flow members 808 could be adjusted to produce different heat flux in the axial or flow direction of the secondary fluid.

[0085] FIG. 12 illustrates an alternative arrangement for an electrical heating system 1200 that allows for the use of high power (e.g., greater than 1 MW) electrical supplies for use in heating a flow of fluid 1202.

[0086] The electrical heating system 1200 of FIG. 12 includes a magnetic core 1204, a primary winding 1206, a core secondary winding 1208, and an external secondary winding 1210 that cooperates with the core secondary winding 1208 to define a complete secondary winding. The core 1204 may be formed and arranged as described herein with regard to other arrangements. In many arrangements, the core 1204 is formed from a series of stacked laminations with each lamination being formed in a desired shape from a magnetic of ferromagnetic material such as iron, electrical steel, or carbon steel. The laminations are stacked in a stackwise direction to define a length of the core 1204. Of course, other arrangements or manufacturing techniques could be employed to form the core 1204 as may be desired.

[0087] The primary winding 1206 includes one or more conductors wound around the core 1204 and operable to receive a flow of electrical current. The flow of electrical current generates a magnetic field in the core 1204 which in turn induces a current or a power flow 1218 in the secondary winding and specifically in the core secondary winding 1208. The number of windings in the primary winding 1206 may be selected to control the voltage and current of the power flow 1218.

[0088] The core secondary winding 1208 illustrated in FIG. 12 includes one conductor for each winding of the core secondary winding 1208 with the core secondary winding 1208 including one or more windings. The core secondary winding 1208 may include solid conductors, hollow conductors or stranded wire conductors as may be desired.Docket No. 2024ID00776AE

[0089] The external secondary winding 1210 includes one or more conductors 1212 with each conductor 1212 following a serpentine path. The serpentine path assures that each conductor 1212 is longer than the core secondary winding 1208 with preferred arrangements having conductors 1212 being between two and one hundred times longer than the core secondary winding 1208. Of course, greater length differences could be achieved if desired.

[0090] Like the core secondary winding 1208, each of the conductors 1212 may include a solid conductor, hollow conductor, or stranded wire conductors as may be desired. The conductors 1212 are positioned adjacent to and parallel to one another such that the flow of fluid 1202 generally passes over adjacent conductors 1212 and not through multiple conductors 1212.

[0091] A first buss bar 1214 and a second buss bar 1216 are positioned between the core secondary winding 1208 and the external secondary winding 1210 and operate to distribute the power flow 1218 from the core secondary winding 1208 to each of the conductors 1212 of the external secondary winding 1210. Specifically, a first end of the 1208 and a first end of each of the conductors 1212 is electrically connected to the first buss bar 1214 and a second end of the core secondary winding 1208 and a second end of each of the conductors 1212 is attached to the second buss bar 1216 to complete an electrical circuit that defines the secondary winding.

[0092] Because the construction of FIG. 12 does not include a flow of fluid within any portion of the secondary winding, but in particular between the core secondary winding 1208 and the external secondary winding 1210 the two components can be greatly separated. In some constructions, the external secondary winding 1210 is separated from the core secondary winding 1208 by a distance equal to or greater than a length of the core 1204. In still other arrangements, the separation distance is between one meter and two hundred meters, with greater distances possible.

[0093] The material selected to form the core secondary winding 1208 is selected to have a first electrical resistance and the external secondary winding 1210 is formed from a material having a second electrical resistance that is higher than the first electrical resistance. The selection of materials provides for reduced heating of the core secondary winding 1208 as compared to the external secondary winding 1210 such that the electrical heating is focused in the external secondary winding 1210 to make heating the flow of fluid 1202 efficient.Docket No. 2024ID00776AE

[0094] In some construction, the external secondary winding 1210 is formed from multiple separate modules that or connected in series. This can greatly increase the surface area available for heating. In addition, the conductors 1212 may include heat transfer enhancing surfaces that further increase surface area or heat transfer between the conductors 1212 and the flow of fluid 1202. For example, fins could be formed or attached to the conductors 1212 to increase the surface area. In other constructions, dimples or bumps may be provided to increase surface area and turbulence to further enhance heat transfer..

[0095] FIG. 13 illustrates an arrangement in which three electrical heating systems 1200 as illustrated in FIG. 12 are arranged adjace3nt one another. With this arrangement, a three phase power supply can be used with a first phase of the three phase power supply providing a first quantity of power 1302 to a first electrical heating system 1200, a second phase of the three phase power supply providing a second quantity of power 1304 to a second electrical heating system 1200, and a third phase of the three phase power supply providing a third quantity of power 1306 to a third electrical heating system 1200. The three electrical heating systems 1200 are arranged such that the flow of fluid 1202 passes through only one of the external secondary winding 1210, the second external secondary winding 1314, and the third external secondary winding 1322. This arrangement allows for even heating of a large quantity of fluid. Of course, other arrangements could arrange the three electrical heating systems 1200 in series rather than in parallel as illustrated.

[0096] FIG. 14 illustrates the heating system of FIG. 13 with the individual conductor core secondary windings 1208, 1312, 1320 replaced with multi-conductor windings. Similarly, the individual conductors 1212 of the external secondary winding 1210, 1314, 1322 are replaced with multi-conductor windings. As one of ordinary skill will realize, one of the core secondary windings 1208, 1312, 1320 and the external secondary winding 1210, 1314, 1322 could be replaced with multi-conductor arrangements rather than both if desired.

[0097] The constructions illustrated in FIG. 12 through FIG. 14 allows for heating with power levels in the the megawatt range with heaters over one megawatt being preferred and heaters in the triple digit megawatt range being possible. In addition, the arrangement is particularly suited to heating a high volume of process media and heating that media to high temperatures. In addition, the system if well-suited to heating process media with a high dust concentration and without any metallic particles.Docket No. 2024ID00776AE

[0098] In addition to the foregoing advantages, the constructions illustrated in FIG. 12 through FIG. 14 provide additional advantages. For example, the components of the system are maintained below 150 °C and are not exposed to process fluid as the process fluid flows over the heated element instead of inside the heated element. This allows for the heating of a large volume of fluid as well as the handling of dusty media. In addition, the system is adaptable to any voltage (e.g., medium voltage range: 11-27 kV) and can operate at a high power density. Because there is no fluid within the secondary winding or heating elements, the system offers higher reliability, lower capital and operating costs.

[0099] The arrangement provides for a uniform distribution of heat transfer across the three phases, the capability to position the primary and heating exchangers in separate locations, providing greater flexibility in system design and installation. The positioning of the external secondary windings 1210 of each phase in parallel aids in balancing the load for each phase such that each phase provides a similar level of heating to the flow of fluid 1202.

[0100] 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.

[0101] 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

Docket No. 2024ID00776AECLAIMSWhat is claimed is:

1. An electrical heating system comprising: a magnetic core at least partially surrounded by a primary winding, the primary winding sized to receive a quantity of power greater than 1 MW; a core secondary winding formed from a material having a first electrical resistance, magnetically coupled to, and positioned to surround a portion of the core; an external secondary winding positioned outside of the core and cooperating with the core secondary winding to define a secondary winding, the external flow member formed from a material having a second electrical resistance that is higher than the first electrical resistance; and a flow of fluid passing over an outer surface of the external secondary winding, wherein the external secondary winding is heated in response to the receipt of the quantity of power, and in turn heats the flow of fluid.

2. The electrical heating system of claim 1, wherein the core secondary winding defines a first conductor length and the external secondary winding defines a second conductor length, and wherein the second conductor length is between two and one hundred times the first conductor length.

3. The electrical heating system of claim 1, wherein the external secondary winding follows a serpentine path.

4. The electrical heating system of claim 1, wherein the external secondary winding includes a plurality of conductors, each conductor spaced apart from the other conductors and including a first end and a second end.

5. The electrical heating system of claim 4, further comprising a first buss bar and a second buss bar, the core secondary winding having a first end connected to the first buss bar and a second end connected to the second buss bar, and wherein the first end of each of the conductors is connected to the first buss bar and the second end of each of the conductors is connected to the second buss bar.Docket No. 2024ID00776AE6. The electrical heating system of claim 4, wherein each conductor of the plurality of conductors is spaced apart from and parallel to an adjacent conductor of the plurality of conductors, and wherein each conductor follows a serpentine path between its respective first end and second end.

7. The electrical heating system of claim 4, wherein the core secondary winding includes a plurality of conductors separate from one another.

8. The electrical heating system of claim 4, wherein the core secondary winding includes a one and only one conductor.

9. The electrical heating system of claim 4, wherein the external secondary winding includes a plurality of conductor elements separate from and parallel to one another.

10. The electrical heating system of claim 4, wherein the external secondary winding includes one and only one conductor element.

11. The electrical heating system of claim 1, wherein the magnetic core and the primary winding receive the quantity of power from a first phase of a three phase power supply, and wherein the electrical heating system further comprises a second magnetic core and a second primary winding that receives a second quantity of power from a second phase of the three phase power supply and a third magnetic core and a third primary winding that receives a third quantity of power from a third phase of the three phase power supply.

12. The electrical heating system of claim 11, further comprising a second core winding and a second external secondary winding, the second external secondary winding being heated in response to the receipt of the second phase of the three phase power supply, and a third core winding and a third external secondary winding, the third external secondary winding being heated in response to the receipt of the third phase of the three phase power supply.

13. The electrical heating system of claim 12, wherein the external secondary winding, the second external secondary winding, and the third external secondary winding are arranged adjacent one another such that the flow of fluid passes through one and only one of the external secondary winding, the second external secondary winding, and the third external secondary winding.Docket No. 2024ID00776AE14. The electrical heating system of claim 1, wherein the core secondary winding and the external secondary winding are separated by a distance greater than a length of the magnetic core.

15. The electrical heating system of claim 1, wherein the core secondary winding and the external secondary winding are separated by a distance between one meter and two hundred meters.

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