Secondary winding of induction steam generator

Abstract

FIELD: heat engineering.SUBSTANCE: in the secondary winding of the induction steam generator, comprising a short-circuited pipe with a water inlet pipe and a steam outlet pipe, made from spiral-shaped segments of a smooth-walled pipe connected to each other, in the cavity of each segment there is an insert of a wire turbulator, made in the form of a core twisted from at least two wires, between which, at an angle of 35-80 degrees to the core, wire loops of smaller diameter wire are clamped, wherein the wire loops of the inserts are adjacent to the inner surface of the segments and are fixed thereon by spot welding along the edges of the cavity of each segment, in addition, the inserts of the wire turbulator at the ends of the cores are provided with clamps made in the form of a bar with a mounting hole, welded to the walls of the cavity of the segments or in the form of a hook, or in the form of a ring.EFFECT: increase in the intensity of water evaporation and heat exchange, a reduction in scale formation, and a reduction in the dimensions and weight of the secondary winding of the induction steam generator.11 cl, 10 dwg

Description

[0001] FIELD OF TECHNOLOGY

[0002] The invention relates to thermal power engineering, in particular to the design of induction steam generators, and can be used for efficient steam generation.

[0003] STATE OF THE ART

[0004] The prior art includes solutions for secondary windings of induction steam generators made in the form of smooth tubes made of an electrically conductive material, such as copper, copper alloys or steel, for example, RU 2752986 C1, IPC F22B 1 / 28 (2006.01); RU 2650996 C1; RU 2667833 C1.

[0005] Their common disadvantages are that when using a smooth tube in the secondary winding in a laminar flow of feedwater, when it is heated, a boundary layer is formed in the wall layer of the pipe, which is formed due to the surface boiling of water heated by the electromagnetic field of the primary winding, and which displaces the boiling liquid from the wall, which leads to a deterioration in heat transfer and, as a consequence, to local overheating, as well as accelerated scale deposition in places where vaporization occurs, i.e. over the entire area of ​​​​the winding.

[0006] Various design elements are known in the art that improve the rate of water evaporation in the pipes of direct-flow steam generators and the turbulent flow of the coolant within them. Practice has demonstrated their advantages and disadvantages, so when selecting these elements for a design, it is necessary to consider the specifics of their application to minimize the risk of scale formation and ensure efficient operation of the device.

[0007] Design solutions are known that are aimed at increasing the intensity of water evaporation in steam generator tubes, for example the solution (see invention) RU 2419029 C2, IPC F22B 37 / 18 (2006.01) F28F 1 / 40 (2006.01), F28F 13 / 08 (2006.01) entitled “STEAM GENERATOR PIPE, DIRECT-FLOW STEAM GENERATOR AND METHOD OF MANUFACTURING A STEAM GENERATOR PIPE”, where the steam generator tube is made with inserts in the form of a plurality of wires of the multi-thread type, helically adjacent to the inner wall of the tube.

[0008] Due to the difference in the heating principle of the coolant in the pipes of a straight-through steam generator running on hydrocarbon fuel, from the heating principle of the coolant in the pipes of the secondary winding of an induction steam generator, the coolant in the pipes is heated due to various physical processes.

[0009] In a once-through steam generator tube using a wire heat exchange intensifier, physical processes associated with heat exchange and tube wall corrosion occur when heated by hydrocarbon fuel due to the effects of fuel combustion products, water, and steam. These processes occur when the thermal energy generated during fuel combustion is transferred to the water through the tube walls, and the wire heat exchange intensifier (also called a turbulator in various sources and henceforth referred to as a turbulator) enhances heat exchange.

[0010] The combustion chamber walls of a straight-through steam generator typically use straight steam generator tubes with turbulators installed within them. These tubes are gas-tight welded together through bridges to form a flue gas duct surrounding the combustion chamber. These tubes are connected in parallel to allow the fluid to flow. These steam generators require a large amount of metal, are large in size, and consequently weigh significantly.

[0011] In direct-flow electric induction steam generators, a tubular secondary winding is used, made in the form of a coil, in which water is heated by electromagnetic induction, which simultaneously affects the secondary winding tube, the water in the secondary winding, and also the turbulator, which is an additional source of heating the water inside the pipe. The combined combination of turbulence created by the turbulator and the magnetic field has a strong effect on changing the physicochemical properties of water, the structure of hydrated ions and impurities, as well as reducing scale formation on the heating surface of the pipe cavity, i.e.:

[0012] - the rates of chemical reactions change due to the occurrence of competing reactions of dissolution and precipitation of dissolved salts,

[0013] - the formation and disintegration of colloidal complexes occurs,

[0014] - improves electrochemical coagulation with subsequent sedimentation and crystallization of salts.

[0015] These effects together lead to changes in water density, surface tension, viscosity, pH value and physicochemical parameters of processes occurring in water, including the dissolution and crystallization of inorganic salts dissolved in water.

[0016] As a result, the magnesium and calcium salts contained in the water lose their ability to form a dense deposit. Instead of calcium carbonate CaCO3, a more gentle, fine-crystalline polymorphic form of CaCO3 forms, structurally reminiscent of aragonite. This form either does not precipitate from the water at all, as crystal growth stops at the microcrystal stage, or precipitates as a finely dispersed suspension. The turbulator reduces the thickness of the boundary layer near the wall, which is the primary resistance to heat transfer.

[0017] Among other technical solutions for turbulators, a well-known technical solution is called "INSERT FOR TURBULATION OF LIQUID FLOW IN A TUBULAR ELEMENT" (see patent RU 2396500). The insert for turbulization of liquid flow in a tubular element is made of wire. It comprises a central rod of two thick wires twisted together and a plurality of loop elements between them, arranged radially around the axis of the central rod.

[0018] The loop elements are made of wire, either round or otherwise, such as rectangular, cross-section. The larger surface area of ​​the wire of the loop element is oriented primarily in a plane perpendicular to the axis of the central rod. The loop elements are made of approximately rectangular cross-section and alter the flow characteristics of the fluid, making the flow more turbulent and disordered.

[0019] Using these inserts results in multiple fragmentation and mixing of the flow passing through them. The boundary layer is disrupted very rapidly. Due to the vortex motion of the coolant, greater contact between the coolant and the heated surfaces occurs, facilitating heat transfer.

[0020] Induction steam generators with such inserts in the secondary winding pipes to turbulize the coolant flow inside them have not been identified.

[0021] Disclosure of invention

[0022] Brief description of drawings

[0023] Fig. 1 shows an electric induction steam-generating module with a tubular secondary winding of a serpentine shape and a turbulator in the cavity of the pipe.

[0024] Fig. 2 shows an electric induction steam-generating module with a tubular secondary winding of an oval spiral shape and a turbulator in the cavity of the pipe.

[0025] Fig. 3 shows an S-shaped secondary winding.

[0026] Fig. 4 shows an oval-shaped secondary winding.

[0027] Fig. 5 shows an S-shaped tubular segment.

[0028] Fig. 6 shows an oval-shaped tubular segment.

[0029] Fig. 7 shows a longitudinal section of a secondary winding segment, which shows a turbulator with fixing elements in the form of strips 9 with mounting holes 15.

[0030] Fig. 8 shows a longitudinal section of a secondary winding segment, which shows a turbulator with fixing elements in the form of a bar 9 with a mounting hole 15 and a counter hook 18.

[0031] Fig. 9 shows a longitudinal section of a secondary winding segment, which shows a turbulator with fixing elements in the form of a ring 17 and a hook 18.

[0032] Fig. 10 shows a cross-section of a tubular segment of a secondary winding with a turbulator.

[0033] 1 - Three-rod flat ferromagnetic core;

[0034] 2 - Ferromagnetic core rod;

[0035] 3 - Primary winding coils;

[0036] 4 - Tubular secondary winding assembly;

[0037] 5 - Wire turbulator assembly;

[0038] 6 - ​​Supply pipe (water);

[0039] 7 - Discharge pipe (steam);

[0040] 8 - Shunts;

[0041] 9 - Plank;

[0042] 10 - Cylindrical element;

[0043] 11 - Secondary winding turns;

[0044] 12 - S-shaped secondary winding tubular segment;

[0045] 13 - Tubular segment of secondary winding, 0-shape;

[0046] 14 - Welded connection of the strip with the inner surface of the pipe;

[0047] 15 - Mounting hole in the bar;

[0048] 16 - Wire turbulator insert;

[0049] 17 - Ring;

[0050] 18 - Hook;

[0051] 19 - Wire loop;

[0052] 20 - Tubular segment wall;

[0053] 21- Connecting the wire loop to the pipe wall by spot welding;

[0054] 22 - Turbulator core wires;

[0055] 23 - Turbulator core.

[0056] The technical result is an increase in the intensity of water evaporation and heat exchange in the secondary winding of an induction steam generator, a decrease in scale formation, a decrease in the dimensions and weight of the secondary winding while producing the same volume of steam with the same characteristics as in an induction steam generator with a secondary winding pipe of greater length, but of the same diameter and made of the same material, as well as an increase in the maintainability of the secondary winding of the induction steam generator.

[0057] The specified technical result is achieved by the secondary tubular winding of the induction steam generator, consisting of at least one tubular segment of a serpentine or oval shape, made of copper, or copper-based alloys, or aluminum, or aluminum-based alloys, or corrosion-resistant steel grades. Each secondary winding segment contains a wire turbulator insert 16 located within its cavity, occupying no more than 50% of the internal space of the tubular segment, which allows the coolant flow under pressure to pass through the cavity of the secondary winding tube.

[0058] The insert of the wire turbulator 16 is made in the form of a core 23, twisted from at least two wires 22, between which, at an angle of inclination of 35-80° (preferably 40-60°), loops 19 made of wire of a smaller diameter, preferably of a round cross-section, are clamped, but the use of shaped wire with a square, rectangular or triangular cross-section is not excluded, with the arrangement of loops in the core according to the principle of a multi-start thread, where the loops are helically bent on the inner wall of the pipe 20 in the direction towards the flow, which significantly contributes to the improvement of heat transfer, since it creates a swirl of the coolant flow, due to which the liquid phase is directed to the inner wall of the pipe 20 and uniformly wets it.

[0059] The diameter of the core wire is preferably selected equal to the thickness of the pipe wall, which ensures their equal heating and can be in the range from 1 mm to 4 mm.

[0060] The 19 wire loops can be placed in the core with variable angular pitch, which creates asymmetric flow and increases flow turbulence.

[0061] Wire turbulator insert 16 can have a different number of wire loops (from 300 to 1600 loops per linear meter), depending on the internal diameter of the pipe, cross-section and shape of the wire.

[0062] The diameter of the turbulator insert 16 is larger than the inner diameter of the pipe 20, but not more than 50%, which allows the loops to fit tightly to the inner surface of the pipe.

[0063] The turbulator inserts 16 have various insert locks 9 or 17 or 18 at the ends of the cores 23, which are necessary to fix the installation of the turbulizer insert 16 in a separate segment of the pipe 12, 13, or to fix the turbulator assembly 5 in the secondary winding assembly 4, as well as to connect the turbulator inserts 16 to each other inside the secondary winding 4. The turbulator inserts 16 do not affect the movement of the coolant flow in the secondary winding pipe.

[0064] Different clamps are selected depending on the power and performance of the steam generator. i.e. If the secondary winding pipe 4, consisting of segments 12 or 13, has a total length of up to 30 meters, then the turbulator inserts are secured by a welded joint 14 along the edges of the cavity 20 of segments 12 or 13 with strips 9, and if the secondary winding pipe, consisting of segments 12 or 13, has a total length of more than 30 meters, then the turbulator inserts 16 are sequentially connected to each other using a ring-hook connection, and additionally the wire loops 19 of the turbulator inserts are secured by spot welding 21 along the edges of the walls 20 in the cavity of each segment and at the ends of the secondary winding 4 the outer inserts of the turbulators 16 are fixed with strips 9 welded to the walls 20 of the pipe cavity.

[0065] Secondary windings, made from tubular segments of a serpentine 12 or oval 13 shape, are connected to each other by welding or by couplings for welding, forming a single secondary winding 4, which allows, in the event of a malfunction of one of the segments, to remove it and replace it with a new one, which affects the increased maintainability and durability of the secondary winding 4 as a whole.

[0066] The secondary winding tube, turbulator and all insert clamps are made of material with high electrical and thermal conductivity.

[0067] The materials from which the turbulator and insert retainers are made are similar to the materials of the tubular segments that make up the secondary winding as a whole, but do not exclude a combined design, in which the material of the tubular segment, the material of the turbulator insert and the insert retainers may have different compositions.

[0068] Design Description

[0069] The secondary tubular winding assembly 4 (see Fig. 3, Fig. 4) is part of the electric induction steam-generating module (see Fig. 1, Fig. 2), which contains a three-rod flat ferromagnetic core 1 with rods 2. Primary windings 3 in the form of coils connected to a 0.4 kV alternating current network are located on the rods.

[0070] The secondary winding of an induction steam generator, containing a short-circuited pipe with a water inlet pipe 6 and a steam outlet pipe 7, made of spiral segments of a smooth-walled S-shaped pipe 12 or O-shaped pipe 13, the turns of which contactlessly embrace the rods 2 with windings 3, are connected to each other by shunts 8 and are connected by cylindrical elements 10 of the same diameter as the pipe of the secondary tubular winding 4.

[0071] In the cavity of each segment of pipes 12 or 13, at least one turbulator insert 16 is placed, made in the form of a core 23, twisted from at least two wires 22, between which wire loops 19 made of smaller diameter wire are clamped at an angle of 35-80°, adjacent to the inner surface of the pipe 20 and having welded joints 21 with the surface of these pipes.

[0072] The insert locks on the longitudinal sections of the secondary winding segments, made at opposite ends of the cores, shown in Fig. 7 - Fig. 9, can be combined in the form of:

[0073] - hook 18 and ring 17,

[0074] - bar 9 and hook 18 or ring 17,

[0075] - strap 9 - strap 9.

[0076] At the ends of the outer pipe segments, the insert clamps are made in the form of a strip 9 with a mounting hole 15, welded to the core 23 and to the inner walls 20 of the pipe segment and thereby forming a welded joint 14.

[0077] Wire loops 19 can be placed in the core with variable angular pitch.

[0078] The diameter of the intensifiers 16 exceeds the internal diameter of the pipe 20 by no more than 50%.

[0079] Secondary pipe segments 12 or 13 can be connected to each other by welding or by welding couplings.

[0080] The material of the pipes and insert retainers can be copper or copper-based alloys, aluminum or aluminum-based alloys, corrosion-resistant steel grades, and the fixing elements can also be made from them.

[0081] Device operation:

[0082] Feed water is supplied through the pipe 6 into the cavity of the secondary winding 4 and when a voltage of 0.4 kV is applied to the primary winding, as a result of the electromagnetic induction process, the alternating magnetic field created by the primary winding induces a large induced electric current in the tubular secondary winding 4, which allows for instantaneous simultaneous heating of the entire heating area of ​​the secondary winding and all turbulators 5 built into its cavity, which affects the quality and speed of steam formation.

[0083] Additionally, applying a magnetic field to water flow increases the heat transfer coefficient by 1.5-3 times, depending on the intensity of the magnetic flux in this field. This occurs because the magnetic field acts on moving charges in the liquid, inducing an electric current and magnetic forces that lead to turbulence in the flow as water passes through a channel located within the magnetic field.

[0084] The coolant, consisting of water and steam, flows through the pipe 4 and, in contact with the heated wire loops 19 and the core 23 of the turbulator insert 16, the laminar flow changes to turbulent, resulting in an improvement in the rate of heat transfer throughout the entire volume of the coolant.

[0085] The coolant in the middle of the flow moves faster (according to the Dean vortex theory, based on the fact that in curved pipes, under the action of centrifugal force, a secondary flow is formed in the form of two counter-rotating vortices, which occurs due to the fact that the liquid has mass and moves faster in the middle of the flow than near the channel walls) and due to the fact that the coolant flow flows around the wire loops 19 and the core 23 of the turbulator 5, located in the center of the pipe, a more uniform distribution of the coolant temperature throughout its volume is ensured due to mixing the coolant flow from the pipe walls to the center and vice versa, which also leads to the destruction of the wall boundary layer, and at the outlet - to an increase in the efficiency of vaporization due to intense heat exchange between the steam and the walls of the pipe 20, as a result of which:

[0086] - heat exchange is intensified;

[0087] - the onset of boiling occurs at lower superheats than in a pipe with a smooth surface:

[0088] - heat transfer coefficient increases by 20-30%;

[0089] - reduces scale formation;

[0090] Then the heated water evaporates and the steam is discharged through pipe 7.

[0091] As a result, due to the combined effect of increasing the intensity of heat transfer at a given level of energy consumption, the use of a turbulator 5 in a tubular secondary winding 4 of an induction steam generator makes it possible to reduce the weight and dimensions of the secondary winding 4 and, accordingly, to reduce its cost by reducing the length of the pipe, and by reducing scale formation on the heating surface of the cavity of the pipe 20 to reduce the frequency of maintenance and downtime of the device, which also leads to cost savings.

[0092] Industrial applicability:

[0093] The secondary winding 4 can be manufactured on the same equipment that produces the secondary winding 4 from a smooth pipe for existing induction steam generators that do not have turbulators 5 inserted into the pipes.

[0094] To produce the claimed secondary windings 4, it is sufficient to additionally have means for pulling the turbulators.

[0095] The installation of the turbulator insert 16 into the tubular cavity of each tubular segment 12 or 13 of the secondary winding 4 is performed in the already manufactured segment 12 or 13 of a given shape and length using a secured winch with a cable, which has a hook at the end. The cable hook is passed through the cavity of the tubular segment 12, 13 and is hooked onto the mounting hole 15 of the bar 9 or the ring 17 and then, pulling the turbulator insert 16 through the cavity of the segment 12 or 13, it is placed along the entire length of the segment with a directed structure of loops towards the flow, so that the bars 9 on both sides or the ring 17 and the hook 18 are placed along the edges of the segment 12 or 13, but do not protrude beyond them.

[0096] EXAMPLES OF IMPLEMENTING AN ELECTRIC INDUCTION STEAM-GENERATING MODULE WITH A SECONDARY WINDING WITH A TURBULATOR

[0097] EXAMPLE 1

[0098] The 75 kW module is made of a single flat ferromagnetic core with three rods, with primary windings in the form of coils located on these rods and electrically insulated from them, with a tubular secondary winding of a serpentine shape, assembled from segments having turbulator inserts, each of which has a wire core twisted from two wires of a round cross-section of 2 mm, between which wire loops made of wire of a round cross-section of 1.2 mm are inserted.

[0099] On both sides of the turbulator, strips with mounting holes are installed, which, after installation of the turbulator insert, are rigidly fixed by welding along the edges of the walls in the cavities of the pipes of each segment.

[0100] Tubular segments, turbulator inserts and fixing elements are made of MNZh 5-1 alloy.

[0101] The turns of the secondary winding tube, located one above the other, are connected to each other by cylindrical elements made of MNZh 5-1 material, which have the same diameter, and are welded or soldered between these turns inseparably, and are also short-circuited between each other by means of eight vertical shunts made of the same alloy as the secondary winding.

[0102] Tube dimensions: length - 16 m instead of 24 m compared to the analog without a turbulator, outer diameter - 22 mm, wall thickness - 1.2 mm instead of 1.5 mm for the analog without a turbulator.

[0103] The total number of turns of the secondary winding was 4 units instead of 6 units, and the thermal coefficient was 51 kW / m 2 .

[0104] EXAMPLE 2

[0105] The 225 kW module is made of one flat ferromagnetic core with three rods, with primary windings in the form of coils located on these rods and electrically insulated from them, with a tubular secondary winding of an oval spiral shape, assembled from 7 segments with turbulator inserts, each of which consists of a wire core twisted from two round wires with a diameter of 2 mm, wire loops made of square wire of 1.2 mm.

[0106] The turbulators have a ring on one end and a hook on the opposite end, connected in series using a ring-hook connection. The wire loops of the turbulators are spot-welded to the edges of the cavity walls of each segment, and at the ends of the secondary winding, the outer turbulators are secured with strips with mounting holes welded to the walls of the pipe cavity.

[0107] The tubular segments and intensifier are made in a combined design, in which the segments are made of MNZh 5-1 alloy, and the turbulator inserts and fixing elements are made of stainless steel 08X18H10 (AISI 304).

[0108] The turns of the secondary winding sequentially cover all three rods connected to each other with the primary windings in the form of coils.

[0109] The tubular secondary winding has a tube length of 30m instead of 43m like the smooth tube counterpart, an outer diameter of 22mm and a wall thickness of 1.2mm instead of 1.5mm like the smooth tube counterpart.

[0110] The total number of turns of the secondary winding was 6 units instead of 8 units, as in the analogue with a smooth pipe, and the thermal coefficient was 52 kW / m 2 .

[0111] EXAMPLE 3

[0112] The 450 kW module is made of one flat ferromagnetic core with three rods, with primary windings in the form of coils located on these rods and electrically insulated from them, with a tubular secondary winding of an oval spiral shape assembled from 11 segments with turbulator inserts, each of which has a wire core twisted from three round wires with a diameter of 1.5 mm, wire loops made of rectangular wire with a thickness of 1 mm, having a ring on one side and a hook on the other side, sequentially connected to each other using the ring-hook connection type.

[0113] The wire loops of the turbulators are fixed by spot welding along the edges of the walls in the cavity of each segment, and at the ends of the secondary winding, the outer turbulators are fixed with strips with mounting holes welded to the walls of the pipe cavity.

[0114] Tubular segments, intensifier inserts and fixing elements are made of stainless steel 08X18H10 (AISI 304).

[0115] The turns of the secondary winding sequentially cover all three rods connected to each other with the primary windings in the form of coils.

[0116] The tubular secondary winding has a tube length of 46m instead of 64m as if it were in the smooth tube version with an outer diameter of 22mm and a wall thickness of 1mm.

[0117] The total number of turns of the secondary winding was 8 units instead of 11 units, as if it was in the version with a smooth pipe, and the thermal coefficient was 53.4 kW / m 2 .

[0118] It should be noted that theoretical calculation and practical experience show that with a thermal heat transfer coefficient of the inner wall of the tube of 50(±10%) kW / m 2 The secondary winding operates under normal load and can be operated around the clock.

Claims

1. A secondary winding of an induction steam generator comprising a short-circuited pipe with a water inlet pipe and a steam outlet pipe made of spiral-shaped segments of a smooth-walled pipe connected to each other, characterized in that in the cavity of each segment there is an insert of a wire turbulator made in the form of a core twisted from at least two wires, between which, at an angle of 35-80 degrees to the core, wire loops of smaller diameter wire are clamped, wherein the wire loops of the inserts are adjacent to the inner surface of the segments and are fixed thereto by spot welding along the edges of the cavity of each segment, in addition, the inserts of the wire turbulator at the ends of the cores are provided with clamps made in the form of a bar with a mounting hole welded to the walls of the cavity of the segments or in the form of a hook, or in the form of a ring.

2. The secondary winding according to paragraph 1, characterized in that the spiral segments are made in an S- or O-shape and are connected to each other by welding or by welding couplings.

3. The secondary winding according to paragraph 1, characterized in that the wire loops are placed in the core with a variable angular pitch.

4. The secondary winding according to paragraph 1, characterized in that the diameter of the wire turbulators exceeds the internal diameter of the pipe by no more than 50%.

5. The secondary winding according to paragraph 1, characterized in that when the secondary winding is less than 30 meters long, the insert clamps in each segment are made in the form of strips welded to the inner walls of each segment.

6. The secondary winding according to paragraph 1, characterized in that when the secondary winding is more than 30 meters long, the clamps of the inserts placed in the internal segments of the secondary winding are made in the form of a hook and a ring at opposite ends of the core with the possibility of connecting the segments in series with each other using the ring-hook connection type, and the clamps of the inserts in the segments placed at the ends of the secondary winding are made in the form of a hook or a ring at one end, and at the ends of the secondary winding the clamps of the outer turbulators are made in the form of strips with mounting holes welded to the inner walls of the outer segments along the edges of the winding.

7. The secondary winding according to paragraph 1, characterized in that the material of the tubes is copper or copper-based alloys, aluminum or aluminum-based alloys, corrosion-resistant steel grades.

8. The secondary winding according to paragraph 1, characterized in that the wire turbulator and the fixing elements are made of a material similar to the material of the winding segments.

9. The secondary winding according to paragraph 1, characterized in that the winding segments and wire turbulators with clamps are made of different materials.

10. The secondary winding according to paragraph 1, characterized in that the wires of the wire loops have a round cross-section.

11. The secondary winding according to paragraph 1, characterized in that the wires of the wire loops have a shaped cross-section, namely square, rectangular or triangular.

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