Electric heater and electric boiler

Abstract

To suppress reduction of life of an electric heater.SOLUTION: An electric heater 7A, which is immersed in water, includes: a pipe 23; a heat generation wire 25 arranged in the pipe 23; and an insulating material 27 arranged between the heat generation wire 25 and the pipe 23. A fin 32 is provided on the outside of the pipe 23.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The technology disclosed in this specification relates to an electric heater and an electric boiler. [Background technology]

[0002] 2. Description of the Related Art In the technical field relating to electric heaters, an electric heater used in an electric boiler, such as that disclosed in Patent Document 1, is known. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-169356 A Summary of the Invention [Problem to be solved by the invention]

[0004] The electric heater includes a pipe and a heating wire disposed inside the pipe. In an electric boiler, the electric heater is used while immersed in water. If the watt density of the electric heater increases and the surface temperature of the electric heater increases, the life of the electric heater may be shortened. Watt density refers to the electrical capacity per unit surface area of ​​the electric heater. If the watt density of the electric heater increases, for example, the heating wire may be overheated, the pipe may be susceptible to corrosion, or scale may be easily formed on the surface of the pipe. Scale refers to the deposit of hardness components in water.

[0005] The technology disclosed in this specification aims to prevent the life of an electric heater from being shortened. [Means for solving the problem]

[0006] The present specification discloses an electric heater that is immersed in water. The electric heater includes a pipe, a heating wire disposed inside the pipe, and an insulating material disposed between the heating wire and the pipe. Fins are provided on the outer surface of the pipe. Effect of the Invention

[0007] According to the technique disclosed in this specification, the shortening of the life span of an electric heater is suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a front view showing a schematic diagram of an electric boiler according to a first embodiment. [Diagram 2] FIG. 2 is a side view diagrammatically illustrating the electric boiler according to the first embodiment. [Diagram 3] FIG. 3 is a vertical cross-sectional view showing the heater device according to the first embodiment. [Figure 4] FIG. 4 is a cross-sectional view showing the electric heater according to the first embodiment. [Diagram 5] FIG. 5 is a cross-sectional view showing an electric heater according to the second embodiment. [Figure 6] FIG. 6 is a diagram showing a schematic diagram of a water pipe and an electric heater according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to the embodiment. The components of the embodiments described below can be appropriately combined. In addition, some components may not be used.

[0010] In the embodiment, a three-dimensional orthogonal coordinate system is defined, and the positional relationship of each part will be described with reference to the three-dimensional orthogonal coordinate system. The direction parallel to the X-axis in a horizontal plane is defined as the X-axis direction. The direction parallel to the Y-axis in a horizontal plane perpendicular to the X-axis is defined as the Y-axis direction. The direction parallel to the Z-axis perpendicular to the horizontal plane is defined as the Z-axis direction. The Z-axis direction is the up-down direction. The +Z side is the upper side, and the -Z side is the lower side.

[0011] [First embodiment] A first embodiment will be described.

[0012] <Electric boiler> Fig. 1 is a front view showing an electric boiler 1 according to the present embodiment. Fig. 2 is a side view showing an electric boiler 1 according to the present embodiment. Fig. 1 and Fig. 2 each show a part of the electric boiler 1 in cross section.

[0013] As shown in Figures 1 and 2, the electric boiler 1 comprises a water supply device 2, a lower header 3 connected to the water supply device 2, a plurality of water tubes 4 connected to the lower header 3, a plurality of riser pipes 5 connected to each of the plurality of water tubes 4, an upper header 6 connected to the riser pipes 5, a heater device 8 including an electric heater 7A arranged inside the water tubes 4, and a water level detection device 9 for detecting the water level of the water tubes 4.

[0014] The water supply device 2 supplies water to the water pipes 4 via the lower header 3. The water supply device 2 has a water supply pipe 10 connected to the lower header 3, a water supply pump 11 arranged on the water supply pipe 10, and a water supply valve 12 arranged on the water supply pipe 10. When the water supply pump 11 is operated, water is supplied to the lower header 3 via the water supply pipe 10. When water is supplied to the lower header 3, water is supplied to the water pipes 4.

[0015] The lower header 3 contains water supplied from the water supply device 2. The lower header 3 is connected to the lower ends of the water pipes 4. The lower header 3 distributes the water supplied from the water supply device 2 to each of the multiple water pipes 4. The water supplied from the water supply device 2 to the lower header 3 is supplied to each of the multiple water pipes 4. A drain pipe 13 is connected to the lower part of the lower header 3. A drain valve 14 is disposed on the drain pipe 13. When the drain valve 14 opens, at least a portion of the water contained in the lower header 3 is discharged through the drain pipe 13.

[0016] The water pipe 4 distributes water from the lower header 3. The water pipe 4 is a cylindrical member having a water flow path. The water pipe 4 is arranged so that its central axis is parallel to the Z-axis. The lower end of the water pipe 4 is connected to the upper part of the lower header 3. Multiple water pipes 4 are arranged at intervals in the X-axis direction. Each of the multiple water pipes 4 is connected to the lower header 3.

[0017] The electric heater 7A is disposed inside the water tube 4. The electric heater 7A is a rod-shaped member. The electric heater 7A is disposed so that the central axis of the electric heater 7A is parallel to the Z-axis. The surface of the electric heater 7A faces the inner surface of the water tube 4 across a gap. Water from the lower header 3 is supplied between the inner surface of the water tube 4 and the surface of the electric heater 7A. The electric heater 7A is immersed in water inside the water tube 4. The surface of the electric heater 7A comes into contact with the water supplied inside the water tube 4. The contact between the surface of the electric heater 7A and the water heats the water and generates steam.

[0018] The riser pipe 5 circulates the steam generated in the water pipes 4. The riser pipe 5 is a cylindrical member having a steam flow path. The riser pipe 5 connects the water pipes 4 and the upper header 6. The steam generated in the water pipes 4 is supplied to the upper header 6 through the riser pipe 5. The lower end of the riser pipe 5 is connected to the upper end of the water pipe 4. The upper end of the riser pipe 5 is connected to the lower part of the upper header 6. A plurality of riser pipes 5 are provided so as to be connected to each of the plurality of water pipes 4. Each of the plurality of riser pipes 5 is connected to the upper header 6.

[0019] As shown in Figure 2, in the Y-axis direction, the positions of the lower header 3 and water pipes 4 are different from the position of the upper header 6. A part of the riser pipe 5 is bent. The lower end of the riser pipe 5 is connected to the -Y side surface of the upper part of the water pipe 4. The upper end of the riser pipe 5 is connected to the lower part of the upper header 6.

[0020] The upper header 6 receives the steam supplied from the riser pipes 5. The upper header 6 communicates with the upper ends of the water pipes 4 via the riser pipes 5. The upper header 6 collects the steam supplied from each of the multiple riser pipes 5. A steam pipe 15 is connected to the top of the upper header 6. A steam valve 16 is disposed on the steam pipe 15. When the steam valve 16 opens, at least a portion of the steam received in the upper header 6 is discharged via the steam pipe 15.

[0021] The water level detector 9 detects the water level of the water tube 4. The water level refers to the position of the surface of the water in the Z-axis direction. The water level detector 9 has a detection container 17, a plurality of electrode rods 18 arranged inside the detection container 17, a lower connecting pipe 19 connecting the detection container 17 and the lower header 3, and an upper connecting pipe 20 connecting the detection container 17 and the upper header 6. In this embodiment, three electrode rods 18 are provided. It is to be noted that, for example, four or more electrode rods 18 may be provided. The upper end of the electrode rod 18 is held on the upper lid of the detection container 17 via an insulating material. The lower end of the electrode rod 18 is separated from the detection container 17. The positions of the lower ends of the plurality of electrode rods 18 in the Z-axis direction are different from each other. The detection container 17 is formed of a conductive material. The detection container 17 functions as a common electrode for the plurality of electrode rods 18. Water is contained in the detection container 17. The water level of the detection container 17 and the water level of the water tube 4 are substantially equal. When the water contained in the detection container 17 comes into contact with the lower end of the electrode rod 18, electricity is passed between the detection container 17 and the electrode rod 18 via the water. When a current flows through the electrode rod 18, the water level detection device 9 determines that the electrode rod 18 has come into contact with the water. The water level detection device 9 detects the water level of the detection container 17 based on the presence or absence of a current flowing through each of the multiple electrode rods 18. The water level detection device 9 can detect the water level of the water tube 4 by detecting the water level of the detection container 17.

[0022] <Heater device> Fig. 3 is a vertical cross-sectional view showing the heater device 8 according to this embodiment. Fig. 4 is a horizontal cross-sectional view showing the electric heater 7A according to this embodiment. As shown in Figs. 1, 2, 3, and 4, the heater device 8 has the electric heater 7A, a flange 21 supported on the upper end of the water pipe 4, and a connector 22 connected to a power source.

[0023] The electric heater 7A is disposed inside the water tube 4 for the electric boiler 1. The electric heater 7A is a sheathed heater. The electric heater 7A has a surface that faces the inner surface of the water tube 4 with a gap therebetween. The electric heater 7A is inserted into the inside of the water tube 4 from an opening at the upper end of the water tube 4. A flange 21 is fixed to the upper end of the water tube 4. The heater device 8 is detachable from the water tube 4.

[0024] As shown in Figures 3 and 4, the electric heater 7A includes a pipe 23, a core 24 arranged inside the pipe 23, a heating wire 25 arranged inside the pipe 23, a terminal 26 arranged at the upper end of the pipe 23, an insulating material 27 arranged inside the pipe 23, and a cover 29 connected to the lower end of the pipe 23 via a welded part 28.

[0025] The pipe 23 is made of a metal. The pipe 23 is made of a metal having high thermal conductivity. Examples of the metal that forms the pipe 23 include stainless steel (SUS), nickel (Ni), and copper (Cu). The pipe 23 has a straight shape. The pipe 23 is arranged such that the central axis of the pipe 23 is parallel to the Z-axis.

[0026] The core 24 is a cylindrical member. The core 24 is made of an insulating material such as ceramics. The core 24 is disposed so that the central axis of the core 24 is parallel to the Z-axis.

[0027] The heating wire 25 is a nichrome wire. The heating wire 25 is disposed around the core 24 inside the pipe 23. The heating wire 25 is wound around the core 24 in a coil shape.

[0028] The terminal 26 is connected to the heating wire 25. A pair of terminals 26 are provided. At least a portion of the terminal 26 is disposed at the upper end of the pipe 23. At least a portion of the terminal 26 is disposed inside the core 24. The terminal 26 is connected to a power source via the connector 22. When a current is supplied from the power source to the heating wire 25 via the terminal 26, the heating wire 25 generates heat. One terminal 26 is connected to the upper end of the heating wire 25. The other terminal 26 is connected to the lower end of the heating wire 25. A current input from the power source to one terminal 26 flows through the heating wire 25 and is then output from the other terminal 26.

[0029] The insulating material 27 is disposed between the pipe 23 and the core 24 and the heating wire 25. The insulating material 27 is filled inside the pipe 23. The insulating material 27 is made of an insulating material such as magnesium oxide (MgO). The insulating material 27 is in powder form.

[0030] The opening at the upper end of the pipe is closed by a sealing member 30. The flange 21 is disposed at the upper end of the pipe .

[0031] The opening at the lower end of the pipe 23 is closed by the cover 29. The cover 29 is formed of a metal. The cover 29 is formed of a metal with high thermal conductivity. Examples of the metal forming the cover 29 include stainless steel (SUS), nickel (Ni), and copper (Cu). In this embodiment, the cover 29 is substantially disk-shaped. The cover 29 is fixed to the lower end of the pipe 23 by welding. A weld 28 is formed at the boundary between the lower end of the pipe 23 and the cover 29. The weld 28 includes a weld metal and the heat-affected zones of the pipe 23 and the cover 29.

[0032] In this embodiment, a plurality of fins 32 are provided on the outer surface of the pipe 23. The fins 32 are provided to extend in the up-down direction (Z-axis direction). As shown in Fig. 3, in the Z-axis direction, the position of the upper end of the fins 32 and the position of the upper end of the pipe 23 are substantially the same. In the Z-axis direction, the position of the lower end of the fins 32 and the position of the lower end of the pipe 23 are substantially the same.

[0033] As shown in Fig. 4, the fins 32 are provided at intervals in the circumferential direction of the central axis CX of the pipe 23. The multiple fins 32 are arranged at equal intervals in the circumferential direction of the central axis CX. In an XY plane perpendicular to the central axis CX (Z-axis), the fins 32 are substantially rectangular. Each fin 32 has a shape in which the circumferential dimension is substantially constant toward the radial outside of the central axis CX. The multiple fins 32 protrude by the same amount from the outer surface of the pipe 23.

[0034] The fins 32 may be formed by forming grooves extending in the vertical direction on the outer surface of a straight pipe. The fins 32 may be formed by welding protruding members to the outer surface of the straight pipe.

[0035] <Operation> Next, the operation of the heater device 8 will be described. With the electric heater 7A immersed in water inside the water tube 4, a current is supplied from a power source to the heating wire 25 via one terminal 26. As a result of the current being supplied to the heating wire 25, the heating wire 25 is heated, for example, to about 500°C. As the heating wire 25 is heated, the water inside the water tube 4 is heated and steam is generated. The temperature of the water (steam) inside the water tube 4 rises to, for example, about 180°C.

[0036] Inside the water pipes 4, water flows from the lower part to the upper part of the water pipes 4. That is, inside the water pipes 4, water flows from the lower header 3 to the upper header 6. The fins 32 are provided to extend in the vertical direction. The fins 32 guide the water flowing from the lower header 3 to the upper header 6.

[0037] If the watt density of the electric heater 7A increases and the surface temperature of the electric heater 7A (the outer surface temperature of the pipe 23) increases, the life of the electric heater 7A may be shortened. In this embodiment, fins 32 are provided on the outer surface of the pipe 23. The fins 32 dissipate heat from the outer surface of the pipe 23 to the surrounding water. The fins 32 function as heat dissipation fins. The fins 32 prevent the outer surface temperature of the pipe 23 from becoming excessively high.

[0038] The heat of the heating wire 25 is transferred to the pipe 23 via the insulating material 27. The fins 32 prevent the outer surface temperature of the pipe 23 from becoming excessively high, so that the heat of the heating wire 25 is transferred smoothly to the pipe 23 via the insulating material 27. The heat of the heating wire 25 is transferred smoothly to the pipe 23, so that the heating wire 25 is prevented from being excessively heated. In addition, the outer surface temperature of the pipe 23 is prevented from becoming excessively high, so that the pipe 23 immersed in water is prevented from corroding, and scale is prevented from adhering to the surface of the pipe 23. In addition, the fins 32 make the outer surface temperature distribution of the pipe 23 uniform. Therefore, the life of the electric heater 7A is prevented from being shortened.

[0039] Furthermore, the fins 32 are provided to extend in the vertical direction and guide the water flowing from the lower header 3 to the upper header 6, thereby preventing water from accumulating around the electric heater 7A.

[0040] <Effects> As described above, according to this embodiment, the fins 32 are provided on the outer surface of the pipe 23, so that the surface temperature of the electric heater 7A (the outer surface temperature of the pipe 23) is prevented from becoming excessively high. Therefore, the life of the electric heater 7A is prevented from being shortened. In addition, the fins 32 guide water, so that the water is prevented from accumulating around the electric heater 7A.

[0041] [Second embodiment] A second embodiment will be described below. In the following description, the same or equivalent components as those in the above-described embodiment are denoted by the same reference numerals, and the description of those components will be simplified or omitted.

[0042] FIG. 5 is a cross-sectional view showing an electric heater 7B according to this embodiment. A plurality of fins 33 are provided on the outer surface of the pipe 23. The fins 33 are provided so as to extend in the up-down direction (Z-axis direction). The fins 33 are provided at intervals in the circumferential direction of the central axis CX of the pipe 23. The plurality of fins 33 are arranged at equal intervals in the circumferential direction of the central axis CX. In an XY plane perpendicular to the central axis CX (Z-axis), the fins 33 are substantially triangular. Each fin 33 has a shape in which the circumferential dimension gradually decreases toward the radial outside of the central axis CX. The plurality of fins 33 protrude from the outer surface of the pipe 23 by the same amount.

[0043] As described above, in the XY plane perpendicular to the central axis CX (Z axis), the fins 33 may be triangular.

[0044] [Third embodiment] A third embodiment will be described below. In the following description, the same or equivalent components as those in the above-described embodiment are denoted by the same reference numerals, and the description of those components will be simplified or omitted.

[0045] FIG. 6 is a schematic diagram showing a water tube 40 and an electric heater 7C according to the present embodiment. As shown in FIG. 6, the electric heater 7C is disposed inside a water tube 40 for an electric boiler. The electric heater 7C has a pipe 230 and fins 43 provided on the outer surface of the pipe 230. As shown in FIG. 6, the electric heater 7C may be disposed inside the water tube 40 so that the central axis CX of the pipe 230 is perpendicular to the Z axis. The fins 34 may be provided on the outer surface of the pipe 230 so as to extend in the vertical direction. A plurality of fins 34 may be provided at intervals in the axial direction of the central axis CX. A plurality of fins 34 may be disposed at equal intervals in the axial direction of the central axis CX. The fins 34 can guide water flowing from the lower end (lower header) of the water tube 40 to the upper end (upper header) of the water tube 40.

[0046] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] This disclosure includes matters that contribute to achieving Goal 12 "Responsible consumption and production" and Goal 13 "Take urgent action to combat climate change" of the Sustainable Development Goals (SDGs). [Explanation of symbols]

[0047] 1...electric boiler, 2...feedwater device, 3...lower header, 4...water pipe, 5...rising pipe, 6...upper header, 7A...electric heater, 7B...electric heater, 7C...electric heater, 8...heater device, 9...water level detection device, 10...feedwater pipe, 11...feedwater pump, 12...feedwater valve, 13...drain pipe, 14...drain valve, 15...steam pipe, 16...steam valve, 17...detection vessel, 18...electrode rod, 19...lower connecting pipe, 20...upper connecting pipe, 21...flange, 22...connector, 23...pipe, 24...core, 25...heating wire, 26...terminal, 27...insulating material, 28...welded part, 29...cover, 30...sealing member, 32...fin, 33...fin, 34...fin, 40...water pipe, 230...pipe, CX...center axis.

Claims

1. An electric heater that is immersed in water, Pipes and A heating wire disposed inside the pipe; an insulating material disposed between the heating wire and the pipe; The outer surface of the pipe is provided with fins. Electric heater.

2. The electric heater according to claim 1 ; a water pipe inside which the electric heater is disposed; a lower header communicating with a lower end of the water pipe; an upper header communicating with an upper end of the water pipe; The fins are provided to extend in the vertical direction. Electric boiler.

3. The fins guide water flowing from the lower header toward the upper header.

3. An electric boiler as claimed in claim 2.

4. The fins are provided at intervals in the circumferential direction of the central axis of the pipe.

3. An electric boiler as claimed in claim 2.

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