Electric boiler

Abstract

To provide an electric boiler for enabling appropriate temperature detection using a small number of temperature sensors even when the number of water pipes is increased.SOLUTION: An electric boiler 1 includes a plurality of lower headers (2a, 2b), a plurality of water pipes 3 extending from each of the plurality of lower headers (2a, 2b) to the upper side, a plurality of electric heaters 4 provided in the plurality of water pipes 3, respectively, upper headers 6 connected to the plurality of water pipes 3 via riser tubes 5, respectively, and a plurality of temperature sensors (10a, 10b) provided in the plurality of lower headers (2a, 2b) and arranged on electric heaters 4 in water pipes 3 in any of the lower headers (2a, 2b), respectively.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Electric boilers that heat water with an electric heater are known. In Patent Document 1, three water tubes are arranged vertically between an upper header and a lower header, and an electric heater is installed in each water tube. The three water tubes are arranged in a row along the length of the cylindrical lower header. One temperature sensor is arranged in each electric heater, and a calculation processing device determines whether the electric heater is overheated or not based on the detection value of the temperature sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6958253 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to increase the output of the electric boiler, it is possible to increase the number of water tubes (and electric heaters). When a temperature sensor is provided for each water tube electric heater as in Patent Document 1, increasing the number of water tubes also increases the number of temperature sensors, which leads to a complication of the configuration and control of the electric boiler and an increase in costs.

[0005] Therefore, it is conceivable to reduce the number of temperature sensors compared to the number of water pipes (electric heaters) and have the detection value of one temperature sensor represent the temperature state of each electric heater of multiple water pipes in the vicinity. However, if the number of water pipes is increased, for example, there is a possibility that the difference between the state of the water pipe at one end of the lower header and the state of the water pipe at the other end will become large. Therefore, even if the number of temperature sensors is reduced compared to the number of water pipes (electric heaters), Patent Document 1 does not provide a guideline for how many temperature sensors should be installed and where they should be located. Therefore, it is desirable to be able to detect the appropriate temperature with a small number of temperature sensors even when the number of water pipes is increased.

[0006] The technology disclosed in this specification aims to provide an electric boiler that is capable of appropriate temperature detection with a small number of temperature sensors even when the number of water tubes is increased. [Means for solving the problem]

[0007] This specification discloses an electric boiler comprising: a plurality of lower headers, a plurality of water tubes extending upward from each of the plurality of lower headers, a plurality of electric heaters inserted into upper ends of each of the plurality of water tubes, an upper header connected to each of the plurality of water tubes via riser pipes, and a plurality of temperature sensors provided for each of the plurality of lower headers and disposed in the electric heaters inserted into any of the water tubes of each of the lower headers. Effect of the Invention

[0008] According to the technology disclosed in this specification, an electric boiler is provided that is capable of appropriate temperature detection with a small number of temperature sensors even when the number of water tubes is increased. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view that shows a schematic view of a boiler body of an electric boiler according to this embodiment. [Diagram 2] FIG. 2 is a side view that illustrates an example of the electric boiler according to the present embodiment. [Diagram 3] FIG. 3 is a top view that illustrates an example of the electric boiler according to the present embodiment. [Figure 4] FIG. 4 is a side cross-sectional view showing an example of the electric heater according to the present embodiment. [Diagram 5] FIG. 5 is a vertical cross-sectional view (A) and a horizontal cross-sectional view (B) illustrating a first example of mounting a temperature sensor to an electric heater. [Figure 6] FIG. 6 is a vertical sectional view illustrating a second example of mounting a temperature sensor on an electric heater. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment according to 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.

[0011] In this embodiment, a three-dimensional orthogonal coordinate system is defined, and the positional relationship of each part will be described based on the three-dimensional orthogonal coordinate system. Two directions that are orthogonal to each other in a horizontal plane are defined as the X direction and the Y direction, respectively. One side of the X direction is defined as the X1 direction, and the other side of the X direction is defined as the X2 direction. The up-down direction (vertical direction) that is orthogonal to the X direction and the Y direction is defined as the Z direction.

[0012] <Electric boiler> Fig. 1 is a perspective view that typically shows a boiler body WS of an electric boiler 1 according to this embodiment. Fig. 2 is a side view that typically shows an example of an electric boiler 1 according to this embodiment. Fig. 3 is a top view that typically shows an example of an electric boiler 1 according to this embodiment. Fig. 2 shows a cross section of a portion of the electric boiler 1.

[0013] 1 and 2, the electric boiler 1 includes a plurality of lower headers (first lower header 2a, second lower header 2b), a plurality of water tubes 3, a plurality of electric heaters 4 provided inside each of the plurality of water tubes 3, an upper header 6 connected to each of the plurality of water tubes 3 via a riser tube 5, and a plurality of temperature sensors (first temperature sensor 10a, second temperature sensor 10b, see FIG. 3). In the example of FIG. 2, the electric boiler 1 includes a water supply device 20, a water level detector 30 that detects the water level of the water tubes 3, a control device 40 that controls the electric boiler 1, a power source 41 that supplies power to the electric heater 4, and an alarm device 42 that issues alarm information.

[0014] The boiler body WS shown in Fig. 1 is formed by interconnecting the first lower header 2a, the second lower header 2b, the water tubes 3, the riser tubes 5, and the upper header 6. The boiler body WS is a container for receiving a supply of water, evaporating it, and discharging steam. The electric boiler 1 is a once-through boiler. That is, an electric heater 4 is attached to each of the multiple water tubes 3, and all of the water tubes 3 are connected to the riser tube 5.

[0015] (Lower header) In the example of FIG. 1, the first lower header 2a and the second lower header 2b extend in the X direction (first direction) in a horizontal plane. The second lower header 2b is arranged side by side in the Y direction (second direction) perpendicular to the X direction (first direction) in the horizontal plane. The first lower header 2a and the second lower header 2b are made of cylindrical pipes with both ends sealed and extend linearly. The cylindrical portions of the first lower header 2a and the second lower header 2b have approximately the same dimensions.

[0016] The first lower header 2a and the second lower header 2b are containers that contain water supplied from a water supply device 20 (see FIG. 2). The first lower header 2a and the second lower header 2b are each provided with a water pipe 3. The first lower header 2a and the second lower header 2b distribute the water supplied from the water supply device 20 to a plurality of water pipes 3. As shown in FIG. 1, the first lower header 2a and the second lower header 2b are connected to a drain pipe 7 and a downcomer pipe 8. The first lower header 2a and the second lower header 2b are each connected to one water supply pipe 9a, 9b.

[0017] (water pipe) The water tubes 3 extend upward from each of the multiple lower headers (first lower header 2a and second lower header 2b). The first lower header 2a and the second lower header 2b are each provided with multiple water tubes 3. In the example of FIG. 1, the first lower header 2a has six water tubes 3 arranged at intervals in the X direction. The second lower header 2b has six water tubes 3 arranged at intervals in the X direction. As shown in FIG. 3, the intervals (pitch) between adjacent water tubes 3 in the X direction are approximately equal in the first lower header 2a and the second lower header 2b. Each water tube 3 in the first lower header 2a and each water tube 3 in the second lower header 2b are shifted by half a pitch in the X direction.

[0018] The water pipe 3 distributes water from the lower header (first lower header 2a or second lower header 2b). The water pipe 3 is a cylindrical pipe that distributes water and extends in a straight line. The water pipe 3 is arranged so that the central axis of the water pipe 3 is parallel to the Z axis. The lower end of the water pipe 3 communicates with the upper part of the lower header (first lower header 2a or second lower header 2b).

[0019] In this way, the electric boiler 1 according to this embodiment has multiple steam generation systems, one for each lower header. That is, the electric boiler 1 has a first system including six water tubes 3 arranged in the first lower header 2a and a second system including six water tubes 3 arranged in the second lower header 2b.

[0020] (Electric heater) As shown in FIG. 2, the electric heater 4 is inserted into the interior of each of the water tubes 3 from the upper end of the tube. In this embodiment, a total of 12 electric heaters 4 are provided, one for each of the 12 water tubes 3. The electric heater 4 has a straight rod shape. The electric heater 4 is, for example, a sheath heater or a ceramic heater. The surface of the electric heater 4 faces the inner surface of the water tube 3 with a gap therebetween. The surface of the electric heater 4 comes into contact with the water supplied inside the water tube 3. The contact between the surface of the electric heater 4 and the water heats the water and generates steam. The operation (on / off and heat generation) of the electric heater 4 is controlled by a control device 40 controlling the power supply from a power source 41.

[0021] The electric heater 4 has a heat generating area FA that generates heat when energized, and a non-heat generating area NA. The non-heat generating area NA is disposed above the heat generating area FA. The heat generating area FA includes the lower end of the electric heater 4, and is longer in the Z direction than the non-heat generating area NA. The non-heat generating area NA includes the upper end of the electric heater 4.

[0022] (Temperature Sensor) The first temperature sensor 10a and the second temperature sensor 10b (see FIG. 3) are provided for each of the lower headers (first lower header 2a and second lower header 2b). In this embodiment, since there are two lower headers, two temperature sensors, the first temperature sensor 10a and the second temperature sensor 10b, are provided. The first temperature sensor 10a is disposed on an electric heater 4 inserted into one of the water pipes 3 of the first lower header 2a. The second temperature sensor 10b is disposed on an electric heater 4 inserted into one of the water pipes 3 of the second lower header 2b. The first temperature sensor 10a and the second temperature sensor 10b are, for example, thermocouples, thermistors, etc. The installation positions of the first temperature sensor 10a and the second temperature sensor 10b will be described later.

[0023] (Rising pipe and upper header) As shown in FIG. 1 , the riser pipe 5 connects the water pipes 3 and the upper header 6. The riser pipe 5 is a cylindrical pipe having a steam flow path. The riser pipe 5 circulates the steam generated in the water pipes 3. The lower end of the riser pipe 5 is connected to the upper part of the water pipes 3. The upper end of the riser pipe 5 is connected to the lower part of the upper header 6. The steam generated in the water pipes 3 is supplied to the upper header 6 via the riser pipe 5. One riser pipe 5 is provided for each of the multiple water pipes 3 (i.e., a total of 12 riser pipes 5). The upper ends of the multiple riser pipes 5 are each connected to one upper header 6.

[0024] The lower ends of the riser pipes 5 are bent and connected to the side of the upper part of the water pipes 3. The upper ends of the riser pipes 5 are connected to the lower part of the upper header 6. The upper ends of the twelve riser pipes 5 extending respectively from the six water pipes 3 of the first lower header 2a and the six water pipes 3 of the second lower header 2b are aligned in a straight line along the X direction (first direction) and connected to the lower part of the upper header 6.

[0025] The upper header 6 accommodates the steam supplied from the riser pipes 5. The upper header 6 is made of a cylindrical pipe sealed at both ends, and is a vessel for accommodating steam. In this embodiment, only one upper header 6 is provided for the multiple lower headers (2a, 2b). Multiple upper headers 6 may be provided. The upper header 6 receives and collects the steam supplied from each of the multiple riser pipes 5.

[0026] As shown in Fig. 2, a steam pipe 11 is connected to the upper part of the upper header 6. A steam valve 12 is disposed on the steam pipe 11. When the steam valve 12 is opened, at least a part of the steam contained in the upper header 6 is discharged through the steam pipe 11.

[0027] The upper header 6 extends in a first direction (X direction) in a horizontal plane. As shown in Fig. 1, the upper header 6 is disposed at a position shifted in the Y direction with respect to each of the first lower header 2a and the second lower header 2b.

[0028] (water supply pipe) The water supply pipes 9a, 9b (see FIG. 1) are connected to a plurality of lower headers (first lower header 2a and second lower header 2b). The water supply pipes 9a, 9b are provided in a plurality (two pipes) so as to be individually connected to the plurality of lower headers (2a, 2b).

[0029] As shown in FIG. 2 (particularly illustrating the water supply pipe 9b), the water supply pipes 9a, 9b are connected to each of the multiple lower headers (2a, 2b) at intermediate positions in the X direction (first direction). Here, the intermediate positions refer to intermediate positions in the arrangement of the water pipes 3. Specifically, the water supply pipe 9b is connected to a position (intermediate position) where the six water pipes 3 of the second lower header 2b are divided into groups of three. Similarly, the water supply pipe 9a is connected to a position (intermediate position) where the six water pipes 3 of the first lower header 2a are divided into groups of three. Three water pipes 3 are arranged on each of one end side (X1 side) and the other end side (X2 side) in the X direction with respect to the connection position of the water supply pipe 9a. In addition, when the number of water pipes 3 in the first lower header 2a or the second lower header 2b is an odd number (2N+1), the intermediate position is the position where the water pipes 3 are divided into N and N+1 at one end and the other end.

[0030] The water supply pipes 9a and 9b have water supply ports SP1 and SP2 facing one end side and the other end side in the X direction (first direction) inside the first lower header 2a and the second lower header 2b. Specifically, a T-shaped pipe joint 9c is arranged inside the second lower header 2b, and the ends of the water supply pipes 9a and 9b are connected to the inlets of the pipe joint 9c. The two openings of the pipe joint 9c branched into a T shape are directed to one end side (X1 side) and the other end side (X2 side) in the X direction, respectively constituting a pair of water supply ports SP1 and SP2. As a result, the water supply port SP1 supplies water toward the three water pipes 3 on one end side, and the water supply port SP2 supplies water toward the three water pipes 3 on the other end side. Although only the water supply ports SP1 and SP2 of the water supply pipe 9b are illustrated in FIG. 2, the same is true for the water supply pipe 9a.

[0031] The water supply pipes 9a, 9b are connected to a water supply device 20. The water supply device 20 has a water supply branch 21 connected to the water supply pipes 9a, 9b, a water supply pump 22, and a water supply valve 23 provided between the water supply branch 21 and the water supply pump 22.

[0032] The water supply pump 22 discharges water to the first lower header 2a and the second lower header 2b via the water supply valve 23, the water supply branch 21, and each of the water supply pipes 9a, 9b. This supplies water to each of the water pipes 3. The water supply device 20 can adjust the amount of water supply per unit time by the control device 40 controlling the rotation speed of the water supply pump 22. The water supply valve 23 opens and closes the water supply path to the water supply branch 21. When the water supply valve 23 functions as a flow rate adjustment valve, the water supply valve 23 may adjust the amount of water supply per unit time.

[0033] (drain pipe) As shown in Fig. 1, the drain pipe 7 is connected to the lower part of each of the first lower header 2a and the second lower header 2b. The drain pipe 7 is connected to one end of the first lower header 2a and the second lower header 2b in the X direction (on the X1 side of each water pipe 3) (see Fig. 2).

[0034] The drain pipe 7 has a communication section 7a that communicates the first lower header 2a and the second lower header 2b. The drain pipe 7 extends downward from the first lower header 2a and the second lower header 2b, respectively, and then has pipe sections 7b and 7c that are bent so as to approach each other in the Y direction, and the pipe sections 7b and 7c are each connected to the communication section 7a. The communication section 7a is a T-shaped pipe joint. The drain pipe 7 has a pipe section 7d that extends from the communication section 7a and discharges the joined water. A drain valve 13 (see FIG. 2) is disposed in the pipe section 7d. When the drain valve 13 opens, at least a portion of the water contained in the first lower header 2a and the second lower header 2b is discharged (called blow) through the drain pipe 7.

[0035] The communication section 7a communicates the first system on the first lower header 2a side with the second system on the second lower header 2b side. As a result, the communication section 7a functions to make the water levels of the water tubes 3 uniform even if there is variation in the amount of steam generated or the amount of water distributed between the systems.

[0036] (Downpipe) As shown in Fig. 1, the downcomer pipe 8 is connected to the upper header 6 and branches at a branching portion 8a to connect to each of the first lower header 2a and the second lower header 2b. The steam flowing into the upper header 6 is a wet saturated steam mixture of air and water, and the downcomer pipe 8 returns the water that has flowed into the upper header 6 to the first lower header 2a and the second lower header 2b. In the electric boiler 1 according to this embodiment, a separator (gas-liquid separator, not shown) is not provided, so the downcomer pipe 8 is directly connected to the upper header 6, but a separator may be provided between the upper header 6 and the downcomer pipe 8, and the downcomer pipe 8 may be connected to the separator.

[0037] The downcomer pipe 8 is connected to one end (X1 side) in the X direction (first direction) of each of the multiple lower headers (first lower header 2a and second lower header 2b). Specifically, the downcomer pipe 8 connects one end (X1 side) in the X direction of the upper header 6 (X1 side of each uprising pipe 5) and one end (X1 side of each water pipe 3) of the first lower header 2a and the second lower header 2b in the X direction.

[0038] The downcomer pipe 8 is composed of a branching section 8a and pipe sections 8b to 8d. The upper end of pipe section 8b is connected to the lower part of the upper header 6. Pipe section 8b extends downward from the upper header 6 in the Z direction, then bends and connects to the branching section 8a. The branching section 8a is a T-shaped pipe joint, and causes the downcomer pipe 8 to branch into two in the Y direction toward the first lower header 2a side and the second lower header 2b side. Pipe section 8c bends downward from the branching section 8a and connects to the upper part of the first lower header 2a. Pipe section 8d bends downward from the branching section 8a and connects to the upper part of the second lower header 2b. With this configuration, the branching section 8a has the function of communicating the insides of the first lower header 2a and the second lower header 2b with each other, similar to the drain pipe 7.

[0039] The downcomer pipe 8 has a concentrated drain outlet 14 between the upper header 6 and the branch 8a. The concentrated drain outlet 14 is connected to a concentrated drain valve 15 (see FIG. 2). By opening the concentrated drain valve 15, the water in the downcomer pipe 8 can be discharged to the outside (called concentrated blow). The impurity concentration in the boiler body WS is reduced by the water supply from the water supply pipes 9a and 9b and the water discharged from the concentrated drain outlet 14.

[0040] The downcomer pipe 8 has a water quality measuring unit 16 (see FIG. 2) between the branch 8a and the concentrated drain outlet 14. The water quality measuring unit 16 is connected to a connection port 8e (see FIG. 1) provided between the branch 8a and the concentrated drain outlet 14. The water quality measuring unit 16 has, for example, an electrical conductivity sensor that measures the electrical conductivity of the water in the pipe. By monitoring the electrical conductivity of the water in the boiler body WS with the water quality measuring unit 16, it is possible to grasp the degree of concentration of the water in the boiler body WS. Then, when the water in the boiler body WS becomes more concentrated than a predetermined amount as the electric boiler 1 is operated, the concentrated drain valve 15 is opened to perform concentrated blow.

[0041] (Water Level Detector) As shown in FIG. 2, the water level detector 30 is connected to the upper header 6 and the first lower header 2a via a detector connection pipe 31. In this embodiment, the water level detector 30 is connected only to the first lower header 2a (see FIG. 3), but it may be connected only to the second lower header 2b, or to both. The detector connection pipe 31 includes an upper communication pipe 31a that connects the upper end of the water level detector 30 to the upper header 6, and a lower communication pipe 31b that connects the lower end of the water level detector 30 to the first lower header 2a. Note that the water level detector 30 and the detector connection pipe 31 are not shown in FIG. 1.

[0042] The detector connection pipe 31 is disposed on one end side of the first lower header 2a in the X direction. Therefore, the detector connection pipe 31, the downcomer pipe 8, and the drain pipe 7 are all disposed on one end side of the first lower header 2a in the X direction (first direction). The detector connection pipe 31, the downcomer pipe 8, and the drain pipe 7 are disposed closer to one end side (X1 side) in the X direction than the multiple (12) water pipes 3.

[0043] The water level detector 30 has a detection container 32 and a plurality of electrode rods 33 arranged in the detection container 32. The upper and lower surfaces of the detection container 32 are connected to the upper communicating pipe 31a and the lower communicating pipe 31b, respectively, and water is contained therein. The water level of the detection container 32 and the water level of each water tube 3 are substantially equal. The water level detector 30 can detect the water level of the water tube 3 by detecting the water level of the detection container 32. The water level refers to the position of the water surface in the Z-axis direction.

[0044] The plurality of electrode rods 33 are disposed inside the detection container 32. In this embodiment, the electrode rods 33 include three electrode rods 33A, 33B, and 33C. Note that two or four or more electrode rods 33 may be provided.

[0045] The electrode rod 33 is a rod-shaped member made of a conductive material. The upper end of the electrode rod 33 is held by the upper lid of the detection container 32 via an insulating member (not shown). The lower end of the electrode rod 33 is separated from the inner surface of the detection container 32.

[0046] The positions of the lower ends of the electrode bars 33A, 33B, and 33C in the Z-axis direction are different. In this embodiment, among the electrode bars 33A, 33B, and 33C, the lower end of the electrode bar 33A is located at the highest position, the lower end of the electrode bar 33B is located at the next highest position after the lower end of the electrode bar 33A, and the lower end of the electrode bar 33C is located at the lowest position.

[0047] The detection container 32 is made of a conductive material. The detection container 32 functions as a common electrode for the multiple electrode rods 33. When the water contained in the detection container 32 comes into contact with the lower ends of the electrode rods 33, electricity is conducted between the detection container 32 and the electrode rods 33 via the water.

[0048] The water level detector 30 detects the water level in the detection container 32 based on the presence or absence of a current flowing through each of the multiple electrode rods 33. In the Z-axis direction, the position of the lower end of the electrode rod 33C and the position of the upper end (boundary EG) of the heat generating area FA of the electric heater 4 are substantially the same.

[0049] When the electrodes 33B and 33C detect water but the electrode 33A does not detect water, the control device 40 operates the water supply pump 22 to supply water. When all of the electrodes 33A, 33B, and 33C detect water, the control device 40 stops the operation of the water supply pump 22 to stop water supply. As a result, the water level in the water tube 3 is maintained at a position between the lower end of the electrode 33A and the lower end of the electrode 33B. By maintaining the water level in the water tube 3 between the lower end of the electrode 33A and the lower end of the electrode 33B, the entire heat generating area FA of the electric heater 4 can be immersed in water. When the electrode 33C does not detect water, the control device 40 determines that at least a part of the heat generating area FA of the electric heater 4, including the upper end, is not immersed in the water of the water tube 3. The control device 40 may stop the power supply to the electric heater 4 when the electrode 33C does not detect water for a predetermined time.

[0050] <Temperature sensor> As described above, the first temperature sensor 10a and the second temperature sensor 10b are provided on each of the plurality of lower headers (the first lower header 2a and the second lower header 2b).

[0051] As a result, the detection value of the first temperature sensor 10a represents the first system, i.e., the temperature state of each electric heater 4 in the multiple (six) water tubes 3 provided in the first lower header 2a. The detection value of the second temperature sensor 10b represents the second system, i.e., the temperature state of each electric heater 4 in the multiple (six) water tubes 3 provided in the second lower header 2b.

[0052] In other words, in this embodiment, the number of water pipes 3 (electric heaters 4) provided in one lower header is set within a range in which one temperature sensor can represent the temperature states of all the electric heaters 4 in the system. In this embodiment, one temperature sensor represents the electric heaters 4 of six water pipes 3 in the system, but the number of water pipes 3 (electric heaters 4) that one temperature sensor can represent is not limited to six and is set appropriately depending on the specifications, dimensions, etc. of the electric heaters 4 and boiler body WS.

[0053] For example, assume that the total number of water tubes 3 (electric heaters 4) is designed to be A based on the total output required for the electric boiler 1. Assume that the number of water tubes 3 (electric heaters 4) that can be represented by the detection value of one temperature sensor is B. In this case, the number of systems C (number of lower headers) is set to C≧A / B. By providing C sets of lower headers each equipped with B water tubes 3 that can be represented by one temperature sensor, it is possible to construct an electric boiler 1 equipped with a total of A water tubes 3 (electric heaters 4) using only C temperature sensors.

[0054] (Temperature sensor installation position) Next, the installation position of the temperature sensor will be described with reference to Fig. 3. In this embodiment, the temperature sensor is provided on the electric heater 4 of the second water pipe P2 that is closest to the connection position between the downcomer pipe 8 and at least one lower header. As shown in Fig. 3, the connection position of the downcomer pipe 8 is the end of the X1 side of each lower header, so the second water pipe P2 is the water pipe 3 at the end of the X1 side of the first lower header 2a and the second lower header 2b. In the example of Fig. 3, the first temperature sensor 10a is provided on the electric heater 4 of the second water pipe P2 of the first lower header 2a.

[0055] In this embodiment, the temperature sensor is provided on the electric heater 4 of the first water pipe P1 closest to the connection position between the water supply pipe and at least one lower header. In FIG. 3, the connection positions of the water supply pipes 9a, 9b (i.e., the position of the pipe joint 9c in FIG. 2) are shown by dashed lines. As described above, the connection positions of the water supply pipes 9a, 9b are the middle positions of the lower headers. Therefore, the first water pipe P1 is the two central water pipes 3 out of six in the first lower header 2a and the second lower header 2b. The first water pipe P1 on which the temperature sensor is installed may be either of the two. In the example of FIG. 3, the second temperature sensor 10b is provided on the electric heater 4 of the first water pipe P1 (the fourth water pipe 3 counting from the X1 side) of the second lower header 2b.

[0056] (Temperature sensor mounting structure) Fig. 4 is a side cross-sectional view showing an example of the electric heater according to this embodiment. Figs. 4 to 6 show the first temperature sensor 10a, but the mounting structure of the second temperature sensor 10b is similar to that of the first temperature sensor 10a shown in Figs. 4 to 6. As shown in Fig. 4, the first temperature sensor 10a (and the second temperature sensor 10b) are disposed in the water pipe 3 at the upper end of the heat generating area FA of the electric heater 4. The first temperature sensor 10a and the second temperature sensor 10b detect the temperature in the upper part of the heat generating area FA.

[0057] In the example of Fig. 4, the electric heater 4 includes three U-shaped heater components 4a, 4b, and 4c, and the first temperature sensor 10a is attached to one of the heater components, 4a, by a mounting fixture 50. The first temperature sensor 10a and each of the heater components 4a, 4b, and 4c are provided so as to protrude downward from a terminal unit 4d attached to the upper end of the water pipe 3 (see Fig. 2). The first temperature sensor 10a is connected to the control device 40 (see Fig. 2) via the terminal unit 4d. Each of the heater components 4a, 4b, and 4c is connected to a power source 41 (see Fig. 2) via the terminal unit 4d.

[0058] FIG. 5 is a longitudinal sectional view (A) and a transverse sectional view (B) illustrating a first example of mounting a temperature sensor (first temperature sensor 10a) to an electric heater 4. In the example of FIG. 5, the first temperature sensor 10a and a straight portion of the heater assembly 4a are bundled by a sleeve-shaped metal mounting fixture 50. The mounting fixture 50 fixes the temperature measuring portion of the first temperature sensor 10a in a state of intimate contact with the outer circumferential surface of the heater assembly 4a. In FIG. 5, the first temperature sensor 10a is a contact-type temperature sensor, and has a thermocouple housed in a protective tube.

[0059] Fig. 6 is a vertical cross-sectional view for explaining a second example of mounting a temperature sensor (first temperature sensor 10a) to an electric heater 4. In the example of Fig. 6, the first temperature sensor 10a and a straight portion of the heater assembly 4a are bundled together by a metal wire 51. The number of wires 51 is not particularly limited. The wire 51 fixes the first temperature sensor 10a in a state of intimate contact with the outer circumferential surface of the heater assembly 4a.

[0060] The difference between the example of FIG. 5 and the example of FIG. 6 is the diameter of the first temperature sensor 10a. The first temperature sensor 10a in FIG. 6 has a small diameter and is easily bent, so that the temperature measuring part is easily separated from the outer peripheral surface of the heater assembly 4a. Therefore, in the example of FIG. 6, the first temperature sensor 10a and the heater assembly 4a are bound together at multiple points with wires 51 to ensure a tight contact state. When the diameter of the first temperature sensor 10a is large and difficult to deform as in FIG. 5, it may be fixed with a sleeve-shaped mounting fixture 50 or bound with wires 51. The larger the diameter of the first temperature sensor 10a, the larger the surface area of ​​the temperature measuring part becomes, and the greater the heat dissipation from the non-contact parts with the heater assembly 4a becomes, so it is preferable that the diameter of the first temperature sensor 10a is small. In addition, as a method of attaching the temperature sensor, the first temperature sensor 10a and the heater assembly 4a may be integrated by brazing or the like.

[0061] [Control-related configuration] 2, the control device 40 includes a computer system. That is, the control device 40 has a processor such as a CPU (Central Processing Unit), a storage device including a volatile memory such as a RAM (Random Access Memory) and a non-volatile memory such as a ROM (Read Only Memory), and an input / output interface (I / F) including an input / output circuit capable of transmitting and receiving signals or data.

[0062] The control device 40 judges whether the electric heater 4 in each lower header is overheated or not based on the detection values ​​of the plurality of first temperature sensors 10a and second temperature sensors 10b. In this embodiment, one first temperature sensor 10a and one second temperature sensor 10b are provided for each system, so the control device 40 judges overheating for each system.

[0063] There are two types of factors that cause the electric heater 4 to overheat. One is that scale (a deposit of impurities) adheres to the surface of the electric heater 4. When scale adheres to the heat generating area FA of the electric heater 4, heat dissipation from the heat generating area FA to the water is hindered. As a result, the temperature of the electric heater 4 rises more than usual. The other is that a part of the surface of the electric heater 4 is exposed without contacting the water due to a drop in the water level in the water pipe 3. When the heat generating area FA of the electric heater 4 does not contact the water, the surface dries (the water evaporates completely) and the temperature of that part rises more than usual. The control device 40 judges whether or not scale adheres to the surface of the electric heater 4 based on the detection values ​​of the first temperature sensor 10a and the second temperature sensor 10b. The control device 40 also judges whether or not the electric heater 4 is exposed (water level drops) based on the detection values ​​of the first temperature sensor 10a and the second temperature sensor 10b.

[0064] The control device 40 performs an overheating determination for each cause by comparing the detection values ​​of the first temperature sensor 10a and the second temperature sensor 10b with a predetermined threshold value.

[0065] Specifically, when the detection value of the first temperature sensor 10a or the second temperature sensor 10b is less than the first threshold T1, the control device 40 determines that no scale is attached to the surface of the electric heater 4, and when the detection value of the first temperature sensor 10a or the second temperature sensor 10b is equal to or greater than the first threshold T1, the control device 40 determines that scale is attached to the surface of the electric heater 4. Here, the temperature of the electric heater 4 when scale is attached to the heat generating area FA of the electric heater 4 under a predetermined operating condition, and the temperature of the electric heater 4 when scale is not attached to the heat generating area FA of the electric heater 4 (first threshold T1) can be obtained in advance by experiment or simulation, and are known data. For example, when the temperature of the electric heater 4 is controlled to 170 [°C] under normal operating conditions, the first threshold T1 is set to 185 [°C].

[0066] In addition, when the detection value of the first temperature sensor 10a or the second temperature sensor 10b is less than the second threshold T2, the control device 40 determines that the electric heater 4 is not exposed due to a drop in the water level, and when the detection value of the first temperature sensor 10a or the second temperature sensor 10b is equal to or greater than the second threshold T2, the control device 40 determines that the electric heater 4 is exposed. Here, the temperature of the electric heater 4 when the heat generation area FA of the electric heater 4 is in contact with water under a predetermined operating condition, and the temperature of the electric heater 4 when the heat generation area FA of the electric heater 4 is not in contact with water (the second threshold T2) can be obtained in advance by experiment or simulation, and are known data. The second threshold T2 is higher than the first threshold T1. For example, when the temperature of the electric heater 4 is controlled to 170 [°C] under normal operating conditions, the second threshold T2 is set to 200 [°C].

[0067] For example, when the detection value of the first temperature sensor 10a is equal to or greater than the threshold, the control device 40 determines that one or more of the six electric heaters 4 in the first system, i.e., the first lower header 2a, are overheated, and when the detection value is less than the predetermined threshold, the control device 40 determines that none of the electric heaters 4 in the first system are overheated. For example, when the detection value of the second temperature sensor 10b is equal to or greater than the threshold, the control device 40 determines that one or more of the six electric heaters 4 in the second system, i.e., the second lower header 2b, are overheated, and when the detection value is less than the predetermined threshold, the control device 40 determines that none of the electric heaters 4 in the second system are overheated.

[0068] When the control device 40 determines that the electric heater 4 of any system is overheated, the control device 40 performs a process of notifying an operator that overheating has occurred. The control device 40 performs the notification by controlling the notification device 42.

[0069] The notification device 42 notifies the user of the electric boiler 1 of notification information. Examples of the notification device 42 include at least one of a display device, a light-emitting device, and a sound output device. The display device includes a flat panel display such as a liquid crystal display (LCD) or an organic electroluminescence display (OLED). The light-emitting device includes a light source such as a light-emitting diode (LED). The sound output device includes a siren or a sound output device capable of generating a warning sound. The notification device 42 notifies the user of the electric boiler 1 of notification information using at least one of display data (characters or images) displayed on the display device, light emitted from the light-emitting device, and sound output from the sound output device. The notification information may include information identifying a system (either the first lower header 2a or the second lower header 2b) and information indicating that overheating has occurred in one or more electric heaters 4 in that system.

[0070] When the control device 40 determines that the cause of overheating is scale adhesion to the heat generating area FA of the electric heater 4, it controls the alarm device 42 to, for example, display data indicating that scale may be attached to the surface of the electric heater 4 or output light or sound indicating that scale may be attached. When the control device 40 determines that exposure of the electric heater 4 has occurred as the cause of overheating, it outputs, for example, a control signal to the power source 41 to stop the operation of the electric heater 4. When the detection values ​​of the first temperature sensor 10a and the second temperature sensor 10b fall below the first threshold value T1 and the second threshold value T2 and the control device 40 determines that the electric heater 4 is not overheated, it continues to monitor the detection values ​​without issuing an alarm or stopping the electric heater 4.

[0071] The process of the control device 40 based on the detection values ​​of the first temperature sensor 10a and the second temperature sensor 10b is an example and is not particularly limited. Instead of issuing a notification or stopping the electric heater 4, the control device 40 may perform other processes such as adjusting the power supply to the electric heater 4 or supplying water.

[0072] Furthermore, the first threshold T1 and the second threshold T2 may be set in multiple stages. For example, since scale adhesion progresses over time, the first threshold T1 may be set in multiple stages according to the degree of progress of scale adhesion. As the amount of scale adhesion increases, heat dissipation from the electric heater 4 is hindered and the temperature of the electric heater 4 is more likely to rise, so the degree of progress of scale adhesion can be determined based on the temperature detection value.

[0073] Furthermore, instead of or in addition to comparing the detection values ​​of the first temperature sensor 10a and the second temperature sensor 10b with the thresholds (first threshold T1, second threshold T2), the rate of increase in the detection values ​​of the first temperature sensor 10a and the second temperature sensor 10b during operation of the electric boiler 1 (i.e., the temperature gradient per unit time) may be taken into consideration.

[0074] That is, when scale is attached to the surface of the electric heater 4, the heat dissipation of the electric heater 4 is hindered by the scale, so the temperature of the electric heater 4 rises relatively slowly. On the other hand, when the heat generating area FA of the electric heater 4 is exposed without contacting water, the temperature of the electric heater 4 rises rapidly compared to the case of scale attachment. Therefore, when the rate of increase in the detection value of the first temperature sensor 10a or the second temperature sensor 10b is equal to or greater than the third threshold value and less than the fourth threshold value, that is, when the control device 40 determines that the temperature of the electric heater 4 is rising slowly, it can determine that scale is attached to the surface of the electric heater 4. Also, when the rate of increase in the detection value of the first temperature sensor 10a or the second temperature sensor 10b is equal to or greater than the fourth threshold value, that is, when the control device 40 determines that the temperature of the electric heater 4 is rising rapidly, it can determine that the electric heater 4 is overheated.

[0075] [effect] As described above, the electric boiler 1 of this embodiment includes a plurality of lower headers (2a, 2b), a plurality of water tubes 3 extending upward from each of the plurality of lower headers (2a, 2b), a plurality of electric heaters 4 provided inside each of the plurality of water tubes 3, an upper header 6 connected to each of the plurality of water tubes 3 via a riser tube 5, and a plurality of temperature sensors (10a, 10b) provided for each of the plurality of lower headers (2a, 2b) and arranged on the electric heater 4 of any of the water tubes 3 of each of the lower headers (2a, 2b). In this way, when the number of water tubes 3 (and electric heaters 4) is increased to increase the output of the electric boiler 1, the size of one lower header and the number of water tubes 3 to be installed can be limited to a range where uniformity of water quality and temperature distribution can be ensured by distributing the water tubes 3 among the plurality of lower headers (2a, 2b). Furthermore, since one temperature sensor (10a, 10b) is provided for each of the lower headers (2a, 2b), the temperatures of all the electric heaters 4 provided in one lower header can be represented by the detection value of one temperature sensor. This makes it possible to effectively reduce the number of temperature sensors compared to the number of water tubes 3. As a result, it is possible to provide an electric boiler 1 that is capable of appropriate temperature detection with a small number of temperature sensors, even when the number of water tubes 3 is increased.

[0076] In this embodiment, the electric boiler 1 further includes water supply pipes 9a, 9b connected to a plurality of lower headers (2a, 2b), and a temperature sensor (second temperature sensor 10b) is provided on the electric heater 4 of the first water pipe P1 that is closest to the connection position between the water supply pipes 9a, 9b and at least one of the lower headers (2a, 2b). Since new water that is not stored in the boiler body WS is supplied from the water supply pipes 9a, 9b, the first water pipe P1 is the water pipe 3 that is most susceptible to fluctuations in the water quality (concentration of hardness components) of the supplied water within the same system. For example, the hardness components of the water When the component concentration increases, scale is more likely to form on the surface of the electric heater 4. Because the water flowing through the water supply pipes 9a, 9b comes from the same supply source, it is considered that the effects of water quality fluctuations are similar in the first water pipe P1 of either system. Therefore, by installing a temperature sensor of either system (first temperature sensor 10a or second temperature sensor 10b) in the electric heater 4 of the first water pipe P1, overheating of the electric heater 4 caused by fluctuations in the quality of the supplied water can be detected early. Therefore, even if the number of temperature sensors is reduced, the effects of water quality fluctuations can be detected early.

[0077] In this embodiment, the electric boiler 1 further includes a downcomer pipe 8 connected to the upper header 6 or to the separator, branched at a branching portion 8a, and connected to each of the lower headers (2a, 2b). A temperature sensor (first temperature sensor 10a) is provided on the electric heater 4 of the second water pipe P2 that is closest to the connection position between the downcomer pipe 8 and at least one of the lower headers (2a, 2b). Since water with concentrated impurities is returned from the downcomer pipe 8 to the lower headers (2a, 2b), the second water pipe P2 is the water pipe 3 in the same system in which the impurity concentration of the water in the pipe is most likely to increase. When the impurity concentration of the water increases, scale (precipitate of impurities) is formed on the surface of the electric heater 4. The scale reduces the heat transfer performance of the electric heater 4, making the electric heater 4 more likely to overheat. Therefore, by branching the downcomer pipe 8 and distributing the concentrated water from the downcomer pipe 8 to each system at the branching portion 8a, and then installing a temperature sensor of one of the systems (the first temperature sensor 10a or the second temperature sensor 10b) in the electric heater 4 of the second water pipe P2, overheating of the electric heater 4 caused by an increase in the impurity concentration can be detected early. Therefore, even if the number of temperature sensors is reduced, the effect of an increase in the impurity concentration can be detected early.

[0078] In this embodiment, the lower headers (2a, 2b) extend in the X direction (first direction) in a horizontal plane and are arranged side by side in the Y direction (second direction) perpendicular to the X direction (first direction). The downcomer pipe 8 is connected to each of the lower headers (2a, 2b) at one end (X1 side) in the X direction (first direction), and the feed water pipes 9a, 9b are connected to each of the lower headers (2a, 2b) at the middle position in the X direction (first direction). In other words, the second water pipe P2 is the water pipe 3 at one end in the system, and the first water pipe P1 is the water pipe 3 at the center in the system. This allows the first temperature sensor 10a and the second temperature sensor 10b to obtain the temperature at the end and the temperature at the center of the lower header, respectively, although they are in separate systems. By limiting (dividing) the number of water pipes 3 installed in one lower header to ensure uniformity of water quality and temperature distribution, if the temperature distribution for each system can be considered to be equal or similar, the temperature distribution within the system can be estimated from the detection values ​​at the end and center. In other words, even if only one temperature sensor is installed for each system, information useful for understanding the situation within the system can be obtained by combining the detection values ​​of the first temperature sensor 10a and the second temperature sensor 10b for each system.

[0079] <Modification> In the embodiment, the first temperature sensor 10a is provided in the second water pipe P2 of the first lower header 2a, and the second temperature sensor 10b is provided in the first water pipe P1 of the second lower header 2b, but this is not limited to the example. The first temperature sensor 10a may be provided in the first water pipe P1, and the second temperature sensor 10b may be provided in the second water pipe P2. Each temperature sensor may be provided in a water pipe 3 other than the second water pipe P2 and the first water pipe P1.

[0080] In the embodiment, an example in which two lower headers are provided has been shown, but three or more lower headers may be provided. Also, the number of water pipes 3 provided in each lower header (2a, 2b) is not particularly limited and may be any number.

[0081] In addition, in the embodiment, an example in which the drain pipe 7 is provided with the communication portion 7a has been shown, but the drain pipe 7 may not be provided with the communication portion 7a, and the drain pipe 7 may be provided individually for each lower header (2a, 2b). Similarly, an example in which the downcomer pipe 8 is provided with the branch portion 8a has been shown, but the downcomer pipe 8 may not be provided with the branch portion 8a, and the downcomer pipe 8 may be provided individually for each lower header (2a, 2b). In these cases, a communication pipe that communicates the lower headers (2a, 2b) may be provided separately from the drain pipe 7 and the downcomer pipe 8.

[0082] In the embodiment, the water supply pipes 9a, 9b are connected to the lower headers (2a, 2b) at the middle positions in the X direction, but they may be connected to the ends in the X direction, or may be connected to multiple locations (for example, one end and the other end in the X direction). A water supply pipe may be provided only to one of the first lower header 2a and the second lower header 2b, and the first lower header 2a and the second lower header 2b may be connected to each other, thereby supplying water to both lower headers through one water supply pipe. Also, the water supply pipes 9a, 9b may have one water supply port. [Explanation of symbols]

[0083] 1...electric boiler, 2a...first lower header (lower header), 2b...second lower header (lower header), 3...water pipe, 4...electric heater, 4a, 4b, 4c...heater structure, 4d...terminal unit, 5...rising pipe, 6...upper header, 7...drain pipe, 7a...connecting section, 7b, 7c, 7d...pipe section, 8...downstream pipe, 8a...branching section, 8b, 8c, 8d...pipe section, 8e...connection port, 9a, 9b...feed pipe, 9c...pipe joint, 10a...first temperature sensor (temperature sensor), 10b...second temperature sensor (temperature sensor), 11...steam pipe, 12...steam valve, 13... Drain valve, 14...concentrated drain outlet, 15...concentrated drain valve, 16...water quality measuring section, 20...water supply device, 21...water supply branch section, 22...water supply pump, 23...water supply valve, 30...water level detector, 31...detector connecting pipe, 31a...upper connecting pipe, 31b...lower connecting pipe, 32...detection container, 33 (33A, 33B, 33C)...electrode rod, 40...control device, 41...power source, 42...alarm device, 50...mounting fixture, 51...wire, EG...boundary, FA...heat generating area, NA...non-heat generating area, P1...first water pipe, P2...second water pipe, SP1...water supply inlet, SP2...water supply inlet, WS...boiler body.

Claims

1. A plurality of lower headers; a plurality of water pipes extending upwardly from each of the plurality of lower headers; a plurality of electric heaters provided inside each of the plurality of water tubes; an upper header connected to each of the plurality of water pipes via a riser pipe; a plurality of temperature sensors, each provided for each of the plurality of lower headers, disposed on the electric heater of the water pipe of any of the respective lower headers; Electric boiler.

2. a water supply pipe connected to the plurality of lower headers; a temperature sensor is provided on the electric heater of a first water pipe closest to a connection position between the water supply pipe and at least one of the lower headers; 2. The electric boiler of claim 1.

3. a downcomer connected to the upper header or to the separator, branched at a branching portion and connected to each of the plurality of lower headers; a temperature sensor is provided on the electric heater of a second water pipe closest to a connection position between the downcomer pipe and at least one of the lower headers; 3. An electric boiler as claimed in claim 2.

4. the plurality of lower headers extend in a first direction in a horizontal plane and are arranged side by side in a second direction perpendicular to the first direction, The downcomer pipe is connected to each of the plurality of lower headers at one end side in the first direction, the water supply pipe is connected to each of the plurality of lower headers at an intermediate position in the first direction; 4. An electric boiler as claimed in claim 3.

5. a first lower header extending in a first direction in a horizontal plane; second lower headers arranged side by side in a second direction perpendicular to the first direction in the horizontal plane; a plurality of water pipes extending upward from each of the first lower header and the second lower header; a plurality of electric heaters provided inside each of the plurality of water tubes; an upper header connected to each of the first lower header and the second lower header via a riser pipe; a downcomer pipe connected to the upper header, branched at a branching portion and connected to each of the first lower header and the second lower header; a water supply pipe connected to the first lower header and the second lower header, a first temperature sensor disposed on the electric heater of a first water pipe closest to a connection position between the downcomer pipe and the first lower header; a second temperature sensor disposed on the electric heater of a second water pipe closest to a connection position between the water supply pipe and the first lower header; Electric boiler.

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