JP5969184B2 - Induction heating device - Google Patents

Description

  The present invention relates to an induction heating apparatus.

  In recent years, induction heating (IH) devices using the principle of electromagnetic induction have become widespread (see, for example, Patent Documents 1-4). The induction heating device has good heating efficiency and easy temperature control.

JP 2008-082700 A JP 2003-123949 A JP 2003-100426 A JP 2001-250666 A

  When the fluid flowing in the pipe is induction-heated, if the heating element disposed in the pipe is heated by electromagnetic induction, it is difficult to uniformly heat the fluid. Therefore, as in Patent Documents 1 to 3 described above, by arranging a large number of members having excellent thermal conductivity in the pipe, it is possible to achieve uniformity when heating the fluid. However, even in such a configuration, the vicinity of the center in the tube is heated by heat transfer, so that the heating power is higher than that in the vicinity of the wall surface in the tube where the heating element generating heat by induction heating is arranged. Inferior. Such a tendency becomes conspicuous as the diameter of the pipe through which the fluid flows increases, and a temperature difference occurs between the vicinity of the center of the pipe and the periphery thereof.

  In order to solve such problems caused by thermal conductivity, for example, as described in Patent Document 4, it has been devised to use a heat pipe having excellent thermal conductivity. Therefore, even if the current of the induction coil is adjusted, the thermal response of the fluid is slow, and if the allowable temperature conditions are severe, temperature control is difficult.

  For example, in the process of manufacturing a film using various solvents and plasticizers, heated air having a temperature corresponding to the boiling point of each chemical solution is blown, but the allowable temperature condition is the quality of the product. From the standpoint of ensuring that the temperature is limited to a very narrow range, precise temperature control is required.

  This application is made in view of the said matter, and makes it a subject to provide the induction heating apparatus which improves the thermal uniformity of the fluid to heat, and is excellent also in controllability of temperature control.

  In order to solve the above-mentioned problems, the present invention provides an electromagnetic coil in which a conductive tubular member is disposed in a flow path through which a fluid passes and an alternating current for generating heat by electromagnetic induction is passed through the tubular member. I decided to place it inside.

  More specifically, the present invention relates to an induction heating apparatus for heating a fluid, and is a conductive tubular member disposed in a flow path through which the fluid passes, and the tubular member and the electric member inside the tubular member. And an electromagnetic coil that flows along the longitudinal direction of the tubular member without contact and that flows an alternating current that causes the tubular member to generate heat by electromagnetic induction.

  Non-metallic fluids such as air and water have remarkably lower thermal conductivity than metals, so it is difficult to raise the temperature of the fluid uniformly only by arranging a high-temperature heat source in the flow path. Therefore, it is conceivable to arrange the heat source evenly in the flow path. For example, when an electric heater is used as the heat source, precise temperature control is realized by various restrictions such as the amount of heat required and the allowable current of the coil. It is difficult to construct a circuit. On the other hand, according to the principle of induction heating, it is known that precise temperature control can be easily realized by controlling the current flowing through the electromagnetic coil.

  Here, when the principle of induction heating is used, it is generally possible to generate an eddy current in the member by arranging a conductive member inside the wound electromagnetic coil to generate heat. However, in this case, the fluid to be heated must flow through the conductive member disposed inside the electromagnetic coil. According to such an aspect, the vicinity of the center of the flow path formed inside the conductive member inevitably becomes lower in temperature than the peripheral portion, and uniform temperature rise of the fluid cannot be realized.

  Therefore, the induction heating device has an electromagnetic coil disposed inside the conductive tubular member, so that the flow path for flowing the fluid is from the inside of the conventional electromagnetic coil to the outside of the tubular member in which the electromagnetic coil is installed. By doing so, the restriction when configuring the flow path is eliminated. This makes it possible to freely arrange the tubular member that generates heat by induction heating in the flow path, and to improve the thermal uniformity of the fluid to be heated and the controllability of temperature adjustment. Become.

  Here, a large number of the tubular members may be arranged in the flow path, and the electromagnetic coil may be formed so that one conductive wire passes through the tubular members in order. If the induction heating device is configured in this way, each tubular member generates heat almost uniformly, so that it is possible to improve the thermal uniformity of the fluid to be heated.

  The tubular member is disposed in the flow path so as to intersect the fluid flow direction, and the induction heating device has a heat transfer surface extending along the fluid flow direction, and at least A fin that is fixed to the tubular member and transmits heat of the tubular member from the heat transfer surface to the fluid may be further provided. If the induction heating device is configured in this way, the heat of the tubular member is quickly transmitted to the fluid via the fins, so that the thermal uniformity of the fluid to be heated is further improved, and the temperature adjustment is performed. The controllability can be further improved. Further, the fins do not disturb the fluid flow.

  Further, a temperature sensor for measuring the temperature of the fluid downstream from the tubular member is further provided, and the alternating current that is controlled so that the temperature sensor has a predetermined temperature flows through the electromagnetic coil. May be. By controlling the current flowing through the electromagnetic coil in this way, the effect of controllability with high temperature adjustment that the induction heating device has is effectively exhibited.

  If it is the said induction heating apparatus, the thermal uniformity of the fluid to heat improves and it is excellent also in controllability of temperature control.

It is the figure which showed an example of the system configuration at the time of applying the induction heating apparatus which concerns on embodiment to the dryer process of the line which produces a film. It is a block diagram of the induction heating apparatus which concerns on embodiment. It is an internal structure figure at the time of seeing a fluid heating unit from the front. It is sectional drawing of the pipe member which penetrated the electromagnetic coil. It is a side view of a fluid heating unit. It is the figure which showed the outline | summary of the circuit of the induction heating apparatus which concerns on embodiment. It is the figure which showed the outline | summary of the circuit of the induction heating apparatus which concerns on a prior art example. It is the figure which showed the outline | summary of the comparative experiment. It is an arrangement view of a temperature sensor. It is the table | surface which showed the experimental result of the induction heating apparatus which concerns on embodiment. It is the table | surface which showed the experimental result of the fluid heating unit using the electric heater which concerns on a prior art example.

  Hereinafter, embodiments of the present invention will be described. The following embodiment shows one aspect of the present invention, and the technical scope of the present invention is not limited to the following embodiment.

  FIG. 1 shows a system configuration when the induction heating device according to the embodiment is applied to a dryer process of a line for producing a film. The induction heating device 1 according to the present embodiment is built in a hot air supply device 3 provided with a blower 2 and heats air blown into a casing 5 through which a film 4 passes. In plants for manufacturing various products, experimental facilities for performing various experiments, etc., for example, a facility for supplying hot air may be required as in the dryer process shown in FIG.

  In particular, in the film drying process, air at various temperatures may be required. Here, if the temperature of the hot air when removing various solvents used for film production or drying is not accurately adjusted, substances contained in the air may cause chemical changes, resulting in Highly accurate temperature control is required because it can have serious effects. Therefore, the induction heating device 1 according to the present embodiment is configured as follows to supply hot air whose temperature is accurately adjusted.

  The configuration of the induction heating device 1 is shown in FIG. As shown in FIG. 2, the induction heating device 1 includes a fluid heating unit 6, a temperature monitoring box 7, a high frequency power supply device 8, and a cooling water circulation device 9. The induction heating device 1 is connected to a single-phase 100V AC power source and a three-phase 200V AC power source. In FIG. 1, the induction heating device 1 is illustrated across the inner surface flow path of the hot air supply device 3, but only the fluid heating unit 6 is arranged in that way, and other devices (temperature monitoring box 7, The high-frequency power supply device 8 and the cooling water circulation device 9) are preferably arranged outside the hot air supply device 3 or outside the flow path such as the member space of the hot air supply device 3.

  The fluid heating unit 6 is a device that electrically heats the air sucked into the blower 2, and is appropriately adjusted based on a signal from a temperature monitoring box 7 that monitors the temperature by a temperature sensor installed in the fluid heating unit 6. When a high-frequency current from the high-frequency power supply device 8 flows through an electromagnetic coil, which will be described later, a tube member, which will be described later, becomes hot and air sucked into the blower 2 is heated. In order to prevent overheating, the blower 2 is generally arranged upstream of the heater. However, in order to heat the air more uniformly by stirring, the blower 2 is disposed downstream of the fluid heating unit 6 as a heater. You may arrange. In that case, the blower 2 is desirably made of a member having high heat resistance so that the operation can be continued even when high-temperature air flows.

  The temperature monitoring box 7 sends the signal of the temperature sensor installed in the fluid heating unit 6 to the high frequency power supply device 8.

  The high frequency power supply device 8 incorporates an inverter circuit that generates a high frequency current, and can generate an alternating current of several tens of kHz to supply the high frequency current to the electromagnetic coil of the fluid heating unit 6. The high frequency power supply device 8 controls the output based on the temperature information sent from the temperature sensor via the temperature monitoring box 7, and the specific control target may be any of current, voltage, and power.

  The cooling water circulation device 9 is a device that circulates while cooling the cooling water passing through the electromagnetic coil of the fluid heating unit 6, and is connected to both ends of the electromagnetic coil of the fluid heating unit 6 via the cooling water hose 10. Yes. The electromagnetic coil not only inductively heats a heating element (corresponding to a tube member to be described later), but also generates heat when current flows. Further, since there is radiation from a heating element that generates heat by induction heating, the electromagnetic coil becomes extremely hot. When the temperature of the electromagnetic coil becomes high, there is a possibility of causing problems such as a reduction in heating efficiency or disconnection. Therefore, the cooling water circulating device 9 cools the electromagnetic coil by passing cooling water through the tubular electromagnetic coil. The temperature of the cooling water is preferably a temperature that prevents melting of the electromagnetic coil and does not cause an electrical trouble due to condensation, and is about 25 to 35 ° C., for example.

  The cooling water circulation device 9 includes a cooling water tank 11, a heat radiating unit 12, and a circulation pump 13 in order to cool the electromagnetic coil. The cooling water circulating device 9 is configured such that the cooling water heated through the electromagnetic coil is cooled by the heat radiating unit 12 and the cooling water in the cooling water tank 11 is fed into the pipe of the electromagnetic coil by the circulation pump 13. Cool continuously.

  The cooling water fed into the electromagnetic coil pipe is boosted to an appropriate pressure by the circulation pump 13 and then fed into the electromagnetic coil pipe. The pump and the circulation path are designed so that the discharge pressure of the circulation pump 13 is, for example, about 0.5 MPa so that a sufficient amount of cooling water circulates even in the pipe of the electromagnetic coil having a small inner diameter.

  In order to prevent overheating of the electromagnetic coil due to the abnormality of the cooling water circulation device 9, a flow switch 14 is provided in the circulation path of the cooling water, and the flow switch 14 indicates that the circulation of the cooling water has stopped for some reason. Is detected, the high frequency power supply 8 is stopped.

  FIG. 3 shows the internal structure when the fluid heating unit 6 is viewed from the front. As shown in FIG. 3, the fluid heating unit 6 includes a casing 24, pipe members 15, fins 16, and electromagnetic coils 17. The air sucked into the blower 2 flows inside the casing 24 in a direction perpendicular to the paper surface of FIG.

  The casing 24 is a square frame-shaped member made of SEHC (electrogalvanized steel plate), and is a member that forms a part of a flow path of air sucked into the blower 2. That is, the casing 24 opens in a direction orthogonal to the paper surface of FIG.

  The pipe member 15 is an SGP pipe (carbon steel pipe for piping) having a nominal diameter of 10 A, and a large number of straight pipes extending in a direction orthogonal to the direction of travel of air sucked into the blower 2 are arranged inside the casing 24. . The pipe member 15 is supported by plate-like support members 18 arranged on both sides of the casing 24. However, the support member 18 is not necessarily provided as long as the tube member 15 can be sufficiently supported by alternative means such as the casing 24. . In addition, although the pipe member 15 is not limited to the thing using such a raw material, in order to make it a heat generating body at the time of performing induction heating, it needs to be an electroconductive member. The tube member 15 is not limited to such a straight tube, and the tube member 15 may be bent in the middle as long as the electromagnetic coil 17 is flexible. Moreover, although the electromagnetic coil 17 may be exposed, the edge part of the pipe member 15 connects the both ends of the adjacent pipe member 15 in U shape, for example, and the U-shaped part of the electromagnetic coil 17 is a pipe member. You may make it cover. In this case, if a non-conductor such as ceramic is used for the U-shaped portion, heat generation of the U-shaped portion can be prevented.

The fins 16 are plate-shaped SGCCs (hot dip galvanized steel sheets) arranged at regular intervals, and by ensuring a sufficiently large heat transfer area so that the heat of the tube member 15 is sufficiently transferred to the air. , Increase the heating efficiency. The fins 16 are arranged so that the heat exchange surfaces extend along the traveling direction of the air sucked into the blower 2, and are joined to the tube members 15 penetrating the heat exchange surfaces, so that the heat of the tube members 15 can be obtained. Is transmitted to the fin 16. As long as heat can be transferred from the tube member 15 to the fin 16, the joint may be mechanically pressure-bonded or welded. The thickness and pitch of the fins 16 are appropriately determined according to the flow rate of air, the air volume, and the amount of heat generated by induction heating. For example, the thickness is 0.3 mm and the pitch is about 3 to 5 mm.

  The material of the fin 16 may be any material as long as it has excellent heat conductivity and heat resistance, and may be, for example, a copper plate or an aluminum plate.

  The electromagnetic coil 17 is a copper tube having an outer diameter of 10 mm and an inner diameter of 8 mm. The electromagnetic coil 17 is disposed inside each tube member 15 so as to pass through each tube member 15 in turn while bending and meandering at the end of each tube member 15. It is inserted. A cross section of the tube member 15 through which the electromagnetic coil 17 is inserted is shown in FIG. The electromagnetic coil 17 has a silicon coating on the surface of the electromagnetic coil 17 so as not to be in electrical contact with each tube member 15. Inside the electromagnetic coil 17, the cooling water of the cooling water circulation device 9 described above flows.

  A side view of the fluid heating unit 6 is shown in FIG. As shown in FIG. 5, the electromagnetic coil 17 is bent at the end of each pipe member 15, and is repeatedly meandered by being inserted into the adjacent pipe member 15, and finally all the pipe members 15 are It has come to pass. Then, both ends of the electromagnetic coil 17 indicated by reference signs A and B are electrically connected to the high frequency power supply device 8 via an electric cable, and both ends of the pipe line inside the electromagnetic coil 17 are connected to the cooling water hose 10. Is connected to the cooling water circulation device 9.

In the induction heating apparatus 1 configured as described above, when the power supply is turned on, the circulation pump 13 of the cooling water circulation device 9 is activated to start circulation of the cooling water, and the high frequency power supply device 8 supplies a high frequency current to the electromagnetic coil 17. Shed. When a high-frequency current flows through the electromagnetic coil 17, the tube member 15 made of metal has a direction (Lenz's law) that cancels the high-frequency magnetic field generated around the electromagnetic coil 17, in other words, a current flowing through the electromagnetic coil 17. Eddy current flows in the opposite direction. An outline of the circuit of the induction heating apparatus 1 is shown in FIG. When a high-frequency current flows through the electromagnetic coil 17 and an eddy current flows through the tube member 15, the tube member 15 has an electrical resistance. Therefore, Joule heat represented by the following Equation 1 is generated according to Joule's law. At this time, since the eddy current flowing through each tube member 15 becomes uniform, each tube member 15 is heated uniformly.

  As shown in FIG. 7, this induction heating device 1 is not configured as a conventional general induction heating device in which an electromagnetic coil is wound around the outside of a heating element, but an electromagnetic coil 17 is provided inside a tube member 15. Since it is configured to be inserted, an eddy current flows in the axial direction (longitudinal direction) of each tube member 15, but each tube member 15 is formed of substantially the same diameter and the same material as a whole from one end side to the other end side. Since the electric resistance in the axial direction is uniform, the current flowing in the axial direction is also uniform as a whole.

The input power input to the heating element (corresponding to the tube member 15) in induction heating is proportional to the skin resistance of the heating element and proportional to the square of the strength of the magnetic field that is the source of eddy current. The skin resistance of the heating element is proportional to the square root of the electrical resistivity and permeability of the material constituting the heating element and the frequency of the current flowing through the electromagnetic coil. Here, in order to effectively generate heat from the heating element, the input power may be increased so that the eddy current flowing in the heating element itself increases. Therefore, in order for the air passing through the induction heating device 1 to reach a desired temperature, the current and frequency flowing through the electromagnetic coil 17 may be increased so that the input power has an appropriate magnitude.

  When the current flowing through the electromagnetic coil 17 is increased, it is necessary to reduce the loss and the breakdown voltage of the electromagnetic coil 17. Specifically, the thickness and thickness of the electromagnetic coil 17 are appropriately selected and the silicon coating is strengthened. It is necessary to take such measures. Further, when the frequency of the current flowing through the electromagnetic coil 17 is increased, the number of times the semiconductor switching element of the high frequency power supply device 8 is turned on and off increases in proportion to the frequency, so that an increase in switching loss of the semiconductor switching element is suppressed. Therefore, for example, it is preferable to provide a zero current switching circuit or the like to reduce the loss during switching.

  With the induction heating device 1 configured as described above, the entire tube member 15 generates heat uniformly by induction heating. Thereby, the air which passes the inside of the induction heating apparatus 1 can be heated. In addition, since the amount of heat that can be held by the tube member 15 is smaller than the amount of heat generated by induction heating of the electromagnetic coil 17, the temperature of the tube member 15 quickly increases when the magnitude or frequency of the current flowing through the electromagnetic coil 17 is changed. Follow. Therefore, the air sent to the blower 2 can be precisely and quickly adjusted to a desired temperature by controlling the magnitude and frequency of the current flowing through the electromagnetic coil 17.

A comparative experiment was performed between the induction heating apparatus 1 according to the present embodiment and a conventional example using an electric heater. FIG. 8 is a diagram showing an outline of this comparative experiment. In this comparative experiment, an experimental blower 21 is placed in an experimental duct 20 in which a fluid heating unit 6 of the induction heating apparatus 1 or a fluid heating unit using an electric heater is installed as a test sample indicated by reference numeral 19 in FIG. And air is sent into the experimental duct 20 by the blower 21. A temperature sensor 22 _-U is provided on the upstream side of the specimen 19, and a sensor 22 _-D for detecting the wind speed and temperature is provided on the downstream side of the specimen 19. In addition, a thermo camera 23 that measures the temperature distribution of the specimen 19 with infrared rays is provided on the downstream side of the experimental duct 20. Note that five temperature sensors 22 _-U and five temperature sensors 22 _-D are provided, and are arranged as shown in FIG.

  The table | surface which showed the experimental result is shown in FIG. 10 and FIG. FIG. 10 is a table showing experimental results of the induction heating apparatus 1 according to this embodiment, and FIG. 11 is a table showing experimental results of a fluid heating unit using an electric heater according to a conventional example. The circled numbers shown in the tables of FIGS. 10 and 11 correspond to the positions of the temperature sensors indicated by the circled numbers in FIG. 9 described.

  As is clear from the comparison between the two tables shown in FIGS. 10 and 11, in the case of the fluid heating unit using the electric heater according to the conventional example, the temperature of the air on the outlet side varies greatly depending on the measurement site. Near the center of the duct is extremely hot. That is, temperature unevenness is remarkable. On the other hand, in the case of the fluid heating unit of the induction heating apparatus 1 according to this embodiment, the temperature of the air on the outlet side is uniform regardless of the measurement site. From this, it can be seen that the induction heating device 1 according to the present embodiment can precisely adjust the air sent to the blower 2 to a desired temperature.

  Although not shown in the drawing, the temperature distribution of the specimen 19 as seen by the thermography obtained by the thermo camera 23 has a clear temperature distribution variation in the case of the fluid heating unit using the electric heater according to the conventional example. In contrast, in the case of the fluid heating unit of the induction heating apparatus 1 according to the present embodiment, a significant variation in the temperature distribution could not be confirmed.

  From this experimental result, since the induction heating apparatus 1 can control the temperature with high accuracy, for example, a severe temperature condition is imposed from the viewpoint of preventing a chemical change of the solvent as in the film drying process. It can be seen that even if it is applied to a certain process, the product is hardly affected.

  On the other hand, if dry air is controlled to a specified temperature range while using an electric heater and current is turned on and off using a thermistor, the temperature will constantly change over time, so it should be applied to processes that require precise temperature control. Is difficult. Furthermore, in the case of an electric heater, as is apparent from the above experimental results, the temperature of air varies depending on the location in the duct, and the temperature unevenness is significant. May cause trouble. As a measure to eliminate such temperature unevenness, it is conceivable to place an electric heater in the entire duct. There is a risk of shrinking. On the other hand, in the induction heating device 1, since the temperature is precisely controlled at a substantially constant temperature, mechanical stress due to contact damage of an electric circuit due to repeated on / off, such as an electric heater, or expansion / contraction due to thermal change is applied. I don't give it.

  In the above embodiment, the configuration and operation of the induction heating apparatus 1 have been described by taking as an example a case where the present invention is applied to a dryer process of a film production line, but the present invention is limited to such an embodiment. It is not a thing. That is, the induction heating device according to the present invention is suitable for use in a place where it is desirable to improve the thermal uniformity of the fluid to be heated or a place where precise temperature control is required. In addition, the present invention can be applied to any scene as long as the fluid is simply heated, regardless of the required thermal uniformity and controllability. The fluid to be applied is not limited to air as in the above embodiment, and may be, for example, a gas or liquid other than air.

1 .. Induction heating device, 2 .... Blower, 3 .... Hot air supply device, 4 .... Film, 5, 24 ... Casing, 6 .... Fluid heating unit, 7 .... Temperature monitoring box, 8 .... High frequency Power supply device, 9 ... Cooling water circulation device, 10 ... Cooling water hose, 11 ... Cooling water tank, 12 ... Heat radiation part, 13 ... Circulation pump, 14 ... Flow switch, 15 ... Pipe member, 16 ... · Fins, 17 · · Electromagnetic coils, 18 · · Support members, 19 · · Test specimens, · · · Test ducts, 21 · · Blowers, 22 _-U · · Temperature sensor, 22 _-D · · · sensor, 23・ Thermo camera

Claims (4)

An induction heating device that is built in a hot air supply device and heats a fluid flowing through an air path in the hot air supply device ,
A conductive tubular member disposed in a flow path through which the fluid passes;
The tubular member extends in the axial direction of the tubular member along the longitudinal direction of the tubular member without being in electrical contact with the tubular member, and the tubular member is electromagnetically induced. And an electromagnetic coil through which an alternating current that generates heat is generated ,
In the electromagnetic coil, cooling water flows inside.
Induction heating device. A large number of the tubular members are arranged in the flow path,
The electromagnetic coil is formed so that one conductive wire passes through the tubular members in order.
The induction heating apparatus according to claim 1. The tubular member is disposed in the flow path so as to intersect the flow direction of the fluid,
The induction heating device further includes a fin having a heat transfer surface extending along a flow direction of the fluid, and being fixed to at least the tubular member and transferring heat of the tubular member from the heat transfer surface to the fluid.
The induction heating apparatus according to claim 1 or 2. A temperature sensor for measuring the temperature of the fluid downstream from the tubular member;
The alternating current that is controlled so that the temperature sensor has a predetermined temperature flows through the electromagnetic coil.
The induction heating device according to any one of claims 1 to 3.

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