JPH0668993B2 - Low frequency electromagnetic induction heater - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to a low frequency electromagnetic induction heater. More specifically, it relates to a low-frequency electromagnetic induction heater in which the temperature difference between the heater and the object to be heated is extremely low.

[Prior art]

In a power plant, a factory, etc., oil, coal, natural gas, etc. are generally used as a heat source of steam or hot water and burned. On the other hand, some small-sized and small-capacity ones use an electric resistance heater as a heat source because of their simplicity, and small-sized boilers and the like use oil or natural gas. As another heating method, a low-frequency electromagnetic induction heater is known (Japanese Utility Model Publication No. 56-86789, Japanese Patent Publication No. 58-395).
No. 25 bulletin).

[Problems to be Solved by the Invention]

However, when petroleum, coal, natural gas, etc. are burned and used for boilers, etc., the temperature difference between the heating part and the water of the heated object is too large, so-called scale adheres, the heat transfer coefficient decreases, and finally Has the problem that the pipe will break. For this reason, the water supplied to the boiler needs to be defoamed (deoxygenated) by using a chemical agent, or must be subjected to a scale preventive treatment by maintaining alkalinity. Also, the system that burns oil, coal, natural gas, etc. to make steam, and circulates this steam throughout the building to make it a heating source etc. is widely practiced in hotels and the like.
It is not always an efficient system because it has a lot of energy loss. Also, when an electric resistance heater is placed in water, it is heated near the heat source at a temperature much higher than 100 ° C, which is the boiling point of water, so using a heater that does not have a sufficient interface heat transfer surface area causes various obstacles. Occurs. That is, there were the following problems. Unless the electric power is less than ² W per 1 cm ² , the heat transfer to water will decrease and the heater element inside will break. Since the voltage applied to the heater is 200V to 400V, sufficient insulation must be provided. On the contrary, since this electric insulator serves as a heat insulating material for temperature, heat transfer to water is hindered. When the heat transfer of water deteriorates, the surface temperature of the heater rises,
When water molecules come into contact with the surface of the heater, a steam explosion occurs, resulting in the so-called "bending" (bumping) phenomenon. Not only is such a "bounce" phenomenon dangerous, there is the fundamental problem of extremely low thermal efficiency. Moreover, electric resistance heaters, like gas combustion,
Since the temperature difference between the heating source and water is too large, the inorganic and organic components contained in the water are adsorbed and deposited on the surface of the heater, and this acts as a heat insulating material, reducing the heat transfer, How water boiled worse. At the same time, the heat radiation of the heater also deteriorates, which eventually leads to the accident of the heater breaking. In order to avoid this accident, the water heater has a large surface area and is filled in the water tank, which has been a problem from the point of view of the complexity of heater replacement and reliability. In addition, there is a problem in that it takes a lot of time and effort for cleaning due to adhesion of water stains. Furthermore, the problem that could not be basically improved was that a large Bach tank was required to accurately control the temperature of the hot water, and the size could not be reduced. Furthermore, the low-frequency electromagnetic induction heaters proposed in Japanese Utility Model Publication No. 56-86789 and Japanese Patent Publication No. 58-39525 have not been optimized in design yet and the temperature difference between the heating source and the object to be heated is It was high and the thermal efficiency was not good. In order to solve the above-mentioned problems of the prior art, the present invention uses an electric induction heating method applying a low voltage-high current short-circuit transformer, eliminates a gap between an induction coil and a metal pipe, and conducts heat. By filling the mold resin for improving the property, the temperature difference between the heating part and the object to be heated is reduced,
It is an object of the present invention to provide a device that is reliable and durable and that can perform stable heating for a long period of time.

[Means for Solving the Problems]

In order to achieve the above object, the low-frequency electromagnetic induction heater of the present invention is a low-frequency electromagnetic induction heater in which an induction coil is wound around an iron core, and a metal pipe is provided around the iron coil. A resin mold is provided between the pipe and the metal pipe, and when viewed from the cross-sectional direction of the metal pipe, no substantial gap is provided between the surface of the induction coil and the surface of the metal pipe. To do. In the above configuration, it is preferable that the low frequency power source is a commercial frequency power source. Further, in the above structure, at least two metal pipes are used.
It is preferable that the metal pipes of the layers are integrated. Further, in the above structure, the resin mold is preferably made of a heat resistant resin. Further, in the above structure, it is preferable that the supplied power is 3 W or more per 1 cm ² of surface area of the metal pipe.

[Action]

According to the above-described configuration of the present invention, by using an electric induction heating method applying a low voltage-high current short-circuit transformer, by eliminating a gap between the induction coil and the metal pipe, the heating unit and The temperature difference between the heating element and the heating element can be reduced, the thermal efficiency is good, the reliability and durability are high, and the apparatus can perform stable heating for a long period of time. In addition, the heating area can be increased and the supplied power can be increased. Furthermore, since it is resin-molded, it has excellent thermal conductivity and can prevent the phenomenon that the temperature inside the pipe or coil becomes abnormally high. Further, according to the preferable configuration of the present invention in which the low frequency power source is a commercial frequency power source, the commercial frequency power can be directly converted into Joule heat, which is convenient for use. Further, according to the preferable configuration of the present invention in which the metal pipe is a pipe in which at least two layers of metal pipes are integrated, a metal that easily generates Joule heat is an environmental resistance (for example, a metal that does not cause rust). ) And (3) are integrated, it can be stably used as a whole for a long period of time. Further, according to the preferable configuration of the present invention in which the resin mold is made of a heat resistant resin, it is possible to continue heating stably even if the inside of the pipe reaches a certain temperature. Furthermore, according to the preferable configuration of the present invention in which the supplied power is 3 W or more per 1 cm ² of surface area of the metal pipe, a large heating area can be obtained, so that large heating energy can be generated.

【Example】

An embodiment of the present invention will be described below with reference to the drawings. 1 (A) and (B) are sectional views showing an embodiment of the present invention. FIG. 1 (A) shows an example in which the pipe has one layer, and FIG. 1 (B) shows an example in which the pipe has two layers. Figure 1 (A) (B)
In the low frequency electromagnetic induction heater 6 in which the induction coil 2 is wound around the iron core 1 and the metal pipe 3 or the metal pipe 4 is provided around the induction coil 2, between the induction coil 2 and the metal pipe 3 around the induction coil 2. A resin mold 5 is applied to the low-frequency region where there is substantially no gap between the surface of the induction coil 2 and the surface of the metal pipe 4 when viewed from the cross-sectional direction of the metal pipes 3 and 4. The electromagnetic induction heater 6. The first characteristic requirement in the present invention is that the resin mold 5 is provided between the induction coil 2 and the metal pipe 3 surrounding the induction coil 2.
Is the point. By doing so, the heating efficiency is significantly improved. For example, when boiling water is taken as an example, the inside of the induction coil is about 500 without a resin mold.
On the other hand, when the resin mold is applied, the temperature can be increased only up to about 130 ° C. Therefore, this has an important meaning to reduce the temperature difference between the heating source and the object to be heated. Next, the second characteristic requirement of the present invention is that no substantial gap is provided between the surface of the induction coil 2 and the surface of the metal pipe 4. For example, no gap is provided between the pipes 3 and 4 even when two types of heating pipes are used. As a result, the heat transfer property can be improved and the thermal efficiency can be increased. As the resin used as the resin mold in the above, any resin can be used as long as it is for molding. For example, epoxy-based, acrylic-based, vinyl-based, phenol-based, silicone-based, polyester-based, and other heat-resistant resins. Of these, thermosetting resins having a heat resistance of 100 ° C. or higher are preferable. Further, as the resin mold, any known means such as vacuum casting, compression casting, and pouring casting can be adopted. Any mold resin may be used as long as it has heat conductivity, insulation and heat resistance. As one usage method, for example, aluminum fine particles or silica fine particles may be added to the resin and used as a compound. This is preferable because the thermal conductivity is improved. In addition, in FIGS. 1A and 1B, it is particularly preferable that the molded resin also exists in the induction coil 2. This is because the presence of resin in the induction coil 2 effectively removes the heat generated in the coil. In the above, the heater 6 comprising an iron core, a coil, and a pipe
Can be used either vertically or horizontally. Next, the heat generation principle of the present invention will be described with reference to FIG. Second
FIG. A is a diagram showing the principle of a transformer. Ie coil
100V, 10A AC (50Hz or 60H) on the primary side wound 100 times
When a current of z) is passed, theoretically a 100V, 10A AC (50Hz or 60Hz) current flows in the opposite direction as an additional current on the secondary side where the coil is wound 100 times. Next, as shown in FIG. 2B, when the coil on the secondary side is wound once and an alternating current is similarly applied to the primary side, an induced current of 1 V and 1000 A flows in the opposite direction on the secondary side. That is, a low-voltage, large-current short-circuit transformer can be achieved. The present invention is an application of the above-described principle of a short-circuit transformer of low voltage and large current, in which an induction coil is arranged on the primary side and a metal pipe is arranged on the secondary side. The secondary metal pipe of the present invention is
Any conductive metal may be used. For example, it is made of copper or steel. As shown in FIG. 2B, a large current flows through a metal pipe (for example, a copper pipe), so that it is extremely effective for heating. That is, it is considered that Joule heat due to a short-circuit current is generated by the flow of a large alternating current, and this is effective for heat generation. In this sense, the voltage is not effective for heating. Therefore, in the present invention, it is significant that a large current that is truly effective for heating is taken out of the electric power. In addition, an extremely low voltage flows through the copper pipe on the secondary side, but this is so safe that it does not cause an electric shock even if the human body touches it. In addition, according to the principles of the present invention, the heated area is necessarily large. This is because the metal pipe is arranged outside the coil. Moreover, the power consumption per unit area can be increased. Accordingly, in the present heater metal pipe surface area 1 cm ² per 3W or more, or can be operated satisfactorily even 1 cm ² per 4W or more. Since the heating area is large, the temperature difference ΔT between the heating portion and the object to be heated can be reduced. That is, it is possible to exert a synergistic effect that the heating area can be increased and the supplied power can be increased. FIG. 3 shows a model of the heating unit of the present invention. An induction coil 2 is wound around an iron core 1, and a metal pipe (heating pipe) 3 is arranged around the induction coil 2. Since a current having a commercial frequency is applied to the induction coil 2 and the metal pipe 3 is heated, if an object to be heated such as water is present outside the pipe, heat is taken from the metal pipe to remove heat. In the description of FIG. 1, the metal pipes 3 and 4 are shown as pipes in which two pipes are bonded and integrated, but the metal pipe may be made of one type of simple substance (for example, a pipe made of stainless steel alone). Or a single pipe of copper), or two or more pipes may be integrated and used so that there are no voids. In this example, the inner pipe 3 may be made of copper in order to improve the heat transfer property, and the outer pipe 4 may be made of stainless steel in order to improve durability and corrosion resistance. That is, it can be used properly according to the purpose. Further, in order to integrate (clad) the plurality of metal pipes, any publicly known method such as a bombardment method or an inner tube expanding method can be adopted. In another aspect of the present invention,
The surface of the metal pipe may be resin-lined. For example, a single pipe made of copper may be used as the metal pipe, and the surface thereof may be lined with a fluororesin (for example, "Teflon" manufactured by DuPont). Next, in the present invention, the electric power used is an AC power source of a low commercial frequency. This is because it is practically the easiest to use and economical. Next, a more preferable aspect of the present invention will be described. Figure 4 shows
Input 100V-440V, 50 / 60Hz, heating coil (pipe) 1-
It is a specific example of the combination of the number of metal pipes and the input power source when the number is six. FIG. 4 (A) is an example of single-phase metal pipe connection, FIG. 4 (B) is an example of single-phase metal pipe two, and FIGS. 4 (C) to (E) are three-phase connection lines. Here is an example. Other connections can be freely selected. Next, in the present invention, the preferable diameter of the metal pipe is
It is about 70 to 200 mm. If it is too thin, the magnetic flux will go out and the loss will be large, which is not preferable. A preferable example of the power capacity is about 1 to 50 KW, but the power capacity is not limited to this. Next, the length of the metal pipe is about 10 cm to 1 m, but is not limited thereto. Next, a specific example applied to a heater having a large temperature distribution is shown in FIG. In FIG. 5 (A), the winding density of the coil is changed, and the central portion is coarsely wound and both end portions are densely wound. By doing so, it is effective for a device that radiates a large amount of heat and a heater that is supplied with a body to be heated from the surroundings and whose ambient temperature easily lowers. On the contrary, in the heater in which the temperature of the central portion is likely to decrease, the central coil can be wound densely. FIG. 5B shows a means for improving the uneven temperature distribution by changing the type of the metal pipe in the length direction.
To heat more around the heater, use copper at both ends and brass in the middle. FIG. 6 is a diagram showing another embodiment of the present invention. Sixth
FIGS. A and B are examples of a single phase, and FIGS. 6C and D are examples of using three phases. The heater 6 is as shown in FIG. Reference numeral 7 is a heating zone, 8 is an inlet for a fluid (for example, water), 9 is an outlet thereof, and 10 is a pump. Although the heater 6 is vertical in FIG. 6, it may be horizontal. Fig. 7 shows the lower sensor 1 on the fluid inlet side of the jacket.
1, an example in which an upper sensor 12 is provided on the outlet side. The temperature signal of each of these and the flow rate detection signal of the introduced fluid are
As shown in FIG. 9 and FIG. 9, the power is supplied to the power controller, and the power supplied is controlled by the product of the temperature difference between the inlet and the outlet and the flow rate of the fluid.
That is, how much Kcal is insufficient with respect to the set temperature is calculated, and the insufficient power is controlled by the voltage. In the control system as described above, a highly accurate temperature fluid can be obtained by instantaneously obtaining Kcal = Kw in the arithmetic circuit and controlling the voltage on the primary side. Here, the flow rate detection signal is, for example, a flow rate detection signal such as the number of revolutions of the pump when a pump is used, or the flow rate detection signal when a flow meter is used. In the present invention, since Kw and Kcal are in a linear relationship, control is extremely easy. The voltage flowing through the metal pipe of the heater of the present invention is from 1V to
Since it is about 0.3V, it is much lower than the voltage of the dry cell (1.5V), which is safe for the human body. It can be used without problems even if the humidity is high. Further, as the induction coil, a copper wire, an aluminum wire, or the like can be used, but there is an advantage that durability is improved if vacuum filling is performed using a resin mold.
Also, since the heat transfer area is wide, the heating part can be 120-130 ℃,
It is also possible to prevent calcium in the water and other salts and scales from adhering. The heating device of the present invention is used as a heating device for fats and oils for heating food (fryer), a heating device for water for heating food (steam generator), for example, a dishwasher requiring hot water of about 80 ° C.,
Cookers below 100 ° C (especially cooked dishes for long hours), heaters for cleaning organic solvents, bath heaters (especially for additional cooking), heaters for gas or heavy oil, heaters for boilers (especially It can be used as a general-purpose heater such as a local boiler). The application is not limited to the above because it is safe and has high thermal efficiency.

【Example】

A more specific description will be given below with reference to examples. Example 1 A heater having a cross section as shown in FIG. 1 (B) was manufactured. An iron core was made by laminating a large number of silicon steel plates, an induction coil was made of copper wire, and a metal pipe was made by integrating a copper pipe inside and a stainless pipe outside. And between the induction coil and the metal pipe, heat-resistant epoxy resin is molded by vacuum filling,
I lost space. When using this heater to wash ICs, etc. using 1,1,1-trichloroethane solvent, conventional electric resistance heaters start at 20 kW and steady-state treatment starts at 10 kW.
What required 12 kW, the heater of the present invention could be operated at 10 kW at the start and 4 kW at the steady process. In addition, since the heater of the present invention has a lower temperature than that of the conventional method, scales are not easily attached, cleaning gas and dust falling from the top hardly adhere to the surface of the pipe, and the life of the heater can be greatly extended. Example 2 The first embodiment is constructed as shown in FIGS. 6 (C), (D) and FIG.
The heater of Fig. (A) was placed inside. Three copper pipes 3 each having a diameter of 9 mm and a length of 26 mm were arranged in the tank. Then, between the induction coil and the metal pipe, a heat-resistant epoxy resin was vacuum-molded to eliminate a space. Supply power, approximately per 1 cm ² 4.5 W, i.e. 4.5 W / cm
² Then, while flowing 15 liters of water per minute and applying three-phase AC power of 200V, 25A, 60Hz to the coil,
Hot water at 0 ° C ± 1 ° C could be continuously discharged.
In the above, about 10000A, 0.5V of electric power was flowing through the copper pipe. Example 3 As shown in FIG. 1 (A), FIG. 8 and FIG.
I made a heating device with a sensor and a control system. That is, three copper pipes having a diameter of 90 mm and a length of 260 mm were arranged in the tank. Then, between the induction coil and the metal pipe, a heat-resistant epoxy resin was vacuum-molded to eliminate a space. Power supply was 1 cm ² per about 3.0 W, that is, 3.0 W / cm ^2. And while flowing 20 liters of water every minute, in the coil
Three-phase AC power of 200V, 20A, 60Hz was applied, and the temperature of the outflow water was set to 65 ± 1 ℃. As a result, even if the temperature of the introduced water fluctuates or the amount of water or the water temperature of the fixed quantity pipe fluctuates, hot water at the set temperature was obtained stably for a long period of time. Furthermore, cleaning inside the heating tank was easy. In the above, about 8000 A, 0.5 V of electricity was flowing through the copper pipe.

【The invention's effect】

The present invention utilizes an electromagnetic induction heating method that applies a low voltage-high current short-circuit transformer, and eliminates a gap between an induction coil and a metal pipe, thereby providing a temperature difference between a heating unit and a heated object. Can be made small, the thermal efficiency is good, the reliability and durability are high, and stable heating can be performed for a long period of time. In addition, it is possible to exert an excellent synergistic effect that the heating area can be increased and the supplied power can be increased.

[Brief description of drawings]

1 (A) and 1 (B) are sectional views showing an embodiment of the present invention. 2 and 3 are diagrams for explaining the principle of the present invention. FIG. 4 is a connection diagram of an example of the present invention.
FIG. 5 is a diagram showing an embodiment of the present invention. Fig. 6 ~
FIG. 9 is a diagram showing another embodiment of the present invention. 1: Iron core, 2: Induction coil 3, 4: Metal pipe, 5: Resin mold

Claims (6)

[Claims] 1. A low frequency electromagnetic induction heater in which an induction coil is wound around an iron core and a metal pipe is provided around the induction coil,
A resin mold for improving thermal conductivity is filled between the induction coil and the metal pipe around the induction coil, and when viewed from the cross-sectional direction of the metal pipe, the metal pipe is exposed from the surface of the induction coil. A low frequency electromagnetic induction heater characterized in that there is substantially no air gap up to the surface. 2. The low frequency electromagnetic induction heater according to claim 1, wherein the low frequency power source is a commercial frequency power source. 3. The low frequency electromagnetic induction heater according to claim 1, wherein the metal pipe is a pipe made of one layer of metal. 4. The low frequency electromagnetic induction heater according to claim 1, wherein the metal pipe is a pipe in which at least two layers of metal pipes are integrated. 5. The low frequency electromagnetic induction heater according to claim 1, wherein the resin mold is made of a heat resistant resin. 6. The low frequency electromagnetic induction heater according to claim 1, wherein the supplied power is 3 W or more per 1 cm ² of surface area of the metal pipe.