JPH02297889A - Low frequency electromagnetic induction heating device - Google Patents

Abstract

PURPOSE:To lessen the temp. difference between a heating part and an object to be heated by interposing resin molding between an induction coil and a metal pipe around it without voids substantially. CONSTITUTION:Resin molding is provided between an induction coil 2 and a metal pipe 3 around it with no voids substantially. The temp. inside the induction coil will rise up to 500 deg.C approximately unless such resin molding is provided, but with the resin molding, on the other hand, temp. rise will remain no higher than approx. 130 deg.C. This lessens the temp. difference between a heating part and an object to be heated, that should accomplish heating with good thermal efficiency, reliability, durability, and long-term stability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a low frequency electromagnetic induction heater. More specifically, the present invention relates to a low-frequency electromagnetic induction heater in which the temperature difference between the heater and the heated object is extremely low.

[Prior Art] In power plants, factories, etc., petroleum, coal, natural gas, or the like is generally used as a heat source for steam or hot water, and any of them is combusted.

On the other hand, some small and small-capacity units use electric resistance heaters as the heat source due to their simplicity, and small boilers and the like use oil or natural gas.

As yet another heating method, a low-frequency electromagnetic induction heater is known (see Utility Model Application Publication No. 56-86789, Japanese Patent Publication No. 58-39525, etc.).

[Problem to be solved by the invention] However, when oil, coal, natural gas, etc. are burned and used in boilers, etc., the temperature difference between the heated part and the water of the heated object is too large, so that no scale is attached. However, there is a problem that the heat transfer coefficient decreases and eventually the tube cracks. For this reason, the water supplied to the boiler must be treated in advance to prevent scale by degassing (deoxidizing) it using chemical agents or keeping it alkaline. Also, systems that burn oil, coal, natural gas, etc. to create steam and circulate it throughout the building to use it as a heating source are widely used in hotels.
It is not necessarily an efficient system as there is a lot of energy loss.

In addition, when an electric resistance heater is placed in water, it is heated to a temperature much higher than the boiling point of water (100°C) near the heat source, so using a heater that does not have sufficient interfacial heat transfer surface area may cause various problems. occurs. In other words, there were the following issues.

■ If the power is not lower than 2W per lal, the heat transfer to the water will decrease and the heater element inside will burn out.

■ Since the voltage applied to the heater is 200v to 400v, sufficient insulation must be provided.

This electrical insulator acts as a temperature insulator, inhibiting heat transfer to the water.

When the heat transfer of water deteriorates, the surface temperature of the heater increases,
When water molecules touch the surface of the heater, they cause a steam explosion, a phenomenon called ``swelling''. Such a "swelling and bending" phenomenon is not only dangerous, but also poses a fundamental problem in that thermal efficiency is extremely reduced.

Moreover, electric resistance heaters, like gas combustion,
Because the temperature difference between the heating source and the water is so large, inorganic and organic components contained in the water are adsorbed and deposited on the surface of the heater, which acts as an insulator and reduces heat transfer. Water boils poorly. At the same time, the heat dissipation of the heater also deteriorates, leading to an accident in which the heater eventually breaks.

In order to avoid this accident, water heaters have a large surface area and are filled with water tanks, which has traditionally been a problem in terms of reliability and the complexity of replacing the heater. Another problem was that it took a lot of effort to clean due to the adhesion of limescale and the like.

Another problem that could not be fundamentally improved was that a large Bach tank was required to accurately control the temperature of the hot water, and it was not possible to downsize it.

Furthermore, Utility Model Publication No. 56-86789, Special Publication No. 58-3
The low frequency electromagnetic induction heater proposed in Publication No. 9525 has not yet been properly designed, has a high temperature difference between the heating source and the heated object, and cannot be said to have good thermal efficiency.

In order to solve the problems of the prior art described above, the present invention utilizes an electric induction heating method that applies a low voltage-high current short circuit transformer, and eliminates the gap between the induction coil and the metal pipe. It is an object of the present invention to provide a device that reduces the temperature difference between a heating part and a heated object, has good reliability and durability, and can perform stable heating over a long period of time.

[Means for Solving the Problems] In order to achieve the above object, the present invention has the following configuration.

(1) In a low frequency electromagnetic induction heater in which an induction coil is wound around an iron core and a metal pipe is provided around it, a resin mold is applied between the induction coil and the metal pipe around it, and the metal A low-frequency electromagnetic induction heater characterized in that there is no substantial gap between the surface of the induction coil and the surface of the metal pipe when viewed from the cross-sectional direction of the pipe.

(2) The low frequency electromagnetic induction heater according to item 1 above, wherein the low frequency is a commercial frequency.

(3) The low frequency electromagnetic induction heater according to item 1 above, wherein the metal pipe is a pipe formed by integrating at least two layers of metal pipes.

(4) The low frequency electromagnetic induction heater according to item 1 above, wherein the resin mold is made of a heat-resistant resin.

(5) The low frequency electromagnetic induction heater according to item 1 above, wherein the supplied power is 3 W or more per surface area 1aIr of the metal pipe.

[Function] According to the configuration of the present invention described above, heating is achieved by utilizing an electromagnetic induction heating method that applies a low-voltage-high-current short-circuit transformer and eliminating the gap between the induction coil and the metal pipe. It is possible to reduce the temperature difference between the heating element and the heated object, thereby providing a device that has good thermal efficiency, reliability, and durability, and can perform stable heating over a long period of time. Furthermore, the heating area can be increased and a large amount of power can be supplied.

[Example 1] An example of the present invention will be described below with reference to the drawings.

FIGS. 1A and 1B are cross-sectional views showing one embodiment of the present invention. Figure 1 (A) shows an example where the pipe is one layer, Figure 1 (B)
) is an example of a two-layer pipe. In Fig. 1 (A) and (B), in a low frequency electromagnetic induction heater 6 in which an induction coil 2 is wound around an iron core 1 and a metal pipe 3 or a metal pipe 4 is provided around it, the induction coil 2 and the A resin mold 5 is provided between the surrounding metal pipes 3, and there is a space 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. This is a low frequency electromagnetic induction heater 6 in which there are no substantial voids.

The first characteristic feature of the present invention is that a resin mold 5 is provided between the induction coil 2 and the metal pipe 3 surrounding it. In this way, the heating efficiency is significantly improved. For example, when boiling water, the inside of the induction coil without the resin mold is approximately 5.
However, if resin molding is used, the temperature can be kept from increasing to about 130°C. Therefore, this has an important meaning of reducing the temperature difference between the heating source and the heated object.

Next, the second characteristic requirement of the present invention is that the induction coil 2
There should be no substantial gap between the surface of the metal pipe 4 and the surface of the metal pipe 4. For example, even when two types of heating pipes are used, no gap is provided between pipes 3 and 4.

This improves heat conductivity and increases thermal efficiency.

In the above, any resin can be used as long as it is suitable for molds.

Examples include epoxy resins, acrylic resins, vinyl resins, phenol resins, silicone resins, polyester resins, and other heat-resistant resins. Among these, thermosetting resins having a heat resistance of 100° C. or higher are preferred. Further, as the resin mold, any known means such as vacuum casting, compression casting, and pouring casting can be employed.

Furthermore, any resin can be used as the molding resin as long as it has heat conductivity, insulation, and heat resistance. As one method of use, for example, fine aluminum particles or fine silica particles can be added to the resin and used in a compound.

In addition, in FIGS. 1(A) and 1(B), it is particularly preferable that molded resin also exists inside the induction coil 2. This is because the presence of resin in the induction coil 2 effectively removes the heat generated within the coil.

In the above, the heater 6 consists of an iron core, a coil, and a pipe.
It can be used either vertically or horizontally.

Next, the heat generation principle of the present invention will be explained using FIG. 2. Second
Figure A is a diagram showing the principle of a transformer. In other words, 100V is applied to the primary side of the coil wound 100 times.

When a current of 10A (50H! or 60H) is passed through the secondary side of the coil wound 100 times, theoretically, 10
0V, IOA alternating current (50HI or 60H current flows in the opposite direction as an additional current.

Next, as shown in Figure 2B, when the secondary coil is wound once and an alternating current is passed through the primary side in the same way, the secondary side receives IV, 1
An induced current of 00OA flows in the opposite direction. In other words, a low voltage, large current short-circuit transformer can be achieved.

The present invention places an induction coil on the primary side and a metal pipe on the secondary side, and applies the principle of the above-described low voltage, large current short circuit transformer. The metal pipe on the secondary side of the present invention may be made of any metal as long as it has conductivity. For example, it is made of copper or steel. As shown in FIG. 2B, the current flowing through a metal pipe (for example, a copper pipe) is large, so it is extremely effective in heating it. That is, when a large alternating current flows, Joule heat is generated due to short circuit current, and this is considered to be effective in generating heat. In this sense, 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 extracted from the electric power. In addition, although an extremely low voltage flows through the copper pipe on the secondary side, this voltage is low enough to cause an electric shock even if a human body comes into contact with it, so it is extremely safe. In addition, according to the principles of the present invention, the heating area is necessarily large. This is because the metal pipe is placed outside the coil. Furthermore, power consumption per unit area can be increased. Therefore, in this heater, it is possible to operate satisfactorily with 3 W or more per 1 eaf of surface area of the metal pipe, or 4 W or more per 1 a1. Since the heating area is large, the temperature difference ΔT between the heating section and the heated object can be made small.

In other words, a synergistic effect can be achieved in that the heating area can be increased and a large amount of power can be supplied.

FIG. 3 shows a model of the heating section 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 it. A commercial frequency current is passed through the induction coil 2, and the metal pipe 3 is heated. Therefore, if an object to be heated, such as water, is present outside the pipe, heat will be taken away from the metal pipe and the metal pipe will be heated.

In the explanation of FIG. 1, the metal pipes 3 and 4 are two pipes bonded together and integrated, but the metal pipes may also be made of one type of single piece (for example, a single piece of stainless steel pipe). or a single copper pipe), or two or more pipes may be used integrally so that there are no voids.

In this example, the inner pipe 3 may be made of copper to improve heat transfer, and the outer pipe 4 may be made of stainless steel to improve durability and corrosion resistance. In other words, it can be used properly depending on the purpose. In addition, in order to integrate these multiple metal pipes (cladding),
Any known method such as the explosion bonding method or the inner tube expansion method may be used. In another embodiment of the present invention, the surface of the metal pipe may be lined with resin. For example, a single copper pipe may be used as the metal pipe, and its surface may be lined with a fluororesin (for example, "Teflon" manufactured by DuPont).

Next, in the present invention, the power used is a low frequency commercial frequency AC power source. This is because it is the most practical and economical.

Next, more preferred embodiments of the present invention will be explained. Figure 4 shows
This is a specific example of the number of metal pipes, the input power source, and the combination when the input is 100V to 440V and 1 to 6 50/60H21 heating coils (pipes). Figure 4 (A) is a single-phase wiring example with one metal pipe, Figure 4 (B) is a single-phase example with two metal pipes, and Figures (C) to (E) are three-phase wiring examples. This is an example. Other connections can also be selected freely.

Next, in the present invention, the preferred diameter of the metal pipe is about 70 to 200 mm. If it is too thin, the magnetic flux will go out and the loss will increase, which is undesirable. Further, 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 approximately 10 cm to 1 m, but is not limited to this.

Next, a specific example of application to a heater with a large temperature distribution is shown in FIG. In FIG. 5(A), the winding density of the coil is changed, so that the center part is wound loosely and both ends are wound densely. This is effective for heaters that dissipate a large amount of heat, or for heaters that are supplied with heated objects from the surroundings and whose surrounding temperature tends to drop. On the other hand, in a heater where the temperature tends to drop in the center, the coil in the center can be tightly wound. Figure 5 (B) shows that by changing the type of metal pipe in the length direction, This is a means for improving the temperature distribution unevenness mentioned above.

To heat more of the area around the heater, use copper on both ends and brass in the center.

FIG. 6 is a diagram showing another embodiment of the present invention. 6th
Figure AXB is a single-phase example, and Figure 6 CSD is a three-phase example. The heater 6 is as shown in FIG. 7 is a heating area, 8 is an inlet of a fluid (for example, water), 9 is an outlet thereof, 10
is a pump. In Fig. 6, the heater 6 is vertical type, but
It may be horizontal.

Figure 7 shows the lower sensor 1 on the fluid inlet side of the jacket.
1. This is an example in which an upper sensor 12 is provided on the exit side. Each of these temperature signals and the flow rate detection signal of the introduced fluid are
As shown in FIGS. 9 and 9, it is led to a power controller, and the supplied power is controlled by the product of the temperature difference between the inlet and outlet and the fluid flow rate.

That is, it calculates how much Kcal is in short supply with respect to the set temperature, and the power for the shortfall is controlled by voltage.

In the control system as described above, the arithmetic circuit calculates Kca1=K
By instantly determining w and controlling the voltage on the primary side,
Fluid with highly accurate temperature can be obtained. Here, the flow rate detection signal is, for example, a flow rate detection signal such as the number of rotations of a pump when a pump is used, and this flow rate detection signal when a flowmeter is used. In the present invention, Kw and Kca
Since l is in a linear relationship, control is extremely easy.

Since the voltage flowing through the metal pipe of the heater of the present invention is about 1V to 0.3V, the voltage of the dry battery (1.5V)
It is much lower than that and is safe for humans. It can also be used without problems even in high humidity. Further, the induction coil can be made of copper wire, aluminum wire, etc., but if it is vacuum filled using a resin mold, there is also the advantage that the durability will be improved. In addition, since the heat transfer area is wide, the heating section is 120~
A temperature of 130°C is sufficient, and it also prevents calcium, other salts, and scales from adhering to the water.

Applications of the heater of the present invention include an oil heater for heating food (fryer), a water heater for heating food (steam generator), a dishwasher that requires hot water of about 80°C, for example,
100℃ or less (especially long-time cooking devices such as boilers), heaters for cleaning organic solvents, bath heaters (and (
It can be used as a general-purpose heater, such as a heater for gas or heavy oil (for additional cooking), a heater for boilers (especially local boilers), etc. Since it is safe and has good thermal efficiency, its uses are not limited to those mentioned above.

[Example code] A more specific explanation will be given below with reference to Examples.

Example 1 A heater having a cross section as shown in FIG. 1(B) was manufactured. The iron core was made of a large number of silicon steel plates laminated together, the induction coil was made of copper wire, and the metal pipe was a combination of a copper pipe on the inside and a stainless steel pipe on the outside. Heat-resistant epoxy resin was then vacuum-filled and molded between the induction coil and the metal pipe, eliminating any space. When using this heater to clean ICs, etc. using 1.1.11-lichloroethane solvent, conventional electric resistance heaters required 20KW to start and 10 to 12KW during steady processing; The heater of the invention could be operated at 10 KW at the start and 4 KW during steady processing. Moreover, since the heater of the present invention has a lower temperature than the conventional heater, it also causes scaling, and the cleaning gas and dirt falling from above adheres to the surface of the pipe (<, and the life of the heater is also significantly shortened. I was able to extend it.

Example 2 The structure was as shown in FIGS. 6(C) and 7, and
The heater shown in Figure (A) was placed inside. Three copper pipes 3 having a diameter of 90 mm and a length of 260 mm were arranged in the tank. Heat-resistant epoxy resin was then vacuum-filled and molded between the induction coil and the metal pipe, eliminating any space.

The supplied power is approximately 4.5W per Icm2, or 4.5W per Icm2.
It was set to 5W/cm2. Then, while flowing 15 liters of water per minute, the coil was connected to 200V and 25A.

When 60Hz 3-phase AC power was applied, the temperature was 80℃±1
It was possible to continuously flow out hot water at ℃.

In addition, in the above, the copper pipe is about 10,000A.

A power of 0.5v was flowing.

Example 3 As shown in FIG. 1(A), FIG. 8, and FIG. 9, Example 2
In the same way, we created a heating device equipped with sensors and a control system.

That is, the thickness of the copper pipe 3 is 9Qmm in diameter.

“Three 260mm long coils were placed in the tank. Heat-resistant epoxy resin was vacuum-filled and molded between the induction coil and the metal pipe to eliminate any space.

The supplied power is approximately 3.5 mm per ICm2. OW, i.e. 3
, QW/cm2. and 20 per minute
While running a little water, connect the coil to 200V, 2OA,
60H! 3-phase AC power is applied, and the temperature of the effluent water is 65%.
The temperature was set at ±1°C. As a result, hot water at the set temperature could be stably obtained over a long period of time even if the temperature of the introduced water fluctuated or the water amount or temperature of the metering pump fluctuated. Furthermore, cleaning inside the heating tank was also easy.

In addition, in the above, the copper pipe is about 8000A.

A power of 0.5v was flowing.

[Effects of the Invention] The present invention uses an electromagnetic induction heating method that applies a low-voltage-high-current short-circuit transformer, and eliminates the gap between the induction coil and the metal pipe. The device can reduce the temperature difference with the body, have good thermal efficiency, be highly reliable and durable, and can provide stable heating over a long period of time. Moreover, it is possible to exhibit an excellent synergistic effect in that the heating area can be increased and the power supplied can be increased.

[Brief explanation of the drawing]

FIG. 1(A) and FIG. 1(B) are cross-sectional views showing one embodiment of the present invention. FIGS. 2 and 3 are diagrams explaining the present invention in detail. FIG. 4 is a wiring diagram of an example of the present invention. FIG. 5 is a diagram showing one embodiment of the present invention. 6 to 9 are diagrams showing other embodiments of the present invention. 1: Iron core 2: Induction coil 3.4: Metal pipe 5: Resin mold Figure 1 (A)
40 Metal pipe 5; Resin mold Fig. 1 (B) Fig. 3 Transformer primary side Secondary side 100 times 100 times Fig. 2 (A) Principle of the present invention Induction coil Steel pipe Fig. 2 (B) ( A) (B)
CD) (E)
(C) Fig. 4 (A) (B) Fig. 5 (B) Fig. 6 12 Upper sensor

Claims (6)

[Claims] (1) In a low frequency electromagnetic induction heater in which an induction coil is wound around an iron core and a metal pipe is provided around it, a resin mold is applied between the induction coil and the metal pipe around it, and the metal A low-frequency electromagnetic induction heater characterized in that there is no substantial gap between the surface of the induction coil and the surface of the metal pipe when viewed from the cross-sectional direction of the pipe. (2) Claim 1, wherein the low frequency power source is a commercial frequency power source.
Low frequency electromagnetic induction heater as described. (3) The low frequency electromagnetic induction heater according to claim 1, wherein the metal pipe is a pipe made of a single layer of metal. (4) The low frequency electromagnetic induction heater according to claim 1, wherein the metal pipe is a pipe formed by integrating at least two layers of metal pipes. (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 cm^2 of the surface area of the metal pipe.