WO2007091749A1

WO2007091749A1 - Induction heating element for electric hot air heater and electric heater using the same

Info

Publication number: WO2007091749A1
Application number: PCT/KR2006/001656
Authority: WO
Inventors: Sung-Il Kim
Original assignee: Sung-Il Kim
Priority date: 2006-02-10
Filing date: 2006-05-02
Publication date: 2007-08-16
Also published as: KR100762734B1; KR20070081242A

Abstract

The present invention pertains to an induction heating element for electric hot air heater applicable for indoor environments such as residential areas, offices, industrial sites, vehicles or agricultural plant houses, etc. In the present invention, instead of using conventional heating elements such as Nichrome wires, ceramic heating elements, carbon heating elements and the like, an novel induction heating element and an electric heater are disclosed, wherein induction heating is mostly used as a heating method for typical industrial heaters, electric rice cookers or electric cooker. It is because the induction heating element adopts the novel heating method which is forced to move cold air into the conductor heated by the induction heating and controls the indoor temperature by providing the heated air. For the induction heating element, a conductor with high thermal conductivity can be used as a heating plate unlike the conventional Nichrome wires, so that better heat conversion efficiency can be achieved. Therefore, it is possible to reduce power consumption, and easy to increase the contact area between air and the heating element, resulting in better heat supply capability and a more compact electric heater than conventional electric hot air heater.

Description

INDUCTION HEATING ELEMENT FOR ELECTRIC HOT AIR HEATER AND ELECTRIC HEATER USING THE SAME

Technical Field

[1] The invention relates to an induction heating element for electric hot air heaters. It heats air by means of the induction heating effect in which eddy currents is generated on the surface of a conductor, when a high-frequency magnetic field generated by means of an induction coil is applied to adjacent conductors, and the surface of the conductors is thereby heated.

[2]

Background Art

[3] With people's higher standard of living, there has been a greater need to keep a pleasant and clean indoor environment in winter. Therefore, people are increasingly interested in the electric hot air heaters which are even more pleasant than conventional heaters that use petroleum or gas as fuel, so that they must consume oxygen and generate the gases emitted from combustion processes.

[4] Conventional electric hot air heaters control an indoor temperature in a manner to heat air, using Joule heating generated by applying current directly to the resistance of a heating element using Nichrome wires, a ceramic heating element using resistance of thin metal films on the ceramic surface or a carbon heating element using carbon resistance.

[5] However, the conventional ordinary electric heaters has structurally a low thermal conductivity and a small contact area between air and a heating element, disadvan- tageously resulting in having a very low heat supply capability and low energy efficiency. Therefore, the heaters consume much electric power and are thus used mainly for the cases other than domestic use.

[6] However, there is an increasing need for a pleasant room environment with people's improved standard of living. To meet the need, power-saving electric hot air heaters using an improved ceramic heating element or heat pipe element have been supplied for domestic use. However, users have still to pay more power bills than for gas heaters or fan-type heaters.

[7] There are advantages of electric hot air heaters only, however, that they can be easily maintained as a wall hanging type, in addition to less risk of accidents, quick heating, and no consumption of oxygen in heating, so that it is possible to keep a pleasant room with fresh air.

[8] As for the electric heater using the induction heating element by the present invention, it definitely is different from the conventional electric heaters (Korea patent publication No. 1999 - 0018536 and Korea patent registration No. 20 - 0325269, etc.), and also from the electric rice cookers (Korea patent publication No. 1998 - 063772, etc.), the electric cookers (Korea patent publication No. 20 - 0124979, etc.), and the industrial heater (the Korea patent registration No. 10 0329345, etc.) etc., because it adopts the novel heating method which controls the indoor temperature by moving cold air into the conductor heated by the induction heating element.

[9]

Disclosure of Invention Technical Problem

[10] In order to obviate the aforementioned disadvantages of the conventional electric hot air heaters and have continuously the aforementioned advantages of them, the invention provides a novel power-saving induction heating element to heat air, which is new heating method different from that for conventional electric heaters.

[H]

Technical Solution

[12] In order to achieve the objects of the invention as described above, the invention provides an induction heating element for electric hot air heaters, comprising a hollow conductive pipe, an induction coil wound in a solenoid shape according to the outer circumference of the pipe, and the high-frequency power generator for providing the high-frequency current connected to the induction coil, is characterized in that air is forced to pass through the conductive pipe to heat the air.

[13] In the conductive pipe, a plurality of (at least one) internal conductive pipes of each different diameter may be overlapped one another, centering on a given axis in order to increase the contact area between air and the induction heating element.

[14] An external pipe between the conductive pipe and the induction coil may be further provided, the external pipe being a non-conductor.

[15] The conductive pipe may be a plurality of conductive pipes facing and gathering one another side by side.

[16] Outside the induction coil, an external pipe may be further provided, so that air may be sent into the conductive pipe as well as the gap between the external pipe and the conductive pipe to heat the air.

[17] An external pipe may be further provided outside the induction coil, wherein the conductive pipe is shaped a solid core and heats cold air by sending the air between the external pipe and the conductive pipe.

[18] The induction heating element for electric hot air heaters according to the invention is characterized in that an inverted U-shaped bar made of a magnetic material of a high magnetic permeability for flux induction is connected to both ends of the conductive pipe, so that the bar encompasses the induction coil.

[19] A blower may be further provided to send air towards the inside of the entrance of the conductive pipe, and the induction heating element may be a bundle comprising at least one or more induction heating elements for electric hot air heaters.

[20] A core with a wing may be further provided in order to widen the contact area between air and an innermost conductive pipe.

[21] A wing may be formed on the external or inner surfaces of the conductive pipe or the inner conductive pipes in order to widen the contact area between air and the surfaces.

[22] The induction heating element for electric hot air heaters according to the invention, comprising two conductive plates facing each other, an induction coil placed between the two conductive plates and disposed on a plane, and a high-frequency power generator for providing high-frequency current connected to the induction coil, is characterized in that air is forced to pass through the space between the two conductive plates to heat the air.

[23] The induction heating element for electric hot air heaters according to the invention, comprising two conductive plates facing each other, an induction coil placed outside the two conductive plates and disposed on a plane, and a high-frequency power generator for providing high-frequency current connected to the induction coil, is characterized in that air is forced to pass through the space between the two conductive plates for heating the air.

[24] The induction heating element for electric hot air heaters according to the invention further comprises at least one or more conductive external conductive plates regularly spaced outside the two conductive plates, respectively, and air is forced to be sent the gap between the external conductive plates to heat the air.

[25] The induction heating element for electric hot air heaters according to the invention is characterized in that the two lateral ends of the external conductive plates and the t wo conductive plates are closed by additional plates facing each other, respectively, to make them shaped a rectangular hollow pipe, so that air passes through the space only between the two conductive plates and the external conductive plates and the air can't leak out to the sides. Advantageous Effects

[26] In the induction heating element by the present invention, a conductor with a high thermal conductivity itself is used to act as a heating plate, differently from a conventional heating element for electric hot air heaters. Therefore, the heat conversion efficiency of the induction heating element can be very good. And since there is no need to continue to supply power in order to keep the temperature of the induction heating element almost constant, less electric power is required as compared to conventional electric hot air heaters.

Brief Description of the Drawings [27] The features and advantages of the present invention will be evident like the following detailed description of a preferred embodiment thereof illustrated with reference to the accompanying drawings, wherein: [28] [29] Fig. 1 shows a perspective view illustrating the electric hot air heater using an induction heating element according to the invention; [30] [31] Fig.2 is a perspective view of the induction heating element for electric hot air heaters of a first embodiment according to the invention; [32] [33] Fig.3 is a perspective view of the induction heating element for electric hot air heaters of a second embodiment according to the invention; [34] [35] Fig.4 is a perspective view of the induction heating element for electric hot air heaters of a third embodiment according to the invention; [36] [37] Fig.5 is a perspective view of the induction heating element for electric hot air heaters of a fourth embodiment according to the invention; [38] [39] Fig.6 is a perspective view of the induction heating element for electric hot air heaters of a fifth embodiment according to the invention; [40] [41] Fig.7 is a perspective view of the induction heating element for electric hot air heaters of a sixth embodiment according to the invention; [42] [43] Fig.8 is a perspective view of the induction heating element for electric hot air heaters of a seventh embodiment according to the invention; [44] [45] Fig.9 is a perspective view of the induction heating element for electric hot air heaters of a eighth embodiment according to the invention; and [46] [47] Fig.10 is a perspective view of an induction heating element for electric hot air heaters adding a rotary wing according to the invention. [48]

Best Mode for Carrying Out the Invention

[49] The induction heating element for electric hot air heaters according to the invention is characterized in that the plates to prevent air leaking are made of a magnetic material with a high magnetic permeability to form a magnetic flux path of magnetic field.

[50] The induction heating element for the electric hot air heaters according to the invention may further comprise a blower for blowing air between the two conductive plates as well as between the external conductive plates, and the electric heater also comprises at least one or more induction heating elements to form a bundle.

[51] The conductor plates or pipes heated by induction heating may be made of metal with high thermal conductivity, a magnetic material with a high magnetic permeability, the alloy of the two, or the metal with a high thermal conductivity coated with the magnetic material with a high magnetic permeability in order to enhance heat conversion efficiency of electric power.

[52] The principle that a conductor is heated by means of induction heating is that, when high-frequency current flows through an induction coil, the magnetic field generated by the induction coil reaches a conductor located near the magnetic field, and induction current flows on the surface of the conductor in a skin depth to which the magnetic field reaches, so that Joule heating is generated. More particularly, when a high- frequency magnetic field is applied to the conductor, induction current flows on the surface of the conductor in a direction against the magnetic field, so that the surface of the conductor is heated by means of resistance of the conductor itself.

[53] The induction heating method has been widely used only for the heating method of industrial heaters for partial heating, for example, annealing. Lately, the induction heating, however, is being increasingly widely used for heating method in cooking such as for electric rice cookers and electric cookers. Unlike the cookers, the object of invention, however, controls properly indoor temperature by heating cold air by means of an induction heating element using induction heating for an electric heater. Mode for the Invention

[54] Hereinafter, the invention will be described in detail with reference to accompanying drawings. As shown in Fig. 1, the electric heater 100 according to the invention forces cold air 90 to be sent into an induction heating element bundle 40 by means of a blower 50 to heat the air and then the heated hot air 91 is discharged to the outside through an exit (not shown) provided on the electric heater 100, wherein the cold air comes in through an entrance 92.

[55] In this case, the induction heating element bundle 40 is heated by induction heating generated by the high-frequency current of a high-frequency power generator 30. Also, another blower may be equipped at the exit of air to discharge the heated air.

[56] The induction heating element bundle 40 may consist of at least one or more induction heating elements.

[57] Hereinafter, preferred embodiments of the invention will be described in more detail with reference to the accompanying drawings.

[58]

[59] Embodiment 1

[60] Fig. 2 is a perspective view of an induction heating element of a solenoid shape for electric hot air heaters according to the invention.

[61] As shown in Fig. 2, the induction heating element of a solenoid shape has a structure having a high-frequency power generator 30, an induction coil 20 and a hollow conductor pipe 11 made of metal, magnetic material, the alloy of the two, or the metal coated with the magnetic material in the induction coil 20. The power generator 30 is coupled to the induction coil 20. When high-frequency current generated by the power generator 30 flows to the induction coil 20, induction current is generated on the surface of the conductive pipe 11 positioned inside the induction coil 20 as a reaction to interrupt the high-frequency current flow of the induction coil 20 and the conductive pipe 11 is thereby heated by the induction current.

[62] In order to improve the heat conversion efficiency of the induction heating element from the electric power, the material of the conductive pipe 11 may be a conductor made of a metal with a high thermal conductivity, a magnetic material with a high magnetic permeability, the alloy of the two, or the metal with a high thermal conductivity coated with the magnetic material with a high magnetic permeability.

[63]

[64] As in Fig. 2, the conductive pipe 11 heated by the high-frequency magnetic field is characterized in that it is shaped a hollow pipe. And a indoor temperature is controlled by forcing cold air 90 to be sent into the heated conductive pipe 11 by means of a blower 50 to heat the air.

[65] If the conductive pipe 11 to be heated is made of a conductor with a high thermal conductivity, heat conversion efficiency can be more improved. It is also not needed to continue to supply power to the conductive pipe 11 in order to keep the temperature of the conductive pipe 11 almost constant. Since all the heat is generated in the conductive pipe 11 acting as a heating plate, it is considerably efficient in the power consumption. It is easy to increase the amount of heat supplied by an induction heating element of an electric heater 100, by extending both lengths of the induction coil 20 and the conductive pipe in order to augment the heating area, and it is thus easy to reduce the overall size of the heater.

[66] If the conductive pipe 11 which is a part to be heated in the induction heating element is made of a conductor with a high thermal conductivity, it is possible to significantly lower a heat loss rate, thereby to reduce the amount of power consumption in the heater. For example, it is easily understood that an aluminum pot with a low heat loss can achieve the same cooking effect under the same condition with 25% of the energy required for an iron pot with a high heat loss. In case of an induction heating (IH) electric rice cooker currently available in Korea, cooking time is also reduced under the same conditions, if the inner pot of the cooker is made of brass with a high thermal conductivity instead of stainless steel with a low thermal conductivity.

[67]

[68] Hereinafter, in the accompanying drawings, for the sake of convenience, the size of the induction coils 20 and 21 is exaggerated.

[69]

[70] Embodiment 2

[71] In Fig. 3, the induction heating element has a structure in which a thin cylindrical inner conductive pipe 13 of a small diameter is overlapped inside a thin cylindrical conductive pipe 12 of a large diameter in order to widen the heating area between air and the heated conductive pipe. The embodiment is characterized in that cold air 90 is forced to pass through the conductive pipe 12 as well as the inner conductive pipe 13 to heat the air. In this case, the conductive pipe 12 and the inner conductive pipe 13 are all conductive. The reason that the conductive pipes 12 and 13 must be thin is that heat is generated only on the surface of the conductor which is positioned as deep as the magnetic field generated by means of the induction coil 20 is reached. This is referred to as a skin depth, and the skin depth d of a good conductor is determined according to the following equation:

[72]

[73] where f is a current frequency, sigma is a conductivity of the conductor, μ is a magnetic permeability of the conductor and πis 3.141592.

[74] Regardless of one conductive pipe 11 and a plurality of conductive pipes overlapped with each different diameters centered on a given axis, heat is generated to the same depth of the popes in both cases, if the pipes are made of the same conductive material and its total thickness is the same in both cases. In the latter case that a plurality of conductive pipes are overlapped, the contact area between air and the heated pipes increases largely, so that the latter case can achieve better heat conversion efficiency. That is, better heat conversion efficiency is achieved in the case that the conductive pipes and inner conductive pipes are made thin to result in several overlapped conductive pipes. Even though one inner conductive pipe 13 is overlapped inside the conductive pipe 12 centered on a given axis in case of Fig. 3, one or more inner conductive pipes may be overlapped inside the conductive pipe.

[75] Also, an external pipe of a non-conductor may be further provided between the conductive pipe and the induction coil.

[76]

[77] Embodiment 3

[78] As shown in Fig. 4, the conductive pipe 14 to be heated is shaped a hollow rectangular pipe and air is forced to pass through the empty space of the conductive pipe 14 to heat the air.

[79]

[80] Embodiment 4

[81] As shown in Fig. 5, there is provided an external pipe 16, for leading air, outside the induction coil 20 and there is provided a conductive pipe 15 to be heated inside the induction coil. Air is forced to pass through the empty space between the heated conductive pipe 15 and the external pipe 16 for heating the air. The conductive pipe 15 may be a hollow pipe or a solid core shape.

[82]

[83] Embodiment 5

[84] As shown in Fig. 6, in case of an induction heating element of a solenoid shape, an inverted U-shaped bar 60 made of magnetic material with a high magnetic permeability is connected to both ends of the conductive pipe 11 in order to surround the induction coil 20 and so form a magnetic flux path. And it thus prevents the leakage of the magnetic flux generated by the induction coil. With this structure, the heating efficiency of the conductive pipe 11 can be more increased.

[85]

[86] Embodiment 6

[87] Fig. 7 is a perspective view illustrating an induction heating element for electric hot air heater in which an induction coil 21 is disposed on a flat plane according to the invention.

[88] Fig. 7 shows a structure that the element has two thin conductive plates 71 and 72 made of a magnetic material with a high magnetic permeability, metal with a high thermal conductivity, the alloy of the two, or the metal with a high thermal conductivity coated with the material with a high magnetic permeability, and an induction coil 21 on a given plane between the two conductive plates, and the power generator 30 connected to the induction coil 21. When high-frequency current generated in the high-frequency power circuit 30 flows into the induction coil 21, the two conductive plates 71 and 72 are heated and air is forced to pass through the space between the two conductive plates to heat the air.

[89]

[90] Embodiment 7

[91] As shown in Fig. 8, the induction heating element has a structure in which it has two thin conductive plates 71 and 73 to be heated and an induction coil 21 outside the two conductive plates 71 and 73 and the high-frequency power generator 30 connected to the induction coil 21. In this case air is forced to pass through the space between the two conductive plates 71 and 73 in order to heat the air.

[92]

[93] Embodiment 8

[94] As shown in Fig. 9, the two conductive plates 71 and 72 may be a thin conductive plate as in the embodiment 2. Therefore, at least one or more external conductive plates 74 may further be provided, regularly positioned outside the conductive plates 71 and 72, and air is forced to pass through the space between the external plates 74 as well as the two conductive plates 71 and 72 to heat the air.

[95]

[96] In case of embodiments 6 and 7, the lateral sides are closed with additional plates facing each other to prevent air from leaking out into both sides of the two conductive plates, and to allow air to pass through the space only between the two plates. Also, the plates may be made of magnetic material for forming the magnetic flux path thus to prevent the leakage of the magnetic flux.

[97] A structure suitable for increasing the contact area between the conductor and air may be further added, wherein the conductor is a part to be heated in all embodiments. For example, in case of Fig. 2, it is possible to put a hollow pipe or a solid core pipe made of metal with a rotary wing inside the conductive pipe 11 to increase the contact area between the heating element and air. Fig. 10 shows the resulting shape of the element with a rotary wing 80, and a rotary wing 80 may be further provided in the innermost pipe as shown in Fig. 10. Also, in all the embodiments, it is possible to add a rotary wing on the internal or external surfaces of the conductors to increase the contact area between air and the heating element.

[98] The conductors to be heated by means of induction heating in all embodiments may be made of metal with a high thermal conductivity, a magnetic material with a high magnetic permeability, the alloy of the two, or the metal with a high thermal conductivity coated with the magnetic material with a high magnetic permeability in order to improve heat conversion efficiency of the heating element.

[99]

[100] The induction heating element bundle 40 in all embodiments may be a bundle comprising a plurality of induction heating elements.

[101]

[102] Hereinabove, preferred embodiments of the invention were described in detail, but it should be understood that the scope of the invention should not be limited to those specific embodiments, and should be construed as defined in accompanying claims. Also, it should be understood that many modifications and variations by those skilled in the art can be made without departing from the scope of the invention. Industrial Applicability

[103] The aforementioned induction heating element can heat air quickly, and it is easy to widen the contact area between air and the induction heating element, so that the heat supply capacity thereof is very good and it is thereby possible to produce a compact electric heater.

Claims

[1] An induction heating element for electric hot air heaters, comprising a hollow conductive pipe, an induction coil wound in a solenoid shape according to the outer circumference of the pipe, and the high-frequency power generator for providing the high-frequency current connected to the induction coil, is characterized in that air is forced to pass through the conductive pipe to heat the air.

[2] The induction heating element as claimed in claim 1, characterized in that one or more inner conductive pipes of a different diameter are overlapped inside the conductive pipe, centered on a given axis, in order to increase a contact area between air and the heating element.

[3] The induction heating element as claimed in claim 2, characterized in that an external pipe is further provided between the conductive pipe and the induction coil, the external pipe being a non-conductor.

[4] The induction heating element as claimed in claim 1, characterized in that the conductive pipe consists of a plurality of conductive pipes facing and gathering each other.

[5] The induction heating element as claimed in claim 1, characterized in that an external pipe is further provided outside the induction coil, and air is sent into the conductive pipe and also between the external pipe and the conductive pipe to heat the air.

[6] The induction heating element as claimed in claim 1, characterized in that an external pipe is further provided outside the conductive pipe and the induction coil, and the conductive pipe is shaped a solid core, air being sent between the conductive pipe and the external pipe to heat the air.

[7] The induction heating element as claimed in any one of claims 1 to 6, characterized in that an inverted-U shaped bar of a magnetic material with a high magnetic permeability for magnetic flux induction is connected to both ends of the conductive pipe, the bar externally encompassing the induction coil.

[8] An electric hot air heater as claimed in any one of claims 1 to 6, characterized in that a blower for sending air into the entrance of the conductive pipe and inner conductive pipes is further provided, and the heater comprises one or more induction heating elements formed as a bundle.

[9] The induction heating element as claimed in any one of claims 1 to 6, characterized in that a winged core is further provided in order to increase the contact area between air and an innermost conductive pipe.

[10] The induction heating element as claimed in any one of claims 1 to 6, characterized in that a wing is formed on the external or inner surfaces of the conductive pipe or the inner conductive pipes in order to increase the contact area between air and the surfaces.

[11] An induction heating element for electric hot air heaters, comprising two conductive plates facing each other, an induction coil placed between the two conductive plates and disposed on a plane, and a high-frequency power generator for providing high-frequency current connected to the induction coil, is characterized in that air is forced to pass through the space between the two conductive plates to heat the air.

[12] An induction heating element for electric hot air heaters, comprising two conductive plates facing each other, an induction coil placed outside the two conductive plates and disposed on a plane, and a high-frequency power generator for providing high-frequency current connected to the induction coil, is characterized in that air is forced to pass through the space between the two conductive plates for heating the air.

[13] The induction heating element as claimed in any one of claim 11 or 12, characterized in that at least one or more external conductive plates regularly spaced are further provided outside the two conductive plates, and air is also forced to pass through the space between the external conductive plates to heat the air.

[14] The induction heating element as claimed in any one of claims 11 to 13, characterized in that lateral sides of the conductive plates and the external conductive plates, respectively, are closed by additional plates facing each other in order to prevent air leaking out into the sides and to allow air to pass through the space only between the conductive plates and between the external plates.

[15] The induction heating element as claimed in claim 14, characterized in that the plates for preventing the leakage of air are made of a material with a high magnetic permeability so that a magnetic flux path of magnetic field is thereby formed.

[16] An electric heater as claimed in any one of claims 11 to 13, characterized in that a blower is further provided to blow air between the two conductive plates as well as between the external conductive plates, and the induction heating element is formed as a bundle by comprising one or more induction heating elements.

[17] The induction heating element for electric hot air heaters as claimed in any one of claims 1 to 6 and claims 11 to 13, characterized in that the conductive plates or pipes to be heated by means of induction heating are made of metal with a high thermal conductivity, a magnetic material with a high magnetic permeability, the alloy of the two, or the metal with a high thermal conductivity coated with the magnetic material with a high magnetic permeability.