JPH06134040A - Infrared radiation electric heater - Google Patents

Abstract

PURPOSE:To provide a simple infrared radiation electric heater using a conventional electric heater excellent in fastness and durability. CONSTITUTION:An electric heater 3 composed of a sheath heater is provided in a metal pipe 4 whose outer surface is coated with a black substance having high absorbing capacity and a reflecting plate 5 made of a metal such as stainless steel or an infrared radiation plate wherein a steel plate is coated with a black substance having high adsorbing capacity is provided behind the metal pipe 4. The heat value of the electric heater, the length, thickness or surface area of the metal pipe and the material applied to the outer surface of the metal pipe are selected so that the temp. of the outer surface of the metal pipe becomes about 150-350 deg.C when power is supplied to the electric heater 3. The heat generated from the electric heater is transmitted to the metal pipe having a surface area wider than that of the electric heater to efficiently convert the quantity of heat to infrared rays to emit the same from the surface of the metal pipe lower than the electric heater in temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a far-infrared radiant electric heater which is used for heating or sauna baths and which radiates far-infrared rays directly to a human body to heat them.

[0002]

2. Description of the Related Art Recently, the heat of combustion such as electric power and gas is converted into light called far infrared rays having a long wavelength of about 4 to 7 microns which is easily absorbed by organic substances such as the human body or water, and the human body is irradiated and heated. The electric far-infrared radiation sauna or gas far-infrared radiation sauna has begun to spread. Far infrared rays having the above wavelength are not easily absorbed by a diatomic gas such as air, and are easily absorbed by an organic substance such as a human body or water. Utilizing these features, the far infrared sauna that emits far infrared rays directly to the human body without raising the temperature of the air has a lower air temperature than the conventional electric convection sauna. Since it efficiently heats the human body by the far-infrared radiation effect, it may spread widely in the future because it sweats quickly, does not have stuffy breath, and it is energy-saving, etc. , Tends to be widely used in heating devices and the like. That is, far infrared rays
Because it has the characteristic that it is difficult to be absorbed by the air and easily absorbed by organic substances such as the human body, the far-infrared rays can be directly absorbed by the irradiated object to warm the irradiated object without raising the temperature of the air. Therefore, it will be an energy-saving heating method, and it may become more widely used in the future as well as for saunas.

[0003]

The wavelength of light is
Determined by the surface temperature of the object that emits light, the temperature that emits the largest amount of light of about 4 microns, in other words, the surface temperature of the object that generates light with a peak wavelength of about 4 microns is about 450 ° C. The surface temperature of an object that emits light with a wavelength of about 7 microns is about 150 ° C. For a sauna, light with a wavelength of about 5-6 microns is easily absorbed by water and organic substances, so the surface temperature of the far-infrared radiator is light with a peak wavelength of about 5-6 microns. It is desirable to set the temperature for radiating the light, that is, about 200 to 300 ° C.

On the other hand, the amount of light emitted from an object having the same temperature, that is, the amount of energy is determined by the emissivity of the surface of the object. Also, at the same temperature, the ratio of emissivity to absorptivity is constant regardless of the substance, and is equal to the emissivity of a black body. Therefore, a substance having a high emissivity, that is, a black substance having a high absorptivity is applied or adhered to the far-infrared radiation surface of the conventional far-infrared radiation electrothermal heater or far-infrared radiation gas heater. The amount of energy emitted from the object is proportional to the product of the fourth power of the absolute temperature of the surface of the object, the emissivity of the surface, and the surface area.

[0005] Therefore, a nichrome wire, a sheathed heater or the like has been widely used as an electric heating device for generating light or heat by using electric power. However, because the conventional electric heating equipment is small and generates more heat, the surface temperature of the electric heating equipment is 8
Most of them are set to over 00 ℃. In this way, it is easy to use an electric heating device whose surface temperature is 800 ° C or higher and lower the surface temperature to 200-300 ° C by lowering the voltage to make a far-infrared radiation electric heater. However, if the surface temperature of the electric heating device is lowered, naturally generated energy also decreases.

That is, as described above, the amount of energy generated is proportional to the fourth power of the absolute temperature of the surface of the object, so if the surface temperature is lowered from 800 ° C to 200 ° C, (800 + 273) ⁴
/ (200 + 273) ⁴ = 26.5, that is, the amount of energy generated is
It will be reduced to 1 / 26.5. Lowering the temperature to 300 ° C. from ^{1000 ℃ (1000 +273) 4 /} (300 + 273) 4 = 24.4, i.e., the amount of generated energy is to be reduced to 1 / 24.4. Even when the temperature is lowered from 800 ℃ to 300 ℃ (800 + 27
3) ⁴ / (300 + 273) ⁴ = 12.3, that is, the amount of energy generated
It will be reduced to 1 / 12.3. In other words, when the conventional electric heating device is used as a far infrared radiant electric heater, 12 to 27 times the number is required to generate the same amount of heat. This has a problem that the price is high and the number of instruments is large or the size is too large.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to use far-infrared rays efficiently by using an electric heating apparatus which has been widely used from the past and which has a simple structure. A far-infrared radiant electric heater that radiates well and absorbs electric energy directly to the object to be irradiated without heating the air as much as possible to efficiently heat it in an energy-saving manner. It is to develop manufacturing technology.

[0008]

In order to achieve the above object, the far infrared radiant electric heater according to the present invention closes one end of a metal tube serving as a far infrared radiant tube and supplies the other end for power supply. It is fixed to a power supply connection box, an electric heater is provided inside the metal pipe in parallel with the central axis of the longitudinal direction and with a predetermined gap from the inner wall of the metal pipe, and a terminal portion of the electric heater is connected to a power source via a switch. The outer surface of the metal tube is provided with a coating layer made of a material having a high absorptivity, and a reflecting plate having a low absorptivity is provided in parallel with the metal tube at a predetermined distance behind the metal tube. At the same time, when power is supplied to the electric heater, the calorific value of the electric heater, the length and thickness or the surface area of the metal pipe, and the outer surface of the metal pipe should be set so that the outer surface temperature of the metal pipe becomes 150 ° C to 350 ° C. It is characterized in that the material of the coating layer is selected.

Instead of the above-mentioned reflection plate provided on the rear part of the metal tube, a far-infrared radiation plate in which a steel plate or the like is coated with a substance having a high absorptivity may be provided. As a metal tube,
It is recommended to use a thin stainless steel circular tube, and the electric heater housed in the metal tube should be provided eccentrically from the center of the metal tube to the side where far infrared rays should be radiated. Recommended.

As described above, the present invention has been used for electric heaters such as sheathed heaters, which are commercially available at a lower cost than before, and gas far-infrared radiation sauna heaters, etc., and is a cylinder made of stainless steel or the like having excellent durability. The present invention provides a far-infrared radiant electric heater which is simple, inexpensive, and excellent in durability by using a thin metal tube having a shape. That is, the far-infrared radiation coating material containing a black substance having high emissivity, that is, absorptivity is applied to the outer surface of a stainless steel thin-walled metal tube that is sufficiently thicker and has a larger surface area than the sheathed heater, and far-infrared rays are radiated from the outer surface of the thin-walled metal tube. Configure to allow.

A combustion gas is circulated in the thin metal pipe,
A gas far-infrared sauna heater that heats the inner surface of a thin metal tube with the combustion gas and radiates far-infrared rays from the outer surface of the metal tube to radiatively heat a human body in a sauna room is already known and has no problem in durability. As is known, the present invention appropriately installs a commercially available sheathed heater inside the thin-walled metal tube instead of the combustion gas, and the sheathed heater is sufficiently thicker than the sheathed heater and has a large surface area. The inner surface of the thin metal tube is heated to a temperature suitable for far infrared radiation of about 150 to 350 ° C, more preferably about 200 to 300 ° C. By radiating
It is possible to inexpensively manufacture a far-infrared radiant electric heater which is simple, robust, and excellent in durability.

[0012]

[Function] Far-infrared rays are light that is easily absorbed by organic substances and water, but difficult for air to absorb. To do. Therefore, when used for heating, etc., the human body can be heated without raising the temperature of the air,
It is widely known that this is a heating method with good thermal efficiency and energy saving. Far-infrared light has a longer wavelength than visible light and near-infrared light and is emitted from a relatively low-temperature object, but the wavelength of light is determined by the surface temperature of the object that emits light, as described above. 5 easily absorbed by organic matter
In order to radiate far infrared rays having a peak wavelength of light of about 6 microns, the surface temperature of the radiator needs to be 200 to 300 ° C.

However, when the surface temperature of an electric heating device such as a sheathed heater is lowered to about 200 to 300 ° C. to directly radiate far infrared rays, the amount of heat generated per unit is greatly reduced, so that a large number of electric heating devices are required. You need to use a fixture, or you need a very large electric heater,
It was difficult to put it into practical use. The present invention, which is configured as described above, can provide a far-infrared radiant electric heater that can efficiently convert the same amount of heat into far-infrared rays and radiate it by simply adding simple equipment to the conventional electric heating equipment. Is.

That is, in the present invention, radiant energy from an electric heater having a small surface area and a high surface temperature is once absorbed by a metal tube having a large surface area and re-radiated as secondary radiation from the outer surface of the metal tube. The radiant energy is converted into long-wave far infrared rays by lowering the surface temperature of the source. In other words, the metal tube has a large surface area even if it absorbs radiation of short wavelength supplied from the inside, so that even if the radiant energy per unit surface area decreases, thermal equilibrium is maintained, and the surface has a very high temperature. Therefore, a large amount of far infrared rays can be efficiently obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. 1 is a partially cutaway plan view of a first embodiment of a far infrared radiation electric heater according to the present invention, FIG. 2 is a side view thereof, FIG. 3 is a partially cutaway plan view of a second embodiment, and FIG. It is a side view.

The first embodiment shown in FIGS. 1 and 2 is the most basic embodiment of the present invention.
It is used as a heat source for a far-infrared sauna for home use for one person, or an electric far-infrared radiant heater of about 1 KW used for a far-infrared spot heating for individuals.

One side plate of the pentagonal power supply connection box 1 made of steel plate
1-2 are configured to be removable by screws 1-3, and the electric power supplied from the outside is connected to the terminals of the sheath heater 3 inside the power supply connection box 1 by the power supply line 2. The sheathed heater 3 projects upward from the inside of the power supply connection box 1, makes a U-turn at the upper end as shown in the figure, enters the power supply connection box 1 again, and both ends are connected to the power supply line 2. The region of the sheathed heater 3 near the end portion has the structure of the sheathed heater 3 so that heat generation is reduced.

The far-infrared radiation tube 4 is formed by closing the upper end of a thin-walled metal tube with a metal plate and welding the lower part with a flange for attaching it to the power supply connection box 1, and absorbing the outer surface of the tube with ceramics or metal. Highly effective black paint is applied. Inside the far-infrared radiation tube 4, the aforementioned sheathed heater 3 is built in parallel to the longitudinal direction (center axis direction) of the inner surface of the far-infrared radiation tube 4 and with a predetermined gap provided between the inner surface and the far-infrared radiation tube 4. ing.

Behind the far-infrared radiation tube 4 (on the side opposite to the side on which the object to be irradiated with far-infrared radiation is located), a reflector 5 is provided in parallel with the longitudinal direction of the far-infrared radiation tube 4 and the power supply connection box 1 Attached to. The reflection plate 5 is made of a material such as a stainless plate or an aluminum plate that has a low absorption capacity and easily reflects far infrared rays. The surface desired by the far infrared radiation tube 4 is polished and radiated from the rear surface of the far infrared radiation tube 4. Light is reflected toward the side where the object to be irradiated with far infrared rays is located.

As the sheathed heater 3 housed in the far-infrared radiation tube 4, a commercially available one in which an insulating material and a nichrome wire are enclosed in a steel tube having a diameter of about 10 mm to 20 mm can be used. Such a sheathed heater is used to heat a human body or an object by raising the surface temperature of the steel pipe to about 700 to 1000 ° C in the atmosphere when energized, or when it is placed in a liquid to heat the liquid. For saunas, it has been widely put to practical use as a sauna stove for air-heated saunas, which is commonly called the Finnish method.

When current is supplied to the sheath heater 3 from the power supply line 2, the sheath heater 3 is heated to about 800 ° C.,
Mainly radiates near infrared rays to heat the inner surface of the far infrared ray emitting tube 4. When the inner surface of the far-infrared radiation tube 4 is heated, the temperature of the outer surface of the far-infrared radiation tube 4 rises, and far-infrared rays start to be radiated from the outer surface coated with a black material having high absorbing ability.

In the first embodiment, the thickness and length of the sheathed heater 3 and the far infrared radiation tube 4 are set so that the surface area of the far infrared radiation tube 4 is about 15 to 20 times the surface area of the sheathed heater 3. Since the far infrared radiation tube 4 is sufficiently heated, the temperature on the outer surface of the tube rises to about 200 to 300 ° C, and the most amount of light with a wavelength of about 5 to 6 microns is emitted from the outer surface of the tube. Far infrared rays included in are emitted.

As shown in FIG. 1, the sheathed heater 3 is provided so as to be eccentric to the far infrared ray emitting tube 4 in the downward direction of FIG. 1, that is, in the far infrared ray emitting direction. This is because the intensity of light is inversely proportional to the square of the distance, so a far-infrared radiation tube
This is because the radiation portion of 4 is heated more strongly and the far infrared radiation amount in the radiation direction is further increased. In addition, the inner wall on the back side of the far-infrared radiation tube 4 that is far from the sheathed heater 3 is heated by not only the near-infrared rays emitted from the sheathed heater 4 but also the convection of hot air. Although the back side of the tube 4 has a temperature slightly lower than that of the front side, it can sufficiently function as a heat transfer surface for far infrared radiation. The above is the first embodiment of the present invention.

Next, a second embodiment having a larger capacity than the first embodiment will be described. FIG. 3 is a plan view of the second embodiment of the present invention, and FIG. 4 is a side view of the second embodiment, and a partially broken surface is shown by hatching. The second embodiment is a device larger than that of the first embodiment, and is used as a heat source for a sauna for business, or an electric far-infrared radiant heater of about 2 KW or more used for commercial spot heating, etc. Structure is the first
Two far-infrared radiation tubes 4 having the same structure as the apparatus of the embodiment are provided.

The one side plate 1-2 of the steel power source connection box 1 is
The power supply line 2 is configured to be removable by screws 1-3, and is connected to the terminals of two sets of sheath heaters 3 inside the power supply connection box 1. Similar to the first embodiment, the two far-infrared radiation tubes 4 and 4 made of thin-walled metal tubes each containing two sets of sheathed heaters are closed with a metal plate at the upper part and a lower part with a power connection box via a flange. 1 and the outer surface is coated with a black paint having high absorption capacity. A reflection plate 5 made of stainless steel or aluminum is fixedly provided on the power supply connection box 1 on the back side of the far-infrared radiation tubes 4 and 4, and the light emitted from the far-infrared radiation tubes 4 and 4 is not radiated. When it is emitted in the direction (on the rear side of the far-infrared radiation tubes 4 and 4 and in the installation direction of the reflection plate 5), the reflection plate 5 reflects the far-infrared rays and emits the far-infrared rays toward the irradiation target.

When electric power is supplied to the sheathed heaters 3 and 3 from the power supply line 2, the sheathed heaters 3 and 3 are supplied as in the first embodiment.
3 is heated to about 800 ° C and mainly emits near infrared rays to heat the inner surfaces of the far infrared ray emitting tubes 4 and 4, and when the far infrared ray emitting tubes 4 and 4 are sufficiently heated, the temperature of the outer surface of the tube is 200 to 300 ° C.
Far infrared rays containing the largest amount of light having a wavelength of about 5 to 6 microns are radiated from the outer surface of the tube coated with a black substance having a high absorption capacity.

The sheathed heaters 3, 3 are, as shown in FIG.
The far-infrared radiation tubes 4 and 4 are provided eccentrically in the far-infrared radiation direction, and are configured to further increase the far-infrared radiation amount in the radiation direction as in the first embodiment.

In each of the first and second embodiments, the reflection plate 5 is used to reflect the far infrared rays emitted from the far infrared ray emission tube 4 to the rear side in the emission direction. As described above, a far infrared radiation plate may be used instead of the reflection plate 5. In this case, the far-infrared radiation plate is the reflection plate 5
On the metal plate of the same shape as the above, apply a black paint having the same high absorption capacity as the paint to be applied to the outer surface of the far-infrared ray emitting tube 4, and, in the same way as the reflecting plate 5, in parallel with this behind the far-infrared ray emitting tube 4. It is provided. When such a far-infrared radiation plate is provided, the far-infrared radiation emitted to the rear side of the far-infrared radiation tube 4 hits the far-infrared radiation plate and is absorbed, and when the temperature of the far-infrared radiation plate rises, the far-infrared radiation plate is emitted. Far infrared rays are also emitted from the far infrared ray emitting direction. At this time, the wavelength of far infrared rays emitted from the far infrared radiation plate is
Since the temperature is lower than the light emitted from the far-infrared radiation tube 4, it has a longer wavelength and the far-infrared radiation plate temperature is 100 to 20.
At about 0 ° C., far infrared rays containing the largest amount of light with a wavelength of about 6 to 8 microns are emitted.

To summarize the above functions, the far-infrared radiation plate converts the light emitted from the back side of the far-infrared radiation tube 4 into light having a longer wavelength and emits it toward the object to be heated. . When the object to be heated better absorbs light having a longer wavelength, the far-infrared radiation plate may exert a more excellent effect than the reflection plate 5. However, when the temperature of the far-infrared radiation plate rises, heat radiation to the back side of the far-infrared radiation plate increases, and depending on the case, heat insulation of the back side of the far-infrared radiation plate must be taken into consideration. When the temperature of the radiation plate rises, air is heated by convection and heat transfer by the far-infrared radiation plate, and there is also a disadvantage that the amount of far-infrared rays generated is reduced accordingly. It cannot be said that the infrared radiation plate is functionally superior, and which one should be adopted should be selected according to the usage conditions such as the shape of the device and the physical condition of the object to be heated, and the purpose of use.

[0030]

As described at the beginning, if a far-infrared ray is to be generated using a widely available electric heating device, it is necessary to lower the temperature of the heat generation surface, so that a large number of electric heating devices are required. Or, there is a drawback that a larger electric heating device is required, but according to the present invention, the temperature of the heat generating surface of the conventional electric heating device is not lowered, and the heat generated from the conventional electric heating device causes a thin wall thickness. By heating the inner surface of the far-infrared radiation tube consisting of a metal tube, it has a heat generation surface that is sufficiently larger than the heat generation surface of electric heating equipment, so far infrared rays are generated from the outer surface of a thin metal tube that becomes colder. It was possible to obtain a simple and inexpensive far infrared radiant electric heater using various means.

The thin metal tube used as the far-infrared radiation tube in the apparatus of the present invention circulates a combustion gas of gas or kerosene in the tube and heats the temperature of the outer surface of the tube to 200 ° C. to 400 ° C. to generate far infrared rays. It is possible to use metal tubes widely used in far-infrared radiant heaters and far-infrared radiant sauna equipment. Since this is a cylindrical tube, there is little risk of distortion and deformation due to expansion and contraction due to heat. Therefore, it is already known that a sufficient service life can be obtained even with a very thin metal tube having a wall thickness of about 0.3 mm. Therefore,
By using such a metal tube, it is possible to obtain a far-infrared radiant electric heater which is not only inexpensive but also extremely lightweight and easy to handle.

On the other hand, when the sheathed heater 3 is used for a conventional sauna, a large number of sheathed heaters are accommodated in a narrow stove container and used to heat each other. On the other hand, in the present invention, since a set of sheathed heaters 3 is usually provided inside one far infrared radiation tube 4, it can be used at a lower temperature than before,
Further, since the far-infrared radiation tube 4 and the sheathed heater 3 having different temperatures and different expansion rates can freely expand and contract without being constrained to each other, there is little fear of distortion and deformation due to heat, and there is a feature and an effect that the durability is excellent. . Summarizing the above effects, it can be said that the far infrared radiant electric heater of the present invention is inexpensive, light and has sufficient durability.

Furthermore, in the present invention, by preventing the external air from circulating through the far-infrared radiation tube 4, the external air comes into contact with and flows into the high temperature sheathed heater 3 to take away the heat. Can be prevented as much as possible, and more energy of electric power can be converted into far infrared rays. Further, by arranging the sheathed heater 3 close to the far infrared ray emitting direction inside the far infrared ray emitting tube 4, the far infrared ray can be emitted more efficiently in the far infrared ray emitting direction.
By providing the sheathed heater 3 in the lower half of the far-infrared radiation tube 4, it is possible to heat the vicinity of the floor more strongly when used for a sauna or heating, so the air temperature at the upper part of the room is high and the lower part It also has the effect of correcting the shortcomings of air heating that the heating efficiency is too low and the heating efficiency is poor, and reducing the temperature difference between the sauna room and the room to be heated to save energy. Further, the far infrared radiant electric heater according to the present invention is also used in a far infrared radiant heater, a far infrared radiant sauna heater, a far infrared radiant heater for a coating or printing dryer, and a dryer for various processed foods. It can be widely used in various fields such as a far infrared radiation heater.

The present invention is not limited to the above-mentioned embodiments, and various modified embodiments are possible within the scope of the object of the present invention. That is, for example, (1) use an electric heater such as a nichrome wire or a quartz tube in place of the sheath heater 3, (2)
A connection insulator is provided at the bottom of the far-infrared radiation tube 4, and a sheath heater and the like are connected to the power source inside the far-infrared radiation tube 4.
(3) Using a thicker far infrared radiation tube 4 and incorporating a plurality of sheath heaters in one far infrared radiation tube 4,
(4) To apply heat-absorbing paint not only to the outer surface of the far-infrared radiation tube 4 but also to the inner surface of the tube to promote heat transfer from the sheath heater 3 to the inner surface of the far-infrared radiation tube 4, or (5) In the above embodiment, the far-infrared radiation tube 4 is vertically used vertically, but the far-infrared radiation tube 4 is laid horizontally and installed on a wall or ceiling to be used as a far-infrared radiation heater. Things, etc. are possible.

Since the present invention is constructed as described above, according to the present invention, a conventionally known electric heater such as a nichrome wire or a sheath heater is used, and a simple member is simply added and combined. A far-infrared radiant electric heater, which is simple, robust, and excellent in durability, capable of efficiently converting the generated heat into far-infrared rays and radiating the heat without lowering the temperature of the electric heater can be provided at low cost.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view showing a first embodiment of a far infrared radiation electric heater according to the present invention.

FIG. 2 is a partially cutaway side view of the first embodiment.

FIG. 3 is a partially cutaway plan view showing a second embodiment of the far-infrared radiation electric heater according to the present invention.

FIG. 4 is a partially cutaway side view of the second embodiment.

[Explanation of symbols]

 1 Power supply connection box 2 Power supply line 3 Electric heater such as sheath heater 4 Far-infrared radiation tube (metal tube) 4-1,4-2 Air flow hole 5 Reflector

Claims (6)

[Claims] 1. A far-infrared radiation tube has a metal tube (4) closed at one end and the other end fixed to a power supply connection box (1) for power supply, and the longitudinal central axis thereof is inside the metal tube. An electric heater (3) is provided in parallel with the inner wall of the metal tube with a predetermined gap, and a terminal portion of the electric heater is connected to a power source through a switch, and an outer surface of the metal tube (4) is provided. Is provided with a coating layer made of a material having a high absorptivity, and a reflecting plate (5) having a low absorptivity is provided in parallel to the metal tube (4) at a predetermined distance behind the metal tube (4). When electric power is supplied to the electric heater (3), the outer surface temperature of the metal tube (4) is 150 ℃ to 3 ℃.
A far-infrared radiant electric heater characterized in that the heating value of the electric heater, the length and thickness or surface area of the metal tube, the material of the coating layer on the outer surface of the metal tube, etc. are selected so as to be about 50 ° C. 2. The far infrared radiant electric heater according to claim 1, wherein the metal tube (4) is a thin-walled stainless steel circular tube. 3. The electric heater (3) housed in the metal tube (4) is provided eccentrically from the center of the metal tube to the side from which far infrared rays should be radiated. Alternatively, the far-infrared radiation electric heater according to item 2. 4. A metal tube (4) serving as a far-infrared radiation tube is closed at one end, and the other end is fixed to a power supply connection box (1) for power supply, and the central axis of the metal tube in the longitudinal direction thereof. An electric heater (3) is provided in parallel with the inner wall of the metal tube with a predetermined gap, and a terminal portion of the electric heater is connected to a power source through a switch, and an outer surface of the metal tube (4) is provided. Is provided with a coating layer made of a substance having a high absorptivity, and a far-infrared radiation plate (5) made of a steel plate or the like coated with a substance having a high absorptivity is provided on the rear part of the metal pipe (4) in a predetermined manner. The heat generated by the electric heater and the metal pipe should be set so that the outer surface temperature of the metal pipe (4) becomes about 150 ℃ to 350 ℃ when electric power is supplied to the electric heater (3). Far infrared radiation characterized by selecting the length and thickness or surface area of the metal, the material of the coating layer on the outer surface of the metal tube, etc. Heat heater. 5. The far infrared radiant electric heater according to claim 4, wherein the metal tube (4) is a thin-walled stainless steel circular tube. 6. The electric heater (3) housed in the metal tube (4) is eccentrically provided from the center of the metal tube to the side from which far infrared rays should be emitted. Alternatively, the far infrared radiant electric heater according to item 5.