JPS5814482A - Heater - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating element that emits far infrared rays and is used for heating for heating or drying.

It is well known from physics that black bodies at low temperatures emit far-infrared rays.

For example, a perfect black body at 100 degrees Celsius emits far infrared rays of a continuous spectrum with a maximum wavelength of 7.76 μ into space at absolute zero at a rate of O=1099'W, 2J.

Similarly, a perfect black body at 10°C emits far infrared rays having a maximum wavelength of 10.23μ at a rate of 0.0365W/c-. 80% of the radiant energy is contained between wavelengths 0.76 times to 6.6 times the wavelength of the maximum value.

The above is the case of a completely black body, and actually existing heating elements generally have a lower emissivity than this and emit so-called gray radiation.

This emissivity varies depending on the material, but for far infrared rays,
Ceramics, glass, marble, stone, etc. have a completely black body of about 90~
It has an emissivity of approximately 93%, and it is also known that painted surfaces such as enamel paint have approximately the same emissivity.

The present invention utilizes these properties to directly send energy in the form of radiation to the target object without heating the air around the heating element, thereby achieving a significant energy-saving effect in the field of drying or heating. The purpose is to provide a heating element.

Conventional hot air heaters and the like have the disadvantage that because they send out warm air to warm the entire room, this heat escapes to the outside through walls, windows, ceilings, etc. Therefore, a considerable amount of calories were required for heating.

In addition, conventional radiant heating elements include electric stoves using nichrome wire, infrared lamps using tungsten wire lamps, and gas stoves using red-hot pottery, but all of them have limited area. Since a small number of high-temperature radiators are used, there is a risk of fire or burns if the object to be heated is brought close to it, and conversely, the heating effect decreases rapidly if the object is moved away.

The present invention eliminates such drawbacks, and
To provide a heating element that uses a low-temperature radiator of around °C and has a wide area to form a surface heating element, and further prevents the movement of air near the radiating surface to reduce heat loss due to air convection. be.

The present invention will be explained in detail below.

FIG. 11 is a perspective view showing an embodiment of the present invention, and FIG. 2 is a sectional view thereof. In FIGS. 1 and 2, 1 is a flat radiator, 2 is a heat insulating material, 3 is an outer casing, 4 is a grid, and 5 is a heat source for warming the radiator 1. The radiator 1 has a large surface area and has a structure that allows the surface to be heated uniformly.

Generally, a metal plate is used, and for example, electricity can be connected to the back side of the plate.
It can be heated with gas, kerosene, hot water, hot air, etc. In the example of FIG. 2, the radiator 1 is heated by a heat source 5 made of a hot water pipe. The surface that emits far-infrared rays is coated with a paint with high emissivity, such as enamel. Metal surfaces (1) generally have extremely poor emissivity,
For example, a well-polished copper plate emits only about 4% of a completely black body, but if you paint it with enamel, the emissivity is 90.
%. Also, the emissivity can be improved by pasting heat-resistant rubber such as silicone rubber. ``Metal is used as the base material because metal has good thermal conductivity, so it is easy to make the surface temperature uniform.

The surface temperature of this radiator 1 is maintained at about 80°C to 30°C. Now, if we set it to 100 degrees Celsius, it will go around. At 300°C, this becomes a rate of 5180 W/m''.

The heat insulating material 2 is used to prevent heat loss to the back surface (backward) when radiation is not directed toward the back surface but only toward the front surface. This heat insulating material 2 may be similar to the heat insulating material used for the walls of ordinary houses.

The outer casing 6 is an outer casing that supports the entire heating element, and the front side is open to allow radiation to pass through.

The grating 4 is provided to prevent the flow of air near the radiation surface in order to reduce heat loss escaping from the surface of the radiator 1 into the air by convection.

The grating 4 is provided close to the radiator 1 and prevents air movement due to convection or wind around the surface of the radiator 10, and prevents heat loss due to heat transfer from the surface of the radiator 1 to the air. The purpose is to reduce the amount of heat lost.

For this purpose, the gap between the radiator 1 and the grating 4 is preferably small.

Further, the deeper the depth of the grating 4, that is, the length t in FIG. 2, the more suitable for the above-mentioned purpose.

Furthermore, the finer the lattice width of the lattice 4, the more convenient it is to prevent air movement.

The material of the grid 4 may be plastic, metal, paper, wood, etc. depending on the temperature of the radiator 1.

For example, a metal lattice formed in the shape of a lattice 4
It is suitable as a material for

As the depth t of the grating 4 increases, the directivity of the radiator 1 becomes sharper, so there is an appropriate depth depending on the purpose.

The effectiveness of the grating 4 is highest when the radiation surface of the radiator 1 is horizontal and radiates downward.

This is because the high temperature air heated on the surface of the radiator 10 is -F
As it tries to move toward the surface of the radiator 1, its movement is blocked by the grating 4 and the surface of the radiator 1, and it stays near the surface of the radiator l, maintaining a high temperature, preventing the surface of the radiator 1 from being cooled by the air. It will be done.

On the other hand, when the radiation surface of the radiator 1 is horizontal and faces upward, and radiates upward, the effect of the grating 4 is the least.

Even in this case, if the grid is fine, air convection will be hindered to a certain extent and it will be somewhat effective.

When the surface of the radiator 1 is vertical, the effect of the grating 4 is intermediate between the two examples of 5 or more.

FIG. 3 is a sectional view showing another embodiment of the present invention.

In FIG. 3, 6 is a film that transmits radiation in the far infrared region.

As mentioned above, the radiator l at about 100°C to 300°C is several μ
It emits far infrared rays in a band ranging from m to several 10 μm. The film 6 is a film that transmits radiation in this band well.

Some such films can be found in plastic films.

For example, taking a polyethylene film as an example, its infrared ray pass band is as shown in FIG.

As you can see in this figure, most of the far infrared rays pass through. However, since air flow can be blocked, losses due to convection can be further reduced by attaching such a film to the surface of the grid 40 as shown in FIG.

The air inside the grid 4 covered with the film 6 is confined within a narrow space, hardly causing convection, and effectively acts as a heat insulator. Moreover, since far-infrared rays are radiated through the air and the film 6, the heating effect of the radiation can be sufficiently exerted.

Such an effect of the film 6 is particularly effective when the radiator 1 is horizontal and emits radiation upward. In such a case, the air heated on the surface of the radiator 1 would rise upward through the grid 4 when the film 6 was not present, causing air convection and cooling the radiator 1, but the film 6 would If so, this convection can be prevented.

For the same reason, it is also effective when the radiator 1 is vertical.

゛Although it is effective to use only the film B without the grid 4 because it blocks air convection to some extent, it is more effective if both the grid 4 and the film 6 are present because the air is subdivided and confined within a small space. In addition, cooling of the radiator 1 through heat transfer, in other words, loss can be prevented.

This effect is particularly effective when the radiator 1 is used for drying purposes.

When drying, it is normal to forcefully blow air to speed up drying in order to release evaporated water vapor and other vapors to the outside. Great insulation effect.

As is well known, the amount of heat transferred from a plane to the surrounding air by convection is proportional to the product of heat transfer coefficient, surface area, time, and temperature difference.

Various experimental formulas have been given for the heat transfer coefficient by several scholars, but when we calculate the heat transfer coefficient due to convection from the flat plate surface in the case of forced convection using the formula for Jugeθ, we find that it is a smooth surface. Assuming the wind speed is 4rn, it is approximately 18 Kad/h°C.

If there is no grid 4 or film 6, the amount of heat carried away by the wind from the surface of the radiator 10 by convection is 1 per radiator I, assuming that the surface temperature of the radiator 1 is 150°C and the wind temperature is 30°C. 18×(150℃−
50℃) = 2160! It is. When the surface temperature of the radiator 1 is 150 DEG C., the amount of heat radiated from the radiator 1 to an object at 30 DEG C. is -1206 per 91 hours per 1ff1, assuming an emissivity of 90%.

In other words, in order to obtain negative radiant heat at 1206, (1206+2・
x60) Since the amount of heat required is Kd, the heat due to convection exceeds the heat due to radiation. Although the calculations above are rough estimates, they should be sufficient to know the magnitude of loss due to convection.

On the other hand, when the path plate 4 and the film 6 are present, the heat carried away by the wind is greatly reduced due to the above-mentioned heat insulating effect of both.

The thermal conductivity of the air layer created by the grid 4 and the film B varies depending on the depth and fineness of the grid 4, but the temperature difference 1
The amount of heat flowing through the grid 4 and the film 6 per hour per degree Celsius is approximately 3 to 5 Kd.

Therefore, the greater the heat transfer from the surface due to the wind, the more the film 6
Since the 0 surface is cooled down, the amount of heat removed from that surface is less than if the surface of the hot radiator I were directly exposed to the wind.

When the surface temperature of the radiator 1 is 150°C, the surface temperature of the film 6 is around 50 to 60°C in the above example when the wind speed is 4 m, and the heat loss due to the wind is about 1 in 360 to 540°C. This is significantly reduced compared to the aforementioned 2160 Kcrll.

Due to the action of the grid 4 and the film 60, the amount of heat required to obtain the same radiation is approximately halved, and this method is found to be particularly effective when drying under forced ventilation. Ru.

In addition to polyethylene, suitable materials for the film 6 include polyamides, such as nylons (registered Koroku) such as nylon 11 and nylon 61゛〇-, and polypropylene.

High-density polyethylene absorbs far infrared rays a little more than low-density polyethylene, but it has a high heat resistance, so it is very suitable as a material for film 6, and its infrared transmittance is lower than that of the above-mentioned films. The best.

Furthermore, as another embodiment, the radiation surface of the radiator 1 shown in FIG. 2 or FIG. 5 may be covered with cotton-like fibers. This prevents air convection around the radiation surface and prevents heat loss. If the cotton fibers are thin and their density is not too high, far infrared rays will be emitted through the gaps.

The fiber material can be made of a material that transmits far infrared rays, such as nylon (registered Koroku), etc., but if heat resistance is particularly required, in other words, the surface temperature of the radiator should be around 30°C. In such cases, glass fiber is suitable.

If a metal that reflects far infrared rays well, such as aluminum, is vapor-deposited on the surface of glass fiber, most of the far infrared rays will be reflected by the fiber surface, and the far infrared rays absorbed by the fiber will be reduced, further increasing the effect. do.

The appropriate temperature of the radiator 1 is 8Q, about 300°C. If it is much lower than this, the amount of radiation per unit area will be too small, and the area of the radiator 1 required to obtain the desired heating effect will become too large.

In addition, if the temperature gets too high, there is a risk of burns or fires, and due to the high temperature, a suitable film 4 that transmits far infrared rays may not be used.
It becomes difficult to obtain.

Various materials can be used for the radiator 1, such as metals and ceramics, but metal is most suitable since it is easy to make the surface eagleness uniform. Among them, materials with good thermal conductivity such as aluminum and copper are easy to use. However, when using metal, the emissivity of metal is poor, so it is necessary to paint the surface or bake the enamel.
It is necessary to increase the emissivity by attaching something with good reflectivity, such as silicone rubber or plaster.

As mentioned above, by heating the planar radiator 1 to about 80-600°C and attaching the grating 4 to its surface,
A heating element that efficiently radiates heat rays can be obtained. Further, by covering the outside of the grating 4 with a film 6 that transmits far infrared rays, the effect can be further enhanced. Also, radiator 1
A similar effect can be expected by covering the surface with cotton-like fibers. These inventions bring about the following various effects.

To heat with air, the temperature of the air must be higher than the temperature required by the object to be heated, but when heating by radiation, the temperature of the air must be lower than that of the object to be heated. The heat loss can be reduced accordingly. Thermal efficiency is high because the heating source is directly heated without heating the surrounding air. Furthermore, since heating is done using radiation (a type of radio waves), there is no time delay in the heating effect. Even in places where cold wind blows, such as outdoors in winter, the grid 4, or the grid 4 and the film 6, the fiber 7, or a combination thereof prevents the radiator from cooling, so a heating effect can be expected. It can effectively heat buildings with high ceilings, such as large warehouses and open-air rooms.

The temperature of the radiator 1 is lower than that of a normal stove, etc., and
Since it is insulated with a film, there is no risk of fire or damage. Since the radiation is in the far infrared region, it generally has a high heating effect. For example, white enamel or white cloth, which reflects most of the visible light, absorbs most of the far infrared rays.

Since the radiator 1 has a large area, it has a wide band-shaped directivity characteristic, and the warmth does not change suddenly depending on the distance from the heat source, unlike in the case of a point heat source, and is relatively unaffected by distance. It's difficult to accept. That is, there is no fear of fire or burns even if you are close to the heating element, and it is relatively warm even if you are far away.

Since the grating 4, or the grid 4 and the film 6, or the fiber 7 reduce the loss due to the opposition to ', fewer calories from the heat source are needed to obtain the required amount of radiation heat. Therefore, it is particularly effective in dryers that use forced ventilation.

As described above, the present invention can provide a heating element with a simple structure and a large energy saving effect, and its economical effects are significant.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention, FIG. 2 is a sectional view showing an example, and FIG. 4 is a diagram showing the transmittance of polyethylene in the far infrared region. l... radiator, 2... heat insulating material, 4... lattice, 5...
...Heat source, 6...Film. Patent applicant Kokusai Technological Development Co., Ltd.) 4th wavelength (μ) Wave number (cIn')

Claims (1)

[Claims] (1) A radiator having at least one radiation surface;
A heating element comprising means for warming the radiator and a grid provided in front of the radiating surface to prevent heat loss due to air convection. (2) The heating element according to claim 1, wherein the radiator is made of a metal plate whose surface is covered with a material having a high emissivity. (5) The heating element according to claim 1, wherein the grid is covered with a film that transmits far infrared rays. (4) The heating element according to claim 1 or 3, wherein the radiation surface of the radiator is covered with cotton-like fibers.