WO2014057215A1

WO2014057215A1 - Improved infrared halogen emitter

Info

Publication number: WO2014057215A1
Application number: PCT/FR2013/052404
Authority: WO
Inventors: Olivier DEMANGEON; Benoît DIDIER
Original assignee: Dirtech
Priority date: 2012-10-08
Filing date: 2013-10-08
Publication date: 2014-04-17
Also published as: FR2996720B1; FR2996720A1

Abstract

An infrared halogen emitter used in the field of radiation heating, comprising a tungsten filament (1) and a protective casing (2) combined with a filter (4) limiting the light intensity. It comprises a control device designed such that the filament (1) emits at a temperature of between 1500 and 1800K, and the protective casing (2) has the shape of a tube, while the filament (1) is arranged inside the protective casing and comprises a series of curvatures, changes of direction and straight segments, such that it has a shape that enables it to occupy a large portion of the inner space of the casing (2), and so as to house a significant quantity of tungsten inside the casing (2), i.e. a quantity suitable for enabling operation within said temperature range.

Description

IMPROVED INFRARED HALOGEN TRANSMITTER

The invention relates to the field of infrared halogen emitters for radiant heating, for example for space heating, on a restaurant terrace, or any other application requiring the heating of a target by infrared radiation.

It relates more particularly to an improved infrared halogen transmitter, which does not dazzle.

Short infrared halogen emitters are used in many industrial sectors for the following advantages:

- Ability to have a high power density

- Small footprint

- Low inertia (on ignition and cooling)

- Ease of implementation

One of the major drawbacks is dazzle (high light intensity) with this type of transmitter. Since these infrared halogen emitters emit between 300 and 8000nm (with a peak emission between 850 and 1850nm, depending on the temperature of the filament), the beginning of the spectrum still emits in the visible spectrum, which produces a dazzling .

The reduction of this glare is the subject of many models of emitters for filtering some of the visible light as follows:

- Use of quartz tube doped in the mass (with copper oxides for example)

- Use of a double tube doped in the mass (with copper oxides for example)

- Use of filter (deposition of successive layers of Sio2 and Fe03) on the outer wall of the quartz tube

All these different transmitter models reduce the light intensity compared to a transmitter made with a transparent quartz tube but fail to avoid glare.

The present invention proposes to remedy at least some of the aforementioned drawbacks and proposes a solution which to avoid completely, or at least to a large extent, the glare. The purpose of the new transmitter is to reduce, or at least a large part, the glare of an infrared halogen transmitter without loss of power density and efficiency.

For this purpose, the invention relates to an infrared halogen emitter used in the field of radiant heating, comprising a tungsten filament (1) and a protective envelope (2) associated with a filter (4) for limiting the intensity. light. This emitter is particular in that it comprises a control device designed such that said filament emits at a temperature of between 1500 and 1800 K; and in that said protective envelope has a tube shape, whereas said filament is disposed inside said protective envelope and comprises a succession of curvatures, changes of directions and straight segments, so that it has a shape allowing it to occupy a large part of the interior space of said envelope, and so as to house inside said envelope a significant amount of tungsten, namely an amount able to allow operation in said range temperature.

According to other characteristics:

the filament present, in view in the axis of the tube, a star shape; such a shape makes it possible to house more wire in a given tube, and makes it possible to have a small contact surface between the filament and the tube,

said casing may be coated with a filter formed of successive layers of silica and iron oxide, allowing a complementary filtering of the emitted light,

said filter may be composed of five layers of iron oxide and four layers of silica arranged between the layers of iron oxide, thus providing a particularly effective filter for the emitted light;

this filter can be composed of four layers of iron oxide and four layers of silica arranged between the layers of iron oxide, one of the silica layers being disposed directly on said envelope, thus providing another particularly effective filter of the emitted light.

The advantage of the transmitter according to the present invention resides in particular in that it emits only very little, ideally not at all, in the visible range. Thus, it does not dazzle the users, and moreover all the energy radiates in the infrared spectrum, which improves its performance.

Other features and advantages of the invention will emerge from the following detailed description relating to an exemplary embodiment given by way of indication and not limitation.

The understanding of this description will be facilitated with reference to the accompanying drawings, in which:

- Figure 1 shows a perspective view of a filament of the state of the art;

FIG. 2 represents a front view of the filament of FIG. i;

FIG. 3 represents a perspective view of an emitter tube provided with the filament of FIG. 1;

FIG. 4 represents a front view of a filament according to one embodiment of the invention;

FIG. 5 represents a front view of an emitter tube provided with the filament of FIG. 4;

The filament 1 of this type of transmitter of the state of the art may have a different temperature and shape. The tungsten wire can be more or less electrically charged and can therefore vary up to about 3300K. The less electric wire the tungsten wire is charged (the less it is hot), the higher the emission peak of the emitter will shift towards the average infrared, and the more the filament is hot, the higher the percentage of energy emitted in the spectrum. visible is important (so the more the transmitter dazzles). This filament 1 generally has a coil shape, of diameter much smaller than the diameter of the tube 2 in which it is housed, with rings support 3 at regular spacing, to keep the rest of the coil away from the inner face of the tube 2.

A filament 1 according to the invention is developed with a low tungsten wire temperature, between 1500 and 1800K, which makes it possible to keep a short response time in terms of ignition and cooling, and to shift the emission peak towards the average infrared and therefore to decrease the percentage emitted in the visible spectrum.

Decreasing the filament temperature to 1500 to 1800K makes it possible to maintain a low inertia of ignition and cooling.

The chosen temperature range also makes it possible to obtain an emission peak between 1600 and 1850 nm and thus to reduce the percentage emitted in the visible range, which can be reduced to 20% at 800 nm of its peak value. For comparison, with a transmitter at 2450K, we obtain a peak emission near 1180nmn and the percentage emitted at 800nm is still greater than 60% of the value of this peak. With a transmitter at 2750K, the peak emission is around 1060nm, and the percentage emitted at 800nm is greater than 80% of the value of this peak. As the percentage emitted in the visible is lower, the part emitted in the infrared of a transmitter according to the invention is greater than for standard transmitters (standard filament temperature between 2000 and 2500K), therefore the efficiency and the yield, are improved on targets with good infrared absorption, such as water-based products, especially human bodies.

To allow the filament according to the invention to emit at a power equivalent to a filament of the state of the art, with a lower temperature, a larger amount of tungsten wire is required.

According to a preferred embodiment of the invention, to be able to place in a tube 2, the amount of tungsten wire required for this filament 1, there is given to said filament 1 a particular shape, consisting of a succession of curved and straight segments, in this case a "star" winding. Such a shape is obtained by practicing a series of quasi-semicircular curvatures and straight segments forming ovoid turns, shifting with respect to each other and having an outside diameter slightly smaller than the inside diameter of the tube. The filament has in view in the axis of the tube a star shape. The quasi-semicircle shape here should be understood as a curvature of an angle slightly less than 180 °, to allow the wire after curvature to move slightly away from the wire before the curvature, to go to a point of the diameter of the star which is slightly offset from the opposite of the curvature, so that a succession of such curvatures separated by straight segments can gradually describe the entire circumference of the star, while shifting step by step along the axis of the star. Thus, a "star" with thirteen branches according to FIGS. 4 and 5 will be formed of thirteen "quasi-half-circles", and will have a depth of the order of thirteen thicknesses of wire along the axis of the tube. Each quasi-semicircle has an angle of curvature of 180 ° minus one thirteenth of 180 °, so about 166 °, separated by straight segments. For a star shape with fewer branches, the angle of the quasi-semicircles will be smaller. A complete filament will consist of a succession of such "stars", the last of which may be only partial, to fit the length of the tube, or the length of the wire that has been determined to obtain the heating power desired.

Such a star shape also brings the following advantages:

- The contact surface with the envelope (tube) quartz is weak, and therefore the heat exchange is also low, which allows not to heat the tube too much; it is thus possible to minimize the energy losses while controlling the temperature of the filament better,

the apparent outer diameter of the assembly formed by the filament may be equal to the inside diameter of the tube less about 8 ~ 10%, which allows a good compromise between the volume useful for the filament, and the distance between the filament and the inside of the tube,

- The mechanical strength of the filament is improved compared to a "classic" extrusion, because of its shape.

According to another preferred embodiment of the invention, a filter 4 is added outside the tube (shown partially in FIG.

Two methods of applying such a filter are possible, a dip process, and a vaporization method.

For the soaking process, the quartz tube, constituting the envelope of the emitter, is frosted on the surface (sandblasted) and then coated by successive layers of product SiO 2 and Fe 2 O 3.

The frosting of the surface allows the attachment of the 1st layer.

The layers are dip-coated with a total of five to thirteen layers.

- Si02 is applied on odd-numbered layers.

- Fe203 is applied on even numbered layers.

Heating at 750 ° C allows each layer to be cooked before laying the next layer and thus makes it possible to form the filter.

The color emitted by the transmitter is located at x = 0, 57 +/- 0.048 and y = 0.397 +/- 0.027

For the vaporization process, the quartz tube constituting the envelope of the emitter is coated with successive layers of SiO 2 and FeO 3 products.

The filter is obtained by deposition after decomposition of compounds in the vapor state (CVD).

In total, two to eight layers are deposited, the first layer being SiO 2.

The color emitted by the emitter is located at x = 0, 698 +/- 0.05 and y = 0.318 +/- 0, 033.

The combination of these two techniques, filament with a temperature below 1800K and filter based on SiO 2 and FeO 3, makes it possible to obtain a transmitter with very low illumination. The advantage of the transmitter according to the present invention resides in particular in that it emits only very little, ideally not at all, in the visible range. Thus, it does not dazzle the users, and moreover all the energy is diffused in the form of infrared radiation, which improves the efficiency.

Claims

An infrared halogen transmitter used in the field of radiant heating, comprising a tungsten filament (1) and a protective envelope (2) associated with a filter (4) for limiting the luminous intensity, characterized in that it comprises a control device designed so that said filament (1) emits at a temperature between 1500 and 1800K; and in that said protective envelope (2) has a tube shape, while said filament (1) is disposed inside said protective envelope (2) and comprises a succession of curvatures, changes of directions and of straight segments, so that it has a shape that allows it to occupy a large part of the interior space of said envelope (2), and so as to house a significant amount inside said envelope (2) tungsten, namely an amount capable of allowing operation in said temperature range.

2. Emitter according to claim 1, characterized in that the filament (1) has, in view in the axis of the tube (2), a star shape.

3. Emitter according to one of the preceding claims, characterized in that the filter (4) of said casing (2) is formed of successive layers of silica and iron oxide.

4. Emitter according to the preceding claim, wherein said filter (4) is composed of five layers of iron oxide and four layers of silica arranged between the iron oxide layers.

5. Emitter according to claim 3, wherein said filter (4) is composed of four layers of iron oxide and four layers of silica arranged between the iron oxide layers, one of the silica layers being disposed directly on said envelope (2).