INFRARED RADIATION EMITTER

Abstract

The disclosure relates to a gas-heated infrared radiation emitter comprising at least one radiating screen, which is for example made of ceramic and/or metal, in the form of at least one plate comprising a lower main surface and an upper main surface that are distant from each other, and a plurality of through-prisms, which are preferably hollow, extending from the lower main surface to the upper main surface, each prism being defined by a polygonal base and by an axis. The prisms may be juxtaposed with one another so that their polygonal bases form a tiling of at least one portion of the lower and upper main surfaces of said plate.

Claims

1. A gas-heated infrared radiation emitter comprising at least one radiating screen in the form of at least one plate comprising: a lower main surface and an upper main surface that are distant from each other, and a plurality of through-prisms extending from the lower main surface to the upper main surface, each prism being defined by a polygonal base and by an axis, wherein the prisms are juxtaposed with one another so that their polygonal bases form a tiling of at least one portion of the lower and upper main surfaces of said plate WO.

2. The emitter according to claim 1, wherein the prism bases are all hexagonal, triangular or square.

3. The emitter according to claim 1, wherein the lower and upper main surfaces are parallel to one another, wherein the axis of the prisms is perpendicular to the main surfaces and wherein the base of the prisms is the cross-section of the prisms.

4. The emitter according to claim 1, wherein said at least one plate also comprises a through-opening of size greater than that of the through-prisms, in order to facilitate and accelerate the ignition of the emitter.

5. The emitter according to claim 1, wherein said at least one plate has a degree of opening greater than or equal to 40%.

6. The emitter according to claim 1, comprising a plurality of screens in the form of at least one plate, said screens in the form of at least one plate being arranged in a plurality of planes parallel to one another.

7. The emitter according to claim 1, wherein the screen comprises at least two plates adjacently mounted in a same plane, said at least two plates being separated, at ambient temperature, by a thermally insulating material or else said at least two plates being mounted with clearance between them in said same plane.

8. The emitter according to claim 1, wherein said plate is made of a thermally conductive material or else is made of thermally insulating ceramic coated with a thermal conductor.

9. The emitter according to claim 1, comprising a burner plate, said burner plate acting as combustion surface, said screen in the form of at least one plate being position on the combustion-surface side of said burner plate.

10. The emitter according to claim 1, also comprising one or more additional screens arranged in one or more planes parallel to the plane of said screen in the form of at least one plate.

11. The emitter according to claim 1, wherein each prism has a form factor greater than 3.

12. The emitter according to claim 1, wherein the at least one radiating screen is made of ceramic and/or metal.

13. The emitter according to claim 2, wherein the prism bases are all identical.

14. The emitter according to claim 4, wherein the through-opening of said at least one plate is central.

15. The emitter according to claim 4, wherein the through-opening of said at least one plate is circular.

16. The emitter according to claim 6, wherein said screens are arranged in two planes parallel to one another.

17. The emitter according to claim 6, wherein said screens are arranged at a distance from one another.

18. The emitter according to claim 10, wherein said one or more additional screens are arranged at a distance from said screen in the form of at least one plate.

19. The emitter according to claim 11, wherein each prism has a ratio of a dimension along the axis over the largest dimension of the base, greater than 3.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0042] FIG. 1 is a partial section, in perspective, of an infrared radiation emitter with a screen according to the prior art;

[0043] FIG. 2 is a schematic representation, in perspective, of a first embodiment of the screen according to the disclosure for an infrared radiation emitter;

[0044] FIG. 3 is a schematic representation of a cross-section of an infrared radiation emitter equipped with the screen shown in FIG. 2,

[0045] FIG. 4 is a schematic representation, in perspective, of a second embodiment of the screen according to the disclosure for an infrared radiation emitter.

DESCRIPTION OF THE EMBODIMENTS

[0046] FIG. 1 shows a gas-heated infrared radiation emitter 1 including a screen 2 according to the prior art, for example in the form of a metal grid or braided metal wires.

[0047] The emitter 1 includes a frame 4 with a supply inlet 6 for the gases to be burnt, and a burner plate 8 arranged facing the inner surface of the screen 2. The frame 4 and the burner plate 8 define an inner chamber into which the gases are conveyed entering via the supply inlet 6.

[0048] The burner plate 8 may be, for example, a perforated ceramic plate, the perforations of which are intended to allow gases present in the inner chamber of the emitter 1 to leave. On leaving the perforations, the gases are then burned on the outer surface 10, or combustion surface of the burner plate 8 when there is a flame, and then heat the screen 2 arranged facing the outer surface 10.

[0049] In particular, as illustrated in FIG. 1, the burner plate 8 may comprise a crenelated or ribbed outer surface 10. Hence, the burner plate 8 can have, on the outer surface 10, various levels of combustion surface, for example two. The outer surface 10 can, for example, comprise parallel ribs arranged obliquely over the entire surface of the burner plate 8.

[0050] Such burner plates 8 with a plurality of levels of combustion surface are described, in particular, in document WO 2010/003904.

[0051] FIG. 2 schematically illustrates the general form of a screen 12 according to the present disclosure. The screen 12 is formed by a plate 14 formed by the juxtaposition of through-channels, or prisms 16, and having a lower main surface 18 and an upper main surface 20 (see FIG. 3) which are parallel in the present case. The plate 14 of the screen 12 may comprise, in particular, a thermally conductive material, for example a metal alloy or silicon carbide. Alternatively, the plate 14 may comprise a thermally insulating ceramic, for example cordierite or alumina, coated with a thermally conductive material, such as silicon carbide.

[0052] More precisely, the plate 14 of the screen 12 includes a plurality of through-channels 16, the through-channels extending from the lower main surface 18 to the upper main surface 20. The through-channels 16 having a prism geometry defined by a polygonal base and by an axis, in other words a geometry delimited, in space, by a lower polygonal base, an upper polygonal base at a distance from the lower polygonal base, and side walls connecting the sides of the polygonal bases to one another. In particular, the polygonal bases of the various prisms form a tiling of at least one portion of the main upper and lower surfaces of the plate 14.

[0053] As illustrated in FIG. 2, the channels 16 of the plate 14 are identical and with hexagonal base, and extend perpendicular to the main upper 20 and lower 18 surfaces. In other words, the channels 16 extend along an axis perpendicular to the upper 20 and lower 18 main surfaces. The channels 16 therefore have a prism geometry defined by a hexagonal base extending in the plane of the main surfaces 18, 20 of the plate 14, and an axis perpendicular to the main surfaces 18, 20. The upper and lower hexagonal bases of the through-channels 16 are thus identical, and the walls connecting the sides of the hexagonal bases are rectangles, optionally identical (see FIG. 3). The through-channels 16 allow the burned gas to circulate at the outer surface 10 of the burner plate 8, but are also heated by these and therefore emit infrared.

[0054] The hexagonal base of the through-channels 16 is chosen so as to enable tiling of at least one portion of the upper 20 or lower 18 main surface. A hexagonal base makes it possible to obtain an overall honeycomb structure, in which the prisms are juxtaposed with one another so that their bases cover said portion of the upper 20 or lower 18 main surface. In particular, the side walls of the through-channels 16 are common between two adjacent or neighbouring through-channels 16.

[0055] However, the hexagonal base is not the only polygonal base enabling a tiling of at least one portion of the upper 20 or lower 18 main surface. The through-channels 16 can thus have a triangular base, or even a square base, as shown in FIG. 4.

[0056] Similarly, it is also possible to envisage through-channels 16 having polygonal bases of the same shape but different sizes. Thus, the size of the polygonal base of the through-channels 16 could vary according to the position with respect to the centre and/or to the ends of the plate 14, while retaining a tiling of at least one portion of the main surface of the plate 14.

[0057] Thus, through the use of through-channels 16 that are juxtaposed so that their bases form tiling of at least one portion of the main surface of the plate 14, a particularly high degree of opening of the plate is obtained, while retaining a mechanically stable and durable structure. The plate according to the disclosure can thus have a degree of opening greater than or equal to 40%, and more generally greater than or equal to 60%, or else greater than or equal to 80%. At the same time, the emitter 1 can have a power greater than or equal to 50 kW/m.sup.2, preferably 100 kW/m 2, or even 200 kW/m.sup.2.

[0058] In order to improve the operating stability, the plate 14 can also comprise a through-opening 24 of size greater than that of the through-channels 16. The through-opening 24 can improve the operation of the emitter, in particular at ignition.

[0059] The through-opening 24 can be produced, in particular, by piercing the plate 24, for example using a drill bit, leading to the removal of some of the walls of the channels 16. An opening 24 can then be obtained that is larger than the channels 16. The through-opening 24 is preferably produced at the centre of the plate 14.

[0060] FIG. 3 shows a section through the screen 12 shown schematically in FIG. 2. As can be seen in FIG. 3, the axis of the channels 16 of the screen 12 is oriented in the direction of circulation of the burned gases, in other words from the outer surface of the burner plate 8 to the upper main surface 20 of the screen 12.

[0061] In FIG. 3, the emitter 1 includes only a single screen 12, and the screen 12 includes only a single plate 14. However, the screen could likewise comprise a plurality of plates 14 arranged in a same plane, one beside the other, for example two adjacent plates 14, or else four plates 14 arranged in a square. Such an embodiment makes it possible, in particular, to obtain large surface-area screens, even when the plates 14 can only be manufactured with small dimensions. Such an embodiment may also be preferred when the emitter 1 includes a plurality of coplanar combustion plates 8. In this case, each plate 14 of the screen 12 can be positioned facing one and only one burner plate 8.

[0062] In order to limit the risks of deterioration connected to thermal expansion and/or thermal shocks, separations, made of thermally insulating material for example, can be provided between the plates 14 of the screen 12, or else clearance can be provided between the plates 14 in order to leave a little freedom between the plates 14 and between them and the peripheral contour of the screen 14.

[0063] When the screen includes a plurality of coplanar plates 14, the through-channels 16 of the various plates can be of different size or shape, for example some with square base and others with hexagonal base, or else oriented in different directions, for example in the case of triangular based channels.

[0064] Similarly, the through-opening 24 of each plate 14 need not be centred with respect to the plate 14 but, by contrast, may be positioned in a central zone of the screen 12.

[0065] Finally, the emitter 1 may also comprise a plurality of screens, in other words a plurality of levels parallel to one another and parallel to the burner plate 8, that can be heated and emit infrared. Thus, the various screens may all comprise one or more plates 14 with channels 16 according to the present disclosure. In particular, the geometry of the through-channels 16 and/or their size can vary between the various screens, according to the distance separating the screen from the burner plate 8. Alternatively, the emitter 1 can comprise at least one screen with one or more plates 14 having channels 16 according to the present disclosure, in combination with screens of the prior art.

[0066] FIG. 4 shows a second embodiment of the disclosure. More precisely, FIG. 4 shows a screen 12 in which the through-channels 16 are prisms having a square polygonal base.

[0067] As shown in FIG. 4, the screen 12 according to the second embodiment of the disclosure does not have a plate 14 with a honeycomb structure, but with a grid structure. However, the dimensions of the different channels 16 remain identical to one another, even though it is possible to provide channels with different sizes; twice as large, for example.

[0068] As in the case of the first embodiment, a through-opening 24 can be provided, in particular at the centre of the plate 14.

[0069] Thus, the specific structure of the screen according to the present disclosure makes it possible to obtain operating properties, in particular at start-up of the emitter, which are better than those of emitters from the prior art, while retaining an inexpensive screen that is reliable over time.