EP0196956A1 - Electrical heating arrangement for gas with a tubular conductor - Google Patents

Abstract

Electrical heating installation for gas comprising at least one uninsulated, electrically conducting tubular element (1), folded back on itself in pleats so as to form at least one sheet of substantially parallel conducting segments (3), each of these segments being connected at one of its ends to one of the adjacent segments by a 180 DEG bend (4), and at the other of its ends to the other adjacent segment by another 180 DEG bend (5). The said tubular element is suspended from an electrically insulating carrier structure (2) in such a way that the said conducting segments are arranged substantially vertically, the suspension points being formed at the site of the bends (4) situated on the upper side of the sheet. <IMAGE>

Description

The present invention relates to an electric gas heating installation, and more particularly such an installation comprising at least one non-insulated electrically conductive tubular element, folded back on itself in an accordion manner so as to form at least one ply of substantially parallel conductive sections, each of these sections being connected at one of its ends to one of the adjacent sections by a 180 ° bend and at the other of its ends to the other adjacent section by another 180 ° bend.

Electric heating installations in which the conductor is a non-insulated metal tube, are already well known in the art. However, if these installations are large and intended for high temperatures, it has not yet been proposed a satisfactory solution for fixing the conductive elements.

This is the case, for example, of air heating installations intended for drying fodder.

A first problem which arises in this case is that of the connection of the conductive elements to the structure of the installation, a connection which must be carried out in a manner which is both electrically insulated and thermally insulated.

Another problem lies in the maintenance of the sections of conductors with respect to one another so as to avoid any contact which would cause a short circuit. This problem is often made more difficult to solve because the conductive elements are in an air flow which can be at relatively high speed.

Other difficulties generally arise due to the expansion of the heating elements caused by their heating. This is how these elements can be brought by the Joule effect to temperatures reaching 1100 ° C. Under such conditions, the means of fixing the heating elements to the structure of the installation must allow these expansions. In addition, the mechanical resistance of the heating elements is greatly reduced at such temperatures, which causes additional difficulties.

The present invention aims to overcome these drawbacks and more particularly aims to provide means for connecting the heating elements to the structure of the installation and to position these elements relative to each other, including at high temperature.

To this end, the invention has for its object an electric gas heating installation comprising at least one non-insulated electrically conductive tubular element folded back on itself in an accordion manner so as to form at least one ply of substantially parallel conductive sections, each of these sections being connected at one of its ends to one of the adjacent sections by a 180 "elbow and at the other of its ends to the other adjacent section by another 180 ° elbow, characterized in that said tubular element is suspended from an electrically insulating support structure so that said conductive sections are arranged substantially vertically, the suspension points being arranged at the location of the elbows located on the upper side of the ply.

In a preferred embodiment of the invention, electrically insulating spacers arranged between the conductive sections so as to position these conductors relative to each other and to avoid any contact liable to cause a short circuit.

The spacers are advantageously carried by the tubular element itself so that they follow the movements of the latter during its elongation due to its heating.

In the case where the installation comprises several plies of conductive sections, the spacers can be formed of plates arranged between two plies of sections and be placed on support members mounted on at least some of these sections.

These plates can be notched plates to allow the passage of sections of the tubular element.

The above-mentioned spacers are therefore mounted in the vertical region of the sections of the tubular element, but other spacers can also be mounted at their lower part.

In a particular embodiment of the invention, these other spacers are suspended from said tubular element at the location of the elbows located on the lower side of the ply.

Preferably, supports integral with the carrying structure are provided below said other spacers, at a distance such that these other spacers come to rest on the supports when said tubular elements elongate under the effect of heat.

As a result, when the heating element is in a state of less mechanical resistance due to its heating, it no longer has to bear the weight of the lower spacers which are directly supported on elements integral with the support structure .

Preferably, the other spacers are suspended by means of guide rods passing through holes formed in these other spacers, which are themselves placed on washers fixed to said rods.

Consequently, as soon as the lower spacers are placed on the fixed supports, an additional elongation of the tubular elements causes the guide rods to slide in the holes of the spacers. These rods thus guide the lower part of the heating elements and their relative positioning.

Preferably, the tubular member is flattened in the radial direction in the area of the elbows.

This results in a better distribution of the streamlines which otherwise tend to concentrate in the part of minimum radius of the tubular element.

It was found that it was advantageous to give the tubular element in the area of the elbows a section having two rounded parts at its ends and a central part of lesser thickness.

In a particular embodiment of the invention, the suspension points comprise a substantially V-shaped rod whose ends of the branches are arranged substantially tangentially and fixed to the curved part of said elbows.

As a result, the weight of the tubular element and the weight of the lower spacers are taken up substantially vertically in each section, which avoids deformation of the elbows at high temperature.

• -la figure 1 est une vue en élévation d'une nappe de conducteur dans une installation de chauffage selon l'invention,
• -la figure 2 est une vue en coupe de plusieurs nappes de conducteur selon la ligne II-II de la figure 1,
• -la figure 3 est une vue à plus grande échelle du détail III de la figure 1,
• -la figure 4 est une vue en coupe selon la ligne IV-IV de la figure 3,
• -la figure 5 est une vue agrandie du détail V de la figure 1 à la même échelle que la figure 3,
• -la figure 6 est une vue en coupe selon la ligne VI-VI de la figure 5, et
• -la figure 7 est une vue agrandie du détail VII de la figure 1 à la même échelle que les figures 3 et 5.

A particular embodiment of the invention will now be described by way of nonlimiting example with reference to the appended schematic drawings in which:

• FIG. 1 is an elevation view of a layer of conductor in a heating installation according to the invention,
• FIG. 2 is a sectional view of several conductor plies along the line II-II of FIG. 1,
• FIG. 3 is an enlarged view of detail III of FIG. 1,
• FIG. 4 is a sectional view along line IV-IV of FIG. 3,
• FIG. 5 is an enlarged view of detail V of FIG. 1 on the same scale as FIG. 3,
• FIG. 6 is a sectional view along line VI-VI of FIG. 5, and
• FIG. 7 is an enlarged view of detail VII of FIG. 1 on the same scale as FIGS. 3 and 5.

FIG. 1 represents a heating installation according to the invention comprising a tubular element 1 suspended from a support structure 2 in a gas flow.

The tubular element 1 is folded back on itself in an accordion to form vertical sections such as 3 connected to the adjacent sections by upper bends 4 and lower bends 5 at 180 °.

It is thus possible to form one or more plies using the same tubular element, the two ends of which are connected to a source of electric current (not shown).

In the zone of each elbow 4 and 5, the tubular element is flattened radially, as shown in. FIG. 4, so as to present two rounded ends 6 connected by a zone of lesser thickness 7. This flattening results in a regular distribution of the current lines in the conductor.

Rods 8 bent substantially in the shape of a V are disposed substantially tangentially to the tubular element and are welded to this element in the region of the upper elbows 4.

This welding is carried out at points 9 substantially vertical to the sections of vertical conductors 3, so as to make the elbows bear a minimum load.

The rods 8 thus form a ring in which a hook 10 is engaged, the rod of which passes through the supporting structure 2 on which it is retained by means of a washer 11. As can be seen in FIG. 4, a metal rod of smaller cross section 10a is welded to the beak of the hook 10 in order to be then folded back as shown in broken lines to hold the bent rod 8 in the beak of the hook 10.

Thus, the tubular element 1 is suspended from the support structure 2 with its rectilinear sections 3 substantially vertical.

In the middle part of the sections 3, shown in detail in FIGS. 5 and 6, support members 12 formed from a sheet metal strip folded in a U shape, are welded to at least some of the sections 3.

Spacers 13 are placed on these support members 12 so as to maintain the spacing between the different sections 3 of the same ply and two neighboring plies at a suitable value (FIG. 2).

The spacers 13 consist of plates arranged between two layers of conductors, these layers forming notches 14 substantially semi-circular allowing the passage of the sections 3.

Organs 12 ′ similar to the organs 12 are arranged above the spacers 13 so as to prevent the latter from tilting under the effect of the air current circulating in the installation.

It is thus found that the spacers 13 are directly carried by the heating elements themselves, which largely solves the problems associated with the elongation of the heating elements under the effect of heat.

Rods 15 also substantially V-shaped are welded at the lower elbows 5 of the tubular member in the same manner as the rods 8 at the upper elbows.

The guide rods 16 are mounted on the rods 15 and comprise at their lower part a washer 17 retained by a pin 18.

Lower spacers 19 are placed on the washers 17 so as to ensure the relative positioning of the lower parts of the tubular element 1.

Supports 20, fixed to the frame of the installation, are arranged below the spacers 19 at a distance such that when the heating elements are extended under the effect of heat - (position indicated in dashed lines in Figure 7) the spacers 19 come to rest on the supports 20, thus reducing the load borne by the heating elements.

When the spacers 19 rest on the supports 20, they nevertheless continue to ensure the relative positioning of the sections 3 because the rod 16 slides in the holes 21 of the spacers thus ensuring the guidance of the elbows 5.

The supporting structure 2 as well as the spacers 13 and 19 are made of any suitable refractory and insulating material.

Various variants and modifications can of course be made to the above description without thereby departing from the scope or the spirit of the invention.

Claims (9)

1. Electric gas heating installation comprising at least one non-insulated electrically conductive tubular element (1), folded back on itself in an accordion manner so as to form a set of plies of substantially parallel conductive sections (3), each of these sections being connected at one of its ends to one of the adjacent sections by a 180 ° elbow (4) and at the other of its ends to the other adjacent section by another 180 ° elbow (5), said tubular element to be suspended from an electrically insulating support structure (2) so that said conductive sections are arranged substantially vertically, the suspension points being arranged at the location of the elbows (4) situated on the upper side of the plies, and of the electrically insulating spacers (13; 19) being arranged between the conductive sections, characterized in that the said spacers are carried by the tubular element. 2. Heating installation according to claim 1, characterized in that the spacers (13) are formed of plates disposed between two plies of sections and are placed on support members (12) mounted on at least some of these sections. 3. Heating installation according to claim 2, characterized in that said plates are notched plates (14) to allow passage of the sections of the tubular element. 4. Heating installation according to any one of claims 1 to 3, characterized in that the spacers (19) - are suspended from said tubular element at the location of the elbows (5) located on the lower side of the sheets. 5. Heating installation according to claim 4, characterized in that supports (20) integral with the support structure are provided below said spacers (19) at a distance such that these other spacers come to rest on the supports when said tubular element elongates under the effect of heat. 6. Heating installation according to claim 5, characterized in that said spacers - (19) are suspended by means of guide rods (16) passing through holes (21) formed in these other spacers which are placed on washers (17) fixed to said rods. 7. Heating installation according to any one of claims 1 to 6, characterized in that, in the area of the elbows the tubular element is flattened in the radial direction. 8. Heating installation according to claim 7, characterized in that, in the area of the elbows, the tubular element has a section having two parts (6) rounded at its ends and a central part (7) of lesser thickness. 9. Heating installation according to any one of claims 1 to 8, characterized in that the suspension points comprise a rod (8, 15) substantially V-shaped, the ends of the branches of which are arranged substantially tangentially and fixed. to the curved part of said elbows.

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