FR2826829A1 - Heat exchanger for motor vehicle air conditioning has tubes containing electrical resistances spaced by separators - Google Patents

Abstract

The heat exchanger for motor vehicle air conditioning has heating bars (10) seated in tubes (18) of conductive material and each having an electrode (14) extending along the tube. An electrical insulation (12) is positioned between the electrode and the tube and electrical resistances (16) are seated in the tubes. The resistances are mutually spaced longitudinally in the tubes using separators (15).

Description

<Desc / Clms Page number 1>

Invention background
The invention relates to a heat exchanger comprising heating bars with resistive elements, in particular, but not exclusively, with resistive elements with positive temperature coefficient (PTC).

 Resistive elements, or resistors, CTP offer an advantage in terms of safety since they allow by self-regulation to avoid any excessive heating.

 For this reason, heat exchangers with PTC resistances are used in certain applications, in particular in air heating and ventilation installations for passenger compartments of motor vehicles.

 PTC resistors are in the form of blocks, or stones, and the production of PTC resistance heat exchangers poses the problem of assembling a fairly large number of stones and their electrical supply.

 A known technique consists in using stones to form heating bars which are introduced into tubes themselves assembled with radiant elements. It is necessary to ensure good electrical contact between the stones and two supply conductors, to insulate between the two conductors, and to ensure that the stones are spaced apart in the tube.

Subject and summary of the invention
The object of the invention is to provide a heat exchanger, or electric radiator, which meets these conditions by using a minimum of parts for the production of the heating bars and by enabling these parts to be manufactured and assembled easily, to reduce manufacturing costs.

 This object is achieved by means of a heat exchanger of the type comprising a plurality of heating bars housed in tubes.

<Desc / Clms Page number 2>

 of electrically conductive material and each comprising an electrode housed longitudinally in the tube, an electrical insulator interposed between the electrode and the internal wall of the tube, a plurality of resistive elements housed in the tube and each having two opposite faces in electrical contact with the inner wall of the tube and the electrode respectively, and means for holding the resistive elements spaced from one another in the longitudinal direction in the tube, a bar in which the locations of the resistive elements are separated from each other in the direction longitudinal by separators formed in one piece with the insulator and / or the electrode.

 Thus, an advantageous characteristic of the invention lies in the fact that the longitudinal holding function of the resistive elements is provided by the insulator and / or by the electrode, making it possible to minimize the number of components of the bar.

 The resistive elements can be in contact with the internal face of the tube either directly or via a shape adaptation element having a face in contact with the resistive elements and an opposite face which matches the shape of the internal face. of the tube and is in contact with it.

 The insulator may be formed by a support piece with a hollow profile extending over the length of the tube, and delimiting a longitudinal passage in which the electrode is disposed.

 According to one embodiment, the separators are formed in one piece with the support piece.

 In particular, the separators may be formed by raised parts projecting from opposite edges of the support piece situated on either side of the longitudinal passage, or by raised parts projecting from a bottom wall of the support. . In the latter case, advantageously, the raised parts pass through holes in the electrode disposed above the bottom wall.

 Alternatively, the support has a bottom wall above which the electrode is arranged and a wall opposite to the bottom wall in which windows are formed delimiting the locations of the resistive elements.

 According to another embodiment, the separators are formed in one piece with the electrode.

<Desc / Clms Page number 3>

 Advantageously, the separators are formed by deformed parts of the electrode.

 The insulator may be formed by a hollow profile support piece extending over the length of the tube and delimiting a longitudinal passage along which the electrode extends, and the deformed parts of the separator electrode protrude in the passage.

 Advantageously then, the support piece has a bottom to which the electrode is connected and the connection between the support piece and the electrode is produced by reliefs projecting from the bottom of the support piece and penetrating into recesses formed by deformed parts of the electrode.

 According to yet another embodiment, the electrode is a strip deformed so as to form corrugations which delimit locations for the resistive elements alternately on one side and the other of the electrode, and an insulating layer is interposed between each part of the surface of the electrode opposite to that in contact with a resistive element and the adjacent wall of the tube.

 The insulating layer is preferably a coating applied locally to the electrode.

 The invention also relates to a heat exchanger comprising several heating bars as defined above, assembled with radiant elements.

Brief description of the drawings
The invention will be better understood on reading the description given below, by way of indication but not limitation, with reference to the appended drawings in which: - Figure 1 is a partially cut away perspective view of a heating rod, inserted in a tube, according to an embodiment of the invention; - Figure 2 is a longitudinal longitudinal sectional view of the bar of Figure 1; - Figure 3 is a cross-sectional view along the plane HNi) of Figure 2;

<Desc / Clms Page number 4>

 - Figures 4 and 5 are cross-sectional views similar to that of Figure 3, showing alternative embodiments of the bar; - Figure 6 is a perspective view similar to that of Figure 1 showing another alternative embodiment of the insulating support; FIG 7 is a perspective view similar to that of Figure 1 showing yet another alternative embodiment of the insulating support; - Figure 8 is a partially broken away perspective view showing an alternative embodiment of the heating rod of Figure 1, inserted in a tube; - Figure 9 is a partial perspective view showing the insulating support and the electrode of the bar of Figure 8, before mutual assembly; FIG. 10 is a partial perspective view showing an insulating support and an electrode before mutual assembly, according to an alternative embodiment of the bar of FIG. 8.

- Figure 11 is a longitudinal longitudinal sectional view showing a heating rod formed with the insulating support and the electrode of Figure 10; - Figure 12 is a partially cutaway perspective view of a heating rod inserted in a tube according to another embodiment of the invention; - Figure 13 is a longitudinal longitudinal sectional view of the bar of Figure 12; - Figure 14 is a cross-sectional view along the plane XIV-XIV of Figure 13; - Figure 15 is a perspective view showing an alternative embodiment of the electrode of the heating bar of the figures
12 to 14; - Figure 16 is a longitudinal sectional view of a heating rod incorporating the electrode of Figure 15; - Figure 17 is a partial perspective view of an insulating support according to an alternative embodiment of the bar of Figures 12 to 14;

<Desc / Clms Page number 5>

 - Figure 18 is a longitudinal sectional view of the bar incorporating the insulating support of Figure 17; - Figure 19 is a longitudinal sectional view of a heating rod inserted in a tube according to yet another embodiment of the invention; - Figure 20 is a cross-sectional view along the plane XX-XX of Figure 19; - Figure 21 is a partial perspective view of a heat exchanger comprising heating rods inserted in tubes assembled with fins; - Figure 22 is a partial perspective view of a heat exchanger comprising heating rods inserted in tubes assembled with spacers; and FIG. 23 is a partial perspective view showing an alternative embodiment of tubes receiving heating bars for an exchanger such as that of FIG. 22.

Detailed description of embodiments
In the following description, several embodiments of heating bars inserted in tubes will be described.

The insertion of the heating bars in the tubes can be carried out before mounting the tubes in an exchanger. The tube + heating rod assembly then constitutes a manipulable exchanger component. The insertion of the heating bars in the tubes can be carried out after prior assembly of the tubes alone in an exchanger.

 Figures 1 to 3 illustrate a first embodiment of a heating rod according to the invention.

 The bar 10 is constituted by an insulating support 12, of elongated shape, an electrode 14 extending in a longitudinal passage 11 of the support 12, and resistive elements 16 spaced from one another along the insulating support 12. The insulating support 12 is housed with the electrode 14 and the resistive elements 16 inside a tube 18.

 The insulating support 12 in this example has a shape of a hollow section with rectangular section. It is made of plastic,

<Desc / Clms Page number 6>

telle que PEI, polysulfane ou PTFE, par exemple par moulage. Le support isolant 12 comprend une paroi dite de fond 12a, deux parois , deux parois latérales opposées 12b, 12cet une paroi dite supérieure 12d opposées à la paroi de fond. Le passage longitudinal 11 qui s'étend le long du support 12 est ouvert à une extrémité et peut être fermé par une

paroi 12e à l'autre extrémité.

such as PEI, polysulfane or PTFE, for example by molding. The insulating support 12 comprises a so-called bottom wall 12a, two walls, two opposite side walls 12b, 12c and a so-called upper wall 12d opposite the bottom wall. The longitudinal passage 11 which extends along the support 12 is open at one end and can be closed by a

12th wall at the other end.

 The electrode 14 is a strip of electrically conductive material, for example a metallic strip of copper, aluminum or stainless steel which is disposed in the passage 11, all along the latter, in contact with the face internal of the bottom wall 12a.

 The resistive elements 16 are in the form of substantially parallelepipedic blocks. They can be made of materials with PTC resistance or not, depending on the application envisaged. The resistive elements 16 are arranged along the insulating support 12 and are kept spaced from one another by introduction into apertures or windows 17 of suitable shape formed in the wall 12d of the insulating support 12.

de la face externe de la paroi 12d. The resistive elements 16 have a main face 16a in contact with the electrode 14. They protrude slightly from the insulating support 12 through the windows 17 so that their main face 16b opposite the face 16a is located at a slightly higher level. to the one

of the external face of the wall 12d.

 The parts 15 of the insulating support which form the transverse sides of the windows 17 constitute separators for holding the resistive elements 16 in the longitudinal direction.

côtés longitudinaux 17E, 17c des fenêtres 17. L'insertion des éléments côtés longitudinaux 17b résistifs 16 dans les fenêtres pourra être réalisée au moins légèrement à force, ce qui permet de solidariser les éléments résistifs avec le support isolant et de former un barreau chauffant aisément manipulable lorsqu'il doit être introduit dans un tube déjà en place dans un échangeur. On pourra à cet effet conférer à l'un et/ou l'autre des côtés 17b, 17c une forme bombée comme montré par la figure 1. The lateral support of the resistive elements is ensured by the

longitudinal sides 17E, 17c of the windows 17. The insertion of the resistive longitudinal side elements 17b 16 into the windows can be carried out at least slightly by force, which makes it possible to secure the resistive elements with the insulating support and to form a heating bar easily manipulable when it must be introduced into a tube already in place in an exchanger. To this end, one and / or the other of the sides 17b, 17c can be given a domed shape as shown in FIG. 1.

 The tube 18 is made of an electrically conductive material, for example a metal such as aluminum. It is flattened,

<Desc / Clms Page number 7>

 so as to have a flat internal face 18b at the level of contact with the faces 16b of the resistive elements 16.

 When the internal wall of the tube 18 does not offer sufficient flatness, an additional adapter element 18 ′ can be interposed between the internal face 18b of the tube and the resistive elements 16, as shown in FIG. 4.

 The element 18 is formed by an electric and thermal conductive bar, for example made of aluminum having a face which matches the shape of the internal face 18b of the tube and an opposite planar face applied to the resistive elements.

 The insertion of the insulating support 12 carrying the electrode 14 and the resistive elements 16 can be carried out slightly by force in the tube 18 in order to ensure good electrical contact between the tube and the resistive elements.

 It will also be possible to provide the external face of the bottom wall 12a with ribs 19 in the form of wings which are elastically deformed during insertion into the tube 18 and thus exert a restoring force ensuring good electrical contact between the resistive elements. 16 and the tube 18 and between the resistive elements 16 and the electrode 14.

 The electrode 14 and the tube 18, when connected to the terminals of an electric voltage source, supply the resistive elements in parallel. It will be noted that the bar 10 can be pre-assembled and tested before its subsequent integration into a heat exchanger.

aplati 18, notamment au niveau des parois latérales 12 12ç, qui , 12c, qui épousent la forme des parties du tube 18 raccordant ses deux faces planes. Le contact électrique entre les éléments résistifs 16 et la paroi interne du tube 18 pourra être assuré par l'intermédiaire d'un élément d'adaptation de forme tel que l'élément 18'de la figure 4. FIG. 5 shows an alternative embodiment according to which the insulating support 12 has a shape corresponding to that of the tube

flattened 18, in particular at the level of the side walls 12 12c, which, 12c, which conform to the shape of the parts of the tube 18 connecting its two flat faces. The electrical contact between the resistive elements 16 and the internal wall of the tube 18 can be ensured by means of a shape adaptation element such as the element 18 ′ in FIG. 4.

 In this example, the contact between the resistive elements 16 and the tube 18 is also ensured by a slightly force fitting in the tube 18, under the assistance of ribs 19 formed on the underside of the insulating support.

<Desc / Clms Page number 8>

mais par des reliefs 1 5b mais par des re ! iefs 15b, 15c faisant saillie des faces internes des parois latérales 1212 et 12c du support isolant et définissant les logements des éléments résistifs.

Figures 6 and 7 illustrate alternative embodiments of the insulating support 12 of Figures 1 to 3. According to these variants, the maintenance of the resistive elements 16 in the longitudinal direction is ensured not by crosspieces 15 extending from one edge to the other of the insulating support,

but by reliefs 1 5b but by re! iefs 15b, 15c projecting from the internal faces of the side walls 1212 and 12c of the insulating support and defining the housings of the resistive elements.

The reliefs 15b The re! iefs 15b, 15c may be ribs extending over the entire height of the longitudinal passage 11, or pins extending over only part of the height, as illustrated in FIGS. 6 and 7.

In addition, the reliefs 15b In addition, the reliefs 15b, 15c can be arranged facing each other, as shown in FIG. 6, or simply in staggered rows, as shown in FIG. 7.

 The embodiment illustrated by Figures 8 and 9 differs from that of Figures 1 to 3, in that the maintenance of the resistive elements 16 is ensured in the longitudinal direction in the passage 11 by pins 15a which project from the wall bottom 12a of the insulating support, through holes 14a formed in the electrode 14.

des rebords 12'd des rebords 12'd, 12"d qui s'étendent le long des parois latérales 12b, 12c, conférant au support isolant une forme de profilé à section en C. In addition, the upper wall of the insulating support is limited to

rims 12'd rims 12'd, 12 "d which extend along the side walls 12b, 12c, giving the insulating support a shape of section with a C section.

The flanges 12'd, 12 "d prevent the coming of the electrode 14 in accidental contact with the internal wall of the tube 18. They also provide lateral support for the resistive elements.

 In the variant illustrated in FIGS. 10 and 11, the resistive elements 16 are held in the longitudinal direction in the passage 11 is also ensured by pins 15a which project from the bottom wall 12a of the insulating support, through holes 14a formed in the electrode 14. However, the pins 15a also ensure the fixing of the electrode 14 on the bottom 12a of the insulating support 12. Consequently, the upper wall of the insulating support can be eliminated so that the insulating support 12 has a U section.

 This fixing is provided by the part 15 ′ of the pins which protrudes above the electrode 14 and which has a diameter slightly greater than that of the holes 14 a.

<Desc / Clms Page number 9>

présentant les trous 14a peut être engagée à force sur les picots 15a qui forment des clips de fixation de l'électrode sur le fond 12a. FIG. 11 shows the insulating support 12 with the pins 15a with bulged head 15'a projecting from the bottom 12a. The electrode 14

having the holes 14a can be forcibly engaged on the pins 15a which form clips for fixing the electrode to the bottom 12a.

 Alternatively, the electrode 14 can be placed on the insulating support 12 provided with straight pins, these then being heated to form the bulged heads 15 ′ locking the electrode on the insulating support.

 The establishment of the electrode 14 could also be carried out after heating the insulating support in order to soften the material of the pins 15, the electrode then being locked on the bottom 12a by the heads 15a of the pins, after cooling of the material.

 Figures 12 to 14 illustrate another embodiment of a heating bar according to the invention in which the resistive elements are held by separators formed in one piece in the electrode.

 FIGS. 12 to 14 show a bar 110 constituted by an insulating support 112 of elongated shape, an electrode 114 extending in a longitudinal passage 111 of the support 112, resistive elements 116 spaced from one another along the insulating support 112. The insulating support 112 is housed with the electrode 114 and the resistive elements 116 in a tube 118. The materials constituting the elements forming the bar 110 may be identical to those of the elements forming the bar 10 of FIGS. 1 to 3.

profilé à section en C avec une paroi de fond 112fl, deux parois , deux parois latérales 112t, 1125 et une paroi supérieure limitée à deux rebords longitudinaux 112'd, 112"d. le long des parois latérales. La présence

des rebords 112'~d é 1 des rebords 112'd, 112"d pourra être omise. Le support 112 délimite le passage 111 à section rectangulaire. The insulating support 112 in this example has the form of a

C-shaped section with a bottom wall 112fl, two walls, two side walls 112t, 1125 and an upper wall limited to two longitudinal edges 112'd, 112 "d. along the side walls. The presence

edges 112 '~ d 1 of edges 112'd, 112 "d may be omitted. The support 112 delimits the passage 111 with rectangular section.

 The electrode 114 consists of a metal strip, for example of copper, aluminum or stainless steel in which reliefs 115 have been formed at regular intervals, for example by stamping. The reliefs 115 form studs located in the central part of the electrode 114.

<Desc / Clms Page number 10>

éventuels 112'çL 112" g contribuent au maintien latéral des éléments éventuels 112'd résistifs 116. The pins 115 delimit the locations of the resistive elements in the longitudinal direction in the passage 111. The flanges

possible 112'çL 112 "g contribute to the lateral maintenance of the possible elements 112'd resistive 116.

, 112"d. rebords 112'd, 112"d. The resistive elements 116 have a main face 116a in contact with the electrode 114, between the studs 115, and an opposite main face 116b which protrudes slightly above the

, 112 "d. Ledges 112'd, 112" d.

The insulating support 112, with the electrode 114 and the resistive elements 116 is fitted lightly into the tube 118 of flattened shape. Deformable ribs 119 can be formed on the external face of the bottom wall 112a of the insulating element 112 so, after deformation caused by insertion into the tube, exert a force for applying the faces 116a and 116b of the resistive elements against the electrode 114 and the internal wall of the tube 118.

The flanges 112'd The flanges 1121çL 112 "g of the insulating support prevent any accidental contact between the electrode 114 and the tube 118.

 FIGS. 15 and 16 illustrate an alternative embodiment of the heating rod of FIGS. 12 to 14, a variant according to which the separators of the resistive elements in the longitudinal direction of the passage 111 are reliefs 117 obtained by localized folding of the electrode 114.

, 112"d. les rebords 112'd, 112"d. The folds 117 which extend transversely relative to the strip 114 can be cut at their ends 117b, 117e in order to allow the engagement of the electrode 114 in the passage 111, with the folds 117 possibly located at least partially between

, 112 "d. Ledges 112'd, 112" d.

 The forming of the metal strip 114 to produce the folds 117 can easily be carried out with a wheel.

 It will be noted that in the embodiments of FIGS. 12 to 161, the insulating support (112) is in the form of a profile which can be produced by extrusion of plastic. This makes it possible to cut the profile to the desired lengths after extrusion, and to reduce costs in comparison with molding which requires different tools adapted to the lengths to be produced.

<Desc / Clms Page number 11>

 In addition, the extrusion can be carried out directly around a metal strip in which separating reliefs such as 115,117 have been previously produced. This allows, after cutting to the desired length, to directly obtain an insulating support and a pre-assembled electrode, and to limit the clearances between these two elements.

 Figures 17 and 18 illustrate an alternative embodiment of the heating rod of Figures 12 to 14. According to this alternative, reliefs 115 'are formed on the internal face of the bottom wall 112a of the insulating support which engage in the corresponding recesses to the stamped parts 115 of the electrode 114.

 Advantageously, the insulating support is heated before the electrode 114 is put in place in order to soften the material of the reliefs 115 ′. The electrode 114 is then put in place with the pins 115 fitting onto the reliefs 115 ′. After cooling, a connection is obtained between the insulating support 112 and the electrode 114.

 Such a variant could also be adapted to the embodiment of FIGS. 15 and 16, by forming on the internal face of the bottom wall 112a reliefs corresponding to the folds 117 of the electrode 114.

 Figures 19 and 20 illustrate yet another embodiment of a heating rod 210, according to the invention.

 The bar 210 comprises an electrode 214 of corrugated shape, with rectangular undulations, and of resistive elements 216 distributed along the electrode 214. A suitable tube 218 contains the resistive elements and the electrode 214 of the electrical insulation layers being interposed between the electrode 214 and the internal wall of the tube 218.

l'électrode 214 présente des tronçons 214a, 214b qui s'appuient sur tes , 214b qui s'appuient sur les faces internes opposées 218. 9., 21812 du tube aplati 218 avec , 218b du tube aplati 218 avec interposition de couches isolantes 212a, 212b. The electrode 214 is formed by a metal strip, for example made of copper or stainless steel deformed by bending. So,

the electrode 214 has sections 214a, 214b which are supported on the, 214b which are supported on the opposite internal faces 218. 9., 21812 of the flattened tube 218 with, 218b of the flattened tube 218 with interposition of insulating layers 212a , 212b.

, 212b.

 Each face of the sections 214a, 214b not turned towards the internal wall of the tube 218 is in contact with a main face of a resistive element 216, the other main face of this resistive element being in contact with the adjacent internal wall of the tube, is

<Desc / Clms Page number 12>

 directly, either through a shape adaptation element as in the embodiment of FIG. 4.

Thus, the resistive elements 216 are located alternately on one side and the other of the electrode 214 and are separated from each other in the longitudinal direction of the bar 210 by the sections 214c of the electrode 214 which connect the sections 214a and 214b. The insulating layers formed on the sections 214a and 214b can be extended so as to also cover at least part of the two faces of the separators 214c.

The insulating layers 212a The insulating layers 212a, 212b can be formed by a varnish or a paint deposited on the metal strip constituting the electrode.

munie de couches d'isolation 212a munie de couches d'iso ! ation 212a, 212b alternativement sur ses deux faces et complétée par les éléments résistifs 216, un bon contact électrique entre le tube et les éléments résistifs et entre ceux-ci et l'électrode peut être obtenu par écrasement du tube 218 (flèches F de la figure 20). After insertion into the tube 218 of the corrugated electrode 214,

with layers of insulation 212a with layers of iso! ation 212a, 212b alternately on its two faces and supplemented by the resistive elements 216, good electrical contact between the tube and the resistive elements and between these and the electrode can be obtained by crushing the tube 218 (arrows F of the figure 20).

 In all the embodiments described above, there is an important characteristic of the invention which consists in the production of the separators between resistive elements in a single piece with the insulation and / or with the electrode.

 The number of constituent elements of the heating rod is therefore reduced, which simplifies the supply, storage and assembly of these elements and contributes to the reduction of the manufacturing cost of the heating rods and to their reliability.

 FIG. 21 illustrates an embodiment of a heat exchanger 120 into which can be inserted heating bars as described above, for example bars such as the bar 110 of FIG. 12.

 In this example, tubes 118 which are parallel to each other are preassembled with radiant elements in the form of metal fins 122. The tubes pass through openings formed in the fins, which are arranged perpendicular to the tubes and are regularly spaced from one another. The bars 110 are then inserted into the tubes 118 in the longitudinal direction.

<Desc / Clms Page number 13>

 The tubes and fins are brought to a reference potential (for example ground) while the electrodes of the heating bars are connected in common to a positive terminal of a source of electric voltage. The heat produced by the Joule effect by the resistive elements of the heating bars is taken up by the air passing through the exchanger between the tubes and the fins.

 FIG. 22 illustrates another embodiment of a heat exchanger 130 in which heating bars as described above can be mounted, for example bars such as the bar 110 of FIG. 12.

 In this example, tubes 118 flattened parallel to each other are stacked alternately with radiant elements 132 forming spacers. The spacers are for example constituted by corrugated metal strips. The assembly of tubes 118 and spacers 132 can be achieved by mounting the assembly in a frame. You can also connect the tubes to the spacers by brazing or welding. The bars 110 are then inserted longitudinally into the tubes 118.

 The electrodes of the bars 110 are connected in common to a terminal of an electrical voltage source, the other terminal (ground) of which is connected to the spacers 132 and tubes 118.

 FIG. 23 illustrates an alternative embodiment of the exchanger 130 of FIG. 22. According to this alternative, the tubes 118 ′ are flattened tubes with U-section, that is to say open laterally.

The invention of the heating bars can then be carried out laterally, and not longitudinally, in the tubes 118 ', as shown in the figure, which simplifies the mounting of the bars. Note that the side wall of the insulating support, on the open side of the tube
118 ', protects the resistive elements against external aggressions, in particular corrosion. It would be the same with the bars 10 of Figures 1 to 11. However, a closure of the open sides of the tubes
118 'could be considered.

Claims (17)

1. Heat exchanger comprising a plurality of heating bars (10; 110; 210) housed in tubes (18; 118; 218) of electrically conductive material and each comprising an electrode (14; 114; 214) housed longitudinally in the tube,

 an electrical insulator (12; 112; 212; 212Q) interposed between,; 21212) interposed between the electrode and the internal wall of the tube, a plurality of resistive elements (16; 116; 216) housed in the tube and each having two opposite faces in electrical contact with the internal wall of the tube and the electrode, and means for holding the resistive elements spaced from each other in the longitudinal direction in the tube, characterized in that the locations of the resistive elements (16; 116; 216) are separated from each other in the longitudinal direction by separators formed in one piece with the insulator (12; 112) and / or the electrode (14; 114; 214).  2. Heat exchanger according to claim 1, characterized in that the resistive elements (16) are in electrical contact with the tube (18) via a shape adaptation element (18 ') having a face in contact with the resistive elements and another face which matches the shape of the internal wall (18b) of the tube and which is in contact with the latter.  3. Exchanger according to any one of claims 1 and 2, characterized in that the insulator is formed by a support piece (12; 112) with hollow profile extending over the length of the tube (18; 118), and delimiting a longitudinal passage (11; 111) in which the electrode is arranged.  4. Exchanger according to claim 3, characterized in that the separators (15; 15a; 15b; 15c) are formed in one piece with the support piece.  5. Exchanger according to claim 4, characterized in that the separators are formed by raised parts (15b; 15c) projecting from opposite edges of the support piece (12) located on either side of the longitudinal passage ( 11). <Desc / CRUD Page number 15>  6. Exchanger according to claim 4, characterized in that the separators are formed by raised parts (15a) projecting from a bottom wall of the support (12).  7. Exchanger according to claim 6, characterized in that

 the raised parts (15g) pass through holes (14a) of the raised parts (15a the electrode (14) disposed above the bottom wall.  8. Exchanger according to claim 3, characterized in that the support (12) has a bottom wall (12a) above which the electrode (14) is disposed and a wall zu opposite to the bottom wall in which windows (17) are formed delimiting the locations of the resistive elements (16).  9. Exchanger according to any one of claims 1 and 2, characterized in that the separators (115; 117; 2149 are formed in one piece with the electrode (114; 214).  10. Exchanger according to claim 9, characterized in that the separators (115; 117; 2149 are constituted by deformed parts of the electrode (114; 214).  11. Exchanger according to claim 10, characterized in that the insulation is formed by a support piece (112) with hollow profile extending over the length of the tube (118) and delimiting a longitudinal passage (111) along which extends the electrode (114), and the deformed portions of the separator electrode (115; 117) protrude into the passage.  12. Exchanger according to claim 11, characterized in that the support part (112) has a bottom to which the electrode (114) is connected, and the connection between the support part and the electrode is formed by reliefs ( 115 ') projecting from the bottom of the support piece and penetrating into recesses (115) formed by deformed parts of the electrode.  13. Exchanger according to any one of claims 9 and 10, characterized in that the electrode (214) is a strip deformed so as to form corrugations which delimit locations for the resistive elements (216) alternately on one side and on the other

 of the electrode, and a layer (212a of the electrode, and an insulating layer (212a 212b) is interposed between each surface part of the electrode opposite to that in contact with a resistive element and the adjacent wall of the tube. <Desc / Clms Page number 16>

14. Exchanger according to claim 13, characterized in that the insulating layer (212 21212) is a coating applied as the insulating layer (212a locally on the electrode (214).  15. Exchanger (120; 130) according to any one of claims 1 to 14, characterized in that the tubes (118; 118 ') containing the heating bars (110) are assembled with radiant elements (122; 132).  16. Exchanger according to any one of claims 1 to 15, characterized in that the resistive elements (16; 116; 216) of the bars are resistors with a positive temperature coefficient.  17. A method of manufacturing a heating rod for a heat exchanger according to claim 10, characterized in that it comprises the steps of deformation of a metal strip to produce said separators (115,117), and forming a profile (112) by extruding plastic material around the deformed metal strip, so that an assembly comprising an insulating support and a pre-assembled electrode can be obtained.