Thermal heater for heat transfer fluid with electric rods.

Abstract

The present invention relates to a thermal heater (1) of a heat transfer fluid, comprising a closed enclosure (11) including a cylindrical tube (10) having an upstream end (12) and a downstream end (13), at least one bundle (2) of a plurality of electric heating rods (20) for this fluid, these rods (20) being arranged axially inside said tube (10), an inlet conduit (4) and an outlet conduit (8) of the heat transfer fluid into and out of the enclosure (11). This heater is remarkable in that it includes an annular chamber (3) for introducing the heat transfer fluid into the enclosure, arranged around the tube (10) from its upstream end (12) and along part of its length, in that the inlet conduit (4) opens into this introduction chamber (3) and in that the upstream end (12) of the tube (10) of the enclosure includes several introduction ports (5) for the heat transfer fluid, distributed around the periphery of the tube (10).Figure for the summary: Fig. 3.

Description

Title of the invention: Thermal heater for heat transfer fluid with electric rods. FIELD OF INVENTION

[0001] The invention is in the field of energy storage in thermal form.

[0002] The present invention relates more particularly to a thermal heater of a heat transfer fluid using a bundle of electric rods. STATE OF THE ART

[0003] A number of installations produce electricity intermittently, such as photovoltaic panels, heliostat fields or wind turbines.

[0004] It is therefore desirable to be able to store the electrical energy produced at a given moment by these installations, in order to use it later at a time when there is no sun or wind, for example, but when the demand for electricity is high.

[0005] To this end, prior art already exists thermal heaters which allow a heat transfer fluid, generally a molten salt, to be heated using surplus electricity produced by the aforementioned installations, in order to constitute energy storage in thermal form. This thermal energy is subsequently used to produce electricity, for example using a standard steam turbine cycle and an electricity generator.

[0006] The attached [Fig. 1] illustrates an example of a first embodiment of a thermal heater, known from the prior art.

[0007] As can be seen in this figure, such a heater comprises a cylindrical enclosure A, inside which is arranged a bundle of axial electric rods B. These electric rods extend from one end of the enclosure A to the other. A radial inlet tube C and a radial outlet tube D are provided at each end of the enclosure A for respectively introducing into it or extracting from it the fluid (molten salt) to be heated.

[0008] Each rod B is a tube which internally contains an electrical resistance E and this resistance is supplied with electricity from a power supply unit F. Each rod B thus allows the salt circulating in the heater to be heated by Joule effect.

[0009] However, if the heater must allow the salt to be heated to a specific temperature at its outlet D, the temperature reached locally by the molten salt in enclosure A must also not exceed a certain threshold. Indeed, beyond this temperature threshold, the chemical properties of the salt are likely to degrade, as well as its performance.

[0010] However, when electric rods are used to produce thermal energy by Joule effect in a closed enclosure, if this energy is not uniformly evacuated, that is to say uniformly transferred to the fluid (molten salt) which circulates in this enclosure, then the temperature of this fluid can locally reach very high values, which leads to its irreversible degradation.

[0011] By way of purely illustrative example, for a nitrate salt used in a heater and composed of 60% NaNO and 40% KNC1, it must be brought from a low temperature (about 300°C) to a high temperature (about 580°C), but without exceeding the threshold of 600°C beyond which this salt degrades irreversibly.

[0012] In a heater with the geometry shown in [Fig. 1], a local inhomogeneity in the temperature of the molten salts is observed. Indeed, the salts entering through tube C directly impact the rods B and the electrical resistors E contained within them. These salts tend to flow more rapidly towards the interior of the heater (arrows Fl) and to stagnate in the heater zone referenced A1, located upstream of the inlet tube C. The same stagnation phenomenon is observed in the heater zone referenced A2, located downstream of the outlet tube D.

[0013] In these two stagnation zones, we observe a problem of overheating of the molten salts, due to the fact that the salts remain longer in contact with the electric rods B.

[0014] Furthermore, heat transfer from the rods B to the salts occurs more efficiently where the salts flow more rapidly around the rods than where they flow more slowly, because the heat transfer coefficient is related to the flow velocity. Therefore, in both stagnation zones A1 and A2, there is also a risk of overheating of the electric rods, which can lead to their deterioration.

[0015] In order to remedy this problem, a thermal heater illustrated in the attached [Fig.2] is also known in the prior art.

[0016] This heater differs from the previous one in that the electric heating resistances E do not extend to both ends of each electric rod B. As a result, in the heater area referenced A3, which includes the area A1 and the area opposite the inlet tube C, and in the heater area referenced A4, which includes the area A2 and the area opposite the outlet tube D, the salts are not heated.

[0017] While this solution resolves the aforementioned problems of overheating the salts and the canes, it has the disadvantage of unnecessarily increasing the overall length of the A heater is used to ensure a uniform heating temperature at the outlet. Each zone, A3 and A4, is approximately 1 meter long.

[0018] Finally, in the two aforementioned heaters, there is a problem of vibration of the rods B, due to the fact that the molten salts introduced via the inlet tube C directly impact the rods. There is therefore an additional risk of damage to the rods B. Description of the invention

[0019] The invention aims to solve the aforementioned problems and, in particular, to provide a thermal heater with an electric rod bundle, which allows:

[0020] - to reduce or eliminate the phenomenon of hot spots and therefore inhomogeneity in the heating of the heat transfer fluid (particularly molten salts) to be heated,

[0021] - to respect the temperature thresholds not to be exceeded to avoid degradation of this fluid,

[0022] - to obtain a more homogeneous and reproducible temperature of the outlet fluid of the heater,

[0023] - and to eliminate the problem of vibration of the rods, linked to the introduction lateral movement of a high-speed fluid.

[0024] The invention also aims to provide a heater that may also:

[0025] - to limit the length of the rod not having electrical resistance,

[0026] - to minimize the overall length of the heater for the same power thermal and therefore its footprint,

[0027] - and to be able to connect several heaters if necessary.

[0028] To this end, the invention relates to a thermal heater for a heat transfer fluid, in particular a molten salt, comprising:

[0029] - a closed enclosure comprising a cylindrical tube having an upstream end and a downstream end relative to the direction of flow of the heat transfer fluid inside the enclosure,

[0030] - at least one bundle of a plurality of electric heating rods of this fluid, these rods being arranged axially inside said tube of the enclosure,

[0031] - an inlet conduit for the heat transfer fluid into the enclosure and an outlet conduit of this heat transfer fluid outside the enclosure.

[0032] According to the invention, this heater comprises an annular chamber for introducing the heat transfer fluid into the enclosure, this annular introduction chamber being arranged around the tube of the enclosure and coaxially therewith and extending from the upstream end of the tube over a portion of its length, The inlet duct is connected to this annular introduction chamber and opens into the inside of it, and the upstream end of the enclosure tube includes several orifices for the introduction of the heat transfer fluid, these introduction orifices being distributed around the periphery of the tube and providing fluidic communication between the annular introduction chamber and the inside of the enclosure.

[0033] Thanks to these features of the invention, the heat transfer fluid enters via the inlet duct, then circulates in the annular fluid introduction chamber before entering the enclosure, but at the end of the enclosure and while being distributed around its periphery via the fluid introduction orifices, instead of entering the enclosure at a single lateral point. This results in better optimization of the fluid heating and eliminates any fluid stagnation zones.

[0034] Moreover, unlike the prior art where there was a single incoming jet of fluid which struck certain heating rods and subjected them to strong vibrations, having fluid inlets distributed around the periphery of the tube makes it possible to reduce or eliminate this vibration of the rods.

[0035] According to other advantageous and non-limiting features of the invention, taken alone or in combination:

[0036] - the heater includes an annular chamber for discharging the heat transfer fluid outside the enclosure, this annular evacuation chamber being arranged around the enclosure tube and coaxially to it and extending from the downstream end of the tube over part of its length, the outlet duct is connected to this annular evacuation chamber and opens inside it, and the downstream end of the enclosure tube includes several evacuation ports for the heat transfer fluid, these evacuation ports being distributed around the periphery of the tube and putting the inside of the enclosure and the annular evacuation chamber into fluidic communication;

[0037] - each electric rod of the beam or at least one of the beams comprises an electrical resistance disposed inside a tube longer than said electrical resistance, so as to form at the upstream end of said tube an area free of electrical resistance, called upstream non-heating zone and the introduction ports of the heat transfer fluid are formed in the part of the tube of the enclosure located around the upstream non-heating zones of the electrical rods of the bundle of electrical rods;

[0038] - each electric rod of the beam or at least one of the beams comprises an electrical resistance disposed inside a tube longer than said electrical resistance, so as to form at the downstream end of said tube a zone free of electrical resistance, called the downstream non-heating zone, and the heat transfer fluid discharge ports are formed in the part of the tube of the enclosure located around the downstream non-heating zones of the electric rods in the electric rod bundle;

[0039] - the heater includes, inside the tube of the enclosure, a so-called "upstream" beam » of electric rods and a so-called "downstream" bundle of electric rods, arranged end to end axially in the tube so that the downstream end of the upstream bundle is located close to the upstream end of the downstream bundle, the electric rods of the upstream bundle include an upstream non-heating zone and the electric rods of the downstream bundle include a downstream non-heating zone;

[0040] - the inlet conduit opens radially or substantially radially into the annular inlet chamber and / or in that the outlet conduit opens radially or substantially radially into the annular outlet chamber;

[0041] - the fluid inlet ports and / or the fluid outlet ports are aligned in the form of at least one row of orifices extending in a plane perpendicular to the longitudinal axis of the tube, preferably in the form of at least two parallel rows of orifices;

[0042] - the distribution density of the fluid introduction orifices is greater in the part of the tube of the enclosure located opposite to that where the inlet conduit opens and / or or the distribution density of the fluid discharge orifices is greater in the part of the tube of the enclosure located opposite to that where the outlet conduit opens;

[0043] - the fluid inlet ports and / or the fluid outlet ports are of circular, semi-circular, square or rectangular shape;

[0044] - the fluid inlet ports are arranged in the form of at least two parallel rows of orifices and in that each fluid inlet orifice of a row located further downstream has an area less than ...

[0045] - the heater comprises a plurality of deflectors arranged alternately at inside the tube of the enclosure, these deflectors extend perpendicularly to the axis of the tube to ensure a zig-zag circulation of the heat transfer fluid inside the enclosure. DESCRIPTION OF THE FIGURES

[0046] Other features, objectives and advantages of the invention will become apparent from the following description, which is purely illustrative and not limiting, and which should be read in conjunction with the accompanying drawings on which:

[0047] [Fig. 1] is a diagram representing in longitudinal section an example of an embodiment of a thermal heater known from the prior art.

[0048] [Fig.2] is a diagram representing in longitudinal section another example of the realization of a thermal heater known from the prior art.

[0049] [Fig.3] is a diagram representing in longitudinal section the thermal heater according to the invention.

[0050] [Fig.4] is a perspective view of a portion of the thermal heater according to the invention.

[0051] [Fig.5] is a partial cross-sectional view of the upstream end of the thermal heater according to the invention.

[0052] [Fig.6] is a diagram representing a first possible embodiment of the inlet or outlet ports of the heat transfer fluid.

[0053] [Fig.7] is a diagram representing a second possible embodiment of the inlet or outlet ports of the heat transfer fluid.

[0054] [Fig.8] is a diagram representing a third possible embodiment of the inlet or outlet ports of the heat transfer fluid.

[0055] [Fig.9] is a diagram representing a fourth possible embodiment of the inlet or outlet ports of the heat transfer fluid.

[0056] [Fig. 10] is a perspective and partial cross-sectional view of the heater of the invention showing the positioning of the deflectors.

[0057] [Fig. 11] is a perspective and partial sectional view of the heater of the invention showing the positioning of the deflectors, the section being made along a plane perpendicular to that of [Fig. 10].

[0058] [Fig. 12] is a perspective view of a heater comprising two bundles of electric rods, arranged at each end of the heater. DETAILED DESCRIPTION OF THE INVENTION.

[0059] The thermal heater 1 of a heat transfer fluid according to the invention will now be described in connection with Figures 3 to 5.

[0060] The heat transfer fluid to be heated is, in particular, a molten salt, which allows energy to be stored in thermal form at a sufficiently high temperature to be used subsequently in the production of electrical energy. As a purely illustrative example, a salt composed of 60% NaNO₃ and 40% KNC₂ may be cited. Other molten salts or other heat transfer fluids may also be used.

[0061] This heater 1 comprises a cylindrical tube 10, with central longitudinal axis X-X'.

[0062] A bundle 2 of several electric heating rods 20 for the heat transfer fluid is arranged inside the tube 10, so that its rods 20 extend axially inside this tube, i.e. parallel to the axis X-X'.

[0063] Each rod 20 includes a tube 21, inside which is arranged an axial electrical resistance 22, the latter being supplied with electricity from an electrical connection box 23.

[0064] The rods 20 allow the heat transfer fluid circulating in the tube 10 to be heated by Joule effect.

[0065] Preferably, each tube 21 is longer than the electrical resistance 22, so as to form at the upstream end of said tube 21, a zone free of electrical resistance, called the "upstream non-heating zone" 211.

[0066] Preferably also, each tube 21 is longer than the electrical resistance 22, so as to form at the downstream end of said tube 21, a zone free of electrical resistance, called the "downstream non-heating zone" 212.

[0067] The tube 10, closed at both ends as will be described later, constitutes a closed cylindrical enclosure 11, inside which the heat transfer fluid flows from upstream to downstream, that is to say from left to right in figures 3 and 4.

[0068] In the remainder of the description and claims, the terms "upstream" and "downstream" are to be taken into consideration with respect to the direction of flow of the heat transfer fluid inside the enclosure 11.

[0069] The tube 10 comprises an upstream end 12 and a downstream end 13.

[0070] An annular chamber 3 for introducing the heat transfer fluid into the enclosure 11 is arranged around the tube 10 of the enclosure and coaxially to it. The axis X-X' also constitutes the central axis of the chamber 3. This introduction chamber 3 extends from the upstream end 12 of the tube 10 and over part of its length, as can be seen more clearly on the left side of [Fig.3].

[0071] According to one possible embodiment of the introduction chamber 3, shown in Figures 3 and 4, an upstream cylindrical sleeve 30 is arranged around the upstream end 12 of the tube 10 of the enclosure, at a distance from it and coaxially with this tube.

[0072] The upstream sleeve 30 is closed on one hand at its downstream end by a downstream annular disc 31 and on the other hand, at its upstream end, by an upstream cover 32, which also closes the tube 10, more precisely the upstream end 12 of the latter.

[0073] Thus, the upstream sleeve 30, the downstream annular disc 31, the upstream cover 32 and the upstream end 12 of a portion of the length of the tube 10 together delimit said annular chamber 3 for the introduction of the heat transfer fluid into the enclosure 11.

[0074] An inlet conduit 4 is connected to the annular chamber 3 for the introduction of the heat transfer fluid and opens into the interior of the latter.

[0075] Preferably, this inlet conduit 4 opens radially into the annular chamber 3, as shown in the figures. In other words, the axis of the conduit 4 is preferably perpendicular to the axis X-X' of the tube 10. It can also open substantially radially into the chamber 3, that is to say, its axis is not strictly perpendicular to the axis X-X'. Preferably also, this inlet conduit 4 is made of a tube.

[0076] Several orifices 5 for introducing the heat transfer fluid are formed through the upstream end 12 of the tube 10 of the enclosure (i.e., through the wall that constitutes this tube). These orifices 5 allow the annular introduction chamber 3 to be connected to the interior of the enclosure 11 by the fluid.

[0077] Thus, the heat transfer fluid enters the heater through the inlet duct 4 (arrow i), from where it flows over the 360° of the annular introduction chamber 3 (arrows ii), before passing through the introduction orifices 5 (arrows iii) radially and finally flowing axially into the space provided between the different electric rods 20 (arrows iv).

[0078] The inlet ports 5 are formed on the periphery of the upstream end 12 of the tube 10, preferably even on the entire periphery (i.e. over 360°).

[0079] Preferably, and as is clearer in [Fig. 5], these inlet orifices 5 are aligned to form at least one row 50 of orifices. Preferably, this row 50 of orifices extends in a plane P perpendicular to the longitudinal axis X-X' of the tube 10.

[0080] As shown in Figures 5 to 9, the inlet ports 5 can take on a wide variety of shapes. Preferably, these ports are circular, as shown in [Fig. 6], square, as shown in [Fig. 9], or rectangular, as shown in Figures 5 and 8, because these shapes are simpler to manufacture. However, they can take any other shape, for example hexagonal or triangular, as shown in [Fig. 7], without departing from the scope of the invention.

[0081] Furthermore, the inlet ports 5 can be located at a distance from the cover 32, as shown in Figures 6, 7 and 9, or on the contrary, open onto the cover 32, as shown in Figures 5 and 8. In the latter case, the ports 5 can also be semi-circular.

[0082] Advantageously, on the same row 50, the distribution density of these introduction orifices 5 can also vary.

[0083] Thus, for example in [Fig. 6], it can be seen that the density of the inlet orifices 5 is higher in the lower part of the figure and lower in the upper part. Advantageously, it is possible to predict that the distribution density of the inlet orifices 5 will be greater in the part of the tube 10 of the enclosure opposite the inlet duct 4, (i.e., on the left in [Fig. 5]) and, on the contrary, be less important in the part of the tube 10 located opposite this inlet duct 4, so as to be able to modulate the flow rate entering radially into the tube 10.

[0084] It is possible to have a single row 50 of orifices 5, as shown in Figures 5, 6 and 8, or on the contrary to have several rows of orifices 5, referenced 50, 51 and 52, as shown for example in Figures 7 and 9. Preferably, there are at most four parallel rows of orifices 5.

[0085] Finally, even with orifices 5 of identical shape, it is possible to have orifices smaller than others.

[0086] Thus, for example, when the inlet ports 5 are arranged in at least two parallel rows, it is possible that each inlet port 5 in a row located further downstream (for example, row 51 or 52 in Figures 7 and 9) than in a row 50 located further upstream, has a smaller area than each inlet port 5 in said row 50 located further upstream. This arrangement is particularly advantageous if it is desired to modulate the fluid inlet velocity as well as its circumferential distribution. Furthermore, the axial length of the upstream unheated zones 211 and downstream zones 212 of the tube 10 can be significantly reduced, for example, to approximately 10 cm.

[0087] Furthermore, although this is not shown in the figures, it is also possible to have, on the same row of inlet ports 5, ports 5 which are smaller than others.

[0088] As can be seen in [Fig.3], preferably, the inlet orifices 5 are formed at the upstream end 12 of the tube 10 so as to be opposite the upstream non-heating zones 211 to avoid finding oneself in a situation where the end of the rod 20 which has the electrical resistance 22 would be insufficiently cooled.

[0089] As can be seen in [Fig.5], preferably the angle 01 between the two circumferential ends of an opening 5 can be between 5° and 10° to obtain a homogeneous circumferential distribution of the introduction of the fluid into the cavity 11 of [Fig.3] and not create overly dynamic fluid jets.

[0090] Furthermore, preferably, the angle 02 between the centers of two adjacent openings 5 ​​is between 5° and 10°. This value is chosen in particular to be consistent with the angle 01 used for the dimensions of the openings. This value makes it possible to maximize the passage cross-sections, to modulate a homogeneous circumferential distribution of the fluid entering the cavity 11 of the tube 10, and to reduce the unheated zone 211.

[0091] The thickness El of the annular introduction chamber 3, that is to say the distance between the inner face of the cylindrical sleeve 30 and the outer face of the tube 10 is, advantageously, between 5% and 20% of the diameter of the enclosure 11. The objective is to avoid high velocities in the introduction chamber 3 itself, which could cause additional pressure losses.

[0092] Advantageously, and as is clearer in Figures 4 and 10 and 11, the heater 1 also includes several deflectors 6, arranged alternately to form a baffled passage for the heat transfer fluid to be heated.

[0093] Thus, this fluid is better mixed and passes well into contact with all the electric rods 20, extracting all the heat energy, which guarantees good homogeneity of its temperature at the outlet of the heater.

[0094] In the embodiment shown in the figures, each deflector 6 has the shape of a truncated circular plate (i.e. missing a circular segment) and which therefore includes a straight edge 60 along a chord of the circle.

[0095] The deflectors 6 are arranged alternately head-to-tail (i.e. 180° to one of the next), so that the edge 60 of one is oriented towards the bottom of the heater and the edge 60 of the next is oriented towards the top of the heater (the bottom and the top being defined with respect to the normal operating position of the heater 1 which is horizontal).

[0096] Each deflector 6 is pierced with a plurality of holes 61, each of which allows for the reception of an electrical rod 20. Preferably, the rods 20 are mounted in the holes 61 with a small functional clearance (or mounting clearance). Thus, the majority of the heat transfer fluid flow circulates around the rods 20 (i.e., axially), then, when it reaches a stop against a deflector 6, flows around the edge 60 of the deflector and continues to the next deflector, and so on, until the outlet (see arrow Fl in [Fig. 11], which represents the zigzag flow of the heat transfer fluid). Only a minor portion of the flow passes through the functional clearance.

[0097] According to a first embodiment of the invention, it is possible to have a heater 1 comprising an annular inlet chamber 3 at its upstream end and having at its downstream end only an outlet tube, such as the outlet tube D of the prior art.

[0098] However, advantageously and as shown in [Fig.3], the heater 1 can also have at its downstream end an annular chamber 7 for venting the heat transfer fluid out of the enclosure 11. This allows us to benefit from the aforementioned advantages, particularly in terms of heating homogeneity, elimination of vibration of the rods and reduction of the heater length.

[0099] In this case, and similarly to what has been described for the upstream end of the heater, and which will therefore not be described again in detail, this annular discharge chamber 7 is delimited by a downstream cylindrical sleeve 70, arranged around the downstream end 13 of the tube 10 of the enclosure, at a distance from it and coaxially with this tube, by an upstream annular disc 71 and by a downstream cover 72.

[0100] An outlet conduit 8 is connected, preferably radially or substantially radially, to the sleeve 70 and opens into the annular discharge chamber 7. The outlet conduit 8 could also be connected axially to the sleeve 70, since the electrical connections of the resistors 22 are located at the upstream end.

[0101] Finally, several evacuation ports 9 for the heat transfer fluid are formed through the downstream end 13 of the tube of the enclosure, so as to put in fluidic communication the interior of the enclosure 11 and the annular evacuation chamber 7.

[0102] What has been described for the inlet ports 5 of the heat transfer fluid applies to these outlet ports 9, in particular with regard to the shape, distribution density, dimensions and positions of these ports and their number of rows, and will therefore not be described again in detail.

[0103] Finally, as shown in [Fig. 12], it is possible according to an alternative embodiment of the invention to have a heater 1' whose tube 10 contains two bundles of electric rods, arranged end to end axially in the tube 10. These bundles are respectively called upstream bundle 2 and downstream bundle 2' and they are arranged so that the downstream end of the upstream bundle 2 is located near the upstream end of the downstream bundle 2'.

[0104] Only two rods 20, respectively 20', of each bundle 2, 2' have been schematically represented in dashed lines on [Fig. 12]. The rods 20' of the downstream bundle 2' are connected to an electrical connection box 23'.

[0105] Advantageously, the upstream bundle 2 electrical rods 20 comprise an upstream non-heating zone 211, as described previously, and the inlet ports 5 are preferably arranged in front of this zone 211, and the downstream bundle 2' electrical rods 20' comprise a downstream non-heating zone 212', and the outlet ports 9 are preferably arranged in front of this zone 212'.

[0106] Inside the heater 1', the ends of the electric rods of the two bundles can be very close to each other.

[0107] This embodiment allows for a heater 1' that is longer than the heater 1 described previously and produces a greater heating power. It is also possible to construct two heaters 1 as previously described but without an annular chamber at one of their ends and to join them end to end by their respective tubes 10 to obtain the heater 1'.

Claims

1. Demands Thermal heater (1, 1') for a heat transfer fluid, in particular a molten salt, comprising: - a closed enclosure (11) comprising a cylindrical tube (10) having an upstream end (12) and a downstream end (13) with respect to the direction of flow of the heat transfer fluid inside the enclosure (H), - at least one bundle (2, 2') of a plurality of electric heating rods (20, 20') for heating this fluid, these rods (20, 20') being arranged axially inside said tube (10) of the enclosure, - an inlet duct (4) of the heat transfer fluid into the enclosure (11), and - an outlet duct (8) of this heat transfer fluid out of the enclosure (H), characterized in that it comprises an annular chamber (3) for introducing the heat transfer fluid into the enclosure, this annular inlet chamber (3) being arranged around the tube (10) of the enclosure and coaxially therewith and extending from the upstream end (12) of the tube (10) over a portion of its length, in that the inlet duct (4) is connected to this annular inlet chamber (3) and opens into it, and in that the upstream end (12) of the tube (10) of the enclosure comprises several inlet ports (5) for the heat transfer fluid,these inlet orifices (5) being distributed around the periphery of the tube (10) and establishing fluidic communication between the annular inlet chamber (3) and the interior of the enclosure (11), and in that it comprises an annular chamber (7) for evacuating the heat transfer fluid from the enclosure, this annular evacuation chamber (7) being arranged around the tube (10) of the enclosure and coaxially therewith and extending from the downstream end (13) of the tube (10) over a part of its length, in that the outlet conduit (8) is connected to this annular evacuation chamber (7) and opens into the interior of it, and in that the downstream end (13) of the tube (10) of the enclosure comprises several evacuation ports (9) for the heat transfer fluid, these evacuation ports (9) being distributed around the periphery of the tube (10) and providing fluid communication between the interior of the enclosure (11) and the annular evacuation chamber (7).

2. Thermal heater (1, 1') according to claim 1, characterized in that each electric rod (20, 20') of the bundle (2, 2') or of at least one of the bundles (2, 2') comprises an electric resistance (22) disposed inside a tube (21) longer than said electric resistance (22), so as to form at the upstream end of said tube (21) an area free of electrical resistance, referred to as the upstream non-heating zone (211), and in that the inlet ports (5) of the heat transfer fluid are formed in the portion of the tube (10) of the enclosure located around the upstream non-heating zones (211) of the electric rods (20, 20') of the bundle of electric rods (20, 20').

3. Thermal heater (1, 1') according to claim 1 or 2, characterized in that each electric rod (20, 20') of the bundle (2, 2') or of at least one of the bundles (2, 2') comprises an electric resistance (22) disposed inside a tube (21) longer than said electric resistance (22), so as to form at the downstream end of said tube (21) an area free of electrical resistance, called the downstream non-heating zone (212, 212'), and in that the discharge ports (9) of the heat transfer fluid are formed in the portion of the tube (10) of the enclosure located around the downstream non-heating zones (212, 212') of the electric rods (20, 20') of the bundle of electric rods (20, 20').

4. Thermal heater (1') according to claims 2 and 3, characterized in that it comprises within the tube (10) of the enclosure, a so-called "upstream" bundle (2) of electric rods (20) and a so-called "downstream" bundle (2') of electric rods (20'), arranged end to end axially in the tube (10) such that the downstream end of the upstream bundle (2) is located near the upstream end of the downstream bundle (2'), in that the electric rods (20) of the upstream bundle (2) include an upstream non-heating zone (211), and in that the electric rods (20') of the downstream bundle (2') include a downstream non-heating zone (212').

5. Thermal heater (1, 1') according to any one of the preceding claims, characterized in that the inlet conduit (4) opens radially or substantially radially into the annular inlet chamber (3) and / or in that the outlet conduit (8) opens radially or substantially radially in the annular evacuation chamber (7).

6. Thermal heater (1, 1') according to any one of the preceding claims, characterized in that the fluid inlet ports (5) and / or the fluid outlet ports (9) are aligned in the form of at least one row (50, 51, 52) of ports extending in a plane perpendicular to the longitudinal axis (X-X') of the tube (10), preferably in the form of at least two parallel rows of ports.

7. Thermal heater (1, 1') according to any one of the preceding claims, characterized in that the distribution density of the inlet orifices (5) of the fluid is greater in the part of the tube (10) of the enclosure located opposite to that where the inlet conduit (4) opens, and / or in that the distribution density of the outlet orifices (9) of the fluid is greater in the part of the tube (10) of the enclosure located opposite that where the outlet conduit (8) opens.

8. Thermal heater (1, 1') according to any one of the preceding claims, characterized in that the fluid inlet ports (5) and / or the fluid outlet ports (9) are circular, semi-circular, square or rectangular in shape.

9. Thermal heater (1, 1') according to any one of the preceding claims, characterized in that the fluid inlet orifices (5) are arranged in the form of at least two parallel rows of orifices and in that each fluid inlet orifice (5) of a row (52) located further downstream has an area less than the area of ​​each fluid inlet orifice (5) of a row (50, 51) located further upstream, and / or in that the fluid outlet orifices (9) are arranged in the form of at least two parallel rows of orifices and in that each fluid outlet orifice (9) of a row located further upstream has an area less than the area of ​​each fluid inlet orifice (9) of a row located further downstream.

10. A thermal heater (1, 1') according to any one of the preceding claims, characterized in that it comprises a plurality of deflectors (6) arranged alternately inside the tube (10) of the enclosure, these deflectors (6) extending perpendicularly to the axis of the tube (10) to ensure a zig-zag circulation of the heat transfer fluid inside the enclosure (11).

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