FR3010504A1 - MODULE AND THERMO-ELECTRIC DEVICE, PARTICULARLY FOR GENERATING AN ELECTRICAL CURRENT IN A MOTOR VEHICLE - Google Patents

Abstract

The invention relates to a thermoelectric device comprising a bundle (20) of thermoelectric modules (22), said modules comprising at least one thermoelectric element (3, 3p, 3n) of annular shape, capable of generating an electric current under the action of a temperature gradient exerted between two of its faces, one (4a), said first face being defined by an outer periphery surface and the other (4b), said second face, being defined by a inner periphery surface, said modules being configured to establish a heat exchange between said first face (4a) and a first fluid and to establish a heat exchange between said second face (4b) and a second fluid, said device being configured to deflect said first fluid through said beam (20) in a direction transverse to a stacking direction (24) of said electric thermoelectric elements (3, 3p, 3n) and / or said first fluid to flow in said stacking direction. The invention also relates to the use of such a device in an exhaust line and / or an exhaust gas recirculation circuit.

Description

The present invention relates to a module and a thermoelectric device, in particular for generating an electric current in a motor vehicle. In the automotive field, it has already been proposed thermoelectric devices using so-called electric thermo elements, for generating an electric current in the presence of a temperature gradient between two of their opposite faces according to the phenomenon known as Seebeck effect. These devices comprise a stack of first tubes, intended for the circulation of the exhaust gases of an engine, and second tubes, intended for the circulation of a heat transfer fluid of a cooling circuit. The electrical thermo elements are sandwiched between the tubes so as to be subjected to a temperature gradient from the temperature difference between the hot exhaust gases and the cold cooling fluid.

Such devices are particularly interesting because they make it possible to produce electricity from a conversion of the heat coming from the exhaust gases of the engine. They thus offer the possibility of reducing the fuel consumption of the vehicle by replacing, at least partially, the alternator usually provided therein to generate electricity from a belt driven by the engine crankshaft. . It has already been developed by the holder of thermoelectric elements of annular shape, the temperature gradient for generating the electric current being imposed between two of their inner and outer cylindrical faces. The hot fluid and the cold fluid then circulate coaxially, one circulating inside the ring and the other outside. This solution, however, has integration difficulties that cause the commitment of a large amount of material. In addition to cost implications, such a commitment of material increases the thermal inertia of the device and therefore its effectiveness, particularly its response time. It may not be able to take advantage of strong but too short heat increase of the hot fluid. The invention proposes to improve the situation and concerns for this purpose a thermoelectric device comprising a bundle of thermoelectric modules, said modules comprising at least one thermoelectric element of annular shape, capable of generating an electric current under the action a temperature gradient exerted between two of its faces, one, said first face being defined by an outer periphery surface and the other, said second face being defined by an inner periphery surface, said modules being configured to establish a heat exchange between said first face and a first fluid and to establish a heat exchange between said second face and a second fluid, said device being configured to deflect said first fluid through said beam in a direction transverse to a direction d stacking said thermoelectric elements and / or allowing said first fluid to flow er following said stacking direction. Due to the transverse orientation of the fluid circulation, it is possible to limit the material engaged, in particular the first fluid side, to increase the exchange surfaces. In addition, a ducting effect of the first fluid is carried out enabling it to maintain a relatively constant temperature as long as it has not passed through the beam.

It may also be noted that configuring the device so that said first fluid can follow two different directions through the device makes it possible, by making it follow the beam, to be able to limit the pressure drops imposed on the first fluid passing through the device without crossing. the beam. This also makes it possible to have, if desired, a device comprising a first part, dedicated to the thermoelectric function, in which a temperature gradient is kept as constant as possible between the first and second fluid and a second part enriching the device of a heat exchange function between the first and second fluid, this with a high level of integration.

Said thermoelectric modules are advantageously configured to allow a flow of said first and second fluids, said second fluid having a higher heat exchange coefficient of said first fluid. The first fluid is, in particular exhaust gas. The second fluid is, for example, a coolant.

The invention thus proposes a module whose efficiency is optimized by the fact that the exchange surface is larger at the level of the fluid having the lowest exchange coefficient. There is a kind of a ratio between the thermal resistance on the first fluid side, for example gas, and the thermal resistance on the second fluid side, in particular of the more balanced liquid, favoring the operation of the assembly. According to various embodiments of the invention that may be taken together or separately: said device comprises a valve for modulating the flow rate of first fluid through the beam and the flow rate of the first fluid along said stacking direction, said bundle is tubular so as to define a flow conduit of said first fluid, extending in said stacking direction, said bundle has a substantially circular section, said device being configured to radially deflect said first fluid through the beam from said duct, - said device comprises first secondary exchange surfaces with the first fluid, - said first secondary exchange surfaces connect the modules together so that they pass through said modules, - the surfaces of secondary exchange are fins, - said fins comprise a central orifice for the flow of the pre first fluid in said stacking direction and a plurality of passage openings of the modules, - said fins are of annular shape, - said fins are parallel to each other and / or orthogonal to the stacking direction, - said device is configured to allow a heat exchange between said first fluid and said second fluid, downstream of the passage of said first fluid through said bundle of thermoelectric modules in the direction of flow of said first fluid, said device comprises circulation tubes of said second fluid; fluid, said exchange tubes, for allowing said exchange of heat between the first and second fluids, - said exchange tubes extend in said stacking direction, - said exchange tubes are located radially beyond said electric thermo modules, said first secondary surfaces comprise through holes of said exchange tubes, said passage orifices of said exchange tubes being located downstream of the passage orifices of the thermoelectric modules in the direction of flow of the first fluid through the bundle, said passage orifices of said exchange tubes are located radially beyond said crown of passage orifices of said electric modules, - said device comprises second thermally insulated second exchange surfaces of said electric thermo modules and in thermal contact with said second fluid flow tubes, - said second secondary exchange surfaces are flat fins parallel to the fins of the first secondary exchange surfaces, - said fins of the second secondary exchange surfaces comprise a central passage greater than the central orifice of the fins of the first secondary exchange surfaces so that said modules electric thermo pass through said central passage, - the exchange surfaces seco Ndaire include a catalytic coating to provide catalytic conversion of toxic components of the first fluid. According to a first example of application, said device is used in an exhaust line of a heat engine, especially a motor vehicle, to allow electricity generation thanks to the temperature gradient created between the exhaust gas and the engine. second fluid. It is thus configured to be positioned in an exhaust duct of the motor vehicle so that said exhaust gases flowing in said duct define said first fluid.

According to another application example, said device is used in an exhaust gas recirculation circuit at the intake of the engine to allow electricity generation thanks to the temperature gradient created between the recirculated exhaust gas and the second fluid. It is thus configured to be positioned in a motor vehicle recirculated exhaust gas circuit so that said recirculated exhaust gas flowing in said circuit defines said first fluid.

In such an application, it will then be particularly advantageous if, as mentioned above, said device is configured to allow a heat exchange between said first fluid and said second fluid, downstream of the passage of said first fluid through said bundle of thermo modules. electric in the direction of flow of said first fluid. There is indeed a hybrid device providing both a thermoelectric function and a cooling function of the recirculated exhaust gas.

It may be noted in this regard that the invention also relates to a hybrid device providing both a thermoelectric function and a cooling function of the recirculated exhaust gas, without said device being necessarily configured to deflect said first fluid through said beam in a direction transverse to a stacking direction of said electric thermoelectric elements nor allow said first fluid to flow in said stacking direction. Still in the same application, it will be particularly advantageous, as mentioned above, that said device comprises a valve for modulating the first fluid flow through the beam and the first fluid flow along said stacking direction. There is then an integrated system in which the recirculated exhaust gas can pass through the device by bypassing the bundle of electric thermo modules. This avoids excessive pressure loss on the recirculated exhaust gas which would be detrimental to proper engine operation, especially at full engine load. The invention also relates to a thermoelectric module for a thermoelectric device as described above, in particular a module provided with secondary exchange surfaces with the first annular-shaped fin fluid specific to said module, in particular fins in circular ring shape. The invention will be better understood in the light of the following description which is given for information only and which is not intended to limit it, accompanied by the attached drawings among which: FIGS. 1 and 2 illustrate schematically, in perspective, steps of mounting an example of a thermoelectric module of a thermoelectric device according to the invention, - Figure 3 partially and schematically illustrates, in perspective, the module of Figures 1 and 2 after FIG. 4 and 5 schematically illustrate, in perspective, an exemplary beam according to two embodiments of the thermoelectric device according to the invention; FIG. 6 illustrates a front view of a first type of fins; intended for use in a thermoelectric device according to the invention, - Figure 7 illustrates a thermoelectric device according to the invention schematically, according to a longitudinal sectional plane. e, equipped with a beam of the type of FIG. 5 and fins of the type of FIG. 6, FIG. 8 illustrates in front view a second type of fins intended to be used in a thermoelectric device conforming to FIG. the invention.

As illustrated in Figures 1 and 2, the invention relates to a thermoelectric module. Said module is able to exploit the temperature difference between a first fluid 1, said to be hot, in particular the exhaust gases of an engine, and a second fluid 2, said to be cold, in particular a coolant of a cooling circuit, lower temperature than the first fluid. Said second fluid has a heat exchange coefficient greater than said first fluid. The module comprises at least thermoelectric elements 3p, 3n, of annular shape, capable of generating an electric current under the action of a temperature gradient between two of their faces, the one 4a, said first face being defined by an outer periphery surface, cylindrical, and the other 4b, said second face, being defined by an inner periphery surface, cylindrical.

Said module is advantageously configured to establish a heat exchange between said first face 4a and the first fluid, circulating along the arrow illustrated D, corresponding to a stacking direction of said thermoelectric elements 3p, 3n, and to establish a heat exchange between said second face 4b and the second fluid, flowing outside said thermoelectric elements 3. This promotes the exchange between the electric thermo elements 3p, 3n and the fluid having the lowest heat exchange coefficient, here, the exhaust gas.

Said first and second faces 4a, 4b are, for example, of rounded section, in particular circular and / or oval. Such elements operate, according to the Seebeck effect, by making it possible to create an electric current in a load connected between said faces 4a, 4b subjected to the temperature gradient. In a manner known to those skilled in the art, such elements consist, for example, of Bismuth and Tellurium (Bi2Te3). The thermoelectric elements may be, for a first part, elements 3p of a first type, said P, for establishing a difference in electric potential in a direction, said positive, when they are subjected to a temperature gradient given, and, for the other part, elements 3n of a second type, said N, allowing the creation of a difference of electric potential in an opposite direction, said negative, when they are subjected to the same temperature gradient .

In Figures 1 and 2, the thermoelectric elements 3 shown are formed of a ring in one piece. They may however be formed of several pieces each forming an angular portion of the ring.

The first surface 4a has, for example, a radius of between 1.5 and 4 times the radius of the second surface 4b. It may be a radius equal to about 2 times that of second surface 4b. Said thermoelectric element has, for example, two opposite planar faces 6a, 6b opposite. In other words, the ring constituting the thermoelectric element is of rectangular radial section. An example of an association of the thermoelectric elements with one another in the module according to the invention is described below.

Said thermoelectric elements 3p, 3n are arranged, for example, in the longitudinal extension of one another, in particular in a coaxial manner, and the P-type electrical thermoelectric elements alternate with the N-type thermoelectric elements, according to FIG. stacking direction D.

They are, in particular, of identical shape and size. They may, however, have a thickness, that is to say a dimension between their two planar faces, different from one type to another, particularly depending on their electrical conductivity.

Said thermoelectric elements 3p, 3n are, for example, grouped in pairs, each pair being formed of a said P-type thermoelectric element and a said N-type thermoelectric element, and the said module is configured to allow a flow of current between the first surfaces of the thermoelectric elements of the same pair and a flow of current between the second surfaces of each of the electric thermo elements of said pair and the thermoelectric element adjacent to the neighboring pair. In this way, a series circulation of the electric current is ensured between the electric thermoelectric elements 3p, 3n arranged next to one another in the stacking direction D.

Again to facilitate the configuration of the fluid circulation circuits 1, 2, it can be provided that said electric thermo elements 3p, 3n are arranged relative to each other so that their first and / or second surface 4a, 4b are in the extension of one another. Said first and / or second surfaces 4a, 4b are thus inscribed, for example, in a surface generated by a straight line. For the circulation of fluids, the module according to the invention may comprise a channel 7 for cold liquid circulation in contact with said second surface 4b of said electric thermo elements 3p, 3n. The at least one liquid circulation channel 7 is, for example, of circular section. The channel or channels 7 here comprise a cold liquid circulation tube 12 on which at least thermoelectric elements of the same type are alternated, alternating in the direction of longitudinal extension of the tube, which corresponds to said stacking direction D, with thermoelectric elements of the other type. The tubes 12 are, in particular, metallic. According to the above, the channel 7 cold liquid circulation is unique and placed in the center of the module. According to one variant, a plurality of cold liquid circulation channels may be provided in the same module.

Said module may furthermore comprise electrical insulation means 20 arranged between two faces 6a, 6b opposite neighboring thermoelectric elements 3p, 3n according to the stacking direction D. In FIG. 2, the elements thermo electric 3p, 3n, and the electrical insulation means 20 are assembled, alternately, on the tubes 12 of cold fluid circulation.

Said module may further comprise first electrical connection means 21 connecting the outer periphery surfaces 4a of two of said thermoelectric elements, provided adjacent and of different types. Said first means 21 for electrical connection comprise, for example, a layer of electrically conductive material, in particular copper and / or nickel, coating said electric thermo elements 3p, 3n. In Figure 2, such a layer of material is illustrated only on the last two thermoelectric elements right. Between said tube 12 and said electric thermo elements 3p, 3n, are also provided current flow paths, not shown. They connect the inner periphery surfaces 4b of two of said adjacent thermoelectric elements, of different types, in such a way as to shift to the layer of material provided at the outer periphery 4a of the electric thermoelectric elements so as to allow the more evoked series circulation. high. Layers of thermally conductive and electrically insulating material may also be provided at the surface of the tube 12 and / or layer of material 21 to avoid short-circuits between conductors. As illustrated in FIG. 3, said module may be provided with secondary exchange surfaces with the first fluid. It is, for example, fins 10 in thermal contact with said thermoelectric elements 3, in particular flat fins parallel to each other and transverse, in particular orthogonal to the stacking direction D. Said fins 10 are here of annular shape, in particular of circular section. They thus have a central orifice 11 for the passage of said modules. Said fins 10 are fixed, for example, on said modules, in particular by crimping and / or brazing. They are here positioned parallel to each other with a spacing allowing a good heat exchange with the first fluid while limiting the losses of charges.

However, as illustrated in FIG. 4, the invention also relates to a thermoelectric device comprising a bundle 20 of thermoelectric modules 22 as described above, here provided with said fins 10.

According to the invention, said device is configured to deflect said first fluid, here from an incident direction 24, through said beam 20 in a direction transverse to the direction of stacking of said electric thermoelectric elements 3, said corresponding stacking direction here at said incident direction 24, and / or allowing said first fluid to flow in said stacking direction 24. By conferring such orientation on the first fluid, it is channeled before it comes into contact with the electric thermo modules and it is prevented from being cooled in contact with other elements. Said beam 20 may in particular be tubular so as to define a flow conduit 28 of said first fluid, extending in said stacking direction. Said beam 20 has, for example, a substantially cylindrical shape, in particular of circular section, said device being configured to radially deflect said first fluid 1 through the beam from said conduit. Said modules 22 are thus distributed according to a ring, said flow duct 28 being located inside said ring, and the first fluid 1 is deflected through said modules 22 from said flow duct 28, this over 360 ° . For its part, the second fluid 2 flows in said modules in said stacking direction.

As already mentioned, said modules 22 may comprise first secondary exchange surfaces with the first fluid. In FIG. 4, these are fins 10 such as those described in the context of FIG. 3, that is to say specific to each of the modules 22. According to an alternative embodiment, said first surfaces of secondary exchange connect the modules 22 to each other. In this way, the mechanical cohesion of the device is reinforced and the number of components is limited. The fins may have a passage for the flow of the first fluid in said stacking direction and a plurality of passage openings of the modules at which said fins are in thermal contact with the modules. Such an embodiment will be developed below in connection with FIGS. 5 and 6 in the context of a specific application of the invention, secondary exchange surfaces, in particular fins, connecting said modules which can of course be used in other applications.

As illustrated in FIG. 5, said device is advantageously configured to allow a heat exchange between said first fluid 1 and said second fluid 2, downstream of the passage of said first fluid 1 through said bundle 20 of thermoelectric modules 22, according to the flow direction of said first fluid 1. In this way, it is possible to produce a hybrid device fulfilling both a thermoelectric generator function and a heat exchanger function, in particular the cooling of recirculated exhaust gas in the case of a device configured to be located in an exhaust gas recirculation circuit.

According to this aspect of the invention, said device comprises tubes 30 for circulating said second fluid 2, said exchange tubes, extending in said stacking direction to allow said exchange of heat between the first and second fluids. Said exchange tubes 30 are located, for example, radially beyond said thermoelectric modules 22, for example in one or more rings of larger diameter than the ring of thermoelectric modules 22. As illustrated in FIG. fins 10 of said first secondary exchange surface may be common to both the thermoelectric modules 22 and said exchange tubes 30. They are said in the following hybrid fins. Said hybrid fins 10 have, for example, a central orifice 42, in particular circular, for the passage of the first fluid. Said hybrid fins 10 furthermore have orifices 44 for the passage of said electric thermo modules 22, said orifices 44 being here distributed along a ring coaxial with the central orifice 42 and / or regularly distributed angularly. Said passage orifices 44 of the modules 22 are, for example, circular in sectional correspondence with the section of said modules 22.

Said first secondary exchange surfaces, here said hybrid fins 10, are further in thermal contact with said exchange tubes 30. In this sense, they comprise, for example, orifices 46 for the passage of said exchange tubes 30. passage orifices 46 of said exchange tubes 30 are located downstream of the passage orifices 44 of the thermoelectric modules 22, in the direction of flow of the first fluid through the beam. Said passage orifices 46 of said exchange tubes 30 may be located radially beyond said ring of orifices 44 for passing said thermoelectric modules 22.

Here, said passage orifices 46 of said exchange tubes 30 are distributed in a first ring conforming to an outer contour of the ring of passage openings 44 of said electric modules 22 and a second peripheral ring in which they are grouped in pairs. to increase the density of exchange tubes 30.

In this embodiment also, said fins 10 are flat, parallel to each other and orthogonal to the stacking direction. As illustrated in FIG. 7, said device may comprise a housing 50. Said housing 50 defines a housing 52 accommodating said beam 20 here accompanied by said first secondary exchange surfaces, in particular said hybrid fins 10. Said housing 52 is further configured to allow the circulation of said first fluid 1, in said stacking direction, inside said beam and / or, according to the arrows marked 26, between said thermoelectric modules 22. Said housing 52 extends axially, for example, in said stacking direction D. It comprises here an axial inlet 54 and / or an axial outlet 56 for said first fluid. Said axial inlet 54 opens axially into an axial end of said flow conduit 28 of the first fluid. That being so, said device may comprise a valve 58, for modulating the flow, here radial, of first fluid 1 through the beam 20 and the flow, in this case axial, of first fluid 1 along said stacking direction D. Said valve 58 is arranged, for example, at an axial end of said flow duct opposite to that into which said axial inlet 54 opens. Thus, when the valve 58, in particular of butterfly type, is closed, a majority of the first fluid crosses said device in said stacking direction D, remaining inside said flow conduit 28, and passes at an orifice 60, made passing through the opening of said valve 58, said first fluid finally exiting by said axial outlet 56. When said valve 58 is closed, the first fluid is deflected from the flow conduit 28 through the bundle 20 and then flows axially along the housing 50. emitted axial beam facing the axial outlet 56, it is then diverted to the latter. In the example illustrated in FIG. 7, the device further comprises exchange tubes 30 and hybrid fins 10. When said valve 58 is closed, said first fluid passes firstly through said beam 20 and then between said exchange tubes 30, this between said hybrid fins 10. The heat of said exhaust gas is thus communicated to said modules 22 by said hybrid fins 10 and heat exchange takes place between said first fluid and said second fluid via said exchange tubes 30 and the same said hybrid fins 10. Said device may further comprise collectors 80 for the second fluid. They allow, for example, a series circulation of said second fluid first in said exchange tubes 30 and then in said modules 22. From an electrical point of view, the modules 20 may be connected together in series and / or in parallel, by connections, not shown, located at their longitudinal ends. As illustrated in FIG. 8, said device may also comprise second secondary exchange surfaces 70, thermally insulated from said electric thermo modules 22 and in thermal contact with said exchange tubes 30. This is, for example, fins, said exchange fins 72, planes. They comprise a central flow passage orifice 74 of the first fluid, greater than the central orifice 42 of the hybrid fins 10, so that said modules 22 pass through the central passage 74 of said exchange fins 72. exchange fins 72 still include here passage holes 76 of the exchange tubes 30. Said exchange fins 72 are intended to be parallel to the hybrid fins 10. Said exchange fins and said hybrid fins are advantageously positioned that their respective holes 76, 46 for passage of the exchange tubes 30 are in the extension of each other.

Said hybrid and / or exchange fins are, for example, metallic. They may advantageously comprise a catalytic coating for catalytic conversion of toxic components of the first fluid. In the case of exhaust gas, said module can in this way equip a catalytic converter in addition or substitution of the components conventionally used for catalysis in such equipment.

Claims (15)

REVENDICATIONS1. Thermoelectric device comprising a bundle (20) of thermoelectric modules (22), said modules comprising at least one annular-shaped thermoelectric element (3, 3p, 3n) capable of generating an electric current under the action of a temperature gradient exerted between two of its faces, one (4a), said first face being defined by an outer periphery surface and the other (4b), said second face, being defined by an inner periphery surface, said modules being configured to establish a heat exchange between said first face (4a) and a first fluid and to establish a heat exchange between said second face (4b) and a second fluid, said device being configured to deflect said first fluid through said first beam (20) in a direction transverse to a stacking direction (24) of said electric thermoelectric elements (3, 3p, 3n) and / or allowing said first fluid to flow according to the said stacking direction. The apparatus of claim 1 comprising a valve (58) for modulating first fluid flow through beam (20) and first fluid flow along said stacking direction (24). Apparatus according to any one of the preceding claims wherein said bundle (20) is tubular so as to define a flow conduit (28) of said first fluid, extending in said stacking direction (24). 4. Device according to claim 3 wherein said beam (20) has a substantially circular section, said device being configured to radially deflect said first fluid through the beam (20) from said conduit (28). 5. Device according to any one of the preceding claims, comprising first secondary exchange surfaces with the first fluid. The thermoelectric device of claim 5, wherein said first secondary exchange surfaces connect the modules (20) to each other. 7. Device according to any one of claims 5 or 6, wherein the secondary exchange surfaces are fins (10). 8. Device according to claim 7 wherein said fins (10) comprise a central orifice (42) for the flow of the first fluid in said stacking direction (24) and a plurality of orifices (44) for passage of the modules. (22). 9. Device according to any preceding claim configured to allow a heat exchange between said first fluid and said second fluid, downstream of the passage of said first fluid through said bundle (20) of thermoelectric modules (22), according to the direction of flow of said first fluid. 10. Device according to claim 9 comprising tubes (30) for circulating said second fluid, extending in said stacking direction (24) to allow said heat exchange between the first and second fluids. 11. Device according to claim 10 comprising second secondary exchange surfaces (70) thermally insulated from said electric thermo modules (22) and in thermal contact with said tubes (30) for the flow of the second fluid. The device of any one of claims 5 to 8 or 11, wherein the secondary exchange surfaces (10,70) comprise a catalytic coating for catalytically converting toxic components of the first fluid. 13. Device according to any preceding claim configured to be positioned in a motor vehicle exhaust line so that the exhaust gas flowing in said conduit define said first fluid. 14. Device according to any one of claims 1 to 12 configured to be positioned in a motor vehicle recirculated exhaust gas circuit so that said recirculated exhaust gas flowing in said circuit defines said first fluid. 15. Thermoelectric module for thermoelectric device according to any one of claims 1 to 14.