EP3248228A1

EP3248228A1 - Thermoelectric generator and thermal module for such a generator

Info

Publication number: EP3248228A1
Application number: EP16701020.6A
Authority: EP
Inventors: Cédric DE VAULX; Kamel Azzouz
Original assignee: Valeo Systemes Thermiques SAS
Current assignee: Valeo Systemes Thermiques SAS
Priority date: 2015-01-19
Filing date: 2016-01-19
Publication date: 2017-11-29
Also published as: WO2016116463A1; FR3031838B1; FR3031838A1

Abstract

The invention relates to a thermoelectric generator (10) including at least one thermal module (20), said thermal module (20) comprising thermoelectric elements (21) which are ring-shaped such as to form a substantially cylindrical thermoelectric assembly (22) when arranged side by side, said thermal module (20) being made up of at least one thermoelectric assembly (22) and a guiding casing (25) configured so as to cause a first fluid to hug the outer contour of said one or more thermoelectric elements (21), said generator (10) including a plurality of said thermoelectric modules (20) arranged about a main axis (Y), referred to as the generator axis (Y). The invention also relates to a thermal module (20) for such a generator (10).

Description

Thermoelectric generator and thermal module for such a generator

The invention relates to a thermoelectric generator and a thermal module comprising such a generator.

In the automotive field, it has already been proposed thermal modules using thermoelectric elements for producing an electric current in the presence of a temperature gradient between two of their opposite faces according to the phenomenon known as the Seebeck effect. These modules 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 thermoelectric 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 coolant.

Such modules 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 annular thermoelectric elements, the temperature gradient for generating the electric current being imposed between two of their internal and external cylindrical faces. The hot fluid and the cold fluid then circulate coaxially, one circulating inside the ring and the other outside.

However, this presents integration difficulties when it comes to optimizing the performance of the generators.

The invention proposes to overcome these disadvantages and concerns, for this purpose, a thermoelectric generator comprising at least one thermal module, said thermal module comprising thermoelectric elements in an annular form so as to form a thermoelectric assembly substantially cylindrical when arranged side by side, said thermal module being composed of at least one thermoelectric assembly and a guide casing configured so as to cause a first fluid to conform to the outer contour of the one or more thermoelectric elements.

According to the invention, said generator comprises a plurality of said thermoelectric modules arranged, in particular radially, around a main axis, said axis of the generator.

The thermal module of the invention has a guide casing ensuring the conduction of a fluid plate as close to the thermoelectric elements that compose it. This promotes a good heat exchange between them. In addition, the arrangement of the modules allows a circulation of the first fluid in parallel around them, rather than in series, which further enhances performance while limiting congestion.

According to various embodiments of the invention, which may be taken together or separately:

said modules form a ring around said axis of the generator,

said module comprises two of said thermoelectric assemblies, said envelope has an inlet and an outlet for said first fluid, said inlet and / or said outlet being formed of an elongate slot,

said envelope comprises cylindrical housings, each housing accommodating one of said sets,

said housings are arranged tangentially to each other, said inlet and said outlet being situated substantially at a common plane of symmetry of said housings,

said thermoelectric elements are provided with external fins,

said assembly is configured so that the first fluid forms a hot source of heat of a temperature gradient; said thermoelectric generator further comprises a conduit configured to circulate said first fluid along said axis; of the generator, said duct having a communication zone, said contact zone, with the guiding envelopes of said thermal modules, said contact zone allowing the passage of said first fluid of said conduit to said envelopes, in particular in a direction transverse to the direction of flow of said first fluid in said conduit,

said thermoelectric generator further comprises a collector for the first fluid at the outlet of said envelopes, said collector opening downstream from said contact zone,

said thermoelectric generator further comprises a circuit capable of circulating a second fluid inside the thermoelectric elements, said second fluid forming a second source of heat,

said thermoelectric generator further comprises a flow control device configured to be positioned inside said generator so as to modulate the quantity of the first fluid flowing through said thermoelectric generator,

said flow control device is a valve,

said thermoelectric generator is configured to be positioned in a motor vehicle exhaust line so that the exhaust gases flowing in said line define said first fluid and / or in a recirculated exhaust gas circuit of a motor vehicle; whereby said recirculated exhaust gas flowing in said circuit defines said first fluid.

The invention also relates to a thermal module for a thermoelectric generator according to any one of the preceding claims.

The invention will be better understood, and other objects, details, features and advantages thereof will become more clearly apparent in the following detailed explanatory description of at least one embodiment of the invention given to As a purely illustrative and non-limiting example, with reference to the accompanying schematic drawings.

On these drawings:

FIG. 1 is an isometric view of an exemplary embodiment of a thermoelectric assembly according to the invention, FIG. 2 is a diagrammatic representation, in cross-section, of an exemplary embodiment of a thermoelectric module according to the invention,

FIG. 3 is an isometric view of an example of a radial arrangement of thermoelectric modules,

FIG. 4 is an isometric view of an exemplary embodiment of a duct according to the invention, said duct having zones intended to be in contact with said thermal modules,

FIG. 5 is an isometric view of an exemplary embodiment of a thermoelectric generator according to the invention when it is positioned in a motor vehicle exhaust line,

FIG. 6 is a diagrammatic representation, in longitudinal section, of the example illustrated in FIG. 5, said FIG. 6 representing an exemplary embodiment of a flow control device according to the invention, in the open position,

- Figure 7 is the same figure as Figure 6, the flow control device being in the closed position.

As illustrated in the figures, the invention relates to a thermoelectric generator 10, said generator 10 comprising at least one thermal module 20, said thermal module 20 comprising thermoelectric elements 21.

In FIG. 1, said thermoelectric elements 21 are in annular form. Arranged side by side, they form a thermoelectric assembly 22 substantially cylindrical. Advantageously, said thermoelectric assembly 22 is a hollow cylinder, centered on an axis referenced X. This allows the circulation of a first fluid outside said cylinder and a second fluid, inside.

Said thermoelectric elements 21 are configured to produce an electric current from a temperature gradient existing between a first and a second heat source.

More specifically, the thermoelectric assembly 22 comprises a plurality of thermoelectric elements 21, here annular shapes, capable of generating a electric current under the action of a temperature gradient exerted between two of their faces, one said first active face, being defined by an outer periphery surface, cylindrical, and the other, said second active face, being defined by an inner periphery surface, cylindrical. Said first and second faces are, for example, of circular section. More generally, any section of rounded and / or polygonal shape is possible.

Such elements 21 operate, according to the Seebeck effect, by making it possible to create an electric current in a load connected between said faces subjected to the temperature gradient. In a manner known to the person skilled in the art, such elements are constituted, for example, by low temperature material, such as the telluride alloys of Bismuth and Antimony (Bi, Sb) Te3; or high temperature material, such as magnesium and tin silicates Mg2 (Si, Sn) or Manganese (MnSi).

The thermoelectric elements 21 may be, for a first part, elements of a first type, called P, making it possible to establish an electrical potential difference in a direction, called positive, when they are subjected to a given temperature gradient , and, for the other part, elements of a second type, called N, allowing the creation of an electric potential difference in the opposite direction, called negative, when they are subjected to the same temperature gradient.

The thermoelectric elements 21 are preferably made 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 has, for example, a radius between 1, 5 and 4 times the radius of the second surface. It may be a radius equal to about 2 times that of second surface.

The thermoelectric elements 21 have, for example, two opposite parallel flat faces, also called side faces. In other words, the ring constituting each thermoelectric element 21 is of rectangular annular section. In FIG. 1, said thermoelectric elements 21 are arranged, for example, in the longitudinal extension of one another, in particular in a coaxial manner; they alternate between elements P and elements N in a direction marked X. They are, in particular, of identical shape and dimension. 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 21 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 thermoelectric assembly 22 is configured to allow current flow. 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 thermoelectric elements 21 of the same pair and the thermoelectric element 21 adjacent to the neighboring pair. This ensures a series flow of electric current between the thermoelectric elements 21 arranged next to each other in the X direction.

Again to facilitate the configuration of the fluid circulation circuits it can be provided that said thermoelectric elements 21 are arranged relative to each other so that their first and / or second active face are in line with one another. 'other. Said first and / or second active faces are thus registered, for example, in a surface generated by a straight line. For the circulation of the fluids, it may be provided a tube for the circulation of cold liquid in contact with said second active face of said thermoelectric elements 21. The cold liquid circulation tube or tubes are visible in FIG. 5. They are, for example, of circular section. Said thermoelectric assembly 22 may further comprise connectors between the first and second thermoelectric elements. For example, along the X direction, a connector of a first type is systematically provided between an N type thermoelectric element and a P type thermoelectric element. A connector of a second type, is it systematically provided between a P-type thermoelectric element and an N-type thermoelectric element.

Said connectors differ in their diameter. Thus, the connector provided between an N-type thermoelectric element and a P-type thermoelectric element will be smaller in diameter than the connector provided between said P-type thermoelectric element and the next N-type thermoelectric element.

In other words, for the thermoelectric assembly 22, two sets of connectors of different sizes are required. One for the cold-source electrical connection and a second, for the hot-source side, of larger diameter.

FIG. 2 diagrammatically illustrates the thermal module 20 of the invention which is composed of at least one thermoelectric assembly 22 and a guide casing 25 configured so as to cause said first fluid to conform to the external contour of said thermoelectric element (s). 21. The arrows in the figure illustrate such guidance, according to a fluid plate of small thickness relative to the diameter of the thermoelectric elements 21.

Here, said module 20 comprises two of said thermoelectric assemblies 22, 22 ', each forming a hollow cylinder centered on the X axis, X'. Here again, said guide casing 25 comprises cylindrical housings 24, 24 '; each of them accommodating one of said sets 22, 22 '. Said envelope 25 has, in addition, an inlet E and an outlet S for the first fluid. Said input E and said output S are advantageously formed of an elongated slot in order to optimize the passage of said first fluid through (see also FIG. 3 for an isometric representation of said slots). The thermoelectric assemblies 22 are here identical made of high temperature material. According to an alternative embodiment not shown, the thermoelectric assemblies 22 are identical and consist of low temperature material. According to another embodiment, the two thermoelectric assemblies are different. A first thermoelectric assembly, close to the central tubing is made of high temperature material (silicides) and the second is made of low temperature material (Tellurides).

Said housings 24, 24 'are preferably arranged tangentially to each other, so that they have a passage from one to the other formed at level of a common portion of their periphery. Said housings 24, 24 ', respectively centered on their axis X and X', form a plane of symmetry, called common plane of symmetry, passing through said two axes X, X '.

Said input E and said output S are preferably also located in this common plane of symmetry.

It should be noted that the thickness of the first fluid plate formed between the thermoelectric elements 21 and the guiding envelope 25 is, for example, less than one-third to one-quarter to one-fifth of the radius of the cylinder formed by said assembly. thermoelectric 22, 22 '.

It should also be noted that said thermoelectric elements 21 may advantageously be provided with external fins in order to facilitate exchanges of heat with the first fluid which circulates outside said elements 21.

According to the invention, said thermoelectric generator 10 comprises a plurality of said thermoelectric modules 20 arranged, advantageously radially, around a main axis, called the generator axis, and referenced Y thereafter (see FIG. 3). They thus form a ring around the Y axis.

FIG. 3 also illustrates the inputs E and outputs S of said thermal modules 20, said inputs E being located close to said Y axis and the outputs being further away from said Y axis by comparison. Said inputs E thus form an internal ring configured to circulate said first fluid along said Y axis of the generator 10.

Said inner ring is a communication zone, called contact zone which is materialized by a conduit 30.

FIG. 4 illustrates an exemplary embodiment of said duct 30. It has a substantially cylindrical shape, designed to match the annular shape drawn by said inputs E. Said duct 30 furthermore has a plurality of slots 31 arranged radially around its circumference, said lights 31 being formed in the form of elongated slots to cooperate with said inputs E of said 25. This makes it possible to pass the first fluid between said duct 30 and the inlet E of said envelopes 25.

In other words, the duct 30 is substantially cylindrical and has substantially rectangular openings, the slots 31, radially distributed to allow optimal connection to the thermal modules 20.

On the other hand, said thermoelectric generator 10 comprises a collector 32 for the first fluid at the output of said thermal modules 20.

Said collector 32 is visible in FIGS. 5 to 7.

Said collector 32 is illustrated opening downstream of said contact zone, as is best seen in Figure 7. The fact that the manifold 32 opens downstream of said contact zone allows the escape of the first fluid to the outside.

More specifically, as shown schematically by arrows in FIG. 7, the first fluid is forced to flow transversely to the Y axis by a flow control device 50. The first fluid is then led to the thermal modules 20 in the direction of the outputs S of said modules 20. The first fluid is then guided by the internal walls of the manifold 32, said inner walls then acting as a guiding casing of said first fluid, downstream of said contact zone and said device. flow control 50.

As illustrated in said FIG. 5, said thermoelectric generator 10 further comprises a circuit 40 able to circulate said second fluid inside the thermoelectric elements 21. Said circuit 40 has an inlet 41 and an outlet 42 for said second fluid.

Figures 6 and 7 illustrate the circulation of said second fluid inside the thermoelectric assemblies 22, 22 '. The inlet of the second fluid is via the inlet 41; said second fluid circulates, thanks to the circuit 40, inside the thermoelectric assemblies 22, 22 'of the modules 20. It leaves said circuit 40 by the output 42.

More precisely, the second fluid circulates inside the thermoelectric assemblies 22, 22 'via the tubes visible in FIG. 5. Said tubes allow the second fluid to be guided in the thermoelectric elements 21. Said tubes open, in addition, in a part of the circuit 40 which has a annular shape for distributing / collecting the second fluid to / from the tubes.

It should be noted that the circuit 40 allowing the circulation of the second fluid inside said thermoelectric assemblies 22, 22 'is independent of that allowing the circulation of the first fluid on the outer contour of said thermoelectric elements 21.

Advantageously, here, the first fluid is a hot source and the second fluid is a cold source, by comparison.

FIG. 6 further illustrates the flow control device 50 configured to be positioned within said generator 10 so as to modulate the quantity of the first fluid flowing through said thermoelectric generator 10. This flow control device 50 is a valve.

In Figure 6, said valve 50 is shown in the open position.

Said valve 50 therefore allows the first fluid to pass without forcing it to pass through the thermal modules 20 distributed radially around the Y axis of said thermoelectric generator 10.

Figure 7 illustrates the valve 50 in the closed position.

Said first fluid which then circulates inside the duct 30 is forced to pass inside the thermal modules 20. More specifically, said first fluid enters through the inputs E of said thermal modules 20, licks the outer peripheries of the thermoelectric assemblies 22, then 22 ', following the guidance imposed by the casing 25 and leaves the thermal module or modules 20, to the collector 32 which guides it outwards, or to the exhaust.

In other words, the duct 30 is provided with a bypass valve 50 at one of its ends and said valve makes it possible to force, in the closed position, a radial flow of the first fluid towards the thermal modules 20. In case of loss of load too large, this valve 50 may be partially or fully open so as not to impede the rectilinear flow of the first fluid in the conduit 30 (see Figure 6). Advantageously, the thermoelectric generator 10 is configured to be positioned in a motor vehicle exhaust line so that the exhaust gases flowing in said line define said first fluid and / or in a recirculated vehicle exhaust gas circuit. automobile so that said recirculated exhaust gas flowing in said circuit defines said first fluid.

Claims

claims

Thermoelectric generator (10) comprising at least one thermal module

(20), said thermal module (20) comprising thermoelectric elements

(21) in an annular form so as to form a substantially cylindrical thermoelectric assembly (22) when arranged side by side, said thermal module (20) being composed of at least one thermoelectric assembly (22) and a guide casing (25) configured to conduct a first fluid to conform to the outer contour of said one or more thermoelectric elements (21), said generator (10) comprising a plurality of said thermoelectric modules (20) arranged about an axis principal (Y), said generator axis (Y).

Thermoelectric generator (10) according to the preceding claim, wherein said module (20) comprises two of said thermoelectric assemblies

(22).

A thermoelectric generator (10) according to any one of claims 1 or 2, wherein said envelope (25) has an inlet (E) and an outlet (S) for said first fluid, said inlet (E) and / or said outlet (S) being formed of an elongated slot.

Thermoelectric generator (10) according to the preceding claim, wherein said casing (25) comprises cylindrical housings (24, 24 '), each housing (24, 24') accommodating one of said sets (22, 22 ').

Thermoelectric generator (10) according to the preceding claim, wherein said housings (24, 24 ') are arranged tangentially to each other.

A thermoelectric generator (10) according to any one of claims 4 or 5, wherein said inlet (E) and said outlet (S) are substantially located at a common plane of symmetry of said housings (24, 24 ').

The thermoelectric generator (10) according to any one of the preceding claims, wherein said thermoelectric elements (21) are provided with external fins.

The thermoelectric generator (10) according to any one of the preceding claims, wherein said assembly (22) is configured so that the first fluid forms a heat source, hot, of a temperature gradient.

The thermoelectric generator (10) according to any of the preceding claims, further comprising a conduit (30) configured to circulate said first fluid along said generator axis (Y), said conduit (30) having a communication, said contact zone, with the guide casings (25) of said thermal modules (20), said contact zone allowing the passage of said first fluid from said duct (30) to said casings (25).

10. thermoelectric generator (10) according to the preceding claim, further comprising a collector (32) for the first fluid output of said envelopes (25), said collector (32) opening downstream of said contact zone.

1 1. A thermoelectric generator (10) according to any one of the preceding claims, further comprising a circuit (40) adapted to circulate a second fluid within the thermoelectric elements (21), said second fluid forming a second heat source.

The thermoelectric generator (10) according to any one of the preceding claims, further comprising a flow control device (50) configured to be positioned within said generator (10) so as to modulate the amount of the first fluid flowing through said thermoelectric generator (10).

13. Thermoelectric generator (10) according to the preceding claim, wherein said flow control device (50) is a valve (50).

A thermoelectric generator (10) according to any one of the preceding claims configured to be positioned in a motor vehicle exhaust line so that exhaust gas flowing in said line defines said first fluid and / or in a circuit motor vehicle recirculated exhaust gas such that said recirculated exhaust gas flowing in said circuit defines said first fluid.

15. Thermal module (20) for a thermoelectric generator (10) according to any one of the preceding claims.