The invention relates to a thermoelectric generator for converting heat of a hot gas flow into electric energy, a rail vehicle comprising a thermoelectric generator of this kind, and a method for producing a thermoelectric generator of this kind.
For example, DE 10 2009 058 550 A1 discloses the use of a thermoelectric generator in an exhaust gas line of a combustion engine. In this way, heat of the exhaust gas flow can be converted into electric energy. A thermoelectric module of the generator having a plurality of thermoelectric elements connected in series, which are arranged between a high-temperature side and a low-temperature side, is disposed in each case between a module housing plate on the high-temperature side and the low-temperature side. The module housing plates are part of a module housing which completely surrounds the thermoelectric elements and a flexible compensating element. Damage and soiling of the thermoelectric elements are to be prevented by the completely encapsulated module thus created.
WO 2011/107282 A1 describes a device for utilising exhaust gas heat in combustion engines of motor vehicles. A housing through which exhaust gas passes has an inlet and an outlet for an exhaust gas flow. A plurality of thermoelectric modules are mounted heat-conductively on the housing. The modules extend through openings of a pipe portion and thus protrude both into a flow channel of the housing and into a cooling gas flow outside the housing. Heat conducting fins can be provided to improve the thermal coupling of the thermoelectric modules.
The invention is not limited to the use of a thermoelectric generator in an exhaust gas line of a combustion engine, for example of a diesel engine of a railway locomotive. Rather, the hot gas flow can also be a gas flow other than an exhaust gas flow, for example in an industrial production and/or processing facility or a thermal power plant (for example a CHP unit). In particular, it is also possible that the hot gas flow is coupled via a heat exchanger to an exhaust gas flow, for example of a combustion engine, or to another heat flow, and therefore the heat from the heat flow is transferred via the heat exchanger into the hot gas flow, which flows along the high-temperature side of the thermoelectric generator. In this variant the hot gas flow would function as a heat transfer medium between, for example, the exhaust gas flow or generally a hot heat source and the high-temperature side of the thermoelectric generator.
A problem for thermoelectric generators is the thermal expansion and thermal contraction during the course of the thermal cycles, these being caused by load changes of the combustion engine or generally of the hot heat source and starting in each case with the heating of the thermoelectric generator at start-up and ending with the cooling of the thermoelectric generator at the end of the operation. The device described in WO 2011/107282 A1 for exhaust gas heat utilisation, due to the accommodation of the thermoelectric modules in openings of the housing wall, indeed allows a constraint-free thermal expansion in the direction of the temperature gradient which runs from the outside of the housing into the housing interior. However, thermally induced constraints of the thermoelectric modules occur transversely to the direction of the temperature gradient.
A further problem is the efficiency of the conversion of heat into electric energy. Besides the choice of the materials for the thermoelectric elements, the effective temperature difference is of importance. The efficiency is great when the temperature difference between the high-temperature side and the low-temperature side of the thermoelectric module is great. During operation, only some of the heat on the high-temperature side is converted into electric energy. Another portion of the heat heats the thermoelectric module not only on the high-temperature side, but also on the low-temperature side, even if only to a smaller extent. For this reason, the housing of the device from WO 2011/107282 A1 is cooled on its outside.
In spite of the cooling, a temperature difference is produced for example in stationary conditions with constant hot gas flow and constant cooling fluid flow in the thermoelectric module, which temperature difference is much smaller than the temperature difference between the hot gas flow and cooling fluid flow. The distance between the contact of the material pair on the high-temperature side and the contact of the material pair on the low-temperature side is often only a few millimetres in practice.
In addition to the usable heat flow on the high-temperature side of the thermoelectric module, some of which can be converted into electric power, parasitic heat flows are produced between the high-temperature side and the low-temperature side and flow past the thermoelectric module. These parasitic heat flows are transferred on the one hand via the gas space in the environment of the thermoelectric modules by heat conduction, convection and heat radiation, and on the other hand via solid body heat bridges between high-temperature side and low-temperature side. These solid body heat bridges, in thermoelectric generators other than those described in WO 2011/107282 A1, are formed for example by supporting structures intended to keep the mechanical loading of the thermoelectric modules low.
Yet another problem of the use of thermoelectric modules having a plurality of thermoelectric elements, in particular connected in series, is the sensitivity of the thermoelectric modules with respect to components of the hot gas flow. The use of semiconductor materials for the thermoelectric elements is usual. However, carriers, in particular board-like carriers, of the thermoelectric elements can be sensitive with respect to components of the hot gas flow. This is the case for example if surface regions of the thermoelectric module are copper-plated. In particular, particles in the exhaust gas flow, but also other components, such as sulphur, can damage the surfaces of the thermoelectric module by chemical reactions.
One object of the present invention is to describe a thermoelectric generator for converting heat of a hot gas flow into electric energy, which thermoelectric generator enables a conversion of the heat in the hot gas flow into electric energy with high efficiency, enables a high number of thermal cycles without damage or destruction of thermoelectric modules by mechanical constraints, and protects thermoelectric elements and/or modules against components of the hot gas flow. A further object is to describe a rail vehicle comprising a thermoelectric generator of this kind, and a method for producing a thermoelectric generator of this kind.
In accordance with a basic concept of the present invention, a heat exchanger is used which transfers heat from the hot gas flow to the particular thermoelectric module. An example of a heat exchanger of this kind is the heat conducting fin mentioned in WO 2011/107282 A1, which extends from the thermoelectric module into the hot gas flow. Generally, a part (heat conducting body) made of solid material which in particular has the greatest possible coefficient of heat conduction is preferred as heat exchanger. An example of such a material is aluminium.
In addition, a seal is used which can also be referred to as an area divider. This seal separates the area through which the hot gas flow flows from an area disposed between the area for the hot gas flow and the low-temperature side of the particular thermoelectric module. This separated area contains a portion of the at least one heat exchanger, but also gas and/or a heat-insulating material. Both in the case of gas and of heat-insulating material, the hot gas in the gas flow is prevented from coming directly into contact with the low-temperature side of the thermoelectric module. The seal therefore prevents this contact. In the case of a heat-insulating material, the surface thereof facing the hot gas flow can be referred to as a seal. In the case that the area separated off by the seal contains gas, in particular exclusively gas, and contains a portion of the heat exchanger, the seal can be planar or layer-like or sheet-like for example, that is to say the dimension of the seal in the direction in which the heat exchanger transfers the heat from the hot gas flow to the thermoelectric module is smaller than the dimensions of the seal in the directions transverse to the direction of heat exchange of the heat exchanger. In this case, the seal can also be said to be wall-like, since it separates the area for the hot gas flow from the area with gas.
The seal can be made for example of a closed or of a porous material. If the seal is made of porous material or comprises porous material, it is then preferred that the flow resistance of a flow of gas through the seal is much greater than the flow resistance of the hot gas flow.
The seal is preferably made of a flexible material. This means that mechanical forces acting thereon lead to a deformation of the seal. Merely small and preferably negligible forces are therefore transferred to the thermoelectric module via the seal, and the thermoelectric module together with the heat exchanger can expand and contract in a constraint-free manner during the above-mentioned thermal cycles.
A nonwoven or woven material formed of fibres is particularly preferred as material of the seal, wherein the nonwoven or woven material is optionally combined with at least one further, preferably likewise flexible material, for example a coating of the individual fibres and/or of the nonwoven or woven material. Due to their temperature resistance even at high gas flow temperatures up to some 100° C. or above, mineral fibres, in particular synthetic mineral fibres, are well suited for producing the nonwoven or woven material.
In particular, the seal can be passed through at least at one point by the heat conducting body or one of the heat conducting bodies or by the thermoelectric module. Alternatively or additionally, parts of the seal are separated from one another at least at one point by the heat conducting body or one of the heat conducting bodies or by the thermoelectric module, that is to say the different parts of the seal extend on mutually opposed sides of the heat conducting body or thermoelectric module, wherein the connection of the mutually opposed sides runs along the flow direction of the hot gas flow. In particular, it is possible in this way that a plurality or multiplicity of heat conducting bodies or of protrusions of at least one heat conducting body extends through the seal and/or between different parts of the seal, more specifically in a direction running from the low-temperature side of the thermoelectric module into the hot gas flow, transversely to the flow direction thereof, or vice versa. During operation of the thermoelectric generator, a heat flow can therefore take place through the heat conducting body to the thermoelectric elements, whereas the seal on different sides of the heat conducting body separates the area for the hot gas flow from the area between seal and low-temperature side of the thermoelectric module.
The at least one heat conducting body has a free end within the area for the hot gas flow, and the hot gas flow can flow around said free end on all sides with the exception of the side in the direction of the extent of the heat conducting body to the low-temperature side of the thermoelectric module, and the hot gas also flows around said free end during operation. In particular, protrusions formed by the heat conducting body or by a plurality of the heat conducting bodies can therefore extend into the gas channel forming the area for the flow of the hot gas. For example, the protrusions can be formed as fins of a heat exchanger for transferring the heat of the hot gas flow to the thermoelectric module. For example, it is thus possible that a one-part heat conducting body forms a plurality of protrusions and in particular a plurality of fin-like protrusions. Alternatively or additionally, different heat conducting bodies can each form at least one protrusion, in particular a fin-like protrusion.
The free end is not in contact with other solid bodies. Thus, no mechanical forces are exerted onto the free end and the heat conducting body by thermal expansion and contraction, and therefore no constraints of the thermoelectric module occur.
Depending on the type of heat conducting body, but also depending on the materials of the thermoelectric module, in particular depending on the heat conductivity and any need for protection against harmful components of the hot gas flow, the seal can be positioned at different positions in the direction of the heat conduction through the heat conducting body. For example, the seal can be positioned on a portion of a protrusion formed by the heat conducting body, so that the protrusion passes through the seal and/or separates different parts of the seal from one another. However, it is also possible that the seal is positioned in the region of the fixed end of the heat conducting body, that is to say in the region in which the different materials of the thermoelectric elements of the thermoelectric module are in contact with one another on the high-temperature side of said thermoelectric module. It is additionally possible that the seal is arranged in a position between the contact region of the material pair on the high-temperature side and the contact region of the material pair of the thermoelectric generator on the low-temperature side. In this case, the contact region of the material pair of the thermoelectric module lies in the area through which the hot gas flows.
Put more generally, however, it is preferred that in the case of thermoelectric elements which each have a pair of different materials which are in contact with one another in a first contact region on the low-temperature side and are in contact with one another in a second contact region on the high-temperature side, so that an electrical voltage is produced between the first and the second contact region on account of a higher temperature in the second contact region than in the first contact region, the first contact region is disposed in the area separated by the seal from the gas channel. It is also preferred that the second contact region is likewise disposed in the area separated by the seal from the gas channel. However, the seal is preferably disposed close to the second contact region. In particular, the distance of the second contact region from the seal in the direction of the extent of the heat conducting body to the free end thereof in the gas channel is preferably at most a tenth and in particular at most a twentieth of the length of the heat conducting body from the position of the seal to the free end in the gas channel or, in another case, of the length of the end region of the thermoelectric module starting from the position of the seal plus the length of the heat conducting body to the free end thereof in the aforementioned direction in which the heat transport takes place.
It has already been mentioned that the seal can extend between different protrusions of the heat conducting body or a plurality of the heat conducting bodies, or that parts of the seal can extend therebetween. In this case, but also in other cases, the seal can extend from the heat conducting bodies or from one of the heat conducting bodies to a gas channel wall or to a supporting part of the thermoelectric generator, for example to a housing part of the thermoelectric generator. A supporting part is understood to mean a part of the generator which has any kind of supporting function. This can be the function of supporting the thermoelectric module and/or supporting another part of the thermoelectric generator. In particular, the supporting part can be connected to a heat sink for cooling the thermoelectric module. Although the seal extends to the supporting part, it is preferably not fixedly connected to the supporting part. This prevents the constraint, that is to say the transfer of mechanical forces from the supporting part to the thermoelectric module or vice versa to a significant extent.
With regard to the invention, it is preferred to use a cooling medium with high heat capacity to transport heat away from the heat sink, in other words liquids such as water are preferred compared to gases.
The area separated by the seal from the gas channel can optionally comprise an inlet and an outlet separately from the gas channel, through which inlet and outlet a flushing fluid (preferably a flushing gas) for flushing the area can be admitted and discharged during and/or after operation of the thermoelectric generator. A separate inlet and outlet are understood to mean that the flushing fluid can be admitted into and discharged from the area without flowing through the gas channel. This makes it possible to clean the area, in particular of residues or parts that pass or have passed from the gas channel into the area on account of a leak of the seal. In particular if soot particles also pass through the gas channel during operation, flushing in particular during operation of the thermoelectric generator, but also beforehand and/or thereafter, is advantageous. If the flushing fluid flows through the separated area during operation, said fluid can be for example a gas (for example air), which flows through the area at a higher pressure than the pressure of the gas in the hot gas flow. This prevents a portion of the hot gas flow from passing into the flushed area, since the pressure in the flushed area is higher.
In accordance with a further fundamental concept of the invention, the thermoelectric generator has a heat sink which serves to cool the thermoelectric module. In particular, a cooling fluid, preferably a cooling liquid, flows through the heat sink, so that an effective cooling of the heat sink and therefore of the thermoelectric module takes place. The heat sink is in contact with the thermoelectric module on a low-temperature side of the thermoelectric module. Of course, the thermoelectric generator can have a plurality of thermoelectric modules, which are in contact with the same heat sink and/or on the low-temperature side thereof are in contact with separate, different heat sinks.
In particular, the following is proposed: a thermoelectric generator for converting heat of a hot gas flow into electric energy, wherein the thermoelectric generator comprises:
Furthermore, the scope of the invention includes a rail vehicle comprising a thermoelectric generator in one of the embodiments of the thermoelectric generator disclosed in this description, the claims, and the drawing, wherein the rail vehicle has a combustion engine and the thermoelectric generator is arranged in an exhaust gas tract of the engine or is thermally coupled to the exhaust gas tract.
The following is additionally proposed: a method for producing a thermoelectric generator for converting heat of a hot gas flow into electric energy, comprising the following steps:
In practice, the seal does not completely seal the area with respect to the gas channel, as is generally also not the case with any type of seals. For example at contact points between the seal and the heat conducting body and/or the thermoelectric module, a passage of hot gas into the area can be possible. In any case, however, the seal causes a separation between the area and the gas channel hindering or even almost completely preventing entry of hot gas into the area.
It is preferred that the heat sink supports the thermoelectric module. It is therefore possible to dispense with supporting structures and thus solid body heat bridges between the high-temperature side and low-temperature side of the thermoelectric modules, so that the parasitic heat flows remain small and the temperature difference over the thermoelectric modules is as close as possible to the temperature difference between a hot gas flow and cooling fluid.
In particular in vehicles, for example rail vehicles, the space available for combustion engines and in the underfloor region is already well utilised. There is thus no, or little additional space available for the thermoelectric generator. This is also the case for any additional exhaust gas heat exchangers for transferring exhaust gas heat to a separate hot gas flow from the exhaust gas heat exchanger to the thermoelectric generator, and/or a separate cooling for cooling the thermoelectric generator. The same is true for additional weight, which shall be as low as possible. For this reason alone, systems without additional circuits for the hot gas flow are preferred in vehicles.
In particular for the use in vehicles, but also generally, it is therefore preferred to well utilise the installation space for the thermoelectric generator by providing or using a plurality of heat conducting bodies which extend from different sides of the gas channel for the hot gas flow into the gas channel and have a free end there. For example, a first group of a plurality of heat conducting bodies or protrusions can extend in the manner of a comb into the gas channel from one side thereof and a second group of heat conducting bodies or protrusions can extend in the manner of a second comb from another side into the gas channel, so that individual protrusions of the first comb extend into gaps between protrusions of the second comb and vice versa. The protrusions of the different combs are interlaced with one another.
In particular, the two combs can extend into the gas channel from opposite sides, so that free ends of protrusions of the first comb are disposed between protrusions of the second comb, and vice versa. In particular, the protrusions of the first comb and of the second comb form walls of flow channels for the hot gas flow, i.e. these flow channels jointly and optionally with additional flow channels form the overall cross-section available for the flow of hot gas. Transversely to the flow direction along the opposite sides from which the protrusions of the two combs extend into the gas channel, the protrusions of the first comb and the protrusions of the second comb follow one another in alternation. In all cases, however, it is preferred that the protrusions of the first comb and the protrusions of the second comb do not contact one another.
Not only in the case of the previously described comb-like groups of protrusions, but generally in the case of a plurality of protrusions which extend into the interior of the gas channel and supply heat to at least one thermoelectric module, it is preferred that the plurality of the protrusions form flow channels in particular as already described or in another way, which flow channels jointly contribute to the overall flow cross-section of the gas channel. The individual flow channels therefore have a smaller flow cross-section than the overall gas channel. This leads to a sound-damping property, so that the thermoelectric generator can be used in particular as an exhaust gas sound damper in the exhaust gas flow of a combustion engine. This in turn makes it possible to replace an existing exhaust gas sound damper or an exhaust gas sound damper also existing in systems of the same type by the thermoelectric generator. There is thus no need for any additional installation space, or only little additional installation space is required. The same is true for the additional weight.
Regardless of the possibility to form the plurality of individual flow channels, it is preferred that the thermoelectric generator comprises an arbitrary combination of the following features:
The hydraulic connection of a plurality of cooling channels of the heat sink or of the heat sinks is well known to a person skilled in the art and will not be described here in greater detail. The same is true for the electrical connection of a plurality of thermoelectric modules or basic units. The electrical connections to the thermoelectric modules can be disposed in particular in the area separated by the seal from the gas channel. In this way, the electric connections are protected against particularly high temperatures at the level of the temperature of the hot gas flow.
Instead of the strip-like thermoelectric modules already mentioned above as an example, block-like, in particular cuboid, thermoelectric modules can be used. In particular, these block-like modules on the low-temperature side can comprise a flat surface, enabling a thermal coupling over a large area to the associated heat sink. Alternatively or additionally, at least one block-like thermoelectric module can have a flat surface on the high-temperature side, which flat surface enables a large-area coupling of one or more heat sinks, wherein each heat sink can have a plurality of protrusions, which extend into the gas channel. In this case, the seal is disposed in a position, as viewed from the low-temperature side of the module, on the other side of the high-temperature side of the module, that is to say in the region of the protrusions of the heat sink or heat sinks.
In particular, a plurality of the block-like modules can be thermally coupled to a common heat sink, for example arranged in a rectangular grid.
Alternatively or additionally to the arrangement of a seal between the individual protrusions of the heat conducting body, a seal can be arranged between various arrangements formed of at least one block-like thermoelectric module and a heat conducting body thermally coupled thereto. In this case as well, the seal separates the gas channel from an area between gas channel and low-temperature side of the various block-like thermoelectric modules.
Alternatively to the heat conducting bodies having a plurality of protrusions, which for example can be produced by extrusion or milling, the individual, for example fin-like, heat conducting bodies already mentioned can also be used. In all these cases, protrusions, for example fins, which extend into the gas channel in a comb-like manner from opposite sides thereof, can be interlaced with one another, that is to say the protrusions from one side alternate with protrusions from the other side.
Individual fins can have an L- or T-shaped cross-section in the case of block-like thermoelectric modules, so that in particular a short limb of the L or T is connected on the high-temperature side to the block-like thermoelectric module.
Generally, for all aforementioned connections of parts and also for the connections yet to be described hereinafter, different joining techniques can be used, in particular adhesive bonding, welding, soldering, frictionally engaged joining and/or positively engaged joining.
In the case of block-like thermoelectric modules, thermally induced curvatures may occur at the surfaces, so that in particular the large-area contact with the heat sink and/or the heat conducting body is worsened. In order to solve this problem, it is proposed to arrange flat compensation elements, for example elastic compensation elements, between the heat sink and the module and/or between the module and the heat conducting body.
Depending on the embodiment of the seal, this damps to a greater or lesser extent mechanical vibrations which can be excited, in particular in the case of an exhaust gas flow, in the exhaust gas tract of a combustion engine. In particular, fin-like heat conducting bodies are capable of vibration. Although the seal or the parts of the seal is/are preferably flexible, the forces necessary to deform the seal can nevertheless damp mechanical vibrations. In particular, the stiffness and/or strength of the seal can be matched to the anticipated frequencies of mechanical vibrations in order to damp vibrations at these frequencies particularly well. The same is true for mechanical vibrations which can be excited other than by an exhaust gas flow. For example, vibrations of a combustion engine can be transferred via mechanical contacts on the thermoelectric generator.
The at least one heat sink can be made in particular from a metal, preferably a metal with a high heat conductivity, for example aluminium, an aluminium alloy, a copper alloy, or carbon steel.
The heat sink can be produced from a material block, for example by milling and drilling. The channels for the cooling fluid and the connections can be produced in this way. Alternatively, the heat sink can be produced as an extruded hollow profile. A further variant is the production in a casting method. It is also possible to produce, for example to weld, the heat sink from individual parts, for example profiles, tubes and plates. A further possible production method for the heat sink is additive manufacturing (generally known as “3D printing”). In particular in the case of milled, cast, welded or additively produced heat sinks, the surface pointing towards the low-temperature side of the thermoelectric module can be formed as a flat surface. In particular, the mechanical and thermal connection between heat sink and module can be produced via at least one additional connection element. Alternatively, the heat sink can be produced on the side pointing towards the at least one thermoelectric module with protrusions, for example fin-like protrusions, to which individual thermoelectric modules, in particular strip-like modules, are secured. Block-like and in particular cuboid modules can be secured directly on a planar surface of the heat sink, optionally with compensation elements for compensation of thermal deformation of the planar surface. In particular in the case of a heat sink formed from extruded hollow profiles and in the case of cast, welded or additively manufactured heat sinks, the surface for the connection to the at least one module can be subject to secondary processing (for example material can be removed by machining), before the at least one block-like module is secured to the surface. Surfaces of the material of the heat sink, including inwardly lying surfaces at the edge of cooling liquid channels, can preferably be coated in order to make the material resistant to atmospheric oxygen, the cooling medium and/or components present in the hot gas.
Connection elements for mechanical and thermal connection of heat sink and thermoelectric modules can be produced in particular from the same materials as those mentioned above for the heat sink. The connection element and the heat sink preferably consist of the same material. Connection elements can be punched, sawn or cut from metal sheets and optionally bent or angled into a desired shape (for example with L- or T-profile). Connection elements can be joined to the heat sink for example by soldering, gluing or welding. Mechanical connections between connection elements and thermoelectric modules (in particular module strips) can be produced in particular by soldering or gluing.
As mentioned, thermoelectric modules can be, for example, strip-like or block-like, in particular cuboid. Modules of this kind are commercially available. Details regarding their structure and materials therefore are not described in greater detail in this description. In particular in order to enable soldering, the module can be produced on the low-temperature side and/or on the high-temperature side from a metal. This includes the possibility that the surface is metallised in the connection region to the connection element or heat conducting body. This is true both for strip-like and for block-like modules. Electrical insulation is preferably provided in the contact region between heat conducting body and module and/or between module and heat sink and connection element to the heat sink (alternatively between connection element and heat sink).
For the heat conducting body, which transfers heat from the hot gas flow to the thermoelectric module during operation, the same materials as mentioned above with regard to the heat sink are preferred. In the case of a thermoelectric module strip, the heat conducting bodies can be produced for example as strips of planar material (for example sheet metal strip) or undulating sheet metal strips. Here, the wave troughs in the gas channel extend preferably in the flow direction so as to obtain an increased surface, yet not significantly increase the flow resistance in the gas channel. Thereby, the undulating sheet metal strips, similarly to the straight sheet metal strips, can be arranged opposite one another and interlaced with one another in the gas channel. A plurality of fins or other protrusions protruding into the gas channel can be oriented for example with the aid of templates, moulds or other spacing tools so that a uniform distance is provided therebetween. The individual distance preferably should not deviate by more than 20% from the average distance between two protrusions. The strip-like or fin-like heat conducting bodies can be punched, cut or sawn from larger sheets or from strip-like material, as is already known per se.
In the case of block-like thermoelectric modules, the heat conducting bodies are produced for example by milling or extrusion as fin bodies. As mentioned, heat conducting bodies that are L- or T-shaped in cross-section can be produced alternatively, the short profile limb of which is connected over the greatest area possible to the surface of the block-like module. Alternatively, pin heat sinks can be used as heat conducting bodies, i.e. a plurality of pin-like protrusions extends into the interior of the gas channel. In particular, the heat conducting body can be connected to the module by soldering or gluing. A further possibility lies in producing the module already with protrusions for example in fin form or pin form on the high-temperature side. In this case, the connection of the module to an additional heat conducting body is spared.
A flexible seal, that is to say a seal that deforms under the action of external forces, can be made in particular of material that is already flexible prior to production or that becomes flexible as a result of the production. For example, cavities can be produced during the production of the seal which make the material flexible as a whole. However, a nonwoven material or a mat made of mineral fibres is preferred as seal. For example, a slot-like hole can be cut or punched into the nonwoven material or the mat. The shape of the hole is dependent on the cross-sectional shape of the heat conducting body that passes through or should pass through the seal at the hole. The sealing function between the seal and the heat conducting body is ensured preferably by the friction of the two parts. Without this friction, the seal could move relative to the heat conducting body, and the sealing function could be worsened. A further possibility lies in the fact that free ends of heat conducting bodies extending from an opposite side of the gas channel into the gas channel hold the seal in position, i.e. the seal cannot move further in the direction of the opposite side of the gas channel. Alternatively or additionally, the seal can be held for example by a mount on an edge termination element of the gas channel and/or can be held on a reinforcement structure, and at least the freedom of movement of the seal can be limited in this way. Alternatively or additionally, the seal can be fixedly glued to the heat conducting body. A seal can not only separate the aforementioned area from the gas channel. Rather, at least one seal can also be used to seal the transition between modules, in particular the basic units, arranged in succession in the flow direction. The same materials as for the separating seal can be considered for this purpose. These seals can also be fixedly glued or held in position by clamping forces.
Exemplary embodiments of the invention will now be described with reference to the accompanying drawing. The individual figures of the drawing show:
The arrangement illustrated in
In the exemplary embodiment illustrated in
The strip-like thermoelectric elements, in the cross-section illustrated in
The thermoelectric elements 3a, 3b are connected in pairs to a fin-like heat conducting body 7a, 7b, for example again by adhesive bonding or soldering, on the high-temperature sides pointing towards the exhaust gas channel 6. The inner end regions of the thermoelectric elements 3a, 3b pointing towards the exhaust gas channel 6 enclose therebetween, in pairs, an end region of the heat conducting body 7a, 7b. The heat conducting body therefore mechanically stabilises the pairs of thermoelectric elements 3a, 3b in the same manner as the fins 4a, 4b.
The heat sinks 1a, 1b support the thermoelectric elements 3a, 3b via the fins 4a, 4b formed integrally on the heat sinks in the shown exemplary embodiment, and the thermoelectric elements in turn support the heat exchangers 7a, 7b. The total weight of the thermoelectric elements 3a, 3b and of the heat exchangers 7a, 7b is therefore supported by the heat sinks 1a, 1b.
A seal 2a, 2b made of flexible material, in the exemplary embodiment a nonwoven material formed of mineral fibres, runs close to the high-temperature side ends of the thermoelectric elements 3a, 3b. The heat exchangers 7a, 7b pass through the seal 2a, 2b, which is held by clamping forces and optionally by additional adhesive on the heat conducting bodies 7a, 7b. The heat conducting bodies 7a supported by the first heat sink 1a thus hold the seal 2a, and the second heat conducting bodies 7b supported by the second heat sink 1b hold the second seal 2b. The seals 2a, 2b are mat-like, i.e. they have two large-area surfaces, which are arranged on mutually opposed sides of the seal 2a, 2b. The outer of these surfaces faces towards the thermoelectric elements 3a, 3b and thus also the heat sink 1a, 1b, whereas the other of the large-area surfaces forms the wall of the exhaust gas channel 6.
Within the exhaust gas channel 6, the heat conducting bodies 7a, 7b, as has already been described, are interlaced with one another in a comb-like manner, that is to say in the cross-section of
As can be clearly seen from
Starting from the heat sink 1 in
The seals which are to be arranged one on the left and one on the right of the heat sink 1 illustrated in
The heat sink 1 in
In any case, it is preferred that the lower fastening protrusions 13 of the lowermost level of basic units 14 are fixedly connected to a housing (not illustrated in
Merely the lower supporting frame 41 is preferably fixedly connected to the stack of the basic units 14, whereas the upper supporting frame 31 merely limits the freedom of movement of the upper level of basic units 14 and enables a movement on account of thermal expansion and contraction. The cross-section through a heat sink 1 illustrated in
The second-lowest of the eight cooling liquid channels 5 running in parallel comprises an opening on the left in
The arrangement illustrated in
The flow direction of the exhaust gas channel 106 runs in the illustration of
Since
The undulating interlaced arrangement of the end portions of the heat conducting bodies leads to an increased surface of the heat conducting bodies compared to the shaping in
The surface of the end portions of the heat conducting bodies is increased based on the longitudinal portion, i.e. the quotient of the heat transfer coefficient and the length of the end portion in the longitudinal direction is greater. This makes it possible to choose the length of the end portion to be smaller and still attain a good transfer of heat from the hot gas to the heat conducting bodies. If the flow of the hot gas through the gas channel is not turbulent, the flow resistance is merely slightly higher than in the case of the straight embodiment of the end portions of the heat conducting bodies in
Number | Date | Country | Kind |
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10 2015 210 398.6 | Jun 2015 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2016/062689 | 6/3/2016 | WO | 00 |