This applications claims priority to German Patent Application No.: DE 10 2016 217 904.7 filed on Sep. 19, 2016, the contents of which are incorporated herein by reference.
The invention concerns a thermoelectric generator, in particular for a motor vehicle.
The term “thermoelectricity” is understood to mean the mutual influence of temperature and electricity and their interaction. Thermoelectric modules with, in each case, a plurality of thermoelectrically active elements, make use of this effect in order to generate electrical energy from waste heat as thermoelectric generators. The said thermoelectric elements consist for this purpose of thermoelectric semiconductor materials, which convert a temperature difference into a potential difference, that is to say, into an electrical voltage. In this manner, a heat flow can be converted into an electric current. The thermoelectric modules are based on the Seebeck effect. Within a thermoelectric module, p-doped and n-doped thermoelectric elements are interconnected. A plurality of such thermoelectric modules are usually connected to form a thermoelectric generator, which can generate an electrical current from a temperature difference in conjunction with a corresponding heat flow. Here it is of great importance to achieve the highest possible efficiency in order to convert heat to electrical energy as effectively as possible.
It is therefore an object of the present invention to demonstrate new ways of developing thermoelectric generators. In particular, a thermoelectric generator is to be created, which has a particularly high efficiency.
This object is achieved by the subject matter of the independent patent claims. Preferred embodiments are the subject matter of the dependent claims.
A thermoelectric generator in accordance with the invention, in particular for a motor vehicle, comprises a plurality of first and second stacking disks alternately stacked one upon another along a stacking direction. Both the first and the second stacking disks are designed in the form of a shell. In each case a first stacking disk and a second stacking disk, adjacent to the latter in the stacking direction, form a stacking disk pair. Each stacking disk pair bounds a gas path. In at least one intermediate space between two adjacent stacking disk pairs, a coolant path is formed, which is bounded by a tubular body. In accordance with the invention, the gas path is traversed by a gas with a temperature that has a higher value than a temperature of the coolant flowing through the at least one coolant path.
In at least one intermediate space between a gas path and a coolant path, a thermoelectric module with at least one thermoelectrically active element is arranged. The said thermoelectric module has a hot side, which is in thermal contact with the gas path adjacent to the stacking direction, and a cold side, which is in thermal contact with the coolant path adjacent in the stacking direction. This ensures a highly effective thermal contact of the thermoelectrically active elements with the gas flowing through the gas paths, as well as with the coolant flowing through the coolant paths. In this manner, a high efficiency of the thermoelectric generator can be ensured.
In a preferred embodiment, two stacking disk pairs adjacent in the stacking direction communicate with each other by means of at least one gas path connecting line, namely, which is in fact separated from the respective intermediate space between the two stacking disk pairs in terms of fluid flow. A variant in which two gas path connecting lines are arranged at a distance from one another is to be seen as particularly preferred. This enables a simple distribution of the gas to the existing gas paths as well as a simple collection of the gas after it has flowed through the individual gas paths. In particular, a single common inlet and a single common outlet are sufficient to introduce the gas into the gas paths and to remove the gas from the latter once again, since the distribution to the individual gas paths can take place via the said gas path connecting lines. In this embodiment, a first and/or second stacking disk of a particular pair of stacking disks has, for the design of the at least one gas path connecting line, a thermal expansion compensation dome protruding from the respective stacking disk and enclosing a passage opening. Such a thermal expansion compensation dome also possesses the second and first stacking disks of the pair of stacking disks adjacent in the stacking direction. In this manner, the two thermal expansion compensation domes adjacent in the stacking direction bound the respective gas path connecting line between the stacking disks adjacent in the stacking direction.
Expediently, at least one thermal expansion compensation dome is designed such that it compensates for thermally induced expansions of the material of the stacking disk pairs, in particular in the stacking direction. If the stacking disks of the stacking disk pairs extend in the stacking direction because of the high temperature of the hot gas flowing through the gas path, this thermal expansion in the stacking direction can be compensated for by the thermal expansion compensation domes. In this manner, any damage to the structure of individual components of the thermoelectric generator due to thermal expansion of the stacking disk pairs is prevented. A gap is also prevented from forming between the thermoelectric modules and the stacking disks adjacent to them, which gap would reduce the contact of the gas path with the hot side.
In an advantageous development, at least one thermal expansion compensation dome has a collar-like peripheral wall protruding from the stacking disk in the stacking direction, which encloses the said passage opening. Particularly preferably, the peripheral wall tapers away from the stacking disk along the stacking direction. This permits a simple, yet mechanically robust, configuration of the respective gas path connecting lines.
In order to achieve a durable, fluid-tight connection, it is advisable to connect adjacent thermal expansion compensation domes in the stacking direction with one another in a material bond. A brazed joint, which can be produced in a simple manner for all existing thermal expansion compensation domes in a brazing furnace, proves to be particularly advantageous.
In another preferred embodiment, the thermal expansion compensation domes adjoining the gas path connecting line in the stacking direction are connected directly or indirectly, specifically by means of a connecting tubular body. The first variant is structurally particularly simple and thus particularly cost-effective to implement. The latter variant is structurally somewhat more complex to implement, but in particular permits a flexible determination of the distance between two adjacent pairs of stacking disks. Particularly preferably, such a connecting tubular body is designed as a hollow cylinder, which can be connected to the two associated thermal expansion compensation domes in a material bond, preferably by means of a brazed joint.
Particularly preferably, a ribbed structure is provided between the first and second stacking disks of at least one pair of stacking disks, which is supported on the first and second stacking disks. In this manner, the pairs of stacking disks can be mechanically stiffened. At the same time, the active cross-sectional area of the respective stacking disks is improved with the gas flowing through the pairs of stacking disks.
Particularly preferably, at least two second coolant paths, in particular at least two tubular bodies, are provided between two thermoelectric modules adjacent in the stacking direction, which are arranged adjacent to one another, preferably at a distance from one another, along the first longitudinal direction. These measures result in an improved thermal contact between the coolant flowing through the coolant paths and the thermoelectrically active elements, which increases the efficiency of the thermoelectric generator.
The first and second stacking disks are also particularly preferably designed as half-shells, which face each other so as to bound a gas path. This measure simplifies the production of the said stacking disks, which results in cost advantages, in particular if the first and second stacking disks are produced as identical parts.
Particularly preferably, at least one thermoelectric module has a plurality of thermoelectrically active elements, which are arranged in a grid-like manner at right angles to the stacking direction, and are connected to one another by means of electrical conductor elements, preferably made of copper. This ensures a highly effective thermal contact of the thermoelectrically active elements with the gas flowing through the gas paths, as well as with the coolant flowing through the coolant paths.
Particularly expediently, electrically insulating insulation can be arranged on an outer side of the first stacking disk of a pair of stacking disks facing away from the second stacking disk, and on an outer side of the second stacking disk of a pair of stacking disks facing away from the first stacking disk. In this manner, the electrical wiring required for the proper functioning of the thermoelectric module can be achieved between the individual thermoelectrically active elements. In particular, undesirable electrical short-circuits between the thermoelectrically active elements via the typically electrically conductive material of the stacking disks or the tubular bodies are avoided.
Particularly preferably, the electrical insulation is designed as an insulation layer or as an insulation film, in particular of a plastic material, which together with the electrical conductor elements is materially bonded to the stacking disk adjacent in the stacking direction. This allows a durable attachment of the electrical insulation or of the electrical conductor elements to the stacking plate, even if these are heated to temperatures of up to 600° C. or more during the passage of the hot gas.
Particularly preferably, at least a first stacking disk, as well as—alternatively or additionally—at least one second stacking disk, has a peripheral edge protruding in the stacking direction. This measure facilitates the attachment of the two stacking disks, preferably by means of material bonding, to form a gas path. The said edges also serve to compensate for any thermal expansion of the stacking disks that may arise.
In an advantageous further development, at least one tubular body forming a coolant path is designed as a flat tube whose tube height, measured along the stacking direction, is at most one-fifth, preferably at most one-tenth, of a tube width measured transversely to the tube height. In this manner, the space requirement of the thermoelectric generator in the stacking direction can be kept small.
In a further preferred embodiment, the rib-like structure is arranged laterally, that is to say, in a plane perpendicular to the stacking direction, essentially in the same region as the thermoelectrically active elements of the thermoelectric modules. In this manner, a particularly high stiffening of the thermoelectric generator in the region of the thermoelectrically active elements, which are particularly sensitive to mechanical pressure, is ensured.
In an advantageous further development of the invention at least one gas path extends along a first longitudinal direction, and at least one coolant path along a second longitudinal direction. In this variant, the second longitudinal direction extends transversely to the first longitudinal direction. Both longitudinal directions in turn run transversely to the stacking direction. This allows the gas to be introduced or discharged—typically by means of a gas inlet or gas outlet in a direction transverse to the introduction or discharge of the coolant—typically by means of a (second) coolant inlet or coolant outlet. The connections required for this purpose can therefore advantageously be positioned offset by 90° relative to one another.
Further important features and advantages of the invention ensue from the subsidiary claims, from the drawings and from the associated description of the figures with the aid of the drawings.
It goes without saying that the features mentioned above, and those that are still to be explained below, can be used not only in the respective combination specified, but also in other combinations, or in a single setting, without departing from the scope of the present invention.
Preferred examples of embodiments of the invention are illustrated in the drawings and are explained in greater detail in the following description, wherein like reference symbols refer to identical, or similar, or functionally identical, components.
In schematic representations:
In accordance with
For purposes of compensation for thermal expansion the first and second stacking disks 2a, 2b each have a peripheral edge 21a, 12b protruding in the stacking direction S. (cf.
In the intermediate spaces 6 between two adjacent gas paths 4 in the stacking direction S coolant paths 5 are provided, through which—separated in terms of fluid flow from the gas paths 4—a coolant can flow. The coolant paths 5 are bounded by respective tubular bodies 7. Thermoelectric modules 8 with thermoelectrically active elements 9 are also arranged in the intermediate spaces 6 between the gas paths 4 and the coolant paths 5. In the exemplary scenario, two thermoelectric modules 8 are provided in each intermediate space 6, between which at least one coolant path 5 is arranged in the form of a sandwich in the stacking direction S.
As can also be seen in
The coolant paths 5 as well as the gas paths 4 are also of longitudinal design—their channel length thus being at least three times, preferably at least five times their channel width—and they extend along a second longitudinal direction L2, which runs transversely to the first longitudinal direction L1. The tubular bodies 7 forming the coolant paths 5 can preferably be designed as flat tubes 25, whose tube height measured along the stacking direction S is at most one-fifth, preferably at most one-tenth, of a tube width measured transversely to the tube height.
The thermoelectric modules 8 in each case possess a hot side and a cold side. The hot side of a respective thermoelectric module 8 is in thermal contact with the gas path 4 adjacent in the stacking direction S. The cold side of the same thermoelectric module 8 is in thermal contact with the coolant path 5 adjacent in the stacking direction S. A gas flows through the gas paths 4 at a temperature that is higher than a temperature of the coolant flowing through the coolant paths 5. The resulting temperature difference between the hot side and the cold side causes the thermoelectric modules 8 to generate an electrical voltage.
In what follows, the focus is on what is being represented in
In accordance with
The thermal expansion compensation domes 14a, 14b, 15a, 15b are designed such that thermal expansion of the material of the stacking disk pairs 3, in particular in the stacking direction S, is compensated by them. If the stacking disks 2a, 2b of the stacking disk pairs 3 extend in the stacking direction S by virtue of the high temperature of the hot gas flowing through the gas paths 4, this thermal expansion in the stacking direction S can be compensated for by the thermal expansion compensation domes 14a, 14b, 15a, 15b. In this manner, any damage to the structure of individual components by virtue of the thermal expansion of the stacking disk pairs 3 in the stacking direction S is prevented.
The thermal expansion compensation domes 14a, 15a, and 14b, 15b, adjacent in the stacking direction S in each case bound a gas path connecting line 13a, 13b of adjacent stacking disk pairs 3 in the stacking direction S. Each thermal expansion compensation dome 14a, 14b, 15a, 15b comprises a collar-like peripheral wall 18, protruding from the respective stacking disk 2a, 2b in the stacking direction S, and enclosing the respective passage opening 16a, 16b, 17a, 17b. The peripheral walls 18 preferably taper along the stacking direction S away from the respective stacking disk 2a, 2b. For the formation of a respective gas path connection line 13a, adjacent thermal expansion compensation domes 14a, 14b, 15a, 15 in the stacking direction S are materially bonded with one another, preferably by means of a brazed joint.
In an analogous manner to the first stacking disk 2a, thermoelectrically active elements 9 with electrical conductor elements 22 and electrical insulation 23 are also arranged on the second stacking plate 2b (not shown in
Referring once again to
Number | Date | Country | Kind |
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10 2016 217 904.7 | Sep 2016 | DE | national |