DE102012216041B4 - Device for converting thermal energy into electrical energy - Google Patents

Abstract

Device for converting thermal energy into electrical energy, comprisingat least one thermoelectric module (19) which has a warm side (20) provided for contact with a heat source and a cold side (22) provided for contact with a heat sink,a heating channel (11) through which a hot fluid can flow and which is in thermally conductive connection with the warm side (20) of the thermoelectric module (19), anda cooling channel (25) through which a cooling fluid can flow and which is in thermally conductive connection with the cold side (22) of the thermoelectric module (19),wherein the cooling channel (25) has at least one opening (55) facing the cold side (22) of the thermoelectric module (19) and/or the heating channel (11) has at least one opening facing the warm side (20) of the thermoelectric module (19),wherein a seal (40) enclosing the opening (55) made of an elastic material is applied to a the cold side (22) of the thermoelectric module (19) and/or a side of the heating channel (11) facing the warm side (20) of the thermoelectric module (19), wherein the seal (40) comprises a border section (41) which runs completely around an outer edge region of the side of the cooling channel (25) and/or the heating channel (11),characterized in that the seal (40) further has at least one channel separating section (42) which extends between two parallel channel sections (52) of the cooling channel (25) and/or the heating channel (11),wherein the border section (41) has a greater thickness than the channel separating section (42).

Description

The present invention relates to a device for converting thermal energy into electrical energy, with at least one thermoelectric module which has a warm side provided for contact with a heat source and a cold side provided for contact with a heat sink, a heating channel through which a hot fluid can flow and which is in thermally conductive connection with the warm side of the thermoelectric module, and a cooling channel through which a cooling fluid can flow and which is in thermally conductive connection with the cold side of the thermoelectric module, wherein the cooling channel has at least one opening facing the cold side of the thermoelectric module and/or the heating channel has at least one opening facing the warm side of the thermoelectric module.

Such devices are also known as thermoelectric generators (TEGs) and are used in various ways to utilize waste heat. For example, thermoelectric generators can be used to utilize exhaust heat in combustion engines by converting part of the thermal energy of the hot exhaust gas flow into electrical energy and feeding it into the vehicle's electrical system, ultimately saving fuel. In addition to the efficiency of the thermoelectric module, the key to achieving the greatest possible yield of electrical energy is the greatest possible temperature difference between the heat source and the heat sink.

Heating channels and/or cooling channels provided with one or more openings improve the heat transfer between the thermoelectric module and the corresponding heat transfer fluid, since the normally present channel wall is no longer present as an additional heat transfer resistance, at least in the area of the respective opening. Such openings therefore enable a higher overall efficiency in a thermoelectric generator. A thermoelectric generator with a cooling channel open to the cold side of the thermoelectric modules is in the WO 2012 / 079 662 A1 disclosed.

The object shown in the generic term WO 02 / 086 980 A1 discloses a thermoelectric cooler in which the thermoelectrically active material is covered on both sides by ceramic plates, with the fluid channels being open towards the plates.

In the JP 2001 004 245 A discloses a converter with a thermoelectric module, a metal plate and a half-shell-like channel body made of synthetic resin, wherein the metal plate is attached to one side of the thermoelectric module by means of a thermal paste.

In practice, however, it is difficult to operate thermoelectric generators with channel openings efficiently. A particular problem is that the surface of common thermoelectric modules always has certain unevenness due to the manufacturing process. This can lead to problematic leaks and leakage flows. To prevent these problems, the thermoelectric module can be housed in a housing that has a flat outer surface. However, this in turn increases the heat transfer resistance.

It is an object of the invention to improve thermoelectric generators with heating channel openings and/or cooling channel openings.

The problem is solved by a device having the features of claim 1.

A seal made of an elastic material that encloses the opening is applied to a side of the cooling channel facing the cold side of the thermoelectric module and/or to a side of the heating channel facing the warm side of the thermoelectric module. Such an elastic seal is able to compensate for unevenness on the surface of the thermoelectric module and tolerances in the channel wall, thus ensuring that the relevant channel is securely sealed in the area of the opening. The seal can in particular prevent crosstalk between different channel sections of the respective channel.

Furthermore, the seal comprises a border section which runs completely around an outer edge area of the side of the cooling channel and/or the heating channel. Such a border section seals the channel in question from the environment and reliably prevents undesired fluid leakage.

According to the invention, the seal has at least one channel separation section which extends between two parallel channel sections of the cooling channel and/or the heating channel. Such a channel separation section can prevent undesirable crosstalk between the parallel channel sections and thus further improve the heat transfer between the fluid and the thermoelectrically active surface.

Also according to the invention, the border section has a greater thickness than the channel separation section. This takes into account the fact that a stronger seal is required for the main sealing function against the environment than for protection against crosstalk.

Further developments of the invention are specified in the dependent claims, the description and the accompanying drawings. One embodiment of the invention provides that the side of the cooling channel facing the cold side of the thermoelectric module and/or the side of the heating channel facing the warm side of the thermoelectric module has at least one recess which at least partially accommodates the seal. Such a receptacle for the seal always ensures correct positioning and a secure fit of the seal.

The seal is preferably made of a heat-resistant material, the heat-resistant material preferably being resistant to a temperature of at least 80°C and particularly preferably to a temperature of at least 120°C. In many applications in the field of exhaust gas technology, this enables safe use on the cold side of the thermoelectric module, where the temperature of the flowing cooling fluid is usually around 100°C. For use on the warm side of the thermoelectric module, a higher heat resistance should be selected that corresponds to the respective media temperature, preferably up to a temperature of at least 300°C.

According to one embodiment of the invention, the seal is made of silicone. Silicone seals have proven to be particularly advantageous in the relevant field of application.

According to a further embodiment of the invention, a frame is provided for the thermoelectric module, the seal being arranged at least in some areas between the frame and the side of the cooling channel and/or the heating channel. Such a frame ensures correct positioning of the thermoelectric modules and electrical insulation between individual thermoelectric modules of a plurality of thermoelectric modules. The seal can also be arranged exclusively between the frame and the side of the cooling channel and/or the heating channel.

According to a further embodiment of the invention, the seal is formed by a section of the cooling channel itself, which is made at least in part from an elastic plastic, facing the cold side of the thermoelectric module. A cooling channel made of elastic plastic can make a separate elastic seal superfluous. According to a special embodiment, the entire cooling channel is made of an elastic plastic. Due to the elastic design, such a cooling channel can be placed directly on the surface of a thermoelectric module or a frame for a thermoelectric module, since any unevenness on the surface of the thermoelectric module and tolerances of the frame are compensated for by the elasticity of the channel material. In addition, the design of the cooling channel from plastic enables particularly cost-effective and simple production. Furthermore, a significant weight saving compared to a metal version is advantageous.

The cooling channel can be designed as a one-piece injection-molded component, which makes it particularly easy and cost-effective to manufacture. Reinforcing ribs and/or transverse stiffening ribs can be easily incorporated into a suitable injection-molded tool. In general, the design of the cooling channel as an injection-molded component enables particularly high design flexibility.

According to a further embodiment of the invention, the cooling channel is made of at least two different plastics injected into one another. This increases the flexibility with regard to the properties of the cooling channel even further.

In particular, the cooling channel can be made of a 2K material. 2K materials comprise two interlocking components of different types and enable the use of two different material properties in a one-piece component.

For example, the cooling channel comprises at least one section made of a hard plastic and at least one section made of an elastomer that forms the seal. The section made of hard plastic serves as a support element or carrier for the cooling channel, while the section made of the elastomer enables compensation for unevenness on the surface of the thermoelectric module and provides a seal for the open cooling channel.

One embodiment of the invention provides that the cooling channel comprises a base body made of a first plastic, with stiffening elements made of a second plastic that is harder than the first plastic being inserted into recesses in the base body. This enables a particularly simple construction of a multi-component plastic channel.

According to a further embodiment of the invention, an enclosure for the thermoelectric A module is provided, wherein the cooling channel and/or the heating channel is/are attached to the enclosure by means of at least one clamping element, preferably detachably. This facilitates the manufacture, assembly and, if necessary, maintenance of the device.

According to a special embodiment, the cooling channel and/or the heating channel is locked to the frame, in particular by means of a spring clamp connection. This can further simplify the assembly and, if necessary, replacement of the relevant channel.

Preferably, an electrical insulating layer is provided between the cold side of the thermoelectric module and the opening, which electrically separates the thermoelectrically active surface from the associated channel.

• 1 ist eine perspektivische Darstellung einer erfindungsgemäßen Vorrichtung zur Wandlung von Wärmeenergie in elektrische Energie, welche an einem Abgaskanal eines Verbrennungsmotors angebracht ist.
• 2 ist eine aufgeschnittene Teildarstellung der Vorrichtung gemäß 1.
• 3a ist eine Ansicht eines Kühlkanals der Vorrichtung gemäß 1 von unten.
• 3b zeigt die Lage einer Dichtung in der Ansicht gemäß 3a.

The invention is described below by way of example with reference to the drawing.

• 1 is a perspective view of a device according to the invention for converting thermal energy into electrical energy, which is attached to an exhaust duct of an internal combustion engine.
• 2 is a cutaway partial view of the device according to 1 .
• 3a is a view of a cooling channel of the device according to 1 from underneath.
• 3b shows the position of a seal in the view according to 3a .

According to 1 An exhaust duct 11 is used to guide a hot exhaust gas from a combustion engine (not shown) along a flow direction S into the atmosphere. The exhaust duct 11 has a rectangular, flattened cross-section and is divided into several sub-ducts 12. A flange 13 is provided on a front side of the exhaust duct 11 on the flow inlet side, which serves to connect the exhaust duct 11 to a preceding component of the associated exhaust line. A flange 13 is also provided on the front side of the exhaust duct 11 on the flow outlet side.

As can be seen from the sectional view of 2 , respective arrangements of thermoelectric modules 19 are provided on the top side 15 and on the bottom side 17 of the exhaust gas duct 11 in order to convert the thermal energy of the flowing exhaust gas into electrical energy. Each thermoelectric module 19 is aligned such that the warm side 20 intended for contact with a heat source faces the exhaust gas duct 11. On the opposite cold side 22 of each thermoelectric module 19, a cooling duct 25 is provided through which a cooling fluid, in particular water, can flow. Each cooling duct 25 is designed as a half-shell that is open on one side, ie the individual duct sections 52 have openings 55 that face the cold side 22 of the respective thermoelectric module 19. Each cooling duct 25 essentially completely covers the cold side 22 of the associated thermoelectric module 19. Thus, each cooling channel 25 is essentially completely open when viewed in the direction of the cold side 22 of the thermoelectric module 19.

Despite the openings 55, the cooling channels 25 are sealed from the warm sides 20 of the thermoelectric modules 19 because a seal 40 made of a high-temperature-resistant silicone is provided on the side of each cooling channel 25 facing the cold side 22 of the thermoelectric module 19.

As shown, the cooling channel 25 is attached by means of locking elements 47 to a grid-like, here thin-walled, enclosure 49 for the thermoelectric modules 19. The elastic seal 40 ensures a spring force directed in the locking direction of the locking elements 47.

To produce a device according to the invention, an arrangement of thermoelectric modules 19 is first cemented into a metal frame structure forming the enclosure 49. If necessary, an electrically insulating cover layer is sprayed onto the cold sides 22 of the thermoelectric modules 19. The half-shell-like cooling channels 25 are then placed on the enclosure 49 from the outside and latched into the locking elements 47 against the spring force of the elastic seal 40. In principle, the cooling channels 25 could also be glued onto the enclosure 49.

As from 3a and 3b As can be seen, the seal 40 is divided into a border section 41, which runs completely around an outer edge region of the cooling channel 25, and into a plurality of channel separation sections 42 running parallel to one another, each of which extends between the channel sections 52 of the cooling channel 25 arranged next to one another. Since the border section 41 provides the important main sealing function against the environment, it has a greater thickness than the channel separation sections 42. The border section 41 is positioned by a raised edge 43 of the enclosure 49. Similarly, the channel separation sections 42 are positioned by troughs 45, which are provided on the side of the cooling channel 25 facing the cold side 22 of the thermoelectric module 19. The troughs 45 accommodate the channel separation sections 42 of the seal 40. partially and thus ensure their correct positioning.

The seal 40 made of high-temperature-resistant silicone is applied in a pasty state to the cooling channel 25 automatically by means of a dosing unit. The thickness of the seal 40 is determined, for example, by the travel speed of the dosing unit. During production, a lower travel speed is therefore selected for the application of the border section 41 than for the application of the channel separation sections 42.

During operation of the device, the flowing cooling fluid, in particular water, comes into direct contact with the thermoelectric modules 19 in the individual channel sections 52 of the cooling channels 25, whereby, due to the openings 55, there is no channel wall between the cooling fluid and the thermoelectrically active surface. Undesired escape of cooling fluid is prevented by the seal 40.

In contrast to a seal 40 applied separately to the cooling channel 25, an elastic section of the cooling channel itself can also form a seal. In particular, the cooling channel can be made partially or completely from an elastic plastic. It has proven to be particularly advantageous to manufacture the cooling channel from a 2K material. Two different plastic materials are injected into one another in such a way that a one-piece component is produced. By using a hard plastic as a support material and an elastomer as a sealing material, a cooling channel with an integrated seal can be produced in a simple manner. With a 2K material, there is a positive connection between the two components, which is close to a material connection, so that a high level of stability can be achieved.

In the exemplary embodiment shown, the seals 40 are provided exclusively on the cold sides 22 of the thermoelectric modules 19. In principle, however, it is also possible for the exhaust gas duct 11 to have openings to the warm sides 20 of the thermoelectric modules 19 and for at least one seal analogous to the seals 40 to be provided on the warm side 20 of each thermoelectric module 19.

List of reference symbols

11

Exhaust duct

12

Subchannel

13

flange

15

Top

17

bottom

19

thermoelectric module

20

Warm side

22

Cold side

25

Cooling channel

40

poetry

41

Border section

42

Channel separation section

43

raised edge

45

trough

47

Locking element

49

Edging

52

Canal section

55

Opening

S

Flow direction

Claims (14)

Device for converting thermal energy into electrical energy, with at least one thermoelectric module (19) which has a warm side (20) provided for contact with a heat source and a cold side (22) provided for contact with a heat sink, a heating channel (11) through which a hot fluid can flow and which is in thermally conductive connection with the warm side (20) of the thermoelectric module (19), and a cooling channel (25) through which a cooling fluid can flow and which is in thermally conductive connection with the cold side (22) of the thermoelectric module (19), wherein the cooling channel (25) has at least one opening (55) facing the cold side (22) of the thermoelectric module (19) and/or the heating channel (11) has at least one opening facing the warm side (20) of the thermoelectric module (19), wherein a seal (40) enclosing the opening (55) made of an elastic material is applied to one of the cold sides (22) of the thermoelectric module (19) facing side of the cooling channel (25) and/or on a side of the heating channel (11) facing the warm side (20) of the thermoelectric module (19), wherein the seal (40) comprises a border section (41) which runs completely around an outer edge region of the side of the cooling channel (25) and/or of the heating channel (11), characterized in that the seal (40) further comprises at least one channel separation section (42) which extends between two parallel channel sections (52) of the cooling channel (25) and/or the heating channel (11), wherein the border section (41) has a greater thickness than the channel separation section (42). Device according to Claim 1 , characterized in that the side of the cooling channel (25) and/or the heating channel (11) facing the cold side (22) of the thermoelectric module (19) has at least one recess (45) which at least partially accommodates the seal (40). Device according to Claim 1 or 2 , characterized in that the seal (40) is made of a heat-resistant material, wherein the heat-resistant material is preferably resistant up to a temperature of at least 80°C and particularly preferably up to a temperature of at least 120°C. Device according to one of the preceding claims, characterized in that the seal (40) is made of a silicone. Device according to one of the preceding claims, characterized in that a frame (49) is provided for the thermoelectric module (19), wherein the seal (40) is arranged at least in regions between the frame (49) and the side of the cooling channel (25) and/or the heating channel (11). Device according to one of the preceding claims, characterized in that the seal (40) is applied to a side of the cooling channel (25) facing the cold side (22) of the thermoelectric module (19) and is formed by a section of the cooling channel (25) itself, which is made at least in regions from an elastic plastic, facing the cold side (22) of the thermoelectric module (19). Device according to Claim 6 , characterized in that the cooling channel (25) is made entirely of plastic. Device according to Claim 6 or 7 , characterized in that the cooling channel (25) is designed as a one-piece injection-molded component. Device according to one of the Claims 6 until 8th , characterized in that the cooling channel (25) is made of at least two different plastics injected into one another. Device according to one of the Claims 6 until 9 , characterized in that the cooling channel (25) is made of a 2K material. Device according to one of the Claims 6 until 10 , characterized in that the cooling channel (25) comprises at least one section made of a hard plastic and at least one section forming the seal made of an elastomer. Device according to one of the Claims 6 until 11 , characterized in that the cooling channel (25) comprises a base body made of a first plastic, wherein stiffening elements made of a second plastic which is harder than the first plastic are inserted into recesses in the base body. Device according to one of the preceding claims, characterized in that a frame (49) is provided for the thermoelectric module (19), wherein the cooling channel (25) and/or the heating channel (11) is fastened, preferably detachably, to the frame (49) by means of at least one clamping element (47). Device according to Claim 13 , characterized in that the cooling channel (25) and/or the heating channel (11) is locked to the frame (49), in particular by means of a spring clamp connection.

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