US3617390A

US3617390A - Thermogenerator having heat exchange elongated flexible metallic tube of wavy corrugated construction

Info

Publication number: US3617390A
Application number: US864282A
Authority: US
Inventors: Eugen Szabo De Bucs; Josef Winkler
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1966-06-08
Filing date: 1969-10-01
Publication date: 1971-11-02
Anticipated expiration: 1988-11-02
Also published as: GB1177844A; DE1539323A1

Abstract

A thermogenerator wherein a plurality of thermocouples are arranged with their high-temperature junctions situated in one row and with their opposed low-temperature junctions situated in a second row. A pair of elongated heat-exchangers respectively extend along these rows and engage the thermocouples at the junctions thereof. At least one of these heat-exchangers is in the form of an elongated hollow tubular structure for conveying along its interior a liquid heat-exchanging medium, and this one heat-exchanging structure has a plurality of rigid portions engaging the thermocouples and a plurality of intermediate flexible portions situated respectively between and operatively connected with the rigid portions. A spring means coacts with both of the heat-exchangers for urging them toward each other so as to maintain them pressing against the thermocouples.

Description

United States Patent [72] Inventors Eugen Szabo De Bucs 3,082,275 3/1963 Talaat 136/208 Erlangen; 3,178,895 4/1965 Mole et al.. 62/3 Josef Winkler, Nurnberg, both of Germany 3,208,877 9/1965 Merry 136/212 X [21] Appl. No. 864,282 3,269,874 8/1966 Moeller. 136/211 [22] Filed Oct. 1,1969 3,269,875 8/1966 White 136/212 [45] Patented Nov. 2,197] 3,303,058 2/1967 Sonnenschein.. 136/230 [73] Assignee Siemens Aktiengesellschatt 3,411,955 1 1/1968 Weiss 136/205 Berlin Germany Primary Examiner-Winston A Douglas Pnomy tt i Assistant Examiner-M. J. Andrews S 104187 AtLomeys-itgt M.lAlveTry,kArthur E. Wilford, Herbert L.

Continuation of application Ser. No. an ame 16 640,544, May 23, 1967, now abandoned.

[54] THERMOGENERATOR HAVING HEAT ABSTRACT: A thermogerierator wherein a plurality of ther- EXCHANGE ELONGATED FLEXIBLE METALLIC inocouples are arranged with their high-temperature unctions TUBE 0F WAVY CORRUGATED CONSTRUCTION situated 111 0113 row and with their opposed low-temperature 8 Claims, 6 Drawing 18$ JUUCIIOHS situated in a second row. A pair of elongated heat exchangers respectively extend along these rows and engage [52] U.S.Cl 136/211, the thermocouples at the junctions thereog At has one f 135/210, 136/221, l65/83 these heat-exchangers is in the form of an elongated hollow tu- [5 Ill!- bular structure for conveying along its interior a heal- Fun/00,1401" 1/30 exchanging medium, and this one heat-exchanging structure [50] Field of Search 136/204, has a plummy f rigid portions engaging the thermocouples 210, 21 I, 221; 62/3; 165/83 and a plurality of intermediate flexible portions situated respectively between and o erativel connected with the rigid [56] References (med portions. A spring means COPHCIS witlz both of the heat-exchan- UNITED STATES PATENTS gets for urging them toward each other so as to maintain them 2,729,949 1/1956 Lindenblad 62/3 pressing against the thermocouples.

THERMOGENERATOII HAVING I-IEAT EXCHANGE ELONGATED FLEXIBLE METALLIC TUBE OF WAVY CORRUGATED CONSTRUCTION p This application is a streamline continuation of Ser. No. 640,544 filed May 23, I967 now abandoned.

Our invention relates to thermogenerators.

In particular, our invention relates to therrnogenerators which include at least one tubular structure for conveying in its interior a liquid heat-exchanging medium.

In the construction of thennogenerators a plurality of thermocouples are combined together, in general, in such a way that their low-temperature junctions are arranged in one row extending along the low-temperature side of the generator, while their opposed high-temperature junctions are arranged in a second row extending along the high-temperature side of the generator. Each thermocouple operates according to the well-known Seebeck effect according to which the pair of conductors of the thennocouple, which are made of different metals and which are respectively P-conducting and N-conducting, have their opposed junctions respectively provided with different temperatures so as to generate an electromotive force in the thermocouple. Thus, the conductors of the thermocouple are each made of a material which is operative both electrically and thermally. By way of suitable junction bridges made of electrically and thermally conductive material, the conductors of the thermocouples are electrically interconnected at their low-temperature junctions and high-temperature junctions in such a way that all of the thermocouples are electrically connected in series and are thennally connected in parallel. A pair of heat-exchangers are respectively located in operative engagement with the thermocouples at their hightemperature junctions and at their low-temperature junctions, and the connection between the heat-exchangers and the thermocouples is provided through a layer of thermally conductive but electrically nonconductive material, this layer being situated between and separating the heat exchangers from the thermocouples. In the event that a liquid heat-exchanging medium is to be brought into operative relationship with respect to the junctions of the thermocouples, it is essential that at least one of the heat-exchangers have a hollow tubular construction so as to be able to convey along its interior the liquid heat-exchanging medium.

In general, the temperature differential between the lowtemperature and high-temperature sides of the generator will be on the order of a few hundred degrees centigrade. As a result, the different coefficients of thermal expansion of the materials of the thermogenerator result in great thermal stresses. These thermal stresses, which above all subject the connections between the components of the structure to the strongest load and which are at a maximum in a direction extending longitudinally of the conductors of the thermocouples, since it is in this latter direction that the temperature gradient is at a maximum, must be compensated. It is known to compensate for these thermal expansion forces by the use of pressure contacts which are under compression.

As a result of the operation of these latter contacts, there is the additional result that the resistance to transferred heat at the junctions, during operation, does not change appreciably due to thermal expansion. In this way the efficiency of operation of the thermogenerator is reliably maintained practically constant, this efficiency depending, among other factors, on the magnitude of the resistance to transfer of heat.

In addition, the pressure contacts can compensate for manufacturing tolerances which are encountered in the lengths of the thermocouple conductors and which cannot be avoided during manufacture of the thermocouples, these manufacturing tolerances resulting in a nonuniform contact between the individual thermocouples and the heat-exchangers.

The problems referred to above are solved with structures of the above type in the event that a gaseous heat-exchanging medium is used. In this event, it is always possible to construct the heat-exchangers from individual parts in such a way that the pressure contacts can respectively coact with the individual thermocouples while remaining uniformly in good contact with the heat-exchangers. Where a liquid heatexchanging medium is used, however, at least one of the heatexchangers must be in the form of a hollow tubular structure so as to be capable of conveying along its interior the liquid heat-exchanging medium. As a result such a heat-exchanger does not lend itself to division into a plurality of separate components which are capable of separately coacting with the several thermocouples, and the known, conventional structures cannot reliably compensate for the thermal stresses and longitudinal tolerances of the conductors of the thermocouples.

Therefore, in the case where a thermogenerator is to be constructed in such a way that one of the heat-exchangers thereof will have a hollow tubular structure for conveying in its interior a liquid heat-exchanging medium, care must be taken to see to it that a good heat-conductive contact is reliably maintained between the tubular structure for conveying the liquid heat-exchanging medium and all of the thermocouples even during operation of the generator. Furthermore, care must be taken to see to it that the thermal stresses, which are encountered above all because of the expansion of the conductors of the thermocouples longitudinally, are properly compensated. Finally, it is necessary to compensate for the manufacturing tolerances encountered the lengths of the conductors of the thermocouples.

It is accordingly a primary object of our invention to provide a thermogenerator which will solve the above problems in the case where at least one of the heatexchangers conveys a liquid heat-exchanging medium.

More particularly, it is an object of our invention to provide a thermogenerator having at least one heatexchanger in the form of an elongated hollow tubular structure for conveying in its interior a liquid heat-exchanging medium, while at the same time maintaining proper contact between the latter heatexchanger and the thermocouples, compensating not only for the thermal stresses encountered but also for the'unavoidable manufacturing tolerances.

In accordance with our invention, the above problems are solved by using for the heat-exchanger which conveys the liquid heat-exchanging medium an elongated hollow tubular structure in the form of a metal pipe which is at least partly flexible, while using a spring means to urge rigid portions of the metal pipe against the junctions of the thermocouples so that the contact bridges at the other junctions of the thermocouples, which are distant from the tubular heat exchanger, are pressed against the second heat-exchanger. exchanger.

The partly flexible metal pipe can be manufactured in the form of a metal bellows or in the form of an elongated pipe of wavy configuration, and the rigid portions of the pipe can be provided by way of rigid metal plates which are soldered to the pipe while being distributed parallel to the axis thereof, these plates having flat polished surfaces directed toward the thermocouples. The end surfaces of the metal plates which are directed toward the wavy pipe structure are ribbed and have a configuration matching that of the exterior surface of the metal pipe.

However, it is also possible to construct the tubular heatexchanger medium from a partly flexible metal pipe which is composed of a plurality of relatively large, rigid pipe sections and a plurality of wavy intermediate pipe sections, taking the form of metal bellows, for example, situated between and communicating with the rigid pipe sections.

Thus, with the partly flexible metal pipe of our invention, serving to convey the liquid heat-exchanging medium, there are rigid portions of the pipe which coact with the thermocouples, and a compression spring structure is provided for pressing the rigid pipe portions toward the thermocouples. In this way it is possible to maintain a good heat-conductive contact during expansion of the thermocouple conductors lon gitudinally. Moreover, the thermocouples remain mechanically stable and are held fixed at predetermined locations,

even during changes in the operating conditions. The flexible metal pipe provides in addition a compensation for the manufacturing tolerances in the lengths of the conductors of the thermocouple, these tolerances being unavoidable during manufacture of the thermocouples, since the rigid portions of the flexible pipe remain reliably in operative engagement with the thermocouple junctions even if the latter are not located precisely along a common straight line as a result of the different lengths of the conductors of the thermocouples resulting from the thermal expansion.

In order to prevent the partly flexible metal pipe from bulgin g outwardly to one side, it is situated, according to a further feature of our invention, at least partly within a rail of U- shaped cross section, and this rail has a pair of opposed sidewalls which are respectively fixed to the second heatexehanger and which serve as a support against which the compression springs press.

It is furthermore of advantage, in accordance with out invention, to make the second heat-exchanger in the form of a large pipe and to arrange the rails of U-shaped cross section so that they extend parallel to this latter pipe. This latter pipe will in general form the high-temperature side of the thermogenerator.

By utilizing the above-mentioned rails of U-shaped cross section, it is possible to achieve the advantage of making it easy to remove and replace damaged thermocouples. Thus, with such an arrangement it is only necessary to disconnect one row of thermocouples and to replace the latter.

Our invention is illustrated by way of example in the accompanying drawings which form part of this application and in which:

FIG. 1A is a fragmentary longitudinal sectional elevation of one possible embodiment of a structure according to our invention;

FIG. 1B is a longitudinal sectional elevation of another possible embodiment of a structure according to our inventlon;

FIG. 2 is a fragmentary transverse section of the structure of FIG. IA, taken along line Il-ll of FIG. 1A in the direction of the arrows;

FIG. 3 is a fragmentary transverse sectional elevation of the structure of FIG. lB, taken along line Ill-III of FIG. 1B in the direction of the arrows;

FIG. 4 is a fragmentary longitudinal section of another embodiment of a structure according to our invention; and

FIG. 5 is a partly sectional and partly schematic transverse elevation of the embodiment of our invention which is illustrated in FIG. 4.

Referring to FIGS. 1A and 1B, thermogenerators according to our invention are respectively fragmentarily illustrated therein in longitudinal sections. The thermocouples 1 each include a pair of elongated thermoelectric conductors which are respectively P-conducting and N-conducting. At their hightemperature junctions the several thermocouples are respectively provided with contact bridges 4. At their low-temperature junctions, the thermocouples are respectively provided with contact bridges 2. The contact bridges 2 of adjoining thermocouples are electrically connected to each other by way of twisted, flexible silver conductors 9 which respectively extend between the several thermocouples, each conductor 9 being connected at one end to the contact 2 engaging an N- conducting conductor of one thermocouple and at its opposite end to the contact 2 engaging a small P-conducting conductor of the next thermocouple. By interconnecting the several thermocouples with the flexible, silver, twisted conductors 9, a reliable compensation for lateral expansion of the thermocouples is achieved.

At its high-temperature side, the thermogenerator is provided with a heat-exchanger 7 in the form of an elongated large pipe. The large pipe 7 has a relatively thick wall formed with depressions in which thermally conductive cups 8 are seated, these cups being made of an electrical insulating material so that they are not electrically conductive. The cups 8 may be made of a ceramic material, such as for example, aluminum oxide. The contact bridges 4 of the several thermocouples are respectively fixedly held within the several cups 8, so that the locations of the contact bridges 4 are determined in this way.

At the low-temperature side of the thermogenerator the heat-exchanger takes the form of the flexible metal pipe 6. This pipe is manufactured in the form of a metal bellows. Rigid metal plates 5 are soldered to the metal bellows, and the surfaces of the plates 5 which are directed toward the thermocouples are flat and polished. These metal plates 5 are provided at their end surfaces which are respectively directed toward the pipe 6 with the ribs 15 having an exterior-surface configuration conforming to and matching precisely with that of the metal bellows 6, so that in this way the entire ribbed end surface areas of the plates 5 are in engagement with the wavy pipe 6 so that the heat-transmitting area between the metal bellows 6 and the metal plates 5 is as large as possible to achieve in this way the best possible thermally conductive contact between the plates 5 and the flexible wavy pipe 6. Of course, these plates 5 serve to render the flexible pipe 6 rigid at those portions which are engaged by the plates 5. Between the metal plates 5 and the contact elements 2 of the thermocouples are a plurality of layers 3 made of a material which is thermally conductive but electrically nonconductive, such as aluminum oxide or mica. The metal plates 5 are soldered to the pipe 6 so as to provide the latter with its rigid portions.

A spring means is provided for urging the heat-exchanger 7 and the heat-

exchanger

5, 6 toward each other, and this spring means includes compression springs taking the form of leaf springs 11 in FIG. 1A and coil springs 14 in FIG. 1B. These compression springs, together with the remainder of the spring means described below, serve to press the rigid portions of the flexible heat-exchanging

means

5, 6 against the thermocou ples, and in the case of FIG. 1A the number of leaf springs ll equals the number of thermocouples and are respectively situated in alignment therewith for pressing the several plates 5 toward these thermocouples respectively, while in the case of FIG. 1B the number of springs 14 also corresponds to the number of thermocouples and serves to press the several plates 5 toward the several thermocouples, respectively. In this way there is achieved with the structure of our invention a heat-transmitting contact which does not change even during operation as a result of thermal expansion. Moreover, because of the presence of the flexible portions of the pipe 6, longitudinal tolerances of the conductors of the thermocouples l are compensated.

The spring means of FIG. IA includes, in addition to the leaf springs 11, an elongated rail 10a of U-shaped cross section, and this rail receives the heat-

exchanger

5, 6 in its interior, as is apparent particularly from FIG. 2. The rail l0a has its transverse wall, which extends between its sidewalls, situated at the ends of the sidewalls which are nearest to the heatexchanger 7, so that the transverse end wall of the rail 10a closes off the interior of the rail from the heat-exchanger 7. This transverse end wall of the rail 10a is formed with openings 16 through which the metal plates 5 respectively extend. The leaf springs ll act as the compression springs in this embodiment.

In contrast, as is shown in FIG. 1B and FIG. 3, the rail 10!) of this embodiment, while it also has a pair of opposed sidewalls and transverse end wall, is positioned so that the latter transverse end wall is situated at the edges of the sidewalls which are most distant from the heat-exchanger 7, so that open side of the rail 10!) is directed toward the heat-exchanger 7. The compression springs of this embodiment take the form of the spiral, coil springs 14, and these springs are situated between compression-transmitting elements 12 and the rail 10b. The compression-transmitting elements 12 directly engage and are soldered to the metal bellows 6, and the springs 14 press at their ends which are directed away from the metal bellows 6 against the transverse wall of the rail 10b. Instead of coil springs 14, it is also possible to use cup springs. Guide pins [3 respectively extend through the coil springs 14, are respectively fixed to the metal plates 12, and respectively extend through openings formed in the transverse wall of the rail b.

FIG. 2 shows the configuration of each leaf spring 11. Each spring 11 is provided with opposed, stepped ends which respectively extend through openings formed in the side walls of the rail 10a. FIG. 2 also illustrates the details of the structure of the spring means which connects the rail 10a to the heat-exchanger 7. This structure of the spring means includes at least a pair of bolts 17 fixed to the tubular heatexchanger 7 and operatively connected with angle irons 20 which are fixed to and respectively project laterally from the opposed exterior side surfaces of the rail 10a. The bolts 17 also extend respectively through openings of the angle irons 20, and each bolt 17 is surrounded by sleeves l8 and 19 ,made of thermally insulating material, so that through the sleeves l8 and 19 a thermal insulation between the pair of heat-exchanging means is achieved. The flow of heat in the bolts 17 themselves is negligible. It is of advantage, however, to provide bolts 17 which are themselves made of a thermally nonconductive material.

As may be seen from FIG. 3, this embodiment uses the same structure as that of FIG. 2 for connecting the rail 10b to the heat-exchanger 7. FIG. 3 also illustrates how the springs 14 act to urge the rail 10b away from the pipe 6 so as to urge the latter and the heatexchanger 7 toward each other.

In the embodiment of our invention which is illustrated in FIG. 4, the heat-exchanger pipe which is at least partly flexible has a construction different from that described above. In this embodiment the partly flexible metal pipe includes massive, rigid elongated pipe sections 21 which are interconnected with each other by intermediate wavy pipe sections 22 in the form of metal bellows. The metal bellows sections 22 are welded to the rigid pipe sections 21. By way of the hose-connector fitting 23 the liquid heat-exchanging medium is delivered to the interior of the flexible tubular metallic heatexchanger. It is of advantage to manufacture the rigid pipe sections 21 from elongated metal bars of noncircular cross section which are axially bored so as to provide the tubular structure for the rigid sections 21. For example, these rigid pipe sections may be formed from bars of square cross section which are axially bored to provide the structure shown in FIG. 4. In this way the exterior flat surface for engaging the layers 3 is achieved without any additional manufacturing steps required for this purpose, so that with this construction after the axial bores are formed in the pipe sections 21 they already have the flat surfaces which are directed toward the thermocouples I. It is furthermore to be noted that with this construction it is possible to eliminate the pressuredransmitting plates l2. The springs 14 are capable of directly engaging the flat upper surfaces of the pipe sections 21.

As may be seen from FIG. 4, each rigid pipe section 21 coacts with a pair of thermocouples 1. Thus, each rigid pipe section 21 serves to press a pair of thermocouples toward the heat-exchanger 7. As a result only one coil spring 14 is required for each pair of thermocouples with this embodiment. The heat transmitting contact which is achieved with this construction is also very good, since the longitudinal tolerances or thermal expansion longitudinally of the conductors of the thermocouples are compensated by the seesaw form of the rigid sections 21 each pressing against a pair of thermocouples.

Finally, FIG. 5 shows the construction of FIG. 4 in a transverse view. The square cross sectional configuration of the ipe sections 21 at the exterior thereof is clearly apparent from FIG. 5. The rails 10b of this embodiment are the same as those used in the embodiment of FIG. 1B. The several rails 10b extend parallel to the heat-exchanger 7. Moreover, FIG. 5 shows how with the embodiment of FIG. 4 as well as the remaining embodiments described above a plurality of rows of heat-exchangers are situated axially of the heat-exchanger 7 and circumferentially distributed about the latter in the radial lanes which are indicated by the dot-dash lines in FIG. 5. henever it becomes necessary to change a defective thermocouple, it is only necessary to remove one of the rails so as to have access to the particular thermocouple which requires replacement in order to replace the latter.

We claim:

1. In a thermogenerator, a plurality of thermocouples respectively having high-temperature junctions arranged in one row and opposed low-temperature junctions arranged in a second row, a pair of elongated heat-exchanging means respectively extending along said rows and engaging said thermocouples at said junctions thereof which are situated in said rows, at least one of said heat-exchanging means comprising an elongated metallic tube for carrying a liquid heat-exchanging medium in its interior, said tube being at least partly formed with flexible wavy corrugated portions, a plurality of rigid metal plates fixed to spaced portions of said tube and forming part of said one heat-exchanging means for holding rigid the portions of said tube engaging said plates, said rigid plates respectively having flat surfaces directed toward and engaging said thermocouples and end faces directed away from said thermocouples, said end faces matching the surface of said portions of said tube and engaging said portions over the entire surface area of said end faces, and spring means coacting with said pair of heat-exchanging means for urging them toward each other.

2. The combination of claim 1 and wherein said rigidly held portions of said tube are of the same construction and configuration as said corrugated portions thereof and said rigid plates being fixed to said spaced portions of wavy tubular construction so as to render the latter portions rigid.

3. The combination of claim 2 and wherein said rigid plates respectively have, directed away from said thermocouples, ribbed end surfaces matching the exterior configuration of the wavy tubular construction of said one heat-exchanging means and engaging the latter over the entire surface areaof said ribbed end faces.

4. The combination of claim I and wherein said tube of said one heat-exchanging means comprises elongated rigid tubular portions which engage said thermocouples and intermediate flexible wavy tubular portions extending between and communicating with said rigidtubular portions.

5. The combination of claim I and wherein said spring means includes an elongated rail of U-shaped cross section extending along and receiving in its interior at least part of said one heatexchanging means, said rail having a pair of outer sidewalls respectively fixed to said other heat-exchanging means, and said spring means including a plurality of compression springs each situated between said one heat-exchanging means and said rail for urging the latter away from said other heabexchanging means so as to urge both of said heatexchanging means toward each other.

6. The combination of claim 5 and wherein said other heatexchanging means is in the form of an elongated pipe, and said rail extending parallel to said pipe.

7. The combination of claim 5 and wherein said rail has a transverse wall extending between said sidewalls thereof and engaged by said compression springs, the latter being in the form of coil springs.

8. The combination of claim 5 and wherein said rail has a transverse wall extending between and connected to said sidewalls thereof and situated between said pair of heatexchanging means, said transverse wall of said rail being formed with openings through which portions of said one heat-exchanging means extend into engagement with said thermocouples, and said compression springs being in the form of leaf springs each extending between said sidewalls of said rail and coacting with said sidewalls for urging the latter away from the other of said heat-exchanging means so as to urge both of said heat-exchanging means toward each other.

I I l i

Claims

2. The combination of claim 1 and wherein said rigidly held portions of said tube are of the same construction and configuration as said corrugated portions thereof and said rigid plates being fixed to said spaced portions of wavy tubular construction so as to render the latter portions rigid.
3. The combination of claim 2 and wherein said rigid plates respectively have, directed away from said thermocouples, ribbed end surfaces matching the exterior configuration of the wavy tubular construction of said one heat-exchanging means and engaging the latter over the entire surface area of said ribbed end faces.
4. The combination of claim 1 and wherein said tube of said one heat-exchanging means comprises elongated rigid tubular portions which engage said thermocouples and intermediate flexible wavy tubular portions extending between and communicating with said rigid tubular portions.
5. The combination of claim 1 and wherein said spring means includes an elongated rail of U-shaped cross section extending along and receiving in its interior at least part of said one heat-exchanging means, said rail having a pair of outer sidewalls respectively fixed to said other heat-exchanging means, and said spring means including a plurality of compression springs each situated between said one heat-exchanging means and said rail for urging the latter away from said other heat-exchanging means so as to urge both of said heat-exchanging means toward each other.
6. The combination of claim 5 and wherein said other heat-exchanging means is in the form of an elongated pipe, and said rail extending parallel to said pipe.
7. The combination of claim 5 and wherein said rail has a transverse wall extending between said sidewalls thereof and engaged by said compression springs, the latter being in the form of coil springs.
8. The combination of claim 5 and wherein said rail has a transverse wall extending between and connected to said sidewalls thereof and situated between said pair of heat-exchanging means, said transverse wall of said rail being formed with openings through which portions of said one heat-exchanging means extend into engagement with said thermocouples, and said compression springs being in the form of leaf springs each extending between said sidewalls of said rail and coacting with said sidewalls for urging the latter away from the other of said heat-exchanging means so as to urge both of said heat-exchanging means toward each other.