US2390578A - Thermoelectric generator - Google Patents

Description

Dec., l, 1945. H, J, FlNDLEY 2,390,578

THERMOELECTRIC GENERATOR Filed April l, 1945 3 Sheets-Sheet 1 I N V EN TOR.

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Patented Dee. l1, 1945 THEBMOELECTRIC GENERATOR Howard J. Findlay, Shaker Heights,

signor to Eaton Cleveland, Ohio,

Ohio, as-

Manni'aeturing Company, Y Y Y i. a corporation of Ohio Application April 1, i943, serial No. 481,450

(ci. 13e-4) 7 Claims. This invention relates to thermoelectric generators and more particularly to an improved construction for devices of this kind.

An object of the invention is to provide animproved construction for a thermoelectric generator in which a compact arrangement of, thermocouples is obtained and in which a substantial temperature differential can be maintained between the hot and cold junctions.

Another object of the invention is to provide a thermoelectric generator embodying a heating chamber of novel construction.

Still another object of my invention is to provide an improved construction for a thermoelectric generator wherein a series of refractory electrically-insulating rings support the thermocouples and also form a heating chamber and wherein the rings and thermocouples comprise an assembly unit.

A further object of my invention is to provide an improved thermoelectric generator, oi' the character referred to, which embodies mechanical means i'or causing a flow of cooling medium over certain of the junctions of the thermocouples.

Yet another object oi' this invention is to provide a novel form of thermocouple.

The invention may be further briey summarized as consisting in certain novel combinations and arrangements of parts hereinafter described and particularly set out in the appended claims.

Copending application Serial No. 445,994, filed June 5, 1942, now Patent No. 2,362,258, granted November 7, 1944, discloses a space heater embodying a thermoelectric generator of the type herein disclosed and claimed.

In the accompanying sheets of drawings showing one embodiment of my thermoelectric generator,

Fig. l is an elevational view, with portions broken away, showing a thermoelectrlc generator embodying my invention;

Fig. 2 is a transverse sectional view taken through the device on line 2-2 of Fig. 1;

Fig. 3 is a partial elevational view of the thermopile showing the electrical connections for the groups of the thermocouples;

Fig. 4 is a partial longitudinal sectional view on an enlarged scale, taken as indicated by line 4 4 of Fig. 2;

Fig. 5 is a perspective view showing one of the insulating refractory rings of the thermopile in detached relation;

Fig. 6 is a transverse sectional view taken through one of the refractory rings as indicated by line 6 6 of Fig. 5; i

Figs. 7 and 8 .are partial transverse sectional views showing details of construction and taken respectively on lines 'I--l and 8 8 of Fig. 1;

Fig. 9 is a partial perspective view showing another form of refractory ring;

Fig. 10 is a transverse sectional view thereof taken on line I0-I0 of Fig. 9;

Figs. 11 and 12 are diagrammatic side and end views, respectively, of the thermopile showing a series-parallel hookup for the thermocouples; and

Figs. 13 and 14 are similar diagrammatic side and end views of the thermopile showing another series-parallel hookup for the thermocouples.

'I'he embodiment of my thermoelectric generator shown in the accompanying drawings comprises in general a thermopile I0, a fuel burning means- II for supplying heating medium to one portion of the thermopile and a mechanical means I2 for supplying cooling medium to another portion of the thermopile.

As shown in the drawings, the thermopile I0 comprises an elongated assembly unit made up of a plurality of thermocouple groups or rings I3 and a plurality of electrically-insulating refractory rings I4. The thermocouple groups I3 are in axially spaced substantially parallel relation and each group comprises an annular series of substantially radially extending circumferentially spaced thermocouples I5. The rings I4 are arranged in an elongated series in contiguous substantially coaxial relation and form a substantially cylindrical gas-tight wall IS dening or enclosing an elongated heating or combustion chamber I1.

My thermoelectric generator is preferably, though not necessarily, provided with an outer housing I8 in which the thermopile I Il is disposed. As shown in this instance the housing I8 may be an elongated structure of cylindrical or other de sired shape and formed of sheet metal or other suitable material. The thermopile I0 is arranged in the housing so that the wall I6 formed by the refractory rings I4 extends coaxially with the wall of the housing but is spaced therefrom to provide therebetween an annular cooling chamber I9. The thermopile III is provided at one end thereof with a spider member 2I and at its other end with a hollow fluid-conducting member or exhaust ttlng 22.

The spider member 2| may comprise a sheet metal ring having a peripheral flange 23 engaging the wall of the housing I8, and a shouldered annular recess 24'into which one end oi' the wall I6 extends. Between the peripheral iiange 23 and the shouldered recess 24, the spider may have a plurality of openings forming a portion of the cooling chamber I9. The spider is provided centrally thereof with an opening through which the fuel burning means II communicates with the heating chamber I1.

'I'he exhaust fitting 22 may bein the form of a metal body having heat-radiating fins 21 externally thereof and also having a fluid-conducting passage 28 extending therethrough. The fitting 22 may have a shouldered annular recess 29 surrounding the passage 26and into which the opposite or outer end oi' the wall I6 extends. The exhaust iltting 22 is mounted in the housing I8 by means of lugs 30 formed on certain of the fins 21 and screws 3l extending through the wall of the housing into threaded openings provided in such lugs. The spider member 2| is connected with the exhaust fitting 22 by a plurality of elongated screws or rods 32 whose threaded outer ends extend through ears 33 which are formed integral with certain of the fins of the exhaust fitting. From the construction of the thermopile I0, as just described, it will be seen that the inner end of this unit is supported by the spider 2| and its outer end is supported fby the exhaust iitting 22 and that the refractory rings I4 are held in clamped relation by the rods 32. The thermopile may be supported at an intermediate point by a second spider 34.

As shown in Fig. 2 the thermocouples I5 each comprise a pair of elements 36 and 31 formed of dissimilar metals such as iron and constantan or any other suitable combination of metals. elements 36 and 31 may be ribbon-like pieces of metal whose inner'ends extend into overlapping relation and are welded or otherwise connected together to form thermocouple junctions 38 which are referred to as hot" junctions. The outer ends of the elements 36 and 31 also extend into overlapping relation and are welded or otherwise connected to form cold thermocouple junctions 39. It will be seen from Fig. 2 that the junctions 38 and 39 are arranged alternately or in staggered relation so as to result in all of the thermocouple elements 36 and 31 of one of the groups I3 being connected in series relation with each other. In each of the groups I3 one end of the series of thermocouples is connected with a lead or terminal 4D and the other end oi the y series is connected with an adjacent lead or terminal 4I. The adjacent groups I3 are connected in series with each other by means of short connectors 42 arranged in staggered relation as shown in Fig. 3. Suitable lead wires 43 and 44 may be connected with the end groups I3a and I3-b of the thermopile I0.

As shown in Figs. l and 2 the thermocouples I5 extend substantially radially of the device and have their hot junctions disposed in the heating chamber I1 and their cold junctions 39 disposed in the cooling chamber or air passage I9. The elements 36 and 31 of the thermocouples extend through the wall I6 formed by the refractory rings I4. In addition to forming the wall of the heating chamber, the refractory rings I4 also support the thermocouples I5 in spaced relation and electrically insulate the adjacent thermo couples from each other.

The rings I4 may be made of any heat resisting and electrically-insulating material which will have suilicient strength to support and re- The tain the thermocouples I5 in the desired ar rangement. I prefer to use rings formed of tions of the ring remaining between adjacent grooves 46 form axial teeth or projections 41 which extend between each pair of adjacent ele-l ments 36 and 31. The grooves 46 are of a depth approximately equal to one-half of the width of the elements 36 and 31, and when the rings I4 are assembled in contiguous substantially coaxial'relation, the grooves of one ring register with the grooves of the adjacent ring and cooperate therewith to form radial passages extending across the rings and in which the elements 36 and 31 are accommodated. YIt will be noted that when the grooves of adjacent rings are in the above-explained registering or coinplemental relation, the radial slots `formed thereby have a desired depth or length axiallyof the thermopile and that they hold the thermocouples with the ribbon-like material thereof disposed edgewise to the flow of fluid through the combustion chamber I1 and the cooling pass sage I9.

As seen in Figs. 1 and 4, the rings I4 have interfitting engagement with each other which may be obtained by constructing the rings so that each ring has a concave end face 49 and a convex end face 5I) as shown in Fig. 6. When the rings are assembled the convex face of each ring has interfitting engagement with the concave face of the adjacent ring. This intertting engagement facilitates the operation of assembling the rings in coaxial alignment with each other and assists inholding or retaining the rings in such alignment. As shown in Figs. 4 to 6 inclusive, the end faces of the rings also have annular grooves 5I formed therein which cut across the transversely extending grooves and teeth 46 and 41, and when the rings are in assembled relation the grooves 5I of each ring register with the corresponding grooves of the adjacent rings.

Suitable refractory cement 52 is applied to the rings during the building of the thermopile I9 and serves to unite the rings into a substantially solid tube or sleeve and to also form a gastight seal between the rings and around the thermocouple elements 36 and 31. The cement 52 substantially fills the grooves 5I and forms annular keys 53 therein which assist in holding the rings in proper axial alignment.

From the foregoing detailed description, it will be seen that the thermopile I0 can be conveniently constructed as a preassembled unit and then placed in the housing I8. When the thermopile has been assembled into the housing it will also be seen that one end thereof is anchored to the housing, in this instance the outer end, as by means of the screws 3I engaging the lugs 30 of the exhaust tting 22. The spider 25 at the opposite end of the thermopile is slidable in the housing I8 so as to accommodate the expansion and contraction which occurs in the thermopile as the result of the heating and cooling thereof.

For supplying heating medium to the chamber I1 containing the hot junctions 38, I provide the above mentioned fuel burning means II whichis located at the inner end of the thermopile II). This fuel burning means may include a tapered asoacvs burner tube l' which communicates with the heating. chamber I1 by extending snugly into the central openin oi the spider member 2l. The fuel burning means II also includes a suitable burner 53 extending axially of the tube il and from which gas or liquid fuel is projected and burned. 'I'he iiame and'heated combustion gases are projected into the heating chamber I1 in the direction indicated by the arrows 53a into direct contact with the Junctions 33 and after passing through the chamber I1 are discharged through the passage 23 of the exhaust iltting 22. Since the series of refractory rings Il form a substantially gas-tight wall for the chamber I1, it will be seen that the llame and combustion gases are conned so that they must pass through this chamber into the exhaust tting 22.

It is desirable to maintain a substantial tem- Y Y perature diierential between the hot and cold thermocouple Junctions 33 and`39 and this is accomplished by supplying cooling medium to the junctions 33. For this purpose I provide the above mentioned mechanical means I2 for propelling cooling medium through the passage I9 in which the junctions 33 are disposed, the iiow of cooling air taking place in the direction indicated by the arrows 51a. This propelling means may comprise aisuitable propeller fan 51 and an electric motor 53 with which the fan is connected. 'I'he fan is located at a suitable point in the housing I8, in this instance just outwardly oi' the exhaust fitting 22, and operates to draw cool air into the housing through the openings 59 to cause such air to flow over the exhaust fitting 22 and through the passage I9 in contact with the junctions 39 and the radiating portions of the elements 33 and 31 which project outwardly from the wall I8 of the heating chamber I1.

In accomplishing its function of cooling the junctions 39. the air picks up some heat from the exhaust fitting 22 and a relatively greater amount of heat from the radiating elements 38 and 31 of the thermocouples and when such heated air is discharged from the housing it can be used as a space heating medium or can be directed against any object desired to be heated. Likewise, the heated combustion gases which are disengaged through the exhaust tting 22 can be used as a heating medium. Electric current for operating the motor 53 is obtained from the thermopile III although this motor can be operated from some other source of current if desired. Likewise. the electric current generated by the thermopile III can be used for other purposes than driving the fan motor 58. As shownin Fig. i suitable terminals 53 are mounted on the housing I3 in insulated relation thereto and with which the lead wires 43 and 4l are connected. Suitable conductors 59a connect the fan motor 58 with these terminals and the radio or other electrical device being operated in addition to the fan motor is connected with the terminals by the conductors 53h.

For bringing the name and combustion gases in more direct contact with the thermocouples 38, it may be desirable to provide a flame spreader or deilector 60 in the heating chamber I1. The spreader 60 comprises a tubular member extending axially of the heating chamber and may be suitably supported as by having its outer end connected with the exhaust iltting 22. The spreader may have a closed tapered end 6I adjacent the fuel burning means II and its opposite end may extend through the exhaust fitting tion 32 located in iront of the ian 51 so that air from the latter will be directed into the spreader. At one or more points therealong, the spreader may have hooded aspirated openings 83 through which the air supplied by the ian will be discharged or drawn during the operation of the device. The air thus supplied through the spreader may serve as supplemental air for combustion and other purposes. The spreader GII can be omitted ii.' desired.

I have found it desirable to construct the thermocouples I 5 with a metallic coating 65 thereon which considerably increases the heat and electrical conductivity oi' the thermocouples. This metallic coating may be of nickel or chromium or may be a-coating formed by successive layers of these metals. The metallic coating is preferably applied to the thermocouples after the `functions 33 and 39 have been formed and extends over the junctions as a continuous coating which protects the junctions from corrosion and deterioration, particularly the junctions 33 which are subjected to the direct action of the flame and combustion gases. 'I'he metallic coating 65 can be applied to the thermocouples in any suitable way such as by dipping the thermocouples or the thermocouple groups I3 in a heated bath of metal or by subjecting the thermocouples or thermocouple groups to an electroplating action.

In Figs. 9 and 10 I show another form oi' refractory ceramic ring B1 which can be used instead of the rings Il in forming the wall I3. The end faces of the ring 61 are transversely grooved similarly to the ends of the ring I4. On one end of the ring 61 the intervening teeth 63 are shouldered as indicated at 39 and the other end face has an annular groove or recess 10 therein. The teeth 1I lying outside of the groove 10 are som/ewhat higher than the teeth 'I2 which lie inwardly of the groove 10. When a plurality of the rings 81 are arranged coaxially in a group or stack the tons of the teeth 68 extend into the recessed end of the adjacent ring with the annular shoulder B9 engaging just insidethe teeth 1I. Suitable refractory cement is also used between the rings 61 in the same manner and for the same purpose as will the rings Il.

During the operation of my thermoelectric generator a continuous stream of burning fuel and combustion eases is directed by the burner 56 through the chamber I1 into the exhaust iltting 22. The ame and combustion gases heat the junctions 38 while the iunctions 39 are being cooled by the air delivered by the fan 51. Electric current is generated in the junctions 38 and 39 and since the `thermocouples are connected in series the voltages add up and an electromotiv force of substantial value is made available at the leads I3 and M.

Instead of connecting all oi' the thermocouples in series I can use a series-parallel relation for the thermocouples which is more satisfactory in certain cases, particularly where diierent sections of the thermopile are heated to different temperatures. In the diagrammatic views of Figs. 11 and 12 I show a series-parallel arrangement wherein the thermocouple rings 1S of the thermooile 16 are each divided into three sectors 11. Each such sector comprises a plurality oi' radially extendiner individual thermocouples 13 connected in series. The sectors of the thermocouole rings are arranged to lie in axially extending rows, as shown in Fig. ll, and the sectors of each row are connected in series by the con- 22 and may have an open funnel-shaped por- Y rows are connected together to give a parallel hook-up for the three rows of sectors.`

In the diagrammatic lviews in Figs. 13 and 14,

I show another series-parallel hookup in which' the thermocouple rings 82 of the thermoplle 83 are in three groups 84, 85 and 86. The individual radially extending thermocouples 81 of each ring are connected in series and the rings of each group are also connected in series by the connectors 88. Each of the groups 84, 85 and 86 has apositive lead 89 at one end and a negative lead 90 at its other end and these leads are connected -to give a parallel hookup for the groups of thermocouple rings.

From the foregoing description and accompanying drawings it will now be readily understood that I have provided a thermoelectric generator of a new and improved construction and which is compact-in design and eillcient in operation.

While I have illustrated and described my improved thermoelectric generator in considerable detail, it will be understood of course that VI do not wish to be limited in this respect but regard my invention as including all changes and/variations coming within the scope of the appended I intertting engagement with each other and rial and being heid by said grooves so that the ribbon-like material is disposed in edgewise relation to the longitudinal axis of saidheating chamber.

4. In a thermoelectric generator, a heating chamber comprising a series of vsubstantially coaxially disposed contiguous refractory lrings in having grooves extending generally `radially thereacross, a housing extending longitudinally around said heating chamber and spaced from the wall thereof to form a passage for cooling fluid, and a plurality of thermocouples disposed in said grooves and extending therefrom into the ing into the heating chamber` through said grooves, said thermocouples being made of ribbon-like material and being held by said grooves so that the ribbon-like material is disposed in edgewise relation to the longitudinal axis of said heating chamber.

2. In a, thermoelectric generator, a heating chamber comprising a series of substantially coaxially disposed contiguous refractory rings having grooves extending generally radially thereacross, a `plurality of thermocouples extending into the heating chamber through said grooves, and refractory cement forming a substantially gas-tight seal between .said rings and around said thermocouples.

3. In a thermoelectric generator, a heating chamber comprising a series of substantially coaxially disposed contiguous refractory rings having radiating grooves extending thereacross, and a plurality of thermocouples extending into the heating chamber through said grooves,v said thermocouples being in substantially parallel axially spaced groups and each group comprising a series of substantially radially extending thermocouples held in circumferentially spaced relation by their engagement in said grooves, said thermocouples being made of ribbon-like mateheating chamber and said cooling passage, said thermocouples being made of ribbon-like material and being held by said grooves so that the ribbon-like material is disposed in edgewise relation tothe longitudinal axis of said heating chamber and cooling passage.

5. In a thermoelectric generator, a heating chamber comprising a series of substantially coaxially disposed contiguous refractory rings having grooves extending thereacross, said rings being disposed so that the grooves of one ring register substantially with the grooves of the adjacent ring to form passages, and a plurality of thermocouples extending into the heating chamber through said passages.

6. In a thermoelectric generator, a tubular heating chamber compriisng a series of contiguous refractory rings having intertting engagement with each other, said rings having substantially radial grooves lextending thereacross and the rings being disposed so that the grooves of one ring register substantially with the grooves of the adjacent ring to form passages, and a plurality of thermocouples supported by said heating chamber and extending thereintothrough said passages. i

. '7. In a thermoelectric generator, a pair of spaced outer and inner substantially coaxial tubular members defining a heating chamber and a cooling chamber, the inner member having a wall formed by a series of refractory ceramic rings held in substantially coaxial relation and having radiating grooves extending thereacross, a plurality of thermocouples extending through said wall and having junctions disposed in said heating and cooling chambers, said thermocouples being in substantially parallel axially spaced groups and each group comprising a series of substantially radially extending cir-` cumferntially spaced thermocouples lying in said radiating grooves, means for causing a flow of combustion gases through said heating chamber in direct contact with the thermocouple junctions therein, and mechanical means operable to propel cooling air through said cooling chamber in direct contact with the thermocouple junctions therein.

HOWARD J. FINDLEY.

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