US3881962A

US3881962A - Thermoelectric generator including catalytic burner and cylindrical jacket containing heat exchange fluid

Info

Publication number: US3881962A
Application number: US330017A
Authority: US
Inventors: Martin A Rubinstein
Original assignee: General Atomics Corp
Current assignee: General Atomics Corp
Priority date: 1971-07-29
Filing date: 1973-02-06
Publication date: 1975-05-06
Anticipated expiration: 1992-05-06

Abstract

A generator of the thermoelectric type isolates the fuel combustion area thereof from a series of thermoelectric elements or modules and makes use of a two-phase vapor heat transfer in which there is a transfer from a liquid phase to a gaseous phase through the intervening presence of a boiler in which a fuel burner is supported. Fuel consumed in the boiler creates heat impinging upon a jacket of the boiler in which a vaporizable fluid is confined. The heated vapor thus produced flows through a series of heat exchange loops radiating from the boiler, to heat the hot junctions of the thermoelectric elements. The electrical energy is produced by a potential developed between the hot and cold junctions of said elements.

Description

I United States Patent 11 1 [111 3,881,962

Rubinstein 1 May 6, 1975 [S4] THERMOELECTRIC GENERATOR 3,627,588 12/1971 Rubinstein et a1 136/208 X INCLUDING CATALYTIC BURNER AND 3,663,566 5/1972 Paipe 136/208 X CYLINDRICAL JACKET CONTAINING ,71 ,532 3/1973 Fa enberg et a1, 136/208 HEAT EXCHANGE FLUID FOREIGN PATENTS OR APPLICATIONS Inventor: Martin A. Rubinstein La Jolla 1,932,087 l/l 971 Germany .1 136/208 C l'f. al Primary Examiner-Benjamin R. Padgett [73] Asslgneez General Atomic Company, San A i t ExaminerE. A. Miller g Calif- Attorney, Agent, or Firm-Fitch, Even, Tabin & 1 Filed: Feb. 6, 1973 Luedeka 2! Appl. No.: 330,017

Related U.S. Application Data Continuation-in-part of Ser. No. 167,212, July 29, 1971, abandoned.

References Cited UNITED STATES PATENTS 12/1898 Emanuel 136/210 X 12/1965 Hunt 431/268 X 2/1966 Nelson 136/208 8/1966 Dem 136/208 [57] ABSTRACT A generator of the thermoelectric type isolates the fuel combustion area thereof from a series of thermoelectric elements or modules and makes use of a twophase vapor heat transfer in which there is a transfer from a liquid phase to a gaseous phase through the intervening presence of a boiler in which a fuel burner is supported. Fuel consumed in the boiler creates heat impinging upon a jacket of the boiler in which a vaporizable fluid is confined The heated vapor thus produced flows through a series of heat exchange loops radiating from the boiler, to heat the hot junctions of the thermoelectric elements, The electrical energy is produced by a potential developed between the hot and cold junctions of said elements,

8 Claims, 10 Drawing Figures SHEET 2 OF 5 FAYENTEB A W5 ATTORN EYS PATENTEDHAY 5191s SHEEI 3 BF 5 I I 1 1 1 I 4 1/ 1 1 11 11 1 11 1 11 11 1 1 1 1 11 1 11 11 91 1 l1 1 11 1 1 1/ 1/ 1 1/ 1 11 1/ 11 1 11 a .7 I

I N VEN TOR.

ATTOR N EYS PATENIEBMM' 61915 '2 snznunr s 2 P'JE NTEU HAY 6 i875 SHEET 5 BF 5 FIG/0 THERMOELECTRIC GENERATOR INCLUDING CATALYTIC BURNER AND CYLINDRICAL JACKET CONTAINING HEAT EXCHANGE FLUID This application is a continuation-in-part of copending application Ser. No. 167,2l2 filed July 29, 197], now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention pertains to electrical generators, and in a more particular sense, to generators having a multifuel capability, together with a design facilitating the individual replacement of thermoelectric modules, boiler structure, and burner means.

2. Description of the Prior Art Thermoelectric generators as heretofore devised have been so designed as to cause the hot products of combustion to impinge directly upon a fire wall located in close proximity to, indeed often in direct contact with, thermoelectric elements. As a result, uniform application of heat to the thermoelectric elements has been difficult to achieve. In many instances, this has resulted in the application of excessive heat to said elements, with resultant damage or destruction thereof. Further, the failure to apply heat uniformly to said elements has adversely affected the performance and reliability of the generator, with respect to the steady and uniform production of electrical energy.

The prior art generators, further, have had the undesirable characteristic in that destruction or damage to one component of the generator has often required replacement of the entire generator, or in any event has required the replacement of other undamaged component portions thereof.

In essence, thermoelectric generators as heretofore conceived have been expensive to make, maintain, and repair, while nonetheless being characterized by lack of full reliability in performance, and by inability to deliver maximum energy on a continuing, uniform basis in relation to the amount of fuel consumed.

I am aware, in this regard, of the following patents relating to thermoelectric generators, which may be considered typical of the prior art in that they have one or more of the characteristics discussed above, and which I seek to eliminate in the present invention:

Findley 2,410,872 Findley 2,415,005 Sparrow 2,454,229 Findley 2,480,405 Findley 2,5 l9,24l Findley 2,520,679 Arvin 2,645,675 Flagg 2,665,321 Biggle 2,692,440 Kile 2,783,290 DeLeon 2,82 l ,564 Anderson et al 2,843,647 Imelmann 2,987,564 McCormack 3,26l ,720 Spira et al 3,266,944 Dent 3,269,873

Generators such as shown in the patents listed above are in some instances such as to be designed for use with only one kind of fuel, whether this be gas, liquid, or solid. In other instances, the patents involve thermal contact of the hot products of combustion either directly with the thermoelectric modules, or alternatively with fire walls that are contiguous or at least in close proximity to said modules. And, in still other patents,

application of the heat is to non-removable modules, requiring replacement of the entire generator in the event of destruction of a thermoelectric element or module by, for example, the application of excessive heat thereto. In yet other instances, the thermoelectric conversion means is only a single means of this type, with excessive fuel consumption in relation to the amount of electrical energy generated.

SUMMARY OF THE INVENTION Summarized briefly, the thermoelectric generator constituting the present invention has, within a suitable housing, a boiler structure for a vaporizable liquid. Vaporized liquid within the boiler flows in thermal contact with a readily replaceable thermoelectric element or module.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top plan view of a six-sided thermoelectric generator according to the present invention, in which a portion of the housing and flue have been broken away;

FIG. 2 is a side elevational view of the generator, portions being broken away;

FIG. 3 is an enlarged vertical section taken longitudinally through the thermoelectric generator constituting the present invention, substantially on line 33 of FIG. 2, in which portions have been shown fragmentarily;

FIG. 4 is a fragmentary, vertical sectional view on the same cutting plane as FIG. 3, showing a modified burner assembly usable with the remainder of the apparatus shown in FIGS. 1-3, and adapted particularly for the utilization of solid fuels as distinguished from the burner structure shown in FIG. 3 wherein gaseous fuels are used;

FIG. 5 is a view similar to FIG. 4, showing another modification in the burner assembly, also usable with the remainder of the apparatus shown in FIGS. 1-3, and in this instance designed particularly for utilizing liquid fuels;

FIG. 6 is a still further enlarged, detail section substantially on line 66 of FIG. 3, illustrating the construction of a condenser or heat block incorporated in the invention;

FIG. 7 is a transverse sectional view through the condenser on the same scale as FIG. 6, taken substantially on line 77 of FIG. 6;

FIG. 8 is a full section side view of a further embodi ment of the invention;

FIG. 9 is a full section side view of one type of burner which may be employed in the invention; and

FIG. 10 is an enlarged sectional view taken along the line l010 of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A housing generally designated 10 includes a rectangular lower housing section 10 of sheet metal having a horizontal top wall 12 fixedly secured to vertical side walls 14, rear end wall 16, and front end wall 18 having an access opening 19 (FIG. 2) bounded by a forwardly projecting mounting flange 19 supporting a removable access plate 20. Afiixed to the respective, opposite sides of the lower housing section 10 are angle-iron base flanges supporting the bottom wall 23 of the lower housing section 11 above the floor or equivalent supporting surface S.

Within the lower housing section ll, a vertically disposed transverse partition 24 divides the interior of said housing section into an electrical accessories compart ment 26 to which access is had through the flanged opening of front wall l8, and a larger boiler-and burn er-receiving compartment 28. An access door 29 similar to door covers an access opening provided in rear end wall 16. Obviously, additional access openings can be provided, to permit replacement, maintenance, or repair of the various components mounted in the compartment 28. This is true, also, of the electrical accessories compartment 26.

It may further be noted that the electrical accessories disposed within the compartment 26 would be those that are normal and incident to thermoelectric generators, and since these are conventional and well known, they have not been illustrated. In a generator of this type. the electricity generated by the thermoelectric elements or modules is conducted through the compartment 26, in which compartment there would normally be such regulatory, voltage control, terminal and gauging components as, for example, a voltage regulator. terminal block, ammeter, and voltmeter, all of these being conventional devices requiring no special illustration.

Housing 10 also includes an upper housing section generally designated 29, in which is mounted a series of thermoelectric modules, wherein the actual conver sion of thermal to electrical energy takes place.

The specific configuration and relative arrangement of the component parts of the housing can, of course, be varied, and the illustrated structure is intended merely as one embodiment of the housing.

BURNER ASSEMBLY Designated generally at 30 in FIG. 3 is a burner assembly. which in this FIGURE of the drawing is of the gaseous fuel type, utilizing fuels such as propane, methane, or the like.

The particular structure of the thermal energy source or burner means 30 may vary, but in the illustrated, presently preferred embodiment l utilize for this purpose a gaseous fuel inlet tube 32 that may extend from a fuel gas tank or cylinder, not shown, supplying gas under regulated pressure, said tube 32 extending to a burner head 33 having an upwardly projecting gas jet 34 disposed within a mixing chamber 36 provided by the enlarged lower portion of an upwardly opening, vertically and centrally disposed venturi 38. The enlarged lower end portion of the venturi 38 is mounted within a retainer sleeve 39. Registering apertures are formed in the sleeve and in the enlarged lower portion of the venturi, defining air ingestion ports 42 through which air is drawn to mix with the gaseous fuel issuing under pressure from jet 34.

To assure a sufficient, continuing air supply, an air inlet duct 44 extends vertically above the upper end of housing 10, and is provided at its upper, inlet end with a protective cup below which the duct is open to the entry of ambient air. The duct extends downwardly into the lower section of the housing where it opens to supply air to the burner.

Also illustrated in FIG. 3 is a thermal probe 46, disposed within a boiler assembly to be described herein after, in close proximity to the heated, inner wall of the boiler structure. The probe, which per se is conventional, is so designed that when the heat in the sensed area exceeds a predetermined value, expansion of liquid within the wet bulb of the probe is communicated through a connecting tube 48 to a thermal control valve 49, which is also conventional. Said valve operates to shut off the flow of gaseous fuel from the fuel supply tube 32 to the jet 34. Mb :1 result, combustion in the boiler-heating area terminates temporarily allowing the liquid confined in the boiler assembly to cool. As soon as the liquid cools to a predetermined lower temperature value, valve 49 opens, allowing the gaseous fuel to be supplied again to the jet 34. Rc-ignition then occurs, in a manner to be described hereinafter.

The probe is enclosed in a well 47, sealed against leakage.

BOILER ASSEMBLY The boiler assembly has been generally designated 50 and is in the form of an exteriorly insulated, upstanding, cylindrical structure that includes a vertical outer tube or cylinder 52 of constant diameter, in concentric, spaced relation to an inner tube or cylinder 54. At their upper and lower ends,

cylinders

52, 54 have buttwelded, leak-tight connection to annular top and

bottom walls

56, 58 respectively.

The material of at least the inner cylinder 54 is selected for high heat exchange characteristics.

Encasing the outer cylinder is heat insulation 60.

The insulated structure defined by the concentric inner and

outer boiler tubes

54, 52 respectively constitutes a boiler jacket generally designated 51, in which is confined a fluid F to be heated by combustion of the gaseous fuel. In this connection, within the jacket is included a cylindrical barrier 62, concentric with and disposed substantially equidistantly from the outer and inner boiler tubes. Barrier 62, at its upper end, terminates well short of the upper ends of the inner and outer boiler tubes, and extending from the upper end of the boiler to the outer boiler tube is annular end plate 64 having a leak-tight connection both to the barrier 62 and the outer tube 52 of the boiler.

At its lower end, the cylindrical barrier 62 is spaced upwardly from the bottom wall 58 of the boiler structure.

The provision of barrier 62 within the boiler space defined between the inner and

outer tubes

52, 54 incorporates in the boiler jacket a cylindrical vertically extending, elongated outer or condensate return chamber 66, and an inner, elongated, vertically disposed, cylindrical vaporizing chamber 68.

Chambers

66, 68 are in free and open communication, at their lower ends, through the full circumference of the boiler jacket. The upper end of the outer chamber is closed well below the upper end of the boiler jacket, but the upper end of the vaporizing chamber 68 extends fully to the upper end of the jacket, as shown at 69 in FIG. 3.

The jacket of the boiler extends about a centrally disposed, vertically extending, combustion chamber 70 defined by a hollow center area of the boiler assembly the wall of which is the inner boiler tube 54. In a man ner to be described hereinafter, combustion occurs within chamber 70, and the hot products of combustion pass upwardly, through a stack 72 defining a flue 73 and mounted as a vertical upper extension of the boiler assembly. Stack 72 is mounted in a center opening of the top wall of the housing 10, and as shown in FIG. 2 may be provided at its upper extremity with a cap 74 peripherally apcrtured to provide an outlet for the flue.

An inlet is defined at the lower end of the boiler by reason of the formation of the inner boiler tube open at both its upper and lower ends.

The boiler assembly, in the illustrated example, is supported in spaced relation to the bottom wall 23 of the housing 10, through the provision of circumferentially spaced supporting legs 76 welded or otherwise fixedly secured at their upper ends to the outer boiler tube 52, and extending downwardly from said outer boiler tube to the bottom wall 23, where said legs may be provided with feet as shown in FIG. 3 to stably support the boiler assembly.

CATALYTIC REACTOR In the form of the invention utilizing a gaseous fuel, illustrated by way of example in FIG. 3, I provide a catalytic reactor generally designated 78, said reactor being alternatively termed a combustion cone. Reactor 78 has the highly desirable functional characteristic of effecting release of usable heat uniformly in close proximity to and over the full area of the boiler surface where heat exchange to the confined fluid F is to desirably occur, with said release of the heat occuring at temperatures much lower than the combustion temperature of the gaseous fuel. Within the catalytic reactor, which is mounted in upstanding position within the combustion chamber as shown in FIG. 3, and which in the illustrated embodiment is preferably of frustoconical form, there is defined a fuel-air mixing chamber 87 open at its lower end to receive the burner means 30. Extending about the mixing chamber is an upwardly tapering cylinder 79 forming the side wall of the reactor, said cylinder including an inner wall member 80 of woven wire material, concentric with and spaced inwardly from an outer wall member of catalytic cloth material. The space between the wall members is filled in the illustrated example, by ceramic pettets 84, or can be any other form of porous ceramic material, as for example a single cylinder or loose aggregate. In any event, said material serves as means to diffuse the gas- /air mixture as it passes from the chamber 87 to the catalytic cloth member 82.

The ceramic substance might well be, for example, a molded, solid form formed with perforations or otherwise made pervious to the flow of the gaseous mixture. Whatever the form of the ceramic material, it serves the further desirable function of preventing spontaneous ignition of the combustible mixture. As a result, on the surface of the catalytic cloth material of which the outer wall member 82 is formed, the catalytic reaction occurs, that is, the fuel/air mixture reacts in the presence of the catalyst to release heat to the inner boiler tube 54 at temperatures that are uniform and as indicated above are much lower than would occur if combustion were to be effected directly against the inner wall of the boiler jacket without the presence of a catalytic reactor. In an optimum arrangement achieved through use of the catalytic reactor, the temperature at the surface of the outer wall member is on the order of I200F. The temperature within the mixing chamber 87, under the circumstances, is approximately 600F.

The catalytic cloth mateial from which the outer wall member 82 is fashioned, in a preferred embodiment, would be a ceramic fiber cloth such as, for example, that sold under the trademark Fiberfax", manufactured by The Carborundum Co., Niagara Falls, NY. This cloth, to provide the catalytic surface, would be platinum covered or coated. In addition, catalytic activity can be enhanced by applying a wash coating of alpha ceramic material prior to platinizing.

In the upper end of the reactor, there is inserted a plug 86 of heat insulation material. Further, to close the space between the inner and

outer wall members

80, 82 respectively, there are provided annular bottom and

upper closures

88, 89 respectively.

The catalytic reactor is a self contained unit capable of being replaced within the center area of the boiler, without difficulty, and without requiring corresponding replacement or modification of the boiler assembly. To this end, the reactor includes at its lower end a flat mounting flange 90, extending outwardly and attached by screws or equivalent fastening means to the lower end of the boiler assembly. To prevent heat loss through the lower end of the boiler jacket, there is included, preferably, a removable ring 91 of heat insulation and easily or otherwise secured in underlying relation to the flange 90.

THERMOELECTRIC CONVERTER STRUCTURE As previously noted herein, the housing 10 includes, in addition to the lower housing section, an upper housing section generally designated 29. Referring in particular to FIGS. 1 and 2, and the upper section 29 has a polygonal side wall 94, of sheet metal or the like, secured to and supported directly upon the lower housing section top wall 12. Mounted removably upon each of the several sides of wall 94 is a cooling fin assembly 96, constituting a heat dissipating means. The several assemblies are identical to each other, and each can be removed for replacement independently of the remaining assemblies, to facilitate manufacture and maintenance at the lowest possible cost.

Each assembly 96 includes a flat, rectangular mounting plate 98, secured in face to face contact with its associated side wall portion 99 of polygonal side wall 94. Each assembly 96 further includes a series of uniformly spaced, radially outwardly extending cooling fins 100 Each fin 100 is of rectangular form, as shown in FIG. 2, and like the associated mounting plate 98 is of a material having good heat dissipation characteristics, as for example aluminum.

In association with each heat dissipation means 96, I provide, within the upper housing section 29, a fluid condenser generally designated 102, comprising the thermoelectric-module-heating component of a heating fluid conduit means or loop generally designated 101. As seen from FIG. 1, the loops 101 correspond in number to the cooling fin assemblies 96, with each loop extending radially from the boiler assembly toward its associated cooling fin assembly.

The construction of each heating fluid conduit means of loop 101 is shown in particular advantage in FIGS. 3, 6, and 7. Referring to FIG. 3, it is seen that each loop 101 is generally C-shaped, with the condenser 102 thereof arranged vertically as the bight portion of the C. In a preferred embodiment, and as shown to particular advantage in FIGS. 6 and 7, each condenser 102 is a casting 104 of low carbon steel or the like, of generally oblong configuration cast in a shallowly cupped or dished form. Integrally cast on the back wall 105 of the cast block 104 are banks or rows of pins 106. In the illustrated embodiment, there are six rows, with five pins to each row. The number and arrangement of the pins can of course be varied. Closing the block so as to make the same leak tight is a cover plate 108, which may be of the same material as the body portion of the block.

Within the condenser the superheated fluid F in heat-exchanging relation to the interior surface of the casting 104, including the surfaces of the pins 106 and the internal surfaces of the side wall 109 and back wall I of the block or casting. Said vaporized fluid flows into the block at the upper end thereof, through a vapor inlet tube or first vapor passage 110, the fluid at this time being in vaporized formv The condensate flows out of the lower end of the block, through the condensate outlet tube or second fluid passage 112.

To accommodate the tubular connections between the condenser I02 and the boiler jacket to expansion and contraction of the components of the conduit through which the fluid passes, there is provided a bel lows type connection 114 between the condenser 102 and the

tubes

110, 112.

By means of connecting fittings 116, the tubes 110, 1 12 are connected in communication with vapor and condensate tubes 118, respectively, which extend outwardly from the boiler jacket wall in communication, respectively, with the vaporizing chamber 68 and condensate return chamber 66.

Designated generally at 122 are thermoelectric devices or modules. interposed between the several condensers 102 and their associated cooling fin assemblies. The modules 122 are mounted against the inner surfaces of the several side wall portions 99 of the upper housing section 29. Said side wall portions 99, it may be noted. are selected to be formed of a material having a high rate of heat exchange, whereby heat may be transmitted from the modules to the cooling fin assemblies with minimum resistance to the passage thereof from the modules to the mounting plates 98 of the cooling fin assemblies.

The specific construction of the thermoelectric devices 122 can vary, since said devices are individually well known in the art, and do not, in and of themselves. constitute part of the present invention. Each thermoelectric device or module, in a thermoelectric genera tor assembly, conventionally includes a first portion 123 that constitutes a heat absorbing means, and a sec end portion 125 (FIG. 3) that constitutes a heat trans fer means. Portion 123 is desirably in good thermal contact with the heat producing structure of the gener ator, and in the illustrated example. portion 123 is thus in face to face contact with, but is electrically insulated from (usually by a mica spacer about 0.002 inch thick), the back wall 105 of the condenser 102, where said portion 123 will be heated to the maximum extent by transfer of heat from the vapor passing through the casting 104 in impinging relation to the large internal surface area of the casting. The portion 125 of each module, on the other hand, is in intimate, face to face contact with but electrically insulated from (usually by a mica spacer) the cooling structure comprised of the side wall of the upper housing section and the cooling fin assemblies 96.

It is conventional, further, that circuit means, not shown, be connected across the hot junction defined by the heated module portion 123, and the cold junction defined by the cooled module portion 123. In this way electrical energy is obtained. This functional characteristic is common to all thermoelectric generators of the general category herein described and illustrated, and

hence requires no special illustration or description herein.

MODIFIED BURNER UTILIZING LIQUID FUEL Referring to FIG. 5, there is here shown a modified construction, in which a liquid fuel burner is mounted within the open center area of the boiler, rather than the gaseous fuel burner shown in FIG. 3. In all other respects, the construction is identical to that already described, and thus it is seen that the construction of the thermoelectric generator constituting the present invention is such as to permit selective mounting of liquid, gaseous, and (as will hereinafter appear) solid fuel burners in association with the boiler, housing, and thermoelectric converter structure illustrated and described previously herein. This is of importance, in that it simplifies manufacture, permitting a single form of boiler, thermoelectric converter, and housing to be used regardless of the type of burner needed to meet the requirements of the particular installation.

In any event, as shown in FIG. 5, not only is it possible to substitute a liquid fuel burner for the gaseous burner shown in FIG. 3, but also, the catalytic reactor 78 remains unchanged, except for removal of the plug 86 and substitution of an auxiliary boiler 124 thereof.

A liquid fuel inlet tube 126 extends upwardly within the hollow interior of the catalytic reactor 78 and its upper, outlet end opens into the lower end ofa cylindrical, upwardly projecting boiler cylinder 127 disposed axially of and within the open center space of the main boiler structure.

The nature of the liquid fuel can vary, and typically, I employ kerosene or alcohol as the liquid fuel 129 fed through tube 126 from a suitable pressure regulator, not shown.

Within the boiler cylinder 127, the liquid fuel 129 is vaporized, in the presence of surrounding heat within the boiler, and flows into the upper, inlet end of a vaporized fuel supply tube 128 passing downwardly from the upper end of the interior of the boiler cylinder 127, to open upon the inlet end of a venturi 130 mounted within the catalytic reactor. At the lower end of the venturi, the vaporized fuel is injected into the venturi in jet form, by reason of the fact that the vaporized fuel issues from the tube 128 into a hollow head 132, out of which it is forced as a jet through a nozzle 134.

Air is ingested for mixture with the vaporized fuel forced out of the nozzle 134, through a circumferential series of air inlet ports 138, formed in a mounting cup or housing 136 secured to the lower end of the main boiler jacket. The ports 138 are communicated with ambient atmosphere through the provision of radial openings 139 formed in the heat insulation that surrounds the boiler jacket.

A removable, insulated access panel 140 is mounted against a large center opening formed in the burner support housing 136, for inspection and maintenance of the liquid fuel burner structure.

The vaporized fuel/air mixture emanating from the venturi I30 passes through the foraminous wall of the catalytic reactor in the same manner as the combustible mixture of the first form of the invention illustrated in FIG. 3. Combustion occurs in the same manner as for gaseous fuel, and the liquid within the main boiler jacket is heated and vaporized, and flows in the same path as in the first form.

In the event re-ignition of the liquid fuel is needed, due to a temporary shut-down of the burner resulting from excessive heat against inner wall 54, or resulting from other circumstances that might arise, re-ignition of the mixture may be provided, in the combustion space 70 above the auxiliary boiler, by means of an igniter in the form of a spark plug or the like, not shown, mounted within the combustion space or chamber 70 and the use of an electric resistance heater in the fuel boiler to provide vapor for the jet. The resistance heater, also not shown, would be in circuit with the igniter. In this event, combustion gas products from the catalytic burner would be ignited, setting into operation the vaporizing of the liquid fuel within the auxiliary boiler cylinder 127. Thereafter, as previously indicated herein, vaporization of the kerosene, alcohol, or other liquid fuel will result by impingement of the combustion gas products from the catalytic burner against the wall of the cylinder 127.

MODIFIED BURNER STRUCTURE UTILIZING SOLID FUELS Referring to FIG. 4, there is shown yet another form of burner structure capable of association with the main boiler, thermoelectric converter means, and housing shown in FIGS. 1, 2, and 3. In this form of the invention, which may be particularly useful in remote, relatively primitive areas, a solid fossil fuel such as lumps of coal C are dropped manually or otherwise stoked into a fuel receiver generally designated 144. This is merely an upwardly opening, metal cylinder, the wall of which is relatively thin to assure high heat transfer therethrough to the wall 54 of the main boiler. To further facilitate the transfer of heat, and also to facilitate combustion of the solid fuel, the fuel receiver 144 is formed with vertically and circumferentially spaced openings 142.

As is true of the gas and liquid fuel burners, the fuel receiver 144 is removably mounted against the lower end of the main boiler jacket, without requiring modification of the essential construction of said jacket. To this end, a support ring 146 is secured by screws 147 to the bottom wall 58 of the boiler jacket, supporting the fuel receiver within the hollow center area or combustion space 70 of the boiler.

Carried by the support ring 146 is a grate 148, which is stationarily mounted within the support ring, to provide a bottom for the fuel receiver. The grate is, of course, freely apertured to support the unburned fuel, while permitting air to pass upwardly through the grate for the purpose of supporting combustion of the fuel.

Rotatably mounted on the support ring, in overlying relation to the stationary grate 148, is a shaker grate 150, having a handle 152 that projects exteriorly of the housing, where it can be grasped by a user for the purpose of rotating the shaker grate, thus to permit ashes A to pass therethrough. The ashes are removed from an ash receiver 156 secured to the lower end of the boiler jacket, with access to the ash receiver being provided through a dumping door 158 equipped with a handle 160 projecting exteriorly of the housing.

OPERATION Regardless of the type of burner used, the essential functioning of the thermoelectric generator remains unchanged. In every instance, there is the common characteristic wherein the thermoelectric modules,

which are relatively expensive to replace, are isolated from the combustion area 70. As a result, the modules cannot be over heated, due to the fact that rather than being heated directly by the hot products of combustion, they are heated through the intervening presence of the main boiler containing the vaporizable fluid F. At this point, it may be noted that any of various fluids can be employed within the main boiler jacket, and in a typical embodiment, the fluid may advantageously be that sold under the trademark Dowtherm by the Dow Chemical Company.

Assuming the combustion of the fuel in the open center space of the main boiler in the manner previously described with respect to the gaseous, liquid, and solid fuel burner structures, the fluid F within the vaporizing chamber 68 is heated to the point of vaporization. The vapor flows upwardly through the several radially extending tubes 118, passing through the several loops 101, to heat the hot junctions of the thermoelectric modules. In the process, the vaporized fluid condenses, gravitating to the condensate return chamber 66. It is important to note, in this regard, that the condensate return chamber 66, completely surrounding the vaporizing chamber 68, actually serves an an insulation wall for the vaporizing chamber cooperating in this respect with the insulation material surrounding the jacket.

The condensed vapor flows gravitationally in the exteriorly located chamber of the boiler jacket for return to the vaporizing chamber. Thus, on combustion of fuel within the open center area of the boiler, a selfcirculating system goes into operation, within the boiler, in the fashion of a thermal syphon. This can be closely regulated, to insure extremely uniform temper atures at the condensing pads or blocks located in thermal contact with the modules.

This heating cycle, with consequent generation of electrical energy, continues as long as sufficient heat is produced within the boiler to vaporize the fluid F.

It is understood that any of various means can be employed for the purpose of shutting down the generator, and in particular the burners, and in addition, with the exception of the solid fuels burner, re-ignition can be achieved automatically, following shut down, by circuitry well known in the burner art. With respect to those forms of burners utilizing the catalytic reactor, ignition occurs by initiation of a catalytic reaction of the type previously described herein, resulting from raising the temperature of the catalyst to its predetermined activity level, typically 400600F. This is usually accomplished by heating the catalyst by an electrical resistance element, not shown, or alternatively, by igniting the combustible mixture in the chimney, as for example by use of the previously mentioned spark plug, also not shown. This ignites the combustible mixture in the chimney, so that the flashback onto the catalyst heats it. In a short time, the burning ceases and the combustible mixture is reacted in the catalytic bed.

Readily installed, and equally readily replaceable fuel burners may be mounted within the lower portion of the boiler. Thus, a multi-fuel characteristic is incorporated in the structure, in that any of various burners can be employed, all of which, whether they burn gas, liquid, or solid fuels, operate efficiently to heat the liquid within the boiler jacket.

The design is such that with the same boiler and thermoelectric module structure, one can use any of a variety of burners, according to the requirements of the particular installation. Further. the boiler itself is individually replaceable. and this is true of the thermoelec tric module assembly. and each component of said assembly taken separately.

The two phase (liquidvapor) heat transfer mode using a boiler to provide vapor provides the ability to isolate and control the non-uniform heat source and large variation of temperature. By sensing the pressure and/or temperature of the boiling liquid one can easily control the thermal flux provided by the burner. ln the event of a runaway or over-temperature condition in the boiler the liquid can be vented by a simple pressure relief valve. thus insuring the prevention of excessive destructive temperatures at the thermoelectric modules. Thus, violent or extreme fluctuations of temperature in the burner area are dampened by the boiler to even out and control the temperature in the area of the thermoelectric modules.

Referring now to FIG. 8, a further embodiment of the invention is illustrated. ln the embodiment of FIG. 8, the invention employs a boiler which is of the reflux type. The embodiment of FIG. 8 includes a boiler jacket comprised of an inner heat conductive wall 211 of frusto-conical shape. and an outer wall 213 which is of generally cylindrical shape. The annulus formed therebetween is filled with the heat transfer fluid, the liquid form of which is indicated at 215. A temperature gauge 217 is provided in the outer wall 213 for monitoring the temperature in the annulus. A pair of

fluid level sensors

219 and 221 are provided also in the outer wall 213. The upper one 219 of the level sensors indicates that a maximum amount of fluid is present in the annulus. Failure of the lower level sensor 221 to sense fluid level indicates that there is an insufficient amount of fluid for proper operation.

In order to provide fluid to the annulus. a fill port 223 is provided, connected with the annulus through a suitable conduit 225. A pressure gauge 227 is provided in the conduit 225 for indicating pressure therein, and a drain valve 229 is provided for draining fluid from the annulus through a drain port indicated in phantom at 231.

The annulus for containing the heat transfer fluid 215 is closed at its lower end by a lower closing wall 233 joining the lower ends of the inner wall 211 and the outer wall 213. The upper end of the inner wall 211 has a frusto-conical section 235 of sharper angle extending inwardly and attached to the lower end of a cylindrical section 237. The section 237 extends upwardly to an upper closure wall 239 which joins the upper end of the cylindrical section 237 with the upper end of the outer wall 213. thus completing the closure of the annulus.

A plurality of pipes 241 extend upwardly from the upper end of the annulus containing the heat transfer fluid to a corresponding plurality of condensers 243. The condensers 243 provide condensation of the heat transfer fluid and transfer of heat to the thermoelectric elements 245. The vent lines 247 extend from the con densers 243 and terminate in an annular vent header 249. A conduit 251 extends from the vent header 249 to a relief vent valve 253. The relief vent valve 253 is set to vent excessive pressure buildup within the systern.

A heater, which may be of any suitable type, is placed in the spaced defined by the inner wall 21]. Heat gen erated in this heating chamber, indicated as 255, passes through the wail 211 into the heat transfer fluid 215.

The fluid is vaporized and passes upwardly through the conduits or tubes 241 to the condensers 243. There. the fluid condenses. and heat removed therefrom is transferred to the thermoelectric elements 245. Liquid heat transfer fluid then flows back down the walls of the condenser and tube 241, and returns to the annulus defined between the wall 211 and the wall 213. There it is reheated. This form of boiler is known as a reflux boiler. The returning liquid itself after condensation is heated by the oppositely flowing vapor. thus providing for high efficiency in the operation of the boiler. The cylinder 237 and the annular header 249 allows for the insertion of a cylindrical stack 257 to remove heat gases from the heat chamber 255. The stack 257 is shown in phantom in FIG. 8.

Although any type of suitable heating device may be utilized in the heating chamber 255, one particularly useful type of heating device is a catalytic heater of the design shown in FIG. 9. The catalytic heater in FIG. 9 is shown mounted in a portion of the apparatus of FIG. 8. The catalytic heater is constructed having a frustoconical inner wall 261 defining an exhaust plenum chamber 263. The lower end of the wall 261 is supported on a transverse plate 265 which is supported, by suitable means not shown. such that a clearance space exists between the plate 265 and a lower closure wall 266 which closes the lower portion of the generator.

A platinized ceramic material 267, is pelletized form, is supported between the inner wall 261 and the burner and the inner wall 211 of the generator. As may be more cleariy seen in FIG. 10, the outer surface of the inner wall 211 is provided with a plurality of fins 271, substantially increasing the surface area facing toward the heat transfer fluid. The inner surface of the wall 211 is formed with a plurality of short fins 273 and a plurality of longer fins 275. The pelletized material is contained between the inner wali 211 of the generator and the plenum wall 261. A plurality of holes 277 are provided in the lower plate 265, and the platinized ceramic material is arranged to permit a gas flow up through the holes 277 and through the peiletized material. The plenum wall 261 is made porous to allow gas to pass therethrough and into the plenum chamber 263. Exhaust gas then moves from the plenum chamber 263 up through the chimney 257.

The gaseous fuel for the catalytic burner is passed through a flow meter 279 and a pressure regulator 281 which controls the amount of fuel flow, and then through a thermal control valve 283 to a gas orifice jet 285. A pressure gauge 287 is also provided in the line 289 for indicating pressure therein. The thermai regulator valve 283 is controlled by a sensor 291 located in the heated wall 211 of the generator. The thermal regulator valve opens and closes in response to pressure transmitted from the sensor 291 through a capillary tube 293. The nozzle 285 is a suitable venturi type air inspirator. and the energy of the gas jet passing through the nozzle 285 is sufficient to entrain the proper amount of air for combustion and at the same time ensure optimum mixing. The gas with entrained air enters the region below the plate 265 and passes upwardly through the openings 277 into the catalytic bed 267. The catalytic bed. which may be comprised of platinized ceramic pellets. has the gas-air mixture pass through it in a diffused fashion and causes a catalytic reaction to take place immediately upon contact of the gas-fuel-air mixture with the bed. The heat release is transmitted to the inner wall 211 of the vaporizer or generator and the products of combustion (water vapor and CO which pass through the bed are collected in the plenum chamber 263 and exhausted through the stack 257.

Ignition for start up of the operation may be achieved by suitably heating the catalytic bed 267 to its ignition temperature or activity temperature (typically about 300F). This can be done simply by igniting the air-gas mixture issuing out of the exhaust stack 257 or by placement of small resistance electric heaters in the catalytic bed itself. When igniting the air-gas mixture issuing from the stack 257, a flame develops, flashing down the exhaust stack and burning on the inner face of the catalytic bed. This causes the bed to increase in temperature until the catalyst reaches activity level. At this point the air-gas combustion mixture begins to react in the bed and the flame extinguishes itself.

It may therefore be seen that the invention provides complete separation of the combustion process from the thermoelectric converter modules, enabling the utilization of any of a variety of combustion processes. Uniform heating of all thermoelectric modules takes place, and the design allows for modular construction for operation of any number of thermoelectric modules from a single central heat source. The heat transfer media can be vented and thereby prevents an overtemperature condition, eliminating any possibility of thermoelectric module damage. The catalytic heater described in FIGS. 9 and 10 provides a highly efficient form of heating for the thermoelectric generator of the invention, and when used in combination therewith, provides a highly efficient heat transfer to the vaporizer section of the thermoelectric generator,

Various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description and accompanying drawings. Such modifications are intended to fall within the scope of the appended claims.

What is claimed is:

l. A thermoelectric generator comprising, burner means for combusting a fuel in the presence of oxygen, a boiler including a cylindrical jacket containing a fluid to be heated and being disposed about a hollow center area for accommodating said burner means for heating of the fluid thereby, a plurality of thermoelectric devices for converting thermal to electrical energy, a plurality of conduit means for channeling the heated fluid from said jacket into thermal proximity of said devices and returning said fluid to said jacket, and heat absorbing means disposed in thermal contact with said conduit means for conducting heat therefrom to said devices, said cylindrical jacket including an inner chamber extending about said center area for heating of said fluid within the inner chamber, an outer chamber extending about the inner chamber in communication therewith, said conduit means including a series of loops individual to the several thermoelectric devices and extending generally radially from said jacket, and said burner means including a catalytic reactor extending within said center area of said boiler and incorporating an outer reaction surface disposed to complete combustion in close proximity to said jacket.

2. A thermoelectric generator as set forth in claim 1 wherein each of said loops is removably connected to said boiler independently of the remaining loops.

3. A thermoelectric generator as set forth in claim 1 wherein said center area extends the length of and opens upon the opposite ends of the boiler defining a flue for hot products of combustion emanating from said source.

4. A thermoelectric generator comprising, a generally cylindrical inner wall defining a combustion chamber, an outer wall surrounding said inner wall and forming with said inner wall an annulus surrounding said combustion chamber, said annulus having a closed lower end and containing a quantity of vaporizable heat transfer fluid therein, a plurality of pipes extending from the upper end of said annulus and arranged to conduct vapor of said heat transfer fluid upwardly from said annulus, a plurality of condensers, each in communication with a respective one of said pipes at the end thereof opposite said annulus, each of said condensers having a heat exchange surface to cause condensation of said vaporizable heat transfer fluid with said condensed fluid returning downwardly to said annulus via said pipes, a plurality of thermoelectric devices, each said thermoelectric device being in contact with a separate one of said condensers for receiving heat therefrom, a plurality of vent pipes extending from said condensers, and pressure relief means coupled to said vent pipes for relieving internal pressure when such pressure exceeds a predetermined level.

5. A thermoelectric generator as set forth in claim 4, wherein said vent pipes connect with a common header and a single vent pipe connects with said header for relieving excess internal pressure in the system.

6. A thermoelectric generator as set forth in claim 4, wherein each of said condensers includes a plurality of pins extending inwardly from one wall thereof.

7. A thermoelectric generator as set forth in claim 6, wherein each of said thermoelectric devices are connected in heat exchange relationship with a plurality of outwardly extending cooling fins.

8. A thermoelectric generator as set forth in claim 7, wherein a catalytic heater is located within said combustion chamber, said catalytic heater having a cylindrical wall in which combustion is initiated, said cylindrical wall being pervious to the passage of combustion gases and being disposed in close proximity to said cylindrical wall which defines the combustion chamber.

Claims

1. A THERMOELECTRIC GENERATOR COMPRISING, BURNER MEANS FOR COMBUSTING A FUEL IN THE PRESENCE OF OXYGEN, A BOILER INCLUDING A CYLINDRICAL JACKET CONTAINING A FLUID TO BE HEATED AND BEING DISPOSED ABOUT A HOLLOW CENTER AREA FOR ACCOMMODATING SAID BURNER MEANS FOR HEATING OF THE FLUID THEREBY, A PLURALITY OF THERMOELECTRIC DEVICES FOR CONVERTING THERMAL TO ELECTRICAL ENERGY, A PLURALITY OF CONDUIT MEANS FOR CHANNELING THE HEATED FLUID FROM SAID JACKET INTO THERMAL PROXIMITY OF SAID DEVICES AND RETURNING SAID FLUID TO SAID JACKET, AND HEAT ABSORBING MEANS DISPOSED IN THERMAL CONTACT WIHT SAID CONDUIT MEANS FOR CONDUCTING HEAT THEREFROM TO SAID DEVICES, SAID CYLINDRICAL JACKET INCLUDING AN INNER CHAMBER EXTENDING ABOUT SAID CENTER AREA FOR HEATING OF SAID FLUID WITHIN THE INNER CHAMBER, AN OUTER CHAMBER EXTENDING ABOUT THE INNER CHAMBER IN OMMUNICATION THEREWITH, SAID CONDUIT MEANS INCLUDING A SERIES OF LOOPS INDIVIDUAL TO THE SEVERAL THERMOELECTRIC DEVICES AND EXTENDING GENERALLY RADIALLY FROM SAID JACKET, AND SAID BURNER MEANS INCLUDING A CATALYTIC REACTOR EXTENDING WITHIN SAID CENTER AREA OF SAID BOILER AND INCORPORATING AN OUTER REACTION SURFACE DISPOSED TO COMPLETE COMBUSTION IN CLOSE PROXIMITY TO SAID JACKET.

4. A THERMOELECTRIC GENERATOR COMPRISING, A GENERALLY CYLINDRICAL INNER WALL DEFINING A COMBUSTION CHAMBER, AN OUTER WALL SURROUNDING SAID INNER WALL AND FORMING WITH SAID INNER WALL AN ANNULUS SURROUNDING SAID COMBUSTION CHAMBER, SAID ANNULUS HAVING A CLOSED LOWER END AND CONTAINING A QUANTITY OF VAPORIZABLE HEAT TRANSFER FLUID THEREIN, A PLURALITY OF PIPES EXTENDING FROM THE UPPER END OF SAID ANNULUS AND ARRANGED TO CONDUCT VAPOR OF SAID HEAT TRANSFER FLUID UPWARDLY FROM SAID ANNULUS, A PLURALITY OF CONDENSERS, EACH IN COMMUNICATION WITH A RESPECTIVE ONE OF SAID PIPES AT THE END THEREOF OPPOSITE SAID ANNULUS, EACH OF SAID CONDENSERS HAVING A HEAT EXCHANGE SURFACE TO CAUSE CONDENSATION OF SAID VAPORIZABLE HEAT TRANSFER FLUID WITH SAID CONDENSED FLUID RETURNING DOWNWARDLY TO SAID ANNULUS VIA SAID PIPES, A PLURALITY OF THERMOELECTRIC DEVICES, EACH SAID THERMOELECTRIC DEVICE BEING IN CONTACT WITH A SEPARATE ONE OF SAID CONDENSERS FOR RECEIVING HEAT THEREFROM, A PLURALITY OF VENT PIPES EXTENDING FFROM SAID CONDENSERS, AND PRESSURE RELIEF MEANS COUPLED TO SAID VENT PIPES FOR RELEIVING INTERNAL PRESSURE WHEN SUCH PRESSURE EXCEEDS A PREDETERMINED LEVEL.