US2725873A

US2725873A - Heat exchanger utilizing products of combustion as a heating medium

Info

Publication number: US2725873A
Application number: US275305A
Authority: US
Inventors: Walter Hellmuth
Original assignee: Worthington Corp
Current assignee: Worthington Corp
Priority date: 1952-03-07
Filing date: 1952-03-07
Publication date: 1955-12-06
Anticipated expiration: 1972-12-06

Description

Dec. 6, 1955 H. WALTER I HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTION AS A HEATING MEDIUM '7 Sheets-Sheet 1 Filed March 7, 1952 ZOFFUWZ ZOU MKOLZKMZ w UWm KUICQWI DUNZM JUDK HELLMUTH WALTER mmkamlmmm K71 INVENTOR.

Dec. 6, 1955 H. WALTER HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTION AS A HEATING MEDIUM 7 Sheets-Sheet 2 Filed March 7, 1952 FIG.2

IN VEN TOR.

HELLMU TH WALTER Dec. 6, 1955 H. WALT HEAT EXCHANGER UTILIZI COMBUSTION AS A HEATING MEDIUM Filed March 7, 1952 EHEATED AIR NG PRODUCTS 0F 7 Sheets-Sheet 3 HELLMUTH WALTER IN V EN TOR.

Dec. 6, 1955 H. WALTER HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTION AS A HEATING MEDIUM 7 Sheets-Sheet 4 Filed March 7, 1952 FIG. 6

INVENTOR.

H ELLMUTH WALTER Dec. 6, 1955 H. WALTER HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTION AS A HEATING MEDIUM 7 Sheets-Sheet 5 Filed March 7, 1952 FUEL GAS EJ'ECTOR INVENTOR.

ELLMUTH WALTER E TECTOR EXHAUST HOT GAS COLD GAS FIG] Dec. 6, 1955 H. WALTER HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTION AS A HEATING MEDIUM '7 Sheets-Sheet 6 Filed March 7, 1952 FIGJO INVENTOR.

H ELLM UTH WALTER Dec. 6, 1955 H. WALTER 2,725,873

HEAT EXCHANGER UTILIZING PRODUCTS OF COMBUSTION AS A HEATING MEDIUM Filed March 7, 1952 7 Sheets-Sheet 7 FUEL GAS 99 l 98 93 aw? HEATER x 94 9 a ,9, H, f4 I j ff h I03 l we 97 /4 |O| A EXHAUST l if; x I04- F I 86 l 9 3? H 9 05 5 8 g s| 95 t a l I 96 10s 89 L 8 -95 1 5 AIR I02 38 TO 84 TURBINE 92 90 9| 83 FROM O COMPRESSOR H0 8 IZI H4- TO PlPE LINE j P REG-ENERATQR INVEN TOR.

GUI-.

FROM TURBINE EXHAUST United States Patent HEAT EXCHANGER UTILIZING PRODUCTS 0F CONIBUSTION AS A HEATING MEDIUM Hellmuth Walter, Upper Montclair, N. J., assignor to Worthington Corporation, Harrison, N. J., a corporation of Delaware Application March 7, 1952, Serial No. 275,305 16 Claims. 01. 126-109) This invention relates to heat exchangers and more particularly to a fuel fired heater wherein the medium to be heated is circulated through heat exchange tubes countercurrent to hot gases produced by combustion of fuel in the shell containing the tubes.

The fuel fired heater or heat exchanger of the present invention is particularly adaptable for use in a gas or vapor compression unit for compressing flowing gases or vapor in an isolated system or unit, wherein the energy required for compression is derived from the heat of combustion of fuel burned in one of the components of the system as disclosed in my copending applications, Serial No. 181,512, filed August 25, 1950, and Serial No. 257,303, filed March 7, 1952. However, the heat exchanger or fuel fired heater of the present invention is not limited to such use, the present invention being limited to the fuel fired heater or exchanger per se, which may be adapted to any use where practical.

An object of the present invention is to provide for a heat exchanger which provides for countercurrent flow of gases, that is, of the heating and heated mediums insuring the highest permissible value of mean temperature difference and least area of heat transfer surface, and to provide for minimum loss of pressure of the gases with a given value of overall conductance by flow of the gas longitudinally of the heat transfer surfaces with least practical changes in flow direction. A further object is to insure by recirculation of a part of the cooled-down combustion gases, that the highest permissible mean temperature difference is not exceeded.

' With these and other objects in view, as may appear from the accompanying specification, the invention consists of various features of construction and combination of parts, which will be first described in connection with the accompanying drawings, showing a heat exchanger utilizing products of combustion as a heating medium of a preferred form embodying the invention, and the features forming the invention will be specifically pointed out in the claims.

In the drawings:

Figure l is a diagrammatic layout of a gas or vapor compressing unit showing one application of the heat exchanger or heater.

Figure 2 is a side elevation of one form of the heat exchanger or heater.

Figure 3 is a horizontal section through the heat exchanger of Figure 1 taken on the line 3-3 of Figure 4.

Figure 4 is a vertical section taken on the line 44 of Figure 3.

Figure 5 is a side elevation of another form of the heat exchanger or heater.

Figure 6 is a horizontal section through the heat exchanger or heater shown in Figure 5 and taken on the line 6-6 of Figure 7.

Figure 7 is a vertical section taken on the line 77 of Figure 6. I

Figure 8 is a side elevation of still another form of the heat exchanger or heater.

2,725,873 Patented Dec. 6, 1955 ice Figure 9 is a horizontal section through the heat exchanger or heater of Figure 8 and taken on the line 9-9 of Figure 11.

Figure 10 is a horizontal section through the heat ex. changer or heater taken on the line 10-10 of Figure 11, an

Figure 11 is a vertical section through the heat exchanger or heater shown in Figure 8.

Figure 1 of the drawings shows a diagrammatical layout of a compressing unit for compressing flowing gas or vapor and generically the system includes a line pipe 1 through which the flowing gas or vapor to be compressed flows. The gas or vapor is taken from line 1, through a pipe 2 and delivered to the suction of a compressor 3. Part of the gas from the pipe 2 is extracted through an extraction pipe 4 and passes through one or more regenerators shown at 5, after which it passes into the fuel fired heater or heat exchanger 6 which constitutes the present invention. The heated extracted gas is delivered from the fuel fired heater or heat exchanger 6 through a pipe 7 to a turbine 8 which drives the compressor 3. The compressed gas is returned to the pipe line 1 through a suitable connection 9. This compressing unit is specifically disclosed and claimed in my companion application, Serial No. 275,301, filed March 7, 1952 and Serial No. 275,302, also filed March 7, 1952, and is shown herein and described generically merely for the purpose of showing one use of the heat exchangers forming the subject matter of the present invention.

In Figures 2 to 4 inclusive of the drawings, the fuel fired heat exchanger is illustrated as including a shell 10 which is preferably cylindrical in shape. The lower end of the shell 10 is enclosed by a closure head 11 which is, in the main, preferably formed of heat insulating material and the opposite end of the shell 10 is enclosed by a removable head 12.

A pair of doughnut shaped

tubular rings

13 and 14 are carried by the closure 11 Within the shell of the heat exchanger and the ring 13'has an inlet 15 for the gas or vapor to be heated communicating therewith, while the ring 14 has an outlet 16 for the heated gas'or vapor.

An annular or circular partition 17 is located within the shell 10 and extends from the closure 11 to the inner surface 18 of the heat insulating filler 19 of the removable head 12 forming a central combustion chamber 20 and an outer annular heat exchange chamber 21. The partition 17 is provided 'with a plurality of transverse openings 22 at its lower end, that is, the end remote from the removable head 12 which openings establish communicationbetween the inner chamber 20 and the outer annular chamber 21. I

A plurality of substantially inverted U-shaped heatexchange tubes 23 have theirinlet ends connected to the doughnut ring 13and their outlet ends connected to the doughnut ring 14. The bends 24 of the tubes extend through the annular partition 17 as clearly shown in Fig ure 4 of the drawings and thus one of the legs of each of the tubes 23 is located in the central chamber 20 while the other leg is located in the annular chamber 21.

The removable head 12 is in the major portion filled with a filler of heat insulating material shown at 19 which has a passage 25 extending axially therethrough and opening into the central combustion chamber 20. The passage 25 is provided for admitting air into the combustion chamber for mixture withfuel to provide a combustible mixture within the chamber 20.

In the system shown in Figure 1 of the drawings the air which is admitted to the shell 10 through the passage 25 is preheated in an-air heater 26 although this is not necessary to the operation of the heat exchanger per se. An inlet pipe 27 for fuel gas or vapor extends into the head 12 and axially downwardly through the opening 25 having its outlet end flaredas shown at 28. The air passage 25 is substantially Venturi shaped, that is, it de creases in cross sectional area for a portion of its length inwardly of its inlet and graduallyincreases inarea from the point of minimum cross sectionalareato theoutlet, although the area at the outlet is of course -restricted by the flared. end 28-of the. fuel inlet pipe 27 so that the air will be deflected inwardly and outwardly as it enters the combustion chamber 20. A substantially conical defiector 29 is located in the flared outlet end 28 of the fuel inlet pipe for directing the fuel gas or vapor into the cornbustion chamber. As shown in Figure 4 of the drawings, igniting means in the form of an ordinary spark plug 30 is provided forigniting the mixture of fuelgas or vapor and air in the combustion chamber to cause a burning thereof. It is to be understood, however, that any suitable type of ignition means may be provided.

The burning combustible fuelin the combustion chamber 20 passes downwardly therein longitudinally of the inner legs of the U-shaped tubes 23 in countercurrent flow to the flow of the gas or medium to be heated through the tubes. At the bottom of the shell the products of combustion pass through the openings 22 into the annular outer chamber 21 and pass upwardly therein longitudinally of the tubes 23 and in a countercurrent direction to the downward flow of medium to be heated flowing through the tubes. The products of combustion exhaust from the shell 10 near the upper end thereof through a plurality of circumferentially spaced openings 31 in which an annular exhaust passage 32 formed by a ring formed upon or attached to the outer surface of the shell 10. From the exhaust ring 32 the products of combustion exhaust through an outlet 33.

As is clearly shown in Figure 4 of the drawings, the closure 11 and the removable head 12 are both detachably connected to the shell 10 so that in case of repair or replacement of the ignition means or any of the parts carried by the head 12 the head may be removed without disturbance of the shell 10 and the connections with the pipes and 16. Such removal of the head 12 will also permit access to the tubes 23.

The form of the invention shown in Figures 5, 6 and 7 differs in some degree from the form of the invention shown in Figures 2 to 4 inclusive, but the principles of operation and the general principles of construction are similar.

This form of the invention includes a shell 50, one end of which is closed by a closure 51 and'the other end by a removable head 52. Tubular doughnut rings 53 and 54 are located within the shell-and they have inlet and

outlet connections

55 and 56 respectively, connected thereto for the inlet and outlet of the medium to be heated. Heat exchange tubes 57 have their inlet ends connected to the doughnut ring 53 and their outlet ends connected to the doughnut ring 54. The tubes 57 are substantially U-shaped and their bends extend through the annular partition 58 located within the shell to provide the central combustion chamber 59 and theannular heat exchange chamber-60 with the inlet upflowing legs of the U-shaped tubes located in the central combustion chamber 59 and the downflowing outlet legs of the tubes located in the heat exchange chamber 60.

In this form of the invention a second annular partition 61 is located within the shell forming an annular air passage chamber 62 to the lower end of which air is admitted through an inlet 63. The'annular air passage chamber 62 is closed at its bottom or at its end adjacent to the doughnut rings 53 and 54 and its upper end is constricted as shown at 65 and opens intoan annular air passage 66 formed in the removable head" 52 by the passage-forming heat insulation member 67 against which the upper end of the annular-partition 58abuts. 'The annular air passage 66 opens intoan axial airpassag'e 68, the

flared' outlet endof which '.'-opens inttri-thte fcombustion chamber 59 for deliveringthe-"air"to the combustion chamber. Fuel, gas or vapor is admitted to the combustion chamber 59 for mixture with the air in the combustion chamber through a fuel gas or vapor inlet 69 extending axially through the opening or passage 68. A substantially conical spreader 70 is located in the fuel gas inlet pipe 69 with its base located at the outlet end of the gas inlet pipe. Fuel ignition means 71, which is shown in the form of a spark plug is carried by the spreader 70 and extends into the combustion chamber 59 for igniting the mixed fuel gas or vapor and air to burn the water in the combustion chamber- 59 to provide heat for heating the medium flowing through the tubes 57.

The annular partition 58 has openings 72 in its lower end through which the products of combustion pass from the combustion chamber 59 into the annular heat exchange chamber 60. The products of combustion flow upwardly through the heat exchange chamber 60 in countercurrent flow longitudinally of the outer legs of the tubes 57 and passes out of the annular chamber 60 through a plurality of circumferentially spaced openings 74 into an annular exhaust passage 75. The annular exhaust passage 75 is in the form of a substantially semi-circular ring on the outer surface of the partition 61 and it has an outlet connection 76 connected thereto.

The provision of the annular air passage 62 which, in effect, is a concentric jacket, serves to cool the walls of the unit. The upper outlet end of the annular partition 61 and the wall of the shell 50 is so constructed as to produce a jet or ejector effect as the air which is heated through the partition 61 flows upward into the annular passage 66. This action picks up a small quantity of the products of combustion and stimulates recirculation of relatively cool-products of combustion and brings about a reduction in the temperature within the combustion chamber.

The form of the invention shown in Figures 8 to 11 inclusive illustrates in a single unit the combination of a fuel fired heat exchanger similarto that disclosed in Figures 1 to 7 inclusive and a non-fuel fired heat exchanger.

This form of the invention comprises a main shell 80 which is composed of the shell 81 of the fuel fired section, the shell 82 of the non-fuel fired heat exchange section and the central connecting element 83 interposed between the two

shells

81 and 82.

The fuel fired heat exchange section of this form of the invention includes the closure plate 84 and the removable top or cover 85. An annular partition 86 corresponding to the

partitions

17 and 58, is located within the shell 81 forming the inner combustion chamber 87 and the outer annular heat exchange chamber 88. Of course, in all of the forms of the invention the inner combustion chambers are actually and, in effect, heat exchange chambers, as Well as the outer annular chambers. Substantially U-shaped tubes 89 are carriedby the closure plate 84 with their inlet ends opening out through the closure plate, their bends extending through the partition 86 and with their outlet legs in the heat exchange chamber 88 and their outlet ends opening through the closure 84 into an annular outlet passage 90 formed in the chamber within the central connecting unit 83. The central connecting unit 83 has anannular partition 91 formed therein forming a central chamber or passage 92 in which the medium to be heated enters and from which it passes into the inlet ends of the tubes 89. The removable head 85 has an air passage 93 formed therein by the member or block 94 of insulating material. The inlet side of the air passage 93 opens into the annular air passage 95 formed within the shell 81 about the annular heat exchange passage 88 by the partition 96. As clearly shown in Figure 11 of the drawings the outlet end of the annular air passage 95 is constricted as shown at 97 and a portion of the passage 93 opens into the annular. heat exchange chamber 88 the same as passage 66in Figure -7 of the drawings opens partlyintoatheannularheat exchange chamber 60 with theou'tletend of-the-annular air passage 62 being constricted. The air passage 93 opens through an axial opening 98, the outlet endof which is flared into the combustion chamber 87 and the pipe 99 for inlet of fuel gas into the combustion chamber 87 is carried by the removable head 85 and extends axially through the opening 98. A spreader 100 is located in the fuel gas inlet pipe 99 and it carries suitable ignition means 101 for igniting the mixture of air and gas in the combustion chamber 87. The products of combustion pass downwardly in the combustion chamber 87 and through the openings 102 in the annular partition 86 into the annularheat exchange chamber 88 from which they pass through circumferentially spaced openings 103 into the annular exhaust passage 104 and out of the passage through the outlet 105. Air is admitted to the annular air passage 95 through an air inlet 106.

The non-fuel fired heat exchange section of the form of the invention shown in Figures 8 to 11 includes the shell 82 having a transverse partition or end 110 which forms the lower part of the chamber intermediate the

sections

81 and 82. A plurality of U-shaped tubes 111 are carried by the partition 110. The inlet ends of the tubes open into the annular inlet chamber 112 formed about the circular or annular partition 91 and separated from the outlet passage 90 by the transverse partition 113. Theroutlet ends of the U-shaped tubes 111 open into the central passage 92 formed by the annular partition 91 so that the medium to be heated which enters the annular inlet chamber 112 through the inlet 114 passes downwardly through the outermost legs of the U- shaped tubes 111 and upwardly through the inner legs into the passage 92 and from the passage 92 into the inlet ends of the U-shaped tubes 89. An annular bafile 115 is located within the shell 82 and extends downwardly between the inlet and outlet legs of the U-shaped tubes 111. The inlet pipe 116 extends axially into the shell 82 to a point near the transverse partition 110 so that the heating medium entering the shell 82 from the inlet pipe or tube 116 is deflected laterally and downwardly by the partition 110. The laterally and downwardly flowing heating medium passes longitudinally along the inner legs of the tubes 111 in counter-flow direction to the flow of the medium to be heated through the tubes and passes around the lower end of the baffie 112 and upwardly along the outer inlet legs of the U-shaped tubes 111 in counter-flow direction to the flow of the medium to be heated flowing through these legs. The heating medium passes out of the shell 32 through a plurality of circumferentially spaced openings 117 into an annular exhaust passage 118. The exhaust passage 118, like the

exhaust passages

32, 75 and 104, is formed by an arcuate annular member 120 attached to or formed upon the outer surface of the shell 82. An outlet pipe 121 is connected to the exhaust passage 118.

It will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown, but that they may be widely modified with in the invention defined by the claims.

What is claimed is:

l. In a fuel fired heat exchanger, a shell having an inlet for combustible fuel at one end thereof, an annular partition in said shell forming an inner combustion chamber and an annular outer heat exchange chamber, said inlet for combustible material communicating with said inner combustion chamber, said annular partition having openings therein near the end of the shell remote from said fuel inlet, a' plurality of substantially U-shaped tubes in said shell and having their inlets and outlets at the ends of the shell remote from said fuel inlet, the bends of said tubes extending through said annular partition whereby one leg of each of the tubes will be located in said inner combustion chamber and the other leg of each tube will be located in the outer annular heat exchange chamber said shell having an outlet for gases of combustion therein, said outlet opening into said heat exchange chamber adjacent to the end of the shell remote from said openings in said annular partition.

2. A fuel fired heat exchanger as claimed in claim 1 wherein said shell comprises a central cylindrical portion open at both ends and removable closure heads for the open ends, and wherein said inlet for combustible fuel is carried wholly by one of said removable end closure heads.

3. A fuel fired heat exchanger as claimed in claim 1, a pair of doughnut-shaped tubular rings in the end of said shell remote from the fuel inlet, the inlet ends of said U-shaped tubes connected to one of said rings and the outlet ends of the tubes connected to the other of said rings, an inlet for fluid to be heated connected to the tubular doughnut-ring in which the inlet ends of said tubes are connected and an outlet for fluid to be heated connected to the tubular doughnut-ring to which the outlets of said tubes are connected.

4. A fuel fired heat exchanger as claimed in claim 1 including a tubular doughnut ring connecting the inlets of all of said tubes and a second tubular doughnut ring connecting the outlets of all of said tubes, an inlet for fluid to be heated connected to said first tubular doughnut ring, and an outlet for fluid to be heated connected to said second tubular doughnut ring.

5. A fuel fired heat exchanger as claimed in claim 1 wherein the end of said shell having the inlet forcom bustible fuel has an annular air passage therein, a heat insulating member in said shell end and provided with an axial opening opening into the inner chamber and communicating with said air passage to form an inlet for air to the inner chamber, a fuel gas inlet pipe extending through said air inlet, means for igniting the fuel gas in said inner chamber, and a second annular partition in said shell forming an air passage about said outer chamber and having communication with said annular air passage in the fuel inlet end of the shell. Y

6. A fuel fired heat exchanger as claimed in claim 1 wherein the end of said shell having the inlet for combustible fuel has an annular air passage therein, a heat insulating member in said shell end and provided with an axial opening opening into the inner chamber and communicating with said air passage to form an inlet for air to the inner chamber, a fuel gas inlet pipeextending through said air inlet, means for igniting the fuel gas in said inner chamber, and a second annular partition in said shell forming an air passage about said outer chamber and having communication with said annular air passage in the fuel inlet end of the shell, a tubular doughnut ring connecting the inlets of all of said tubes and a second tubular doughnut ring connecting the outlets of all of said tubes, an inlet for fluid to be heated connected to said first tubular doughnut ring and an outlet for fluid to be heated connected to said second tubular doughnut ring.

7. A fuel fired heat exchanger as claimed in claim 6 including means forming an exhaust outlet passage for products of combustion, said means located in said annular air passage adjacent to said heat insulating member and provided with inlets opening into the annular outer heat exchange chamber and an outlet opening outwardly of said shell.

8. A heat exchanger as claimed in claim 1 including an exhaust passage-forming ring carried by said shell adjacent to the fuel inlet, said shell having an exhaust outlet opening therein opening from said heat exchange chamber into said exhaust passage-forming ring, whereby products of combustion will travel in one direction throughout said combustion chamber and in a reverse direction throughout said heat exchange space to said exhaust outlet.

9. In a fuel fired heat exchanger, a shell, an annular partition in said shell forming an inner combustion chamber and an outer annular chamber about said combustion chamber, a heat insulation element spaced inwardly of one end of said shell to form an annular air passage space and disposed to close the end of said annular partition adjacent thereto, said heat insulation element provided with an air inlet passage opening into said combustion chamber at' one end and in communication with said annular air passage space atthe other end, a second annular partition in said shell about said outer annular chamber formingan air passage with said shell, said second annularpartition defining an openingto provide communication between said air passage and said annular air passage space, said shell having an air inlet communicatingwith said partition formed air passage, said first mentioned annular partition having an opening therein spaced from said air inlet to provide communication between said inner combustion chamber and said outer annular chamber, an inlet for fuel gas opening into said combustion chamber, a plurality of substantially U-shapedtubes having their ends extending through said first-named annular partition and their spaced legs located in said combustion chamber and said annular outer chamber, said shell having'an outlet for gases of combustion therein opening into said outer annular chamber, inlet means for fluid to be heated connected to the inlet ends of said substantially U-shaped tubes and outlet means for fluid to be'heated connected to the outlet ends of substantially U-shaped tubes.

10. In a heat exchanger, a shell, a pair of spaced transverse partitions in said shell intermediate its ends and forming an intermediate chamber and heat exchange chambers 'on each side of each intermediate chamber, a centrally located annular partition in said intermediate chamber forming a central passageway, a transverse partition in said intermediate chamber outwardly of said central annular partition and'forming an inlet passage and an outlet passage, a plurality of tubes in one of said heat exchangeehambers and having their inlets communicating with said inlet passage and their outlets communicating with said central passage, and a plurality of tubes in the other of said heat exchange chambers having their inlets communicating with said central passage and their outlets communicating with said outlet passage inlet means for fluid to be heated communicating with said inlet passage,"and outlet means for the fluid to be heated communicating with said outlet passage.

11. A heat exchanger as claimed in claim wherein one of said heat ex'change'ehambers forms a combustion chamber, an inlet for air to said combustion chamber, an inlet for fuel gas to the combustion chamber, said shell provided with an outlet for combustion gases communicating with said combustion chamber, and means for igniting fuel gas in said combustion chamber.

12. A heat exchanger as claimed in claim 10 wherein one of said heat exchange chambers forms a combustion chamber, an inlet for air'to said combustion chamber, an inlet for fuel gas to the combustion chamber, means for igniting fuel gas in said combustion chamber and said shellprovided with an outlet for gases of combustion communicating with said combustion chamber, an inlet pipe for a heating medium extending from one end of the shell into the other of said heat exchange chambers for directing incoming heating medium into the chamber about the tubes thereinat a point near one of said transverse-partitions, an outlet forthe heating medium, and means for directing the heating medium longitudinally'along the "tubes from the point of inlet to said outlet.

13. A heat exchanger as claimed in claim 10 wherein an annular partition is located in each of said heat exchange chambers, andwherein said tubes are substantially U shaped with their bends extending through the annular partitions in the heat exchange chambers and with the leg portions of the U-shaped tubes located one on each side of said annular partitions, the inlet ends of the substantially U-shaped tubes in one of said heat exchange chambers communicating .with said inlet passage and th'eir outlet ends communicatingwith said central passage; the --inl e t-1endsofsaid substantially-- U -shapd 'tubes in the *ot-h'e'r of saidheafexchange chambers communicating with "said central passage and their'outlet ends communicating with said outlet passage.

14. 5 A fuel fired-heat exehanger as claimed in claim 10 wherein a block isrnounted in the end of one of said heat exchangers remote from said' intermediate chamber, a first annularpartition insaid block containing heat exchange chamber and engaging-saidbloek to form an inner combustion chamber andan outer heat exchange space in the chamber, an air inlet for said combustion chamber, an inlet for fuelgas to the combustion chamber, means for igniting fuel gas in said combustion chamber, said shell provided with an outlet for gases of combustion communicating with said'heat exchange chamber, and said annularpartition having openings therein to allow combustion gases to pass from said inner combustion chamber to said outer heat exchange space in the block containing heat exchange chamber.

15. A fuelfire heat exchanger-as claimed in claim 10 wherein a block is mounted in the end of one of said heat exchange chambers remote from said intermediate chamber, a first annular partition in said block containing heat exchange chamber and engaging said block to form an inner combustion chamber and an outer heat exchange space in the block containing heat exchange chamber, a second annular partition in said block containing heat exchange chamber forming an annular air chamber about said heat exchange space, an air inlet to said annular chamber, said block shaped to provide an annular air passage having inlet communication with said air chamber and outlet communieationwith said combustion chamber, an inlet for fuel gas to said combustion chamber, means for igniting fuel gas in said combustion chamber, said shell provided with an outlet for combustion gases communicating with said heat exchange space, and said first annular partition havingopenings therein to allow combustion gases to pass from said combustion chamber into said outer heat exchange space in said block containing heat exchange chamber.

16. A fuel fired heat exchanger as claimed in claim 10 wherein a block is mounted in the end of one of said heat exchange chambers remote from said intermediate chamber, a first annular partition in said block containing heat exchange chamber and engaging said block to form an inner combustion chamber and an outer heat exchange space in the chamber, a second annular partition in said block containing heatexchange chamber forming an annular air chamber about said heat exchange space, an air inlet to said annular air chamber, said block shaped to provide an annular air passage having inlet communication with said air chamber and outlet communication with said combustion chamber, an inlet for fuel gas to said combustion chamber, means for igniting fuel gas in said combustion chamber, means forming an exhaust outlet passage for products of combustion, said means located in said air chamber adjacent the block carrying end of the heat exchange chamber and provided with inlets opening into the heat exchange space and with outlets opening outwardly of said shell, and said first partition provided with openings therein at its end remote from said block whereby products of combustion flow from the combustion chamber into and through said heat exchange space of the block containing heat exchange chamber.

References Cited inthe file of this patent UNITED STATES PATENTS

Claims

1. IN A FUEL FIRED HEAT EXCHANGER, A SHELL HAVING AN INLET FOR COMBUSTIBLE FUEL AT ONE END THEREOF, AN ANNULAR PARTITION IN SAID SHELL FORMING AN INNER COMBUSTION CHAMBER AND AN ANNULAR OUTER HEAT EXCHANGE CHAMBER, SAID INLET FOR COMBUSTIBLE MATERIAL COMMUNICATING WITH SAID INNER COMBUSTION CHAMBER, SAID ANNULAR PARTITION HAVING OPENINGS THEREIN NEAR THE END OF THE SHELL REMOTE FROM SAID FUEL INLET, A PLURALITY OF SUBSTANTIALLY U-SHAPED TUBES IN SAID SHELL AND HAVING THEIR INLETS AND OUTLETS AT THE ENDS OF THE SHELL REMOTE FROM SAID FUEL INLET, THE BENDS OF SAID TUBES EXTENDING THROUGH SAID ANNULAR PARTITION WHEREBY ONE LEG OF EACH OF THE TUBES WILL BE LOCATED IN SAID INNER COMBUSTION CHAMBER AND THE OTHER LEG OF EACH TUBE WILL BE LOCATED IN THE OUTER ANNULAR HEAT EXCHANGE CHAMBER SAID SHELL HAVING AN OUTLET FOR GASES OF COMBUSTION THEREIN, SAID OUTLET OPENING INTO SAID HEAT EXCHANGE CHAMBER ADJACENT TO THE END OF THE SHELL REMOTE FROM SAID OPENINGS IN SAID ANNULAR PARTITION.