US3224502A - Finned envelope heat exchanger - Google Patents

Description

Dec. 21, 1965 R. N. WALLACE 3,224,502

FINNED ENVELOPE HEAT EXCHANGER Filed May 29, 1965 I5 Sheets-Sheet l EUDOLF M W/ILLHC? 7- /Ma/ HTTUE/VV Dec. 21, 1965 R. N. WALLACE 3,224,502

FINNED ENVELOPE HEAT EXCHANGER Filed May 29, 1963 3 Sheets-Sheet 2 H77'0E/VEY Dec. 21, 1965 Filed May 29, 1963 R. N. WALLACE FINNED ENVELOPE HEAT EXCHANGER 3 Sheets-Sheet 5 ilited States Patent Office 3,224,502 Patented Dec. 21, 1965 3,224,502 FINNED ENVELOPE HEAT EXCHAN'GER Rudolf N. Wallace, Glastonbury, Conn, assignor to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Filed May 29, 1963, Ser. No. 285,547 12 Claims. (Cl. 165-82) This invention relates to heat exchangers and particularly to radiators for transferring heat from one fluid stream to another.

A most difiicult problem in heat exchange is the transfer of heat from a liquid to a gas. One of the most emcient radiator configurations for transferring heat from a liquid to a gas is the so-called finned-plate type which has a plurality of hollow envelopes, each of which contains a relatively thin layer of one fluid stream confined between closely spaced plates of the envelope. The spaced plates are finned on their exterior surfaces to provide extended surface area in the other fluid stream. However, heat exchangers of the finnedplate type have not been satisfactory under severe operating conditions, such as for liquid metal radiators. I believe their shortcomings have been due to previously used methods of interconnecting passages and of providing mechanical restraint against pressure and vibration, requiring matrices which were solidly welded or brazed together. Because of their complexity, these cores have been very diflicult to make completely leak-free in initial assembly and, when loaded pressurewise and thermally, they have not been sufficiently flexible to absorb, without failure, the strains which are produced by thermal and pressure gradients throughout the core matrix and headers.

It is therefore an object of this invention to provide a radiator having a plurality of finned-plate heat transfer elements which is easy to manufacture and which permits relative motion between elements so as to relieve the structure of the destructive stresses which result when thermal strains and pressure deflections are rigidly restrained.

Specifically, the radiator of this invention provides a number of U-shaped finned-plate elements, identical except for header details, each of which is supported independently by means of inlet and outlet connections to circular manifolds. The elements are self-supporting with respect to collapsing pressures and are supported against bursting pressures by adjacent elements. Each element is free to expand longitudinally and transversely as required by thermal expansion and pressure strain. Only one manifold is fixed in the axial direction. The other is free to position itself according to differences in the length of the hot and cold legs of the U-shaped finned elements.

It is a further object of this invention to provide an improved radiator of the type above outlined.

A further object of the invention is generally to improve radiators.

These and other objects and advantages of the invention will be pointed out in connection with the detailed description of one illustrative embodiment thereof shown in the accompanying drawings in which a liquid metal to air radiator is shown by way of example. In these drawings:

FIG. 1 is a side elevation of the radiator embodying the present invention shown between the compressor and turbine sections of a gas turbine engine, part of the engine casing and radiator being broken away to facilitate illustration.

FIG. 2 is an enlarged sectional view on line 22 of FIG. 1.

FIG. 3 is a section on line 33 of FIG. 1 on a larger scale.

FIG. 4 is a section on line 44 of FIG. 1 on a very much larger scale showing the finned envelopes in section and illustrating their position relative to the tube openings in the headers.

FIG. 5 is an exploded perspective view illustrating one of the U-shaped finned-envelope elements, the major part of one leg of the U, which is duplicative, being broken away to facilitate illustration.

FIGS. 6, 7, and 8 are sectional views taken on lines 66, 7-7, and 8-8 respectively, of FIG. 4 illustrating the three types of headers used for connecting the envelopes of the outlet manifold.

FIG. 9 is a detailed sectional view through one of the envelopes; and FIGS. 10 and 11 are detailed views showing one of the supports for the outlet manifold.

In FIG. 1 there is shown the intermediate section 12 of a gas turbine engine between the compressor section 14 and the turbine section 16 of the engine. Section 12 includes the usual inner cylindrical casing member 18 through which the engine shaft extends and the outer casing member 20 which forms, with member 18, an axial passage 22 which is torus-shaped in cross-section. Passage 22 usually contains a circular arrangement of axially directed burner cans. Herein this passage is 0ccupied by the radiator, generally indicated at 24, with which this invention is concerned.

The engine casing includes transition sections 26 and 28 between the compressor and passage 22 and between passage 22 and the turbine inlet. Transition section 26 receives the compressor discharge from annular passage 30 and directs it into passage 22, divergent annular walls 32 and 34 being connected between the walls of compressor discharge passage 30 and the cylindrical casing walls 18 and 20, respectively. On the downstream side of the radiator, convergent annular walls 36 and 38 connect cylindrical casing walls 18 and 20, respectively, with tie anular turbine inlet passage 40.

Radiator 24 includes an inner annular manifold 42 and an outer annular manifold 44. Herein, 42 is the outlet manifold and 44 is the inlet manifold for the liquid metal. Inlet manifold 44 is supported on outer casing 20 by four supporting devices 46, equally spaced about its periphery. One of these devices is shown in FIG. 1 and in greatest detail in FIGS. 10 and 11. Each of these devices includes a shoe 46a having an arcuate outer surface which conforms to the inner surface of outer casing member 24) and is welded thereto. The shoe has two parallel inwardly directed flanges 46b spaced to form a radial slot 460 which extends transverse to the longitudinal axis of the engine casing to receive a web 46d welded to manifold 44.

The liquid passages of the radiator consist of a plurality of like, generally radially disposed finned-plate elements in the form of U-tubes, the ends of which are connected to manifolds 42 and 44. Each tube includes parallel elongated legs 52 and 54 flattened and curved normal to their length. Legs 52 and 54- are connected together at their downstream ends by headers 56 and 58 respectively and header connectors 60 (FIG. 5). At their upstream ends the legs 52 are connected by successive groups of headers 64, 64a and 64b and header tubes 65 to inner manifold 42. It will be noted that inner and outer manifolds 42 and 44 have annular flattened faces adjacent the radiator. Face 70 of manifold 42 is provided with three annular rows of staggered tube openings 72, 74 and 76 arranged to receive header tubes 65 of headers 64, 64a and 64b, respectively (FIGS. 6, 7 and 8) of successive groups of legs 52 about its periphery. Outer manifold 44, having a longer peripheral dimension, is similarly provided with two annular rows of staggered openings 78 and 30 arranged in its annular face 70 to receive in a like manner staggered annular rows of header tubes 82 leading to headers 81 of alternate legs 54. One of these tubes is shown in FIG. 1.

Inner manifold 42 is provided with an outlet pipe 84 and outer manifold 4-4 is provided with a similar inlet pipe 86 for the liquid which, in this radiator, is liquid metal, these inlet and outlet pipes being connected, as shown herein, to the manifolds 42 and 44 at the bottom of the engine.

It will be noted from FIG. 1 that the liquid containing elements of the radiator and their connected manifolds 42 and 44 do not completely fill the torus-shaped axial passage 22 between casing members 18 and 20, an inner annular passage 88 being provided between casing member 18 and the radiator elements and an outer annular passage 90 being provided between casing 20 and the radiator elements. An annular seal 92 (FIG. 4) closes off passage 96 at the upstream end of the radiator, this seal comprising an annular flange 92a carried by the radiator which is received in a slot formed by parallel flanges 92b on a continuous annular shoe which has a sliding connection with casing member 20.

A similar annular seal 94 having an annular shoe slidable on casing member 18 is carried by the radiator at its downstream end which closes off the annular passage 88. The seals 92 and 94 are very similar in construction to the support devices 46 for manifold 44 shown in detail in FIG. 11 except that the annular shoe is not welded to the casing member. As a result, air discharged from the compressor entering axial passage 22 is forced inwar-dly into passage 88 from which it is forced to flow substantially radially through the spaces between the plate elements of the U-tubes into passage 90 and into turbine inlet passage 40.

To insure this generally radial flow and to increase the surface area of the plate-like elements of the tubes, corrugated panels 96 are brazed or welded to both outer surfaces of legs 52 and 54 of the tubes, as shown in FIGS. 2, 3 and 4. The corrugations are rectangular in cross section and the flat outer faces 98 of each panel 96 on an envelope abut the like flat face of the panel on the opposite side of the next adjacent tube.

Ribs, or air baflles, 100 are also brazed to each platelike element of the tubes along opposite sides thereof at -the upstream and downstream ends of the radiator to confine the cooling air to the finned area of the tubes. These completely enclose the ends of the plate-like envelopes as shown in FIG. 9 and abut the ribs of adjacent envelopes to form a complete closure at the upstream and downstream ends of the radiator matrix and to further support the envelopes against compression forces. The adjacent air baffles 100 of legs 52 and 54 abut along 'line 102 (FIG. 4), further supporting the radiator elements. The curvature of the flattened tubes and their corrugated panels 96 and ribs 100 is of involute form so that each element is of constant width and, when combined with the other elements, they completely fill the annular torusshaped space alloted to the radiator core.

Collapsing loads are carried by the fin panels, acting as transverse beams, to a number of bearing strips 104 (FIG. 5) running lengthwise of the radiator in the liquid passage of the flattened tubes. These bearing strips, which are H-shaped in cross section, are either loosely located by stops or are attached to one wall only by brazing so they cannot carry any tension loads between the sides of the tubes. Besides taking compression loads these strips also serve to distribute the liquid flow evenly over the entire area of the envelopes.

In the operation of the radiator, air discharged from the compressor section 14 flows through the transition section 26 from the annular compressor discharge passage 30 to the upstream end of passage 22. Since the annular barrier 92 closes off passage 20 between the radiator and casing 20, and since the air baflles 1&0 on the upstream ends of the radiator envelopes completely close 01f the frontal area of the torus-shaped radiator, the entering air is obliged to flow inwardly into annular passage 88 between the inner casing member 13 and the inner periphery of the radiator. This annular space 8% is also closed off at the downstream end of the radiator by the annular air seal 94. Consequently the air is obliged to flow from passage 88 between the envelopes 52 and 54 into the outer annular passage 90. Further, in its passage through the radiator, the air in passage 88 is distributed evenly over all of the envelopes in the torus-shaped radiator by reason of the corrugated panels 96. From the annular passage 90 the air heated by the radiator passes into transition section 28 and from thence into annular turbine inlet passage 40.

Liquid metal entering the radiator through conduit 86 enters the outer annular manifold 44 from which it is fed into the radiator through header tubes 82 which are arranged in staggered relation in two circular rows about the flat face 76 of manifold 44, a tube 82 from the outside row supplying the header of one envelope and a tube from the inside row supplying the header of the next envelope. The fluid in each of the headers 81 of the outer legs 54 of the U-shaped finned elements is distributed evenly over the envelope space by the bearing strips N4 which divide the envelope into a plurality of axial flow passages leading to the header 58 at the downstream end of leg 54. The liquid metal then flows through the header connector 60 into header 56 of the inner leg 52 of the U-tube. Here again the liquid metal is distributed over the surface of the envelope by bearing strips 104 as it flows axially forwardly through the envelope into headers 64, 64a, and 64b which are shown in FIGS. 6, 7 and 8. These headers are connected serially around the outlet manifold 42 into tube openings 72, 74 and 76 in the annular flattened face 70 of manifold 42. The arrangement of these tube openings is shown in FIG. 4 from which it will be evident that the finned-plate element of the first tube, beginning at the left of the figure, is connected to one of the tube openings 72. The tube 65 of the next element is connected to a tube opening 76 and the element 65 of the next tube is conneeted to atube opening 74 and so on about the manifold 42. In this way the tubes 65 can be of suflicient size to carry the flow from the envelopes while preserving the close spacing of the latter. From manifold 42 the liquid metal is discharged through outlet conduit 84. It will be noted that the inlet and outlet conduits 86 and 84 are shown herein only at the bottom of the radiator. However, if desired, such conduits may be provided at other points about the periphery of the manifolds.

From the above description it will be evident that a radiator has been provided herein consisting of a number of finned plate elements, identical except for header details, each of which is supported independently through inlet and outlet connections to circular manifolds. It Will also be evident that the elements are self-supporting with respect to collapsing pressures and that each is supported against bursting pressures by adjacent elements. Each element is independently free to expand longitudinally and transversely as required by thermal expansion and by pressure strain. Only one manifold, herein manifold 44, is fixed in the axial direction. The other is free to position itself according to differences in the length of the hot leg 54 and the cold leg 52 of the U-tube. Both manifold 42 and manifold 44 are allowed freedom of radial movement in all directions.

It will be understood that the same scheme can be used to produce rectangular radiators by assembling elements which are fiat rather than being formed to an involute curve. In such an arrangement the radiator air case must bear against the outer corrugations of the two end elements in order to provide support against bursting pressures.

While only one embodiment of the invention has been shown and described herein, which is particularly adapted to the air flow pattern of an axial flow gas turbine engine, it will be evident that variations may be made in the construction and arrangement of the parts for other adaptations without departing from the scope of the following claims.

I claim:

1. In a radiator for transferring heat from one fluid stream to another, elongated concentric cylindrical casing members defining a toroidal shaped chamber therebetween, a radiator matrix comprising a plurality of elongated U-shaped tubular elements the parallel legs of each of which are flattened and curved normal to their length to form hollow envelopes which lie in the same curved planes, said elements being arranged side-by-side in a circle about said toroidal chamber with their flat side surfaces in juxtaposition, inner and outer annular manifolds, one adjacent the inner casing member, the other adjacent the outer casing member, conduit means for connecting the inner legs of said U-shaped elements at their free ends to said inner manifold, conduit means for connecting the outer legs of said elements at their free ends to said outer manifold, means for fixedly supporting one of said manifolds against axial movement on the adjacent casing member While permitting limited radial movement relative to said casing member, and means for supporting the other manifold for free axial and lateral movement relative to said casing members.

2. The radiator of claim 1 having corrugated metal panels secured to the opposite sides of the envelopes with the corrugations running transverse to the longitudinal axes of said envelopes, said envelopes being closely spaced with the tops of the corrugations on adjacent envelopes in abutting relation, whereby said envelopes support one another against bursting pressures.

3. The radiator of claim 1 having means within the envelopes for resisting collapsing pressures, said means comprising bearing strips extending longitudinally of said envelopes in spaced relation over the area of said envelopes.

4. The radiator of claim 2 in which an annular space is provided between the inner casing member and the matrix and an annular space is provided between the outer casing member and the matrix, means for directing the incoming cold fluid into said inner space, and means for discharging the heated fluid from said outer space.

5. The radiator of claim 4 in which curved fluid baffles are secured to the opposite curved surfaces of each envelope at its axial extremities which engage the bafiies of adjacent envelopes and confine the fluid flow between said inner and outer spaces to the passages between said corrugations, the curvature of said envelopes being involute so that the envelopes with the baffles thereon present closed areas at the ends of the matrix.

6. The radiator of claim 5 in which the fluid bafiies are commensurate in height with the corrugations of said panels and engage the bafiies of adjacent envelopes to support the envelopes against bursting pressures.

7. In a liquid-metal-to-air radiator, an axially elongated casing having spaced cylindrical inner and outer casing members defining a toroidal chamber for the air flow, a plurality of U-shaped tubes extending axially from the upstream end to the downstream end of said chamber, said tubes being compressed to form hollow plate-like elements in the plane of the tube which are arranged in said chamber with the plane of the tube generally radially disposed in said chamber with the open ends of the tubes at the upstream end of said chamber, means for directing a stream of air into the upstream end of said chamber, means for discharging said air from the downstream end of said chamber, an inner circular manifold in the upstream end of said chamber adjacent said inner casing member, an outer circular manifold in the upstream end of said chamber adjacent said outer casing member, one of said manifolds being fixed to the adjacent casing member and the other being free to move relative to said casing, a header closing each of the free ends of each tube, a conduit connecting said inner manifold with the headers at the inner ends of said tubes, and a conduit connecting said outer manifold with the headers at the outer ends of said tubes.

8. In a liquid-metal-to-air radiator, an axially elongated casing having spaced cylindrical inner and outer casing members defining a toroidal chamber, a radiator matrix comprising a plurality of U-tubes forming the fluid passages of the radiator having each leg flattened and curved normal to its length, the legs at the closed end of the U terminating in headers, means for connecting said headers together, headers at the open ends of said U tubes, an inner circular manifold in said chamber adjacent the inner open ends of said U tubes, said manifold having an annular tube sheet confronting the headers of said inner open ends of said U tubes, header tubes connecting said inner headers with said tube sheet, an outer circular manifold in said chamber adjacent the outer open ends of said U tubes, said outer manifold having an annular tube sheet confronting the headers of said outer open ends of said U tubes, header tubes connecting said outer headers with said outer manifold, means for rigidly connecting one of said circular manifolds to a cylindrical casing member, fluid connections to said inner and outer manifolds, curved corrugated panels carried by said curved legs of said U tubes, said panels of each tube abutting panels of adjacent tubes, means for directing a stream of air into said chamber at its upstream end, air baflies for directing said air within the toroidal matrix of said radiator and into the spaces formed by the corrugations of said panels, and means for discharging said air at the downstream end of said chamber.

9. In a two-pass hot-liquid-to-air radiator, the combination of an elongated toroidal casing having a transition section at its upstream end receiving the discharge from a compressor and a transition section at its downstream end discharging into a gas turibne, outer and inner spaced concentric manifolds at the upstream end of said casing, said manifolds having liquid outlet and inlet connections and only one of said manifolds being fixedly supported by said casing at said upstream end against axial movement, inner and outer banks of hollow flat envelopes arranged in side-by-side relation about said toroidal casing and extending lengthwise of said casing, said envelopes in said inner and outer banks abutting each other and being closed at their abutting ends, said inner bank of envelopes having fluid connections with said inner manifold and said outer bank having fluid connections with said outer manifold, means for establishing fluid connections between said envelopes of said banks at their downstream ends, means for directing air entering said casing from the compressor into an annular passage in said casing within said inner bank of envelopes, and extended surface means between adjacent envelopes for directing said air over the surfaces of said envelopes.

It In a liquid-metal-to-air radiator, a core structure comprising a plurality of elongate U tube elements having each leg flattened and curved normal to its length to provide hollow plate-like envelopes, headers closing the ends of the envelopes at the closed ends of the tube elements, header connectors connecting the headers of each element, corrugated panels secured to opposite faces of said envelopes, the curvature of said envelopes being involute so that when said U shaped elements are arranged in side-by-side abutting relation they form a torus in which the elements provide mutual lateral support for each other against internal pressures, the spaces between the corrugations serving as passages for the air through the core and said envelopes serving as the liquid metal passages through the core.

11. In a liquid-to-metal-to-air radiator, a core structure comprising a plurality of elongate-d U tube elements having each leg flattened and curved normal to its length to provide hollow plate-like envelopes, headers closing the ends of the envelopes, header connectors connecting the headers at the closed ends of the U tube elements, curved corrugated panels secured to the opposite faces of said envelopes, the curvature of said envelopes and their panels being involute so that when said elements are arranged in side-by-side relation they form a solid torus in which the elements provide mutual lateral support for each other against internal pressures, inner and outer circular manifolds at the unconnected ends of said legs, tubes connecting the header of the inner leg of each element to said inner manifold, tubes connecting the header of the outer leg of each element to said outer manifold, liquid metal inlet and outlet connections to said manifolds, and means for directing a stream of air to flow through the spaces formed by the corrugations of said abutting panels.

12. A liquid-metal-to-air radiator comprising, a plurality of elongated U tubes forming the liquid passages for the radiator, said tubes having each leg flattened and curved normal to its length, pairs of curved ribs brazed to opposite sides of each leg at its ends forming air baffles, corrugated curved panels brazed to opposite sides of said legs and extending between said ribs, the curvatures of said legs being involute so that when arranged in side-byside relation said tubes form a continuous solid matrix of toroidal shape, inner and outer cylinders forming an elongated torus-shaped chamber for said matrix, inner and outer circular manifolds located at the open ends of said U tubes, tubes connecting said inner manifold to the headers of corresponding inner legs of said U tubes, tubes connecting said outer manifold to the headers of corresponding outer legs of said U tubes, liquid metal inlet and outlet connections for said manifolds respectively, means for directing a stream of air into the upstream end of said chamber, means for discharging said air stream downstream of said chamber through the passages formed by the corrugations on said panels first across one leg of said U tubes then the other, and baflle means in said chamber for directing air to flow generally radially across said envelopes means for fixedly supporting one of said manifolds against axial movement on an adjacent cylinder, and means for supporting the other manifold on an adjacent cylinder for freedom of movement both axially and laterally.

References Cited by the Examiner UNITED STATES PATENTS 1,830,375 11/1931 Shoop 165164 2,053,780 9/1936 Price et a1. 16581 2,409,801 10/1946 Ruegg l26109 2,444,908 7/1948 Bailey et al. l172 X 2,582,134 1/1952 Kimmell et al 81 X 3,033,534 5/1962 Caughill et al. 165-82 FOREIGN PATENTS 501,849 3/1939 Great Britain.

FREDERICK L. MATTESON, JR., Primary Examiner.

SAMUEL FEINBERG, Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,224 502 December 21, 1965 Rudolf N. Wallace It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, line 56, column 5, line 11, column 6, lines 11, 58 and 74, and column 7, line 19, for "length", each occurrence, read width Signed and sealed this 31st day of January 1967.

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents

Claims (1)

1. IN A RADIATOR FOR TRANSFERRING HEAT FROM ONE FLUID STREAM TO ANOTHER, ELONGATED CONCENTRIC CYLINDRICAL CASING MEMBERS DEFINING A TOROIDAL SHAPED CHAMBER THEREBETWEEN, A RADIATOR MATRIX COMPRISING A PLURALITY OF ELONGATED U-SHAPED TUBULAR ELEMENTS THE PARALLEL LEGS OF EACH OF WHICH ARE FLATTENED AND CURVED NORMAL TO THEIR LENGTH TO FORM HOLLOW ENVELOPES WHICH LIE IN THE SAME CURVED PLANES, SAID ELEMNETS BEING ARRANGED SIDE-BY-SIDE IN A CIRCLE ABOUT SAID TOROIDAL CHAMBER WITH THEIR FLAT SIDE SURFACES IN JUXTAPOSITION, INNER AND OUTER ANNULAR MANIFOLDS, ONE ADJACENT THE INNER CASING MEMBER, THE OTHER ADJACENT THE OUTER CASING MEMBER, CONDUIT MEANS FOR CONNECTING THE INNER LEGS OF SAID U-SHAPED ELEMENTS AT THEIR FREE ENDS TO SAID INNER MANIFOLD, CONDUIT MEANS FOR CONNECTING THE OUTER LEGS OF SAID ELEMENTS AT THEIR FREE

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