US3785435A

US3785435A - Thermal damper for plate type heat exchangers

Info

Publication number: US3785435A
Application number: US00306968A
Authority: US
Inventors: W Stein; S Straniti
Original assignee: Avco Corp
Current assignee: Avco Corp
Priority date: 1972-11-15
Filing date: 1972-11-15
Publication date: 1974-01-15
Anticipated expiration: 1991-01-15
Also published as: DE2342174B2; FR2206488B1; JPS4981948A; IT996410B; DE2342174C3; DE2342174A1; SE414828B; FR2206488A1; JPS5215817B2; GB1419839A

Abstract

A heat exchanger is described which is particularly adapted for use with a regenerative type gas turbine engine. The heat exchanger comprises a series of annular discs which define a central flow path for the hot gas discharge of the engine. Adjacent plates define radial flow paths for the hot gas discharge which alternate with cross flow paths between plenums which are respectively connected to the engine''s compressor and combustor thereby increasing the energy level of the hot gas stream generated in the combustor. This stack of plates is connected to a frame member of relatively large mass through a series of thermal damper discs which are alternately connected, by seam welding, peripherally around their inner and outer diameters and then peripherally around openings which define the plenum passageways for the flow of air from the compressor and back to the combustor.

Description

Stein et al.

[ THERMAL DAMPER FOR PLATE TYPE Primary Examiner-Charles J. Myhre HEAT EXCHANGERS Assistant Examiner-Theophil W. Streule, Jr. [75] Inventors: Wolfgang J. Stein, Milford; Attorneyncharles Hogan et gzgzfitore Stu-amt], Orange, both of 57] ABSTRACT h A heat exchanger is described which is particularly Asslgnee? Avco Corpqratwn, Stratford, Connadapted for use with a regenerative type gas turbine [22] Filed: No 15 1972 engine. The heat exchanger comprises a series of annular discs WhlCh define a central flow path for the hot PP 306,968 gas discharge of the engine. Adjacent plates define radial flow paths for the hot gas discharge which alter- 52 U.S. c1 165/76, 165/80, 165/166 i cmss PathS Plan"ms which are [51] Int. Cl F28f 7/00 respectwely connected to the engmes compressor and [58] Field of Search .L 165/164-167, 157, 170 cmbustr hereby iwetsing the energy level. the hot gas stream generated in the combustor. ThlS stack of plates is connected to a frame member of relatively [56] References Cited lalrlgehmass ltthroughl a series totgjtllijermal damlpjer discs w 1c are a erna e y connec e y seam we mg, pe- UNITED STATES PATENTS ripherally around their inner and outer diameters and 3,228,465 l/19 66 Vadot 165/167 then peripherally around openings which fi the 12:23 et plenum passageways for the flow of air from the com- 3:603:38] 9 1971 scherbaiiiii 1:............:::Ill:.. 165 80 Press and back to the combusm 8 Claims, 4 Drawing Figures Al ll 1 I III II l lllll Ill llj R FROM COMPRESSOR lllllllillllllllll ll 27 26 HOT GAS f m a DISCHARGE P I 1111 11111 1111111\|11-||| AIR TO COMBUSTOR 22 Y L l I l I II II I l l EXHAUST 1 [FEED I II II l llH II I II MF S SOR 20 Hl! lllll llll I" PAIENIEUJAN I W 3.785.435

ExFiAusT 24 PAIENTEUJAM I 5 I974 SHEET 2 BF 3 EDIE The present invention relates to heat exchangers and more particularly to improvements in mounting plate type heat exchangers.

A particularly effective type of heat exchanger,

adapted for a regenerative type gas turbine engine, is

disclosed in US. Pat. No. 3,424,240. In that heat exchanger, a stack of corrugated annular discs defines a central entrance passageway for the hot gas discharge of the engine. The hot gasses pass radially between alternate pairs of discs to a discharge duct. Compressor air enters longitudinally extending plenums and then passes through cross flow paths between other alternate discs to exit plenums connecting with the engines combustor. The discs are corrugated to facilitate the exchange of heat from the hot gas stream to the compressor air passing through the heat exchanger. In the regenerative type engine, the waste heat energy of the engine is transferred to the pressurized air in transit between the compressor and combustor of the engine. Transfer of heat in this fashion increases the theoretical efficiency of the engine.

A problem of particular significance is found in mounting such a heat exchanger. The heat exchanger is disposed downstream of the last turbine stage of the engine and must be secured in some fashion to the engine itself. Thus, the thin disc of the heat exchanger, in some fashion, must be secured to a relatively massive frame element which will surround the discharge flow path of the engine and usually include passageways connecting the plenums of the heat exchanger at the compressor and the combustor of the engine.

The thin corrugated discs of the heat exchanger are secured together be welding or the like in bellows fashion. Such discs being alternately joined at the inner and outer peripheries and peripherally of openings which define the referenced plenums. These thin discs have a high rate of. thermal growth,-as compared to the frame member to which they must be joined. During thermal transients a problem arises after repeated thermal cycles, as encountered in normal engine operation, of a failure at or adjacent the juncture between the discs and the frame. Such a failure can then lead to, leakage between the separate flow paths for the hot gas discharge and the pressurized air. Such leakage can lead to losses in engine efficiency or even engine failure.

Accordingly, the object of the invention is to provide an improved connection between relatively thin, flow path defining discs, or plates, of a heat exchanger and a mounting frame therefor and more specifically to devise such an improved mounting for heat exchanger discs having an annular configuration.

The above ends, in accordance with the broader aspects of the invention, are attained by a heat exchanger comprising aseries of relatively thin plates which define alternate flow paths for different fluids between which heat energy is to be exchanged. This series of plates is connected to a frame of relatively large mass and low rate of thermal growth through a thermal damper comprising a series of thermal damper plates which are successively connected to each other with the connection to each thermal damper plate, on opposite sides thereof, being laterally spaced.

Further, it is advantageous that the thermal damper plates have their opposite adjacent surfaces in substantially contiguous relationship and also that the thermal damper plates adjacent the frame have a greater thickness than those adjacent the heat exchanger plates.

In a configuration particularly adapted for use with a regenerative type engine, the heat exchanger plates and the thermal damper plates are in the form of annular discs defining a central passageway for one of the fluids which would be the hot gas discharge of the engine. Further, the heat exchanger discs and the thermal damper discs have inlet and outlet plenum passageways extending therethrough which are defined by openings therein. The alternate flowpaths between the heat exchanger plates comprise cross flow paths between said plenums and radial flow paths communicating with said central passageway. In this case, each of the thermal damper discs within the series thereof, is joined on one surface to the adjacent discby seam welding peripherally of both its inner and outer diameters and is joined on its opposite surface to the adjacent disc by seam welding peripherally of the plenum defining openings.

Further, it is advantageous that the adjacent surfaces of the thermal damper plates are disposed in substantially contiguous relationship to prevent a flow of fluid between the surfaces thereof. Also it is preferable that the thermal damper plates adjacent the frame have a thickness greater than those adjacent the heat exchanger plates.

In a more specific sense, the frame would have a conical annular seat throughwhich the plenum opening passageways thereof extend. The thermal damper plates would comprise a part of a thermal damper assembly which includes an annular mounting disc having a seat sealingly engaging the frame seat and also having corresponding plenum passageways or openings therethrough. A thermal damper plate of intermediate thickness, in substantially contiguous relationship with the mounting disc is joined thereto by seam welding peripherally of the passageway openings thereof, successive thermal damper plates are then joined to the intermediate plate, first by seam welding around the inner and outer peripheries thereof and then alternately by seam welding peripherally of the plenum defining openings and the inner and outer diameters. Further, a heat exchanger disc is joined to the last of the thermal discs by seam welding peripherally of the inner and outer diameters thereof. This assembly is completed by a support disc joined to the last of the heat exchanger discs by seam welding peripherally of the inner and outer diameters thereof. The heat exchanger is completed by a series of heat exchanger discs in sub-stacks defined at their opposite ends by support discs. This heat exchanger is then held in assembledrelation by tie rods means which exert an axial loading on the stack of discs relative to the frame and compress same to bring the thermal damper discs or the surfaces thereof into contiguous relationship.

Another aspect of the invention is found in a thermal mounting assembly for use in a heat exchanger as referenced above. This assembly comprises a plurality of thermal damper discs having plenum passageway openings therethrough. The discs are joined together in pairs by seam welding peripherally of the openings therethrough. These pairs are divergently flared toward their inner and outer diameters which in turn are joined peripherally thereof to adjacent pairs. By forming the thermal damper in this fashion, the welding of the component parts thereof is facilitated. Further, the assembly described is characterized by the fact that when subjected to an axial loading, the adjacent surfaces of the thermal damper plates can be brought into contiguous relationship without any undue stresses being induced therein.

The above and other related objects and features of the invention will be apparent from a reading of the following description of a preferred embodiment thereof, with reference to the accompanying drawings, and the novelty of the invention will be apparent from a reading of the appended claims.

In the drawings:

FIG. 1 is a longitudinal cross section of a heat exchanger in which the present invention is embodied;

FIG. 2 is a perspective view, partially exploded, of a stack of plates comprising the present heat exchanger;

FIG. 3 is a fragmentary perspective view, on a greatly enlarged scale, of a thermal damper assembly for the discs of the heat exchanger prior to installation in the heat exchanger; and

FIG. 4 is an enlarged longitudinal section of the thermal damper assembly of FIG. 3 after installation in the heat exchanger.

The heat exchanger illustrated in FIG. 1 and indicated by reference character 10, is adapted for attachment to a gas turbine engine at a point downstream of its last turbine stage. The engine itself may be of conventional construction inaccordance with well known designs for a regenerative type engine. The hot gas discharge of the engine enters the center of the heat exchanger and then is directed radially outwardly, through a stack of plates, or discs, 1 1, to an exhaust system which includes a surrounding duct 12. The heat exchanger 10 comprises an adaptor frame 14 which may be attached to the load carrying structure of the engine.

The adaptor frame 14 has a plurality of passageways l6 and 18 which respectively connect with engine passageways (not shown) leading'from the engine compressor and leading to the engines combustor. The compressor passageways 16 are aligned with a plurality of inlet plenums 20, see also FIG. 2, formed longitudinally through the stack of discs 11. The combustor passageways 18 are aligned with a plurality of exit plenums 22 also extending longitudinally through the stack of discs 11. Radial flow paths for the hot gas discharge and cross flow paths, between adjacent plenums and 22, for the compressor air provide the primary area of heat exchange. These flows are indicated in FIG. 2.

The heat exchanger 10 also comprises an end frame 24 and an end disc 26 which define the downstream limit of the hot gas discharge flow path so that all of the hot gasses may be turned radially outwardly through the stack of discs 11 and discharged to the duct 12. The

frame

14 and 16 are connected by tie rods 27 to hold the heat exchanger in assembled relation.

The heat exchanger discs 11 have flanges peripherally of their inner and outer diameters which alternately project in opposite axial directions so that the discs are disposed in pairs joined at their matching flanges. The discs also have openings which respectively define the

plenums

20 and 22. The pairs of discs joined at their flanges are then joined with the next adjacent discs by seam welding or the like, peripherally of the plenum defining openings thus forming a bellows type of construction which defines the referenced flow paths for the radially flowing hot gas discharge and the cross flow of air from the inlet plenums to the exit plenums. These discs are also corrugated, as in the above referenced patent, for increased heat transfer as well as to prove structural strength when the stack of discs is subjected to axial loading through the tie rods 28.

The stack of discs 11 may be formed as a series of sub-stacks as taught in U. S. Pat. No. 3,385,353 thus a plurality of discs 11 may be secured to somewhat thicker support discs 32 which also have corresponding plenums defining openings. The support discs 32 are slotted around the peripheries to receive rods 28 which extend between the frames 13 and 24.

The stack of discs 11, or series of sub-stacks thereof, connect with the frame 14 through a thermal damper assembly 34 comprising in series relationship (FIG. 4), a mounting disc 36, an intermediate thickness disc 38, a plurality of thermal damper discs 40, a pair of heat exchange discs 11, and a support disc 32. The

discs

36, 38 and 40 also have openings corresponding to and aligned with the openings in discs 11, to further define the

plenums

20 and 22.

FIG. 3 illustrates the thermal damper assembly 34 prior to its incorporation in the heat exchanger. The mounting disc 36 is flanged peripherally of its inner and outer diameters to form a seat for sealingly engaging a correspondingly shaped, annular seat on the frame 14. The disc 36 is joined to the somewhat thinner, intermediate thickness thermal damper disc 38 by seam welding peripherally of the openings defining the

plenums

20 and 22. Successive pairs of the thinner thermal damper discs 40 are also joined by seam welding peripherally of their plenum defining openings. Each pair of discs so joined at their openings is joined to the adjacent disc pair by seam welding peripherally of their inner and outer diameters. The inner and outer diameters of the disc pairs,joined at their openings, are divergently flared to facilitate seam welding of the inner and outer diameters of adjacent pairs. The pair of discs 11 are also joined by seam welding peripherally of their plenum defining openings and have divergent flanges to facilitate seam welding of their respective inner and outer diameters to the last thermal damper disc 40 and the support disc 32.

When this assembly is incorporated in the heat exchanger, the discs 42 are flattened by the compressive forces exerted through the tie rods 28. The flared thermal damper discs are sufficiently'thin that they are not unduly stressed when so flattened. The thermal damper discs thus have their opposite surfaces in contacting or substantially contiguous relation so that there is no gas or air flow therebetween.

It will be apparent that when engine operation is initiated and all components of the heat exchangers are at essentially the same temperature, the heat exchange discs 11 will quickly increase in temperature and will be subject to a relatively rapid thermal growth. This is particularly reflected in the-discs ll of the mounting assembly. The disc 11 and the last thermal damper disc defines a relatively cool, air cross flow path, opposite which is radial flow path for the hot gas discharge. The thermal growth of this disc 11 is then transferred through the succession of thermal damper discs 40 which provide respective increments of thermal growth as the heat transfers, or flows therebetween. More specifically, since opposite sides of the thermal damper discs are joined to adjacent discs by connections which are laterally offset, i.e., between the inner and outer diameters and the plenum openings, an elongated heat flow path is created, there bieng a relatively low heat transfer between contiguous discs. This results in progressive thermal growth of thethermal damper plates so that growth differentials between successive plates is relatively small and also small between the thermal damper plate adjacent the frame M which is of large mass and heat sink with a relatively slow thermal growth. This effect is further enhanced by forming the intermediate disc 40 and the mounting disc 33 of progressively greater thickness. The net effect of the de scribed thermal damper assembly is to greatly minimize induced stresses between adjacent discs which tend to rupture the joints therebetween. This all combines to provide an economical mounting of the heat exchanger which minimizes the possibilities of failure and greatly prolongs its service life.

While a preferred embodiment of the invention has been described, modifications thereof will be apparent to those skilled in the art within the broader aspects of the invention. Thus, for example, in the broader aspects of the invention, the thermal damper plates may not be incorporated in a separate assembly or may be joined by other welding procedures such as brazing or the discs may take other plate form. The spirit and scope of the invention is therefore to be derived from the following claims.

Having thus described the invention, what is claimed is novel and desired to be secured by letters of patent of the United States is:

l. A heat exchanger comprising a series of relatively thin heat exchange plates which define alternate flow paths for different fluids between which heat energy is to be exchanged,

a frame of relatively large mass and low rate of thermal growth,

a thermal mounting interposed between said frame and series of heat exchange plates, said mounting including a series of successively connected, thermal damper plates with the connections between each thermal damper plate within the series thereof being laterally spaced on opposite sides thereof.

2. A heat exchanger as in claim 1 wherein said thermal damper plates are disposed with their adjacent surfaces in substantially contiguous relation.

3. A heat exchanger as in claim 2 wherein thermal damper plates adjacent the frame have a thickness greater than the thermal damper plates adjacent said heat exchanger plates.

4. A heat exchanger as in claim ll wherein the heat exchanger plates and the thermal damper plates are annular discs and define a central passageway for one of said fluids,

the frame, the heat exchanger discs, and the thermal damper discs have inlet and outlet plenum passageways extending therethrough, defined by openings therethrough, and the alternate flow paths, between said heat exchange discs, comprise cross flow paths between said plenums and radial flow paths communicating with said central passageway and further wherein each thermal damper disc, within the series thereof, is joined on one surface to the adjacent disc by seam welding peripherally of both its inner and outer diameters and is joined on its opposite surface to the adjacent disc be seam welding peripherally of said plenum defining openings.

5. A heat exchanger as in claim 4 wherein the adjacent surfaces of said thermal damper discs are disposed in substantially contiguous relationship thereby preventing a flow of fluid between the surfaces thereof.

6. A heat exchanger as in clain 5 wherein the thermal damper discs adjacent the frame are thicker than those adjacent the heat exchanger plates.

7. A heat exchanger as in claim 6 wherein the frame has a conical annular seat through which said plenum passageways extend,

the thermal mounting is in the form of an assembly comprising, in series relationship,

an annular mounting disc having a correspondingly formed seat for sealingly engaging said frame seat and also having corresponding plenum passageways therethrough,

an intermediate thickness, thermal damper disc in substantially contiguous relationship therewith and joined thereto by seam welding peripherally of the openings thereof,

a first, thin thermal damper disc joined to the intermediate disc by seam welding peripherally of the inner and outer diameters thereof,

a plurality of thinner thermal damper discs,

a plurality of heat exchange discs, the first of which is joined to the adjacent thermal damper disc by seam welding peripherally of their inner and outer diameters, and a support disc joined to the last heat exchanger plate by seam welding peripherally of the inner and outer diameters thereof,

further heat exchange discs arranged in sub-stacks bounded by end plates and means holding said assembly in compressed relation.

8. A thermal mounting assembly comprising a plurality of annular, thermal damper discs having aligned passageway openings therethrough and spaced around the central opening thereof,

said discs being disposed in series stacked relation,

successive pairs of discs being joined by seam welding around said openings with their inner and outer diameters being divergently flared and adjacent pairs of discs being joined by seam welding around their inner and outer diameters, the divergence of the diameters facilitating the welding thereof said stack of discs being further characterized by the thinness of the discs permitting their flattening into substantially contiguous surface relation, without undue deflective when the stesses, stack is subject

Claims

1. A heat exchanger comprising a series of relatively thin heat exchange plates which define alternate flow paths for different fluids between which heat energy is to be exchanged, a frame of relatively large mass and low rate of thermal growth, a thermal mounting interposed between said frame and series of heat exchange plates, said mounting including a series of successively connected, thermal damper plates with the connections between each thermal damper plate within the series thereof being laterally spaced on opposite sides thereof.

4. A heat exchanger as in claim 1 wherein the heat exchanger plates and the thermal damper plates are annular discs and define a central passageway for one of said fluids, the frame, the heat exchanger discs, and the thermal damper discs have inlet and outlet plenum passageways extending therethrough, defined by openings therethrough, and the alternate flow paths, between said heat exchange discs, comprise cross flow paths between said plenums and radial flow paths communicating with said central passageway and further wherein each thermal damper disc, within the series thereof, is joined on one surface to the adjacent disc by seam welding peripherally of both its inner and outer diameters and is joined on its opposite surface to the adjacent disc be seam welding peripherally of said plenum defining openings.

7. A heat exchanger as in claim 6 wherein the frame has a conical annular seat through which said plenum passageways extend, the thermal mounting is in the form of an assembly comprising, in series relationship, an annular mounting disc having a correspondingly formed seat for sealingly engaging said frame seat and also having corresponding plenum passageways therethrough, an intermediate thickness, thermal damper disc in substantially contiguous relationship therewith and joined thereto by seam welding peripherally of the openings thereof, a first, thin thermal damper disc joined to the intermediate disc by seam welding peripherally of the inner and outer diameters thereof, a plurality of thinner thermal damper discs, a plurality of heat exchange discs, the first of which is joined to the adjacent thermal damper disc by seam welding peripherally of their inner and outer diameters, and a support disc joined to the last heat exchanger plate by seam welding peripherally of the Inner and outer diameters thereof, further heat exchange discs arranged in sub-stacks bounded by end plates and means holding said assembly in compressed relation.

8. A thermal mounting assembly comprising a plurality of annular, thermal damper discs having aligned passageway openings therethrough and spaced around the central opening thereof, said discs being disposed in series stacked relation, successive pairs of discs being joined by seam welding around said openings with their inner and outer diameters being divergently flared and adjacent pairs of discs being joined by seam welding around their inner and outer diameters, the divergence of the diameters facilitating the welding thereof said stack of discs being further characterized by the thinness of the discs permitting their flattening into substantially contiguous surface relation, without undue deflective when the stesses, stack is subject to an axial loading.