US3473210A

US3473210A - Method of making a heat exchanger

Info

Publication number: US3473210A
Application number: US640760A
Authority: US
Inventors: Walter C Klank
Original assignee: United Aircraft Products Inc
Current assignee: United Aircraft Products Inc
Priority date: 1967-01-19
Filing date: 1967-01-19
Publication date: 1969-10-21
Anticipated expiration: 1986-10-21

Description

Oct. 21, 1969 w. c. KLANK 3,473,210

METHOD OF MAKING A HEAT EXCHANGER Original Filed June 2, 1965 2 Sheets-Sheet l INVENTOR.

Oct. 21, 1969 w. c. KLANK 3,473,210

METHOD OF MAKING A HEAT EXCHANGER Original Filed June 2, 1965 2 Sheets-Sheet z INVENTOR. W517i? C. KAfl/VK BY His 0770/24 55 United States Patent US. Cl. 29-1573 3 Claims ABSTRACT OF THE DISCLOSURE This disclosure relates to method of assembling a heat exchanger which is largely self fixturing in its construction. The method requires the use of a fixture having a bottom plate with spaced upright posts extending therefrom. Plate elements and fin elements having openings aligned with the posts are stacked in alternating order, the posts extending through the openings. Inlet and outlet bosses are slid over the posts at the top and bottom of the assembly. The assembled structure is permanently united while being firmly held in the fixture. The fabricated heat exchanger is then removed from the fixture.

This application is a division of Ser. No. 460,715, filed June 2, 1965, now abandoned.

This invention relates to heat exchangers and to methods of making thereof, the invention having particular regard to new concepts in the making of low cost plate and fin heat exchangers.

An object of the invention is to provide a generally new plate and fin heat exchanger which uses but few parts and which lends itself to simplified assemblies.

Another object of the invention is to introduce a method of manufacture permitting rapid assembly of the parts of a heat exchanger by unskilled operators and in a manner to obviate process steps of the prior art.

A further object of the invention is to provide a heat exchanger which is largely self fixturing in its construction and which eliminates manifolding requirements.

Other objects and structural details of the invention will appear from the following description, when read in connection with the accompanying drawings, wherein:

FIG. 1 is a view in side elevation of a plate and fin heat exchanger in accordance with the illustrated embodiment of the invention, a portion of the device being broken away to show flow passages therein;

FIG. 2 is a top plan view of the device of FIG. 1;

FIG. 3 is a fragmentary view in cross-section, taken substantially along the line 3-3 of FIG. 1;

FIG. 4 is a view in exploded isometric showing the heat exchanger device of FIGS. l-3 in a stage of manufacture, the parts being shown in conjunction with fixturing apparatus; and

FIG. 5 is a fragmentary top plan view of a plate element.

Referring to the drawings, a heat exchanger in accordance with the invention is comprised of a plurality of plate elements between certain of which is interposed a fin element 11 and between certain others of which is disposed a fin element 12 (FIG. 3). In the illustrated instance the several plate elements 10 are identical. Thus, and referring also to FIG. 4, each is a flat thin metal sheet which in a press or the like is formed to have on one side thereof a recess 13, formed over nearly the entire surface of the plate. The result is to form peripherally of the plate element a relatively raised marginal edge or flange 14. The plate element 10 is rectangular in shape and may be formed at either end with two spaced series of extrusions 15 projecting into the recessed area 13. Be-

tween the series of extrusions 15 at each end the plate is deformed to provide on the recessed side thereof a circular depression 16, and, on the opposite side a circular proturbance 17. The bottom of the depression or protuberance so formed is flat and there is thus provided with respect to the described opposite side of the plate a relatively projected surface 18 approximately parallel to the plate proper. Coaxial of each depression-protuberance 16-17, in the surface 18, is a through opening 19.

The fin elements are provided in two forms. In one form, represented by the fin 11, thin, ductile sheet metal material is crimped or gathered to an undulating formation to present a plurality of parallel peaks and valleys, the peaks being in the case of fin elements 11, relatively tall. The fin elements 11 are rectangular in shape and conform generally to the dimensions of the plates 10. Near the ends of each fin element are through openings 22. The openings 22 are in the same relative positions in the fin elements 11 as are the depressions 16 in the plate elements 10 and are sized to receive the protuberances 17 in a substantially nested relation. The other fin elements 12 are like the fin elements 11 but are shorter in length and the individual fins thereof are shorter in height than in the case of elements 11. The fin elements 12 have no openings therein. Their length is such as approximately to equal or to be slightly less than the distance between the series of extrusions 15 at opposite ends of each plate element 10.

In the assembly of a heat exchanger a plate element 10 may serve as the bottom end plate and is placed with its recessed side facing downwardly or outwardly. On top of such bottom plate is placed a fin element 11, the openings 22 therein fitting over the upwardly facing protuberances 17 on the plate element. This is followed by another plate element 10 turned in inverse relation to the first so that the proturbances 17 of the second plate element are in a facing relation to the corresponding protuberances on the bottom plate element. The two sets of protuberances extend through the openings 22 of the interposed fin element 11 and achieve a contacting relationship to one another along the surfaces 18, as indicated in FIG. 1. The openings 19 in the plate elements are thus aligned and form with the abutting protuberances a through longitudinal passage. The uppermost of the described pair of plate elements 10 has its side forming recess 13 facing upwardly 0r outwardly. In superposed relation to this plate element is placed another like plate element and in a relatively inverted relation. This arrangement puts the raised marginal edges 14 of the mating plate elements in a contacting relation and forms by virtue of the opposing recesses 13 a chamber 24 (FIG. 3). A fin element 12 is received within the chamber 24 and the depth of the recess 13 is so determined, in relation to the height of fin element 12 as to place the bottoms of the respective facing recesses 13 in contact with the peaks and valleys of the interposed fin element 23. Placed on top of the mating plate elements 10 is another fin element 11 and this is followed by another, relatively inverted, plate element 10, with the several plate and fin elements being stacked in the described order until an amount of heat transfer surface is provided calculated to produce heat transfer in accordance with specification requirements.

The fin elements 11 and 12 are, as noted, arranged at right angles to one another in respect to the longitudinal direction of their respective fins. Thus, the fin element 12 is placed in a recess 13 in such manner that fluid flowing longitudinally through the recess, or through chamber 24, from one opening 19 to another may pass freely through and over the fin element. The fin element 11 is placed at right angles to the fin element 12 so that a fluid flowing between a pair of plates separated by the fin element 11 in a direction transversely of the direction of fluid flow between openings 19 will flow longitudinally through and over the fin element 11. The result is a heat exchanger of the cross-flow type. Fluids of different temperature, flowing over the respective fin elements, undergo a temperature change as the warmer fluid yields up some of its heat to the fin element with which it is in contact, with such heat being then conducted through an interposed plate element to be absorbed into the fluid of lower temperature on the opposite side thereof. The fin elements provide secondary heat transfer surface while the plate elements 10, being directly in contact with the separated fluids, present primary heat transfer surface.

Further in accordance with the illustrated embodiment of the invention the end plate elements have their recessed sides 13 facing outwardly. Located in each depression 16 in such outwardly facing side is a boss 25. Each boss 25 is a short length cylindrical member having a through bore 26 therein which bore may be threaded to facilitate connecting of the heat exchanger in fluid flowing systems.

The diameter of the bore 26 corresponds approximately to the diameter of the openings 19 in the plate elements 10. Further, the external diameter of the boss 25 is such as to cause it to fit relatively closely in the depression 16. The result is to align bore 26 with the series of openings 19 and to make of such bore a continuation of the passage defined by the several openings 19 and the mating protuberances 17 of the plate elements 10.

The bosses 25 provide for the inlet and outlet of a fluid. According to one mode of use thereof the bosses 25 at the bottom of the heat exchanger are closed, as by the installation of threaded plugs therein. One of the top bosses is used as the inlet and the other as the outlet. Fluid under pressure admitted to the inlet boss 25 flows downward through the aligned openings 19 and fills the vertical passage defined thereby. This passage, as indicated and described, intersects the transverse chambers 24 at each level thereof. Accordingly the mentioned fluid has access to the chambers 24 at one end thereof. It flows longitudinally through each chamber over and around the fin element 12 disposed therein until it reaches the corresponding vertical passage at the opposite end of the heat exchanger. There it rises through a communicating opening 19 and moves through the vertical passage to the outlet boss 25. In the illustrated instance the heat exchanger functions to extract heat from a heated liquid. The liquid is supplied to the inlet boss 25 and flows through the described circuit represented essentially by the chambers 24 and fin elements 12. Air, serving as the coolant, is blown or drawn through the heat exchanger in a cross-flow relation to the movement of the liquid through the chambers 24 and hence flows over and around the fin elements 11 with the efiect heretofore described.

The device of the invention accordingly is characterized by simplicity of construction wherein a single, simple plate element is repeatedly used as a tube sheet. In accordance with further inventive concepts, however, the device is constructed to be in large part self-fixturing and to be easily assembled and otherwise prepared for the brazing operation by which the parts are joined together. Thus fixturing means is provided in the form of a bottom or base member 27 and a top pressure member 28. The

members

27 and 28 are made of a nonbrazing material different from the material of

elements

10, 11 and 12. While they may assume any convenient configuration they are in the illustrated instance rectangular in correspondence with the plate elements 10 but with dimensions somewhat exceeding those of the plate elements. The upwardly facing side of base member 27 is formed with longitudinally spaced apart recesses 29 from the center of each of which projects an upstanding post 31. The posts 31 are rigidly set in the base 27 and have a height substantially to exceed the height of a heat exchanger device to be assembled. The recesses 29 are greater in diameter than are the posts 31, being of a size rather closely to receive the bosses 25. The diameter of the posts 31 is somewhat less than but close to the diameter of the bores 26 in the bosses 25 and of the plate openings 19. The top or pressure member 28 has on the underside thereof recesses 32 corresponding in size and location to the recesses 29 in base 27. Concentric openings 33 allow for passage of the posts 31 therethrough.

In making use of the fixturing means the parts are stacked in order on the base member 27, fitting over the posts 31. Thus, as a first step, bosses 25 are slipped over the posts 31 and come to rest in the recesses 29 in base member 27. This is followed by a plate member 10 which comes to rest with its depressions 16 interfitting with the upper outer ends of the bosses 25. Remaining elements of the heat exchanger assembly are stacked in this manner, and in the order before described, until the required heat transfer surface has been provided. Then the top bosses 25 are slipped over the posts 31, coming to rest in the depressions 16 in the top most plate element 10. Now the top pressure member 28 is mounted on the posts 31, the latter projecting through the openings 33 therein in such a manner as to make the member 28 a free floating part. The member 28 is made of heavy material or otherwise weighted in such wise as to exert a downward pressure upon the heat exchanger elements, urging adjacent parts into contact with one another and seating the assembly firmly on the base 27. As a result of this there is a close uniform contact between the raised edges 14 of mating plate elements 10 and close continuous contact between the peaks and valleys of the fin elements 11 and 12 and the plate surfaces engaged thereby. As a consequence, in an ensuing brazing operation, long, continuous joints are achieved insuring strength and resistance to separation from internal fluid pressure, vibration or like causes. The extrusions of mating plate elements limit applied compression, maintaining flow paths through chambers 24.

The brazing process may be one of a known kind, as for example one in which the assembled device is dipped in molten flux. In this instance the bosses 25 provide access for the molten flux during the brazing operation and provide also a means whereby the molten flux may readily be drained and flushed from the interior of the device after brazing. The lower bosses 25 serve, in this connection, as alternate inlet and outlet openings, and, also, as access and drainage holes. In the latter regard they obviate the use of the usual drainage holes which must be later plug Welded shut.

The construction lends itself, however, also to furnace brazing performed in the usual manner or under vacuum conditions. The parts of the device are, as noted, substantially self-fixturing by reason of their manner of interengagement with one another and with the fixturing means. The top pressure plate 28 of the fixture serves as a free floating member of suflicient weight to provide the necessary braze contact of the heat exchanger elements but not requiring elaborate clamping or bolting arrangements. Thus when a device has been assembled and fixtured in the manner shown in FIG. 4 hereof it may simply be placed in a brazing furnace, with the fixturing members being detached from the assembly after the brazing is completed.

A device may be completely assembled and prepared for brazing without the need of special skills. The mounting posts 31 and their relationship to the parts of the heat exchanger, taken with the uniformity of and small number of different parts, obviates the need for exercising anything other than a sense of touch in completely assembling and preparing a heat exchanger device. The fixture on which the parts are stacked serves also as the brazing fixture.

In another aspect thereof, the invention avoids the need for outside manifolding. The liquid for flow through the chambers 24 is brought directly to the core of the heat exchanger by way of the bosses 25 and similarly is carried away from the core. The attaching of duct work or flow conduits to the heat exchanger externally thereof is unnecessary. This feature, along with the elimination of the need for drainage holes as before described avoids any need for welding in the assembly process and of course further simplifies the heat exchanger construction.

It will be understood that the device in its illustrated form is subject to modification without departing from the invention. For example the plates may take other shapes than rectangular, and the depression-protuberances 16-17 may assume other shapes than circular. Also, the extensions might be omitted and their function carried out by the installed fin elements. Further, however, in applications where the purposes they serve are unnecessary, the fins on either or both sides of the plates 10 may be eliminated.

Still further, while the flow through the several chambers has been described as occurring in a single pass the flow through the heat exchanger could be made to follow multiple passes, as by closing off selected openings 19. In this area connection the arrangement of flow passes and of the connecting bosses advances the universal installation concept. The bosses are selectively usable as inlet and outlet parts and those not selected are closed.

What is claimed is:

1. A method of fabricating of a heat exchanger assembly, the fabrication being performed in a fixture having a bottom plate member, said member having longitudinally spaced recesses sized to receive fluid inlet and outlet bosses and having upstanding posts projecting vertically from said recesses, said heat exchanger assembly having alternating layers of plate elements and fin elements, said plate elements having openings to align with said recesses, n'm portions at said openings being deformed outwardly to define on one side of each plate a protuberance and on the other side a recess, said fin elements being in some instances less in length than the distance between said posts and in other instances having openings through which said posts extend and with which protuberances on said plates interfit, said method comprising: providing said fixture, dropping bosses over said posts, stacking said plate elements and said fin elements in alternating order, said posts extending through said plate openings, said plates being placed on said posts in relatively inverse relation so that protuberance-s of adjacent plates contact one another, the last provided plate element being disposed with its recessed side facing upwardly, dropping other bosses over said posts following the last provided plate element which bosses seat in the upwardly facing recesses of said last provided plate element, weighting said top plate element to apply in conjunction with said bottom plate a pressure to the interposed plate and fin elements for improved and more uniform contact therebetween, uniting the assembly comprising said bases, said plates and said fin elements into a unitary structure, and lifting the united assembly from said posts and from said bottom plate member.

2. A method according to claim 1, characterized in that the weighting of said top plate element is accomplished by placing over said posts in a superposed position to the last provided plate element a free floating weighted member capable of exerting the desired pressure, maintaining said weighted member in place while the assembly of plates, fin elements and bosses is united, and removing said free floating member following the uniting.

3. A method according to claim 2 wherein the step of uniting the assembly comprising said bosses, said plates and said fin elements is carried out by a metallurgical bonding process accomplished while said assembly is mounted on said posts and held between said bottom plate member and said free floating member.

References Cited UNITED STATES PATENTS 2,222,721 11/1940 Ramsaur et a1 -157 2,617,634 11/1952 Jendrassik 165-166 X 2,952,444 9/1960 Jenssen 165-167 3,212,572 10/1965 Otto 165-166 3,240,268 3/1966 Armes 165-167 3,345,726 10/ 1967 Hickman et al 29-202 X 3,263,314 8/1966 Smeltzer et a1. 29-1573 JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Assistant Examiner US. Cl. X.R. 29-202; 113-118