US3540531A - Plate heat exchanger - Google Patents

Description

United States Patent Inventor Rudolf Becker 56] References Cited 1 N ga g; Germany UNITED STATES PATENTS P 3,282,334 11/1966 Stahlheber 165/166 FIed 1968 3 372 743 3/1968 P 11 t 1 165/166 Patented Nov. 17, 1970 y a e a Assignee Linde Aktiengesellschaft Primary Examiner Robert A. OLeary Wiesbaden, Germany Asristant Examiner-Theophil W. Streule a corporation of Germany Anomey Karl F. Ross Priority Aug. 22, 1967 Germany 1,501,212 ABSTRACT: A plate-type heat exchanger having a stack of mutually spaced parallel plates defining at least two sets of passages in heat-transferring relationship and spacers between PLAID; HEAT the plates for maintaining same in spaced relationship. At least 6 Clams 8 Drawmg one wall in said housing laterally flanks the stack and is in con- U.S. Cl 165/166 tact therewith along an inner surface of the wall while the wall Int. Cl F28f 3/00 defines a pressurized chamber along its outer surface. The Field ofSearch 165/157, spacers are corrugated members between each pair of said 166.167.168.164-166 plates.

L a 14 a 23 s 2 1a 1 I A I /X A W? I YI I IW .2 111\/\/\/\ I I I I I I 5 I I I I I I IIZ\/\/\/\ 1 1 1 1 1 1 1 F fiAZ\/\/\/\/\ 25 I I I I I I I I I \X\/\/\/\N\/\/\/ I\N I I I 1 MM NW //I\I/ /l /Z Patented Nov. 17, 1970 Sheet 1 014 A /Il/l||ll INVENTOR. Rudolf Becker Attorney Patented Nov. 17, 1970 Sheet r m. C R a b e M u u 8m l 5 mm m R 3 A m /A 1 m u m IA A Y m M11 ,1, V m n V m W 1 A V m w v. d V1 .A b/L m m w 2 4 m s il Attorney Patented Nov. 17,1970 3,546,531

Sheet 3 01'4 217 103 202 I 207 m 1 x 207 Fig. 5

A {Boss Attorney PLATE HEAT EXCHANGER SPECIFICATION The present invention relates to a plate heat exchanger and, more particularly, to a lightweight, simply constructed heat exchanger, especially for cryogenic processes such as Linde- Frankl air rectification.

While various types of plate heat exchangers have been proposed heretofore, perhaps the sole characteristic of substantially all of them has been the considerable expense resulting from the complex methods of assembly and the difficulties inherent in producing them. More specifically, it can be pointed out that plate heat exchangers of this type are fortned internally with numerous plates and are sealed along the sides of the plate assembly by lateral housing plates which are soldered or welded to the heat-exchange plates. The soldering step involves considerable complication since efficient heat exchangers are characterized by numerous plates in the stack and relatively small intcrplatc spacing, thereby making it necessary to solder or weld a large number ofjoint end seams. Besides the added cost and production delays resulting from such assembly procedures, there is the disadvantage that tight work and the large numbers of joints give rise, almost as a necessary evil, to flaws and, therefore, bursting of the device at one or more of its scams. Such difficulties are, because of the nature of the sealed unit, substantially irreparable.

It is, therefore, the principal object of the present invention to provide a plate heat exchanger which avoids the aforementioned disadvantages and can be produced in a simple, convcnient and inexpensive manner.

Still another object of this invention is to provide a plate heat exchanger, especially designed for use in cryogenic systems and particularly those for the rectification of air, which has a high efficiency and fluid throughput.-

These objects are obtained, in accordance with the present invention, by providing a heat exchanger having a stack of plates with intervening supporting elements, the stack being bounded laterally with at least one pressure wall which clamps the stack against an opposing wall, the latter preferably being under pressure as well. These walls, preferably lying parallel to the plates of the stack. are formed along their sides turned away from the stack (Le. verso) as one wall of a pressure chamber to which the fluid is supplied at elevated pressure. When more than one pressure chamber is provided, it is found to be advantageous to interconnect them and thereby ensure a common pressure level in all the pressure chambers. The ex ternally applied pressure, moreover, acts to counter the pres sure within the heat exchanger and thereby prevents forces from developing which may damage the unit. The externally applied pressure also serves to stiffen the lateral wall or walls of the heatcxchanger chamber and stack against outward forces applied to this wall when the heat exchanger is in use and thus further serves to limit deformation of the heat exchanger or the plates of the stack.

Thus it is a principal feature of the present invention that the heat exchanger, which may also be of any type other than the air rectification heat exchanger mentioned earlier, com prises a stack of mutually spaced parallel plates defining at least two sets of passages in heat-transferring relationship via these places. A spacer means is interposed between the plates for maintaining them in spaced relationship under pressure from without, thereby ensuring constant flow cross section and stability in spite of the externally applied pressure. The heat exchanger has a housing at least one wall of which flanks the stack and contacts the latter (tug. at one of the plates or spacers) along an inner surface of the wall; the outer surface of the latter is subjected to fluid pressure from at least one chamber defined between the wall and a housing. The pressurizable wall may thus comprise a so-called pressure bottom.

According to a more specific feature of this invention, the stack of heat-exchanger plates is received between or flanked by a pair of such pressurizable walls which extend parallel to one another at opposite sides of the stack. The walls also may run parallel to the plates which, within the heat-exchange zone, are substantially coextensivev with the pressurizable walls; the latter may, however, extend out of the heatexchange compartment beyond the stack. In one embodiment of this invention, the housing defines with each of the pres surizable walls, along the outer surface thereof, a respective chamber individual to that wall. Alternatively, a common chamber can surround the heat-exchanger compartment and encompass both pressurizable walls or more such walls if provided. However, it is possible to make use of a single pressurizable wall and yet obtain the effectiveness of a two-wall structure. In this case, a relatively massive, i.e.pressure-re' sistant, wall is rigid with the housing and bears upon one side of the stack in a manner analogous to the arrangement of one ofthe pressurizable walls mentioned earlier. On the other side of the stack, however, a somewhat thinner, pressure-yielding wall (of the type described earlier) bears upon the stack at a pressure applied front without front a chamber within the housing at this opposite side of the stack. In this case, the relatively massive wall is drawn against the stack by the reaction force generated in the chamber.

It has also been found to be advantageous. when two fluids are to be passed in hcat-exchanging relationship, at different pressures, to provide that the pressurizable chamber CtHlIlllllnicates with the system for passing the higher pressure fluid through the heat exchanger. More specifically, one means can be provided for passing a relatively high-pressure fluid through one of said passages while another means passes a relatively low-pressure fluid through the other set of passages, the first means communicating with the pressurizablc chamber. Each of these means may include an inlet manifold or distributing chamber for feeding the fluid to the mutually parallel passages and also includes a collecting means for gathering the fluid passed through the corresponding passages, This system has proved to be satisfactory in cases in which pressures are different in the different sets of fluid passages, For example, condenser-evaporators for air-rectification installations (e.g. columns of the Linde-Frankl type) are provided with manifold feed chambers and manifold collecting chambers on opposite sides of the housing in comntunication with the respective sets of passages, the high-pressure system ofwhich is connected to the pressurizable chamber.

According to a further feature ofthis invention, the stack of heat-exchanger plates comprises a plurality of generally flat. mutually spaced parallel plates of identical configuration separated by a spacer means in the form of one or more generally corrugated members. The expression generally corrugated is used herein to describe zigzag, folded, undulat ing or wavy members having alternating crests and hollows, the crests and hollows being of angular or arcuate configuration. According to one feature of this invention, the generally flat plates are separated by shectlikc corrugated spacers which have alternating crests resting against the opposite plates of a respective pairso that each plate defines with the spacer sheet a channel through which the heat-exchange fluid can be passed. The channels of all of the plates may be parallel to one another and codirectional or, in accordance with another feature of this invention, oriented in different directions so that, for example, alternate sheets are turned orthogonally with respect to one another. Still another modification provides that the spacer elements, which lend rigidity to the stack, are constituted by strips spaced apart between the respective pairs ofplates but generally extending parallel to one another. It has been found to sufficewhen the high-pressure fluid acts upon the spacer sheets or members at spaced-apart locations so as to define, in effect, high-pressure ribs which increase the rigidity of the stack.

In other words, the support members can be relatively thinwalled elements which have their spacer effect reinforced by the presence of high-pressure (or low-pressure) fluid in the passages which they define with the plates. In some cases, it is desirable to separate the two sets of passages by the generally flat plate. In this case. alternating passages for the highand low-pressure fluid are provided along the stack so that the low-pressure passages or compartments are supported by the respective spacers and together therewith withstand the higher pressure. When the corrugated sheets are used. however. it is desirable to alternate between highand low-pressure channels between each set of plates and along the hollows and troughs thereof.

The above and other objects, features and advantages of the present invention will become more readily apparent from the following description. reference being made to the accentpanying drawing in which:

FIG. I is a vertical cross section through a plate-type heat exchanger serving as a condenserevaporator for a cryogenic installation;

FIG. 2 is across section taken along the lines II-Il of FIG. 1'.

FIG. 3 is a cross section along the lines Ill-lll of FIG. I;

FIG. 4 is a cross section generally along the lines IV-IV of FIG. 1 but directed to another embodiment;

FIG. 5 is a cross-sectional view of still another plate-heat exchanger;

FIG. 6 is a cross scctional view of a single-chamber heat exchanger;

FIG. 7 is a detail view ofthe system of FIG. 6; and

FIG. 8 is a cross-sectional detail view corresponding to a modification ofthe system of FIG. 7.

In FIGS. 1 and 2. I show a heat exchanger adapted to the use as a condcnser-cvaporator fora Lindc-Frankl air rectification installation in which the heat exchanger step is formed with a first set of passages l and a second set of passages 2 defined between mutually parallel spaced-apart plates 3 which have not been shown with wall thickness in FIGS. I and 2 so as to maintain the proportion of the drawing. Between the plates 3 which define the passages I and 2 in pairs. I provide undulating sheets for a corrugated sheet metal (seen in cross section in FIG. 2) in the space forming the passages I. In the alternate spaces. defining the passages 2. I have provided a plurality of spaced-apart strips 5 which are also of corrugated or zigzag configuration but are welded on a bias (see FIG. 3) to hold the plates 3 apart.

The resulting stack of heat exchangers is flanked by a pair of pressuredeformable walls 6 and 7 which lie parallel to the plate 3 and are generally coextensive therewith within the heat-exchange compartment H. Along their inner surfaces. these walls rest against the stacks but have an overall height 8 (FIG. I) such that they extend somewhat beyond the plates and the chamber H to form part of the housing. Along their periphery. the walls 6 and 7 are welded at seams 6a. 7a to the lower and upper plates 9 and 10 which. together with walls 6 and 7. enclose the hcatexchange compartment H. A pair of domes 20a and 2Iu are also welded at 60. 7a to the walls 6 and 7 so as to define pressurizable chambers 20. 2] with the outer surfaces I8 and [9 of these walls.

As is customary in the condensor-evaporator of an air rectification installation. the bottom plate 9 is perforated at 14 to allow liquid oxygen to pass through into a distributing compartment I2 and then through the latter into the passages 1. Communication between the passages I and the distributing chamber I2 is established between the plates of alternate pairs, the other pairs being provided with filling strips 16 and 17 so as to seal their interior. Above the plate 3 and below the upper plate 10. there is defined a collecting compartment I3 into which the vaporizable or vaporizing medium passes for further movement into the column via the perforation in plate 10. As oxygen passes upwardly through the channels I. it is vaporized in heat exchange with nitrogen in passages 2. the nitrogen being liquefied in the process. The vaporized oxygen passes out through the collecting compartment 13 and the perforations 15 previously mentioned.

As noted earlier, the filler strips 16 and I7 enclose the spaces between plates 3 which define the passages 2 and also prevent the nitrogen from entering the distribution compartment 12. the passages I and the collecting compartment l3.

As shown in FIG. 2, the gaseous condensable medium. in this case nitrogen. is introduced at a distribution compartment 22 which communicates with the passages 2 while. in the rcgion of this compartment, the passages l are scaled from the compartment by filler strips 25. A similar chamber on the opposite end ol'the stacks is provided to collect the uncondcnsed nitrogen if desired. Since the gaseous medium is at elevated pressure with respect to the oxygen, I have found it to be advantageous to connect the pressure chambers 20 and 21 with the inlet compartment 22. To this end, I provide passages 23 and 24. the former being bored through extensions ofthe pressurized walls 6 and 7. The filler strip 25 prevents leakage of oxygen into the nitrogen space as well as leakage of the nitrogen into the oxygen passages.

FIG. 3 shows a section through one of the nitrogen passages terminating in the distribution compartment 22. Partitions 29 and 30 close off the compartment 22 from the inlet and outlet manifold chambers I2 and 13. The bias-folded spacer strips 5. which are of corrugated sheet metal (FIG. I) extend downwardly from the plate I7 but terminate short ofthe lower plate 15 to enable the liquid nitrogen to pass along the latter for collection in any desired manner. The strips 5 need be dimensioned only to withstand the relatively low pressure in the oxygen passages I in the event of failure of the nitrogen pressure in passages 2. Approximately halfway along the upper strip I7 of each of the passages 2. I provide a bore 26 and a leadout tube 28 whose hood 27 overlies the bore 26 to collect the helium gases of the hood 27 where the system is used for the rectification of air. In this manner. the helium is prevented from mixing with the oxygen in the space I3.

In FIG. 4 there is shown a modification of the system of FIGS. I through 3 corresponding to a section along the line lV-lV of FIG. I. and in which the corrugated sheets in the passages l are subdivided vertically into three sealed sections collectively represented at 104 but individually shown at 1040, l04b and 1040.

FIG. 5 shows an embodiment of this invention wherein the housing consists of a cylindrical shell 232 which encloses a pressure chamber 232a common to both of the lateral walls 206. 207 flanking the stack which is made of plates 203 defined in passages 201 and 202 and separating sheets 204 or corrugated strips 205. all as previously described with respect to passages I. 2, plates 3, spacers 4. Sand walls 6. 7. The exterior surfaces 218 and 219 of the walls 206. 207 are exposed to the pressure in the chamber 232a. A pair of coaxial cylindrical segments 209 and 210 are welded to the pressureyieldable walls 206. 207 and define with the stack the feed and collecting compartments 212 and 217 or one of the heatexchange fluids. Filler strips 216 and 217 prevent the other fluid from leaking into the first fluid space and vice versa.

As previously noted, it is also possible to use only a single pressurizable yieldable wall as shown at 37 in FIG. 6. In this embodiment. the stack comprises mutually spaced parallel plates a. 35b, etc. and rests against the rigid, nonyieldable and relatively massive wall 38 at the right-hand side of that housing. The pressure-yieldable wall 37, at the other side of the housing, bears against the other side of the stack at the pressure within the chamber 44 and acts upon the outwardly turned face 43 of this wall 37.

Between each of the plates 35a, 35b, etc. and an adjoining plate, there is provided a spacer sheet 36 of corrugated configuration such that the crests 45 of each sheet bear upon one of the plates 35a. 45b alternately while the remaining crests bear upon the opposed plates. Upper and lower walls 41 and 42 secure the massive wall 38 to the chamber 44 and define. with the stack. the collecting compartment and the feed compartment ofone of the stacks of passages. Chamber 47 is connected with the high-pressure fluid passages in the manner described earlier. The corrugated sheets 36 serve to reinforce the plates 35a. 35b, etc. against compressive and expansive forces and also to limit deformation of the individual plates within the heat-exchanger stack. In addition. the hollows of these corrugated sheets define passages 39a, 39. a and 40 which alternate with one another and are sealed against leakage therebetween When high-pressure fluid is introduced into the hollows 41, 40 and 40a, for example, low-pressure fluid can be introduced into the alternate channels 39a.

ln FIGS. 7 and 8, there is shown to detail views of a heatexchanger stack according to this invention wherein, as in FIG. 5, filler strips 47, 48 seal the peripheries of the respective passagesln the same system of FIG. 7, planar plates 50 are separated by corrugated sheets 51 to define the alternating channels 54 and 55 which are supplied with the different fluids to be brought into heat-exchanging relationship. Air can, in the system of FIG. 7. pass through both sets of passages 54. 55 in countercurrent to another medium, for example nitrogen. which is passed through the adjoining passages. Alternatively. the nitrogen can he passed through the passages 55, for example. while the nitrogen is delivered to the passages 54. In H0. 8. a similar arrangement is shown wherein, however, the corrugated plate 351 is shown to he turned at right angles to the plates 5l so that transverse flow rather than countercurrcnt flow can be achieved.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scopeof the invention except as limited by the appended claims l claim:

1 A plate-type heat exchanger, comprising:

a housing;

a stack of mutually spaced parallel heat exchanger plates defining passages in heat-transferring relationship and respective turbulence-promoting formations extending along said passages for promoting heat exchange between fluids traversing said passages;

an inlet extending through said housing and communicating with at least one set of said passages, and an outlet extending through said housing and communicating with said set ofsaid passages;

at least one wall flanking said stack and independent of the plates thereof and extending parallel to said plates for enclosing the space occupied by said stack while defining within said housing a pressurizable chamber outwardly of said'space; and

means for maintaining said chamber at approximately the pressure in said space whereby said wall is maintained substantially free from pressure differential thereacross.

2. The plate-type heat exchanger defined in claim I wherein a pair of such walls flanks said stack on opposite sides of said space and extend parallel to said plates. saidwalls each having an outer surface turned away from said plates and exposed to pressure in said chamber.

3. The plate-type heat exchanger defined in claim 1 wherein said passages include a second set of passages in heatexchanging relationship with the first-mentioned set of passages said heat exchanger further comprising an inlet extending through said housing ahd communicating with the second set of passages and an outlet communicating with said second set of passages and extending through said housing. one of said sets of passages being traversed by a relatively high-pressure fluid and the other set of passages being traversed by a relatively low-pressure fluid, said chamber communicating with said one of said sets of passages for pressurization by said relatively high-pressure fluid substantially at the pressure thereof.

4. The plate-type heat exchanger defined in claim I wherein said plates are relatively thin sheet metal members and said wall is a relatively thick plate, said heat exchanger further comprising a plurality of corrugated sheet metal elements between each pair of'plates of said stack and subdividing the spaces between them into respective passages.

5. The plate-type heat exchanger defined in claim 4 wherein said corrugated sheet metal elements are strips spaced apart between respective plairs ofthe plates of said stack.

6. The plate-type eat exchanger defined in claim I wherein said corrugated elements are corrugated sheets'substantially coextensive with the respective plates of said stack and having alternate crests engaging same, while hollows between said crests define said passages with said plates of said stack, alternate sheets having their crests and hollows lying in mutually parallel planes but in orthogonal orientation.

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