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Publication numberUS3847211 A
Publication typeGrant
Publication dateNov 12, 1974
Filing dateJan 28, 1969
Priority dateJan 28, 1969
Publication numberUS 3847211 A, US 3847211A, US-A-3847211, US3847211 A, US3847211A
InventorsH Fischel, A Dichiro
Original AssigneeSub Marine Syst Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Property interchange system for fluids
US 3847211 A
A system is provided for interchanging properties such as thermal energy, ions or particles, between fluids, such as liquids or gases. Two fluids flow in countercurrent fashion along small, densely packed passageways within an assembly of individual thin plastic membranes formed into a compact multilayer laminate. Standardized membranes are utilized that are self supporting and unite into an assembly that maintains its structural integrity under high thermal stresses. The membrane configurations dispose the individual passageways in selected relation, maintain the fluids separate, and automatically direct the fluids into and out of the passageway system. The flow passageways for different fluids are interspersed so that the fluid within each small passageway is substantially completely encompassed by flowing volumes of the other fluid and property interchange takes place in three-dimensional fashion directly through the passageway walls. High heat transfer coefficients and total heat transfer efficiency are achieved with low fluid pressure gradients by the use of straight, short laminar flows within the small passageways. Limitations imposed by nonuniformities in flow between the passageways are overcome by means for lateral integration of the property states existing in selected passageway sets.
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United States Patent [1 1 Fischel et a1.

1 1 PROPERTY INTERCHANGE SYSTEM FOR FLUIDS [75] Inventors: Halbert Fischel, Van Nuys; Anthony Dichiro, Sun Valley, both of Calif.

[22] Filed: Jan. 28, 1969 [21] Appl. N0.: 794,705

[52] US. Cl. 165/166, 161/133 [51] Int. Cl. F281) 3/12 [58] Field of Search 165/166, 5, 10, 4; 156/207, 208-211 [56] References Cited UNITED STATES PATENTS 2,173,815 5/1937 51152 et a1 156/207 X 2.429.482 10/1947 Munters 156/208 2,553,030 5/1951 Bell l 165/166 2,602,645 4/1948 Benenati et al.... 165/4 2,812,165 11/1957 Hammond l65/166 3 081,822 3/1963 Wolansky et al. 165/10 3,165,152 1/1965 Jones l l l l l 1 1. 165/166 3,212,57 10/1965 Otto 165/166 3 256,930 6/1966 Norback 165/166 X 3 305,010 2/1967 Campbell et a1 165/166 3,334,399 8/1967 Teeguarden 165/166 X 3,444,925 5/1969 Johnson .1 165/166 3,449,157 6/1969 Wandel 156/210 3,451,473 6/1969 Urie et al.... 165/166 3,490,523 [[1970 Esmond 165/166 FOREIGN PATENTS OR APPLICATIONS 1,106,660 3/1968 Great Britain 165/10 passageways fluids separate, and automaticalmhe fluids [451 Nov. 12, 1974 5 7 1 ABSTRACT A system is provided for interchanging properties such as thermal energy, ions or particles, between fluids, such as liquids or gases. Two fluids flow in countercurrent fashion along small, densely packed passageways within anassembly of individual thin plastic membranes formed into a compact multilayer laminate. Standardized membranes are utilized that are self supporting and unite into an assembly that maintains its structural integrity under high thermal stresses. The membrane configurations dispose the individual in selected relation, maintain the into and out of the passageway system. The flow pas sageways for different fluids are interspersed so that the fluid within each small passageway is substantially completely encompassed by flowing volumes of the other fluid and property interchange takes place in three-dimensional fashion directly through the passageway walls. High heat transfer coefficients and total heat transfer efficiency are achieved with low fluid pressure gradients by the use of straight, short laminar flows within the small passageways. Limitations imposed by nonuniformities in flow between the passageways are overcome by means for lateral inte gration of the property states existing in selected passageway sets.


saw u at 7 TERTIARY GAS our FlG.-8

BOIL- OFF FIRST MANIFOLD 1 us ems l 92 I27 I26 HALBERT' FISCHEL BY ANTHONY D'ICHIRO YWM i A TTO NEYS PATENTEUNBY 1 2 4974 SEEN 5 INVENTORS HALBERT FISCHEL BY ANTHONY mcmno Fm g ATTORNEYS ATENTEDHUY 12 I974 MEN 8 0F 7 so: m3 225% INVENTORS HALBERT FISCHEL ANTHONY DICHIRO ATTOR 1 PROPERTY INTERCHANGE SYSTEM FOR FLUIDS interchange is effected between fluids, some substantial degree of improvement is possible in terms of operating characteristics orcost' factors. 'In counter-flow heat exchangers, for example, low cost is generally considered incompatible withhigh heat transfer coefficient and temperature exchangeefficiency, a concept. given quantitative definition below. Temperature exchange efficiency is one'important aspect of exchanger performance and is used'hereafter to provide a qualitative reference for discussion and understanding. As discussed generally in the book Compact Heat Exchangers, 2nd Edition ,.by W. M. Kays and A. L. London, published by McGraw-Hill Book Co., N. Y. (1964) at page 15, temperature exchange efficiency (sometimes simply T.E.E. herein), is 'determinedby:

T.E.E-. l -BT/AT-where AT the difference between thetemperaturesof two fluids at one end'of an exchanger after interchange has taken place,

' and i AT the totaltemperatu'r'e range through which the fluid is taken between ends'of the exchanger.

A'value approaching unity thus connoteshigh per-- form-ance," but it must' berecognized'that the exchange efficiency value does not provide afully definitive expression ofperformance because" flow rate'mustals'o be considered, as is pointed outjin more detail below. Nonetheless, the same basic relationshipfgiven anyas- 'sumed flow rate, providesa comparative measure that is useful whether evaluating exchange of temperature (as above) or other properties.

Where extremely high temperature exchange. efficiency is-needed,.it is now generally necessary to use, extremely long heat exchangepath lengths, convolutedpaths and multiple passesof fluids through the system. Expensively fabricated structures, generally made of metal for high heat conductivity, areemployed together with complicated. headers or manifolds. Multiple passes and large flow differential pressures are usually needed to obtain efficiency values of the order of 0;98 and above. 1

Existing types of high efficiency systems have one or more of several'additional disadvantages. Thermal gradients within the fluids themselves limit efficiency unless passageway areas are small or-turbule'nce is.introduced. A finely divided'passageway system is generally achieved only at substantial increases in cost and complexity of both theheat exchanger andthe headering portions of the system. The introduction of turbulent flow tends to markedly increase pressure gradients and reduce flow rates.

In addition, a short, efficient and high flow counter current unit has a-sharp thermalgradient along its length. I-leat therefore tends to'flow longitudinally along the separator walls, to an extent dependent-upon the thermalv gradient, and this longitudinal'heat conduction often-imposes its own limit on total heat-transfer efficiency. I-Iighthermal gradients also introduce substantial thermal stresses which'cannot readily be withstood without the use of high strength, massive parts. The use of such parts, however, limits efficiency. The efficiency of existing systems is also diminished by non-uniformity of flow distribution within the variouspassageways, due to membrane distortion and small variations-in passageway cross section. Thesefactors become extremely significant when veryhigh efficiencies (e.g. in excess of 0.95) are sought'tobe'attained.

' ltisgenerallypreferred, in order to obtain highproperty interchange efficiency values, to flow the fluids whose properties are to beinterchanged in countercurrent relationship, and to obtain a high ratio of transfer" area to flow volume. With the widespread useof closed cycle cryogenic systems,'for example, there isaneed for heat exchangers which can effectivelyconserverefrigeration power or a cryogenic supply.'Mobile'I-versions of such systems generally must be very small, have high efficiency andin some instances should introduce only a low pressure gradient. lt'hasnot heretofore been considered feasible to satisfy all the mentioned physicaland performance requirementssimultaneously.

Significant additionalproblems are also presented by theneed for appropriatetmanifolds or headers-for feeding' fluids to; and receiving fluids from the separateflow pathspsmalland numerous passageways canimprove the interchange 'efficiencyfbut disproportionately increase the costs of! the header mechanism; The costs and complexities. of header" systems have been major factors in limiting the use 'of c untercurrent flow'systerns. Attempts have been mad'e'toutilize plastic elements for property exchange functions' because'their initial'and fabricatingcosts are low. Such units v have,

however,- beenrelaitive'ly complex, intended only for limited applications, and have moreover provided only relatively low transfer efficiency values.

The interchange of thermal energybetween fluids;

through a membrane has counterpartsin many. other systems, such as those which interchange particle matter, ionic matter or chemical constituents. In dialysis and oxygenatorsystems,- for example, one liquid substance such as bloodmaybe passed on one side of a suitable membrane while a glucose, plasma, saline or.

. other solution is passed on the other sideof the'mmembrane.-lmpurities are drawn into the solution from the. blood, thereby purifying the blood. A countercurrent.

relationship is useful for such systems, in order to achieve high efficiency in extraction of impurities. The;

requirement that there be an extremely high interchange area'to liquid volume relationship also.obtains-,. but in addition critical requirementsare imposed! on.

the handling of the blood. Blood isa sensitive tissuelike member that cannot be subjected tothermal shock, mechanical trauma, or substantial differential pressures and consequently the pressure gradient must be very low throughout the entire interchange system. The same desirable features are sought for other prop erty interchange systems for fluids, including gas-liquid systems and dual gas systems.

SUMMARY on THE INVENTION Asystem for interchanging properties of different ingwith both the internal passageways and external headers. Planar supportelements may be alternated with corrugated membranes within the laminate to unify and rigidify the structure against thermal stresses.

- The support elements are preferably bonded to the checkerboard disposition. In some of. the heat ex- I changer exemplifrcations of the invention, the walls have low thermal conductivity but are so thin that they do not interpose a significantthermal barrier between adjacent fluid segments. Extremely high ratios of interchange surface area to total fluid volume, thin-walled membranes, and optimum and intimate interspersion of laminar-flow fluids in a great multiplicity of small passageways result in temperature interchange between the two fluids with high heat transfer coefficient, without substantial pressure drop.

A feature of the invention is the disposition of a matrix of minute passageways for counter'currentflowing fluids in such fashion as'to achieve virtually optimum three-dimensional transfer effects. Each passageway has a height to width ratio of approximately lzl, with :-,the'pa ssag'eways within separate laminate layers being precisely positioned. Each column of fluid issurrounded by columns of the countercurrent fluid. Passageway' densities inexcess of severalthousand per squareinch of cross section are readily achieved, although the internal fluid volume still occupies a high proportion;(e.g., in excess of 80 percent) of the total -interchange '=volume. There is also'an' extremely high ratio of transfer area to unit volume, this being in excess-of lOO in /in 'in 'onepractical example. i

in accordance with the invention the property states of fluids in separate lines of now maybe equalized or integrated to minimize the effects of flow rate differences arisingfromdimensional and other variations. Such integration maybe realized in a heat exchanger having membranesof'relatively low heat conductivity by strips intersecting lines of flow and transferring heat between separateipassageways. in one exemplification a number of lateral conductive strips are spaced apart along the length of the structure. Alternatively, longitudinally separated internal header "regions may be spa'cedalong the flow paths to physically mix flows from individual pasageways in selected regions. Elongated lateral apertures may be incorporated at various regions within spacers between the membranes to allow periodic physical mixing for the same purpose. Alternatively o'rjin addition,- integration may. be effected by inducing turbulence within flow paths by roughening the sides of the corrugations in contact with the flows, for

example. These means may be used separately or to gether-in varying cpmbinations. Further in accordance with the invention, particular membraneand header configurations may be utilized to overcome the mechanical, cost, and volume limitations of the prior art. in a specific example, very thin nodes of the" corrugations internally, as well as along selected regions of the periphery. Because of the thin pliant nature of the membranes, and the physical integrityof the assembly, temperature. differences of several hundred C over a little more than a foot in length have been realized without adverse effects on structural or operative properties.

in one example in accordance with the invention, only two standardized types of corrugated plastic membranes together with alternate flat membranes are employed in forming an assembly. Each corrugated membrane includes a central corrugated region, peripheral lip portions at the sides and end, header transition regions adjacent the ends, and selected depressed surfaces in the peripheral lip portions adjacent eachend. in the header transition regions, themembrane deviations are only on one side of the median plane for the membrane, permitting at least partially transverse flow across the membrane. The first and second types'of membranes are essentially mirror images, such thatbetween first alternate pairs the headertransitionregions and the depressed surfaces'in the peripheral lips face each other to define internal header transition volumes communicatingv with first peripheral apertures. Be

tween the alternate pairs, however, peripheral aper;

of such membranes may be utilized, and they communicate with end headers or side headers. Thusthe ex-' changer design may utilize, at a given end, two adjacent end headers, two side-headers, or various combinations of these. in the header transition regions the longitudinalflows are atleast partially transversely directed toward the appropriate headers, without the introduction of a significant pressure drop.

Property exchange systems in accordance with the invention may be advantageously fabricated by ther moforming in a controlled heating cycle using matched molds, and assembling the membranes together with interposed support sheets in bonded relation by spray ing the facing surfaces with an adhesive mixture, and assembling subunits into a complete body while maintaining-desired alignments.

I BRIEF li'ESCRIPTlON OF THE DRAWINGS A better understanding of the invention may be had FIG. 3 is an enlarged exploded simplified view of a portion of the assembly of FIG. 1;

FIG. 4 is an enlarged perspective view of an end fragment of one corrugated membrane of the arrangement of FIG. 1;

FIG. 5 is a fragmentary perspective view of one corner of the interchange system of FIG. 1, showing the fluid flow paths in greater detail;

FIG. 6 is an enlarged cross sectional view of the relationship of individual corrugations in the system of FIG. 1;

FIG. 7 is a broken away perspective view of a second property interchange system in accordance with the inventlon;

FIG. 8 is an enlarged fragmentary view of a portion of the system of FIG. 7;

FIG. 9 is a simplified exploded view of a portion of a third property interchange system in accordance with the invention;

FIG. 10 is an enlarged fragmentary view of a portion of a membrane employed in the system of FIG. 9;

FIG. 11 is an end view ofan assembly comprising the portions of FIG. 9;and

FIG. 12 is an exploded perspective view of a portion of membranes and spacers used in a different arrangement in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION A property interchange system for fluids, referring now to FIGS. 1-5, comprises a heat exchange system for gases that are to beoppositely shifted in temperature between limits'which lie in the ambient range at one extreme and in the near-liquid nitrogen range at the'other extreme. For many closed cycle cryogenic applications, conservative use of refrigeration capacity requires a highly effective heat interchange,'although it is also generally desirable that the exchange unit be compact, inexpensive and readily fabricated. Such needs are typified by closed circuit, self-contained underwater breathing apparatus using cryogenic fluids.

The system illustrated in FIGS. 1-5 fulfills all of these functions and further maintains its structural and operative integrity even though the opposite ends of the unit may be maintained at a temperature differential substantially in excess of 200C. As previously discussed, however, a heat exchanger is merely one example of applications of the concepts of the invention.

As best seen in FIG. 1, the heat exchanger l0comprises a generally rectangular central body with a set of inlet and outlet headers ormanifolds. The principal gas flow paths along the central interchange volume within the exchanger 10 are parallel to its longitudinal central axis. The inlet and outlet headers may, as will be evident hereafter, be widely varied in size, shape and position, or reversed in function. For purposes of illustration, however, an inlet header 12 and an outlet header 13 for a first gas are disposed at opposite longitudinal ends of the exchanger 10, coaxial with the central axis and communicating with slot-like apertures 14in the ends of the exchanger 10. An inlet header l5 and an outlet header 16 for a second gas communicate with slot-like apertures 17 adjacent different ends and on opposite sides of the exchanger Ill). The first gas, here assumed for purposes of illustration to be at or near ambient temperature, thus passes directly along the length of the exchanger 10 between the inlet header l2 and the outlet header 13, whereas the second gas, as-

sumed to be initially at near-cryogenic temperature (e.g. liquid nitrogen), passes from the inlet header I5 transversely into the interior of the exchanger 10, then passes along the length of the exchanger 10 in a direction opposite to the first gas until approximately abreast of the outlet header 16, at which region it is diverted transversely out into the outlet header 16 through the apertures 17.

Within the interchange volume in the generally central region of the header 10, the two gases pass in intimate countercurrent flow r'ealtionship in a mannerillustrated in enlarged form in FIG. 2. The first gas (designated A) and the second gas (designated B) are separated vertically into alternating thin sheet-like volumes or passages which are also separated transversely by the corrugations into small spaced passageways. The passageways for the type A gas are alternated with passageways for the type B gas, as shown in FIG. 2. This construction is achieved by deployinga multiplicity of corrugated membranes in multi-laminate fashion, with precise alignment of corrugations between layers. Although for forming purposes the corrugations or undulations are generally sinusoidal in form as shown in FIG. 2, it will be appreciated that the terms corrugations or undulations are used for convenience and for ready visualizationand that in fact any of a wide variety of shapes incorporating deviations from the principal membrane plane, may be employed. For example, the membrane may include ridges and grooves that deviate' from a central plane in bidirectional fashion, or ridges which simply deviate in one direction. The'de'viations may be periodic or aperiodic and may be'curvilinear or rectangular in shape. Lateral heat transfer between the flows in the separate passageways is achieved by means of the heat conducting strip 11 in FIG. 2, as

- is described in greater'detail hereafter.

The relationshipand construction shown in FIG. 2 provide a highly effective heat interchange configuration. A plurality of corrugated membranes 20, 22 of first and second types respectively are disposed in alternating fashion through the height of the exchanger 10.

Planar support membranes 24 are interposed between each pair of membranes 20, 22. The first and secondv types of corrguated membranes 20, 22 have minute' corrugations lying in inphase relationship. The distinction' between the two types is primarily in a mirror image relationship useful in forming the complete laminate and described in greater detail below.

The cross sectional areas within the passageways designated A and B are extremely small, as are the corrugation height, designated by h, and the corrugation width,-designated by w. In one practical example, the dimensions h and w are approximately in a l-to-l ratio, and each is approximately 0.020 inches, so that there are approximately corrugations per inch. As can be seen in FIG. 2, each passageway containing an A gas is substantially surrounded by passageways containing the B gas, and vice versa. This checkerboard-type pattern (as viewed in vertical section through the core of the exchanger) is dependent upon the maintenance of .the inter-laminate alignment as well as relatively v rections relative to the center of a passageway. Ex-

'tremely thin membranes are employed, those in this example being of the order of 0.002 inches in thickness. The passageways are so small and the walls so thin that interchange. of properties readily takes place between fluids on opposite sides of the passageways. The heat transfer area presented between the counter-flowing gases is greatly extended by the corrugations in the membranes and the area has an extremely high ratio to the confined volumes of gasesi in the practical example being discussed, there is a ratio of about 100 in of transfer for each cubic inch of volume. Further, over 80 percent .of thetotal volume is devoted to fluid flow. The-exch'angerthus comprises a dense matrix of passageways, having. in excess of about 250 passageways per square inch, and as many as several thousand passageways per square inch.

. Consequently, it is feasible for the first time to utilize lowcost plastic heat exchange elementsin achieving extremely high temperature exchange efficiency. Another advantage is that the exchanger body E of FIG. I may be extremely short, such as approximately fifteen inches in overall length, yet operate through an jap pro ximately 200 C. temperatureydifferential between the opposite ends'without significant loss of efficiency: due to longitudinal conduction. Temperature gradients in excess of C. per inch, and as many as about C. per inch, have been realized. A significant further advantage is derived from the fact that the short length of flow, the'multiplicity of flow paths and the use of laminar flow introduce only a minimum pressure gradient. I I v v An added important advantage comes from the presence of the conductingstrip's ll,1which facilitate lateral temperature integration of the separate flows. The significance of suchi'ntegration is based on the followiing considerations. Uneven mass flow between adjacent flow paths results in temperature differentialsbetween them, varying approximately directly with the difference in mass flowbetween the flow'paths. The resulting temperature imbalance repeated for many different paths hasa net effect of causing larger temperature differenc es at the ends of the heat exchanger between entering and exiting gases than in the caseof perfectly 'uniformiflow. This heat differential due to non-uniform flow imposes an upper limit'on temperature exchange efficiency differing by a second order quantity from 100 percent. A variationof 1 percent, for example, in passage diameter, which results in a 4 percent imbalance in respective mass flows, makes it impossible without some form of integration to achieve greater than 96 percent temperature exchange efficiency in practice.

In order to minimize the effects of inequalities, a mulsageways. Longitudinal heat conduction is not significantly affected, because the strips 11 are separated by substantial distances in comparison to their longitudinal dimension. This lateral integration function suppresses the effects of non-uniform flow distribution, raising the upper limit of overall heat transfer efficiency for given dimensional and flow tolerances. A fuller exposition of the problem may be found in an article in Advances in Cryogenic Engineering, Volume 12, Plenum Press, 1967, entitled The Effects of Flow Distribution in Parallel Channels of a Counter Flow Heat Exchanger, by R. B. Fleming, Page 352.

it should be noted that the lower face of one mem brane and the upper face of the adjacent membrane completely confine one particular gas. The planar support membranes 24, 24' are not required for gas separation, but assist in preserving the physical relationship of the elements of the system under'the'stresses introduced by a sharp temperature gradient along the exchanger 10. It is preferred for temperature stability,

between adjacent corrugated membranesmay then be bonded, if desired.

Materials used for the conductive strips are of standard heat-conductive type, ,such as aluminum orcopper, and may be vacuum deposited or affixed as a film. in addition, it is preferred to bondthe nodal points of the corrugations to the abutting surfaces of the planar support elements 24, as is more fully described below- The longitudinal dimensions and numberv of conductive strips 11 may be increasedto include the case in which the entire interchange area of a membrane has a thin heat conductive coating. Such a result is permissible in some applications, in which the adverse effects of longitudinal conduction are more than offset by the beneficial effects of lateral integration. Bearing in mind that small passageways having thin walls are utilized, the membranes may in fact be of a good heat conductor material for some applications. I It will be recognized that heat exchangers of the regenerator type use corrugated membranes interspersed between planar members, and that heat exchangers of other types, such as the crosscurrent type, also use a multiplicity of laminates with corrugations disposed between planar elements. in regenerator-type systems,

however, all passageways confine the same fluid at a given time, the membranes alternately taking heat from one gas and giving it up to another. in prior art heat exchangers, the corrugations are utilized primarily to extend the conductive area of an element which additionally provides support, with the gases being separated by the planar elemments. Where fluids have been passed on the opposite sides of a planar separator, high effec tiveness has not been achieved and the units have been large and cumbersome.

In this first example of a practical system, substantial cost and fabrication advantages are achieved by using Company under the trademark two types of corrugated membranes 20, 22 and two types of separator membranes 24, 24'. The membranes 20, 22, 24 and 24' provide the barriers and sealing necessary to control flow of the two fluids to and from the appropriate headers, while also maintaining the fluids separate. These basic elements are used in repetitive fashion toform a multilayer laminate of the size desired. An appreciation of the general arrangement of the membranes and the fluid flow paths, best shown in the exploded view of FIG. 3, will assist in understanding the particular details of the individual membranes.

In FIG. 3, the corrugated membranes and 22 of first and second types respectively are shown as they are stacked inalternating fashion, with planar support membranes 24 and 24' being interposed between each pair of corrugated membranes 20, 22. The planar membranes 24, 24"differ only in that one incorporates an aperture to be described below. When united in the final assembly, these various membranes successively abut in intimate layered contact. Inasmuch as the structure, is equivalent at each end, only one end of the membranes has been illustrated in FIG. 3. It will be evident that the side headers may be on the same or opposite sides, or interchanged with the end headers at one or both ends, at the option of the designer. It is clear also that any number of side headers could be placed along thelongitudinal dimension of the heat exchanger, for purposes of injection or extraction of fluids at various process points. The corrugated membranes 20, 22 differ primarily in having substantially a mirror image relationship. In the following description terms such as upper and under are usedfor clarity of reference to the elements as viewed in the Figures,but it will be understood that the exchanger may be used inany attitude. I

In FIG. 3, in correspondence to FIG. 1, the first gas is directed from the end of the assembly between the first and second corrugated membrances 20, 22 on 3 each side. of the interposed support membrane 24. More-specifically, the first gas passes between the underside of the first corrugated membrane 20 and the upper side of the subjacent corrugatedmembrane 22, as viewed in FIG. 3. The second gas passes over the upper .side of the first corrugated membrane 20 and below 'a'superposed membrane '22 of the second type. This pattern of different gas flows between successive pairs of membranes 20, 22 or 22, 20 is repeated throughout the multilayer laminate. In each instance, the gas flows are on both sides of the interposed support membrane 24 or 24'.

Between the underside of a first corrugated membrane 20 and the upper side of a second corrugated membrane 22 an open flow path exists at eachend of the assembly. For the alternate corrugated membrane pairs, however, a side opening is defined by deviations along one longitudinal edge of the upper side of the first corrugated membrane 20 and corresponding edge on the underside of the second corrugated membrane 22 immediately above. The second gas flowing between these membranes is diverted transversely from the central interchange region 25 of the membrane, within a header transition region 26. This header transition region 26 is approximately rectangular in area form in this example, and communicates with all of the longitudinal passageways in the interchange region 25, as well as the side opening defined along the edges of the membranes 20, 22. e

Specific details of the configuration of a first corrrugated membrane 20 are shown in FIGS. 2 and 4. Because each membrane within the interior of the stack has a median plane but has surface portions contacting the planar membranes that are immediately above and below, it is cconvenient to refer to upper and lower reference planes as well as the median plane in describing the various parts of the structure. The upper and lower nodes of the corrugations in the central interchange region 25, for example, lie tangential to the upper reference plane and lower reference plane respectively. .In the header transition region 26, as best seen in FIG. 4, the gases are free to flow transversely because the tops of the corrugations are in effect cut off, with the lower halves or valleys of the corrugations being interconnected by webs 28 lying in the median plane. Referring again to FIG. 3, it will be appreciated that these facing mirror image surfaces of the second membrane 22 and the subjacent first membrane 20 define an internal volume constituting the header transition region. v

A system of integrally formed peripheral seals prevents leakage to the exterior or between membranes. As shown in FIGS. 2 and 4, one leg of a side channel 30 of U-shapedsection is joined by a web 32 in the upper reference plane of the membrane 20 to the closest corrugation. A side peripheral lip 34extends outward from the channel 30 to define the outer periphery of the membrane 20. The base of the channel 30and the peripheral lip 34 have substantial areal contact and seal to the corresponding surfaces of the lower and upper planar support membranes 24 and 24, respectively.

In the region of the side'openingpreviously referred to, however, the peripheral lip 34 and side channel 30 include a generally U-shaped notchor depression 36 having a long base corresponding generally to the length of the headertransition region 26,-the base lying in the median plane of the mmembrane 20,'coplanar by an integral lip 38 in the upper reference plane. A

corresponding lip 39 in the lower reference plane of the second type membrane 22 lies adjacent to the lip 38 across the end of the exchanger, so that the second gas can exit only through the side opening. The transverse end lips 38 merge into terminating end shoulders 40 which close off the corrugations. I

As best seen in FIG. 3, the planar membrane 34 between the first and second corrugated membranes 20,

22 has a coextensive area except for a generally rectangular opening about the header transition region. A generally U-shaped web 44 extends along oneside and across the end of the membranes 20, 22, to complete the seal between these membranes.

The flow path for the second gas, therefore, in the example of FIG. 4, proceeds along the upper side of the membrane 20 within the interchange region 25 and into the header transition region 26, the gas then being blocked from longitudinal flow by the transverse lips 38, 39 and flowing transversely across the median plane webs 28 toward the side opening whose bottom half is defined by the U-shaped notch 36 in the side peripheral lip 34. At the same time, there is a parallel and adjacent flow of the-second gas along the underside of the superposed second corrugated membrane 22, towardjthe sameside opening.

It will be appreciated that the gases flowing in the corrugation passageways below the median plane of the membrane are diverted upwardly at the header transition region 26 in moving transversely to pass between the median plane and the upper reference plane. No significant pressure drop results, however, because there is substantially the same cross-sectional flow area due to the absence of the'upper part of the corrugation.

The'first gas enters under the first membrane 20 and across the top of the next lower second membrane 22 by passing between the transverse end lips 38, 39. The first gas, moving in counter-current relation to the second gas, moves between but on the opposite sides of the header transition regions 26. The first gas does encounter a restricted cross-sectional flow area in this region. The restriction, however, is found in practice not to introduce a significantly discernible pressure drop.

With this arrangment, the first and second gases are maintained completely separate from each other. For the flow of second gas between a first membrane 20 and the superposed second membrane 22, the abutting peripheral side lips 34and the interposed planar membranes 24 are open only at the notches 36 defining the side opening 17 (FIGS. 1 and 2). The first gas does not communicate with any .side openings in passing between'a secondmembrane. 22 and the superposed first membrane 20,'but passes through the end apertures 14. The physically'displaced side and end openings 14, 17 may be convenientlycoupled into any desired header or'conduit system.

Apart from the mirror image relationship, the prima'ry distinction, referring now again to FIG. 2, between the first and second corrugated membranes 20, 22' is thatthe "web portion 32in the second corrugated membrane 22 is longer by the width of one corrugation, in order to maintain the desired precisely in-phase. relationship between the corrugations. From the structural standpoint both membranes 20, 22 are essentially the sameiThe sinuous corrugations substantially stiffen the thin membranes, and eliminate unsupported lengths of material. All abutting surfaces of the membranes and the adjacent planar membranes '24, 24' are bonded together for superior physical integrity, but this is not needed in all applications.

Processes of fabricating. corrugated membranes and assemblies in accordance-with the invention utilize vacuum and pressure forming of the corrugated membranes'against a mold in controlled heating and cooling bly by vacuum deposition of a thin (e.g., 0.0005

inches) prior to forming. Subunits of the assembly, comprising a corrugated membrane and a planar membrane are first assembled, by spraying the planar membrane with an adhesive dissolved in solvent and pressing the parts together, while maintaining the corrugated membrane in a matched mold. Through these steps, the membranes are maintained in precise positional relationship by alignment with positioning pins inserted in positioning holes punched in the excess trim portion. Then, after the excess material around the headers is trimmed, the subunits are built up into a complete assembly, by successive steps of adhesive bonding under pressure as previously described. Thereafter, when the assembly is built up to a desired number of layers to provide a chosen cross-sectional area for flow, the excess material beyond the peripheral lip portions is trimmed off and the side and end apertures are coupled to-associated manifolds or headers.

A completed assembly therefore appears as in the fragmentary view of FIG. 5, with the endopenings 14 being alternated in the successive layers with the side openings 17. Within the laminates, the corrugations appear in cross-section essentially asshown in FIG.'6, which is greatly enlarged in scale but corresponds closely to the actual relationships and shapes involved.

' It should be noted that the thickness of the corrguated membrane 30 does not vary substantially atthe top, bottom or sides, so that pin hole defects or ruptures of the material do not occur. In addition, the bonding ma terial 48 adheres between the corrugated membrane 20 and the planar membranes 24 and 24' and enhances the rectangularity of the corrugations when bonded, and cured under small pressure. The result is to aug-,

ment the checkerboard effect and increase the inter-' change area ratio to the volume of fluid. The achievement of a checkerboardpattern, with minute passageways, enables the system to take advantage of certain fundamental considerations of heat transfer, and to beable to achieve high efficiency. The

thermal gradient within the fluid in a-passag'eway is dependent upon the effective radius of the passageway from its center. The thermal gradient within a fluid varies in accordance with the radius, and consequently FIGS. 1 to 6 has been described in terms of a heat exchanger for operating in a given temperature range, the same conditions apply to other ranges, up to a level at which thermal degradation of the materials involved becomes of concern. Additionally, the property interchange function directly relates to a number of other applications, such as dialysis, ion exchange and oxygenation functions. In the handling of blood, for example, it is highly desirable to avoid substantial pressure gradients. turbulent flow and abrupt discontinuities. It is also highly desirable to achieve effective purification in a dialysis unit by the use of counter-current flow with a high interchange area per unit of volume. All of these conditions are achieved by structures in accordance with the present invention.

FIGS. 7 and 8 illustrate the general organization and particular details of another heat exchanger system having high efficiency and extreme compactness but also using elements that can be readily fabricated and easily assembled.

As best seen in FIG. 8, which is a greatly enlarged view of a segment of the heat exchanger, in which relative dimensions are not to scale in order to show the elcments more clearly, the basic heat exchanger elements comprise thin corrugated membranes 110, with the corrugations running parallel and lengthwise along the membrane. Of the order of fifty corrugations per inch may be employed for use in the present system, and the peak-to-valley dimension may be of the order of approximately 30 mils, with a membrane of the order of 0.002 inches in thickness. The membrane 110 itself is preferably of a thermosetting plastic of one of the types conveniently used in thermoforming such as the material sold under the trademark LEXAN. The corrugated configuration can be achieved by shaping the plastic between dies after bringing it above the plastic flow temperature. The waviness or repetitive deviation of the membrane 110 from its median plane to define gas passageways need not follow the generally sinusoidal form that is associated with the term corrugation. Instead, the membrane 110 may deviate to define grooves, or peaks'and valleys, in any desired periodic or even aperiodic fashion.

For separation of the gases, and for headering purposes, the peaks and valleys on opposite sides of the membrane 110 are affixed respectively to an intermediate thin lamination 112 and'a relatively thicker spacer 114. As may be seen in both FlGS. 7 and 8, the intermediate laminations' are disposed between a pair of membranes-110, and run the full length of the heat exchange structure. The spacers 114, however, are discon'tinuous'along the length of the heat exchanger, and the spacers 114 and intervening open volumes are utilized for several purposes.

It is convenient for'purposes of illustration and description to regard the laminated structure comprising a pair of membranes 1l0between a pair of thicker spacers 114 as a heat exchanger entity. This entity is then bounded by the thicker spacers 114, and includes an adjacent and coextensive pair of membranes 110 between which the intermediate thin lamination 112 is interposed forthe full length of the heatexchanger. The laminations 112 and the spacer 114, may as with the membranes 110, be of a suitable plastic material. Re-

, garding the thin lamination 112 as the center of the structure, the interior adjacent passageways Whose sides are bounded by the lamination 112 and the two adjacent membranes 110 provide flow paths from one end of the heat exchanger to the other. What may be termed the exterior passageways within the entity are the passageways defined between the opposite sides of the membranes 110 and the outer spacers 114. A first gas or mixture passing in one direction along the length of the heat exchanger within the interior passageways is therefore completely separated from a second gas or mixture passing along the exterior passageways. If leakage occurs due to improper bonding between the membrane and the intermediate lamination 112, there is neither a substantial temperature differential between the gases nor a mixing of unlike gases. The open volumes between the separate thicker spacers 114 provide access to all of the exterior passageways of an entity from a side of the heat exchanger. These outer open volumes communicate with the outer passageways on the lower side (as seen in FIG. 7) of the upper entity, and the upper side of the next lower heat exchanger entity. All of these open volumes communicate with common side manifolds or headers positioned at two or more regions along the heat exchanger. The necessary separation between the gas mixtures is provided by sealing surfaces 120 closing off the exterior passageways at the ends of the system, and by sealing membranes 121 closing off the interior passageways at the side header regions.

As shown in both FIGS. 7 and 8, therefore, gases in the interior passageways moving in a first direction (from right to left in FIGS. 7 and 8) pass from one end header 116 to the opposite header 118. The second gas mixture passing in the opposite flow direction is fed from one side header 122 through the heat exchanger, to the'opposite side header 124.

The greatly simplified and idealized representation of FIG. 7 therefore shows a complete heat exchange structure 92 built up of successive laminations of the basic heat exchange entities until the desired crosssectional areas for flow of the two gas mixtures are attained. It will be appreciated that the continued lamination of additional elements does not in any way change or further complicate the headering arrangement and that many hundreds of entities may be utilized. In a practical example, a heat exchanger having external dimensions of approximately 2.4 inches by 4 inches by 1.5 feet provides the needed heat transfer capacity for an individual life support system. This system operates between the breathable temperature range and the cryogenic range at approximately K, transferringapproximately BTU per minute with better than 99 percent temperature exchange efficiency, and with-a total heat exchanger volume of the order of 0.1 cubic foot. The gas passageways are linear, and as noted, a substantial cross sectional area is made available for gas flow, together with an extremely large heat transfer area. Thus, a low pressure differential (less than approximately 1 inch H O) exists within the system. This arrangement is further characterized by the fact that standardized heat exchange sections may be assembled of selected length and cross sectional areas. For greater capacity or efficiency, these may be series or parallel connected simply by appropriate interconnection between'the heat exchange headers.

The heat exchanger structure is also arranged to providean additional heat transfer function, extracting heat from the principal countercurrent gases with high efficiency. It will be appreciated that a temperature drop or rise may be augmented simply by insertion of an available high or low temperature source in close contact with the heat transfer entities, in view of the unrestricted interior volumes between the entities and headers. Apart from this obvious expedient, however, it is desirable in the present example to provide heat extraction from the counter-flowing gas mixtures without substantially impeding gas flow and by utilizing a substantial heat exchange area. To this end, low temperature gases from a boil-off manifold 125 are passed through a tortuous conduit 126 interposed between the facing sets of exterior passageways in adjacent heat exchanger entities, and between the side headers I22, 124. The gases in the exterior passageways are kept separated by thin interior laminations 127. A tertiary heat exchange is thus effected, utilizing the boil-off gases as a heat sink that acts substantially upon both counter-flowing gases through that gas flowing in the second direction within the heat exchanger, between the side headers I22, 124.

- FIGS. 9-11 illustrate a different exchanger 50, arranged to provide what may be termed in-line or end headering. As in the example of FIG. 1, the exchanger 50' comprises a multilayer laminate of first and second, substantially mirror image, corrugated membranes 52, S4 and interposed first and second planar membranes 56,58. As in the example of FIGS. 1-6 the membranes 52, 54, 56, 58 are disposed in a repetitive pattern, and

first and second gases are passed between'alternate pairs of corrugated membranes in opposite longitudinal directions. Again, the corrugated membranes 52, 54 have substantially mirror image configurations. Also, as in the previous example, the extreme upper and lower nodes of the corrugations of membrane 52 are tangent to upper and lower reference planes, respectively.

Each corrugated membrane 52 or 54, however, includes, adjacent each longitudinal end, a pair of header transition regions, these being formed integral with the membrane itself, separated longitudinally, and associated with header transition volumes on opposite sides of the membrane. Each transition volume, defined at a particular longitudinal region between the facing membrane surfaces, provides at least partially transverse gas flow, and is in communication with a different end header. Referring now to FIGS. llland 11 particularly, only the disposition of first andjsecond header transition regions 60, 62 on thefirst corrugated membrane 52 need be discussed in detail. As indicated, the first and second gas flows are respectively under and over (as viewed in FIG. 10) the membrane 52. The first header transition region '60 is closest to the longitudinal end of the membrane 52and is defined by bottom-half corrugation segdefine side-by-side sets of apertures separated down the center of the exchanger as best seen in FIG. 9. Each set communicates with a different header or other conduit (not shown). The planar membranes 56, 58 include principal apertures 86, 88 respectively which encompass the associated header transition region of the membranes, and also are open to the appropriate end aperture.

Consequently, the second gas, in flowing from the interchange region to the appropriate exchanger 50 outlet, first passes across and over the second header transition region 62. Upon entering the open volume of the first header transition region 60, gas flowing on the right side (as viewed in FIG. 11)), is blocked from the end by the shoulders 84 and the second edge sealing lip 78. This gas flow is then directed transversely across the first header transition region 60 and out between the side lip 72 and the center wall 80. The first gas, moving under the membrane 52 at the second edge sealing lip 78, passes along beneath the second header transition region 60 until reaching the second header transition region 62. At this region the first gas is dis tributed least partially transversely across all the paslimited to end regions. Side headers, communicating with their own header transition regions, may be disposed at any point along the length of the exchahger. Fluid injection and expulsion may consequentlybe carried on th'roughoutthe extent of the exchanger in acmentjs'64 interconnected by median plane webs 66.

Thus the upperhalf of the membrane 52 volume is open 'for'part ially transverse flow of the second gas in this region. The second headertransition region 62 is defined by upper-half corrugation segments 68 joined by median plane webs 70, permitting at least partially transverse flow of the first gas.

Other elements and relationships are also used in achieving the desired flows. The side lips 72 and side channels 74 run the full length of the membrane-52.

Along the transverse edge, however, a first edge sealin g lip 76 of approximately half the membrane 52 width ately above and below the first membrane 52 thus together with the interposed planar membranes'5'6, 58

cordance, for example, with the requirements of a chemical process occurring within thesystem. The invention clearly is not limited to situations in which fluids enter at one end and exit at the other.

Headers may be arranged so as to communicate with header transition regions andipassageway sets in any desired pattern. With a proper choice of passageway sets, patterns of fluid flow can be set up to allow fluids greater than two in number to be in exchange relationship with one another. In a three fluid model, for example, a fluid such as blood could exchange properties with two other fluids which for physical or chemical reasons could not be mixed together for property exchange with the blood. The headers communicating with the passagewaysthrough which the blood flows may be similar to those discussed above. The headers for the other two fluids may be arranged so as to inject each of the fluids in alternate layers of the exchanger. The resulting pattern of fluid flow then may provide for each blood flow being surrounded by two sets of passageways, each set containing one of the other two fluids.

Means of equalizing the temperature states of different flow lines, which may be used with any of the previously discussed forsm of the system, are illustrated in FIGs. 9 and 12. Referring to FIG. 9, a slot 89 extends across the 'width of the planar membrane 58 in a region in the exchange region of the exchanger 50. Separate passageways in a thin sheet-like passage defined by the corrugations of membranes 52 and planar membrane 58 are brought into communication by slot 89 as are passageways in a passage defined by the corrugated membrane 54 in the planar membrane 58 in the layer above. Both these passages contain flows of the second gas. Interpassage communication between layers is also provided by slot 89. Thus, three-dimensional physical mixing of previously separated flows of the second gas is provided by slot 89. After mixing, the gas then resumes its normal longitudinal flow.

FIG. 12 shows a fragment of heat exchanger which comprises first and second mirror image corrugated membranes 90, 94 stacked alternately with first and second planar membranes 96, 100. A first gas flows in a passage containing separate passageways defined by corrugated membrane 94 and planar membrane 96 and in separate passageways in a passage under member 90 defined by membrane 90 and planar membrane 96; a second gas flows under membrane 94 and over membrane 90 in passageways of passages defined in a similar manner with planar membrane 98. Only situations involving the first gas need be discussed.

An internal communication volume is formed by facing mirror image internal header regions 100,106 similar to the header transition region of FIG. 4. Unlike the FIG. 4 header region there are no side openings here,

longitudinal edges 102, 104 of the corrugated membranes 94, 90 being in the same plane as their continuations ouside this region. Also unlike the situation of FIG. 4, there is no transverse barrier to flow at ends of the internal header regions, gas flow being longitudinal at each end of the internal header regions.

The internal communication volume comprises an internal header permitting communication among the passageways of the first gas passages. A slot 108 in planar membrane 96 extending across the width of the membrane and longitudinally for the extent of the internal communication volume permits communication between the first gas passages. Thus, the first gas enters the internal. communication volume in spearate flow within separate passages and experiences interpassageway mixing within each passage due to the internal header regions 1'00, 106. The gas flows within each passage intermix through the slot 108. The means of physical mixing of gas flows illustrated in FIGS. 9 and 12, internal headers. and, slots, may be used separately or in combination, as shown.

Physical mixing achieved in the embodiments of FIGS. 9 and 12 makes uniform the temperature of the gases within .the regions of mixing thus minimizing the effect of anytemperature differences between flows in different passageways andpassages due to small deviations in flow arising from variations in passageway size or other causes.

Temperature equalization may also be achieved by inducing turbulence in the gas flows, for example, by means of roughening passageway interiors or introducing obstacles to straight flow. Turbulence may also be used separately or in combination with the means illustrated in FIGS. 9 and 12.

Although a number of alternative forms and modifications of systems in accordance with the invention have been described, it will be appreciated that the invention is not limited thereto, but encompasses all vari- 6 first header means communicating with first fluid passage sets between first selected pairs of membranes to pass a first fluid therealong;

second header means communicating with second fluid passage sets between second selected pairs of membranes to pass a second fluid therealong in countercurrent relationship to the first fluid, said first and second selected pairs of membranes alternating across the height of the laminate body, such that different fluids pass on opposite sides of each membrane and property transfer takes place through each membrane;

the corrugations of said membranes having a height to width ratio of approximately one, there being in excess of approximately 20 corrugations per inch and each passageway thereby being substantially encompassed by passageways for the other fluid; means laterally disposed relative to the longitudinal axis along said membranes for equalizing the property state of at least one of said fluids at least one region along said longitudinal axis. 1

2. A heat exchanger comprising:

a substantially rectangular body including a plurality of thin laminate membranes of low heat conductivity, said membranes having corrugations whose length lies parallel to a selected axis of the body, the broad faces of adjacent pairs of membranes defining substantially distinct sheet-like passages along the selected axis, the corrugations thereof providing an extended surface area and dividing the passages into substantially distinct passageways;

means feeding different ones of a pair of fluids alternately into the passages between adjacent membrane pairs, such that heat transfer between fluids takes place directly through the membranes; and,

wherein there are at least about 250 passageways per square inch in cross-section of said body,

wherein said membranethicknesses are no greater than approximately 0.005 inch, and wherein the corrugations are periodic and similar within the corrugated membranes, and disposed in an inphase relationship between adjacent membranes such that heat exchange between the fluid in a passageway and gas of the other type in adjacent passageways takes place in three dimensional and omni-directional fashion directly through the membranes,

wherein said exchanger further includes a plurality of planar support membranes interposed between each pair of corrugated membranes, and having thickness of no greater than approximately 0.020 inch,

wherein at least the central portions of said membranes are corrugated, the corrugated membranes are of thermo-formed polycarbonate resin material having corrugations of generally sinusoidal form, in which the height-to-width relationship of the corrugations average no less than approximately 1:1, wherein in addition means disposed between said corrugated membranes adhesively join abutting surfaces of adjacent support and corrugated membranes, wherein the corrugated membranes include transverse and longitudinal edge sealing members disposed in substantially mirror image relationship and joined together in selected patterns, lateral temperature equalization means comprising a plurality of thin conductive strips, each disposed within a different passage at a longitudinally spaced region therealong and conducting heat between the passageways of the passage to equalize the temperature in such passageways at said longitudinally spaced region, and wherein the heat exchanger operates from the near'cryogenic temperature range to an approximately ambient temperature range. 3. A property interchange system for fluids comprising a substantially rectangular body including'a plurality of thin membranes including central corrugated re gions whose length lies parallel to a selected axis of the body, the broad faces of. adjacent pairs of membranes defining a'set of substantially distinct passages along the selected axis, means feeding different ones of a pair of fluids along opposite sides of the individual membranes, such that transfer of properties takes place directly throug'h the membranes, and wherein said corrugations divide said passages into at least about 1000 passageways per square inch in cross-section of said body, the passageways for each fluid being directly aligned throughout the height of said body with the superposed passageways for the opposite fluid such that an approximate checkerboard distribution of passageways is achieved.

4. A property exchanger comprising a central matrix of passagewaysfor fluids-whose properties are to be in- ,terchanged, said matrix being defined-by a plurality of layers ofcorrugated membranes, the corrugations having a height-'t'o-width ratio of about 121, the membranes being less than about 0.005 inches thick and of thermoforma ble plastic material, there being approximately 50 corrugations perinch, and the corrugations in succes'sive layers being in in-phase relation;

means for feeding fluids whose properties are to be interchanged into alternate adjacent passageways in countercurrent relationship, such that a checkerboard fluid flow pattern is established in the respective passageways-throughout the matrix.

5. The invention as set forth in claim 4 above, wherein said corrugated membranes have relatively low thermal conductivity and wherein, in addition, planar support membranes are disposed between said corrugated membranes, said planar support membranes being less than approximately 0.020 inches thick, and wherein bonding means couple the opposite extremities of the ridges and grooves of the corrugations to said planar support membranes.

6. The invention as set forth in claim 5 above, wherein said property exchanger is of rectangular form, wherein said first and secondcorrugated membranes .have'coextensive rectangular outlines, and wherein said means for feeding fluids comprises extended interlayer openings having heights substantiallyequal to the corrugation heights.

7. The invention as set forth in claim 6 above, wherein selected pairs of said corrugated membranes include integral header transition regions in communication with selected ones of the inter-layer openings.

8. The invention as set forth in claim 7 above, wherein the different apertures comprise spaced apart side and end apertures.

9. The invention as set forth in claim 7 above, wherein said exchanger also includes planar support sheets between adjacent pairs of membranes, and wherein said membranes also include integral longitudinal edge sealing members, definingside apertures between selected pairs of membranes, and integral transverse edge sealing members defining end apertures between other selected pairs of membranes.

v10. A heat exchanger comprising:

a plurality of thermoformed sheets of first and second types;

a plurality of support sheets;

said therrnoformed sheets and support sheets being stacked in multilayer laminate relation, said thermoformed sheets being alternated between said first and second types, said support sheets being interposed between each adjacent pair of thermoformed sheets, all said sheets being substantially coextensive and rectangular in plan;

said thermoformedsheets each having a central corrugated regionwith corrugations running lengthwise, said corrugations having selected heights and surfaces, saidv side sealing surfaces comprising a longitudinal side lip and an adjacent channel, and said end sealing surfaces comprising a transverse end lip and terminating shoulders in said corrugations, said side sealing surfaces further including shaped aperture-defining surfaces in communication with the interior header transition regions, the corrugations in the sheets of the first and second types having like periodicity and being directly in phase; I

first inlet and outlet header means communicating with said transition regions;

second inlet and outlet header means communicating with the lengthwise ends of the laminate.

11. The invention as set forth in claim 10 above, wherein said support sheets comprise planar membranes, and both said thermoformed and said support sheets are of thin plastic material of relatively low heat conductivity, wherein said first and second types of thermoformed sheets have substantially mirror image configurations with the web portions of said header transition regions in adjacent ones of each thermoformed sheets being in facingrelation, wherein aperture-defining surfaces of said side sealing surfaces are between first alternate pairs of said thermoformed sheets, to provide a first set of apertures along the side of said exchanger, and wherein the end sealing surfaces seal the ends of said first alternate pairs and are open between the remaining alternate pairs of said thermoformed sheets, to provide a second set of apertures along the end of said exchanger, and spaced apart from said first set of apertures.

12. A heat exchanger for operation between the near cryogenic range and an ambient temperature range comprising:

a plurality of thermoformed sheets of first and second types having substantially mirror image relationships, said thermoformed sheets each having a central corrugated region with corrugations running lengthwise relative to the longitudinal exchanger axis, said corrugations varying from the median plane of the sheet in generally sinusoidal fashion to define ridge nodes tangential to an upper reference plane and groove nodes tangential to a lower reference plane, said upper and lower reference planes and the sinusoidal variations of said corrugations providing a height-to-width ratio for said corrugations of approximately 1:1, there being in excess of approximately 50 corrugations per inch, and said thermoformed sheets being of approximately 0.001 inch in thickness and of polycarbonate resin material, said sheets also each including header transition regions in the form of a corrugated area comprising unidirectionally varying half-corrugation segments and planar webs joining said halfcorrugation segments at approximately the median plane, said thermoformed sheets also including peripheral sealing means extending thereabout and including side channel means having a base lying in one of the reference planes, and a side peripheral lip lying in the other of the reference planes, said side channel means and side peripheral lip including a generally U-shaped'notch having an extended base lying approximately in the median plane adjacent to and communicating with the different header transition regions, said sheets further including edge peripheral lips at each lengthwise end transverse to the longitudinal axis, said edge peripheral lips lying in one of said reference planes, said sheets of first and second types being substantially coextensive and rectangular in plan;

a plurality of planar support sheets of thin plastic material coextensive with said thermoformed sheets, and including areal apertures adjacent each end corresponding to the outline of the header transition regions and including an opening corresponding to the U-shaped notch portions;

said thermoformed sheets and said planar support sheets being stacked in multilayer laminate relation, said thermoformed sheets being alternated between said first and second types, with the U- shaped notch portions facing to define the peripheries of side apertures communicating with interior header transition volumes defined by facing header transition regions, said support sheets being interposed between each adjacent pair of thermoformed sheets, with the side openings therein corresponding to the side apertures defined by said U- shaped notch portions;

adhesive means disposed between said thermoformed sheets and said support sheets and bonding corrugation nodes of said thermoformed sheets to the facing adjacent support sheet along the length of the corrugations;

first inlet and outlet header means disposed along the sides of said heat exchanger, and each communicating with the side openings defined by the exchanger;

and second inlet and outlet header means disposed adjacent to the longitudinal ends of the exchanger and each communicating with the set of side apertures between adjacent alternate pairs of thermoformed sheets within the exchanger at the corresponding end of the exchanger.

13. The invention as set forth in claim 12 above wherein one type of thermoformed sheet includes at least one additional corrugation therein relative to the other type of thermoformed sheet, wherein the corrugations in said thermoformed sheets are disposed in inphase relation, and wherein said thermoformed sheets and bonding means have substantially like thermal coefficients of expansion.

232 3 UNITED STATES PATIENT OFFICE CERTIFICATE OF CORRECTION Patent Ko- 3.s47211 Dated November 12 1-974 V Inventor-(s) Halbert Fischel and Anthony Dichi ro It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 15, "otherwide" read "otherwise"; line 33, the formula read:

Column 2 line 54, "mmem-" read .--mem-.- Column 3,'- line 62 "cpmbinations" read --combinat ions--. Column 4, line 25, "end" read --ends--; line 44, "Diifferent" read --Differ'ent--. Column 6, line 19; "realtionship" read --relationship line 52, ."corrguated" read --corrugated-"-. Column 8, line 28, "suffficiently" read "sufficientlyline 62, "elemments" read --elements--. Column 9, line '63, "area" read --areal--. Column 10, line 1, "corrru-" read --corruline 6, "cconvenient" read --convenient--;. line 38, "mmembrane" read --membrane--; line 40, "supernosed" read --superposed--.

Column ll, line 25, "arrangment" read "arrangement".

Column 12, line 26 "corrguated" read --corrugat ed-. Column 15, line 61, "tion' read --tions--. Column 16, line 63, "forsm" read --fo rms--. 'Column 17, line 11, after "of" and before "heat" insert --a--; line. 40, "spearate" read --separate--. Column 18, line 64, "thickness" read .--thicknesses"'.f Column 19, line 65, "comprises" read --comprise--. v

Signed and. sealed this 13th d-ay' of May 1975.

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Arresting Officer and Trademarks

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U.S. Classification165/166, 165/70, 165/DIG.389, 428/186
International ClassificationF28F21/06, B01D53/22, F28D9/00
Cooperative ClassificationB01D53/22, F28F2275/025, B01D2313/38, B01D63/082, F28F3/025, B01D2313/04, F28F21/065, F28D9/0025, B01D69/00, Y10S165/389
European ClassificationF28F3/02D, B01D53/22, F28F21/06C, F28D9/00E, B01D63/08D, B01D69/00