Title of Invention	A HEAT EXCHANGE ELEMENT AND A METHOD OF MANUFACTURING A HEAT EXCHANGER
Abstract	The present invention relates to a heat exchange element comprising a formable laminate (105) of a metal layer and a heat-seal layer, the laminate (105) being provided on both surfaces with a plurality of generally corrugated fins (106, 107) having a series of troughs, the fins (106, 107) being connected at the troughs under heat and pressure in heat conducting relationship with the laminate (105) to increase the effective surface area thereof, the laminate (105) being sealed under heat and pressure to itself or to another similar laminate to form a flow channel for a heat exchange medium the flow channel having fins on both an internal surface and an external surface, the heat exchange element further comprises a water-retaining layer (204 provided on the fins. The present invention also relates to a method of manufacturing a heat exchanger.

Title of Invention

A HEAT EXCHANGE ELEMENT AND A METHOD OF MANUFACTURING A HEAT EXCHANGER

Abstract

The present invention relates to a heat exchange element comprising a formable laminate (105) of a metal layer and a heat-seal layer, the laminate (105) being provided on both surfaces with a plurality of generally corrugated fins (106, 107) having a series of troughs, the fins (106, 107) being connected at the troughs under heat and pressure in heat conducting relationship with the laminate (105) to increase the effective surface area thereof, the laminate (105) being sealed under heat and pressure to itself or to another similar laminate to form a flow channel for a heat exchange medium the flow channel having fins on both an internal surface and an external surface, the heat exchange element further comprises a water-retaining layer (204 provided on the fins. The present invention also relates to a method of manufacturing a heat exchanger.

Full Text	HEAT EXCHANGER AND METHOD OF MANUFACTURE THEREOF The present invention relates to a beat exchange element and a foimable laminate for the manufacture of such a heat exchange element in particular for use in heat exchange between two fluid flows such as in an evaporative type heat exchanger. The invention also relates to a method of manufacturing such a beat exchange element, Heat exchai^sTs for heat exchange "between two.fiuid streams are generally known in which a dividing wall separates the two fluid streams. In general, it is an objective of many such devices to increase the surface area of the dividing wall to increase the effective heat transfer between the two fluids. Generally, the wall will be thin to maximise the thermal gradient and in such cases, the conductivity, of the wall material is not critical if its total area is sufficiently large, A device is known from JEPQ2ZZQSS* ^sh »s_# a coni^t^jsh^tlo^oduc^Aii^j^hange filament, It haE also been suggested to uss metal sheet formed into U-bends to form a dividing wall. Such a device is known from US4384611. Conventional metal heat exchangers have used various techniques to join parts of the exchanger together. Typical joining techniques include crimping, welding brazing' and adhesives. The use of such techniques has been found to have certain disadvantages in terms of cost, integrity-and complexity of the joini and the joining procedure. Particularly in cases where a wall is provided" with additional 5ns to achieve the required heat transfer, Hie joining of the fins to the wall is difficult In low temperature applications such as domestic heat recovery and dew point coolers, plastics material and the like has frequently been adopted since it is relatively cheap to produce and easy to form into the desired .shapes. A dew-point cooler is a particular form of evaporative heat exchanger, which attempts to bring down the temperature of a product air stream to as close to the dew point temperature as'possible. For air at a given absolute humidity, the dew point is the . temperature ai whicLthe air reaches a relative humidity of 100%, at which point it is ' saturated and can absorb no further moisture, The heat is removed from the product air stream by evaporation of a quantity of liquid into another working air stream. Such a process is theoretically extremely efficient and requires no compressor, as is the case for conventional refrigeration cycles. Many attempts have been made to realise such cycles but practical considerations have caused great difficulties in approaching the dew point over most temperature ranges, An indirect evaporative gas cooler is known from US4976113 to Gershuni et al where the product and working air streams are in counter flow. Other devices axe known which operate substantially in cross flow such as the device kaown from XJS2003/0033S21 to Maisotsenko et'aL The teachings of the present invention may thus be applied to devices according to both of the above disclosures, the contents of which are hereby incorporated by reference in their-entirety. In the following, the term dew-point cooler will be used to refer to devices that cool a fluid to at or near its initial dew point by heat transfer to cause evaporation of a liquid into a working fluid operating at or near its saturation point Particularly in the case of dew-point coolers, it has been found desirable to use fins attached to a * dividing wall to achieve the necessary heat trax^fajmte conditions where the temperature gradient across the wall is smalL According to the present invention there is provided a heat exchange element comprising a formable laminate of a metal layer and a heat-seal layer, the laminate being sealed under heat and pressure to itself or to another similar laminate to form a flow channel for a heat exchange medium. By providing such a formable laminate, complex shapes such as convolutions,-fins and the like may be easily produced that are fluid tight ensure good heat transmission and are robust According to an advantageous embodiment of the. invention, the metal layer, comprises aluminium, in particular soft annealed aluminium, which can be easily plastically deformed. Other similar metals may also be used but soft aunealed aluminium hzs been found particularly cheap and easy to work. In particular, by choosing a marerial that if relatively inelastic, deformation of the laminate is unlikely to cause separation of the heat-sealed sections. Such forces may alternatively or additionally be reduced by choosing a relatively tnin metal layer in the form of a foil. Preferably the metal layer may iave a thickness of between 25 microns and 120 microns, more preferably around 70 microns. In a partial embodiment of the invention, the heat-seal layer is substantially coextensive with the metal layer and may-be-applied by coating onto either one or both sides of the metal layer* Depending upon fee nature and intended use of the heat exchange element, the laminate may further comprise additional layers. A layer ofprimer or ike like may be required between the metal layer and the heat-seal layer to improve bonding or to provide protection against corrosion Such primer may also be pigmented ox otherwise coloured to improve the aesthetic effect or to optimise heat transfer. Furthermore, for use as an evaporative heat exchanger, humidifier or for improved wicking. a water-retaining or water-transporting layer may be provided over some or afl of the surfaces of the laminate. This layer may be adhered by means of the heat-. seal layer or otherwise. Acoardmg to a first heat exchanger e^stzuctim, theJantinate.may be formed into a ....... convoluted shape or corrugated to form a plurality of fins thereby.providing an increased surface area. In this context, an increased surface area is understood to mean an increased surface area for a given volume. According to an alternative heat' exchanger construction the laminate may be provided on one or both surfaces with a plurality of fins or other constructions in heat conducting relationship with the laminate to increase the surface area thereof, * By the advantageous use of a metal/heat-seal laminate as described above for these fins, they may also be easily connected by a combination of heat and-pressure, The fins may further be provided with other surface area increasing elements or elements for breaking up the boundary layers of the fluids used. Such elements may take the form of lounes or openings in the fins. A convenient shape for the flow channel is that of an elongate flat tube of generally rectangular cross-section. For use in a heat exchange unit, a number of such flow ■ channels may be located side by side in a suitable housing whereby a primary fluid can flow through the tube and a secondary fluid can flow over the outside thereof. The rabe may comprise a single laminate folded on itself and joined at the edges along a single elongate seam. Alternatively, it may be formed of two halves from first and second laminate portions sealed to one another along respective edges. According to a particularly advantageous application of the invention the flat tube comprises fin sections on both the interior,and exterior surfaces of the laminate, The fin sections on the interior surfaces 'support against one another and help rnnmhtm the mechanical rigidity of the tube. This is a particular advantage of the construction which allows the use of such extremely thin gauge material, For use as a dew point cooler, at least the fin sections on the exterior surfaces are provided with water retaining layers. The interior of the tube may thus serve as a primary diy flow channel and the exterior of the tube may form part of the secondary wet flow channel. The invention alsorelates to a method of manufacturing a heat exchanger comprising. * providing a plastically defonnable first metal- laminate providing a plastically deifarmafale second laminate: ^plastically forming thefcst i»-m™»** i^to a generally corrugated shape having a series of troughs;, connecting the first' laminate to the second laminate at the series of troughs to form a heat-transmitting wall with heat-conducting fins; and sealing the second igTnrnate to itself or to another similar laminate to form a flow channel Preferably, either the first or the second laminate comprises a heat-sealable layer and # the first and second laminates are connected together by beat-sealing at a first temperature. Both the first and second laminates are preferably laminates as described above. In which case the second'laminae may comprises a heat-sealable layer differing from the first laminate so that the second laminate can be sealed to itself or to another similar laminate by heat sealing at a second temperature' lower than the first temperature. In this manner, the fins may first be connected to the second laminate prior to forming the second laminate into a flow channel The method may further comprise the step of dividing the first laminate into sections prior to connecting'it to the second laminate. It has been' found, that individual fin sections separate from one another can prevent heat conduction along the heat exchanger and can also help to encourage turbulent flow by .breaking up 1he boundary layer. His may also "be achieved by forming louvres in the first laminate prior to connecting it to the second laminate. ' According to a particular embodiment of the invention, the method further- comprises forming a water retaining layer on a first surface of the first laminate, wherein the second surface of the first laminate is- connected to the second laminate. The heat exchange element produced in this way may ideally be used in a dew point cooler, for- humidifying dry air or in a heat recovery device. The invention also relates to a method of manufacturing a heat exchanger, comprising: two sets of medium through-flow channels placed mutually interlaced, which sets of channels form respectively a primary medium circuit and a secondary medium circc&ijg^^ can flow which are physically separated and in heat-exchanging contact; heat-conducting walls separating said channels; and a housing in which the walls bounding the channels are accommodated, to which housing connect at least one inlet and two outlets for the two sets of channels. The method comprises: * * (a) providing a plastically deforrnable plate, for instance of a plastic or a metal such as copper or aluminium; (b)* providing at least one metal strip moulded into a general wave shape, fox instance of copper or alitmirriiiTnj which can serve as a row of fins; (c) plastically deforming the plate such that it acquires an edge zone with which it can be connected to a similar plate; (d) prior to or after step (c), connecting the strip to the plastically deforrnable plate by means of the outermost surfaces of the wave shape directed toward the strip, such that a heat-conducting wall with heat-conducting fins is created; (e) repeating steps (a), (b)s (c) and (d) a number of times to obtain a number of heat-conducting walls with fins; (f) connecting these walls at least in twos to each other using the edge zones according to step (c) such that a chosen number of such walls is placed in mutually parallel relation; and (g) accommodating these walls in the housing. In this way there is provided a method of manufectnring a heat exchanger which can he performed very inexpensively, rapidly and with great reliability, so that the heat exchangers can be manufactured, also in mass production, at considerably reduced cost compared to the prior art The plastic -deformation can be carried out in any appropriate manner, wherein the choice is determined parity by die nature and type of ihe applied material. Use can for instance be made of pressing, themio-foxming, vacuum-forming, injection moulding. Patticuto5jr^rQ.:&^]^or^ case ti3at"55feinimn is applied, t£e method cam advantageously be embodied such that the plastic deformation according to step (c) takes place in cold state. The method can for instance be embodied such that the plate and/or the fins are provided prior to step (d) with an adhesive layer and that step (d) is performed by pressing the plate and the fins against each other at least at the position of the contact surfaces, optionally while heating, •" * A simple press tool can for instance be used for this pttcpose which provides the necessary adhesion through pressure and optional heating for a certain time. It must be ensured that the heat, resistance represented by the adhesive layer lies below a predetermined value. This means that the adhesive layer, given its heat-conducting properties, may have only a limited thickness after'forming of the connection. Particular advantages are provided by the method in which the adhesive layer substantially covers fee plate end/or the fins completely and protects them against corrosion. The adhesive layer hereby fulfils an adhesive and an anti-corrosive function. The method can for instance be embodied such that the adhesive layer is applied as foil. . - Particularly when a thermoplastic plastic is applied as material for the plastically ■ defoxmsfcie plate, the method can be embodied such that the adhesive .layer is formed together with the pkte by co-extrusion into a laminated co-extmdate. An important variant of the method has the special feature that the plate and/or the fins consist of a materia] to which the adhesive layer adheres with difficulty, for instance ahramiuEL and that the part of the adhesive layer directed to the aluminium is adhered thereto via a layer of primer. The primer layer provides an .excellent" adhesion of the adhesive' layer to the duminium. Without the primer this adhesion would leave something to be desired, ^ .„_„. ..i which cannot be permittedin respect of the reliabflit^ of the heat exchanger. The latter specified method can advantageously be embodied such that the primer has a chosen colour, pattern anaVor-tertae, and that the adhesive layer is transparent. The primer can for instance be gold-coloured, A heat exchanger pkte hereby acquires an extremely attractive appearance, Colour, pattern and/or texture can also serve as coding for heat exchanger components, with an eye to ready identification of the category within the selection of technical specifications. Li yet another embodiment the method has the special feature that the primer and/or the coating contain silver, such that the adhesive layer has an anti-microbial action. This embodiment has the ad^'antage of not requiring any specific provisions in respect of for instance bacterial contamination. According to yet another aspect of the invention, the method has the special feature thai finished pktss wifii fins ere adhered to each other in alternate pairs using edge zones, and that a number of thus formed pairs Hie stacked onto each other prior to step (g). The finished plates or walls can for instance be identical. The latter embodiment of the method can particularly take place such that adhesion takes place "by providing the plates in advance with the adhesive layer and pressing the edge zones against each other, optionally while heating. This method can also be performed in exceptionally simple, inexpensive and rapid manner. This latter described method can further be embodied such that the plates are adhered to each other via a sheet which is placed beforehand therebetween and which is provided on both sides with an adhesive layer, and that the respective edge zones directed toward each other and preferably also the respective outer surfaces of the fins directed toward each ofeer are thus adhered to each other by being pressed together, optionally while applying heat for instance by feeding through hot air, In one embodiment of the heat exchanger, at least the fins in the secondary medium through-ficrw circuit are provided with a hydrophilic and porous or fibrous coating, consisting for instance of a microporous Portland cement, which layer is kept wet by j^tcring^neans fonning p^.of^^h^t.excha^CT.5uch.kt3iat3 through'evaporation therefrom by the secondary medium, respectively the layer, the secondaxy fins, the wall the primary fins and finally the primary medium axe cooled, which layer has a small thickness such that in wet state it has a sufficiently low heat resistance such that the heat exchanger can operate as dew point cooler. In order to obtain a good mechanical strength, cotrosion resistance and heat transfer in combination with relatively low cost, the heat exchanger can have 'the special feature that the sheet is embodied as a lamioate3 comprising a metal inner layer which is coated on both sides with plastic outer layers. The' inner layer can for instance consist of aluminium v.ith a thickness in the oider of magnitude of 25 fim. The plastic outer layers, which can consist of any suitable plastic, can for instance " also have a thickness in the order of magnitude of 25 pm or less. With such a small thickness the hsat resistance represented by the plastic outer layers is negligible. According to another aspect of the invention, the heat exchanger can have the special feature that two sheets are each folded into the form of a rectangular wave shape, wherein the TWO wave shapes have equal- pitch, and are positioned mutually interlaced "with a relative longirudinal orientation of 90°, Embodiments of the invention will now be described by way of example only "with, reference ID the annexed drawings, in which; Fig. la shows a perspective view of a plastic sheet moulded by thermo-fhrming. on both sides of which heat-conducting fins are arranged; Fig. lb shows the phase in which the sheet is folded along the two fold'lines * such thai the walls are moved toward each other, Fig. Ic shows the end position in which the two walls are positioned fixedly in mutually parallel relation; Fig, 2a, 2b and 2c show views corresponding to respectively fig. la, lb and 1 c of an embodiment with the same width but of greater length; Fig. 3a shows a perspective view of a sheet having in the zoaae of the walls rectangular perforations for passage of fins; Fig. 5b shows a perspective view of a heat-conducting wall, on both sides of which fins are arranged which fir into the perforations of the sheet according to Fig. Fag. 4 shows a pardy broken-away perspective view of a heat exchanger, wherein the housing is omitted for the sake of clarify; Fig. 5a and 5b show perspective views from different sides of a dew point .cooler, Fig. 6 is a perspective view of a pact of a dew point cooler; Fig. 7 shows a view corresponding with Fig. 4 of a variant; Fig. 8 is a-cut-away perspective view of an alternative of the embodiment of Fie, 3a and 2b: Fig. 9 shows a "schematic perspective view of a heat exchanger constructed from two sheets folded in mutually interlaced manner, . Fig. 10a shows a very schematic view of a compression mould for modelling a plate into a heat-exchanging wall; Fig. 10b shows a very schematic -view of the arranging of strips of fins on either side cf me wall; • Fig. 10c shows the heat-exchanging wall having heat-conducting fins arranged thereon; Fig, lOd shows the stacking of four such walls'with fins in order to form the interior of a hear exchanger according to the invention; Fig. 11 shows an alternative, wherein the heat-exchanging walls and also 5ns are adhered to each other by means of an adhesive foil; Fig.' 12 is a perspective, view of a practical embodiment of a strip of fins: and Fig. 13 is a perspective view of a moulded wall, Fig. 1 shows a moulded sheet 1 consisting of a thin foil-like material of for instance polystyrene, PVC or ?ET. It is possible using such materials to apply a relatively small wall thickness, .for instance in the order of 0.1 mm. Inexpensive production wife a short throughput time is possible with for instance ftenno-forming. Sheet 1 is provided on both sides with schematically indicated packets of fins which, in Fig. 1 ? are designated 2 for the primary medium through-flow circuit and 3 for the secondary medium through-flow circuit, Attention is drawn to tbe fact that the fins 2, 3 are shown very schematically. They consist in this embodiment of strips of limited length moulded in zigzag form in the longitudinal direction, i.e. the medium flow direction. This aspect is however not significant for the present invention.' Deflector rfons 4 axe formed in sheet 1 for deflecting tie relevant medium flow. This aspect will be further elucidated with reference to Fig. 4, . Sheet I further has a number of condensation outlets in the form of funnel-shaped structures wiih triangular, intermediate forms 5 for draining water. This may for instance be condensation water: although in the case of operation of the heat exchanger as dew point cooler it may also be excess water added to the secondary medium circuit As will be apparent from comparing the three successive steps of Fig. la, lb and lc, the walls S, 5 are folded toward each other along hinge lines 6 and 7 to form the folded-up situation shown in Fig. lc, The construction obtained here is an element of a packet of such elements together forming a heat exchanger. Reference can for instance be made in this respect to Fig. 4, 5a, 6 and 7. The heat exchanger can also serve fox instance as a dew point cooler. As described above, aa effective, for instance intermittent watering of the beat-exchanging surface in the secondary medium circuit must in that case be ensured. This implies that 5ns 3 must be provided with a coating which has a hydrophilic character and which exhibits an open porosity ox fibrous structure such that a rapid distribution of water or other evaporable liquid can occur through capillary suction' The manner in which ' this watering takes place falls outside the scope of the present invention and will therefore not be discussed further. Fig. 5a shows this watering symbolically. During this production phase, in which the fins are already arranged, sheet 1 according to Fig. la is treated by at least wetting the fins, in any case on their outer side, and by then applying a mortar in powder form to the fins by atomisatioa The thus obtained coating of microporous Portland cement can have a thickness in the order of for instance 50 \im. The process in question is highly controllable and produces a hydrophilic and water-buffering coating. The fins 2 in the primary circuit are not provided with such a coatmg,,_sjncejpni evaporation occurs in the primary circuit The free edges 10 of wall parts 8, 9 are earned toward each other as according to Fig> lb and connected to each oiher as according to Fig, lc, for instance by glueing, welding or the like. It will be apparent that a sealing primary medium channel is obtained in this manner. For sealing of a secondary medium channel in which the fins 3 extend other pnmsions are necessary, in particular sealing means co-acting with a housing, Fig. 2a, 2b and 2c show structures the same as those according to Fig. la, lb and lc, with the understanding that the length in the medium flow direction is greater, It is noted here thai the medium flow direction extends in the direction of the drawn lines of 5ns 3. The sheet is designated in Fig. 2 with reference numeral 11. Fig. 3 a shows a sheet 21, the general structure of which corresponds with that of sheet I of Fig. I. Sheet 21 is not however provided with fins 2, 3, but is provided instead with two perforations 22, 23, Into these perforations nt fins 24 which are arranged on a hsat-conducting wall 25, for instance by welding or soldering. The fins as well as the wall can be manufactured from for instance copper. Fins designated with 26 are likewise situated on the otiier side of the wall. The respective "blocks of fins fit into perforations 22, 23. The heat-conducting wall part 25 is adhered sealingly to plate 21, for instance by glueing. lie finally obtained structure has the same ejcfcernal structure as shown in Fig. la. The structure differs from that in Fig. la in that the piste or wall part 25 extends on the underside of sheet 1. It is of course necessary to take into account that wall part 25 must "bend readily along hinge lints It is further noted in respect of Fig. 3b that fins 26 are shown with contour line6 only. for the sake of clarity. They are of course not visible in this perspective view,' Fig. 4 shows the interior 31s i.e. without a housing or casing, of a dew point cooler with the fins omitted A number of units 32, comparable to the unit of Fig. 1c, are placed in a base 33. As described briefly above, water can be drained via water outlets '34 via an opening 35 in base 33. . "Fig. 5aT3i33b each'sEow a dew point cooler 41 with two units 42,43. As shown in Fig, 5b, a primary medium flow 44 is admitted to the inside from the one side. On the other side a part of this primary flow, designated 45, exits to the outside. Another part ,46 is reversed as partial flow' and passes over die watered fins 47. The thus wetted secondary airflow 48 is deflected upward by deflection dams 49 and leaves unit 41 from the top side. Fig. 6 shows a base in die form of a tray 51 in which a number of units 52 arc disposed. Use is also made in this embodiment of deflection dams 53. Fins are not drawn. The openings between funnels 54 give access to the bottom of the tray for water drainage via outlet opening 55. Fig. 7 shows a structure related to that of Fig. 4» Units 61 have a differently moulded drainage provision. Pig. 8 shows two units 71 based on the principles elucidated with reference to Fig. 3a and 3b, A copper plate or foil 72 bears on both rides fins which are ordered in respective blocte 73; 74; 75. Identical fins are situated on the non-visible side. These St as according to an arrow 176 through respective openings 76, 775 78 in preformed sheet 79. Similarly to the structure shown in Fig. 1 c, the walls are folded in the dipper hinge zone into a mutually parallel relation, whereafter the free edges 10 are adhered to each othsr. At variance with the structure of Fig. 1> use is made in this embodiment of a single hinge line 80 which is embodied as a score with a substantially rigid zone on either side such that, also due to the correspondingly formed co-acting lower wall parts 839 84, the final mutual distance of walls 81, 82 corresponds with the chosen distance. ■ This distance can for instance be chosen such that the fins press against each other. ' By means of a suitable pressing construction it is possible to hereby achieve that units 71 (of which there can be more "than two) form a mechanically substantially rigid packet The fins thus make an essential contribution toward.the mechanical strength of the finally obtained heat exchanger. Fig. 9 shows an alternative embodiment of the heat exchanger according to the .-iftY5ffl?S^Heat exchanger 90comprises two sheets 91, 92jtfhich are each folded in the form of respective rectangular wave shapes of identical pitch or wavelength. Sheets 91, 92 are positioned mutually interlaced with a relative longitudinal orientation of 90c. The manifolds necessary for feeding and discharging the primary and secondary medium flow are omitted from this schematic drawing. Heat exchanger 90 comprises fins, all designated with 93. As in the embodiment of Fig,- 3,-fa the embodiment of Fig. 9 the heat exchanger 90 can advantageously be embodied such that fins 93 are in heat-exchanging contact with each other via respective holes in sheets 91,92, for instance via heat-conducting carrier plates 94. This avoids toe heat resistance via-the two sheets 91, 92 becoming disturbingly manifest at the location of the fins. Fins 93 and carrier plates 94 must in that case be in the most direct possible thermal contact with each other, for instance by means of a heat-conducting glue layer (for instance a thin pressure-sensitive or thermally activated plastic glue layer), a welding operation, a soldering operation, a mechanical coupling or the like. Fig, 10a shows an opened mould consisting of a lower mould part 101 and an upper mould part 102 which corresponds therewith and which can be closed as according to arrow 1C3 to cause plastic cold deformation of an aluminium plate 104, which is covered on both sides with a glue layer activated "by heat and pressure, For use with aluminiucL a PVC/poiyacrylate based adhesive has been found to be suitable. This may be provided with a thickness of about 3 microns, preferably in combinarioi: with a P VC primer in the foim of a heat-seal lacquer of about 2 micron thickness. Kg. 10b shows that a strip of fins 106,107 is positioned from both sides on the thus formed, moulded heat-exchanging wall 105 and then pressed on as according to arrows 108,109 respectively, It is noted that the lower surfaces 120 of fins 107 and the upper surfaces 110 of fins 106 are preferably also provided with a glue layer activated by heat and pressure, 'tfbich may be of the same type as that applied to the. plate 104. Alternatively, it may be selected to. have a higher melting temperature thereby preventing loosening of the fins during heat-sealing of the pkte 104. Fig.. 10c shows wall-105 with the strips of fins 106,107 arranged thereon. Fig. lOd shows the manner in which a 'number of identical heat-exchanging walls 105 with fins 106, 107 arranged thereon can be coupled'to each other to form the interior of a heat exchange^ which must later also be placed in a suitable housing having inlets and outlets fear the primary and the secondary medium, as well as associated manifolds, whereby said inlets and outlets can be coupled in the correct manner to the diverse channels in heat exchanger unit 111 of Fig. lOd. In Fig. lOd it is also noted how the two sets of fins 107 support against one another to provide a reinforced structure. A foil 121 may be provided between the fins 107 in Fig. lOd to increase the stability of iht structure. Fig. 11 shows an alternative in which an adhesive foil 112 is placed between two finished walls with fins, whereafter, by suitably pressing together the edge zones 113 with foil 112 therebetween as according to arrows 114 and by pressing the fins 107 against each other with foil 112 therebetween as according to arrows 115. a mechanically very strong structure is created which, owing to the tensively strong connection between walls 105 via adhesive foil 112, is able to withstand an increased internal pressure in the relevant heat-exchanging medium. A very effective manner of causing the adhesive fofl 112 to melt under some pressure is to feed hot air through the space occupied by fins 107. The desired softening and, after cooling, the desired adliesion is hereby realized in a short time* The adhesive foil layer 112 is manufactured from a plastic having a relatively low softening and melting point - -compared with that of the heat-seal adhesive on the fins. While Figs. 10a - 11 show flow channels being formed by joining two like laminate portions. It is noted that-a construction by folding a single laminate e.g. provided with fins on "both surfaces may also be achieved in a similar maimer to that shown in Figs. 1-3. Fig. 12 shows in greater detail a strip of fins 107, for instance of copper or aluminium, as shown schematically in earlier figures. The strip can for instance be embodied as a laminate consisting of a base layer of copper or aluminium, a layer of primer applied thereto and an anti-corrosive, adhesive layer applied thereover, activated by heat and pressure for coupling of the strip of fins 107 to a wall 105. The laminate is also provided with a hguid retaining layer 204 on an upper surface thereof. The liquid renaming layer 204 is formed from a fibrous non-woven material. Although reference is made to a liquid retaining layer, it is clearly understood that the layer is in fact a liquid retaining and releasing layer. The layer 204 is schematically illustrated to have a very open structure such that the metal laminate can be clearly seen through fee spaces between the fibres of the layer 204. An exemplary material for forming the water retaining layer is a 20gfcn2 polyester/viscose 50/50 blend available from Lantor B.V. in The Netherlands. Another exemplary material is a 30g/m2 polyamide coated polyester fibre available • under the name CoIbackTM from Colbond K V. in The Netherlands. Other materials having similar properties including synthetic and natural fibres such as wool may also be used. Where necessary, the liquid retaining layer may be coated or otherwise treated to provide anti bacterial or other anti fouling properties. The liouid retaining layer 204 msy be adhesively attached TO the metal layer over 1he entire area of the laminate 1. For use with aluminium and Lantor fibres as mentioned above, a 2 micron layer of two-component polyursthane adhesive has been found to provide excellent results. When present as such a fti& layer, its effect on heat transfer is negligible. Other liquid retaining layers such as Portland cement as mentioned above may also be used-According to Fig. 12 The strip comprises individual fins 216 each provided with louvres 218 in the form of elongate slots penetrating through the laminate (only the louvres on the first fin are shown). The louvres 218 are arranged in groups. A first group 220 serves to direct flow into the surface, while a second group 222 directs flow out of the surface, Thus> some of the aii flowing along the fins 216 in the direction of arrow A will "be directed through the laminate towards the lower second surface. Air following the direction of arrow B will be directed outwardly by the second group of louvres. In this way, the air alternately flows oyer the first surface, where it can receive moisture by evaporation from the liqjiid retaining layer. followed by the second surface where it can receive direct thermal energy to raise its temperature. hi addition to, their function in directing flow between the surfaces of the fins 216, louvres 218 also serve to break up the boundary layers that may develop as ah flows along the surfaces. Other break np dements may be provided in addition or instead of the louvres 21S. Furthermore, vrhile the fins 216 of Fig. 12 are straight, curvilinear or zig-zag fins may also be produced. It-is believed that such fin shapes are advantageous in breaking up the boundary layers that develop in flow along the fins, since each time the fin changes direction, turbulent flow is re-established. Various cross-sectional shapes are also possible for the fins, including corrugations of square, trapezoidal, rectangular, bell and sbf wave shapes. In particular, it is noted that the base or trough 208 of the fin should preferably be as flat as possible with sharp comers in order to macdmise the area of heat transfer to the plate 105. In addfton to louvres 21S, fins 216 are provided with conduction bridges 224, These L bridges 224 are in the fonn of cuts through the laminate over substantially the whole height of the fin 216. They serve to prevent unwanted transport of heat along the fins 216 in the direction of the air flow. The strip of fins 107 is preferably formed using standard corrugation techniques. An appropriate width roll of prepared laminate may be fed through a pair of corrugated rollers which can form the fins 216, louvres 218 and heat bridges 224 in a single pass. The resulting product may then be cut into suitably sized strips of fins 107 for further processing. Finally. Fig. 13 shows a heat-exchanging wall 116 formed of a laminate according to the present invention, with relatively shallow stiffening profiles 117 on both short sides, in addition to bent edges 118 with end flanges 119, which bent edges 118 can act as reflection dams. It is noted in this respect that it is unnecessary in most applications to make use of the smooth rounded form of deflector darns as shown for instance in Fig, la. The flows of the media axe generally steady such that there need be no fear of undesired losses. The heat-exchanging wall 116 of Fig. 13 is symmetrical. This may not be essential in " all circumstances, While the above examples illustrate preferred embodiments of the present invention it is noted.that various other arrangements may also be considered which fell within the spirit and scope of the present invention as defined by the appended claims. CLAIMS A heat exchange element comprisd&g a fbimable laminate of a mct8l layer and a heat-seal layer, the laminate being sealed tmder heat and pressure to itself or to another similar laminate to form a flow channel for a heal exchange medium, the heat exchange element further comprising a water-retaining layer. The heat exchange element according to claim 1 wherein die metal layer comprises soft aimtaled aluzmniuni* ■.■"The .heat exchange element according to any preceding claim, wherein the metal layer has > i tBicfiesrofhetween 25 microns and 120 microns, preferably around 70 microns. The heat exchange element according to any preceding claim, wherein the heat-seal layer is substantially coextensive with the metal layer. The heat exchange element according to any preceding claim, wherein the heal-seal layer is provided on both surfaces of the metal layer. . . The heat exchange element according to any preceding claim, wherein the water-retaining layer is provided on only one surface of the laminate. The heat exchange element according to any preceding claim, wherein &e laminate is formed into a convoluted shape having an increased surface area. The heat exchange element according to any preceding claim, wherein the laminate is generally corrugated to form a plurality of fins. 9- Tike beat exchange elemeot according to any pjecedhjg claim, wherein the laminate is provided on one or both surfaces -with a ptomlity of fins connected raider heat and pressure in h^ wiuiacting itlationship ^vrith flic laminate to increase fhe effective surface area thcrcot 10. The beat exchange clement according to claim 9, wherein the fins are formed of a Ifrmfnate as defined in any of claims I tot. 1L The heat exchange dement according to any preceding claim, Tchosm the flow channel comprises an elongate flat tube of generally rectangular cros$-ssctioiL i 12.Tbe'heat"exchange clement according to claim llrwhereinthe tube comprises a first laminate portion having lateral edges, the edges being folded togdher and sealed to form an elongate seam. 13. The heal exchange dement according to claim 11, wherein the tube comprises first and second laminate portions each having lateral edges, the first and second laminate portions bring sealed to one another along their respective edges. 14. A method of mamifectaring a heat exchanges:, comprising: providing a plastically detbrmable first metal laminate; providing a plastically defonnable second laminate; plastically forming fee first laminate into a generally corrugated shape having a series of troughs; connecting the first laminate to the second laminate at the series of troughs to form a heat-transmitting "wall vntii hc&t-condootbg fins; and seaBtxg the second laminate to itself or to another similar laminate to form a flow channel. . The method according to claim H wherein at least the first or the second btmmfa comprises a heat-scalable layer and the first and second laminates are connected together by heat sealing at a £r& temperatare- . The method according to claim 15, wherein the second lament* comprises a heat-scalable layer and ths second laminate h sealed to itself or to another similar laminate by heat sealing at a second temperature lower than the first tempecttoe. , The method according to any of claims 14 to 16, wherein the first ^^r^ comprises first and second surfaces, the first surface being provided with a water retaining layer and the second surface being connected to ^ secMd laminate. _ . The method according to any of claims 14 to 17, further comprising the step of dividing die first laminate into sections prior to connecting it to the second laminate. The method according to claim 18, wherein the second laminate comprises first and second surfaces and sections of the first laminate are connected to both of the first and second surfaces of the second laminate. The method according to any of claims 14 to 19, further comprising the step of forming IOOYTCS in the first laminate prior to connecting it to the second laminate-

Full Text

HEAT EXCHANGER AND METHOD OF MANUFACTURE THEREOF
The present invention relates to a beat exchange element and a foimable laminate for the manufacture of such a heat exchange element in particular for use in heat exchange between two fluid flows such as in an evaporative type heat exchanger. The invention also relates to a method of manufacturing such a beat exchange
element,
Heat exchai^sTs for heat exchange "between two.fiuid streams are generally known in which a dividing wall separates the two fluid streams. In general, it is an objective of many such devices to increase the surface area of the dividing wall to increase the effective heat transfer between the two fluids. Generally, the wall will be thin to maximise the thermal gradient and in such cases, the conductivity, of the wall material is not critical if its total area is sufficiently large, A device is known from JEPQ2ZZQSS* ^sh »s_# a coni^t^jsh^tlo^oduc^Aii^j^hange filament,
It haE also been suggested to uss metal sheet formed into U-bends to form a dividing wall. Such a device is known from US4384611. Conventional metal heat exchangers have used various techniques to join parts of the exchanger together. Typical joining techniques include crimping, welding brazing' and adhesives. The use of such techniques has been found to have certain disadvantages in terms of cost, integrity-and complexity of the joini and the joining procedure. Particularly in cases where a wall is provided" with additional 5ns to achieve the required heat transfer, Hie joining of the fins to the wall is difficult
In low temperature applications such as domestic heat recovery and dew point coolers, plastics material and the like has frequently been adopted since it is relatively cheap to produce and easy to form into the desired .shapes. A dew-point cooler is a particular form of evaporative heat exchanger, which attempts to bring down the temperature of a product air stream to as close to the dew point temperature as'possible. For air at a given absolute humidity, the dew point is the . temperature ai whicLthe air reaches a relative humidity of 100%, at which point it is ' saturated and can absorb no further moisture, The heat is removed from the product

air stream by evaporation of a quantity of liquid into another working air stream. Such a process is theoretically extremely efficient and requires no compressor, as is the case for conventional refrigeration cycles. Many attempts have been made to realise such cycles but practical considerations have caused great difficulties in approaching the dew point over most temperature ranges,
An indirect evaporative gas cooler is known from US4976113 to Gershuni et al where the product and working air streams are in counter flow. Other devices axe known which operate substantially in cross flow such as the device kaown from XJS2003/0033S21 to Maisotsenko et'aL The teachings of the present invention may thus be applied to devices according to both of the above disclosures, the contents of which are hereby incorporated by reference in their-entirety. In the following, the term dew-point cooler will be used to refer to devices that cool a fluid to at or near its initial dew point by heat transfer to cause evaporation of a liquid into a working fluid operating at or near its saturation point Particularly in the case of dew-point coolers, it has been found desirable to use fins attached to a * dividing wall to achieve the necessary heat trax^fajmte conditions where the temperature gradient across the wall is smalL
According to the present invention there is provided a heat exchange element comprising a formable laminate of a metal layer and a heat-seal layer, the laminate being sealed under heat and pressure to itself or to another similar laminate to form a flow channel for a heat exchange medium. By providing such a formable laminate, complex shapes such as convolutions,-fins and the like may be easily produced that are fluid tight ensure good heat transmission and are robust
According to an advantageous embodiment of the. invention, the metal layer, comprises aluminium, in particular soft annealed aluminium, which can be easily plastically deformed. Other similar metals may also be used but soft aunealed aluminium hzs been found particularly cheap and easy to work. In particular, by choosing a marerial that if relatively inelastic, deformation of the laminate is unlikely to cause separation of the heat-sealed sections. Such forces may alternatively or additionally be reduced by choosing a relatively tnin metal layer in the form of a foil. Preferably the metal layer may iave a thickness of between 25 microns and 120 microns, more preferably around 70 microns.

In a partial embodiment of the invention, the heat-seal layer is substantially coextensive with the metal layer and may-be-applied by coating onto either one or both sides of the metal layer*
Depending upon fee nature and intended use of the heat exchange element, the laminate may further comprise additional layers. A layer ofprimer or ike like may be required between the metal layer and the heat-seal layer to improve bonding or to provide protection against corrosion Such primer may also be pigmented ox otherwise coloured to improve the aesthetic effect or to optimise heat transfer. Furthermore, for use as an evaporative heat exchanger, humidifier or for improved wicking. a water-retaining or water-transporting layer may be provided over some or afl of the surfaces of the laminate. This layer may be adhered by means of the heat-. seal layer or otherwise.
Acoardmg to a first heat exchanger e^stzuctim, theJantinate.may be formed into a .......
convoluted shape or corrugated to form a plurality of fins thereby.providing an increased surface area. In this context, an increased surface area is understood to mean an increased surface area for a given volume.
According to an alternative heat' exchanger construction the laminate may be provided on one or both surfaces with a plurality of fins or other constructions in heat conducting relationship with the laminate to increase the surface area thereof, * By the advantageous use of a metal/heat-seal laminate as described above for these fins, they may also be easily connected by a combination of heat and-pressure, The fins may further be provided with other surface area increasing elements or elements for breaking up the boundary layers of the fluids used. Such elements may take the form of lounes or openings in the fins.
A convenient shape for the flow channel is that of an elongate flat tube of generally rectangular cross-section. For use in a heat exchange unit, a number of such flow ■ channels may be located side by side in a suitable housing whereby a primary fluid can flow through the tube and a secondary fluid can flow over the outside thereof. The rabe may comprise a single laminate folded on itself and joined at the edges

along a single elongate seam. Alternatively, it may be formed of two halves from first and second laminate portions sealed to one another along respective edges.
According to a particularly advantageous application of the invention the flat tube comprises fin sections on both the interior,and exterior surfaces of the laminate, The fin sections on the interior surfaces 'support against one another and help rnnmhtm the mechanical rigidity of the tube. This is a particular advantage of the construction which allows the use of such extremely thin gauge material, For use as a dew point cooler, at least the fin sections on the exterior surfaces are provided with water retaining layers. The interior of the tube may thus serve as a primary diy flow channel and the exterior of the tube may form part of the secondary wet flow channel.
The invention alsorelates to a method of manufacturing a heat exchanger comprising.
*
providing a plastically defonnable first metal- laminate providing a plastically deifarmafale second laminate: ^plastically forming thefcst i»-m™»** i^to a generally corrugated shape having a series of troughs;, connecting the first' laminate to the second laminate at the series of troughs to form a heat-transmitting wall with heat-conducting fins; and sealing the second igTnrnate to itself or to another similar laminate to form a flow channel
Preferably, either the first or the second laminate comprises a heat-sealable layer and
#
the first and second laminates are connected together by beat-sealing at a first temperature.
Both the first and second laminates are preferably laminates as described above. In which case the second'laminae may comprises a heat-sealable layer differing from the first laminate so that the second laminate can be sealed to itself or to another similar laminate by heat sealing at a second temperature' lower than the first temperature. In this manner, the fins may first be connected to the second laminate prior to forming the second laminate into a flow channel
The method may further comprise the step of dividing the first laminate into sections prior to connecting'it to the second laminate. It has been' found, that individual fin

sections separate from one another can prevent heat conduction along the heat exchanger and can also help to encourage turbulent flow by .breaking up 1he boundary layer. His may also "be achieved by forming louvres in the first laminate prior to connecting it to the second laminate.
' According to a particular embodiment of the invention, the method further- comprises forming a water retaining layer on a first surface of the first laminate, wherein the second surface of the first laminate is- connected to the second laminate. The heat exchange element produced in this way may ideally be used in a dew point cooler, for- humidifying dry air or in a heat recovery device.
The invention also relates to a method of manufacturing a heat exchanger, comprising:
two sets of medium through-flow channels placed mutually interlaced, which
sets of channels form respectively a primary medium circuit and a secondary
medium circc&ijg^^ can flow which are physically
separated and in heat-exchanging contact;
heat-conducting walls separating said channels; and
a housing in which the walls bounding the channels are accommodated, to which housing connect at least one inlet and two outlets for the two sets of channels.
The method comprises:
* * (a) providing a plastically deforrnable plate, for instance of a plastic or a
metal such as copper or aluminium;
(b)* providing at least one metal strip moulded into a general wave shape, fox instance of copper or alitmirriiiTnj which can serve as a row of fins;
(c) plastically deforming the plate such that it acquires an edge zone with which it can be connected to a similar plate;
(d) prior to or after step (c), connecting the strip to the plastically deforrnable plate by means of the outermost surfaces of the wave shape directed toward the strip, such that a heat-conducting wall with heat-conducting fins is created;
(e) repeating steps (a), (b)s (c) and (d) a number of times to obtain a number of heat-conducting walls with fins;

(f) connecting these walls at least in twos to each other using the edge zones
according to step (c) such that a chosen number of such walls is placed in mutually parallel relation; and
(g) accommodating these walls in the housing.
In this way there is provided a method of manufectnring a heat exchanger which can he performed very inexpensively, rapidly and with great reliability, so that the heat exchangers can be manufactured, also in mass production, at considerably reduced cost compared to the prior art
The plastic -deformation can be carried out in any appropriate manner, wherein the choice is determined parity by die nature and type of ihe applied material. Use can for instance be made of pressing, themio-foxming, vacuum-forming, injection moulding.
Patticuto5jr^rQ.:&^]^or^ case ti3at"55feinimn is applied, t£e method cam advantageously be embodied such that the plastic deformation according to step (c) takes place in cold state.
The method can for instance be embodied such that the plate and/or the fins are
provided prior to step (d) with an adhesive layer and that step (d) is performed by
pressing the plate and the fins against each other at least at the position of the contact
surfaces, optionally while heating, •" *
A simple press tool can for instance be used for this pttcpose which provides the necessary adhesion through pressure and optional heating for a certain time. It must be ensured that the heat, resistance represented by the adhesive layer lies below a predetermined value. This means that the adhesive layer, given its heat-conducting properties, may have only a limited thickness after'forming of the connection.
Particular advantages are provided by the method in which the adhesive layer substantially covers fee plate end/or the fins completely and protects them against corrosion. The adhesive layer hereby fulfils an adhesive and an anti-corrosive function.

The method can for instance be embodied such that the adhesive layer is applied as
foil. . -
Particularly when a thermoplastic plastic is applied as material for the plastically ■ defoxmsfcie plate, the method can be embodied such that the adhesive .layer is formed together with the pkte by co-extrusion into a laminated co-extmdate.
An important variant of the method has the special feature that the plate and/or the fins consist of a materia] to which the adhesive layer adheres with difficulty, for instance ahramiuEL and that the part of the adhesive layer directed to the aluminium is adhered thereto via a layer of primer.
The primer layer provides an .excellent" adhesion of the adhesive' layer to the
duminium. Without the primer this adhesion would leave something to be desired,
^ .„_„. ..i
which cannot be permittedin respect of the reliabflit^ of the heat exchanger.
The latter specified method can advantageously be embodied such that the primer has a chosen colour, pattern anaVor-tertae, and that the adhesive layer is transparent. The primer can for instance be gold-coloured, A heat exchanger pkte hereby acquires an extremely attractive appearance, Colour, pattern and/or texture can also serve as coding for heat exchanger components, with an eye to ready identification of the category within the selection of technical specifications.
Li yet another embodiment the method has the special feature that the primer and/or the coating contain silver, such that the adhesive layer has an anti-microbial action. This embodiment has the ad^'antage of not requiring any specific provisions in respect of for instance bacterial contamination.
According to yet another aspect of the invention, the method has the special feature thai finished pktss wifii fins ere adhered to each other in alternate pairs using edge zones, and that a number of thus formed pairs Hie stacked onto each other prior to step (g). The finished plates or walls can for instance be identical.

The latter embodiment of the method can particularly take place such that adhesion takes place "by providing the plates in advance with the adhesive layer and pressing the edge zones against each other, optionally while heating. This method can also be performed in exceptionally simple, inexpensive and rapid manner.
This latter described method can further be embodied such that the plates are adhered to each other via a sheet which is placed beforehand therebetween and which is provided on both sides with an adhesive layer, and that the respective edge zones directed toward each other and preferably also the respective outer surfaces of the fins directed toward each ofeer are thus adhered to each other by being pressed together, optionally while applying heat for instance by feeding through hot air,
In one embodiment of the heat exchanger, at least the fins in the secondary medium through-ficrw circuit are provided with a hydrophilic and porous or fibrous coating, consisting for instance of a microporous Portland cement, which layer is kept wet by j^tcring^neans fonning p^.of^^h^t.excha^CT.5uch.kt3iat3 through'evaporation therefrom by the secondary medium, respectively the layer, the secondaxy fins, the wall the primary fins and finally the primary medium axe cooled, which layer has a small thickness such that in wet state it has a sufficiently low heat resistance such that the heat exchanger can operate as dew point cooler.
In order to obtain a good mechanical strength, cotrosion resistance and heat transfer in combination with relatively low cost, the heat exchanger can have 'the special feature that the sheet is embodied as a lamioate3 comprising a metal inner layer which is coated on both sides with plastic outer layers. The' inner layer can for instance consist of aluminium v.ith a thickness in the oider of magnitude of 25 fim. The plastic outer layers, which can consist of any suitable plastic, can for instance " also have a thickness in the order of magnitude of 25 pm or less. With such a small thickness the hsat resistance represented by the plastic outer layers is negligible.
According to another aspect of the invention, the heat exchanger can have the special feature that two sheets are each folded into the form of a rectangular wave shape, wherein the TWO wave shapes have equal- pitch, and are positioned mutually interlaced "with a relative longirudinal orientation of 90°,

Embodiments of the invention will now be described by way of example only "with, reference ID the annexed drawings, in which;
Fig. la shows a perspective view of a plastic sheet moulded by thermo-fhrming. on both sides of which heat-conducting fins are arranged;
Fig. lb shows the phase in which the sheet is folded along the two fold'lines * such thai the walls are moved toward each other,
Fig. Ic shows the end position in which the two walls are positioned fixedly in mutually parallel relation;
Fig, 2a, 2b and 2c show views corresponding to respectively fig. la, lb and 1 c of an embodiment with the same width but of greater length;
Fig. 3a shows a perspective view of a sheet having in the zoaae of the walls rectangular perforations for passage of fins;
Fig. 5b shows a perspective view of a heat-conducting wall, on both sides of which fins are arranged which fir into the perforations of the sheet according to Fig.
Fag. 4 shows a pardy broken-away perspective view of a heat exchanger, wherein the housing is omitted for the sake of clarify;
Fig. 5a and 5b show perspective views from different sides of a dew point .cooler,
Fig. 6 is a perspective view of a pact of a dew point cooler;
Fig. 7 shows a view corresponding with Fig. 4 of a variant;
Fig. 8 is a-cut-away perspective view of an alternative of the embodiment of Fie, 3a and 2b:
Fig. 9 shows a "schematic perspective view of a heat exchanger constructed from two sheets folded in mutually interlaced manner,
. Fig. 10a shows a very schematic view of a compression mould for modelling a plate into a heat-exchanging wall;
Fig. 10b shows a very schematic -view of the arranging of strips of fins on either side cf me wall; •
Fig. 10c shows the heat-exchanging wall having heat-conducting fins arranged thereon;
Fig, lOd shows the stacking of four such walls'with fins in order to form the interior of a hear exchanger according to the invention;

Fig. 11 shows an alternative, wherein the heat-exchanging walls and also 5ns are adhered to each other by means of an adhesive foil;
Fig.' 12 is a perspective, view of a practical embodiment of a strip of fins: and
Fig. 13 is a perspective view of a moulded wall,
Fig. 1 shows a moulded sheet 1 consisting of a thin foil-like material of for instance polystyrene, PVC or ?ET. It is possible using such materials to apply a relatively small wall thickness, .for instance in the order of 0.1 mm. Inexpensive production wife a short throughput time is possible with for instance ftenno-forming.
Sheet 1 is provided on both sides with schematically indicated packets of fins which, in Fig. 1 ? are designated 2 for the primary medium through-flow circuit and 3 for the secondary medium through-flow circuit,
Attention is drawn to tbe fact that the fins 2, 3 are shown very schematically. They
consist in this embodiment of strips of limited length moulded in zigzag form in the
longitudinal direction, i.e. the medium flow direction. This aspect is however not
significant for the present invention.'
Deflector rfons 4 axe formed in sheet 1 for deflecting tie relevant medium flow. This aspect will be further elucidated with reference to Fig. 4, .
Sheet I further has a number of condensation outlets in the form of funnel-shaped structures wiih triangular, intermediate forms 5 for draining water. This may for instance be condensation water: although in the case of operation of the heat exchanger as dew point cooler it may also be excess water added to the secondary medium circuit
As will be apparent from comparing the three successive steps of Fig. la, lb and lc, the walls S, 5 are folded toward each other along hinge lines 6 and 7 to form the folded-up situation shown in Fig. lc, The construction obtained here is an element of a packet of such elements together forming a heat exchanger. Reference can for instance be made in this respect to Fig. 4, 5a, 6 and 7.

The heat exchanger can also serve fox instance as a dew point cooler. As described above, aa effective, for instance intermittent watering of the beat-exchanging surface in the secondary medium circuit must in that case be ensured. This implies that 5ns 3 must be provided with a coating which has a hydrophilic character and which exhibits an open porosity ox fibrous structure such that a rapid distribution of water or other evaporable liquid can occur through capillary suction' The manner in which ' this watering takes place falls outside the scope of the present invention and will therefore not be discussed further. Fig. 5a shows this watering symbolically.
During this production phase, in which the fins are already arranged, sheet 1 according to Fig. la is treated by at least wetting the fins, in any case on their outer side, and by then applying a mortar in powder form to the fins by atomisatioa The thus obtained coating of microporous Portland cement can have a thickness in the order of for instance 50 \im. The process in question is highly controllable and produces a hydrophilic and water-buffering coating. The fins 2 in the primary circuit are not provided with such a coatmg,,_sjncejpni evaporation occurs in the primary circuit
The free edges 10 of wall parts 8, 9 are earned toward each other as according to Fig> lb and connected to each oiher as according to Fig, lc, for instance by glueing, welding or the like. It will be apparent that a sealing primary medium channel is obtained in this manner. For sealing of a secondary medium channel in which the fins 3 extend other pnmsions are necessary, in particular sealing means co-acting with a housing,
Fig. 2a, 2b and 2c show structures the same as those according to Fig. la, lb and lc, with the understanding that the length in the medium flow direction is greater, It is noted here thai the medium flow direction extends in the direction of the drawn lines of 5ns 3. The sheet is designated in Fig. 2 with reference numeral 11.
Fig. 3 a shows a sheet 21, the general structure of which corresponds with that of sheet I of Fig. I. Sheet 21 is not however provided with fins 2, 3, but is provided instead with two perforations 22, 23, Into these perforations nt fins 24 which are arranged on a hsat-conducting wall 25, for instance by welding or soldering. The fins as well as the wall can be manufactured from for instance copper. Fins designated

with 26 are likewise situated on the otiier side of the wall. The respective "blocks of fins fit into perforations 22, 23. The heat-conducting wall part 25 is adhered sealingly to plate 21, for instance by glueing. lie finally obtained structure has the same ejcfcernal structure as shown in Fig. la. The structure differs from that in Fig. la in that the piste or wall part 25 extends on the underside of sheet 1. It is of course necessary to take into account that wall part 25 must "bend readily along hinge lints
It is further noted in respect of Fig. 3b that fins 26 are shown with contour line6 only. for the sake of clarity. They are of course not visible in this perspective view,'
Fig. 4 shows the interior 31s i.e. without a housing or casing, of a dew point cooler
with the fins omitted A number of units 32, comparable to the unit of Fig. 1c, are
placed in a base 33. As described briefly above, water can be drained via water
outlets '34 via an opening 35 in base 33. .
"Fig. 5aT3i33b each'sEow a dew point cooler 41 with two units 42,43. As shown in Fig, 5b, a primary medium flow 44 is admitted to the inside from the one side. On the other side a part of this primary flow, designated 45, exits to the outside. Another part ,46 is reversed as partial flow' and passes over die watered fins 47. The thus wetted secondary airflow 48 is deflected upward by deflection dams 49 and leaves unit 41 from the top side.
Fig. 6 shows a base in die form of a tray 51 in which a number of units 52 arc disposed. Use is also made in this embodiment of deflection dams 53. Fins are not drawn. The openings between funnels 54 give access to the bottom of the tray for water drainage via outlet opening 55.
Fig. 7 shows a structure related to that of Fig. 4» Units 61 have a differently moulded
drainage provision.
Pig. 8 shows two units 71 based on the principles elucidated with reference to Fig. 3a and 3b, A copper plate or foil 72 bears on both rides fins which are ordered in respective blocte 73; 74; 75. Identical fins are situated on the non-visible side. These St as according to an arrow 176 through respective openings 76, 775 78 in preformed

sheet 79. Similarly to the structure shown in Fig. 1 c, the walls are folded in the dipper hinge zone into a mutually parallel relation, whereafter the free edges 10 are adhered to each othsr. At variance with the structure of Fig. 1> use is made in this embodiment of a single hinge line 80 which is embodied as a score with a substantially rigid zone on either side such that, also due to the correspondingly formed co-acting lower wall parts 839 84, the final mutual distance of walls 81, 82 corresponds with the chosen distance. ■
This distance can for instance be chosen such that the fins press against each other. ' By means of a suitable pressing construction it is possible to hereby achieve that units 71 (of which there can be more "than two) form a mechanically substantially rigid packet The fins thus make an essential contribution toward.the mechanical strength of the finally obtained heat exchanger.
Fig. 9 shows an alternative embodiment of the heat exchanger according to the .-iftY5ffl?S^Heat exchanger 90comprises two sheets 91, 92jtfhich are each folded in the form of respective rectangular wave shapes of identical pitch or wavelength. Sheets 91, 92 are positioned mutually interlaced with a relative longitudinal orientation of 90c. The manifolds necessary for feeding and discharging the primary and secondary medium flow are omitted from this schematic drawing. Heat exchanger 90 comprises fins, all designated with 93.
As in the embodiment of Fig,- 3,-fa the embodiment of Fig. 9 the heat exchanger 90 can advantageously be embodied such that fins 93 are in heat-exchanging contact with each other via respective holes in sheets 91,92, for instance via heat-conducting carrier plates 94. This avoids toe heat resistance via-the two sheets 91, 92 becoming disturbingly manifest at the location of the fins. Fins 93 and carrier plates 94 must in that case be in the most direct possible thermal contact with each other, for instance by means of a heat-conducting glue layer (for instance a thin pressure-sensitive or thermally activated plastic glue layer), a welding operation, a soldering operation, a mechanical coupling or the like.
Fig, 10a shows an opened mould consisting of a lower mould part 101 and an upper mould part 102 which corresponds therewith and which can be closed as according

to arrow 1C3 to cause plastic cold deformation of an aluminium plate 104, which is covered on both sides with a glue layer activated "by heat and pressure, For use with aluminiucL a PVC/poiyacrylate based adhesive has been found to be suitable. This may be provided with a thickness of about 3 microns, preferably in combinarioi: with a P VC primer in the foim of a heat-seal lacquer of about 2 micron thickness.
Kg. 10b shows that a strip of fins 106,107 is positioned from both sides on the thus formed, moulded heat-exchanging wall 105 and then pressed on as according to arrows 108,109 respectively, It is noted that the lower surfaces 120 of fins 107 and the upper surfaces 110 of fins 106 are preferably also provided with a glue layer activated by heat and pressure, 'tfbich may be of the same type as that applied to the. plate 104. Alternatively, it may be selected to. have a higher melting temperature thereby preventing loosening of the fins during heat-sealing of the pkte 104.
Fig.. 10c shows wall-105 with the strips of fins 106,107 arranged thereon.
Fig. lOd shows the manner in which a 'number of identical heat-exchanging walls 105 with fins 106, 107 arranged thereon can be coupled'to each other to form the interior of a heat exchange^ which must later also be placed in a suitable housing having inlets and outlets fear the primary and the secondary medium, as well as associated manifolds, whereby said inlets and outlets can be coupled in the correct manner to the diverse channels in heat exchanger unit 111 of Fig. lOd. In Fig. lOd it is also noted how the two sets of fins 107 support against one another to provide a reinforced structure. A foil 121 may be provided between the fins 107 in Fig. lOd to increase the stability of iht structure.
Fig. 11 shows an alternative in which an adhesive foil 112 is placed between two finished walls with fins, whereafter, by suitably pressing together the edge zones 113 with foil 112 therebetween as according to arrows 114 and by pressing the fins 107 against each other with foil 112 therebetween as according to arrows 115. a mechanically very strong structure is created which, owing to the tensively strong connection between walls 105 via adhesive foil 112, is able to withstand an increased internal pressure in the relevant heat-exchanging medium. A very effective manner of causing the adhesive fofl 112 to melt under some pressure is to feed hot air

through the space occupied by fins 107. The desired softening and, after cooling, the desired adliesion is hereby realized in a short time* The adhesive foil layer 112 is manufactured from a plastic having a relatively low softening and melting point - -compared with that of the heat-seal adhesive on the fins.
While Figs. 10a - 11 show flow channels being formed by joining two like laminate portions. It is noted that-a construction by folding a single laminate e.g. provided with fins on "both surfaces may also be achieved in a similar maimer to that shown in Figs. 1-3.
Fig. 12 shows in greater detail a strip of fins 107, for instance of copper or aluminium, as shown schematically in earlier figures. The strip can for instance be embodied as a laminate consisting of a base layer of copper or aluminium, a layer of primer applied thereto and an anti-corrosive, adhesive layer applied thereover, activated by heat and pressure for coupling of the strip of fins 107 to a wall 105. The laminate is also provided with a hguid retaining layer 204 on an upper surface thereof.
The liquid renaming layer 204 is formed from a fibrous non-woven material. Although reference is made to a liquid retaining layer, it is clearly understood that the layer is in fact a liquid retaining and releasing layer. The layer 204 is schematically illustrated to have a very open structure such that the metal laminate can be clearly seen through fee spaces between the fibres of the layer 204. An exemplary material for forming the water retaining layer is a 20gfcn2 polyester/viscose 50/50 blend available from Lantor B.V. in The Netherlands. Another exemplary material is a 30g/m2 polyamide coated polyester fibre available • under the name CoIbackTM from Colbond K V. in The Netherlands. Other materials having similar properties including synthetic and natural fibres such as wool may also be used. Where necessary, the liquid retaining layer may be coated or otherwise treated to provide anti bacterial or other anti fouling properties.
The liouid retaining layer 204 msy be adhesively attached TO the metal layer over 1he entire area of the laminate 1. For use with aluminium and Lantor fibres as mentioned above, a 2 micron layer of two-component polyursthane adhesive has been found to

provide excellent results. When present as such a fti& layer, its effect on heat transfer is negligible. Other liquid retaining layers such as Portland cement as mentioned above may also be used-According to Fig. 12 The strip comprises individual fins 216 each provided with louvres 218 in the form of elongate slots penetrating through the laminate (only the louvres on the first fin are shown). The louvres 218 are arranged in groups. A first group 220 serves to direct flow into the surface, while a second group 222 directs flow out of the surface, Thus> some of the aii flowing along the fins 216 in the direction of arrow A will "be directed through the laminate towards the lower second surface. Air following the direction of arrow B will be directed outwardly by the second group of louvres. In this way, the air alternately flows oyer the first surface, where it can receive moisture by evaporation from the liqjiid retaining layer. followed by the second surface where it can receive direct thermal energy to raise its temperature.
hi addition to, their function in directing flow between the surfaces of the fins 216, louvres 218 also serve to break up the boundary layers that may develop as ah flows along the surfaces. Other break np dements may be provided in addition or instead of the louvres 21S. Furthermore, vrhile the fins 216 of Fig. 12 are straight, curvilinear or zig-zag fins may also be produced. It-is believed that such fin shapes are advantageous in breaking up the boundary layers that develop in flow along the fins, since each time the fin changes direction, turbulent flow is re-established. Various cross-sectional shapes are also possible for the fins, including corrugations of square, trapezoidal, rectangular, bell and sbf wave shapes. In particular, it is noted that the base or trough 208 of the fin should preferably be as flat as possible with sharp comers in order to macdmise the area of heat transfer to the plate 105.
In addfton to louvres 21S, fins 216 are provided with conduction bridges 224, These
L
bridges 224 are in the fonn of cuts through the laminate over substantially the whole height of the fin 216. They serve to prevent unwanted transport of heat along the fins
216 in the direction of the air flow.

The strip of fins 107 is preferably formed using standard corrugation techniques. An appropriate width roll of prepared laminate may be fed through a pair of corrugated rollers which can form the fins 216, louvres 218 and heat bridges 224 in a single pass. The resulting product may then be cut into suitably sized strips of fins 107 for further processing.
Finally. Fig. 13 shows a heat-exchanging wall 116 formed of a laminate according to the present invention, with relatively shallow stiffening profiles 117 on both short sides, in addition to bent edges 118 with end flanges 119, which bent edges 118 can act as reflection dams. It is noted in this respect that it is unnecessary in most applications to make use of the smooth rounded form of deflector darns as shown for instance in Fig, la. The flows of the media axe generally steady such that there need be no fear of undesired losses.
The heat-exchanging wall 116 of Fig. 13 is symmetrical. This may not be essential in " all circumstances,
While the above examples illustrate preferred embodiments of the present invention
it is noted.that various other arrangements may also be considered which fell within
the spirit and scope of the present invention as defined by the appended claims.

CLAIMS
A heat exchange element comprisd&g a fbimable laminate of a mct8l layer and a heat-seal layer, the laminate being sealed tmder heat and pressure to itself or to another similar laminate to form a flow channel for a heal exchange medium, the heat exchange element further comprising a water-retaining layer.
The heat exchange element according to claim 1 wherein die metal layer comprises soft aimtaled aluzmniuni*
■.■"The .heat exchange element according to any preceding claim, wherein the metal layer has
>
i tBicfiesrofhetween 25 microns and 120 microns, preferably around 70 microns.
The heat exchange element according to any preceding claim, wherein the heat-seal layer is substantially coextensive with the metal layer.
The heat exchange element according to any preceding claim, wherein the heal-seal layer
is provided on both surfaces of the metal layer. . .
The heat exchange element according to any preceding claim, wherein the water-retaining layer is provided on only one surface of the laminate.
The heat exchange element according to any preceding claim, wherein &e laminate is formed into a convoluted shape having an increased surface area.
The heat exchange element according to any preceding claim, wherein the laminate is generally corrugated to form a plurality of fins.

9- Tike beat exchange elemeot according to any pjecedhjg claim, wherein the laminate is provided on one or both surfaces -with a ptomlity of fins connected raider heat and pressure in h^ wiuiacting itlationship ^vrith flic laminate to increase fhe effective surface area thcrcot
10. The beat exchange clement according to claim 9, wherein the fins are formed of a Ifrmfnate as defined in any of claims I tot.
1L The heat exchange dement according to any preceding claim, Tchosm the flow channel
comprises an elongate flat tube of generally rectangular cros$-ssctioiL
i
12.Tbe'heat"exchange clement according to claim llrwhereinthe tube comprises a first laminate portion having lateral edges, the edges being folded togdher and sealed to form an elongate seam.
13. The heal exchange dement according to claim 11, wherein the tube comprises first and second laminate portions each having lateral edges, the first and second laminate portions bring sealed to one another along their respective edges.
14. A method of mamifectaring a heat exchanges:, comprising: providing a plastically detbrmable first metal laminate; providing a plastically defonnable second laminate;
plastically forming fee first laminate into a generally corrugated shape having a series of
troughs;
connecting the first laminate to the second laminate at the series of troughs to form a
heat-transmitting "wall vntii hc&t-condootbg fins; and
seaBtxg the second laminate to itself or to another similar laminate to form a flow channel.

. The method according to claim H wherein at least the first or the second btmmfa comprises a heat-scalable layer and the first and second laminates are connected together by heat sealing at a £r& temperatare-
. The method according to claim 15, wherein the second lament* comprises a heat-scalable layer and ths second laminate h sealed to itself or to another similar laminate by heat sealing at a second temperature lower than the first tempecttoe.
, The method according to any of claims 14 to 16, wherein the first ^^r^ comprises first and second surfaces, the first surface being provided with a water retaining layer and the second surface being connected to ^ secMd laminate. _ . The method according to any of claims 14 to 17, further comprising the step of dividing die first laminate into sections prior to connecting it to the second laminate.
The method according to claim 18, wherein the second laminate comprises first and second surfaces and sections of the first laminate are connected to both of the first and second surfaces of the second laminate.
The method according to any of claims 14 to 19, further comprising the step of forming IOOYTCS in the first laminate prior to connecting it to the second laminate-

Documents:

1056-chenp-2005-abstract.pdf

1056-chenp-2005-claims.pdf

1056-chenp-2005-correspondnece-others.pdf

1056-chenp-2005-correspondnece-po.pdf

1056-chenp-2005-description(complete).pdf

1056-chenp-2005-drawings.pdf

1056-chenp-2005-form 1.pdf

1056-chenp-2005-form 18.pdf

1056-chenp-2005-form 3.pdf

1056-chenp-2005-form 5.pdf

1056-chenp-2005-pct.pdf

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Patent Number

219812

Indian Patent Application Number

1056/CHENP/2005

PG Journal Number

27/2008

Publication Date

04-Jul-2008

Grant Date

13-May-2008

Date of Filing

27-May-2005

Name of Patentee

OXYCELL HOLDING B.V.

Applicant Address

Kaagstraat 17-19, NL-8102 GZ Raalte,

Inventors:

#	Inventor's Name	Inventor's Address
1	REINDERS, Johannes, Antonius, Maria

PCT International Classification Number

F24F5/00

PCT International Application Number

PCT/EP2003/012132

PCT International Filing date

2003-10-31

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	1021794	2002-10-31	Netherlands
2	1022794	2003-02-27	Netherlands