OA18366A - Enthalpy exchanger element, enthalpy exchanger comprising such elements and method for their production - Google Patents

Abstract

The present invention provides enthalpy exchanger elements (E, E') and enthalpy exchangers comprising such elements. Furthermore, the invention discloses a method for producing such enthalpy exchanger elements and enthalpy exchangers, comprising the steps of a) providing an air-permeable sheet element (1); b) laminating at least one side (la, lb) of the sheet element (1) with a thin polymer film (3, 4) with water vapor transmission characteristics; and c) forming the laminated sheet element (1) into a desired shape exhibiting a three-dimensional corrugation pattern (5,5, ...).

Description

The présent invention refers to enthalpy exchanger éléments and enthalpy exchangers comprising such éléments. Furthermore, the invention discloses a method for producing such enthalpy exchanger éléments and enthalpy exchangers.

It is well known to use different kinds of heat exchangers for different purposes. Usually, heat exchangers are used to recover heat energy from one fluid or medium into another one. This kind of heat energy is called sensible energy. The heat energy or sensible energy of one fluid, normally air, is recovered into another one which is running adjacent, e.g. parallel, counter or cross flow, to the first where the fluid is at lower température. By inversing fluid flows, the exchange between the two will generate a cooler fluid. Heat exchangers used for sensible energy recovery are usually made of métal or polymer éléments. There are different types, as there can be cross flow, parallel flow or counter flow configurations. The éléments are t* defming flow channels between themselves so that the fluids can flow between the éléments. Such devices are e.g. used in residential and commercial ventilation (HRV).

Another type of energy exchangers refers to the so called latent energy which ,î includes the moisture in the air. To exchange the latent energy it is known to use desiccant coated métal or polymer substrates or membranes made from desiccant impregnated cellulose or polymer. Between plates made from cellulose or polymer, air passages are defined or created to allow the fluids to pass along the surface of the plates, thereby transferring moisture from one fluid to the other one. As the ¢membranes usually hâve no structural strength, it is known to combine the membranes with frames or grids which thereby define spacings between the membranes.

In case of a combination of the above, i.e. heat exchange and moisture exchangè, the energy exchangers are called enthalpy exchanger. Those enthalpy exchangers allow for the exchange of sensible and latent energy, resulting in total energy recovery.

Membrane materials as currently available are delivered by the roll. The membrane material is the most critical part of an enthalpy exchanger. The membrane müst be fixed and sealed to a kind of grid or frame and arranged in a way to allow for a fluid to flow between each membrane layer. So, it is obvious that enthalpy exchangers of the known art are a compromise. They will usually lose in sensible energy exchange to gain in latent energy exchange as a resuit of the sélective scope and characteristics of currently used membranes.

Such an enthalpy exchanger built from respective éléments is e.g. WO 02/072242 Al. On grids, respective membranes made of fibers are positioned. Grids containing a membrane or spacers between adjacent membranes, i.e. spacers and membranes in f altemating sequence, are stapled or stacked, thereby altering the direction of the plates in order to create different air flow directions.

In view of the mentioned state of the art, it is an object of the invention to provide enthalpy exchanger éléments and enthalpy exchangers as well as a method for their t

production which allow for the création of enthalpy exchangers where the efficiency of both sensible energy exchange and latent energy exchange in each enthalpy exchanger element is increased and where the manufacturing cost of enthalpy exchanger éléments and enthalpy exchangers made of such éléments is reduced.

i

It is another object of the invention to provide enthalpy exchanger éléments and *

enthalpy exchangers with a high spécifie exchange area for water vapor, as well as a method for their production.

In order to achieve this object, the invention provides a method for producing enthalpy exchanger éléments comprising the steps * of

a) providing an air-permeable sheet element;

b) laminating at least one side of the sheet element with a thin polymer film with water vapor transmission characteristics; and

c) forming the laminated sheet element into a desired shape exhibiting a three- » dimensional corrugation pattern.

As a resuit, an enthalpy exchanger element is obtained which allows both the transfer of heat and water molécules in the form of vapor across the element from one side of the element to the other side of the element almost throughout the entire surface area of the element which now has a higher spécifie exchange area than such éléments in the prior art. In contrast, molécules larger or less polar than water molécules, such as carbon dioxide and odor-related molécules, are barred from passing across the element. In addition, the sheet element and the selectively water vapor transmissible barrier material laminated to at least one side of the sheet element are formed into the desired corrugated shape using only one forming step (“one-step forming”). Thus, in the enthalpy exchanger element according to the invention, total (i.e. sensible plus latent) energy transfer efficiency is increased on the one hand while manufacturing cost is reduced on the other hand.

Altematively, the sequence of steps b) and c) in the method may be switched, i.e. forming the (not yet laminated) sheet element into a desired shape exhibiting a three-dimensional corrugation pattern and then laminating at least one side of the formed sheet element with a thin polymer film with water vapor transmission characteristics (“two-step forming”).

Water vapor transmission characteristics means a water vapor transmission rate of at least 500 g/m²/24h, preferably of at least 1000 g/m²/24h, even more preferably of at least 1500 g/m /24h and most preferred of at least 2000 g/m /24h, as measured using the upright cup method according to modified ASTM E 96-66 B; modifications: TWater⁼ 30°C, Taj_r = 21°C, rel. humidity = 60%, air flow = 2m/s. *

Step c) of forming the laminated sheet element into a desired shape exhibiting a three-dimensional corrugation pattern may include a first step cl) and a second step c2).

Step cl) comprises forming a first corrugation pattern or reinforcing corrugation pattern with corrugations extending in a first direction and having a relatively fine structure. The first corrugation pattern may hâve a sinusoïdal, rectangular or triangular periodic profile. Preferably, this first periodic profile of the first corrugation pattern has a period of 0.5 mm to 2 mm and an amplitude of 0.5 mm to 1 mm. The first corrugation pattern may comprise adjacent ridges. There may be a spacing between neighboring ridges, i.e. the space of the laminated or not yet laminated sheet element between neighboring ridges is a substantially fiat région and the neighboring ridges may protrude in the same or in opposite directions from the sheet element. The height or depth as well as the width of these individfually located ridges may be 0.2 mm to 1 mm. The ridge spacing may be 1 to 10 times the ridge width.

This optional first step cl) contributes to the overall stiffness of the enthalpy exchanger element.

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Step c2) comprises forming a second corrugation pattern or main corrugation pattern with corrugations extending in a second direction and having a relatively coarse structure defining the heat exchanger plate channel cross section geometry. Again, the second corrugation pattern may hâve a sinusoïdal, rectangular or triangular periodic profile, but with larger dimensions than the first corrugation pattern. Preferably, this second periodic profile of the second corrugation pattern has a period of 2 mm to 10 mm and an amplitude of 2 mm to 10 mm. As a resuit, the optional first step cl) and the necessary second step c2) provide an enthalpy exchanger element with double corrugation and enhanced rigidity. *

The first direction, i.e. the direction of the ridges of the first corrugation pattern, forms an angle with respect to the second direction, i.e. the direction of the ridges of the second corrugation pattern, preferably an angle of 45° to 90°, more preferably an angle of 85° to 90° and most preferably about 90°.

The sheet material of the sheet element may comprise a polymer, preferably a thermoplastic polymer. Thus, the sheet element lends itself for instance to thermal processing in the forming step c). Preferably, polystyrène (PS), polyvinyl chloride a

(PVC), viscose or polyester, such as polyethylene terephthalate (PET), or copolyester are selected as thermoplastic polymer. Preferably, the polymer of the sheet material does not include any plasticizer. The polymer of the sheet material may include a biocide (bactéricide and/or fungicide).

*

In a preferred embodiment, the sheet element is a fabric, preferably a nonwoven fabric. The fabric may include thermoplastic fibers only or a combination of thermoplastic fibers and thermoset fibers or a combination of thermoplastic fibers and a resin or a combination of thermoplastic fibers and inorganic fibers. Most preferably, the fabric includes multicomponent or bicomponent fibers together with standard thermoset and/or thermoplastic fibers. Preferably, the fabric includes more than 50 wt. % multicomponent or bicomponent fibers and may include multicomponent or bicomponent fibers only. In addition, the fabric may include métal fibers and/or wick fibers providing high thermal conductivity together with mechanical strength and high capillary action (“humidity conductivity”), respectively. The inorganic fibers may be glass fibers, silicon carbide fibers or any minerai fiber.

Altematively, the sheet element is a woven fabric, preferably having an anisotropic structure and anisotropic properties resulting therefrom. For instance, the woven fabric may hâve thicker polymer fibers in a first fiber direction and thinner polymer fibers in a second fiber direction. The second fiber direction may be between 90° and 100°, preferably about 90°, with respect to the first fiber direction. Due to the thicker polymer fibers in the first fiber direction, the anisotropic woven fabric can withstand more stretching along the first fiber direction without being mechanically weakened (or even damaged) than along the second fiber direction with thinner polymer fibers.

Altematively, the sheet element may comprise a nonwoven fabric which may hâve an anisotropic structure and anisotropic properties resulting therefrom, and a Woven fabric, preferably having an anisotropic structure and anisotropic properties resulting therefrom.

The sheet element may comprise additional reinforcement fibers for providing extra strength. These reinforcement fibers may be at least one of métal fibers, càrbon fibers or thermoplastic polymer fibers. The reinforcement fibers may extend in a first general direction within the sheet element. Preferably, the reinforcement fibers are non-straight. In particular, they may hâve a wave-like pattern, e.g. with a triangular or sinusoïdal fiat pattern, preferably having periods of 1 mm to 3 mm and amplitudes of 1 mm to 3 mm. Altematively, they may hâve a curly shape, e.g. a helical shape, preferably having a hélix diameter of less than 1 mm.

The reinforcement fibers may be continuous fibers or staple fibers with minimum length of 5 mm. The métal fibers may be selected from aluminum, copper, silver or steel fibers having a diameter between 10 μιη and 200 pm, preferably between 20 pm to 100 pm.

Preferably, the first general direction of the wave-like pattern and/or the curly shape of the reinforcement fibers form an angle with respect to the direction of the sçcond corrugation pattern defining the heat exchanger plate channel cross section geometry. Preferably, they form an angle of 45° to 90°, more preferably an angle of 85° to 90° and most preferably an angle of about 90° with respect to each other.

During step c) or in particular during steps cl) and c2), but primarily during step c2), the non-straight reinforcement fibers are straightened out. In particular, the wave-like pattern and/or the curly shape is stretched and thus flattened in profile, i.e. the amplitude of the wave-like pattern is reduced and its period is increased and/or the diameter of the curly/helical shape is reduced and its period (or pitch) is increased. Once the non-straight carbon and/or métal fibers are completely straightened out, the sheet element will be prevented from further stretching along the first general direction.

In addition, if the sheet element is heated beyond the softening température of the thermoplastic polymer fibers before or during step c) or in particular before or during steps cl) and/or c2), the thermoplastic fibers will be deformed by undergoing local stretching and/or bending. After the forming step c) or the forming steps cl) and c2), the permanent deformation of the thermoplastic polymer fibers will contribute to the dimensional stability, i.e. shape rétention, of the enthalpy exchanger element. *

Preferably, if carbon fibers are included within the sheet element, they extend along the second direction of the second (main) corrugation pattern. Thus, during forming step c) or during forming sub step c2), the carbon fibers will not undergo any Λ sbending. However, they contribute to the overall strength of the sheet element before and after the forming step c) or c2).

Preferably, if métal fibers are included within the sheet element, they may extend along whatever directions within the sheet element. Thus, during forming steppe) or during forming sub step c2), the métal fibers will undergo bending under métal cold deformation conditions even if the sheet element is heated beyond the softening température of thermoplastic polymer fibers. After the forming step c) or the forming steps cl) and c2), the permanent deformation of the métal fibers will contribute to the dimensional stability, i.e. shape rétention, of the enthalpy exchanger element.

Preferably, the fibers of the fabric hâve fiber diameters between 1 pm and 40 pm, more preferably between 3 pm and 40 pm and most preferably between 5 pm and 20 pm. As a resuit, when the fabric is laminated with the thin polymer film-with water vapor transmission characteristics in the laminating step b), the fabric fibers in direct contact with the thin polymer film will cover only a small portion of the surface of the thin polymer film, thus minimizing any blocking of the thin polymer film. In addition, even if not permanently deformed as described above for thermoplastic polymer fibers or métal fibers, any fabric fibers undergoing elastic bending during step c) will hâve a high degree of flexibility which helps make the forming step c) easier to perform.

Preferably, the fibers or fabric filaments within the sheet element and in particular those at a non-laminated surface of the sheet element, may hâve linear 'mass densifies (filament weights) between 1 and 10 dtex (1 tex = 1 g/lOOOm; 1 dtex = lg/lOOOOm). Such fine fibers exhibit a strong wicking effect alloying them to transport humidity faster. In addition, when used at a sheet surface or at both sheet surfaces, they provide a smoother and less abrasive surface. First, this helps reduce the risk of damage to a very thin adjacent functional membrane layer laminated to the respective surface. Second, this helps prevent the formation any air boundary layer at a non-laminated sheet surface.

The fibers of the fabric may hâve substantially circular, triangular or oval çrosssections. Also, the fibers of the fabric may hâve X-type or star-like cross-sections. The fabric may include fibers having different cross-sections, preferably chosen from the mentioned types of cross-sections.

In addition, the fabric may include a surface imprégnant, preferably a thermoplastic or thermoset polymer, in order to improve structural stability after the forming step. In addition or as an alternative, the fabric may include a surface imprégnant which can be cross-linked after the forming step c), preferably a resin which can be cured by UV irradiation after the forming step c).

The fabric or the enthalpy exchanger element may include a hydrophobically treated layer on one of its sides and a thin polymer film on the other side, i.e. a single water repellant imprégnation.

This can be achieved by laminating only one side of the fabric with a thin polymer film with water vapor transmission characteristics in step b) and providing the other side of the fabric with a hydrophobization treatment before, during or after the laminating step b). The hydrophobization treatment may be carried out even after the forming step c).

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Preferably, the hydrophobization treatment of the fabric is carried out before the laminating step b), i.e. before, during or after the providing step a). This prevents the thin polymer film with water vapor transmission characteristics to be accidentally rendered hydrophobie on its surface facing the fabric.

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The fabric or the enthalpy exchanger element may include a hydrophobically treated layer on both of its sides and a thin polymer film inside extending in between and “in parallel” to the first hydrophobically treated layer and to the second hydrophobically treated layer of the fabric or the enthalpy exchanger element, i.e. a double water repellant imprégnation. *

This can be achieved by the following steps:

First, providing one side of a first fabric or the entire first fabric with a hydrophobization treatment before, during or after any laminating step b). ’

Second, providing one side of a second fabric or the entire second fabric with a hydrophobization treatment before, during or after any laminating step b).

Third, laminating one side of the first fabric with a first side of a thin polymer film with water vapor transmission characteristics.

Fourth, laminating one side of the second fabric with a second side of the thin polymer film with water vapor transmission characteristics producing a sandwich structure having the thin polymer film sandwiched between the first fabric and the second fabric.

Finally, according to step c), this laminated sheet element having a first fabric / thin film / second fabric type sandwich structure is formed into a desired shape exhibiting the three-dimensional corrugation pattem. ÿ

Preferably, steps three and four are carried out at the same time, i.e. co-laminating or one-step laminating the first fabric and the second fabric with the one thin polymer film with water vapor transmission characteristics producing the sandwich structure with the thin polymer film sandwiched between the two fabric sheets. ► £

Preferably, the hydrophobization treatment of the first fabric and/or the second fabric is carried out before any laminating step b), i.e. before, during or after the fabric providing step a). Again, this prevents any thin polymer film with water vapor transmission characteristics to be accidentally rendered hydrophobie on its surface facing the fabric, i.e. first fabric or the second fabric. *

Instead, the hydrophobization treatment of the first fabric and/or the second fabric may be carried out after the forming step c).

The sheet element may be composed of one layer of fabric comprising any of the combinations of fibers mentioned in the previous paragraph. Alternatively, the sheet element may be composed of several, preferably two or three, stacked layers of fabric attached to each other and each comprising a different one of the combinations of fibers mentioned in the previous paragraph.

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The several stacked layers of fabric may hâve different filament weights. They may comprise a first layer having relatively fine filaments, e.g. 1 to 10 dtex, and a second layer having relatively coarse filaments, e.g. 10 to 40 dtex.

Preferably, the second layer with the coarser or heavier filaments is attached to the thin polymer film (membrane), providing a small direct contact area between the sheet element surface and the thin polymer film attached to it, thus increasing the active membrane surface area of the thin polymer film. Preferably, at least a portion of the heavier filaments are bicomponent fibers allowing the thin polymer film to be attached to the sheet element surface with less glue or no glue at ail. *

Alternatively, depending on the type of filaments, it can be advantageous if the first layer with finer filaments is contacted with and attached to the thin polymer film (membrane), providing a smooth surface at the sheet element / thin polymer film interface that does not damage the polymer film during the forming step *c) of * forming the corrugation pattern or during the forming sub step c2) of forming the second corrugation pattern or during end use.

Irrespective of its position within the sheet element, the second layer with heavier or thicker filaments will provide an open and highly air and vapor permeable layer of the sheet element.

In addition, the sheet element may comprise fine filaments or fibers with strong wicking properties to enhance transport of humidity through the sheet element. Preferably, the fine filaments or fibers, when measured according to DIN 53924, exhibit rising heights of at least 30 to 60 mm after 30 seconds and more preferably rising heights of at least 40 to 60 mm after 30 seconds.

If the forming in step c) or in step c2) in done by vacuum forming with the support of an upper pleating tool, the sheet element may hâve an asymmetric structure across its thickness. In particular, it may hâve a layer with relatively fine filaments on the vacuuming side, providing good réplication of the mold geometry, and relatively coarse filaments facing the upper pleating tool, providing the required structural strength to the sheet element.

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The sheet element may comprise a layer of nonwoven fabric and a layer of woven fabric attached to each other. Preferably, the woven fabric has an anisotropic structure and anisotropic mechanical properties resulting therefrom, as described above.

A portion of the fibers within the sheet element, preferably 5 to 60 wt.%, may be hollow fibers. A portion of the fibers within the sheet element, preferably 20 to 70 wt.%, may be bicomponent fibers. These bicomponent fibers may hâve circular and/or non-circular cross sections.

A portion of the fibers within the sheet element, preferably 5 to 60 wt.%, may be hydrophilic fibers showing strong wicking properties to increase transport of humidity. Preferably, such wicking fibers are hydrophilic on their surface and hydrophobie in their center.

*

A portion of the fibers within the sheet element, preferably 5 to 30 wt.%, may be water absorbing fibers, preferably hydro polymers, to create a water buffer for excess humidity.

The sheet element may hâve a textured surface and/or an integrated grid structure, t*

As a resuit, this type of sheet element will cover a minimum surface area of the adjacent thin polymer film attached to the sheet element. The integrated grid structure may be the above-described first or reinforcing corrugation pattern formed in the first forming step cl).

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In addition or as an alternative to the above-described measures for increasing the

structural	strength	of the	sheet	element,
1)	hydroentanglement	and/or	spunlacing;	and/or
2)	surface	texturing;	and/or

3) intégration of a grid structure with a pattern adapted to the geometry qf the second or main corrugation pattern may be applied to the not yet laminated sheet element before subséquent lamination.

In addition or as an alternative to the above-described measures for increasing the structural strength and the formability of the sheet element, the sheet element may be made with an anisotropic fiber distribution providing higher overall strength of the sheet element and/or higher strength in a preferred direction of the sheet element. In particular, as mentioned above, the anisotropic fiber distribution may be provided by at least one of carbon fibers, métal fibers or thermoplastic polymer fibers included in at least one of the several layers of the sheet element.

Preferably, the métal fibers and/or thermoplastic polymer fibers are oriented in close-to-orthogonal relationship with respect to the second direction of the second (main) corrugation pattern or they may extend along whatever directions within the * sheet element. Preferably, the carbon fibers are oriented in parallel to the second direction of the second (main) corrugation pattern.

The laminating step b) may comprise bonding, preferably heat bonding, welding and/ôr gluing, of the thin polymer film to the sheet element. Preferably, a * thermoplastic adhesive (hot melt adhesive), a thermoset adhesive or a UV-curable adhesive is used for the bonding between the polymer film and the sheet element.

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In a preferred embodiment, the thin polymer film is a monolithic membrane, i.e. a poreless membrane exhibiting a solution-diffusion transport mechanism for

A individual water molécules. Preferably, this monolithic membrane has a maximum élongation between 100% and 300%, more preferably between 150% and 200%.

In a further preferred embodiment, the thin polymer film is a multilayer film comprising a sequence of polymer layers of different polymer types. Thus, with a *

few given polymer types, thin polymer films of different water vapor transmission characteristics can be designed and produced.

Preferably, the polymer type of each polymer layer is selected from the group consisting of polyether ester, polyether amide and polyether urethane.

Preferably, the total thickness of the thin polymer multilayer film is between 5 pm and 200 pm, more preferably between 10 pm and 150 pm.

The thickness of each individual polymer layer within the thin polymer multilayer film may be between 1 pm and 20 pm, preferably between 4 pm and 20 pift and most preferably between 4 pm and 15 pm.

In general, the polymer film(s) or polymer layer(s) should be as thin as possible for high transport rates. In the setup of the enthalpy exchanger element according to the invention, the limiting layer for transport of water vapor is the three-dimensionai sheet element located next to the one polymer laminate or between the two polymer laminates. In order to achieve mechanical strength and robustness of the laminate(s) on the one hand and high transport rates on the other hand, a setup is chosen with a polymer film (laminate) thickness between 1 pm and 20 pm, preferably between 4 pm and 20 pm and most preferably between 4 pm and 15 pm. Also, the Îhrcedimensional sheet element is a thin as possible and as permeable as possible. Preferably, the sheet element is a fabric having a thickness between 200 pm and 600 pm, preferably between 300 pm and 500 pm. Preferably, the sheet element is a fabric having a fiber volume portion between 10% and 65% of the fabric volume, preferably between 20% and 50% of the fabric volume.

Preferably, the thermoplastic polymer(s) of the thin polymer film does not include any plasticizer. Instead, the thin polymer film may include a biocide (bactéricide and/or fungicide). The biocide will help prevent growth of bacteria and fungi on the p polymer and thus achieve longer operation periods without cleaning.

As mentioned above with respect to the thermoplastic polymer; the forming step c) may be a pleating step or thermoforming step, preferably a vacuum forming step. At least a first mold part (e.g. lower tool) having first corrugation formations cor defining the predetermined corrugation pattern of the enthalpy exchanger element to be manufactured, is provided in the thermoforming step. In addition to the at least first mold part, a second mold part (e.g. upper tool) having second corrugation formations complementary to the first corrugation formations and/or a forming

I* vacuum co-defining the predetermined corrugation pattern of the enthalpy exchànger element to be manufactured, is/are provided in the thermoforming step.

Preferably, prior to the actual forming operation of the laminated sheet element at a spécifie predetermined forming température of the first mold part or at spécifie predetermined forming températures of the first and second mold parts; the laminated sheet element is preheated to a preheating température a few degrees below the forming température. For pleating, the preheating température may be lower.

Preferably, the forming température is provided by intemally heated first and/or second mold parts.

Preferably, the preheating température is provided by exposing the not yet formed laminated sheet to electromagnetic radiation (e.g. at infrared or microwave r frequencies) and/or to mechanical waves (e.g. at ultrasonic frequencies).

The invention also provides an enthalpy exchanger element, preferably produced using the method as defined in the previous paragraphe, including a sheet element and a predetermined corrugation pattern, wherein a first thin polymer film is laminated to a first side of the sheet element and/or a second thin polymer film is laminated to a second side of the sheet element, both thin polymer films having water vapor transmission characteristics.

The first thin polymer film and the second thin polymer film may be identical to each other. If both sides of the sheet element are laminated, an enthalpy exchanger element having excellent hygienic properties is obtained. If only one side of the sheet element is laminated, the thermoplastic polymer of the sheet material preferably undergoes a hydrophobization treatment and/or includes a biocide

183&6 (bactéricide and/or fongicide) and again, an enthalpy exchanger element having excellent hygienic properties is obtained.

The first thin polymer film and the second thin polymer film may be different from each other. This provides additional freedom to adjust and optimize the heat and moisture transfer characteristics of the enthalpy exchanger element. *

Finally, the invention provides an enthalpy exchanger having at least three sheet-Iike or plate-like enthalpy exchanger éléments as defined in any of the previous paragraphe, which are stacked onto and fixed to each other with their respective corrugation patterns in parallel orientation to form parallel fluid paths allowing fluids to flow there through. The individual enthalpy exchanger éléments may be fixed to each other and sealed by welding, preferably using laser welding, and/or gluing, preferably using epoxy.

*

A non-limiting embodiment of the invention is described in forther detail below with reference to the drawings, wherein:

Fig. 1 is a schematic représentation of the method for producing enthalpy exchanger éléments according to the invention; _f

Fig. 2 is a schematic représentation of an enthalpy exchanger according to the invention or a portion thereof including a plurality of enthalpy exchanger éléments according to the invention;

Fig. 3 is a SEM (scanning électron microscope) micrograph of a cross-sectional view of a portion of an intermediate product produced during the method for producing an enthalpy exchanger element according to the invention;

Fig. 4 is a SEM micrograph of a cross-sectional view of a portion of an enthalpy exchanger element produced by the method according to the invention;

Fig. 5 is a SEM micrograph similar to the one of Fig. 3 showing of a larger scale cross-sectional view of a smaller portion of an intermediate product produced during the method for producing an enthalpy exchanger element according to the invention; and

Fig. 6 is a SEM micrograph similar to the one of Fig. 4 showing of a smaller scale cross-sectional view of a larger portion of an enthalpy exchanger element produced by the method according to the invention. *

In Fig. 1, a schematic représentation of the method for producing enthalpy exchanger éléments according to the invention is shown. Cross-sections of the intermediate products, i.e. the results of each of steps SI, S2 and S3, are shown.

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In a first step SI, an air-permeable sheet element 1 having voids or openings 2 is provided.

In a second step S2, both sides la, lb of the sheet element 1 are laminated with a thin polymer film 3,4 with water vapor transmission characteristics.

In a third step S3, the laminated sheet element 1 is formed into a desired shape exhibiting a three-dimensional corrugation pattern 5.

The sheet element 2 is a non-woven fabric including thermoplastic fibers only or a combination of thermoset fibers and thermoplastic fibers. The fabric may inplude bicomponent fibers together with standard thermoset and/or thermoplastic fibers.

The thin polymer film 3, 4 is a multilayer film which may comprise a sequence (not shown) of polymer layers of different polymer types.

I*

The forming step S3 is a thermoforming step, preferably a vacuum forming step. i*

At least a first mold part (e.g. lower tool, not shown) having first corrugation formations co-defining the predetermined corrugation pattern 5 of the enthalpy exchanger element E, E’ to be manufactured, is used in the thermoforming step S3. In addition to the at least first mold part, a second mold part (e.g. upper tool, not shown) having second corrugation formations complementary to the * first corrugation formations and/or a forming vacuum co-defining the predetermined corrugation pattern of the enthalpy exchanger element E, E’ to be manufactured, is/are used in the thermoforming step S3.

The resulting enthalpy exchanger element E having a first thin polymer film 3 qn the first side la of the sheet element 1 and a second thin polymer film 4 on the second side lb of the sheet element 1 comprises a corrugated structure 5 with altemating squeezed portions 5a and squeezed/stretched portions 5b. The squeezed portion 5a extend in a first direction (horizontal direction in Fig. 1) and the squeezed/stretched portions 5b extend in a second direction different from the first direction. Preferably, the angle a between the first direction and the second direction in the corrugation pattern 5 of the enthalpy exchanger element E is between 90° and 120°, preferably between 95° and 105°, an example of which is shown in Fig. 1. Alternatively, unlike the example shown in Fig. 1, the angle a between the first direction and the second direction in the corrugation pattern 5 of the enthalpy exchanger element *E is between 80° and 90°, preferably between 85° and 90°.

In Fig. 2, a schematic représentation of a first type enthalpy exchanger E1-E2-E3 or second type enthalpy exchanger El’-E2’-E3’ according to the invention is shown. The first type E1-E2-E3 includes a plurality of enthalpy exchanger éléments EÎ, E2, E3 where the first thin polymer film 3 and the second thin polymer film 4 (Fig. 1) are films of the same type. The second type El’-E2’-E3’ includes a plurality of enthalpy exchanger éléments ΕΓ, E2’, E3’ where the first thin polymer film 3 and »

the second thin polymer film 4 (Fig. 1) are films of different types including the case * where one of the two films 3, 4 has zéro thickness, i.e. the enthalpy exchanger element has only one thin polymer film 3 or 4 on one side la or lb of the sheet element 1. ‘

In Fig. 2, the outer walls of the housing/packaging of the enthalpy exchanger E1-E2t

E3 or El’-E2’-E3’ is not shown. The air inlet/outlet portions (not shown) of the enthalpy exchanger E1-E2-E3 or El’-E2’-E3’ are provided with air distribution patterns such that the air flow direction in adjacent air ducts in the enthalpy exchanger E1-E2-E3 or El’-E2’-E3’ are in opposite directions, as shown by the O symbol indicating air flow towards the viewer and the X symbol indicating air. flow away from the viewer.

Fig. 3 shows a SEM (scanning électron microscope) micrograph of a cross-sectional view of an air-permeable sheet element 1 laminated on its upper side la with a first thin polymer film 3 and laminated on its lower side lb with a second thin polymer film 4 as a resuit of step b) of the method according to the invention.

The laminating step b) may comprise bonding, preferably heat bonding and/or gluing, of the thin polymer films 3, 4 to the sheet element 1. A thermoplastic adhesive (hot melt adhesive) may be used for the bonding between the polymer film 3 and 4 and the sheet element 1.

The sheet element 1 is a nonwoven fabric comprising a plurality of fibers 6. The fibers 6 may be thermoplastic fibers only or a combination of thermoset fibers b and/or minerai fibers on the one hand and thermoplastic fibers on the other hand. Most preferably, the fabric includes multicomponent or bicomponent fibers together with standard thermoset and/or thermoplastic fibers. As can be best seen by comparing Fig. 3 with Fig. 4, the fibers 6 of the nonwoven fabric sheet element 1 shown in Fig. 3 are less densely packed than the fibers 6 of the nonwoven fabric sheet element 1 ofthe enthalpy exchanger element shown in Fig. 4.

Fig. 4 shows a SEM micrograph of a cross-sectional view of a portion of an enthalpy exchanger element E produced by forming the laminated sheet element 1 of Fig. 3 into a desired shape exhibiting a three-dimensional corrugation pattem as a resuit of step c) of the method according to the invention.

The forming step c) may be a pleating step or thermoforming step, preferably a

Λ vacuum forming step. At least a first mold part (e.g. lower tool, not shown) having first corrugation formations defining or co-defining the predetermined corrugation pattem of the enthalpy exchanger element E, E’ to be manufactured, is provided for and used in the thermoforming step. In addition to the at least first mold part, a second mold part (e.g. upper tool, not shown) having second corrugation formations complementary to the first corrugation formations and/or a forming vacuum codefining the predetermined corrugation pattem of the enthalpy exchanger element E, E’ to be manufactured, may be provided in the thermoforming step.

The first mold part (e.g. lower tool) may comprise nozzles or through holes pneumatically connected to a vacuum source providing a vacuum for the vacuum forming step.

In addition to the first mold part and/or the second mold part used in the forming step c), preferably for supporting the vacuum action in the vacuum forming*step, nozzles connected to a pressurized air source may be provided. These nozzles may be provided in the vicinity of, preferably adjacent to, the first mold part and/or the second mold part. Preferably, the pressurized air source comprises an air heating device for heating the pressurized air.

«i

The combined use of the first tool and the vacuum source in the thermoforming step c) can be supplemented by the second tool and/or the pressurized air source, preferably with air heating device. As a resuit, using at least some of these suppléments, a sheet element 1 laminated with a first thin polymer film 3 and an optional second thin polymer film 4 can be pressed more strongly against thé first corrugation formations of the first mold part, thus producing an enthalpy exchanger element E with a better copy of the first corrugation formations of the first mold part defining or co-defining the predetermined corrugation pattern of the enthalpy exchanger element E to be manufactured.

*

The sheet element 1 of the enthalpy exchanger element E has its fibers 6 much more densely packed than the sheet element 1 of Fig. 3. During the pleating or thermoforming step c), the fabric sheet element 1 with its first thin polymer film 3 and its second thin polymer film 4 is compressed and heated. At least the thermoplastic fibers or the multicomponent or bicomponent fibers of the plurality of fibers 6 are softened or partly melted during the pleating or thermoforming step c). As a resuit, after cooling and hardening of the thermoplastic fibers or the multicomponent or bicomponent fibers of the plurality of fibers 6, the fabric sheet element 1 with its first thin polymer film 3 and its second thin polymer film 4 is transformed into an enthalpy exchanger element E according to the invention with a more compact fiber structure in the fabric sheet element 1 and with a threedimensional corrugation pattern.

Fig. 5 shows a SEM micrograph similar to the one of Fig. 3 showing of a larger scale cross-sectional view of a smaller portion of the air-permeable fabric sheet element 1 laminated on its upper side la with the first thin .polymer film 3 and laminated on its lower side lb with the second thin polymer film 4 as a resuit of step

b) of the method according to the invention.

A

Fig. 6 shows a SEM micrograph similar to the one of Fig. 4 showing of a smaller scale cross-sectional view of a larger portion of the enthalpy exchanger element E produced by the method according to the invention.

!» *

Reference numerals:

fabric sheet element la first surface lb second surface voids or openings first thin polymer film second thin polymer film corrugation a squeezed portion

5b squeezed and/or stretched portion providing step laminating step forming step (co-forming)

O air fiow direction towards viewer

X air fiow direction away from viewer fiber a angle (in corrugation pattern)

Claims (19)

1. A method for producing enthalpy exchanger éléments (E, E’) comprising the steps of:

a) providing an air-permeable sheet element (1);

b) laminating at least one side (la, lb) of the sheet element (1) with a thin polymer film (3,4) with water vapor transmission characteristics;

c) forming the laminated sheet element (1) into a desired shape exhibiting a three-dimensional corrugationpattern (5, 5,...).

A

2. The method according to claim 1, wherein the sheet material of the sheet element (1) comprises a polymer.

3. The method according to claim 1 or 2, wherein the sheet element (1) is a fabric, preferably a nonwoven fabric. *

4. The method according to claim 3, wherein a fraction, preferably at least 50% by weight, of the fibers (6) of the fabric are multi-component, preferably bi-component fibers.

*

5. The method according to any of claims 1 to 4, wherein the laminating step b) comprises at least one of bonding, preferably heat bonding, welding and gluing, of the thin polymer film (3,4) to the sheet element (1).

6. The method according to any one of claims 1 to 5, wherein the at least one thin polymer film (3, 4) on the at least one side (la, lb) of the sheet element (1) is an airimpermeable polymer film.

7. The method according to any of claims 1 to 6, wherein the thin polymer film (3, 4) is a multilayer film comprising a sequence of polymer layers of different polymer types.

8. The method according to claim 7, wherein the polymer type of each polymer layer is selected from the group consisting of polyether ester, polyether amide and polyether urethane.

9. The method according to claim 7 or 8, wherein the total thickness of the thin polymer multilayer film is between 5 pm and 200 pm, more preferably between 10 * pmandl50pm.

10. The method according to any of claims 7 to 9, wherein the thickness of each individual polymer layer within the thin polymer multilayer film is between 1 pm and 20 pm, preferably between 4 pm and 20 pm, and more preferably between 4 pm «» and 15 pm.

11. The method according to any of claims 1 to 10, wherein the forming step c) is a thermoforming step, preferably a vacuum forming step or a pleating step.

12. The method according to claim 11, wherein at least a first mold part having first corrugation formations defining or co-defining the predetermined corrugation pattern of the enthalpy exchanger element (E, E’) to be manufactured, is provided for and used in the thermoforming step c).

13. The method according to claim 12, wherein a second mold part having second corrugation formations complementary to the first corrugation formations codefining the predetermined corrugation pattern of the enthalpy exchanger element (E, E’) to be manufactured, is provided for and used in the thermoforming step c).

14. The method according to any of claims 10 to 13, wherein nozzles connecteà to a pressurized air source provided for and used in the thermoforming step c).

15. The method according to claim 14, wherein the nozzles are provided in the vicinity of the first mold part and/or the second mold part.

16. An enthalpy exchanger element (E; E’), preferably produced using the method as defined in any of claims 1 to 15, including an air-permeable sheet element (1) and a predetermined three-dimensional corrugation pattern (5, 5, ...), wherein a first thin polymer film (3) is laminated to a first side (la) of the sheet element (1) and/or a second thin polymer film (4) is laminated to a second side (lb) of the sheet élément (1), both thin polymer films (3,4) having water vapor transmission characteristics.

17. The enthalpy exchanger element (E) according to claim 16, wherein the first thin polymer film (3) and the second thin polymer film (4) are identical to each other.

Λ

18. The enthalpy exchanger element (E’) according to claim 16, wherein the first thin polymer film (3) and the second thin polymer film (4) are different from each other.

t

19. An enthalpy exchanger having at least three sheet-like or plate-like enthalpy exchanger éléments (El, E2, E3; ΕΓ, E2’, E3’) as defined in any of claims 16 to 18, which are stacked onto and fixed to each other, preferably by means of welding such as laser welding or ultrasonic welding or by means of gluing, with their respective three-dimensional corrugation patterns (5, 5, ...) in parallel orientation to^form parallel fluid paths allowing fluids to flow there through.