ADSORBER STRUCTURE

Abstract

An adsorber structure for an adsorption heat exchanger may include directed transport structures for the transport of at least one of heat and adsorptive vapours. The transport structure may be substantially aligned with a gradient direction.

Claims

1. An adsorber structure for an adsorption heat exchanger, comprising directed transport structures for the transport of at least one of heat and adsorptive vapours, wherein the transport structures are substantially aligned in a gradient direction.

2. An adsorber structure according to claim 1, wherein the transport structures are formed by organic fibres that leave behind micro-vapour channels for transporting matter after a pyrolysis process.

3. An adsorber structure according to claim 2, wherein the organic fibres have the form of heat conducting fibres and are connected to a first surface of the adsorber structure, and the vapour channels are closed towards the first surface and are predominantly open to the outside atmosphere toward an opposite, second surface.

4. An adsorber structure according to claim 3, heat conducting fibres are made from at least one of carbon fibres, metal fibres, inorganic fibres or whiskers.

5. An adsorber structure according to claim 2, wherein an adsorber material is arranged between the organic fibres and the vapour channels.

6. An adsorber structure according to claim 3, wherein the organic fibres are substantially perpendicularly incident on the first surface.

7. An adsorber structure according to claim 2, wherein the organic fibres and the vapour channels extend predominantly parallel to each other.

8. An adsorber structure according to claim 2, wherein the organic fibres and the vapour channels are one of linear or serpentine in nature.

9. An adsorber structure according to claim 2, further comprising a first layer with a particle/binder mixture containing thermally conductive particles, and a second layer with a porous adsorbent powder and a binder, the second layer being adjacent to the first layer.

10. An adsorber structure according to claim 9, wherein the first layer is connected to the first surface and the second layer is connected to the second surface.

11. An adsorber structure according to claim 2, wherein the organic fibres are polymer-based fibres of one of polyamide, polyester or polyethylene.

12. An adsorber structure according to claim 11, wherein the organic fibres are made from at least one of polystyrene, SAN, polyamide (PA), PA 66, polycarbonate, polyester carbonate, aromatic polyesters (polyarylates), polyimides (PI), polyether imide (PEI), modified polymethacryl imide, poly-(N-methylmethacryl imide), PMMI, polyoxymethylene (POM), polyterephthalate (PETP, PBTP), copolymers of said polymers, polyethylene, polypropylene, or phenolic resin.

13. An adsorber structure according to claim 2, wherein the organic fibres are shorter than a thickness of the adsorber structure.

14. An adsorption heat exchanger comprising: an adsorber structure having directed transport structures for the transport of at least one of heat and adsorptive vapours, wherein the transport structures are substantially aligned in a gradient direction, and a heat exchanger element to which the adsorber structure is connected in a thermally conductive manner via fibres in the form of thermally conductive fibres.

15. A method for producing an adsorber structure, comprising: bonding fibres, made from at least one of a thermally conductive and pyrolysable material and aligned predominantly in a gradient direction of the produced adsorber structure, to an adhesive layer by electrostatic flocking, filling interstitial spaces between the individual fibres with a mixture of adsorbing and binder particles, converting the fibres into tubular vapour channels by a pyrolysis process, and sintering the adsorber structure to form a directed transport structure for transporting both heat and adsorptive vapours.

16. A method according to claim 15, wherein the interstitial spaces in two particle layers of different compositions are filled out, specifically with a first layer having a particle/binder mixture with high proportions of thermally conductive particles, and with a second layer adjacent thereto and having highly porous adsorbent powder and a binder.

17. A method according to claim 15, wherein the adsorber structure is compacted.

18. An adsorber structure according to claim 1, wherein the adsorber structure is produced by extruding.

19. An adsorber structure according to claim 18, wherein the adsorber structure is compressed such that vapour channels created by at least one of organic and inorganic fibres, or left behind following a pyrolysis process, are reduced in terms of cross section.

20. An adsorber structure according to claim 9, wherein the thermally conductive particles are made from expanded at least one of graphite, graphite powder, BN, SiC and AlN.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In the drawing, the figures represent diagrammatically:

[0029] FIG. 1 a cross section through an adsorber structure according to the invention, with enlarged details of the area of a first and a second surface,

[0030] FIG. 2 a representation as in FIG. 1, but with transport structures extending at an angle to the respective surfaces resulting from shearing compaction,

[0031] FIG. 3 a representation as in FIG. 2, but with serpentine transport structures resulting from vertical compaction,

[0032] FIG. 4 a representation as in FIG. 3, but with a two-layer adsorber structure,

[0033] FIG. 5 an adsorber structure according to the invention produced by an extrusion process,

[0034] FIG. 6 an adsorber structure according to the invention having extruded vapour channels, produced by an extrusion process.

DETAILED DESCRIPTION

[0035] As shown in FIGS. 1 to 4, an adsorber structure 1 according to the invention includes transport structures 15 for transporting heat and adsorptive vapours, wherein transport structures 15 are formed by organic and/or inorganic fibres 2 and/or the vapour channels left behind thereby after a process of pyrolysis, and are essentially aligned in gradient direction 4. Fibres 2 have the form of thermally conductive fibres and are connected to a first surface 5 of the adsorber structure 1, whereas vapour channels 3 are closed towards first surface 5 and at least partially open towards an opposite, second surface 6 of the adsorptive vapour chamber, as is illustrated particularly clearly in the enlarged representation of FIG. 1. An adsorber material 7, for example activated carbon, is arranged between the individual fibres 2 and vapour channels 3. Upon examination of FIG. 1, it may be seen that fibres 2 as well as the vapour channels 3 created therefrom by the pyrolysis process are substantially perpendicular to first surface 5 at their point of incidence therewith. As with the adsorber structures 1 shown in FIGS. 2 to 5, fibres 2 and the vapour channels 3 are incident on first surface 5 and also on the opposite, second surface 6 at an angle. Fibres 2 may thus be made from non-pyrolysable thermally conductive fibres as well pyrolysable organic fibres, which largely disintegrate in the pyrolysis process, thus leaving behind the vapour channels 3. Given a relatively dense arrangement of fibres 2 and thus also of vapour channels 3, high sorption kinetics, that is to say low-loss transport of heat and vapours may be achieved.

[0036] The inclined alignment of fibres 2 and vapour channels 3 may be an unintended but tolerable side effect of a shearing, compacting compression of adsorber structure 1, carried out to increase the density and mechanical strength of the adsorber structure. The individual fibres 2 and the vapour channels 3 created therefrom are preferably aligned substantially parallel to each other, so that with an appropriate choice of the fibre mass fractions in the compound, each adsorbing particle is arranged not only as closely as possible to a thermally conductive fibre 2 but also as closely as possible to a vapour channel 3.

[0037] In general, adsorber structure 1 is connected directly or indirectly to a heat exchanger element 10, particularly a wall of an adsorption heat exchanger 13, for example a sorption heat pump or a sorption refrigeration plant, via an adhesive layer 9. However a purely non-positive thermal attachment of the adsorber structure to the wall of an adsorption heat exchanger 13 is conceivable instead of adhesive layer 9.

[0038] In order to produce the adsorber structure 1 illustrated in FIGS. 1 to 4, chopped fibres for example, made from a highly thermally conductive and/or readily pyrolysable material may be bonded, particularly vertically, to an adhesive surface, in this case adhesive layer 9, by electrostatic flocking, which may be carried out particularly inexpensively using a throughput flocker, for example. It should be noted that the primary adhesive layer for use in the flocking process does not necessarily have to be identical to the adhesive layer used for bonding the structure to heat exchanger wall 13. It may also be in the form of a self-adhesive foil or similar, for example, which is peeled off and thrown away after one of the method steps that will be described later.

[0039] In a second process step following the flocking process, the interstitial spaces of the lawn created from upright fibres 2 is filled with a mixture of adsorbent and binder particles. A number of known application methods are suitable for this purpose, to ensure that the bulk density of the composites of adsorber structure 1 that are to be produced thereby is as high as possible. In this context, vibration, blowing, brushing and/or slurrying methods of a dry or aqueous mixture may be cited. The density of the thermal contact and/or the strength of the composite may be increased yet further by various compaction processes, for example by compacting either perpendicularly or at an angle, whereby particularly the adsorber structures 1 shown diagrammatically in FIGS. 2 to 4 may be produced.

[0040] According to FIG. 2, the thermal connection between adsorber structure 1 and heat exchanger wall 13 may also be established by a non-positive contact, although the adsorber structures 1 according to FIG. 1 as well as FIGS. 3 and 4 have an adhesive layer 9 that is highly thermally conductive and/or thin.

[0041] A consideration of the adsorber structure 1 according to FIG. 4, reveals that it is divided into two layers 11 and 12. First layer 11 contains a higher, or very high proportion of thermally conductive particles 8, preferably consisting of expanded graphite or graphite powder, BN, SiC, or AlN. In this content, a high content may mean>30 M.-%. Second layer 12 contains a large proportion of highly porous adsorbent powder and a binder, on the basis of alumosilicates, for example. In the lowest area of adsorber structure 1, which creates the thermal contact with heat exchanger surface 5, the powder mixture to be introduced into the interstitial spaces between the fibres thus has a higher proportion of readily thermally conductive particles 8 for the purpose of improving the thermal contact between thermally conductive fibres 2 and surface 5, that is to say the contact surface with a later wall of heat exchanger element 10. The interstitial spaces between the fibres above this layer preferably have high proportions of highly porous adsorbent powder and a binder, to obtain high adsorption capacity. High proportions of adsorbent powder means mass fractions greater than 50%, preferably greater than 75%. In order to improve processability, the mixture may contain still further auxiliary substances. Because of the elevated content of thermally conductive auxiliary substances, that is to say thermally conductive particles 8 in first layer 11, a larger contact area and considerably improved thermal bonding of fibres 2 to wall 10 is possible. The dry or aqueous two-layer composite mass of adsorber structure 1 may undergo further treatment by compacting, cutting, drying, possibly removing adhesive layer 9, and sintering to create finished adsorption bodies, which in a final process are bonded in known manner to form a thermally conductive force-fit or adhesive connection with heat exchanger element 10. Since it is possible for all process steps to be performed automatically in the plane of the contact surface in an endless loop passthrough system, extremely low manufacturing costs may be achieved.

[0042] FIG. 4 shows a further design variant of adsorber structure 1, in which fibres 2 that are considerably shorter than the thickness of adsorber structure 1 are use. These fibres may be in the form of chopped fibres with uniform length or also as milled fibres with a certain length variation. Through an extrusion process in the thickness direction, that is to say in gradient direction 4, according to experience in producing fibre composite materials in which shearing and stretching forces are exploited by accelerating the extrudate in a conical die, said fibres 2 are predominantly aligned in this direction. In this context, the aligning effect may be enhanced further by dividing the external cross section into smaller conical exit cross sections and implementing shearing meshes and the like upstream. In order to create thermal contactability, an adsorber structure 1 produced in this way must be cut into slices perpendicularly to the extrusion direction, that is to say perpendicularly to gradient direction 4. When a pasty or thixotropic mass is created, this is easily possible with the aid of a cutting wire, for example. The fibres 2 that are introduced may be selected in terms of composition, material, mass fractions and geometry such that optimally balanced heat and matter transport is established in the final, sintered state.

[0043] The following substances are particularly suitable for producing the fibres 2 that leave behind the vapour channels 3 following pyrolysis and/or sintering: polymer-based fibres of polyamide, polyester or polyethylene. Polymers such as polystyrene and SAN, polyamides (PA) such as PA 66, polycarbonate and polyester carbonate, aromatic polyesters (polyarylates), polyimides (PI) such as polyether imide (PEI) or modified polymethacryl imide (poly-(N-methylmethacryl imide), PMMI), polyoxymethylene (POM) and polyterephthalate (PETP, PBTP), also copolymers of said polymers and polyethylene, polypropylene and phenolic resins can be pyrolysed particularly readily. With regard to the thermally conductive fibres 2, PAN- or pitch-based carbon fibres are particularly preferred, but highly metal or ceramic fibres and whiskers with good thermal conductivity are also suitable.

[0044] A further variant of the manufacturing method based on the extrusion process consists in extruding a mixture that contains the thermally conductive fibres 2, the adsorber material 7 and the binder, and optionally additional auxiliary substances and in which the transport channels, that is to say the vapour channels 3 are created by the tool during the extrusion process. Moreover, the vapour channels 3 created by the extrusion process may be reduced in cross section, as shown in FIGS. 6b and 6c, defining the body of adsorber structure 1 by moulding and/or compacting it while it is still pasty and can be kneaded and moulded to yield a defined final geometry, before or after cutting to length. FIG. 6a shows the vapour channels 3 before they are deformed. For example, a channel structure or transport structure 15 may be created that is generated by squeezing or plastic reshaping of a honeycomb structure with square channels 3, having a channel width of 1.17 mm and a wall thickness of 330 m, corresponding to a cell density of 300 cells/inch.sup.2. Depending on the direction of the subsequent reshaping, vapour channels 3 may be narrowed considerably to an optimum dimension (FIG. 6, c). In this context, vapour channels 3 may also be reshaped to form rhomboids. With these measures, an optimal combination of high vapour diffusion capacity and high volume-specific adsorbent mass may be reached.

[0045] The adsorber structure 1 according to the invention with fibres 2 and vapour channels 3 created therefrom by pyrolysis is capable of improving sorption kinetics significantly. As a result, the cycle time may be shortened correspondingly for unchanged driving temperature and pressure differentials, thereby increasing the power density of adsorber structure 1 and of the system, and thus enabling the construction size and system costs to be lowered. At the same time or alternatively, the driving differentials may be reduced for the same cycle time thereby significantly enhancing the plant's coefficient of performance (COP).

[0046] With a shortened cycle time and the correspondingly increased power density of sorption modules, it becomes possible to expand the potential application range, including into the automotive sector, with its extremely constricted installation space requirements. The greater power density also contributes to reducing consumption of valuable resource such as the adsorber material 7, steel, and stainless steel.