Elastocaloric energy converter unit

Abstract

The invention relates to an elastocaloric energy converter unit (10) for heating and cooling a medium (16), comprising: a housing for receiving the medium (16), an elastocaloric element (12) arranged in the housing, which is designed to be in heat transfer contact with the medium (16), and a collection device (20) arranged in the housing and at least partially around the elastocaloric element (12), which is designed to collect at least a fragment (22) of the elastocaloric element (12) in the event of a defect of the elastocaloric element (12).

Description

[0001] The present invention relates to an elastocaloric energy converter unit, in particular an elastocaloric energy converter unit for heating and cooling a medium.

[0002] Elastocaloric energy conversion units, which can also be referred to as thermoelastic energy conversion units, can achieve a heating or cooling effect through cyclic mechanical deformation and relaxation of a thermoelastic element, such as a shape memory alloy element. When a mechanical deformation stress is applied, the thermoelastic elements typically undergo a phase transition, particularly a crystal lattice transformation. Due to the thermoelastic effect, the thermoelastic elements release latent heat during stressing and absorb latent heat during relaxation. This released or absorbed heat can be used to achieve a heating or cooling effect.

[0003] However, it has been shown that elastocaloric elements cannot be tensioned and relaxed indefinitely. For example, it has been shown that if the elastocaloric element is tensioned / relaxed sufficiently frequently, material fatigue can occur in the elastocaloric element, which can lead to the elastocaloric element becoming defective and, in the worst case, to fatigue fracture.

[0004] The object of the present invention is therefore to provide an elastocaloric energy converter unit which enables safe operation of the energy converter unit, in particular even in the case of defective elastocaloric elements.

[0005] This object is achieved by the elastocaloric energy converter unit according to claim 1. Further embodiments of the invention are the subject of the dependent claims.

[0006] According to one aspect of the present invention, an elastocaloric energy converter unit for heating and cooling a medium is provided. The energy converter unit comprises: a housing for accommodating the medium; an elastocaloric element arranged in the housing, which is designed to be in heat-transfer contact with the medium, in particular to be flowed around by the medium; and a collecting device arranged in the housing and at least partially around the elastocaloric element, which is designed to collect at least a fragment of the elastocaloric element in the event of a defect in the elastocaloric element.

[0007] The present invention is based, in part, on the recognition that elastocaloric elements can become defective due to excessive stress and generate fragments that can impair the smooth operation of the energy conversion unit. The invention is based, at least in part, on the recognition that these fragments can be collected by means of a collecting device within the housing that carries the medium of the elastocaloric machine. The invention is based, at least in part, on the recognition that such collection of the fragments within the collecting device promotes the safe and smooth operation of the energy conversion unit, since the fragments can neither be carried away by the medium nor become entangled or caught with other components of the energy conversion unit.

[0008] In the context of this disclosure, the term "elastocaloric element" refers to an element made of an elastocaloric material, for example, nitinol, which releases or absorbs latent heat during cyclic mechanical stress and relaxation due to the elastocaloric effect. This released or absorbed heat can then be used for heating or cooling applications via heat transfer contact with the medium located in the housing. In the device according to the invention, a collecting device extending at least partially around the elastocaloric element is located within the housing, i.e., in the space through which the medium flows. This collecting device collects fragments of the elastocaloric element. The elastocaloric element can have various forms. For example, the elastocaloric element can be in the form of a wire, strip, rod, or the like.The elastocaloric element is preferably a thin wire with a diameter and / or cross-section adapted to the specific application of the elastocaloric energy conversion unit. The collecting device collects fragments of the defective elastocaloric element. The defective elastocaloric element can crack, for example, due to material stress during cyclic tensioning and relaxation. The crack results, for example, in an elastocaloric element that was a single piece before the defect, consisting of at least two parts after the defect. A part of the elastocaloric element resulting from the defect in the elastocaloric element can thus be referred to as a fragment.Elastocaloric elements are typically mechanically mounted and held at predetermined sections, particularly end sections, in such a way that tension and relaxation of the elastocaloric element is possible. A defect in an elastocaloric element mounted in this way leads, for example, to the elastocaloric element no longer being continuous between the predetermined sections, particularly end sections, because a crack, particularly a fracture, has occurred in the elastocaloric element on the path between the predetermined sections. A fragment within the meaning of this disclosure can therefore also be understood to mean that part of the elastocaloric element which has no connection between two mounted sections, but rather has at least one loose end, i.e., an end that is no longer mounted in the elastocaloric energy converter unit.However, it is also conceivable that the elastocaloric element is defective in such a way that a section of the elastocaloric element has no connection whatsoever to the holding sections of the elastocaloric element. In other words, in such a defect, the elastocaloric element, which was a single-piece element before the defect, would have at least three parts after the effect. A part with two loose ends is also referred to as a fragment in the context of this disclosure.

[0009] The purpose of the collecting device proposed here is to collect fragments of the elastocaloric element, whether fragments with one or more loose ends, and thereby keep them at a predetermined location inside the collecting device.

[0010] Preferably, the collecting device is arranged at least partially in a tubular or tubular manner around the elastocaloric element. This preferred embodiment is based at least partially on the realization that fragments within the meaning of this disclosure may, for example, have only one loose end, and that these fragments can become entangled during operation of an energy converter unit, in particular during rotation of the elastocaloric elements. By arranging the collecting device at least partially in a tubular or tubular manner around the elastocaloric element, the loose end is caught and held inside the collecting device, thus preventing the loose end from becoming entangled.

[0011] Preferably, the collecting device is arranged at least partially around a plurality of elastocaloric elements, and the collecting device is designed to collect at least a fragment of one or more of the elastocaloric elements. This preferred embodiment is based at least in part on the realization that a plurality of elastocaloric elements can be combined as a bundle in the energy converter unit. A collecting device according to this preferred embodiment thus extends at least partially around a bundle of elastocaloric elements. If, in such a case, one or more elastocaloric elements of this bundle were to be defective, fragments of one or more of the elastocaloric elements of this bundle would be collected within the collecting device.The advantage of a collecting device per bundle, i.e. around several elastocaloric elements, is the lower material and assembly costs for the collecting device compared to one collecting device per elastocaloric element.

[0012] Preferably, the collecting device is formed at least partially from a metallic and / or textile material and / or a plastic material. This preferred embodiment is based at least in part on the finding that such materials typically exhibit high tear resistance. In other words, a collecting device formed from one or more such materials is highly unlikely to be destroyed by fragments of the elastocaloric elements. This ensures that, particularly in the case of multiple defective elastocaloric elements, the fragments can be safely and reliably collected inside the collecting device without destroying the collecting device.

[0013] It is particularly advantageous if the collecting device is a knitted, woven, or braided fabric. This special design is based at least in part on the realization that knitted, woven, or braided fabrics exhibit a certain degree of extensibility. Extensibility is important as soon as the elastocaloric element is stretched, since the collecting device may also be stretched, for example, because the collecting device and the elastocaloric element are mounted or clamped in the same sections. Knitted, woven, or braided fabrics also have the advantage of being permeable to liquids and / or gases, in particular permeable to the heat transfer medium of the elastocaloric energy conversion unit.In addition, knitted, woven, or braided fabrics typically exhibit low flow resistance, which has little to no impact on energy efficiency during heat transfer between the elastocaloric element and the medium. Knitted, woven, or braided fabrics can also be easily and cost-effectively adapted to the specific application, for example, in terms of diameter and / or length.

[0014] Furthermore, regardless of the material and shape of the collecting device, it is advantageous if the collecting device has at least one opening for the medium to flow through. It is particularly advantageous if these openings are arranged in a lateral surface of the collecting device. This preferred embodiment is based at least in part on the finding that many elastocaloric energy converter units incorporate elastocaloric elements, particularly wire-shaped elastocaloric elements, which are subjected to radial flow.If the collecting device extends in particular in the axial direction around the elastocaloric element, it is advantageous if the lateral surface (i.e. the surface radially surrounding the elastocaloric element) of the collecting device has one or more openings so that the medium flowing in the radial direction can flow through the one or more openings of the collecting device and can thus be in direct heat exchange with the elastocaloric element.

[0015] An independent aspect of the present invention provides a method for producing a system from an elastocaloric element with a collecting device that surrounds it at least in part, the method comprising the following steps: producing an elastocaloric element, and at least partially surrounding the elastocaloric element with a collecting device, wherein the collecting device is preferably hose- or tubular and surrounds the elastocaloric element at least in part in a hose- or tubular manner. The two steps preferably take place simultaneously, in particular if the production of the elastocaloric element comprises drawing a wire made of elastocaloric material. In such a case, the collecting device can be drawn over a section of the wire or over the entire wire during the drawing of the wire (or optionally thereafter).

[0016] Further features and objects of the present invention will become apparent to those skilled in the art upon application of the present teachings and upon consideration of the accompanying drawings. Fig. 1 a schematic view of an embodiment of an elastocaloric energy converter unit according to the invention, Fig. 2 a schematic view of another embodiment of the elastocaloric energy converter unit according to the invention, and Fig. 3 a schematic view of another embodiment of the elastocaloric energy converter unit according to the invention.

[0017] Elements with the same function or construction are provided with the same reference symbols throughout the figures.

[0018] It is initially Fig. 1, which shows an embodiment of an elastocaloric or thermoelastic energy converter unit 10 according to the invention. The elastocaloric energy converter unit 10 has several elastocaloric or thermoelastic elements 12. In the specific example of Fig. 1, the elastocaloric elements 12 are designed in the form of wires. The elastocaloric elements 12 are mechanically mounted and held in two clamping devices 14. The clamping devices 14 can be moved relative to one another, in particular in the axial direction of the thermoelastic elements 12, such that the elastocaloric elements 12 are cyclically tensioned and relaxed, whereby latent heat is released or absorbed. The elastocaloric elements 12 are in heat transfer contact with a heat-conducting medium 16, which can also be referred to as a heat transfer medium. The medium 16 can be liquid or gaseous, depending on the application of the energy conversion unit 10. In the specific example of Fig. 1, the medium flows in a radial direction (indicated by the arrow 18) past the elements 12, whereby heat is transferred between the elements 12 and the medium 16.

[0019] As in Fig. 1, some of the elements 12 have collecting devices 20. In the specific example of Fig. 1 shows three elastocaloric elements 12, two of which are each surrounded by a collecting device 20. In the specific example of Fig. 1, the collecting device 20 of a respective elastocaloric element 12 extends in a hose-like or tubular manner around the element 12. In the specific example of Fig. 1, the respective collecting device 20 also extends over the entire length of the elastocaloric element 12. In other embodiments not shown, the number, arrangement and position of the collecting device 20 can of course be different.

[0020] The collecting device 20 serves to collect fragments of defective, particularly cracked, elements 12 and to retain them within the collecting device 20. This is intended to prevent fragments of the elements 12 from being carried away, for example, by the medium 16 or from becoming caught or tangled in other (not shown) components of the energy converter unit 10. It is also conceivable that fragments of the elements 12 become entangled with other elements 12 (or their fragments), which is prevented by the collecting device 20. Examples are shown in Fig. 1, four fragments 22 are indicated in the middle elastocaloric element 12. Of course, the shape and size of the fragments 22 vary from case to case. The concrete example of Fig. 1 therefore only serves to illustrate one of many possible examples of fragments of an elastocaloric element 12.

[0021] The collecting device 20 can be made of a metallic, textile, or plastic material, or combinations thereof. The material of the collecting device 20 is selected such that fragments 22 of the elastocaloric elements 12 cannot destroy the collecting device 20. In the specific example of Fig. 1, the collecting device 20 is also attached to the clamping devices 14 of the elastocaloric elements 12. In such a case, it must be ensured that the collecting device 20 is extensible at least to the extent that the clamping devices 14 are movable relative to one another to act on the thermoelastic elements 12. In other embodiments not shown, it is conceivable that the collecting device 20 is mounted differently. Knitted fabrics, woven fabrics, or braids have the advantage that they have a certain extensibility and are easily adaptable to the respective application. The knitted fabrics, woven fabrics, or braids do not have to be formed from a textile material. For example, it is conceivable to use a material and shape analogous to stents known from medicine. However, plastic fabrics, such as those known as plastic meshes, can also be used as the collecting device 20.

[0022] It is now on Fig. 2, which shows a further embodiment of the energy converter unit 10. In the embodiment according to Fig. 2, the collecting device 20 extends around a plurality of elastocaloric elements 12. In elastocaloric energy converter units 10, a plurality of elastocaloric elements 12 are typically combined to form a bundle of elastocaloric elements 12, particularly in the case of wire-shaped elastocaloric elements 12. Fig. 2 is intended to show an example of such a bundle. In the concrete embodiment of Fig. 2, such a bundle of elastocaloric elements 12 is surrounded by a collecting device 20. In the specific example of Fig. 2, two elastocaloric elements 12 of the bundle are also defective. In the specific example of Fig. 2, six fragments 22 are indicated, which are collected by the collecting device 20. The shape, material and type of the collecting device 20 of Fig. 1 may be determined by the shape, material and type of the collecting device Fig. 2. In the concrete example of Fig. 2, the medium 16 again flows in a radial direction, although this does not necessarily have to be the case.

[0023] After all, it is Fig. 3, which shows a further embodiment of the energy converter unit 10. In the specific example of Fig. 3, the collecting device 20 is designed as a tubular or pipe-shaped mesh. This shape is strongly reminiscent of the previously mentioned shape of a stent in the medical field, but has several surprising effects, particularly as a collecting device 20 for the energy converter unit 10. Thus, the collecting device 20 in the embodiment according to Fig. 3 in the axial direction of the elastocaloric elements 12 due to the honeycomb structure. Furthermore, the collecting device 20 has a plurality of openings, of which Fig. 3, three openings are indicated by reference numeral 24. The openings 24 are located in a lateral surface of the collecting device 20, i.e., in the radial direction around the elastocaloric elements 12. The plurality of openings 24 has several effects. Firstly, the openings 24 allow the medium to flow through. Secondly, the plurality of openings 24 results in a comparatively low flow resistance, which has a particularly advantageous effect on the efficiency of the energy converter unit 10. The honeycomb design of the collecting device 20 also has the advantage of sufficient flexibility and tear resistance, so that the Fig.3 indicated fragments 22 can be collected without destroying the collecting device 20.

[0024] Further useful designs of the collecting device 20 are conceivable.

[0025] The elastocaloric energy converter unit 10 can be used in particular as an air conditioning system, further in particular as an air conditioning system in the vehicle sector.

Claims

[1] Elastocaloric energy converter unit (10) for heating and cooling a medium (16), comprising: - a housing for holding the medium (16), - an elastocaloric element (12) arranged in the housing, which is designed to be in heat transfer contact with the medium (16), and - a collecting device (20) arranged in the housing and at least partially around the elastocaloric element (12), which is designed to collect at least one fragment (22) of the elastocaloric element (12) in the event of a defect in the elastocaloric element (12). [2] Elastocaloric energy converter unit (10) according to claim 1, wherein the collecting device (20) is at least partially tubular or hose-shaped. [3] Elastocaloric energy converter unit (10) according to one of the preceding claims, wherein the collecting device (20) is arranged at least partially around a plurality of elastocaloric elements (12) and is designed to collect at least one fragment (22) of one or more of the elastocaloric elements (12). [4] Elastocaloric energy converter unit (10) according to one of the preceding claims, wherein the collecting device (12) is formed at least partially from a metallic and / or textile material and / or from a plastic material. [5] Elastocaloric energy converter unit (10) according to one of the preceding claims, wherein the collecting device (20) is a knitted fabric, woven fabric or braid. [6] Elastocaloric energy converter unit (10) according to one of the preceding claims, wherein the collecting device (20) has at least one opening (24) for the medium (16) to flow through. [7] Elastocaloric energy converter unit (10) according to claim 6, wherein the opening (24) is arranged in a lateral surface of the collecting device (20).

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