Elastocaloric machine and corresponding method for operating such an elastocaloric machine

Abstract

The invention relates to an elastocaloric machine (1), preferably for operation as a heat pump or chiller in a heating or cooling circuit, comprising: a fluid guidance element (2) in which at least one channel (K) is formed which is configured to guide a fluid (F) in the direction (X) of the channel extension, an elongated elastocaloric element (31) taken up in the channel (K) along its channel extension direction (X), wherein the fluid guidance element (2) is configured to vary a channel cross-section with respect to a channel section for applying or relieving force on the elongated elastocaloric element (31) in such a way that the elastocaloric element (31) undergoes a change of state from a first state in which the elastocaloric element (31) releases heat energy to the fluid (F) and a second state in which the elastocaloric element (31) absorbs heat energy from the fluid (F) to the other state in which the first state and the second state.

Description

[0001] The invention relates to an elastocaloric machine, preferably for operation as a heat pump or refrigeration machine in a heat or refrigeration circuit, for example in the form of an air conditioning system in a motor vehicle.

[0002] Such elastocaloric machines traditionally use elastocaloric elements made of elastocaloric materials, particularly so-called shape memory alloys (SMA). In such pseudoelastic alloys, a significant deformation can be induced by the introduction of heat. If the alloy releases the heat by removing the heat source, the metal returns to its original shape. This effect is completely reversible. Along with this, the reverse effect, the so-called elastocaloric effect, is utilized. Through a change in the shape of the elastocaloric material, the heat of transformation of the elastocaloric material is exchanged with the environment, so that the elastocaloric material can assume a lower energy state after exchanging heat energy with the environment than before the heat energy exchange.

[0003] Specifically, to apply and utilize the elastocaloric effect, the elastocaloric material is subjected to mechanical stress, resulting in a crystalline phase transformation and heating. This resulting heat is dissipated, for example, via a heat sink, so that the material cools back to its initial temperature. If the mechanical stress is then removed, i.e., the material relaxes, the order decreases, and the material cools even below its initial temperature, allowing it to absorb thermal energy from the environment.

[0004] By cyclical loading and unloading of the elastocaloric material, appropriate heat supply and removal can be achieved in the sense of an elastocaloric heat pump. By appropriately controlling the cyclic loading and unloading, combined with appropriate control of a fluid circuit, which may contain a coolant such as water, a heat pump or refrigeration machine can be realized using the elastocaloric machine.

[0005] The introduction of mechanical forces onto the elastocaloric elements made of elastocaloric material in order to load or stretch them accordingly is conventionally carried out via two corresponding and opposing clamping devices, via which tensile stresses of up to 1000 MPa can be applied.

[0006] The elastocaloric elements made of elastocaloric material or the wires of the wire bundles can be designed in the form of, for example, thin strips, tubes or round wires, with the intention of providing the largest possible elastocaloric volume with the largest possible surface area of ​​the elastocaloric material for heat dissipation and heat absorption.

[0007] Such two corresponding clamps hold and move an elastocaloric element within a channel of the elastocaloric machine that carries a fluid and is usually designed in the form of a cylindrical shell or a hollow cylinder. By stretching, the elastocaloric element is brought into a first state in which the elastocaloric element releases heat energy to the fluid due to the elastocaloric effect, and upon relaxation into a second state in which the elastocaloric element absorbs heat energy from the fluid due to the elastocaloric effect.

[0008] As initially explained, corresponding elastocaloric machines are intended for use in the automotive environment. However, the systems described above require too much installation space and have an inadequate power-to-weight ratio (ratio of the mass of the elastocaloric machine to the provided heating or cooling power) for their intended application. Furthermore, high forces are applied to the elastocaloric elements during the tensile loading process. Due to the design of the elastocaloric elements in the form of thin wires or strips, the high tensile load acts on a correspondingly small cross-section. Over time, this leads to fatigue of the elastocaloric material, which can lead to tearing or failure of the elastocaloric elements in the field / during operation of the elastocaloric machine, thus resulting in a loss of efficiency or even failure of the elastocaloric machine.

[0009] The document DE 102020214000 A1 discloses a centrifuge, in particular a laboratory centrifuge, comprising a rotor rotatably mounted in the interior of a rotor chamber, which rotor is designed to accommodate sample vessels, a drive motor for rotating the rotor, and a cooling device designed to dissipate heat from the interior of the rotor chamber via a coolant. The cooling device is designed to utilize the elastocaloric effect and has at least one cooling unit comprising an elastocaloric material arranged between a counter-block and a plunger. The plunger is designed to periodically apply a force to the elastocaloric material and then allow the elastocaloric material to relax again. The cooling device is designed to transfer heat both from the elastocaloric material to the coolant and from the coolant to the elastocaloric material.

[0010] The non-patent literature of the Fraunhofer Institute for Physical Measurement Techniques IPM: Elastocaloric Systems - Efficient Cooling Systems without Harmful Refrigerants. 08 / 2019, available e.g. at https: / / www.ipm.fraunhofer.de / content / dam / ipm / de / PDFs / produktblaetter / TE / KAS / Elastokalorik-kaeltemittelfreie-kuehlsysteme.pdf, discloses an elastocaloric system in which elastocaloric material is subjected to such a pressure that the material's inherent elastocaloric effect can be utilized for heat transfer purposes.

[0011] Against this background, the object of the present invention is to provide an elastocaloric machine that offers an alternative concept for loading the elastocaloric elements and, at the same time, can be implemented more compactly. Furthermore, a method for operating such an elastocaloric machine is to be provided.

[0012] This object is achieved by the features of the independent claims. Advantageous embodiments and further developments of the invention emerge from the dependent claims.

[0013] The elastocaloric machine according to the invention is preferably intended for operation as a heat pump or refrigeration machine in a heat or refrigeration circuit and comprises: a fluid guide element in which at least one channel is formed which is configured to guide a fluid in the channel extension direction thereof, an elongate elastocaloric element accommodated in the channel along the channel extension direction thereof, wherein the fluid guide element is configured to vary a channel cross-section with respect to a channel section for applying or relieving force to the elongate elastocaloric element such that the elastocaloric element experiences a change of state from a first state in which the elastocaloric element releases heat energy to the fluid and a second state in which the elastocaloric element absorbs heat energy from the fluid to the respective other state from the first state and the second state.

[0014] By applying a force to the elastocaloric element in the elastocaloric machine according to the invention by changing the channel cross-section, loading is not achieved by stretching, as in the prior art, but by applying pressure or compression in the transverse direction of the elongated elastocaloric element. This is advantageous in that the load acts on the elastocaloric element along its longitudinal direction and is not exerted on a small cross-section of the elastocaloric element, as in the prior art.

[0015] Preferably, the cross-sectional area of ​​a space formed between the channel and the elastocaloric element, which is filled with the fluid for heat transfer, is as large as possible or smaller than the cross-sectional area of ​​the elastocaloric element. This allows the elastocaloric machine to be designed smaller or more compactly and preferably requires less space.

[0016] According to the invention, the fluid guide element is designed to vary the channel cross-section by a force application element forming a movable channel wall section being mounted in the fluid guide element so as to be movable transverse to the channel extension direction relative to a fixed channel wall section, so that the elastocaloric element can be loaded or unloaded upon movement of the force application element in its transverse direction in order to effect the change of state.

[0017] Furthermore, the elastocaloric machine according to the invention can be realized in such a way that a spring element which is arranged in the channel opposite the force application element and is designed to apply a spring force to the elastocaloric element, which counteracts a force applied by the force application element or resulting from the force application.

[0018] Furthermore, the elastocaloric machine according to the invention can be implemented in such a way that the force application element is formed from a plurality of sub-elements arranged next to one another in the channel extension direction, which are movable independently of one another in the transverse direction.

[0019] Furthermore, the elastocaloric machine according to the invention can be realized in such a way that the fluid guide element has a carrier body of cylindrical shape, the channel extension direction corresponds to an axial direction of the fluid guide element or the carrier body, and the force application element is mounted so as to be movable in the radial direction with respect to the carrier body.

[0020] Furthermore, the elastocaloric machine according to the invention can be further developed such that the cylindrical support body has a groove extending in the axial direction and open in the radial direction, which forms the fixed channel wall section, and the force application element forming the movable channel wall section is mounted so as to be movable in the radial direction within the open groove.

[0021] Furthermore, the elastocaloric machine according to the invention can be such that the housing accommodates the fluid guide element rotatably mounted relative to the housing, wherein the housing and the fluid guide element are designed such that a relative rotation leads to a movement of the force application element for loading or unloading the elastocaloric element.

[0022] Preferably, the fluid guide element is stationary, and the housing is rotatably mounted around the fluid guide element. Alternatively, the housing can be stationary, and the fluid guide element can be rotatably mounted within the housing.

[0023] Furthermore, the elastocaloric machine according to the invention can be developed in such a way that the relative rotation leads to a cyclic loading and unloading of the elastocaloric element.

[0024] Furthermore, the elastocaloric machine according to the invention can be designed such that the housing forms a control surface on its inner wall and the force application element has a force application surface which is in contact with the elastocaloric element, and further has a cam surface which, during relative rotation, is in contact with the control surface of the housing such that the force application surface loads and unloads the elastocaloric element.

[0025] The control surface is preferably formed such that it varies a radial distance from a circumferential surface of the carrier body, i.e., from the inner wall of the housing to the circumferential surface of the carrier body. For example, the carrier body and the housing can be arranged concentrically to one another, with the housing forming a section on the inner wall in the circumferential direction that protrudes radially toward the carrier body and reduces the radial distance from the circumferential surface. Alternatively, the change in the distance can also be achieved by arranging the carrier body and the housing eccentrically with respect to one another.

[0026] Furthermore, the elastocaloric machine according to the invention can be realized in such a way that the force application area is smaller than the cam area.

[0027] In this way, a transmission ratio of a force acting from the control surface onto the cam surface to a force acting from the force application surface onto the elastocaloric element can be set or provided.

[0028] Furthermore, the elastocaloric machine according to the invention can be developed such that a plurality of channels are formed in the fluid guide element, through which the fluid can flow in series and / or in parallel, and the elastocaloric machine further comprises a controller which is configured to control a flow of the fluid such that the fluid is guided in series and / or in parallel through the respective channels.

[0029] The control is preferably formed by a valve system configured to control the supply and discharge of the fluid residing in the channels in accordance with the loading and / or unloading of the elastocaloric elements accommodated in the channels. In particular, the control can be formed by (valve) plates provided on the end faces of the housing. The (valve) plates are preferably rotatable relative to the fluid guide element and each have a hole pattern, wherein holes in the hole pattern can be brought into positions communicating with the channels and / or into positions separating communication with the channels by rotation.

[0030] The method according to the invention for operating an elastocaloric machine for exchanging heat energy with a fluid is preferably intended for operation as a heat pump or refrigeration machine in a heat or refrigeration cycle, wherein the elastocaloric machine comprises: a fluid guide element in which at least one channel is formed, which is designed to guide a fluid in the channel extension direction, an elongated elastocaloric element accommodated in the channel along its channel extension direction, the method comprising the following steps: Guiding a fluid in the channel in the direction of its channel extension, and varying a channel cross-section with respect to a channel section for applying or relieving force to the elongated elastocaloric element such that the elastocaloric element undergoes a change of state from a first state in which the elastocaloric element releases heat energy to the fluid and a second state in which the elastocaloric element absorbs heat energy from the fluid to the respective other state from the first state and the second state.

[0031] As a result, the properties and advantages explained in connection with the elastocaloric machine according to the invention result in the same or similar way, which is why reference is made to the above statements to avoid repetition.

[0032] Preferred embodiments of the invention are explained below by way of example with reference to the figures. Fig. 1 shows a schematic representation of an elastocaloric machine according to the invention in cross section according to a first embodiment of the invention; Fig. 2 (A) and (B) show enlarged sections of the Fig. 1 shown cross section of the elastocaloric machine according to the first embodiment of the invention; Fig. 3 (A) and (B) show side views of the elastocaloric machine 1 according to the first embodiment and a second embodiment of the invention; Fig. 4 (A) and (B) show enlarged sections of a cross section of an elastocaloric machine according to a third embodiment of the invention; Fig. 5 shows a section of a longitudinal section of the elastocaloric machine according to a fourth embodiment of the invention; and Fig. 6 (A) to (D) illustrate exemplary configurations that can be achieved in an elastocaloric machine according to the fourth embodiment of the invention by dividing the force application element in the channel extension direction.

[0033] Fig. Figure 1 shows a schematic cross-sectional view of an elastocaloric machine 1 according to the invention, according to a first embodiment of the invention. In this case, the elastocaloric machine 1 is configured to operate as a heat pump or refrigeration machine in a heating or refrigeration circuit (not shown in detail).

[0034] The elastocaloric machine 1 comprises a fluid guide element 2 and a housing 3.

[0035] The Fig. 1, the Z-direction shown is a height direction, the X-direction shown is a depth direction, and the Y-direction shown is a width direction of the elastocaloric machine 1.

[0036] In the illustrated first embodiment, the fluid guide element 2 comprises a carrier body 10, a plurality of elongate force application elements 21 to 28, a plurality of elongate elastocaloric elements 31 to 38 and a plurality of spring elements 41 to 48.

[0037] The support body 10 is cylindrical in shape and has an axial direction corresponding to the depth direction (X direction). In the first embodiment, the cylindrical support body 10 has a circular base.

[0038] The carrier body 10 comprises a plurality of grooves 11 to 18 open in its radial direction. These multiple open grooves 11 to 18 each extend in the axial direction (X-direction) over the entire carrier body 10 and protrude into the carrier body 10 in the radial direction with a specific groove depth. Furthermore, these multiple open grooves 11 to 18 are preferably evenly distributed in a circumferential direction of the carrier body 10 over its lateral surface M.

[0039] The Fig. 2 (A) and (B) show enlarged sections of the Fig. 1 shows a cross-section of the elastocaloric machine 1 according to the first embodiment of the invention. In these enlarged sections, only the part of the cylindrical support body 10 with the open groove 11 is shown.

[0040] The open groove 11 forms an elongated cavity with a rectangular cross-section, open in the axial direction towards the lateral surface M, and comprises a bottom surface 111 (groove base) and two opposing guide surfaces 112 and 113 (groove walls) running parallel to one another.

[0041] The plurality of elongated force-applying elements 21 to 28 also extend along the depth direction (X-direction) and are shaped such that they are each movably inserted, at least in sections, in the radial direction into the cavity formed by the open grooves 11 to 18. The following explanations regarding the interaction of a pairing of the open groove 11 and the force-applying element 21 also apply analogously to the respective other pairings.

[0042] As in the Fig. As shown in Figures 2 (A) and (B), the force-applying element 21, which is inserted into the open groove 11, has a rectangular cross-section. The force-applying element 21 comprises a force-applying surface 211, a cam surface 212, and two sliding surfaces 213 and 214.

[0043] The force application surface 211 faces the bottom surface 111 (groove base) and is accommodated within the cavity formed by the open groove 11. Furthermore, the force application surface 211, together with the sliding surfaces 213, 214, seals the open cavity from the outside environment. The cam surface 212 lies opposite the force application surface 211 and is not accommodated within the cavity formed by the open groove 11, but is offset radially outward with respect to the outer surface M of the cylindrical support body 10. In other words, the force application element 21, which is inserted radially movably into the groove 11, forms a projection with respect to the outer surface M.

[0044] The two sliding surfaces 213 and 214 are arranged parallel to each other and each connect the force application surface 211 to the cam surface 212. Furthermore, the sliding surfaces 213 and 214 each face at least partially toward one of the two guide surfaces 112 and 113 of the open groove 11. The two sliding surfaces 213 and 214 of the force application element 21 are further configured to slide along the guide surfaces 112 and 113 of the open groove 11 in such a way that the force application element 21 is mounted for movement in the radial direction within the cavity formed by the open groove 11, while the cavity is still sealed.

[0045] Thus, the open groove 11 and the force application element 21 together define a channel K. The channel K is preferably a cavity that is tightly sealed against the external environment and is designed to guide a fluid F to be cooled or heated along a channel extension direction.

[0046] In the Fig. 2 (A) and (B), a channel extension direction corresponds to the axial direction (X-direction), in which the open groove 11 also extends. Furthermore, the channel comprises a fixed channel wall section and a movable channel wall section. In the embodiment shown in the Fig. In the first embodiment shown in Figures 2 (A) and (B), the fixed channel wall section is formed by the bottom surface 111 (groove base) and the exposed sections of the guide surfaces 112 and 113 (groove walls). The exposed sections of the guide surfaces 112 and 113 are preferably formed by those sections that are not in contact with the sliding surfaces 213 and 214, respectively. The movable channel wall section, on the other hand, is formed by the force-applying surface 211.

[0047] By relative movement of the movable channel wall section relative to the fixed channel wall section, a channel cross-section of the channel K can be varied. In particular, the force application surface 211 can be moved in a direction toward the bottom surface 111 (groove base) in order to reduce the channel cross-section of the channel K (cf. Fig. 2 (A)), and in a direction away from the bottom surface 111 (groove base) in order to increase the channel cross-section of the channel K (cf. Fig. 2 (B)).

[0048] In the first embodiment, the plurality of elongated elastocaloric elements 31 to 38 are each formed in the form of a wire or a strip of elastocaloric material. Each of the plurality of elongated elastocaloric elements 31 to 38 is accommodated in a respective channel section of the channels K defined by the respective pairs of open grooves 11 to 18 and force-applying elements 21-28. In particular, each elastocaloric element 31 is accommodated in the channel K in such a way that the fluid F guided in the channel K flows around it.

[0049] Furthermore, the plurality of spring elements 41 to 48 are preferably also accommodated in the respective channels K. In particular, one of the spring elements 41-48 is accommodated in one of the respective channel sections of the channels K defined by the respective pairings of the open grooves 11 to 18 and the force application elements 21-28.

[0050] As in the Fig. 2 (A) and (B), the spring element 41 rests on the bottom surface 111 (groove bottom) of the open groove 11 and supports the elastocaloric element 31 in the channel K. However, the provision of the plurality of spring elements 41 to 48 is optional.

[0051] By changing the channel cross-section of the channel K, a change in the state of the elastocaloric element 31 accommodated therein can be brought about, which can be determined by the Fig. 2 (A) and (B) and is explained below.

[0052] If the force application surface 211 of the force application element 21, as in Fig. 2 (A), is moved in the radial direction toward the bottom surface 11 (groove base) - in other words, the channel cross-section is reduced - the force application surface 211 comes into contact with the elastocaloric element 31, if they are not already in contact. Upon further movement of the force application element 21, a force is applied to the elastocaloric element 31 via the force application surface 211. In this case, this force counteracts a spring force of the spring element 41, which increases until the spring element 41 is completely compressed. In this way, for example, manufacturing tolerances of the components forming the channel K or of the elastocaloric element 31 itself can be compensated.

[0053] When the spring force of the spring element 41 and the force applied by the force application element 21 act against each other in such a way that the elastocaloric element 31 is deformed or compressed, the elastocaloric element 31 is placed in a first state and releases heat energy to the fluid F.

[0054] In detail, the elastocaloric element 31 is elastically deformed due to the force applied in its transverse direction. This mechanical stress on the elastocaloric element 31 leads to a crystalline phase transformation, which results in heating of the elastocaloric element 31. The thermal energy of the elastocaloric element 31 can subsequently be absorbed and dissipated by the fluid F flowing around the elastocaloric element 31. In this way, the fluid F can be heated as it passes through the channel K.

[0055] If the force application surface 211, as in Fig. 2 (B), now moved in the radial direction away from the bottom surface 111 (groove base) - in other words the channel cross-section is increased -, a force relief of the elastocaloric element 31 takes place, ie the resulting force from the spring force and the force applied by the force application element 21 becomes continuously smaller, so that the elastocaloric element 31 is put into a second state, expands again accordingly in the transverse direction, and absorbs heat energy from the fluid F.

[0056] Specifically, the elastocaloric element 31 deforms elastically as a result of the unloading or expands elastically, as permitted by the interaction between the spring element 31 and the force-applying element 21. This leads to a phase transition, which results in a cooling of the elastocaloric element 31. The elastocaloric element 31 then absorbs heat from the surrounding fluid F, which is consequently cooled as it passes through the channel K. At the same time, the spring element 41 preferably also expands again and returns to its rebounded initial state.

[0057] The movement of the force application element 21 occurs through the interaction, explained later, of the cam surface 212 with a control surface S formed by the housing 3.

[0058] Furthermore, materials with a low thermal conductivity coefficient, preferably materials with a thermal conductivity coefficient between 0.001 and 0.1 W / (m K), are preferably used to form the channel wall sections. Alternatively, coatings with a corresponding thermal conductivity coefficient can also be applied to the corresponding channel wall sections. In this way, heat transfer from the fluid F or from the elastocaloric element 31 to the channel wall sections can be at least reduced. Furthermore, heat transfer between the respective channels K can also be prevented or at least reduced in this way.

[0059] The housing 3 is, as in Fig. 1, is arranged to receive the fluid guide element 2 and comprises a hollow cylinder H and two covers D1 and D2, as shown for example in Fig. 3 can be seen.

[0060] In Fig. 1 shows that the fluid guide element 2 is inserted in the axial direction (X-direction) into a cavity formed by the hollow cylinder H. The cylindrical support body 10 of the fluid guide element 2 and the hollow cylinder H of the housing 3 are arranged concentrically to one another, and the hollow cylinder H of the housing 3 is rotatably mounted about the fluid guide element 2. In addition, a drive (not shown) is provided, which is configured to drive the hollow cylinder H such that it rotates about the fluid guide element 2.

[0061] The hollow cylinder H forms at least in sections the control surface S. This control surface S is in the Fig. 1, is formed by the inner wall of the hollow cylinder H facing the carrier body 10. As indicated above, the movement of the force-applying element 21 occurs through an interaction of the cam surface 212 with the control surface S.

[0062] The control surface S is formed such that it varies a radial distance between the lateral surface M of the carrier body 10 and the inner wall of the hollow cylinder H. In particular, the control surface S has a loading section and a relaxation section in the circumferential direction, wherein the radial distance in the relaxation section is greater than in the loading section.

[0063] Furthermore, the control surface S is at least partially in contact with the cam surface 212 of the force-applying element 21. By rotating the hollow cylinder H around the support body 10, the cam surface 212 comes into contact with either the loading section or the relaxation section of the control surface S.

[0064] When the cam surface 212 comes into contact with the loading section of the control surface S, the radial distance between the outer surface M of the support body 10 and the inner wall of the hollow cylinder H decreases according to the inner radial profile of the loading cross-section, and the force-applying element 21 is moved in the radial direction toward the bottom surface 111 (groove base) of the open groove 11. As a result, the elastocaloric element 31 is placed in the first state. In other words, the elastocaloric element 31 is loaded while the cam surface 212 is in contact with the loading section of the control surface S.

[0065] Upon further rotation of the hollow cylinder H around the support body 10, the cam surface 212 leaves the loading section of the control surface S and comes into contact with the relaxation section of the control surface S. The radial distance increases accordingly, and the force-applying element 21 is moved radially away from the bottom surface 111 (groove base) according to the inner radial course of the relaxation section. As a result, the elastocaloric element 31 is placed in the second state. In other words, the elastocaloric element 31 is unloaded while the cam surface 212 is in contact with the relief section of the control surface S.

[0066] The other elastocaloric elements 32 to 38 can be loaded and unloaded in an analogous manner.

[0067] During several rotations of the hollow cylinder H around the support body 10 of the fluid guide element 2, the elastocaloric element 31 is cyclically loaded and unloaded. Furthermore, the fluid F, which is guided through the channel K during a loading cycle, is heated. Conversely, the fluid F, which is guided through the channel K during a unloading cycle, is cooled. This effect can be exploited, with appropriate control of the loading and unloading as well as the flow of the fluid F through the channels K, to operate the elastocaloric machine 1 as a heating or cooling machine. Corresponding options for controlling the flow of the fluid F are explained below.

[0068] The Fig. 3 (A) shows a side view of the elastocaloric machine 1 according to the first embodiment of the invention and illustrates by way of example a corresponding control of the flow of the fluid F.

[0069] The covers D1 and D2 are provided on the end faces of the hollow cylinder H and preferably seal off the cavity formed by the hollow cylinder H from the external environment. Furthermore, the covers D1 and D2 preferably comprise the control system configured to control the flow of the fluid F through the respective channels K of the fluid guide element 2.

[0070] In the Fig. In the first embodiment shown in Figure 3 (A), the fluid F is guided in series through several channels K1 to K3 with the aid of the controller.

[0071] On the cover D1, which is provided on one of the end faces of the hollow cylinder H, an inlet Z is formed, via which the fluid F can be introduced into the housing 3. In the example shown, this inlet Z communicates with a channel K1 defined by the fluid guide element 2. Furthermore, on the cover D2, which is provided on the other end face of the hollow cylinder H, an outlet A is formed, via which the fluid can be discharged from the housing 3. This outlet A communicates in the exemplary embodiment shown with a further channel K3 defined by the fluid guide element 2. Furthermore, connecting channels V1 and V2 are preferably formed in the respective covers D1 and D2. These connecting channels V1 and V2 respectively connect the channel K1 communicating with the inlet Z and the channel K3 communicating with the outlet, with a channel K2 lying between them in the direction of circulation.Thus, the fluid F can be guided from the inlet Z1 via the channel K1 and the connecting channel V1 into the channel K2 and then via the connecting channel V2 into the channel K3 and finally discharged via the outlet A. In other words, the fluid F can be guided in series through the channels K1, K2 and K3.

[0072] At the same time, the hollow cylinder H is rotated around the fluid guide element 2 such that the force application elements of the respective channels K1 to K3 load or unload the elastocaloric elements accommodated in the channels K1 to K3 according to the order in which the fluid F flows through them. Furthermore, the inlet Z and the outlet A preferably comprise a valve system configured to control the supply and discharge of the fluid F residing in the series-connected channels K1 to K3 in accordance with the loading and / or unloading of the elastocaloric elements accommodated in the channels K1 to K3.

[0073] Thus, the fluid F, which is guided in series through channels K1, K2, and K3, can gradually absorb or release heat several times. In this way, the difference between the temperature of the fluid F when it is fed in via inlet Z and the temperature of the fluid F when it is discharged via outlet A can be increased.

[0074] The Fig. 3 (B) shows analogous to the Fig. 3 (A) is a side view of the elastocaloric machine 1 according to a second embodiment of the invention and illustrates an alternative control of the flow of the fluid F by way of example. In the description of this second embodiment, only the differences from the first embodiment will be discussed, wherein identical or similar components are designated by the same reference numerals. Fig. In the second embodiment shown in Fig. 3 (B), the fluid F is guided in parallel through the plurality of channels K1 to K3.

[0075] In Fig. 3 (B) Several inlets Z1 to Z3 are provided on the cover D1. At the same time, several outlets A1 to A3 are provided on the other cover D2. Thus, the fluid F can be guided from the inlet Z1 via the channel K1 to the outlet A1. Likewise, the fluid F can be guided from the inlet Z2 via the channel K2 to the outlet A2 and from the inlet Z3 via the channel K3 to the outlet A3. In other words, the fluid F can be guided parallel through the channels K1, K2, and K3.

[0076] The fluid supply and discharge is preferably controlled by means of the inlets and outlets in such a way that the fluid F remaining in the respective channel is discharged in the course of a change in state of the elastocaloric element accommodated in the channel.

[0077] The Fig. 4 (A) and (B) show analogous to the Fig. 2 (A) and (B) show an enlarged section of a cross-section of an elastocaloric machine 1 according to a third embodiment of the invention. In the description of this third embodiment, only the differences from the first embodiment will be discussed, with identical or similar components being designated by the same reference numerals.

[0078] In this embodiment, the cam surface 212 of the force application element 21 is larger than its force application surface 211.

[0079] The force application element 21 is mushroom-shaped and has a head section which, as shown in Fig. 4 (A), is provided outside the open groove 11 and protrudes relative to the sliding surfaces 213 and 214, respectively. In this way, the cam surface 212 can be enlarged, thus providing a larger area in contact with the control surface S.

[0080] Specifically, a portion of the cam surface 212 that is in contact with the control surface S is larger in area than a portion of the force application surface 211 that is in contact with the elastocaloric element 31 during loading. In this way, a pressure transmission can be provided between the control surface S or the cam surface 212 and the force application surface 211.

[0081] Fig. Figure 5 shows a section of a longitudinal section through an elastocaloric machine 1 according to a fourth embodiment of the invention. The description of this fourth embodiment will again focus solely on the differences from the first embodiment, with identical or similar components again being designated by the same reference numerals.

[0082] In this embodiment, the force application element 21 is formed from a plurality of sub-elements T1, T2, T3, and T4 arranged side by side in the channel extension direction (X-direction). The plurality of sub-elements T1, T2, T3, and T4 move independently of one another in the radial direction within the open groove 11. Fig. 6 (A) to (D) illustrate exemplary configurations that can be achieved by independent movement of the sub-elements T1, T2, T3, and T4. In particular, in the configurations shown, the elastocaloric element 31 is subjected to force in the channel extension direction (X-direction) sequentially by the respective sub-elements T1, T2, T3, and T4. Thus, the elastocaloric element 31 is Fig. 6 (A) is first loaded by the sub-element T1. Subsequently, corresponding loads are applied by the sub-elements T2, T3 and T4, as shown in the Fig. 6 (B) to (D).

[0083] Furthermore, the control surface S is formed such that the respective loading and unloading sections for the respective sub-elements T1 to T4 are offset from one another in the circumferential direction. In this way, the above-explained movement of the sub-elements T1, T2, T3 and T4 can be realized.

[0084] Due to the above-described design of the force application element 21, the elastocaloric element 31 can be loaded or unloaded in sections in the channel extension direction (X-direction). At the same time, a pumping effect can be applied to the fluid F flowing through the channel K through successive radial movements of the sub-elements T1, T2, T3, and T4, so that the fluid F is conveyed through the channel K in the channel extension direction (X-direction). This may make the provision of an external pump for fluid guidance obsolete.

[0085] The features of the invention disclosed in the above description, in the drawings and in the claims may be essential for the realization of the invention both individually and in any combination.

Claims

[1] Elastocaloric machine (1), preferably for operation as a heat pump or refrigeration machine in a heat or refrigeration circuit, comprising: a fluid guide element (2) in which at least one channel (K) is formed, which is designed to guide a fluid (F) in the channel extension direction (X), an elongate elastocaloric element (31) accommodated in the channel (K) along its channel extension direction (X), wherein the fluid guide element (2) is configured to vary a channel cross-section with respect to a channel section for applying or relieving force to the elongate elastocaloric element (31) such that the elastocaloric element (31) undergoes a change of state from a first state in which the elastocaloric element (31) releases heat energy to the fluid (F) and a second state in which the elastocaloric element (31) absorbs heat energy from the fluid (F), to the respective other state from the first state and the second state, wherein the fluid guide element (2) is configured to vary the channel cross-section by a force application element (21) forming a movable channel wall section (211) being mounted in the fluid guide element (2) so as to be movable transverse to the channel extension direction (X) relative to a fixed channel wall section (111, 112, 113), so that the elastocaloric element (31) can be loaded or unloaded when the force application element (21) moves in its transverse direction in order to effect the change of state. [2] Elastocaloric machine (1) according to claim 1, further comprising: a spring element (41) which is arranged in the channel (K) opposite the force-applying element (21) and is designed to apply a spring force to the elastocaloric element (31) which counteracts a force applied by the force-applying element (21). [3] Elastocaloric machine (1) according to claim 1 or 2, wherein the force application element (21) is formed from a plurality of sub-elements (T1, T2, T3, T4) arranged next to one another in the channel extension direction (X), which are movable independently of one another in the transverse direction. [4] Elastocaloric machine (1) according to one of claims 1 to 3, wherein the fluid guide element (2) has a carrier body (10) of cylindrical shape, the channel extension direction (X) corresponds to an axial direction of the carrier body (10) and the force application element (21) is mounted so as to be movable in the radial direction with respect to the carrier body (10). [5] Elastocaloric machine (1) according to claim 4, wherein the cylindrical support body (10) has a groove (11) extending in the axial direction and open in the radial direction, which forms the fixed channel wall section (111, 112, 113), and the force-applying element (21) forming the movable channel wall section (211) is mounted so as to be movable in the radial direction within the open groove (111). [6] Elastocaloric machine (1) according to claim 5, further comprising: a housing (3) which receives the fluid guide element (2) rotatably mounted relative to the housing (3), wherein the housing (3) and the fluid guide element (2) are designed such that a relative rotation leads to a movement of the force application element (21) for loading or unloading the elastocaloric element (31). [7] Elastocaloric machine (1) according to claim 6, wherein the housing (3) and the fluid guide element (2) are designed such that the relative rotation leads to a cyclic loading and unloading of the elastocaloric element (31). [8] Elastocaloric machine (1) according to claim 6 or 7, wherein the housing (3) forms a control surface (S) on its inner wall, and wherein the force application element (21) has a force application surface (211) which is in contact with the elastocaloric element (31) and further has a cam surface (218) which, during relative rotation, is in contact with the control surface (S) of the housing (3) in such a way that the force application surface (211) loads and relieves the elastocaloric element (31). [9] Elastocaloric machine (1) according to claim 8, wherein the force application area (211) is smaller than the cam area (212). [10] Elastocaloric machine (1) according to one of claims 1 to 9, wherein a plurality of channels (K1, K2, K3) are formed in the fluid guide element (2), through which the fluid (F) can flow in series and / or in parallel, and the elastocaloric machine (1) further comprises a controller which is configured to control a flow of the fluid (F) such that the fluid (F) is guided in series and / or in parallel through the respective channels (K1, K2, K3). [11] Method for operating an elastocaloric machine (1) according to one of the preceding claims for exchanging thermal energy with a fluid (F), preferably for operation as a heat pump or refrigeration machine in a heat or refrigeration cycle, the elastocaloric machine (1) comprising: a fluid guide element (2) in which at least one channel (K) is formed, which is designed to guide a fluid (F) in the channel extension direction (X), an elongated elastocaloric element (31) accommodated in the channel (K) along its channel extension direction (X), the method comprising the following steps: Guiding a fluid (F) in the channel (K) in its channel extension direction (X) and Varying a channel cross-section with respect to a channel section for applying or relieving force to the elongated elastocaloric element (31) such that the elastocaloric element (31) undergoes a change of state from a first state in which the elastocaloric element (31) releases heat energy to the fluid (F), and a second state in which the elastocaloric element (31) absorbs heat energy from the fluid (F), to the other state of the first state and the second state.

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