Shape memory alloy heat pump

Abstract

The present invention relates to a heat pump comprising at least one stack of Shape Memory Alloy (SMA) plates stacked one on top of the other. Each of the SMA plates, except for the end plates, has a plurality of fluid ports machined therethrough. The fluid ports allow fluid to pass through the stack. Fluid is introduced into the SMA plates through an inlet port and discharged out of the stack through an outlet port. At least one of the SMA stacks includes an SMA core, the SMA core being located within a housing. Optionally, the housing is configured with a plurality of buckling supports to keep the SMA plates intact and aligned when a compressive load is applied.

Description

[Technical Field]

[0001] The present disclosure relates to a shape memory alloy heat pump. [Background technology]

[0002] Heat pump (HP) technology is widely used commercially in Heating, Ventilation and Air Conditioning (HVAC-R) applications, offering energy savings and emissions reductions, and is typically deployed for heating and cooling systems in buildings, vehicles, etc.

[0003] Heat pumps using shape memory alloy (SMA) tubes are well known in the art. SMA refers to an alloy that retains its shape when deformed by an external force at temperatures below a critical temperature, but regains its original shape after heating to the critical temperature through its shape recovery effect. SMAs, such as titanium-nickel alloys, are manufactured at high temperatures to have a predetermined shape.

[0004] U.S. Patent Application Publication No. 20160084544 (Radermacher et al.) discloses a heat pump system using SMA material tubes, which are filled with tubes or rods of unknown material to occupy a volume, thus helping to eliminate dead thermal mass and increase the efficiency of the system. However, a problem with this configuration is that the SMA tubes are thermally inefficient and do not expand and / or contract uniformly. Furthermore, the tubes have the disadvantage of buckling during use. U.S. Patent Application Publication No. 20120273158 (Cui et al.) discloses a system that twists bundles of SMA wire to release heat. This system also has the disadvantage of being inefficient and buckling during operation. Other patent publications in this field include U.S. Patent No. 5,339,653 (DeGregoria) and U.S. Patent Application Publication No. 2013 / 139538, assigned to Fujitsu, which disclose heat pumps in general.

[0005] Therefore, there is a need for a heat pump that is resistant to buckling and / or has high thermal efficiency, which constitutes an object of the present invention. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention relates to a heat pump comprising at least one stack of plates made from SMA, as set out in the accompanying claims. [Means for solving the problem]

[0007] In one embodiment of the present invention, there is provided a heat pump device comprising at least one stack of plates, at least two plates are formed of a shape memory alloy and assembled together, and the plurality of shape memory alloy plates have one or more fluid ports adapted to allow passage of a fluid through the stack; at least one plate is dimensioned to have an inlet port for introducing fluid into the stack; A heat pump device is provided in which at least one plate is dimensioned to have an outlet port for discharging fluid introduced through the inlet port to the exterior.

[0008] In one embodiment, the plates are assembled in a stack, each plate having a number of fluid ports machined therethrough to allow the passage of a fluid at a particular temperature through the stack. The fluid is introduced into the stack through an inlet port, and after passing through the stack, the fluid is expelled to the outside through an outlet port.

[0009] In a preferred embodiment of the present invention, the inlet and outlet ports are independent structural units and are formed using the same SMA as that used to make the plates, and further, at least one stack of SMA plates comprises an SMA core.

[0010] In accordance with a preferred embodiment of the present invention, the SMA stack is located within a housing having a plurality of buckling supports adapted to keep the stack plates intact and aligned during application of a load.

[0011] In one embodiment, the composition of the SMA forming each of the plurality of stacked plates is the same. In another embodiment of the invention, the composition of the SMA forming at least one plate is different from the composition of the other plates in the stack.

[0012] In another embodiment of the invention, multiple SMA stacks are located within a housing, and the composition of the SMA forming the plates in one SMA stack is different from the composition of the SMA forming the stacked plates in another SMA stack.

[0013] The present invention increases the surface area of the SMA material that comes into contact with the fluid. Furthermore, as the fluid in the stack passes through the stack, it only comes into contact with the SMA material, reducing overall heat loss. Some of the fluid that passes outside the SMA stack may come into contact with the housing.

[0014] In one embodiment, a notch or cutout in the periphery of at least one plate defines an exit port.

[0015] In one embodiment, the intake port and the outlet port are separate structural units.

[0016] In one embodiment, the inlet and outlet ports are formed from a shape memory alloy.

[0017] The construction of the inlet and outlet ports using SMA materials further reduces heat loss. The stack formation described in this invention resists buckling, reducing the need for external supports.

[0018] The housing ensures that the SMA plates are thermally isolated, and the housing and buckling supports ensure that the SMA plates can withstand hydraulic loads while also allowing movement of individual plates or stacks under compression. The present invention also allows for easy retrofitting of heat pumps, as it is easy to replace one SMA stack with another.

[0019] This means that as better SMA compositions become available, it is easy to replace stacks having plates formed from older SMA compositions with stacks having plates formed from the newer, improved SMA compositions.

[0020] In one embodiment, at least one stack of a plurality of plates, at least two plates being formed of a shape memory alloy and assembled in a stack, the plurality of shape memory alloy plates having a plurality of serpentine fluid ports adapted to allow passage of a fluid through the stack; an intake port adapted to introduce fluid into the stack; an outlet port adapted to discharge the fluid introduced through the intake port to the outside; wherein the intake port and the outlet port are formed of a shape memory alloy.

[0021] It will be understood that there are a series of flow ports in the plates that allow fluid to flow through the stack. This flow path can be single pass, multiple pass, serpentine or spiral, or multiple spiral or serpentine flow paths. A serpentine flow path is the preferred embodiment.

[0022] In another embodiment, at least one stack of a plurality of plates formed of a shape memory alloy and assembled in a stack, the plurality of shape memory alloy plates having at least one fluid port adapted to allow the passage of a fluid through the stack; an intake port adapted to introduce fluid into the stack; an outlet port adapted to discharge the fluid introduced through the intake port to the outside; wherein the intake port and the outlet port are formed of a shape memory alloy.

[0023] In a further embodiment there is provided a device for use in a heat pump, said device comprising at least one stack of a plurality of plates; at least two plates are formed of a shape memory alloy and assembled together, and the plurality of shape memory alloy plates have one or more fluid ports adapted to allow passage of a fluid through the stack; at least one plate is dimensioned to have an inlet port for introducing fluid into the stack; At least one plate is dimensioned to have an outlet port for discharging fluid introduced through the intake port to the exterior. [Brief explanation of the drawings]

[0024] The invention will be more clearly understood from the following description of embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: [Figure 1a] 1 is a perspective view of a preferred embodiment of the present invention; [Figure 1b] 1 shows an enclosure with fluid inlet and outlet ports that houses a heat pump according to an embodiment of the present invention. [Figure 2] FIG. 1 is a front view of a preferred embodiment of the present invention. [Figure 3] 1 shows several different views of an SMA plate according to the present invention. [Figure 4] Figure 4a shows an exploded view of a heat pump according to one embodiment of the present invention, and Figure 4b shows an assembled view of a heat pump according to one embodiment of the present invention. [Figure 5] Figure 5a shows an exploded view of a heat pump made up of multiple stacked SMA plates according to another embodiment of the present invention, and Figure 5b shows an assembled view of a heat pump made up of multiple stacked SMA plates according to another embodiment of the present invention. [Figure 6] Figure 6a shows an exploded view of a heat pump made up of multiple stacked SMA plates according to a further embodiment of the invention, and Figure 6b shows an assembled view of a heat pump made up of multiple stacked SMA plates according to a further embodiment of the invention. [Figure 7] 7 shows a cutaway cross section of the heat pump embodiment of FIG. 6 to illustrate serpentine flow, according to another embodiment of the present invention. [Figure 8] Figures 8(a) to 8(d) show multiple cascade arrangements of heat pumps. DETAILED DESCRIPTION OF THE INVENTION

[0025] The operation of heat pumps using SMA materials is known and fully described in PCT Patent Application Publication No. WO2019 / 149783, which is assigned to the assignee of the present invention and is hereby incorporated by reference in its entirety.

[0026] FIG. 1a shows a perspective view of a preferred embodiment of the present invention. The disclosed heat pump device includes at least one stack of multiple plates 101 formed from SMA and assembled in a stacked or side-by-side configuration. Each of the multiple plates 101 has multiple fluid ports 102 machined therethrough. The fluid ports 102 are designed to allow the passage of fluid through the stack of plates 101. The stack of plates 101 is adapted to absorb heat and store energy or release heat as fluid passes through the plates 101, and further includes multiple plate reinforcement slots 103. The plate reinforcement slots 103 allow for the insertion of rigid rods to resist buckling when the stack is compressed during operation. The slots 103 can be on the order of a few millimeters in diameter and the length of the stack, and the size can be selected based on the desired design. Ideally, two or more rods are used to maintain the integrity of the stack and prevent the plates from sliding relative to each other during use. Additionally, the rods prevent the plates from rotating. 1b is an exemplary enclosure in which the stack / core is disposed. A fluid, e.g., water, at a particular temperature is introduced or injected into the chamber containing the stack / core through one inlet 104, and the fluid exits at 105. An exemplary operation of the heat pump is described in the aforementioned PCT Patent Application Publication No. WO2019 / 149783. It will be understood that the SMA heat pump as described hereinabove can preferably be operated using compressive or tensile forces.

[0027] Regarding the shape and arrangement of the stack, the inlet port is adapted to introduce fluid into the stack, and the outlet port is adapted to discharge the fluid introduced through the inlet port to the outside. At least one plate is dimensioned to have an inlet port for introducing fluid into the stack, and at least one other plate is dimensioned to have an outlet port for discharging the fluid introduced through the inlet port to the outside, and the inlet port and outlet port are formed of a shape memory alloy. The inlet port and outlet port are independent structural units and can be made using the same SMA material as the stack of multiple plates to minimize heat loss. Fluid ports 102 machined in each plate allow for a significant increase in the surface area of the plate exposed to the fluid and also ensure that the fluid only contacts the SMA material, reducing overall heat loss. The fluid ports can be constructed in any geometric pattern, such as a lattice, circular, or polygonal pattern, as described in more detail below.

[0028] The SMA plate 101 in the illustrated embodiment is substantially rectangular in shape. The SMA plate can be considered a basic building block for building scaled stacks, cores, and heat pump systems. The plate stack structure allows for easier modular design, so that heat pumps of various shapes and sizes can be easily constructed. The plate design is a function of heat transfer optimization, and the illustrated embodiment is merely indicative. Smaller plates and stacks can also be used for scaling down using the same principles.

[0029] Figure 2 shows a front view of another embodiment of the present invention. In the illustrated view, a stack of SMA plates 101 forming an SMA core or heat pump device is located within a housing 201. The housing 201 has at least one buckling support 202 to keep the SMA stack intact when a load is applied. When compressive forces are applied to an SMA heat pump, optimizing the location, size, and number of buckling supports is important to estimate the amount of force that can be exerted without collapsing the structure. This ensures optimal use of the heat-generating properties of SMA. The housing 201 ensures that the SMA plates are thermally isolated, and the housing and buckling support 202 ensure that the SMA plates 101 can withstand hydraulic loads while also allowing movement of individual plates or stacks under compression. Ideally, two or more rods are used to maintain the integrity of the stack and prevent the plates from sliding relative to each other during use. Additionally, the rods prevent the plates from rotating. As shown in Figure 1b, a heat pump embodiment can be incorporated within the housing.

[0030] In another embodiment of the invention, the composition of at least one plate in a stack of SMA plates is different from the composition of the other plates in the stack, and different SMA blends are used for different SMA plates within a single stack.

[0031] Another embodiment of the invention uses an SMA core with multiple SMA stacks, where each stack is made up of plates with a different SMA composition than the other stacks, meaning that plates within the same stack have the same SMA composition.

[0032] Another embodiment of the invention uses multiple stacks, each stack having multiple SMA plates, each stack having at least one SMA plate with an alloy composition that is different from the alloy composition of the other plates in the same stack.

[0033] Figure 3 shows several different views of SMA plates 301-306 according to the present invention, with the openings being of any size or shape depending on the heat pump design specifications. It will be understood that the shape memory alloy plates can be substantially rectangular or square in shape, as shown. The plates can also be any 2D shape, including circular and hexagonal. The various openings or slots configured on each plate can be selected depending on the required application. By selecting the specific shape and dimensions of the slot or slots for a particular application, an optimal heat transfer design can be achieved. Optimization can be calculated using finite element analysis using known thermodynamic modeling techniques. For example, the openings in each plate can have curved edges or sloped inner walls to optimize heat transfer depending on the heat pump application.

[0034] Figures 4a and 4b show exploded and assembled views of a heat pump constructed with multiple stacked SMA plates according to one embodiment of the present invention. The SMA plates can be considered as building blocks for constructing a scaled core and heat pump system. The plate design is a function of heat transfer optimization, and the illustrated sample is merely indicative. Smaller plates and stacks can also be used to scale using the sample principle. Various actuation means, including hydraulic and electrical, can be used for specific applications. Figure 4 shows three plate assemblies 400, 401, and 402. For plate 401, a notch or cutout defines an inlet port 403 through which fluid can enter and exit at an outlet port, which is essentially a duplicated inlet port at another location, typically the opposite end of the stack. Slots 404 allow optional support or reinforcing rods to be inserted (not shown).

[0035] 5a and 5b show exploded and assembled views of a heat pump constructed of multiple stacked SMA plates according to another embodiment of the present invention. In this heat pump, a notch or finger 500 on the periphery of one plate defines an inlet port 500 through which fluid can enter. A notch or finger 501 on the periphery of at least one plate defines an outlet port 501. Fluid can enter at the inlet 500, travel through the stack to contact the SMA plates, and exit at an outlet port, which is essentially the inlet port replicated in a separate location, typically at the opposite end of the stack. Note that in this embodiment, only a single slot 502 is provided for engaging a support rod and is shown in the center of the plate. Additional notches 503 and 504 can be made around the periphery, allowing additional support rods to be easily positioned to secure the heat pump.

[0036] Figures 6a and 6b show exploded and assembled views of a heat pump constructed with multiple stacked SMA plates similar to the embodiment of Figure 5 according to a further embodiment of the present invention. As shown in this design, there are three slots 600, 601, and 602 to allow for the insertion of support slots. Variable-sized notches or fingers 603 are made in the periphery of one or more of the SMA plates to define multiple inlets. The inlets, along with other openings provided in plates 605 and 606, are sized to allow efficient heat transfer between the fluid and the SMA material. Plate 604 has multiple openings to provide flow ports to allow fluid flow through the plate stack. The outlet port is essentially the inlet port replicated at a separate location, typically at the opposite end of the stack, where the fluid exits the stack.

[0037] Figure 7 shows a cutaway cross-section of the heat pump embodiment of Figure 6 to illustrate serpentine flow, according to another embodiment of the present invention. As shown by the arrows, serpentine flow can be achieved whereby fluid enters one end of the stack and travels up and down the length of the plate stack through a series of flow paths before exiting at the opposite end of the stack. Multiple different flow paths can be provided, determined by a series of cutouts in the plates.

[0038] In the context of the present invention, it will be understood that the particular plate size may be selected depending on the particular application of the heat pump required. There is a wide range of physical plate dimensions, with the following size ranges for each SMA plate being preferred: Length range: 5mm~150mm Width range: 5mm~150mm Height range: 0.5mm~150mm Material area: 80% to 40% opening area range Ideally a 1:1 ratio, with a maximum length-to-width ratio of 5:1

[0039] FIGS. 8(a)-8(d) show multiple cascade arrangements of a heat pump according to another embodiment of the present invention. Cascading of SMA plates, which can be used to increase Delta-T, can be achieved using multiple solutions. For example, FIG. 8a shows an intra-stack arrangement with optimized SMA plates of different blends used in a single stack, with Blend 1, Blend 2, and Blend 3 plates arranged in a single stack. FIG. 8b shows a multi-stack version of FIG. 8a. Stacks of plates, each with multiple SMA blends, interact with other stacks of plates with similar or different SMA blends in the multi-stack arrangement. For example, an intra-stack cascade arrangement interacts with different or similar intra-stack cascade arrangements in series in the multi-stack arrangement. FIG. 8c is a multi-stack version of FIG. 8b. Stacks of plates, each with the same SMA blend, interact with other stacks of plates with different SMA blends. For example, a Blend 1 stack interacts with a Blend 2 stack (and so on) in series in the multi-stack arrangement. Figure 8d shows a multi-core arrangement, where cores constructed with either Multi-Stack Version 1, Multi-Stack Version 2, or a combination of both interact together in series to form a cascade. The different types of SMA stacks shown in Figure 8 have different latent heats. The cascaded blend results in an increase in delta temperature throughout the heat pump.

[0040] In the context of the present invention, it will be understood that the following definitions apply throughout the specification. Plate - An individual SMA plate with one or more fluid ports machined into the plate to allow fluid flow through the plate. Stack - multiple SMA plates comprising at least two plates assembled together. Enclosure - Containment vessel for the stack of plates. Provides thermal isolation and fluid inlet / outlet. Core - Mechanically, it can consist of a single stack or multiple stacks that are axially aligned and loaded in series.

[0041] As used herein, the terms "comprise, comprise, comprised, and comprising" or any variation thereof, and the terms "include, includes, included, and including" or any variation thereof, are considered to be fully interchangeable and all of them should be given the broadest possible interpretation, and vice versa.

[0042] The invention is not limited to the embodiments described hereinabove, which may be varied in both structure and detail.

Claims

1. A heat pump having a shape memory alloy (SMA) core, The SMA core is at least one stack of a plurality of plates, at least two of the plates being formed of a shape memory alloy and assembled together; having one or more fluid ports adapted to allow the passage of fluid through the stack; Further, each plate includes a plurality of reinforcing slots, the reinforcing slots of each plate being positioned in alignment with respective reinforcing slots of adjacent plates, such that when the reinforcing slots are aligned, they can receive supports or reinforcing rods; at least one plate is dimensioned to have an intake port for introducing the fluid into the stack; At least one plate is dimensioned to have an outlet port for discharging the fluid introduced through the intake port to the outside.

2. The heat pump of claim 1 , wherein the composition of at least one shape memory alloy plate is different from the composition of other shape memory alloy plates of the plurality of shape memory alloy plates.

3. 3. The heat pump of claim 1 or 2, wherein a notch or cutout in the periphery of the at least one plate defines the intake port.

4. 4. A heat pump according to claim 1, wherein a notch or cutout in the periphery of the at least one plate defines the outlet port.

5. The heat pump according to claim 1 , wherein the suction port and the outlet port are formed of a shape memory alloy.

6. The heat pump of claim 1 , wherein the plurality of shape memory alloy plates are substantially rectangular, square, 2D shaped, circular, or hexagonal in shape.

7. 7. The heat pump of claim 1, wherein the fluid port defines a serpentine shape to define a flow path for the fluid.

8. The housing and at least one shape memory alloy core located within the housing, the shape memory alloy core including at least one stack of a plurality of plates formed of a shape memory alloy, the plurality of plates having a plurality of fluid ports adapted to allow passage of a fluid through the shape memory alloy core, the plurality of plates formed of a shape memory alloy further including a plurality of reinforcing slots, the reinforcing slots of each plate being aligned with respective reinforcing slots of adjacent plates; an intake port adapted to introduce the fluid into the shape memory alloy core; an outlet port adapted to discharge the fluid introduced through the intake port to the outside; Equipped with At least one buckling support rod adapted to keep the plurality of plates intact during application of a compressive load is inserted into the aligned reinforcing slots.

9. 10. The heat pump of claim 8, wherein at least one shape memory alloy core has at least one shape memory alloy plate having a different composition compared to the composition of other shape memory alloy plates of the plurality of shape memory alloy plates.

10. 10. The heat pump of claim 8 or 9, wherein at least one shape memory alloy core comprises a plurality of stacked plates formed of a shape memory alloy having a different composition than the shape memory alloy making up the plurality of stacked plates in other stacks of the core.

11. 11. The heat pump of claim 8, wherein the plurality of shape memory alloy plates are substantially rectangular, square, 2D shaped, circular, or hexagonal in shape.

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