Patent Application
20190049158
The present invention relates to a wire used in a magnetic heat pump device using a magnetocaloric effect, and a heat exchanger and a magnetic heat pump device including the wire.
The present application claims priority from Japanese Patent Application No. 2017-155813 filed on Aug. 10, 2017. The contents described and/or illustrated in the documents relevant to the Japanese Patent Application No. 2017-155813 will be incorporated herein by reference as a part of the description and/or drawings of the present application.
In order to suppress an increase in pressure loss, a heat exchanger is known in which a plurality of linear magnetic bodies are inserted in a tubular casing while being overlapped in a direction intersecting the longitudinal direction of the magnetic body (for example, see Patent Document 1).
Patent Document 1: JP 2013-64588 A
When a magnetic heat pump device reaches a steady state, a temperature gradient is generated in the heat exchanger so that a uniform temperature span is formed between a high temperature end and a low temperature end of the heat exchanger. It is desirable that the temperature span become wider and thus the applicability of the magnetic heat pump increases. However, there is a problem in which the above-described linear magnetic body has a narrow temperature span compared to a granular magnetic body.
An object of the invention is to provide a wire capable of obtaining a wide temperature span and a heat exchanger and a magnetic heat pump device including the wire.
A wire according to the invention is a wire which is formed of a magnetocaloric material having a magnetocaloric effect, in which an outer surface of the wire partially has at least one of a concave portion and a convex portion in a longitudinal direction of the wire, the concave potion is recessed in a radial direction of the wire, and the convex portion protrudes in the radial direction.
In the above-described invention, the wire may have a non-circular cross-sectional shape, and a cross-sectional shape at one position in the longitudinal direction and a cross-sectional shape at the other position in the longitudinal direction may have a rotational symmetry relationship.
In the above-described invention, the wire may have a non-circular cross-sectional shape, and the wire may be twisted in a circumferential direction of the wire.
In the above-described invention, the cross-sectional shape of the wire may include an oval shape, a semi-circular shape, or an n-polygonal shape (n is a natural number from 3 to 8).
In the above-described invention, a cross-sectional shape at one position in the longitudinal direction and a cross-sectional shape at the other position in the longitudinal direction may be different from each other.
In the above-described invention, a cross-sectional area at one position in the longitudinal direction and a cross-sectional area at the other position in the longitudinal direction may be different from each other.
In the above-described invention, the wire may have a columnar shape having at least one of the concave portion and the convex portion.
In the above-described invention, at least one of the concave portion and the convex portion may include at least one of a wall and a groove formed on an outer surface of the wire, and an extending direction of at least one of the groove and the wall may include at least the circumferential direction of the wire as an element.
A heat exchanger according to the invention is a heat exchanger including: an assembly which is obtained by bundling a plurality of the above-described wires; and a casing which accommodates the assembly.
In the above-described invention, the casing may include a first opening located at one end portion and a second opening located at the other end portion, and a direction from the first opening to the second opening may substantially match the extending direction of the assembly.
A magnetic heat pump device according to the invention is a magnetic heat pump device comprising: at least one of the above-described heat exchangers; a magnetic field changer configured to apply a magnetic field to the magnetocaloric material and change the magnitude of the magnetic field; first and second external heat exchangers respectively connected to the heat exchanger through a pipe; and a fluid supplier configured to supply a fluid from the heat exchanger to the first or second external heat exchanger in synchronization with the operation of the magnetic field changer.
In the invention, the outer surface of the wire partially has at least one of the concave portion and the convex portion in the longitudinal direction of the wire. Accordingly, since a flow of a fluid flowing on the surface of the wire becomes turbulent and a heat transfer rate between the wire and the fluid can be enhanced, it is possible to obtain a wide temperature span.
Hereinafter, a first embodiment of the invention will be described with reference to the drawings.
A magnetic heat pump device 1 of this embodiment is a heat pump device using a magnetocaloric effect and includes, as illustrated in
The first and second MCM heat exchangers 10 and 20 of this embodiment correspond to an example of the heat exchanger of the invention, the piston 30 and the permanent magnet 40 of this embodiment correspond to an example of a magnetic changer of the invention, the low temperature side heat exchanger 50 and the high temperature side heat exchanger 60 correspond to an example of first and second external heat exchangers of the invention, the pipes 81 to 84 of this embodiment correspond to an example of a pipe of the invention, and the pump 70 and the switching valve 90 of this embodiment correspond to an example of a fluid supplier of the invention.
The first MCM heat exchanger 10 includes, as illustrated in
The wire 12A of this embodiment corresponds to an example of the wire of the invention, the assembly 11 of this embodiment corresponds to an example of the assembly of the invention, and the casing 13 of this embodiment corresponds to an example of the casing of the invention.
The wire 12A is composed of a magnetocaloric material (MCM) having a magnetocaloric effect. When a magnetic field is applied to the wire 12A formed of the MCM, magnetic entropy decreases as electron spins are aligned and the wire 12A generates heat so that a temperature rises. On the other hand, when the magnetic field is removed from the wire 12A, the magnetic entropy increases as the electron spins become cluttered and the wire 12A absorbs heat so that a temperature falls.
The MCM forming the wire 12A is not particularly limited as long as it is a magnetic body. However, a magnetic body having a Curie temperature (Curie point) in a normal temperature range of about 10° C. to 30° C. and exerts a high magnetocaloric effect in a normal temperature range is desirable. Detailed examples of such MCMs include gadolinium (Gd), gadolinium alloy, lanthanum-iron-silicon (La—Fe—Si) based compounds, and the like.
As illustrated in
In this way, in this embodiment, since the wire 12A is twisted, an outer surface 121 of the wire 12A partially includes a concave portion 122 and a convex portion 123 in the longitudinal direction of the wire 12A as illustrated in
Further, in this embodiment, since the wire 12A having a square cross-sectional shape (that is, a non-circular cross-sectional shape) is twisted, the cross-sectional shape at one position (for example, a line VIIA-VIIA illustrated in
Although there is no particular limitation, it is desirable that the wire 12A have a diameter in which a diameter of a circumscribed circle circumscribing a rectangular cross-sectional shape of the wire 12A is about 0.05 mm to 3 mm. Further, although there is no particular limitation, it is desirable that a twist pitch P of the wire 12A be about 10 to 50 times longer than the diameter of the circumscribed circle of the wire 12A.
The cross-sectional shape of the wire is not particularly limited to the above-described square shape as long as the shape is non-circular (that is, a shape other than a perfect circle).
For example, as illustrated in
Alternatively, as illustrated in
Alternatively, as illustrated in
Alternatively, as illustrated in
The assembly 11 is formed by bundling a plurality of the wires 12A. The plurality of wires 12A are bundled (overlapped) in a direction intersecting the longitudinal direction of the wire 12A. In other words, the plurality of wires 12A are adjacent to each other so that the side surfaces of the wires 12A contact each other. At this time, since the wire 12A has a non-circular cross-sectional shape and is twisted as described above, a passage 111 (see
The assembly 11 illustrated in
As a method of twisting the wires, for example, collective twisting, concentric twisting, complex twisting, and the like can be exemplified. The collective twisting is a twisting method in which a plurality of wires are bundled together and twisted in the same direction about the axis of the assembly. The concentric twisting is a twisting method in which a plurality of wires are concentrically twisted around a core wire. The complex twisting is a twisting method in which child stranded wires each of which is obtained by twisting a plurality of wires by concentric twisting or collective twisting are further twisted by concentric twisting or collective twisting.
The casing 13 which accommodates the assembly 11 includes, as illustrated in
The accommodation portion 14 includes a bottom portion 141 which constitutes a bottom plate of the casing 13 and a pair of side portions 142 and 143 which constitutes both side walls of the casing 13. An opening 144 is formed between upper ends of the pair of side portions 142 and 143. As a result, the accommodation portion 14 has a square-cornered U-shaped (substantially U-shaped) cross-sectional shape in a cross-section in a direction substantially orthogonal to the axial direction thereof.
The lid portion 15 is a rectangular plate-shaped member. As illustrated in
The assembly 11 is accommodated in the casing 13 so that the longitudinal direction (the extension direction (the longitudinal direction) of the assembly 11) of the wire 12A constituting the assembly 11 substantially matches the axial direction (a direction extending from the first opening 131 to the second opening 132) of the casing 13. Further, the centers of the first and second openings 131 and 132 are located to be substantially coaxial to the center of the assembly 11. Then, the passage 111 is formed between the wires 12A constituting the assembly 11 (see
As illustrated in
The first terminal member 17 includes a first connection port 171 which is smaller than the first opening 131 of the casing 13. As illustrated in
Similarly, an assembly 21 is also accommodated in the casing 23 of the second MCM heat exchanger 20 (see
The wire 22A of the second MCM heat exchanger 20 has the same configuration as the wire 12A of the first MCM heat exchanger 10. Further, the casing 23 of the second MCM heat exchanger 20 also have the same configuration as the casing 13 of the first MCM heat exchanger 10, and the terminal members of the second MCM heat exchanger 20 also has the same configuration as the terminal members 17 and 18 of the first MCM heat exchanger 10.
For example, in a case where an air conditioner using the magnetic heat pump device 1 of this embodiment is operated in a cooling mode, an indoor place is cooled by a heat exchange between the low temperature side heat exchanger 50 and the inside air, and heat is emitted to an outdoor place by a heat exchange between the high temperature side heat exchanger 60 and the outside air.
On the contrary, in a case where the air conditioner is operated in a warming mode, the indoor place is warmed by a heat exchange between the high temperature side heat exchanger 60 and the inside air, and heat is absorbed from the outdoor place by a heat exchange between the low temperature side heat exchanger 50 and the outside air.
As described above, a circulation path including four heat exchangers 10, 20, 50, and 60 is formed by two low temperature side pipes 81 and 82 and two high temperature side pipes 83 and 84, and a liquid medium is pressure-fed in the circulation path by the rotary pump 70. As a detailed example of the liquid medium, for example, a liquid such as water, an antifreeze solution, an ethanol solution, or a mixture thereof can be exemplified. The liquid medium of this embodiment corresponds to an example of a fluid of the invention.
Two MCM heat exchangers 10 and 20 are accommodated inside the piston 30. The piston 30 can move in a reciprocating manner between a pair of permanent magnets 40 by the actuator 35. Specifically, the piston 30 can move in a reciprocating manner between a “first position” illustrated in
Here, the “first position” is a position of the piston 30 when the first MCM heat exchanger 10 is not interposed between the permanent magnets 40 and the second MCM heat exchanger 20 is interposed between the permanent magnets 40. On the contrary, the “second position” is a position of the piston 30 when the first MCM heat exchanger 10 is interposed between the permanent magnets 40 and the second MCM heat exchanger 20 is not interposed between the permanent magnets 40.
Instead of the first and second MCM heat exchangers 10 and 20, the permanent magnet 40 may be moved in a reciprocating manner by the actuator 35. Alternatively, an electromagnet having a coil may be used instead of the permanent magnet 40. In this case, a mechanism of moving the MCM heat exchangers 10 and 20 or the magnet is not necessary. Further, when the electromagnet having the coil is used, the magnitude of the magnetic field applied to the wires 12A and 22A may be changed instead of applying/removing of the magnetic field with respect to the wires 12A and 22A of the MCM heat exchangers 10 and 20.
The switching valve 90 is provided at the first high temperature side pipe 83 and the second high temperature side pipe 84. In synchronization with the operation of the piston 30, the switching valve 90 can switch the liquid medium supply destination of the rotary pump 70 to the first MCM heat exchanger 10 or the second MCM heat exchanger 20 and switch the connection destination of the high temperature side heat exchanger 60 to the second MCM heat exchanger 20 or the first MCM heat exchanger 10.
Next, an operation of the magnetic heat pump device 1 of this embodiment will be described with reference to
First, when the piston 30 is moved to the “first position” illustrated in
At the same time, a first path (the rotary pump 70 the first high temperature side pipe 83 the first MCM heat exchanger 10 the first low temperature side pipe 81 the low temperature side heat exchanger 50 the second low temperature side pipe 82 the second MCM heat exchanger 20 the second high temperature side pipe 84 the high temperature side heat exchanger the rotary pump 70) is formed by the switching valve 90.
For this reason, the liquid medium is cooled by the wire 12A of the first MCM heat exchanger 10 of which a temperature decreases due to a demagnetization and the liquid medium is supplied to the low temperature side heat exchanger 50 so that the low temperature side heat exchanger 50 is cooled. At this time, since the liquid medium passes through the passage 111 formed between the wires 12A inside the first MCM heat exchanger 10 so as to contact the wires 12A, the liquid medium is cooled by the wires 12A.
Meanwhile, the liquid medium is heated by the wire 22A of the second MCM heat exchanger 20 of which a temperature increases due to a magnetization and the liquid medium is supplied to the high temperature side heat exchanger 60 so that the high temperature side heat exchanger 60 is heated. At this time, since the liquid medium passes through the passage formed between the wires 22A inside the second MCM heat exchanger 20 so as to contact the wires 22A, the liquid medium is heated by the wires 22A.
Next, when the piston 30 is moved to the “second position” illustrated in
At the same time, a second path (the rotary pump 70 the second high temperature side pipe 84 the second MCM heat exchanger 20 the second low temperature side pipe 82 the low temperature side heat exchanger the first low temperature side pipe 81 the first MCM heat exchanger 10 the first high temperature side pipe 83 the high temperature side heat exchanger the rotary pump 70) is formed by the switching valve 90.
For this reason, the liquid medium is cooled by the wire 22A of the second MCM heat exchanger 20 of which a temperature decreases due to a demagnetization and the liquid medium is supplied to the low temperature side heat exchanger 50 so that the low temperature side heat exchanger 50 is cooled. At this time, since the liquid medium passes through the passage formed between the wires 22A inside the second MCM heat exchanger 20 so as to contact the wires 22A, the liquid medium is cooled by the wire 22A.
Meanwhile, the liquid medium is heated by the wire 12A of the first MCM heat exchanger 10 of which a temperature increases due to a magnetization and the liquid medium is supplied to the high temperature side heat exchanger 60 so that the high temperature side heat exchanger 60 is heated. At this time, since the liquid medium passes through the first passage 111 formed between the wires 12A inside the first MCM heat exchanger 10 so as to contact the wires 12A, the liquid medium is heated by the wires 12A.
When the above-described cycle is repeated, the cold and hot temperature generated by the magnetocaloric effect is accumulated in the assemblies 11 and 21, the side connected to the high temperature side pipe has a high temperature, and the side connected to the low temperature side pipe has a low temperature. Then, when a temperature gradient is formed inside the first and second MCM heat exchangers 10 and 20 and the first and second MCM heat exchangers 10 and 20 reaches a steady state, a uniform temperature span ΔT is generated between the high temperature end and the low temperature end. The temperature span ΔT is expressed by the following equation (1). In the following equation (1), Th indicates the temperature at the high temperature end in the steady state and T1 indicates the temperature at the low temperature end in the steady state.
[Math. 1]
ΔT=Th−T1 (1)
Here, Δq which indicates the heat quantity per unit time from the unit surface area of the magnetocaloric material to the liquid medium is expressed by the following equation (2). In the following equation (2), h indicates the heat exchange rate, Ts indicates the surface temperature of the magnetocaloric material, and Tf indicates the temperature of the liquid medium.
[Math. 2]
Δq=h(Ts−Tf) (2)
Then, a state where the temperature span ΔT becomes uniform due to the repeated cycle (a state where the temperature span ΔT is saturated) is a state where the heat quantity Δq of the above-described equation (2) is sufficiently small and a change ΔTf of the refrigerant temperature Tf for each cycle disappears. Thus, according to the above-described equation (1), the magnitude of the temperature span ΔT depends on the magnitude of the heat transfer rate h.
In general, the heat exchange rate h in the above-described equation (2) is determined by the shape of the magnetocaloric material and the filling method. Regarding some shapes such as a granular or linear shape, the heat exchange rate h is formulated by the Nusselt number Nu. That is, when the Nusselt number Nu is large, it can be considered that the heat transfer rate h is also large. Then, when the liquid medium flows at the same speed, the Nusselt number Nu1 of the granular material can be expressed by the following equation (3) and the Nusselt number Nu2 of the wire can be expressed by the following equation (4). In the following equations (3) and (4), Re is Reynolds number and Pr is Prandtl number.
[Math. 3]
Nu1=2+0.6Re0.5Pr0.33 (3)
[Math. 4]
Nu2=0.023Re0.8Pr0.33 (4)
According to the above-described equations (3) and (4), since the Nusselt number Nu2 of the wire is smaller than the Nusselt number Nu1 of the granular material, it is understood that the heat transfer rate of the granular is lower than that of the wire. That is, the temperature span AT of the wire not twisted is narrower than that of the granular material. The Nusselt number Nu2 illustrated in the above-described equation (4) is calculated on a condition that the flow of the liquid refrigerant flowing on the surface of the wire is a laminar flow and the heat exchange between the wire surface and the liquid refrigerant is performed by natural convection.
On the contrary, in this embodiment, the concave portion 122 and the convex portion 123 are partially provided in the outer surface 121 of the wire 12A in the longitudinal direction of the wire 12A. Accordingly, the liquid medium flowing on the surface of the wire 12A collides with the concave portion 122 or the convex portion 123 so that forced convection occurs and the flow of the liquid medium becomes turbulent. For this reason, since the heat transfer rate between the wire 12A and the liquid medium can be improved, a wide temperature span can be obtained.
A wire 12B of this embodiment has, as illustrated in
In this way, in this embodiment, since the wire 12B is provided with the groove 124, the outer surface 121 of the wire 12B partially includes the concave portion 122 in the longitudinal direction of the wire 12B as illustrated in
Further, in this embodiment, since the wire 12B is provided with the groove 124, the cross-sectional area at one position (for example, a line XIA-XIA of
In this way, in this embodiment, the concave portion 122 is partially provided in the outer surface 121 of the wire 12B in the longitudinal direction of the wire 12B similarly to the first embodiment. Accordingly, the liquid medium flowing on the surface of the wire 12B collides with the concave portion 122 so that forced convection occurs and the flow of the liquid medium becomes turbulent. For this reason, since the heat transfer rate between the wire 12B and the liquid medium can be increased, a wide temperature span can be obtained.
The shape of the wire is not particularly limited. For example, as illustrated in
Alternatively, as illustrated in
Embodiments heretofore explained are described to facilitate understanding of the present invention and are not described to limit the present invention. It is therefore intended that the elements disclosed in the above embodiments include all design changes and equivalents to fall within the technical scope of the present invention.
The configuration of the above-described magnetic heat pump device is an example, and the heat exchanger according to the invention may be applied to another magnetic heat pump device of an AMR (Active Magnetic Refrigeration) type.
For example, the magnetic heat pump device may include one MCM heat exchanger, a magnetic field changer configured to supply a magnetic field to the MCM and change the magnitude of the magnetic field, first and second external heat exchangers respectively connected to the MCM heat exchanger through a pipe, and a fluid supplier configured to supply a fluid to the first or second external heat exchanger from the MCM heat exchanger in synchronization with the operation of the magnetic field changer. Further, in the above-described embodiment, the liquid medium flow direction is changed by using the rotary pump 70 and the switching valve 90, but a reciprocating pump may be used instead of the rotary pump 70 and the switching valve 90.
Further, in the above-described embodiment, an example in which the magnetic heat pump device is applied to the air conditioner for home or an automobile has been described, but the invention is not particularly limited thereto. For example, when an MCM having an appropriate Curie temperature according to the application is selected, the magnetic heat pump device according to the invention may be used for an application in an extremely low temperature range such as a refrigerator or in a high temperature range to some extent.
Further, in this embodiment, the first and second MCM heat exchangers 10 and 20 have the same configurations, but the invention is not particularly limited thereto. Here, the heat exchangers may have different configurations. For example, the first and second MCM heat exchangers 10 and 20 may use wires having different wire diameters. Further, the twisting pitches of the wires may be different from each other.
Further, in this embodiment, the MCM heat exchanger includes a single assembly, but the invention is not particularly limited thereto. For example, a plurality of assemblies may be arranged in series along the extending direction of the MCM heat exchanger. In this case, the plurality of assemblies may have the same configurations or different configurations.
1: magnetic heat pump device
10: first MCM heat exchanger
11: assembly
111: passage
12A, 12Aa to 12Al, 12B, 12Ba to 12Be: wire
122: concave portion
123: convex portion
124: groove
125: wall
13: casing
131: first opening
132: second opening
14: accommodation portion
141: bottom portion
142, 143: side portion
144: opening
15: lid portion
17: first terminal member
171: first connection port
18: second terminal member
181: second connection port
20: second MCM heat exchanger
21: assembly
22A: wire
23: casing
271: first connection port
281: second connection port
30: piston
35: actuator
40: permanent magnet
50: low temperature side heat exchanger
60: high temperature side heat exchanger
70: rotary pump
81 to 82: first and second low temperature side pipes
83 to 84: third and fourth high temperature side pipes
90: switching valve
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-155813 | Aug 2017 | JP | national |
