Magnetic heat pump

Abstract

To save energy when cooling is performed by applying a variable magnetic field to a magnetic working substance.SOLUTION: A magnetic working substance 30 is disposed within a superconducting coil 31. A capacitor 32 is connected in series to the superconducting coil 31 via a switch 36. Both ends of the superconducting coil 31 are connected via the switch 37. Due to this configuration, after an electric current is caused to flow from a power source 33 to the superconducting coil 31, even if the power source 33 is shut off, the electric current to the superconducting coil 31 is periodically changed by an LC resonant circuit, and the magnetic working substance 30 can be switched to a heat generation state and a cooling state. By putting in a state where both ends of the superconducting coil 31 are connected to cause a constant electric current to continuously flow and a state where both of the superconducting coil 31 and the capacitor 32 are cut off to prevent an electric current from flowing, more efficient heat exchange is enabled. Accordingly, energy for cooling by using the variable magnetic field can be saved.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetic heat pump that performs cooling by applying a varying magnetic field generated by a superconducting coil to a magnetic working material. [Background technology]

[0002] BACKGROUND ART Conventionally, magnetic refrigerators that use magnetic materials (hereinafter referred to as "magnetic working materials") that generate and absorb heat in response to a magnetic field are known as refrigerators that are applicable to extremely low temperatures below liquid helium. For example, Patent Document 1 discloses a static magnetic refrigerator in which a magnetic working material is placed in the center of a superconducting coil and a magnetic shield is moved back and forth in the space between the superconducting coil and the magnetic working material. In this technology, the magnetic field is applied to or blocked from the magnetic working material in accordance with the reciprocating motion of the magnetic shield, thereby changing the heat generation / absorption of the magnetic working material and achieving refrigeration. Patent Document 2 discloses a magnetic refrigerator having a structure in which a superconducting coil and a magnetic shield are stacked and a magnetic working material is placed inside the stack. In this technology, the magnetic shield is reciprocated to switch between a state in which it is placed inside the superconducting coil and a state in which it is placed inside the magnetic shield, thereby changing the heat generation / absorption of the magnetic working material and realizing refrigeration. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-273956 [Patent Document 2] Japanese Patent Application Publication No. 6-151983 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional magnetic refrigeration technology, the generation of a magnetic field by a superconducting coil requires cooling to maintain the superconducting state, and although energy efficiency has been improved due to the absence of current loss, energy is required for the reciprocating motion of the magnetic shield or magnetic working material itself, leaving room for improvement in overall energy efficiency. Therefore, there has been a demand for a technology that can vary the magnetic field acting on the magnetic working material in an energy-saving manner. In view of the above, an object of the present invention is to fluctuate a magnetic field in an energy-saving manner and to make it possible to realize magnetic refrigeration. [Means for solving the problem]

[0005] The present invention provides A magnetic heat pump that transports heat from an object to be cooled, the magnetic working material that becomes exothermic or endothermic in response to a change in the magnetic field; a superconducting coil that applies a magnetic field to the magnetic working material; an LC resonant circuit in which the superconducting coil and a capacitor are connected in series; The magnetic heat pump may be configured to include a heat exchange mechanism for exchanging heat between the magnetic working material and the object to be cooled.

[0006] In the present invention, the LC resonant circuit is provided, so the current flowing through the superconducting coil fluctuates at a period corresponding to the resonant frequency, which causes the magnetic field applied to the magnetic working material to fluctuate, thereby achieving cooling. Moreover, since superconductivity has zero electrical resistance, the current flowing through the LC resonant circuit theoretically continues to flow with almost no attenuation even without external energy being applied. Therefore, according to the present invention, it is possible to keep the energy required for cooling using a magnetic working material to a very low level.

[0007] In the present invention, various substances such as gadolinium can be used as the magnetic working material. Furthermore, the shape and structure of the portion of the heat exchange mechanism that exchanges heat with the magnetic working material can be determined arbitrarily. For example, a portion of the heat exchange mechanism may be made of a mass of magnetic working material, or may be made of thin wires made of magnetic working material woven into a mesh. Such thin wires may be manufactured by a so-called powder-in-tube manufacturing technique, in which the magnetic working material is wrapped in copper or other metals with good thermal conductivity. In the heat exchange mechanism, the part that exchanges heat with the object to be cooled may be, for example, a mechanism that circulates a heat exchange medium, or may utilize heat conduction from metal or other materials. Various other configurations are also applicable. The LC resonant circuit can be designed with a resonant frequency that effectively achieves heat exchange, and the inductance of the superconducting coil and the capacitance of the capacitor can be designed accordingly. The resonant frequency can be set arbitrarily, but can be as low as about 0.1 Hz, for example.

[0008] In today's invention, The LC resonant circuit is a first state in which the superconducting coil is disconnected from the circuit; a second state in which the capacitor is disconnected from the circuit to form a closed circuit including the superconducting coil; The superconducting coil and the capacitor may be connected in series to one or more switches for switching between a third state and a third state.

[0009] By doing this, in the first state, it is possible to maintain a state in which no current flows through the superconducting coil. In the second state, it is possible to continue to flow current in a fixed direction through the superconducting coil. In the third state, it is possible to vary the current flowing through the superconducting coil. In this way, according to the above embodiment, by separating the states, it becomes possible to control the magnetic field applied to the magnetic working material.

[0010] In the aspect in which the first to third states can be switched, The power supply may further include a switch control unit that controls the switch so that the first state of the LC resonant circuit is held for a first holding time and the second state is held for a second holding time.

[0011] The magnetic working material undergoes a heating or cooling state in response to changes in the magnetic field. In this sense, the first state, in which no current flows through the superconducting coil, and the second state, in which current continues to flow in one direction through the superconducting coil, do not appear to contribute to either heating or cooling. However, in reality, heating or cooling does not immediately stop just because the magnetic field fluctuations have stopped. The above embodiment has the advantage that the heating or cooling state of the magnetic working material can be maintained even after the magnetic field fluctuations have stopped by controlling the current to maintain the first state and the second state, respectively.

[0012] In this way, when the first and second states are maintained, the heat exchange mechanism is a mechanism for flowing a heat exchange medium through a flow path capable of heat exchange between the heat exchange medium and the magnetic working material, The first and second retention times may be set to be equal to or longer than the time required for the heat exchange medium to pass through a portion of the flow path where the heat exchange medium exchanges heat with the magnetic working material.

[0013] This has the advantage that the heat exchange medium can perform heat exchange sufficiently.

[0014] If the first to third states can be switched, There are a plurality of the switches, When switching between the first to third states, the switch control section may perform control so as to close any of the switches that have been open, and then open any of the switches that have been closed.

[0015] Generally, if a switch is suddenly opened while a current is flowing to stop the current from flowing, an arc discharge may occur at the switch. In the above embodiment, one of the switches is closed to ensure that the current flows before the other switch is opened, thereby preventing the occurrence of an arc discharge.

[0016] In the present invention, the heat exchange mechanism is a mechanism for flowing a heat exchange medium through a flow path capable of heat exchange between the heat exchange medium and the magnetic working material, The flow path is a heat-generating flow path when the magnetic working material is in the heat-generating state; and an endothermic flow path when the magnetic working material is in the endothermic state.

[0017] When the magnetic working material is in a heat-generating state, it is preferable to perform heat exchange so as to discharge the heat to the outside. On the other hand, when the magnetic working material is in a cooled state, it is preferable to perform heat exchange with the object to be cooled. In the above embodiment, since the magnetic working material is provided with a flow path suitable for each state, it is possible to achieve appropriate heat exchange in both the heat-generating state and the cooled state.

[0018] When a heat generation flow path and a heat absorption flow path are provided, they may be provided as separate systems. The heat generation flow path and the heat absorption flow path are partially common to each other, The flow path may further include a switching valve for switching between the heat generation flow path and the heat absorption flow path.

[0019] This allows the heat exchange medium and its flow path to be shared, making it possible to configure the system more simply and at lower cost than providing separate flow paths for heating and cooling.

[0020] When equipped with a heat generation flow path and a heat absorption flow path, A flow path control unit may be provided that selectively uses the heat generation flow path and the heat absorption flow path in conjunction with the state of current flow to the superconducting coil. This makes it possible to selectively use the flow path when heat is generated and the flow path when heat is absorbed in synchronization with the heat generation and heat absorption states of the magnetic working material.

[0021] When switching the flow path in this way in conjunction with the energized state, The flow path control unit may switch from the heat generation flow path to the heat absorption flow path with a predetermined delay from the timing when the current flow state to the superconducting coil changes from the current flow state that causes the magnetic working material to be in the heat generation state to the current flow state that causes the magnetic working material to be in the heat absorption state.

[0022] If the flow path is switched from the heat generation flow path to the heat absorption flow path immediately after the change to the heat absorption state, the heat medium that has received heat during the heat generation may flow into the heat absorption flow path. According to the above-described embodiment, the switching is performed after a delay of a while after the change to the heat absorption state, so that such a problem can be avoided.

[0023] The present invention does not need to include all of the various features described above, and can be configured by omitting or combining some of them as appropriate. Furthermore, the present invention may be configured as a magnetic refrigeration method using a magnetic working material in addition to a magnetic heat pump. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is an explanatory diagram showing the configuration of a magnetic heat pump. [Figure 2] FIG. 10 is an explanatory diagram showing a switching mode. [Figure 3] FIG. 10 is an explanatory diagram showing a switching sequence. DETAILED DESCRIPTION OF THE INVENTION

[0025] The following describes an embodiment of the present invention, taking as an example a configuration of a magnetic heat pump using a superconducting coil and a magnetic working material. This is an example of a configuration of a system in which hydrogen is the cooled material, and this is recondensed and stored as liquid hydrogen. This is a system that performs refrigeration at extremely low temperatures.

[0026] FIG. 1 is an explanatory diagram showing the configuration of a magnetic heat pump. A superconducting coil 31 is placed inside the sealed vessel 10. The superconducting coil 31 is cooled to achieve superconductivity, but this cooling mechanism is not shown in the figure to avoid complicating the drawing.

[0027] The magnetic working material 30, which generates / absorbs heat depending on the state of the magnetic field, is placed in the internal space of the superconducting coil 31. The magnetic working material 30 can be made of various materials, but in this embodiment, a dysprosium alloy (e.g., DyNi) is used. The magnetic working material 30 can be made by weaving thin wires produced by a so-called powder-in-tube manufacturing technique, in which dysprosium alloy powder is filled into a hollow thin wire made of copper or other material with good thermal conductivity. The magnetic working material 30 is not limited to this configuration, and may be made of a block of dysprosium alloy. However, these are merely examples, and gadolinium alloys (e.g., Gd5Ge4) are not to be excluded.

[0028] Flow paths 21-24 for flowing a heat exchange medium are provided so as to pass through the magnetic working material 30. When the magnetic working material 30 generates / absorbs heat due to the action of a magnetic field, the corresponding heat is transferred by the heat exchange medium in the flow paths 21-24.

[0029] A heat exhaust unit 20 is attached above the flow paths 21 and 22 and outside the sealed container 10. When the magnetic working material 30 is in a heat generating state, the heat is transferred to the heat exhaust unit 20 through the flow paths 21 and 22 and is discharged from the sealed container 10 to the outside. Meanwhile, a thermal switch 25 is attached between the hydrogen storage tank 12, which is the object to be cooled, and the magnetic working material 30. The thermal switch 25 is an element that transfers heat in only one direction. Various well-known elements can be used for the thermal switch 25, so a detailed description will be omitted. By providing the thermal switch 25, when the magnetic working material 30 absorbs heat, heat flows from the hydrogen storage tank 12 to the magnetic working material 30, thereby cooling the hydrogen storage tank 12. Conversely, when the magnetic working material 30 absorbs heat, heat transfer to the hydrogen storage tank 12 is blocked, preventing the cooling of the hydrogen storage tank 12 from being hindered.

[0030] In this embodiment, the flow paths 21 to 24 are configured to circulate the heat exchange medium as a series of flow paths, and switching mechanisms 26 and 27 are provided midway through the flow paths. The switching mechanism 26 is a mechanism for short-circuiting the flow paths 21 and 22 so that the heat exchange medium circulates so as to bypass the heat exhaust section 20. When the magnetic working material 30 is in a heat absorption state, the medium can be effectively cooled by bypassing the heat exhaust section 20. This state is the heat absorption flow path. On the other hand, the switching mechanism 27 is a mechanism that short-circuits the flow paths 23 and 24 so as to bypass the thermal switch 25 and the hydrogen storage tank 12. When the magnetic working material 30 is in a heat generating state, bypassing the hydrogen storage tank 12, which is the object to be cooled, prevents the cooling of the hydrogen storage tank 12 from being hindered. This state becomes the heat generating flow path. In this way, by making it possible to switch between the flow path during heat absorption and the flow path during heat generation, it becomes possible to effectively perform heat exchange during heat absorption and heat generation. In the embodiment, the switching mechanisms 26 and 27 are provided in part of the series of flow paths, but the flow path for heat absorption and the flow path for heat generation may be configured as two separate flow paths.

[0031] The superconducting coil 31 is connected to a circuit including a power supply 33 and a capacitor 32. The power supply 33 can be a system power supply, a battery, or any other type of power source. In the circuit, the power supply 33 and the capacitor 32 are connected in parallel to both ends of the superconducting coil 31. In addition, a circuit is formed between the superconducting coil 31 and the capacitor 32, shorting both poles. A switch 35 is provided between the capacitor 32 and the power supply 33, a switch 36 is provided between the short circuit and the capacitor 32, and a switch 37 is provided in the short circuit. The following circuit configuration is realized by opening and closing these switches 35 to 37. With switches 35 and 36 closed and switch 37 open, a closed circuit is formed connecting power supply 33 and superconducting coil 31. It is only in this state that switch 35 is closed. When all of the switches 35 to 37 are open, the superconducting coil 31, the capacitor 32, and the power supply 33 are all disconnected from the circuit. When the switches 35 and 37 are open and the switch 36 is closed, an LC resonant circuit is formed by connecting the superconducting coil 31 and the capacitor 32. When the switches 35 and 36 are open and the switch 37 is closed, a circuit is formed connecting both poles of the superconducting coil 31 .

[0032] The operation of the magnetic heat pump is controlled by a control device 40. The control device 40 can be configured as a computer equipped with an internal CPU and memory. In this embodiment, by installing a computer program, the following functions are realized in software: a switching control function for switching the switches 35 to 37; a flow path control function for controlling the switching mechanisms 26 and 27 to switch between the heat generation flow path and the cooling flow path; and a heat exhaust control function for controlling the operation of the heat exhaust unit 20. All or part of these functions may be realized by hardware such as an ASIC.

[0033] FIG. 2 is an explanatory diagram showing a switching mode. First, when a closed circuit is formed connecting the power supply 33 and the superconducting coil 31 with the switches 35 and 36 closed and the switch 37 open, a current flows through the superconducting coil 31 and initial charging is performed (this state is not shown). When the initial charging is completed, the respective switching modes shown in FIG. 2 are entered.

[0034] As shown in Fig. 2(a), when switch 37 is closed and switch 36 is opened, a closed circuit is formed connecting both poles of superconducting coil 31. Since current is already flowing in superconducting coil 31, current continues to flow in a fixed direction (clockwise in the figure) in Fig. 2(a).

[0035] 2(b), when switch 37 is opened and switch 36 is closed, an LC resonant circuit is formed connecting superconducting coil 31 and capacitor 32. The current that was flowing clockwise through superconducting coil 31 now flows clockwise, including capacitor 32, and capacitor 32 is charged as shown in the figure. As the capacitor 32 is charged, the current flowing through the superconducting coil 31 decreases and eventually becomes zero.

[0036] If left as is, current will then begin to flow in the reverse direction from capacitor 32 to superconducting coil 31, and resonance will begin due to the LC resonant circuit. In this embodiment, although it is acceptable to allow such resonance to occur, in order to more actively control the period during which current flows, switches 36 and 37 are opened as shown in Figure 2(c) when the current to superconducting coil 31 becomes zero. In this way, both superconducting coil 31 and capacitor 32 are disconnected from the circuit, and capacitor 32 remains charged while no current flows.

[0037] Next, as shown in Figure 2(d), switch 36 is closed while switch 37 is left open. This causes current to flow through superconducting coil 31 using capacitor 32 as a power source, and current begins to flow counterclockwise as shown. This state continues until the charge in capacitor 32 is completely discharged.

[0038] If left as is, superconducting coil 31 will start charging capacitor 32, and resonance will begin due to the LC resonant circuit. Although there is no problem in allowing such resonance to occur, in order to more actively control the period during which current flows, switch 36 is opened and switch 37 is closed as shown in Figure 2(e) when the charge in capacitor 32 is released. This allows counterclockwise current to continue flowing through superconducting coil 31.

[0039] Next, as shown in Fig. 2(f), when switch 36 is closed and switch 37 is opened, an LC resonant circuit is formed connecting superconducting coil 31 and capacitor 32. The current that had been flowing counterclockwise through superconducting coil 31 now flows counterclockwise, including capacitor 32, and capacitor 32 is charged as shown in the figure. As the capacitor 32 is charged, the current flowing through the superconducting coil 31 decreases and eventually becomes zero.

[0040] When the current to the superconducting coil 31 becomes zero, the switches 36 and 37 are opened as shown in Fig. 2(g). This disconnects both the superconducting coil 31 and the capacitor 32 from the circuit, and the capacitor 32 remains charged while no current flows.

[0041] Next, as shown in Figure 2(h), switch 36 is closed while switch 37 is left open. This causes current to flow through superconducting coil 31 using capacitor 32 as a power source, and current begins to flow counterclockwise as shown. This state continues until the charge in capacitor 32 is completely discharged. Then, the state returns to that shown in FIG. 2(a).

[0042] The above switching is repeated. In the state shown in Fig. 2(b), the current to the superconducting coil 31 is decreasing, so the magnetic working material 30 is in a cooled state. In Fig. 2(c), no current is flowing, but the cooled state shown in Fig. 2(b) continues for a while. In the state shown in Fig. 2(d), the current to the superconducting coil 31 increases, causing the magnetic working material 30 to generate heat. In Fig. 2(e), no current flows, but the heat generation state shown in Fig. 2(d) continues for a while. Similarly, Figures 2(f) and 2(g) represent the cooling state, and Figures 2(h) and 2(a) represent the heating state. In this way, in this embodiment, by performing the switching shown in Figure 2, the current to the superconducting coil 31 can be changed using the LC resonant circuit without applying energy from the outside, and the magnetic working material 30 can be changed between a heating state and a cooling state.

[0043] Fig. 3 is an explanatory diagram showing the switching sequence. Broken lines L36 and L37 show the ON (closed) and OFF (open) changes of switches 36 and 37, and the accompanying change in current is shown schematically by curve C. (a) to (h) on the time axis correspond to the states in Fig. 2(a) to Fig. 2(h). During period (a) (corresponding to FIG. 2(a)), switch 36 is OFF, switch 37 is ON, and the current is constant at its maximum value. During period (b) (corresponding to FIG. 2(b)), the switch 36 is ON and the switch 37 is OFF, and the current decreases as the capacitor 32 is charged. This causes the magnetic working material 30 to cool. During period (c) (corresponding to FIG. 2(c)), both switches 36 and 37 are turned off and the current is 0. The magnetic working material 30 is maintained in a cooled state for a while. During period (d) (corresponding to FIG. 2(d)), switch 36 is ON, switch 37 is OFF, and the reverse current gradually increases with capacitor 32 as the power source, causing the magnetic working material to generate heat. During period (e) (corresponding to FIG. 2(e)), switch 36 is OFF, switch 37 is ON, and the reverse current is constant at its maximum value. The magnetic working material 30 maintains a heat generating state for a while. During period (f) (corresponding to FIG. 2(f)), switch 36 is ON and switch 37 is OFF, and the reverse current decreases as the capacitor 32 is charged. As a result, the magnetic working material 30 enters a cooled state. During period (g) (corresponding to FIG. 2(g)), both switches 36 and 37 are turned off and the current is 0. The magnetic working material 30 is maintained in a cooled state for a while. During period (h) (corresponding to FIG. 2(h)), switch 36 is ON, switch 37 is OFF, and the reverse current gradually increases with capacitor 32 as the power source, causing the magnetic working material to generate heat.

[0044] The lower part of the figure shows an enlarged view of the detailed switching procedure when switching from period (a) to period (b). In this switching, switch 36 is switched from OFF to ON, and switch 37 is switched from ON to OFF. If switch 37 is switched OFF even momentarily earlier than switch 36 is switched ON, an instant occurs when both switches 36 and 37 are OFF. When current is flowing as in period (a), an arc discharge typically occurs when both switches are suddenly turned OFF. To avoid this, in this embodiment, as shown in the figure, switching is controlled so that switch 36 is first turned ON, and then switch 37 is turned OFF after a short time dt has elapsed. This prevents arc discharge. The short time dt can be determined arbitrarily as long as it is within a range that avoids arc discharge. This control of delaying the turning off of the switch is also applied when switching from period (e) to period (f).

[0045] In FIG. 3, the switching timings of the switching mechanisms 26, 27 are also indicated by black triangles B1 to B4. When the transition from period (a) to period (b) occurs, the magnetic working material 30 enters a cooling state. However, since the magnetic working material 30 is in a heat-generating state during period (a), the heat exchange medium is in a heated state. Therefore, if the flow path is switched to the cooling state flow path, in which the heat exchange medium flows into the hydrogen storage tank 12 (the object to be cooled) immediately after the transition to period (b), there is a risk that high-temperature heat exchange medium will flow into the hydrogen storage tank 12. In this embodiment, to avoid this, the flow path is switched to the cooling state flow path at time B1, some time after the transition to period (b). The elapsed time from the transition to time B1 can be determined arbitrarily based on the cooling state of the heat exchange medium, etc.

[0046] Next, when the period (c) transitions to the period (d), the magnetic working material 30 enters a heat generating state, and the heat exchange mechanism switches to the heat generating flow path. In this case, there is no risk of impeding the cooling of the hydrogen storage tank 12, so the switching to the heat generating flow path is performed at timing B2, which is simultaneous with the transition. However, taking into consideration that the temperature of the heat exchange medium will remain low for a while even during the transition from period (c) to period (d), a method of switching with a slight delay from the transition to period (d), as with timing B1, is not excluded.

[0047] When switching from period (e) to period (f), similar to timing B1, the flow path is switched to the cooling flow path some time after the transition to period (f). When switching from period (g) to period (h), similar to timing B2, the flow path is switched to the heating flow path simultaneously with the transition to period (h). This allows for effective heat exchange.

[0048] As shown in Figure 3, the switching sequence of this embodiment includes periods (a) and (e) during which a constant current flows (these are called "maximum current holding periods"), and periods (c) and (g) during which no current flows (these are called "zero current holding periods"). During these periods, the magnetic field to the magnetic working material 30 does not change, but the immediately preceding heated or cooled state is maintained. Therefore, by providing the maximum current holding periods and zero current holding periods, the heated or cooled state of the magnetic working material 30 can be fully utilized for heat exchange. The maximum current holding period and the zero current holding period can be determined arbitrarily, but in order to utilize the heat generating and cooling states of the magnetic working material 30, it is preferable to set them longer than the time required for the heat exchange medium to flow through the part where heat exchange with the magnetic working material 30 takes place.

[0049] The time it takes for the magnetic working material 30 to heat up or cool down is determined by the time it takes for the current to change during periods (b), (d), (f), and (h). This time is determined by the resonant frequency of the LC resonant circuit, which is determined by the reactance of the superconducting coil 31 and the capacitance of the capacitor 32. Therefore, in this embodiment, it is preferable to set periods (b), (d), (f), and (h) so as to ensure sufficient time for heat exchange with the heat exchange medium, and to design the LC resonant circuit to achieve this. It is preferable that the times of periods (b), (d), (f), and (h) be at least longer than the time it takes for the heat exchange medium to flow through the portion where heat exchange with the magnetic working material 30 occurs.

[0050] According to the magnetic heat pump of the embodiment described above, by periodically flowing the energy stored in the superconducting coil 31 by initial charging through the LC resonant circuit of the superconducting coil 31 and the capacitor 32, the magnetic field applied to the magnetic working material 30 can be varied with almost no external energy supply, which has the advantage of reducing the energy required for cooling. In reality, the current flowing through the LC resonant circuit attenuates due to AC loss and other factors, but it is possible to maintain cooling by supplying a small amount of energy to compensate for this.

[0051] It is not necessary to provide all of the various features described above, and some of them can be omitted or combined as appropriate. Furthermore, the present invention is not limited to the above-described embodiments, and various modifications can be made. While the embodiments have been described as examples of a magnetic heat pump for condensing hydrogen, the present invention can also be used for other applications. Such applications include refrigeration or cooling systems that are not intended to condense hydrogen, such as cooling systems for nuclear fusion coils and superconducting power storage systems. [Industrial Applicability]

[0052] The present invention can be applied to cooling by applying a varying magnetic field using a superconducting coil to a magnetic working material. [Explanation of symbols]

[0053] 10. Airtight containers 12 Hydrogen storage tank 20 Heat exhaust section 21, 22, 23, 24 Flow paths 25 Thermal Switch 26, 27 switching mechanism 30 Magnetic Working Materials 31 Superconducting coil 32 capacitor 33 Power supply 35, 36, 37 Switches 40 Control device

Claims

1. A magnetic heat pump that transports heat from an object to be cooled, a magnetic working material that becomes exothermic or endothermic in response to a change in the magnetic field; a superconducting coil that applies a magnetic field to the magnetic working material; an LC resonant circuit in which the superconducting coil and a capacitor are connected in series; A magnetic heat pump comprising a heat exchange mechanism for exchanging heat between the magnetic working material and the object to be cooled.

2. 2. The magnetic heat pump according to claim 1, The LC resonant circuit is a first state in which the superconducting coil is disconnected from the circuit; a second state in which the capacitor is disconnected from the circuit to form a closed circuit including the superconducting coil; a third state in which the superconducting coil and the capacitor are connected in series;

3. 3. The magnetic heat pump according to claim 2, A magnetic heat pump comprising: a switch control unit that controls the switch so as to hold the first state in the LC resonant circuit for a first holding time and to hold the second state for a second holding time.

4. 4. The magnetic heat pump according to claim 3, the heat exchange mechanism is a mechanism for flowing a heat exchange medium through a flow path capable of heat exchange between the heat exchange medium and the magnetic working material, The magnetic heat pump, wherein the first and second retention times are each equal to or longer than the time required for the heat exchange medium to pass through a portion of the flow path where the heat exchange medium exchanges heat with the magnetic working material.

5. 4. The magnetic heat pump according to claim 3, There are a plurality of the switches, The magnetic heat pump is configured such that, when switching between the first to third states, the switch control unit closes any of the switches that have been open, and then opens any of the switches that have been closed.

6. 2. The magnetic heat pump according to claim 1, the heat exchange mechanism is a mechanism for flowing a heat exchange medium through a flow path capable of heat exchange between the heat exchange medium and the magnetic working material, The flow path is a heat-generating flow path when the magnetic working material is in the heat-generating state; a heat absorption flow path when the magnetic working material is in the heat absorption state.

7. 7. The magnetic heat pump according to claim 6, The heat generation flow path and the heat absorption flow path are partially common to each other, The flow path further includes a switching valve that switches between the heat generation flow path and the heat absorption flow path.

8. 7. The magnetic heat pump according to claim 6, A magnetic heat pump including a flow path control unit that selectively uses the flow path during heat generation and the flow path during heat absorption in conjunction with the state of current flow to the superconducting coil.

9. 9. The magnetic heat pump according to claim 8, The flow path control unit switches from the heat generation flow path to the heat absorption flow path with a predetermined delay from the timing when the current flow state to the superconducting coil changes from the current flow state that causes the magnetic working material to be in the heat generation state to the current flow state that causes the magnetic working material to be in the heat absorption state.

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