JP7544418B1 - Magnetic Heat Pump - Google Patents

Abstract

[Problem] To achieve energy saving when cooling a magnetic working material by applying a fluctuating magnetic field. [Solution] A magnetic working material 30 is placed inside a superconducting coil 31. A capacitor 32 is connected in series to the superconducting coil 31 via a switch 36. In addition, both ends of the superconducting coil 31 are connected via a switch 37. In this way, even if a current flows from a power source 33 to the superconducting coil 31 and then the power source 33 is cut off, the current to the superconducting coil 31 can be periodically changed by the LC resonant circuit, and the magnetic working material 30 can be switched between a heating state and a cooling state. In addition, by connecting both ends of the superconducting coil 31 to keep a constant current flowing, and by disconnecting both the superconducting coil 31 and the capacitor 32 to no current flowing, more effective heat exchange can be achieved. As a result, energy saving in cooling by a fluctuating magnetic field can be achieved. [Selected Figure] Figure 1

Description

Article 30, paragraph 2 of the Patent Act applies. 2023 Autumn Meeting of the Cryogenics and Superconductivity Society, Kaikyo Messe Shimonoseki (Shimonoseki City, Yamaguchi Prefecture), December 4, 2023 [Publications, etc.] 2023 Autumn Meeting of the Cryogenics and Superconductivity Society, Abstracts of Lectures, Cryogenics and Superconductivity Society of Japan, published December 4, 2023, ISSN 0919-5998

The present invention relates to a magnetic heat pump that cools a magnetic working material by applying a fluctuating magnetic field generated by a superconducting coil.

2. Description of the Related Art Conventionally, as refrigerators applicable to extremely low temperatures below liquid helium, magnetic refrigerators that use magnetic materials (hereinafter referred to as "magnetic working substances") that generate and absorb heat in response to a magnetic field are known.
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, a magnetic field is applied to the magnetic working material or blocked in response to the reciprocating motion of the magnetic shield, thereby changing the heat generation/absorption of the magnetic working material and realizing 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 the magnetic working material is placed inside the superconducting coil and a state in which the magnetic shield is placed inside the superconducting coil, thereby changing the heat generation/absorption of the magnetic working material and realizing refrigeration.

Japanese Patent Application Publication No. 4-273956 Japanese Patent Application Publication No. 6-151983

In conventional magnetic refrigeration technology, the generation of a magnetic field by a superconducting coil requires cooling to maintain the superconducting state, and although the lack of current loss has improved energy efficiency, the reciprocating motion of the magnetic shield or magnetic working material itself requires energy, 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 problems, an object of the present invention is to vary a magnetic field in an energy-saving manner and to realize magnetic refrigeration.

The present invention relates to
A magnetic heat pump that transports heat from an object to be cooled,
The magnetic working material is in a heat generating or heat absorbing state in response to a change in a magnetic field;
a superconducting coil for applying 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 provided with a heat exchange mechanism for exchanging heat between the magnetic working material and the object to be cooled.

In the present invention, since the LC resonant circuit is provided, the current flowing through the superconducting coil fluctuates at a period corresponding to the resonant frequency, which fluctuates the magnetic field applied to the magnetic working material, thereby realizing cooling. Moreover, since the electrical resistance of superconductivity is zero, 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 greatly reduce the energy required for cooling using the magnetic working material.

In the present invention, various substances such as gadolinium can be used as the magnetic working substance.
The shape and structure of the part of the heat exchange mechanism that exchanges heat with the magnetic working material can also be determined as desired. For example, a part 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 shape. 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 portion that exchanges heat with the object to be cooled may be, for example, a mechanism for passing a heat exchange medium, or may utilize heat conduction of metal or other materials. Various other configurations are also applicable.
The LC resonant circuit is designed to set a resonant frequency so as to effectively realize heat exchange, and the inductance of the superconducting coil and the capacitance of the capacitor are designed to achieve this. The resonant frequency can be determined arbitrarily, but can be set to a low frequency of, for example, about 0.1 Hz.

In the present 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;
There may be one or more switches for switching between a third state in which the superconducting coil and the capacitor are connected in series.

By doing so, 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, and in the third state, it is possible to vary the current flowing through the superconducting coil.
In this manner, according to the above embodiment, by separating the states, it becomes possible to control the magnetic field applied to the magnetic working material.

In the embodiment 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 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.

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 stop immediately just because the magnetic field fluctuations have stopped. The above embodiment has the advantage that the heating and cooling states of the magnetic working material can be maintained even after the magnetic field fluctuations have stopped by controlling the current to maintain the first and second states, respectively.

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 each 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.

This has the advantage that the heat exchange medium can perform sufficient heat exchange.

If you want to be able to switch between the first, second and third states,
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.

In general, 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 can flow before the other switch is opened, thereby preventing the occurrence of an arc discharge.

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 includes:
a heat generation flow path when the magnetic working material is in the heat generation state;
and a heat absorption flow path when the magnetic working material is in the heat absorption state.

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 cooling state, it is preferable to perform heat exchange with the object to be cooled. In the above embodiment, since it is provided with a flow path suitable for each state, it is possible to realize appropriate heat exchange in both the heat generating state and the cooling state.

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.

This allows the heat exchange medium and its flow path to be shared, making it easier and less costly to configure than having separate flow paths for heat generation and cooling.

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 accordance with a state of current flow through the superconducting coil.
This makes it possible to selectively use the flow path during heat generation and the flow path during heat absorption in synchronization with the heat generation and heat absorption states of the magnetic working material.

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 at which the current flow state to the superconducting coil changes from the current flow state that brings the magnetic working material to the heat generation state to the current flow state that brings the magnetic working material to the heat absorption state.

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, there is a risk that the heat medium that has received heat during the heat generation will flow into the heat absorption flow path. According to the above embodiment, the switching is performed after a delay of a while after the switch to the heat absorption state, so this kind of problem can be avoided.

The present invention does not need to have all of the various features described above, and can be configured by omitting or combining some of them as appropriate. In addition to the magnetic heat pump, the present invention may also be configured in the form of a magnetic refrigeration method using a magnetic working material.

FIG. 1 is an explanatory diagram showing a configuration of a magnetic heat pump. FIG. 4 is an explanatory diagram showing a switching mode. FIG. 11 is an explanatory diagram showing a switching sequence.

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

FIG. 1 is an explanatory diagram showing the configuration of a magnetic heat pump.
A superconducting coil 31 is placed in the sealed vessel 10. The superconducting coil 31 is cooled to achieve superconductivity, but this cooling mechanism is omitted from the drawing to avoid complicating the drawing.

In the internal space of the superconducting coil 31, a magnetic working material 30 is installed, which generates heat/absorbs heat depending on the state of the magnetic field. 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 filling a hollow thin wire made of copper or other material with good thermal conductivity with a powder of dysprosium alloy, producing a thin wire by a so-called powder-in-tube manufacturing technique, and weaving the thin wire. The magnetic working material 30 is not limited to such a configuration, and may be made of a lump of dysprosium alloy. However, these are only examples, and the gadolinium alloy (e.g., Gd ₅ Ge ₄ ) is not excluded.

The flow paths 21-24 through which the heat exchange medium flows are provided to pass through the magnetic working material 30. When the magnetic working material 30 generates/absorbs heat due to the action of the magnetic field, the corresponding heat is transmitted by the heat exchange medium in the flow paths 21-24.

A heat exhaust unit 20 is attached to the outside of the sealed container 10 above the flow paths 21 and 22. 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 exhausted 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, and detailed description thereof 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, and the hydrogen storage tank 12 is cooled. Conversely, when the magnetic working material 30 absorbs heat, the transfer of heat to the hydrogen storage tank 12 is blocked, and it is possible to prevent the cooling of the hydrogen storage tank 12 from being hindered.

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 as to circulate the heat exchange medium so as to bypass the heat exhaust section 20. When the magnetic working material 30 is in a heat absorption state, it 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 for short-circuiting the flow paths 23, 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, it is possible to prevent the cooling of the hydrogen storage tank 12 from being hindered by bypassing the hydrogen storage tank 12, which is the object to be cooled. This state is 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 carry out heat exchange during heat absorption and heat generation.
In the embodiment, the switching mechanisms 26, 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.

The superconducting coil 31 is connected to a circuit including a power source 33 and a capacitor 32. The power source 33 can be a system power source, a battery, or any other type of power source. In the circuit, the power source 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 source 33, a switch 36 is provided between the short circuit and the capacitor 32, and a switch 37 is provided in the short circuit. By opening and closing these switches 35 to 37, the following circuit configuration is realized.
With the switches 35 and 36 closed and the switch 37 open, a closed circuit is formed connecting the power supply 33 and the superconducting coil 31. It is only in this state that the switch 35 is closed.
When the switches 35 to 37 are all open, the superconducting coil 31, the capacitor 32, and the power source 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 .

The operation of the magnetic heat pump is controlled by a control device 40. The control device 40 can be configured as a computer 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 35-37, a flow path control function for controlling the switching mechanisms 26, 27 to switch between the flow paths for heat generation and the flow paths for cooling, and a heat exhaust control function for controlling the operation of the heat exhaust section 20. All or part of these functions may be configured by hardware such as an ASIC.

FIG. 2 is an explanatory diagram showing a switching mode.
First, when a closed circuit is formed between the power source 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 of FIG. 2 are entered.

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 through superconducting coil 31, in FIG. 2(a) the current continues to flow in a fixed direction (clockwise in the figure).

2B, 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 flowed 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.

If left as is, current will then begin to flow in the opposite direction from capacitor 32 to superconducting coil 31, and resonance will begin due to the LC resonant circuit. In this embodiment, it is acceptable to allow such resonance to occur, but 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.

Next, as shown in FIG. 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 the power source, and current begins to flow counterclockwise as shown. This state continues until the charge in capacitor 32 is completely discharged.

If left as is, this time superconducting coil 31 will start charging capacitor 32, and resonance will begin with the LC resonant circuit. There is no harm in allowing this resonance to occur, but in order to more actively control the period during which current flows, as soon as the charge in capacitor 32 is released, switch 36 is opened and switch 37 is closed, as shown in Figure 2(e). This allows counterclockwise current to continue to flow through superconducting coil 31.

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.

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 with no current flowing through it.

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 flows counterclockwise as shown in the figure. This state continues until the charge in capacitor 32 is completely discharged.
Then, the state returns to that shown in FIG.

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 flows, but the cooled state shown in Fig. 2(b) continues for a while.
The state shown in Fig. 2(d) is a period in which the current to the superconducting coil 31 is increasing, and the magnetic working material 30 is in a heat generating state. In Fig. 2(e), no current is flowing, but the heat generating state shown in Fig. 2(d) continues for a while.
Similarly, Figs. 2(f) and 2(g) show the cooling state, and Figs. 2(h) and 2(a) show the heating state.
In this manner, in this embodiment, by performing the switching shown in FIG. 2, the current to the superconducting coil 31 can be changed by utilizing 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.

3 is an explanatory diagram showing a switching sequence. The broken lines L36 and L37 show the ON (closed) and OFF (open) changes of the switches 36 and 37, and the accompanying change in current is shown diagrammatically in 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 the maximum value.
During a 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 a period (c) (corresponding to FIG. 2(c)), the switches 36 and 37 are both OFF, and the current is 0. The magnetic working material 30 is maintained in a cooled state for a while.
During a period (d) (corresponding to FIG. 2(d)), the switch 36 is ON, the switch 37 is OFF, and the current in the reverse direction increases gradually with the capacitor 32 as the power source. This causes the magnetic working material to generate heat.
During a period (e) (corresponding to FIG. 2(e)), the switch 36 is OFF, the switch 37 is ON, and the reverse current is constant at a maximum value. The magnetic working material 30 maintains a heated state for a while.
During a period (f) (corresponding to FIG. 2(f)), the switch 36 is ON and the switch 37 is OFF, and the reverse current decreases as the capacitor 32 is charged. This causes the magnetic working material 30 to cool.
During a period (g) (corresponding to FIG. 2(g)), the switches 36 and 37 are both OFF, and the current is 0. The magnetic working material 30 is maintained in a cooled state for a while.
During a period (h) (corresponding to FIG. 2(h)), the switch 36 is ON, the switch 37 is OFF, and the current in the reverse direction increases gradually with the capacitor 32 as the power source. This causes the magnetic working material to generate heat.

The lower part of the figure shows an enlarged detailed switching procedure when switching from period (a) to period (b). In this switching, the switch 36 is switched from OFF to ON, and the switch 37 is switched from ON to OFF. At this time, if the timing of switching the switch 37 to OFF is even a moment earlier than the timing of switching the switch 36 to ON, an instant occurs when both the switches 36 and 37 are turned OFF. When a current is flowing as in period (a) and both switches are suddenly turned OFF in this manner, an arc discharge usually occurs. In this embodiment, in order to avoid this, as shown in the figure, the switching is controlled so that the switch 36 is first turned ON, and then the switch 37 is turned OFF after a very short time dt has elapsed. In this way, the occurrence of an arc discharge can be avoided. The very short time dt can be determined arbitrarily within a range in which an arc discharge can be avoided.
Such control of delaying the turning off of the switch is also applied when switching from period (e) to period (f).

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

Next, when the period (c) transitions to the period (d), the magnetic working material 30 becomes in a heat generating state, and the heat exchange mechanism switches to the heat generating flow path. In this case, since there is no risk of impeding the cooling of the hydrogen storage tank 12, the heat exchange mechanism switches to the heat generating flow path at timing B2, which is the same as 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.

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).
In this way, effective heat exchange can be achieved.

As shown in Fig. 3, the switching sequence of this embodiment has 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 and cooled states are maintained. Therefore, by providing the maximum current holding periods and zero current holding periods, the heated and cooled states 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 heating 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 that exchanges heat with the magnetic working material 30.

The time required for the magnetic working material 30 to become heated or cooled is determined by the time required 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 that there is 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) are at least longer than the time required for the heat exchange medium to flow through the portion where heat exchange with the magnetic working material 30 takes place.

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

It is not necessary to provide all of the various features described above, and some of them may be omitted or combined as appropriate.
Furthermore, the present invention is not limited to the above-mentioned embodiment, and various modifications can be made. In the embodiment, an example of a magnetic heat pump for condensing hydrogen is shown, but the present invention can be used for other purposes. For example, the present invention may be used as a refrigeration or cooling system that is not intended for condensing hydrogen, such as a cooling system for a nuclear fusion coil or a superconducting power storage system.

The present invention can be applied to cooling by applying a fluctuating magnetic field using a superconducting coil to a magnetic working material.

10: sealed container 12: hydrogen storage tank 20: heat exhaust section 21, 22, 23, 24: flow path 25: thermal switch 26, 27: switching mechanism 30: magnetic working material 31: superconducting coil 32: capacitor 33: power source 35, 36, 37: switch 40: control device

Claims (8)

A magnetic heat pump that transports heat from an object to be cooled,
a magnetic working material that becomes exothermic or absorbing in response to a change in a magnetic field;
a superconducting coil for applying 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 heat exchange mechanism for exchanging heat between the magnetic working material and the object to be cooled ;
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 magnetic heat pump comprising one or more switches for switching between a third state in which the superconducting coil and the capacitor are connected in series . 2. The magnetic heat pump according to claim 1 ,
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. 3. The magnetic heat pump according to claim 2 ,
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,
A 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. 3. The magnetic heat pump according to claim 2 ,
There are a plurality of the switches,
The switch control unit controls, when switching between the first to third states, to close any of the switches that have been open and then open the switch that has been closed. 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 includes:
a heat generation flow path when the magnetic working material is in the heat generation state;
a heat absorption flow path when the magnetic working material is in the heat absorption state. 6. The magnetic heat pump according to claim 5 ,
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. 6. The magnetic heat pump according to claim 5 ,
A magnetic heat pump comprising a flow path control unit that selectively uses the flow path during heat generation and the flow path during heat absorption in accordance with a current supply state to the superconducting coil. 8. The magnetic heat pump according to claim 7 ,
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 brings the magnetic working material to the heat generation state to the current flow state that brings the magnetic working material to the heat absorption state.