JP6772878B2 - Thermal management method - Google Patents

Description

The present invention relates to a heat management method, particularly a heat management method using a material exhibiting a negative electric calorific value effect.

Currently, a system using a gaseous refrigerant is the mainstream for a heat management system, particularly a cooling system. As a thermal management system that replaces such a system, a solid-state cooling system that uses the Electrocaloric effect (ECE), which is a heat absorption phenomenon that utilizes the change in entropy when an electric field is applied to a ferroelectric or antiferroelectric. Is being considered.

In the normal electric calorific value effect (hereinafter, also referred to as "positive electric calorific value effect"), the temperature of the material rises when an electric field is applied, and decreases when the electric field is removed. However, in some antiferroelectrics, contrary to the positive electrocaloric effect, a negative electrocaloric effect is observed in which the temperature drops when an electric field is applied and the temperature rises when the electric field is removed.

For example, Non-Patent Document 1, a material exhibiting a negative electric caloric _effect, discloses a single crystal of _{(Pb 0.97 La 0.02) (Zr} 0.66 Sn 0.23 Ti 0.11) O 3 ing. In Non-Patent Document 1, the above-mentioned single crystal has a positive electric calorific value by using a method called Direct EC measurement method for indirectly calculating the temperature change ΔT due to the electric calorific value effect from the measurement of the temperature dependence of PE hysteresis. It shows that the material has both an effect and a negative electrocaloric effect.

Fangping Zhuo et al., Applied Physics Letters 108, 082904 (2016)

The present inventor examined a material system in which a positive electric heat effect and a negative electric heat effect coexist as described above. In such a material system, the positive electric heat effect and the negative electric heat effect cancel each other out. In addition, I noticed that the overall effect of the amount of electric heat of the material system as a whole is reduced.

An object of the present invention is to provide a method for obtaining a larger electric heat quantity effect in a material system in which a positive electric heat quantity effect and a negative electric heat quantity effect coexist.

As a result of diligent studies to solve the above problems, the present inventor maximizes the electric heat quantity effect of the material system as a whole even in a material system showing a negative electric heat quantity effect by using a specific electric field application method. We have found that it can be obtained and have reached the present invention. Specifically, an electric field showing a negative electric heat effect is first applied to a material showing an electric heat effect, then an electric field showing a positive electric heat effect is applied, and then the first negative electric heat effect is applied. Return the indicated electric field to the applied state. By repeating this cycle, it is possible to prevent the positive electrocaloric effect and the negative electrocaloric effect from canceling each other out.

According to the first gist of the present invention, it is a heat management method using a material exhibiting a negative electric calorific value effect, from at least two electrodes and a material exhibiting a negative electric calorific value effect located between the electrodes. An electric field E1 in which a material showing an electric heat effect shows a negative electric heat effect and an electric field E2 in which a material showing an electric heat effect shows a positive electric heat effect are provided in a heat management element having an insulating portion. , A thermal management method is provided, which comprises applying alternately.

According to the present invention, the material showing a negative electric heat effect is an electric field E1 in which the material showing an electric heat effect shows a negative electric heat effect, and the material showing an electric heat effect is an electric field E2 showing a positive electric heat effect. By alternately applying the above, a larger electric calorific value effect can be obtained. This enables more effective heat management.

FIG. 1 is a schematic cross-sectional view of the heat management element used in the present invention. FIG. 2 is a schematic cross-sectional view of another thermal management element used in the present invention. FIG. 3 is a circuit diagram for explaining a circuit including a thermal management element and a monopolar power supply in the embodiment. FIG. 4 is an electric field application profile applied to the heat management element in the embodiment. FIG. 5 shows the change in ΔT of the thermal management element of the embodiment. FIG. 6 is an electric field application profile applied to the heat management element in the comparative example. FIG. 7 shows the change in ΔT of the thermal management element of the comparative example. FIG. 8 is a graph showing the dependence of ΔT (temperature change of the material) on the applied electric field in a material in which a positive electric heat effect and a negative electric heat effect coexist.

Hereinafter, the thermal management method of the present invention will be described.

The "electric calorific value effect" means an effect in which the temperature of a specific material changes when an electric field is applied to the material. This temperature change is caused by the change in the orientation of the dipoles of the material due to the electric field. Compared with the case where no electric field is applied, the effect of increasing the entropy of the material by applying the electric field and lowering the temperature, that is, absorbing heat is called "negative electric heat quantity effect". Further, the effect of reducing the entropy of the material by applying an electric field and raising the temperature of the material, that is, dissipating heat is called "positive electric calorific value effect".

In the heat management method of the present invention, a heat management element having at least two electrodes and an insulating portion located between the electrodes and made of a material exhibiting a negative electric heat effect is used.

The material exhibiting the negative electric heat effect is a material that absorbs heat in an electric field of a certain size and generates heat in an electric field of another size according to the magnitude of the electric field when an electric field in a certain direction is applied. Typically, it means a material that absorbs heat in a low electric field and generates heat in a high electric field. FIG. 8 shows an applied electric field dependence diagram of ΔT (temperature change of the material) of a material exhibiting a typical negative electric heat effect.

The insulating portion is made of a material exhibiting a negative electric heat effect.

Examples of the material exhibiting the negative electrocaloric effect include antiferroelectric ceramics such as PbZrO ₃ , Pb (Zr, Sn, Ti, Nb) O ₃ , (Pb, La) (Zr, Ti) O ₃ . Examples thereof include organic antiferroelectrics such as PVDF / TrFE copolymers and proton transfer type antiferroelectrics such as imidazole compounds.

The shape of the insulating portion is not particularly limited, and can be formed into, for example, a sheet shape, a block shape, or various other shapes. Preferably, the insulating portion is in the form of a sheet or a block.

The insulating portion is obtained by molding a material exhibiting the negative electrocaloric effect. The molding method is not particularly limited, and compression, sintering, or the like can be used. Further, it may be molded by mixing with a binder such as resin or glass.

The insulating part has at least two electrodes. An electric field is formed by applying a voltage to these electrodes.

The material constituting the electrode is not particularly limited, and examples thereof include Ag, Cu, Pt, Ni, Al, Pd, Au, and alloys thereof (for example, Ag-Pd and the like). Of these, Pt, Ag, Pd or Ag-Pd are preferable.

The method for forming the electrode is not particularly limited, and plating, vapor deposition, baking of a metal paste, or the like can be used.

The structure and shape of the heat management element used in the present invention are not particularly limited as long as it has at least two electrodes and an insulating portion located between these electrodes.

For example, the thermal management element 1a as shown in FIG. 1 can be used. The thermal management element 1a includes a pair of electrodes 2 and 4 and an insulating portion 6 located between the pair of electrodes. When a voltage is applied between the electrodes 2 and 4, an electric field is applied to the insulating portion 6. As a result, the insulating portion 6 exhibits an electric heat quantity effect.

Further, the heat management element 1b as shown in FIG. 2 can be used. In the thermal management element 1b, a plurality of internal electrodes 12a and 12b and a plurality of insulating portions 14 are alternately laminated. The internal electrodes 12a and 12b are electrically connected to the external electrodes 16a and 16b arranged on the end faces of the heat management element 1b, respectively. When a voltage is applied from the external electrodes 16a and 16b, an electric field is applied between the internal electrodes 12a and 12b. As a result, the insulating portion 14 exhibits an electric heat quantity effect.

The thermal management element described above is typically connected to a circuit that includes a monopolar power supply.

The method of the present invention is characterized by a method of applying an electric field to an insulating portion of a heat management element. Hereinafter, the method of applying an electric field includes the following steps (1) to (4).

(1) An electric field E1 in which the material exhibiting the electric calorific value effect exhibits a negative electric calorific value effect is applied to the insulating portion.
(2) From the state in which the electric field E1 is applied to the insulating portion, the state in which the electric field E2 showing the positive electric heat effect is applied to the material showing the electric heat effect.
(3) From the state in which the electric field E2 is applied to the insulating portion, the state in which the material showing the electric heat quantity effect is applied to the electric field E1 showing the negative electric heat quantity effect.
(4) The above steps (2) and (3) are repeated.

The electric field E1 is not particularly limited as long as the material exhibiting a negative electric calorific value effect (hereinafter, also simply referred to as “electric calorific value effect material”) is an electric field exhibiting a negative electric calorific value effect. For example, in FIG. 8, E1 is an electric field in which ΔT is less than 0.

Preferably, E1 can be a high electric field (hereinafter, also referred to as "E1'") equal to or higher than the electric field in which the electric calorific value effect material exhibits the maximum negative electric calorific value effect. More preferably, E1 may be an electric field (hereinafter, also referred to as "E1 _max ") in which the electrocaloric effect material exhibits the greatest negative electrocaloric effect. Here, the "electric field in which the material showing the electric heat quantity effect shows the maximum negative electric heat quantity effect" is the electric field in which ΔT is the maximum on the negative side. Further, the "high electric field _{equal to} or higher than the electric field in which the material showing the electric heat quantity effect shows the maximum negative electric heat quantity effect" is the high electric field having E1 _max or more and showing the negative electric heat quantity effect. For example, in FIG. 8, E1 _max is an electric field in which ΔT is the minimum value. E1'is an electric field in which ΔT is less than 0, and is an electric field greater than or equal to the electric field in which ΔT is the minimum value.

In the state where the electric field E1 is applied to the insulating portion, the entropy of the electrocaloric effect material constituting the insulating portion is increased as compared with the state in which the electric field is not applied. In particular, when the applied electric field is E1 _max , the entropy of the electrocaloric effect material is maximized.

The electric field E2 is not particularly limited as long as the electric heat quantity effect material exhibits a positive electric heat quantity effect. For example, in FIG. 8, E2 is an electric field in which ΔT has a value larger than 0.

Preferably, E2 can be an electric field (hereinafter, also referred to as "E2 _max ") applied by the maximum voltage at which the insulating portion does not cause dielectric breakdown.

When the electric field E2 is applied to the insulating portion, the entropy of the electrocaloric effect material constituting the insulating portion is reduced as compared with the state where the electric field is not applied. In particular, when the applied electric field is E2 _max , the entropy of the electrocaloric effect material becomes smaller.

By applying the electric field E1 to the insulating portion in the above step (1), a state in which the electric field E1 is applied to the insulating portion can be obtained. As described above, in this state, the entropy of the electrocaloric effect material constituting the insulating portion is increased as compared with the state in which no electric field is applied.

Then, in the step (2), by changing the electric field applied to the insulating portion from E1 to E2 from this state, a state in which the electric field E2 is applied to the insulating portion can be obtained.

As described above, in the state where the electric field E2 is applied, the entropy of the electrocaloric effect material constituting the insulating portion is reduced as compared with the state where the electric field is not applied. That is, by changing the state in which the electric field E1 is applied to the insulating portion to the state in which the electric field E2 is applied to the insulating portion, the entropy is larger than that in the state in which the electric field is not applied, and the electric field is not applied. Beyond the entropy of the state, the entropy is smaller than that in the state where no electric field is applied. Therefore, if the entropy in the state where the electric field E1 is applied is En1, the entropy in the state where the electric field E2 is applied is En2, and the entropy in the state where the electric field is not applied is En0, then En1> En0> En2. That is, the amount of reduction in entropy in step (2) is En1-En2. This is larger than the amount of reduction in entropy by the conventional method of applying E2 from the state where no electric field is applied, En0-En2. That is, by using the management method of the present invention, it is possible to release a larger amount of heat than the conventional heat management method.

Next, in the step (3), the electric field E1 is applied to the insulating portion by changing the electric field applied to the insulating portion from E2 to E1 from the state where the electric field E2 is applied to the insulating portion.

In this step, the entropy of the electrocaloric effect material constituting the insulating portion increases from En2 beyond En0 to become En1. That is, the amount of increase in entropy in step (3) is En1-En2. This is larger than the amount of increase in entropy by the conventional method of removing the electric field from the state where E2 is applied, En0-En2. That is, by using the management method of the present invention, it is possible to absorb a larger amount of heat than the conventional heat management method.

Then, by repeating step (3) and step (2) (step (4)), it is possible to release and absorb a larger amount of heat than the conventional method.

In a preferred embodiment, E1 is E1'. By setting E1 to E1', the difference in the magnitude of the electric field from E2 becomes small, and the control of the electric field becomes easy. Further, in the change of the electric field from E1'to E2 or from E2 to E1', the electrocaloric effect material has a state in which ΔT becomes maximum on the negative side (a state in which ΔT becomes maximum entropy), that is, the electrocaloric effect material. Since the dipole does not go through the most disturbed state, a stable entropy effect can be exhibited.

In a more preferred embodiment, E1 is E1 _max . By setting E1 to E1 _max , the entropy of the state of the step (2) becomes larger, and the difference in entropy between the steps (2) and the step (3) becomes larger. This enables more efficient heat management.

In a preferred embodiment, E2 is E2 _max . By setting E2 to E2 _max , the entropy of the state of the step (3) becomes smaller, and the difference in entropy between the steps (2) and the step (3) becomes larger. This enables more efficient heat management.

In a more preferred embodiment, E1 is E1 _max and E2 is E2 _max . By setting E1 to E1 _max , the entropy of the state of step (2) becomes larger, and by setting E2 to E2 _max , the entropy of the state of step (3) becomes smaller, and the entropy of the state of step (2) and step (2) becomes smaller. The difference in entropy between (3) becomes larger. This enables more efficient heat management.

By using the heat management method of the present invention, an efficient heat transfer device, particularly a cooling device, can be obtained.

Therefore, the present invention also provides a heat transfer device using the heat management method of the present invention.

Furthermore, the present invention also provides an electronic component comprising the heat transfer device of the present invention, and an electronic device comprising the heat transfer device or the electronic component of the present invention.

The electronic components are not particularly limited, but for example, a central processing unit (CPU), a hard disk (HDD), a power management IC (PMIC), a power amplifier (PA), a transceiver IC, a voltage regulator (VR), and the like. Integrated circuits (ICs), light emitting diodes (LEDs), incandescent light bulbs, light emitting elements such as semiconductor lasers, components that can be heat sources such as field effect transistors (FETs), and other components such as lithium ion batteries, substrates, and heat sinks. , Parts generally used for electronic devices such as housings.

The electronic device is not particularly limited, and examples thereof include a mobile phone, a smartphone, a personal computer (PC), a tablet terminal, a hard disk drive, and a data server.

_{Pb 0.99 [(Zr 0.5 Sn 0.5} ) 0.97 Ti 0.03] 0.98 Nb 0.02 O 3 with ceramic as in Example electrical heat effect material element, use Pt as the electrode material We prepared a laminated thermal management element.

The laminated thermal management element obtained above and a monopolar power supply were connected in series to obtain a circuit as shown in FIG. By applying a voltage to the electrodes of the stacked heat management element using this circuit, a rectangular wave-shaped electric field application profile (FIG. 4) in which electric fields E1 and E2 are alternately applied to the stacked heat management element. An electric field was applied. The electric field is E1 = 10 MV / m (voltage 300 V) and E2 = 20 MV / m (voltage 600 V).

The temperature change ΔT due to the electric heat quantity effect was measured by continuously reading the temperature of the laminated heat management element when the electric field was changed using an ultrafine thermocouple having φ = 0.5 mm and a digital multimeter. The results are shown in FIG.

The temperature change ΔT due to the electric heat quantity effect was measured by the same operation as in the above embodiment except that the electric field corresponding to Comparative Example E1 was set to 0 MV / m (voltage 0 V). The electric field application profile is shown in FIG. 6 and the results are shown in FIG.

From FIGS. 5 and 7, it was confirmed that the example in which the electric field was applied at a cycle of 10 MV / m-20 MV / m had a larger ΔT than the comparative example in which the electric field was applied at a cycle of 0 MV / mV / mV / m. It was.

The heat management method of the present invention can be suitably used in various electronic devices, for example, heat management devices of small electronic devices such as mobile phones in which heat countermeasure problems are becoming prominent, particularly cooling devices.

1a, 1b ... Heat transfer device 2,4 ... Electrode 6 ... Dielectric part 12a, 12b ... Internal electrode 14 ... Dielectric layer 16a, 16b ... External electrode

Claims (3)

It is a heat management method using a material that shows a negative electric calorific value effect.
A material exhibiting an electric calorific effect exerts a negative electrocaloric effect on a heat management element having at least two electrodes and an insulating portion composed of a material exhibiting a negative electrocaloric effect located between the electrodes. A thermal management method comprising alternately applying an electric field E1 shown and an electric field E2 in which a material showing a positive electric heat effect shows a positive electric heat effect. The heat management method according to claim 1, wherein E1 is an electric field E1 _max in which the material exhibiting the electric calorific value effect has the maximum negative electric calorific value effect. The thermal management method according to claim 1 or 2, wherein E2 is the maximum electric field E2 _max at which the insulating portion does not cause dielectric breakdown.

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