Heat storage body and heating apparatus

Abstract

To provide a heat storage body that enables maintenance of the temperature of an object to be heated in a broader temperature region.SOLUTION: A heat storage body includes two or more kinds of heat storage particles having different particle diameters D50, where each of the two or more kinds of heat storage particles has a phase change type heat storage material capable of heat storage and heat release utilizing solid-liquid phase change.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a heat storage body and a heating device. [Background technology]

[0002] Phase-change heat storage bodies that are capable of storing and releasing heat by utilizing solid-liquid phase changes are known. For example, Patent Document 1 discloses a heat storage body that includes two or more types of phase-change heat storage materials with different melting points. The heat storage body disclosed in Patent Document 1 includes two or more types of phase-change heat storage materials with different melting points, and therefore has multiple temperature ranges in which heat release occurs. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-91759 Summary of the Invention [Problem to be solved by the invention]

[0004] The heat storage body disclosed in Patent Document 1 has multiple temperature ranges in which heat dissipation occurs, and therefore can maintain the temperature of the object to be heated over a wider temperature range than when there is only a single temperature range in which heat dissipation occurs. However, there has been a demand for a heat storage body that can maintain the temperature of the object to be heated over an even wider temperature range. An object of the present invention is to provide a heat storage body that can maintain the temperature of an object to be heated over a wider temperature range. [Means for solving the problem]

[0005] The gist of one embodiment of the present invention is that the heat storage body comprises two or more types of heat storage particles with different particle diameters D50, and each of the two or more types of heat storage particles has a phase-change type heat storage material that can store and release heat by utilizing a solid-liquid phase change. A heating device according to another aspect of the present invention includes the heat storage body according to the above aspect. [Effects of the Invention]

[0006] According to the present invention, it is possible to maintain the temperature of the object to be heated over a wider temperature range. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram showing the results of thermal analysis of the heat storage bodies of the examples and comparative examples. [Figure 2] FIG. 10 is a diagram showing the results of thermal analysis of a heat storage medium of a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0008] An embodiment of the present invention will be described below. Note that this embodiment is merely an example of the present invention, and the present invention is not limited to this embodiment. Furthermore, various modifications and improvements can be made to this embodiment, and such modifications and improvements can also be included in the present invention.

[0009] The heat storage body according to this embodiment comprises two or more types of heat storage particles with different particle diameters D50, and each of the two or more types of heat storage particles has a phase-change type heat storage material capable of storing and releasing heat by utilizing a solid-liquid phase change. Since heat storage particles with different particle diameters D50 release heat in different temperature ranges, if the heat storage material according to this embodiment is used to heat an object when its temperature drops, heat will be released from the heat storage material in multiple temperature ranges, heating the object. Therefore, even if the temperature of the object drops, it is possible to suppress the temperature drop of the object over a wider temperature range.

[0010] In order to suppress a temperature drop in the heated object over a wider temperature range, it is preferable that heat dissipation occurs from the heat storage material over a wider range of temperatures, and therefore it is preferable to have as many types of heat storage particles with different particle diameters D50 as possible. That is, although two types of heat storage particles with different particle diameters D50 may be used, three or more types are preferable, four or more types are more preferable, and five or more types are even more preferable.

[0011] Furthermore, in order to suppress the temperature drop of the heated object over a wider temperature range, it is preferable that the temperature ranges in which heat dissipation occurs for different types of heat storage particles partially overlap, which results in a state in which the heated object is heated continuously as the temperature drops, rather than being heated intermittently as the temperature drops, making it easier to suppress the temperature drop of the heated object.

[0012] By selecting the type of phase-change type heat storage material, it is possible to make the temperature ranges in which heat dissipation occurs from the heat storage particles overlap partially. However, even if the type of phase-change type heat storage material is the same, it is possible to make the temperature ranges in which heat dissipation occurs from the heat storage particles overlap partially by selecting the particle diameter D50 of the heat storage particles. The particle diameter D50 is the particle diameter at which the cumulative particle volume from the small particle diameter side in the volume-based cumulative particle diameter distribution is 50% of the total particle volume.

[0013] If the particle diameter D50 of the heat storage particle with the largest particle diameter D50 is D1 and the particle diameter D50 of the heat storage particle with the second largest particle diameter D50 is D2, in order to ensure that the temperature ranges in which heat dissipation occurs from the heat storage particles overlap partially, the ratio D1 / D2 of D1 to D2 is preferably 1.5 or more and 15 or less, and more preferably 1.9 or more and 7.5 or less.

[0014] Furthermore, the particle diameter D50 of the heat storage particles is not particularly limited, but the particle diameters D50 of the two or more types of heat storage particles are preferably all 10 μm or more and 300 μm or less, and more preferably all 20 μm or more and 100 μm or less. The smaller the particle diameter D50 of the heat storage particles, the faster the melting and solidification rates of the heat storage particles, so that the heat storage and heat release by the heat storage material according to this embodiment can be performed in a short time (i.e., the heat storage rate and heat release rate tend to be high).

[0015] The use of the heat storage body according to this embodiment is not particularly limited, but it can be used, for example, to suppress a drop in catalyst temperature. Here is one example of its use. A catalyst for purifying exhaust gas is installed in an automobile, and the temperature of the catalyst drops when the engine is stopped. To suppress this, the heat storage body according to this embodiment can be used. By heating the catalyst installed in the automobile using heat radiation from the heat storage body according to this embodiment, the temperature of the catalyst can be maintained at a temperature at which the catalyst is activated (for example, 300 to 400°C) without using electrical energy. A heating device equipped with the heat storage body according to this embodiment may be installed in the automobile, and the catalyst can be heated by the heating device. The heat storage body according to this embodiment will be described in further detail below.

[0016] (1) Phase change heat storage materials The type of phase-change heat storage material is not particularly limited as long as it is capable of storing and releasing heat by utilizing a solid-liquid phase change, but metals or alloys are suitable as phase-change heat storage materials. Specific examples of metals include aluminum (Al), zinc (Zn), magnesium (Mg), lead (Pb), tin (Sn), and indium (In). Specific examples of alloys include aluminum alloys, zinc alloys, magnesium alloys, tin alloys, and indium alloys.

[0017] Aluminum alloys are alloys containing at least one of silicon (Si), magnesium, copper (Cu), zinc, etc. as alloying components, with aluminum being the predominant component. Zinc alloys are alloys containing at least one of aluminum, copper, magnesium, etc. as alloying components, with zinc being the predominant component. Magnesium alloys are alloys containing at least one of aluminum, zinc, etc. as alloying components, with magnesium being the predominant component.

[0018] Although the alloy composition ratio of these alloys is not particularly limited, it is preferable that the alloy composition ratio has a eutectic point. An alloy having a eutectic point is unlikely to undergo changes in its crystalline structure even when it undergoes repeated phase changes (repeated melting and solidification), and therefore its performance as a heat storage material is unlikely to deteriorate.

[0019] The type of aluminum alloy is not particularly limited, but examples include 4000-series aluminum alloys (aluminum-silicon alloys) containing silicon as an alloying component, 5000-series aluminum alloys containing magnesium as an alloying component, 6000-series aluminum alloys containing silicon and magnesium as alloying components, and 7000-series aluminum alloys containing zinc and magnesium as alloying components. The alloy composition ratio of the aluminum-silicon alloy is not particularly limited, but a preferred ratio is 60 atomic % to 99 atomic % aluminum and 1 atomic % to 40 atomic % silicon. For example, an aluminum-silicon alloy containing 88 atomic % aluminum and 12 atomic % silicon is suitable because it has a eutectic point.

[0020] The melting point of the metal or alloy used as the phase-change heat storage material is not particularly limited, but is preferably 300° C. to 600° C., and more preferably 350° C. to 400° C. The melting point of an aluminum-silicon alloy with an alloy composition ratio of 88 atomic % aluminum and 12 atomic % silicon is 573° C.

[0021] (2) Heat storage particles All of the heat storage particles contain a phase-change heat storage material capable of storing and releasing heat by utilizing a solid-liquid phase change. However, to prevent adjacent heat storage particles from mixing when the phase-change heat storage material melts, the heat storage particles may be encapsulated in an encapsulating material. For example, the heat storage particles may be held in a dispersed state inside the encapsulating material. In this case, two or more types of heat storage particles with different particle diameters D50 may be dispersed inside a single encapsulating material. Alternatively, each type of heat storage particle may be dispersed inside a different encapsulating material. In other words, one type of heat storage particle may be dispersed inside one type of encapsulating material, and another type of heat storage particle may be dispersed inside a different type of encapsulating material.

[0022] The material of the encapsulating material is not particularly limited as long as it can hold the heat storage particles in a dispersed state, but an inorganic compound can be used. The encapsulating material may be formed of one type of inorganic compound or multiple types of inorganic compounds. Examples of inorganic compounds include silicon carbide (SiC), inorganic oxides, inorganic nitrides, and metal salts. Specific examples of inorganic oxides include metal oxides such as alumina (Al2O3), titanium oxide (TiO2), and zirconium oxide (ZrO2). Alumina with a high α-alumina content is preferable. Because α-alumina has high thermal conductivity, the higher the α-alumina content in the encapsulating material, the more efficient the heat transfer, enabling heat storage and release in a short period of time.

[0023] Furthermore, when the phase-change-type heat storage material is a metal or an alloy, the heat storage particles formed of the metal or alloy may be covered with a coating formed of a metal oxide. In this configuration, the coating formed of the metal oxide exhibits the same effect as the above-mentioned encapsulating material, so that mixing of adjacent heat storage particles when the phase-change-type heat storage material melts is suppressed.

[0024] (3) How to use the heat storage material The method for using the heat storage material according to this embodiment is not particularly limited, but it can be used, for example, in the following manner: An example of a method for using the heat storage material according to this embodiment will be described.

[0025] The heat storage body according to this embodiment is heated to a temperature equal to or higher than the melting point of the phase-change heat storage material that forms the heat storage particles. At this time, the heat storage particles melt, causing heat absorption (i.e., the heat storage body stores heat). Next, the heated heat storage body according to this embodiment is cooled to a temperature equal to or lower than the melting point of the phase-change heat storage material that forms the heat storage particles. At this time, the melted heat storage particles solidify, causing heat generation (i.e., the heat storage body releases heat).

[0026] Next, the method of using the heat storage body according to this embodiment will be described in more detail, taking as an example a case where the heat storage body is used to suppress a temperature drop in a catalyst for purifying exhaust gas from an automobile. The heat storage body or the heating device according to this embodiment is installed near a catalyst mounted on an automobile. When the automobile engine is started, the temperature of the catalyst rises, and so does the temperature of the heat storage body. At this time, the heat storage particles melt, and the heat storage body stores heat. Next, when the automobile engine is stopped, the temperatures of the catalyst and the heat storage body drop (the rate at which the temperature of the catalyst and the heat storage body drops when the engine is stopped is, for example, 5°C / min or more and 100°C / min or less), but when the heat storage particles solidify, the heat storage body releases heat. This heat release suppresses the temperature drop of the catalyst, and the temperature of the catalyst can be maintained at a temperature at which the catalyst is activated without using electrical energy. [Example]

[0027] The present invention will be described in more detail below with reference to examples and comparative examples. Example 1 Spherical aluminum-silicon alloy powder Al-12Si manufactured by Hikari Materials Industry Co., Ltd. was classified to obtain a powder consisting of particles with a particle size of 58 μm or less. This classified powder was then further classified using a sieve with a mesh size of 38 μm, and separated into powder remaining on the sieve and powder that passed through the sieve.

[0028] The particle size D50 was measured using a laser diffraction particle size distribution analyzer, and the particle size D50 of the powder remaining on the sieve was 59 μm, while the particle size D50 of the powder that passed through the sieve was 31 μm. The spherical powder Al-12Si was produced by atomization. The aluminum silicon alloy had an alloy composition ratio of 88 mass % aluminum and 12 mass % silicon.

[0029] Equal masses of "powder remaining on the sieve (particle diameter D50: 59 μm)" and "powder that passed through the sieve (particle diameter D50: 31 μm)" were weighed and mixed to obtain a mixed powder. A 5 mg sample of this mixed powder was then subjected to differential thermal analysis. The differential thermal analysis was performed in an air flow at a flow rate of 100 mL / min. The sample was heated to 600°C and held there for 30 minutes, then cooled at a rate of 10°C / min while measuring the voltage change. The results are shown in Figure 1. The D1 / D2 ratio was 1.903.

[0030] Comparative Example 1 A differential thermal analysis was carried out using the "sieved powder (particle diameter D50 is 31 μm)" used in Example 1 as a sample. The conditions for the differential thermal analysis were the same as those in Example 1. The results are shown in FIG. 1.

[0031] Comparative Example 2 A differential thermal analysis was performed on the "powder remaining on the sieve (particle diameter D50: 59 μm)" used in Example 1 as a sample. The conditions for the differential thermal analysis were the same as those in Example 1. The results are shown in FIG. 1.

[0032] Comparative Example 3 Spherical zinc-aluminum alloy powder Zn-10Al manufactured by Hikari Materials Industry Co., Ltd. was prepared. The particle diameter D50 was measured using a particle size distribution analyzer and found to be 31 μm. This spherical powder Zn-10Al was produced by an atomization method. The alloy composition ratio of the zinc-aluminum alloy was 90 mass% zinc and 10 mass% aluminum.

[0033] The same masses of spherical zinc-aluminum alloy powder Zn-10Al and the "sieved powder (particle diameter D50: 31 μm)" used in Example 1 were weighed and mixed to obtain a mixed powder. Five mg of this mixed powder was then used as a sample to perform differential thermal analysis. The conditions for differential thermal analysis were the same as those in Example 1. The results are shown in FIG. 2.

[0034] 1, it can be seen that the length of time that the heat storage body of Example 1 dissipates heat is 1.8 minutes. Similarly, the length of time that the heat storage body of Comparative Example 1 dissipates heat is 0.9 minutes, and in the case of Comparative Example 2 it is 0.3 minutes. In this way, the heat storage body of Example 1 was able to continuously dissipate heat for a longer period of time than the heat storage bodies of Comparative Examples 1 and 2. In other words, the heat storage body of Example 1 was able to continuously dissipate heat over a wider temperature range than the heat storage bodies of Comparative Examples 1 and 2.

[0035] Therefore, the heat storage body of Example 1 can suppress the temperature drop of the heated object over a wider temperature range than the heat storage bodies of Comparative Examples 1 and 2, and can therefore maintain the temperature of the heated object over a wider temperature range. The length of time during which the voltage change measured in differential thermal analysis was 5 μV or more was defined as the length of time during which the heat storage body was radiating heat.

[0036] 2, the heat storage body of Comparative Example 3 releases heat in two temperature ranges, but cannot release heat continuously, and the lengths of time during which the heat storage body of Comparative Example 3 releases heat are 0.9 minutes and 0.5 minutes. Since there is a time (temperature range) during which no heat is released between the two heat releases, it is thought that the temperature drop of the heated object cannot be sufficiently suppressed.

[0037] Furthermore, when comparing the temperature range in which the lower-temperature heat dissipation of the two types of heat dissipation occurred in the heat storage body of Example 1 with the temperature range in which heat dissipation occurred in the heat storage body of Comparative Example 2, the temperature ranges are different even though the heat dissipation is caused by the same heat storage particles, and the heat storage body of Example 1 dissipates heat at a lower temperature. This is thought to be because the higher-temperature heat dissipation of the two types of heat dissipation occurred in the heat storage body of Example 1 heated the heat storage particles that caused the lower-temperature heat dissipation, and therefore delayed cooling to the temperature range in which heat dissipation occurred.

[0038] Furthermore, in order to make the heat radiating time length the same between the heat storage body of Example 1 and the heat storage body of Comparative Example 1, it is necessary to use twice the amount of the heat storage body of Comparative Example 1 as the amount of the heat storage body of Example 1. Therefore, the heat storage body of Example 1 can suppress the temperature drop of the heated object with 50% of the amount of the heat storage body of Comparative Example 1, and therefore the cost can be reduced by 50%.

[0039] Example 2 Spherical aluminum-silicon alloy powder Al-12Si manufactured by Hikari Materials Industry Co., Ltd. was classified using a sieve and separated into powder remaining on the sieve and powder that passed through the sieve. The particle diameter D50 was measured using a laser diffraction particle size distribution device, and the particle diameter D50 of the powder remaining on the sieve was 31 μm, while the particle diameter D50 of the powder that passed through the sieve was 20 μm.

[0040] The same masses of "powder remaining on the sieve (particle diameter D50 is 31 μm)" and "powder that passed through the sieve (particle diameter D50 is 20 μm)" were weighed and mixed to obtain a mixed powder. Five mg of this mixed powder was then used as a sample for differential thermal analysis. The conditions for differential thermal analysis were the same as in Example 1. The D1 / D2 ratio was 1.55. Furthermore, according to the above definition, the heat release time of the heat storage body of Example 2 was 1.0 minute.

[0041] Comparative Example 4 Differential thermal analysis was performed on the "sieved powder (particle diameter D50 is 31 μm)" used in Example 2 as a sample. The conditions for differential thermal analysis were the same as those in Example 1. According to the above definition, the heat release time of the heat storage material of Comparative Example 4 was 0.3 minutes.

[0042] Comparative Example 5 Differential thermal analysis was performed on the "sieved powder (particle diameter D50 is 20 μm)" used in Example 2 as a sample. The conditions for differential thermal analysis were the same as those in Example 1. According to the above definition, the heat release time of the heat storage material of Comparative Example 5 was 0.2 minutes.

[0043] It can be seen that the length of time that the heat storage body of Example 1 dissipates heat is 1.8 minutes. Similarly, the length of time that the heat storage body of Comparative Example 1 dissipates heat is 0.9 minutes, and in the case of Comparative Example 2 it is 0.3 minutes. In this way, the heat storage body of Example 1 was able to continuously dissipate heat for a longer period of time than the heat storage bodies of Comparative Examples 1 and 2. In other words, the heat storage body of Example 1 was able to continuously dissipate heat over a wider temperature range than the heat storage bodies of Comparative Examples 1 and 2.

[0044] The length of time that the heat storage body of Example 2 dissipates heat is 1.0 minute. Similarly, the length of time that the heat storage body of Comparative Example 4 dissipates heat is 0.3 minute, and in the case of Comparative Example 5 it is 0.2 minute. In this way, the heat storage body of Example 2 was able to continuously dissipate heat for a longer period of time than the heat storage bodies of Comparative Examples 4 and 5. In other words, the heat storage body of Example 2 was able to continuously dissipate heat over a wider temperature range than the heat storage bodies of Comparative Examples 4 and 5.

Claims

1. A heat storage body comprising two or more types of heat storage particles having different particle diameters D50, wherein the two or more types of heat storage particles are all made of a phase change type heat storage material capable of storing and releasing heat by utilizing a solid-liquid phase change.

2. 2. The heat storage material according to claim 1, wherein the particle diameter D50 of the heat storage particles having the largest particle diameter D50 is D1 and the particle diameter D50 of the heat storage particles having the second largest particle diameter D50 is D2, and the ratio D1 / D2 of D1 to D2 is 1.5 or more and 15 or less.

3. 3. The heat storage medium according to claim 1, wherein the particle diameter D50 of each of the two or more types of heat storage particles is 10 μm or more and 300 μm or less.

4. 3. The heat storage medium according to claim 1, wherein the phase-change type heat storage material is a metal element or an alloy.

5. 5. A heat storage body according to claim 4, wherein said alloy is an aluminum silicon alloy.

6. A heating device comprising the heat storage medium according to claim 1 or 2.

Images