coolant

Abstract

To provide a coolant having improved heat exchange capacity.SOLUTION: A coolant includes a base liquid and a fine particle having mono-dispersibility contained in the base liquid. The fine particle has a spherical silica porous body including a plurality of pores in an approximately columnar shape, a phase change material contained in the pores of the spherical silica porous body, and an outer shell part made of solid silica crystal that fills at least a part of the pores of the spherical silica porous body. In the spherical silica porous body, the pores have a uniform pore size and are radially arranged from the center toward the surface of the spherical silica porous body.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to coolants. [Background technology]

[0002] Conventionally, a technology has been proposed for storing heat by retaining a phase-change substance (latent heat storage material) that absorbs and releases latent heat in response to temperature changes in a solid form (see, for example, Patent Document 1). Patent Document 1 discloses a hard-shelled microencapsulated latent heat transport material in which a phase-change substance is encapsulated in porous hollow silica particles and a hard shell is formed on the surface of the particles.

[0003] Incidentally, heat transport systems using liquid heat transport fluids (hereinafter referred to as "coolants") have conventionally been adopted in the cooling systems of automobiles, electric aircraft, supercomputers, etc. In such heat transport systems, techniques have been studied to improve temperature control performance by using latent heat storage materials (hereinafter also simply referred to as "heat storage materials") (see, for example, Patent Documents 2 and 3).

[0004] Patent Document 2 discloses a cooling device for an electric motor that switches between using oil as a coolant and a heat storage material stored in a separate container. It states that this configuration improves the effect of suppressing the temperature rise of the electric motor and also suppresses the temperature drop of the coolant.

[0005] Patent Document 3 discloses a coolant composition containing microcapsules encapsulating a latent heat storage material, a base in which the microcapsules are dispersed, and a rust inhibitor. It states that by making the microcapsules concave, the thermal conductivity of the latent heat storage material during melting and solidification is improved. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2015 / 025529 [Patent Document 2] Japanese Patent Application Publication No. 2018-182854 [Patent Document 3] Patent No. 2013-112687 Summary of the Invention [Problem to be solved by the invention]

[0007] In the technology described in Patent Document 1, the phase change material may leak out of the porous hollow silica particles when forming the hard shell, potentially reducing the filling rate of the phase change material in the microcapsules. Furthermore, in the technology described in Patent Document 2, a separate container is required to store the heat storage material, which complicates the system and increases costs. Furthermore, in the technology described in Patent Document 3, the microcapsules are not spherical, which could lead to blockages at contracted flow sections in the coolant flow path.

[0008] The present invention aims to provide another technique for improving the heat exchange capacity of the coolant. [Means for solving the problem]

[0009] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0010] (1) According to one aspect of the present invention, there is provided a coolant comprising a base liquid and monodisperse microparticles contained in the base liquid, the microparticles comprising a spherical porous silica body having a plurality of substantially cylindrical pores formed therein, a phase-change material contained in the pores of the spherical porous silica body, and an outer shell formed of solid silica crystals and closing at least a portion of the pores of the spherical porous silica body, the pores of the spherical porous silica body having a uniform pore diameter and arranged radially from the center to the surface of the spherical porous silica body.

[0011] According to this configuration, the coolant contains monodisperse microparticles encapsulating a phase-change material in a base liquid. Because the microparticles function as a latent heat storage medium, when this configuration is used as a coolant for a battery or motor in an electric vehicle, for example, the phase-change material continues to absorb and release heat while melting or solidifying, maintaining the temperature near its melting point. This increases the temperature difference between the coolant and high-temperature objects such as the battery or motor, or the low-temperature external air in the radiator, thereby improving heat exchange capacity. Here, heat exchange capacity = coolant density × volumetric flow rate × specific heat × temperature difference.

[0012] Furthermore, because the microparticles have an outer shell, even if the microparticles come into contact with an organic solvent, the elution of the phase-change material encapsulated in the microparticles can be suppressed. Therefore, even if the organic solvent is mixed into the coolant, the elution of the phase-change material can be suppressed, and the deterioration of the heat exchange performance of the coolant can be suppressed. Furthermore, as the base liquid, an aqueous heat transfer medium containing an organic solvent (so-called emulsion-based coolant) or an organic heat transfer medium can be used.

[0013] Furthermore, because the microparticles are monodisperse, they are monodispersed in the base liquid, preventing a decrease in heat exchange capacity due to aggregation of the microparticles. Here, monodispersity refers to a state in which the particles are approximately uniform in size and easily dispersed without agglomeration. For example, a particle can be said to be "monodisperse" when the ratio (%) of the particle size distribution width to the average particle size is ±15% or less.

[0014] Furthermore, the spherical porous silica particles have multiple pores arranged radially from the center to the surface, and one end of the pores is not open, which further suppresses leakage of the phase-change material. Furthermore, because the pores are approximately cylindrical, the phase-change material is held in place by capillary force, and even if the phase-change material dissolves in the organic solvent, leakage to the outside is suppressed. As a result, the heat storage stability of the particles can be improved, and a decrease in the heat exchange capacity of the coolant can be suppressed.

[0015] (2) In the coolant of the above embodiment, the thickness of the outer shell of the microparticles may be 0.055 μm or more. This can further suppress elution of the phase-change material even when an organic solvent is mixed into the coolant or when an organic heat transfer medium is used as the base liquid. Therefore, it is possible to suppress a decrease in the heat exchange capacity of the coolant.

[0016] (3) In the cooling liquid of the above aspect, the absolute value of the zeta potential of the surfaces of the microparticles when the microparticles are dispersed in the base liquid may be 16.2 mV or more, thereby improving the monodispersity of the porous microparticles in the base liquid.

[0017] (4) In the coolant of the above embodiment, the concentration of the fine particles may be 30% by weight or less, which can suppress an increase in the viscosity of the coolant and prevent blockages at orifices of the flow path when the coolant flows.

[0018] (5) In the coolant of the above aspect, the central pore diameter of the plurality of pores of the spherical porous silica material contained in the microparticles may be 1 nm or more and 20 nm or less. In this way, the coolant contains microparticles in which a sufficient amount of phase change material is filled in the pores of the spherical porous silica material, thereby further improving the heat storage capacity of the microparticles and further improving the heat exchange capacity of the coolant.

[0019] (6) In the coolant of the above embodiment, the plurality of pores of the spherical porous silica of the microparticles may have a standard deviation of 20% or less of the median pore diameter in the pore diameter distribution curve in the range of pore diameters greater than 1 nm. In this way, the pore diameters of the spherical porous silica are highly uniform, so that capillary forces act more uniformly, improving the filling rate of the phase-change material and further improving the heat storage capacity of the microparticles. As a result, the heat exchange capacity of the coolant can be improved.

[0020] (7) In the coolant of the above aspect, the spherical porous silica particles contained in the microparticles may have a diameter of 10 nm or more and 3000 nm or less. This can improve the monodispersity of the microparticles in the coolant and further suppress a decrease in the heat exchange capacity of the coolant.

[0021] (8) In the cooling liquid of the above aspect, the plurality of pores of the spherical porous silica of the fine particles have a pore volume of 0.9 [ml / g] or more and a specific surface area per unit pore volume of 1.4 × 10 9 [m 2 / m 3 In this way, the proportion of the phase change material that effectively functions as a latent heat storage material can be increased, and the heat storage density can be increased, thereby further improving the heat exchange capacity of the coolant.

[0022] (9) In the cooling liquid of the above embodiment, the phase change material of the microparticles may be at least one of sugar alcohol and paraffin. Sugar alcohol has a high heat storage density, so it is possible to provide microparticles with good heat storage properties. Paraffin has a low degree of supercooling, so it is possible to suppress a decrease in heat storage efficiency. Therefore, it is possible to improve the heat exchange capacity of the cooling liquid.

[0023] (10) In the coolant of the above aspect, the shell portion of the microparticles may have a molecular size of raw material smaller than the pore diameter of the plurality of pores of the spherical porous silica. In this way, the raw material molecules of the shell portion of the microparticles are likely to crosslink inside the pores of the spherical porous silica and block the pores, thereby improving the density of the shell portion and further suppressing the elution of the phase-change material. As a result, the decrease in the heat exchange capacity of the coolant can be further suppressed.

[0024] The present invention can be realized in various forms, for example, in the form of a heat transport system using a coolant, a system including the heat transport system, a method for manufacturing a coolant, etc. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is an explanatory diagram illustrating a schematic configuration of a heat transport system according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram for explaining a coolant according to the embodiment. [Figure 3] 1 is an explanatory diagram conceptually showing a schematic configuration of a particle and heat storage in the particle. FIG. [Figure 4] FIG. 1 is an explanatory diagram conceptually showing the structure of a spherical porous silica material. [Figure 5] 1 is an explanatory diagram illustrating a concept of improving the heat dissipation ability of a coolant according to an embodiment. [Figure 6] FIG. 10 is a diagram showing the results of calculations of the coolant temperature when the concentration of particulates in the coolant is 10 wt %. [Figure 7] FIG. 10 is a diagram showing the results of calculations of the coolant temperature when the concentration of particulates in the coolant is 20 wt %. [Figure 8] FIG. 10 is a diagram showing the relationship between the concentration of fine particles in the coolant and the heat transfer improvement ratio. [Figure 9] FIG. 10 is a diagram showing the heat transfer improvement ratio at each concentration of fine particles in the coolant. [Figure 10] FIG. 2 is a process diagram showing an example of a process for producing fine particles. [Figure 11] FIG. 1 is an explanatory diagram conceptually showing a method for producing a spherical porous silica material used in Examples 1 to 3 and Comparative Examples 1 to 3. [Figure 12] 1 shows SEM images of the fine particles of Examples 1 and 2. [Figure 13] 1 is an SEM image of the fine particles of Comparative Example 1. [Figure 14] FIG. 1 is a diagram showing the specifications of each particle obtained from an SEM image. [Figure 15] FIG. 1 is a diagram showing the properties of fine particles obtained by thermal analysis. [Figure 16] FIG. 10 is a diagram showing the results of a durability test. [Figure 17] FIG. 1 shows a TGA curve of a phase change material. [Figure 18] FIG. 1 is a diagram showing a DSC curve of a phase change material. [Figure 19]1 shows SEM images of the fine particles of Examples 2 and 3. [Figure 20] FIG. 2 is a diagram showing the parameters obtained from SEM images of the fine particles of Examples 2 and 3 and Comparative Example 1. [Figure 21] FIG. 2 is a diagram showing the parameters obtained by thermal analysis of the fine particles of Examples 2 and 3 and Comparative Example 1. [Figure 22] FIG. 10 is a diagram showing the results of a durability test. [Figure 23] FIG. 1 is a diagram showing the main specifications of a shell source. [Figure 24] 1 is an SEM image of the fine particles of Example 1. [Figure 25] 1 shows SEM images of the fine particles of Comparative Examples 1 and 2. [Figure 26] 1 is an SEM image of the fine particles of Comparative Example 3. [Figure 27] FIG. 2 is a diagram showing the specifications obtained from SEM images of the fine particles of Example 1 and Comparative Examples 1 to 3. [Figure 28] FIG. 2 is a diagram showing the parameters obtained by thermal analysis of the fine particles of Example 1 and Comparative Examples 1 to 3. [Figure 29] FIG. 10 is a diagram showing the results of a durability test. [Figure 30] FIG. 10 is an explanatory diagram conceptually showing the formation of an outer shell portion. DETAILED DESCRIPTION OF THE INVENTION

[0026] <Embodiment> 1 is an explanatory diagram showing the schematic configuration of a heat transport system 1100 according to an embodiment. The heat transport system 1100 is a system that dissipates heat from a heat source using a coolant CL (a liquid heat transfer medium). The coolant CL of this embodiment contains a base liquid and monodisperse microparticles.

[0027] The heat transport system 1100 includes a first heat exchanger 110, a second heat exchanger 120, a coolant tank 130, a valve 140, and a pump 150 that pumps the coolant CL. The first heat exchanger 110, the second heat exchanger 120, the coolant tank 130, and the pump 150 are connected in a circular configuration via pipes 62, 63, 64, and 65. The pump 150 circulates the coolant CL through the first heat exchanger 110, the second heat exchanger 120, and the coolant tank 130 in that order via the pipes 62, 63, 64, and 65.

[0028] The first heat exchanger 110 dissipates heat from the heat source using the coolant CL. In this embodiment, the heat source is exemplified by a battery CE mounted on an electric vehicle.

[0029] The second heat exchanger 120 is disposed downstream of the first heat exchanger 110, and dissipates heat from the coolant CL that has passed through the first heat exchanger 110. In this embodiment, a radiator is exemplified as the second heat exchanger 120.

[0030] The coolant tank 130 contains the coolant CL therein. As described above, the coolant CL contains a base liquid and monodisperse microparticles. In Fig. 1, the microparticles contained in the coolant CL are illustrated in an enlarged manner.

[0031] A valve 140 is provided on the pipe 64, and is opened, for example, while the electric vehicle is in operation.

[0032] FIG. 2 is an explanatory diagram illustrating the coolant CL of this embodiment. The coolant CL of this embodiment contains a base liquid L and monodisperse particles P contained in the base liquid L. Here, monodispersity refers to a state in which particles are approximately uniform in size and easily dispersed without agglomeration. For example, "monodispersity" can be said to occur when the ratio (%) of the particle size distribution width to the average particle size is ±15% or less. Because the particles P are monodisperse, even if the particles P settle when the coolant CL is left stationary, when the heat transport system 1100 is driven and the coolant CL circulates through the heat receiving and dissipating section, the particles P become monodisperse in the base liquid L. In FIG. 2, the particles P are shown with diagonal hatching, and some of the particles P are assigned reference numerals, while the reference numerals for the remaining particles P are omitted.

[0033] In the coolant CL, the absolute value of the zeta potential of the surface of the particles P when the particles P are dispersed in the base liquid L is not particularly limited, but is preferably 16.2 mV or more. In this way, the monodispersity of the particles P in the base liquid L can be improved, for example, as described in Japanese Patent No. 7194129 of the present applicant. Note that, as described in Japanese Patent No. 7194129, the zeta potential of the surface of the particles P can be controlled by controlling the thickness of the outer shell 300 of the particles P. The zeta potential can be measured by dynamic light scattering (DLS).

[0034] The concentration of the particles P in the coolant CL is preferably 30 wt% or less, and more preferably 20 wt% or less. If the concentration of the particles P in the coolant CL is 30 wt% or less, an increase in the viscosity of the coolant CL can be suppressed, and blockages at the orifices of the flow path can be suppressed when the coolant CL flows.

[0035] As shown in Figures 1 and 2, when the coolant CL flows through the first heat exchanger 110, it exchanges heat with the battery CE to cool the battery CE, and when it flows through the second heat exchanger 120, it exchanges heat with the outside air to dissipate heat.

[0036] Base liquid: The base liquid L is a liquid heat transfer medium, and its composition is not particularly limited and can be selected according to the purpose. The base liquid L can be, for example, various liquids such as water or an alcohol aqueous solution. The base liquid L can be any of an aqueous coolant, a non-aqueous coolant, and an emulsion-based coolant. The aqueous coolant is a water-based coolant (so-called antifreeze: for example, a freezing point ≦−20°C) that is a mixture of water and a freezing point depressant that is mutually soluble in water. The water content is optional, but preferably 30 to 50 wt%. The freezing point depressant is preferably an alcohol-based one. From the viewpoint of reducing viscosity, alcohols such as methanol, ethanol, n-propanol, and i-propanol are preferred. From the viewpoint of low vapor pressure and performance, glycols such as ethylene glycol and propylene glycol are preferred. Other glycols such as polyalkylene glycol and glycol ether may also be used as freezing point depressants. Furthermore, a rust inhibitor may be added. This inhibits metal corrosion caused by water and also inhibits metal ion elution. From the viewpoint of insulating properties, nonionic rust inhibitors are preferred. Furthermore, from the viewpoint of copper rust prevention, triazole-based rust inhibitors are preferred, and from the viewpoint of aluminum rust prevention, silicon-based rust inhibitors are preferred. Examples of nonaqueous coolants include highly electrically insulating coolants such as oils and fluorine-based media. Highly electrically insulating coolants are suitable for cooling electrical components such as batteries, inverters, motors, ECUs, and CPUs, and their high electrical insulation also enables immersion-type high-performance cooling.

[0037] ·Fine particles: 3 is an explanatory diagram showing the schematic structure of a particle P and conceptually illustrating heat storage in the particle P. In FIG. 3, a portion of the particle P is cut away to show the internal structure. The particle P has a spherical porous silica material 100 having a plurality of pores 10, a phase change material 200 present in the pores 10, and an outer shell 300 that closes the plurality of pores 10 of the spherical porous silica material 100.

[0038] The pores 10 of the spherical porous silica material 100 are generally cylindrical. The pores 10 have uniform diameters and are arranged radially from the center of the spherical porous silica material 100 toward the surface. In the figure, some of the pores 10 and some of the phase change material 200 are labeled with reference numerals, while other portions are not labeled. FIG. 3 conceptually illustrates the microparticles P, and the number of pores may be greater or less than that illustrated. Although the figure illustrates an example in which the phase change material 200 fills the entire pores 10, the phase change material 200 may be filled only partially. Although the figure illustrates an example in which the outer shell 300 fills all of the pores 10 of the spherical porous silica material 100, it is sufficient that the outer shell 300 fills at least a portion of the pores 10.

[0039] The phase-change material 200 absorbs and releases latent heat in response to temperature changes. The particles P absorb and release heat by utilizing the phase change (solid, liquid) of the phase-change material 200. Specifically, when the phase-change material 200 held in the spherical porous silica 100 changes from solid phase-change material 200S (upper row of FIG. 3) to liquid phase-change material 200L (lower row of FIG. 3), it absorbs ambient heat near the melting point to maintain a temperature near the melting point. Conversely, when it changes from liquid phase-change material 200L (lower row of FIG. 3) to solid phase-change material 200S (upper row of FIG. 1), it releases heat to the ambient near the freezing point to maintain a temperature near the freezing point until it is completely solidified. In other words, the particles P store heat by utilizing the absorption and release of latent heat accompanying the solidification and melting of the phase-change material 200. In FIG. 3, the solid phase change material 200 is cross-hatched and designated by the reference numeral 200S, and the liquid phase change material 200 is dot-hatched and designated by the reference numeral 200L.

[0040] (1) Spherical porous silica 100 FIG. 4 is an explanatory diagram conceptually illustrating the structure of a spherical porous silica material 100. In FIG. 4, as in FIG. 3, a portion of the spherical porous silica material 100 is cut away to illustrate the shape and arrangement of the pores 10. The pores 10 are indicated by hatching in the cross section. As shown in the figure, the spherical porous silica material 100 has a plurality of approximately cylindrical pores 10, which are arranged radially from the center of the spherical porous silica material 100 toward the surface. The arrangement of the pores 10 can be confirmed by observing the fine particles P with a TEM (Transmission Electron Microscope). The arrangement of the pores can be more clearly confirmed by introducing a metal (e.g., platinum) into the pores of the fine particles P and observing them with a TEM.

[0041] The plurality of pores 10 are arranged radially from the center of the spherical porous silica 100 toward the surface, and one end of the pores 10 is not open, which further suppresses leakage of the phase-change material 200. Furthermore, since the pores 10 are approximately cylindrical in shape, the phase-change material 200 is held by capillary force, and even if the phase-change material dissolves in an organic solvent, leakage to the outside can be suppressed, and the retention stability can be maintained.

[0042] The central pore diameter of the plurality of pores 10 is not particularly limited, but is preferably 1 nm or more and 20 nm or less. More preferably, it is 2 nm or more and 10 nm or less. If the diameter of the pores 10 of the spherical porous silica material 100 is too small, it may be difficult to introduce the phase change material 200. Furthermore, since the introduction of the phase change material 200 into the pores 10 of the spherical porous silica material 100 is achieved by utilizing the capillary force of the pores 10, if the diameter of the pores 10 of the spherical porous silica material 100 is too large, the capillary force may not work effectively, and the phase change material 200 may not be sufficiently filled. If the amount of the phase change material 200 filled is insufficient, the amount of heat storage by the particles P will be small. If the central pore diameter of the pores 10 of the spherical porous silica material 100 is 1 nm or more and 20 nm or less, a sufficient amount of the phase change material 200 is filled, thereby improving the heat storage capacity of the particles P.

[0043] The pores 10 in the spherical porous silica material 100 have a uniform pore size. Here, "uniform pore size" means that the standard deviation of the pore size distribution curve in the range of pore sizes greater than 1 nm is within 35% of the median pore diameter. The median pore diameter refers to the pore diameter at which the pore size distribution curve shows a maximum peak in the range of pore sizes greater than 1 nm. The standard deviation of the pores 10 in the spherical porous silica material 100 in the range of pore sizes greater than 1 nm is preferably within 25% of the median pore diameter, more preferably within 20%. This ensures high uniformity in the pore sizes of the pores 10 in the spherical porous silica material 100, allowing capillary forces to act more uniformly, improving the filling rate of the phase-change material 200 and resulting in fine particles P with higher heat storage capacity.

[0044] The diameter of the spherical porous silica material 100 is not particularly limited, but is preferably on the order of several hundred nanometers. The diameter of the spherical porous silica material 100 is more preferably 10 nm or more and 30,000 nm or less. This can improve monodispersity when dispersing multiple microparticles P in a base liquid L. The spherical porous silica material 100 has multiple pores 10 with uniform pore diameters, and the multiple pores 10 are arranged radially from the center of the spherical porous silica material 100 toward the surface, so it can also be said to be a "spherical porous silica material with highly regular pores."

[0045] The pore volume of the plurality of pores in the spherical porous silica material 100 and the specific surface area per unit pore volume are not particularly limited, but the pore volume is preferably 0.9 ml / g or more and the specific surface area per unit pore volume is preferably 1.4×10 9 [m 2 / m 3 In this way, the proportion of the phase change material 200 that effectively functions as a latent heat storage material increases, and the fine particles P can have a high heat storage density.

[0046] The spherical porous silica material 100 can be synthesized by the method described in Japanese Patent No. 5480461. During synthesis, the diameter of the pores 10 can be adjusted by changing the type of surfactant. In addition, the pore size can be enlarged after synthesis by replacing the surfactant with another surfactant, introducing a swelling agent, or performing hydrothermal treatment under acidic conditions. The shape of the spherical porous silica material 100 (diameter, arrangement of multiple pores, pore diameter, pore volume), details of its effects, and manufacturing method are as described, for example, in Japanese Patent Application Nos. 2021-196743 and 2021-196745, which have already been filed by the applicant of the present application.

[0047] (2) Phase change material 200 In the microparticles P, a phase change material 200 is retained within the pores 10 of the spherical porous silica 100 (FIG. 3). While the phase change material 200 is not particularly limited, sugar alcohols are preferred because they have a high heat storage density and can provide a heat storage medium with good heat storage properties. Paraffin is also preferred because it has a low degree of supercooling and can suppress a decrease in heat storage efficiency. Erythritol is preferred as the sugar alcohol, and linear paraffin is preferred as the paraffin. Other examples of the phase change material 200 that can be used include sugar alcohols such as mannitol, galactitol, xylitol, sorbitol, and ribitol, inorganic salts such as inorganic phosphates, branched paraffins, and inorganic hydrates. Details of the types of phase change materials and their effects are described, for example, in Japanese Patent Application Nos. 2021-196743 and 2021-196745, previously filed by the applicant of the present application.

[0048] (3) Outer shell 300 The outer shell 300 is formed of solid silica crystals and fills at least a portion of the pores 10 of the spherical porous silica material 100. Here, "solid silica crystals" refers to so-called non-porous silica crystals that are highly dense and have substantially no pores. The fact that the outer shell 300 is solid can be confirmed by a TEM image of the fine particles P. While FIG. 3 illustrates the outer shell 300 as having a two-layer structure having a first outer shell layer 310 and a second outer shell layer 320, the outer shell may be a single layer or may have three or more layers.

[0049] The raw material for the outer shell 300 (hereinafter also referred to as the "shell source") is not particularly limited as long as it forms solid silica crystals, but it is preferable that the molecular size of the shell source be smaller than the pore diameter of the pores 10 in the spherical porous silica material 100. For example, if tetraethyl orthosilicate (hereinafter also referred to as "TEOS") is used as the raw material for the outer shell 300, its small molecular diameter makes it easy to crosslink inside the multiple pores 10 in the spherical porous silica material 100 and block the pores, thereby forming a highly dense outer shell 300. The method for producing the microparticles P will be described later.

[0050] <Estimation of coolant temperature> Fig. 5 is an explanatory diagram showing the concept of improving the heat dissipation ability of the coolant in this embodiment. Fig. 5(A) shows the conditions for calculating the outlet temperature of the coolant in the radiator serving as the second heat exchanger 120, and Fig. 5(B) conceptually shows the results of the calculation. In Fig. 5(B), the coolant in this embodiment is shown by a solid line, and the coolant in a comparative example is shown by a dashed line.

[0051] Here, the coolant temperature was calculated under the following conditions: [Coolant of the embodiment] Base liquid: 50 wt% ethylene glycol aqueous solution Heat storage density of microparticles: 70 J / g (filling rate: 37 vol%) Phase change material (heat storage material): normal paraffin (Rubitherm, RT90HC) [Comparative Example Coolant] 50wt% ethylene glycol aqueous solution [Radiator] Air side heat dissipation area: 20.353m 2 Cooling water side heat radiation area: 3.347m 2 Wind speed: 4m / s Standard heat dissipation capacity: 68.7kW (when using the comparative example coolant) Radiator size (mm): 873 (height), 334 (width), 48 (depth) In this specification, weight % concentration is also referred to as wt%, and volume % concentration is also referred to as vol%.

[0052] As shown in FIG. 5(B), when the coolant is introduced into the radiator, heat exchange occurs between the coolant and the air as it flows through the radiator, causing the coolant to release heat and lower its temperature. When the coolant of this embodiment is used, the phase-change material undergoes a phase change from liquid to solid (solidifies) for a while after being introduced into the radiator, continuing to release heat, maintaining the temperature near the melting point of the phase-change material. Therefore, as shown in the figure, the temperature of the coolant does not drop within a certain distance from the coolant inlet of the radiator. Therefore, the temperature difference between the coolant of this embodiment and the air is large, and the heat dissipation capacity can be improved compared to the coolant of the comparative example.

[0053] FIG. 6 is a diagram showing the results of calculations of the coolant temperature when the concentration of particulates in the coolant is 10 wt%. The calculation results shown in FIG. 6 were calculated using a 1D simulation in Excel under the above calculation conditions, with the concentration of particulates in the coolant set to 10 wt%. As shown in the figure, the coolant temperature at the radiator outlet of the coolant of this embodiment is lower than that of the coolant of the comparative example. In other words, the heat exchange capacity of the coolant of this embodiment is improved compared to the coolant of the comparative example.

[0054] FIG. 7 is a diagram showing the results of calculations of the coolant temperature when the concentration of particulates in the coolant is 20 wt %. The calculation results shown in FIG. 7 were also calculated using the same calculation method as above. As shown in the figure, the coolant temperature of the coolant of this embodiment is lower at the radiator outlet than the coolant of the comparative example. The coolant of this example can lower the coolant temperature at the radiator outlet more than the example shown in FIG. 6. In other words, by increasing the concentration of particulates in the coolant, the heat exchange capacity of the coolant can be improved.

[0055] Fig. 8 is a diagram showing the relationship between the concentration of particulate matter in the coolant and the heat transfer improvement ratio. Here, the concentration of particulate matter in the coolant shown in the above calculation conditions was changed, and the heat dissipation output Q [kW] was calculated using the following (Equation 1). The ratio of the heat transfer amount to the case where no particulate matter is contained (i.e., particulate matter concentration 0 wt%) (the above comparative example) is shown as the heat transfer improvement ratio. In other words, the heat transfer improvement ratio when no particulate matter is contained (particulate matter concentration 0 wt%) is set to 1. Q = ρCpF(T1-T2) (Equation 1) where ρ: density [kg / m 3 ], Cp: specific heat [kJ / kgK], F: Volumetric flow rate [m 3 / s], T1: Radiator inlet temperature [℃], T2: Radiator outlet temperature [℃]

[0056] Figure 9 is a diagram showing the heat transfer improvement ratio for each concentration of particulate matter in the coolant. Figure 9 shows the same calculation results as those shown in Figure 8. The coolants with the particulate matter concentrations shown in Figures 8 and 9 have the same pressure loss as a coolant that does not contain particulate matter (comparative example).

[0057] 8 and 9, in the coolant (containing particulates) of this embodiment, the heat transfer improvement ratio can be improved as the particulate concentration is increased. Furthermore, when the particulate concentration in the coolant of this embodiment is in the range of at least 30 wt%, the pressure loss is equivalent to that of a coolant (comparative example) that does not contain particulates, and the heat exchange capacity of the coolant can be improved while suppressing a decrease in pressure loss.

[0058] Even if the coolant temperature and heat transfer conditions (composition of the base liquid, heat storage density of the microparticles, type of phase-change material) differ from those set in the calculations of the coolant temperature and heat transfer, the coolant of the embodiment will exhibit the same trends as those shown in FIGS. 5 to 9 . For example, even if water, a glycol solution, or the like is used as the base liquid, the coolant can contain microparticles as a heat storage material, thereby slowing the temperature rise and fall of the coolant compared to when only the base liquid is used as the coolant (comparative example). This results in a larger temperature difference between the coolant and the heating element, low-temperature external air, etc., compared to the comparative example, improving the heat exchange capacity. Furthermore, for the same reason, even if the heat storage density of the microparticles or the type of phase-change material is different, the heat exchange capacity can be improved compared to when only the base liquid is used as the coolant.

[0059] <Details of the particles> The production method and performance of the fine particles P as a heat storage material contained in the coolant CL of this embodiment will be described below with examples. [Manufacturing method] FIG. 10 is a process diagram showing an example of a manufacturing process for the fine particles P according to the embodiment. First, spherical porous silica into which a phase-change material has been introduced and a shell source liquid are prepared (step P102). For example, a 100% TEOS liquid is prepared as the shell source liquid. Next, the prepared spherical porous silica is added to the shell source liquid, and the mixture is stirred and maintained at a predetermined temperature for a predetermined time (step P104). For example, the mixture is maintained at room temperature for 24 hours. Step P104 forms a first outer shell layer 310 on the surface of the spherical porous silica 100 (FIG. 1).

[0060] The liquid 1 produced in step P104 is filtered, and the particles on which the first outer shell layer 310 has been formed are taken out and dried to obtain the particles 1 (step P106). For example, the particles are dried at 45° C. for 24 hours.

[0061] Next, the particles 1 are immersed in an aqueous solution and hydrated to obtain liquid 2 (step P108). For example, the particles 1 are immersed in an ethylene glycol (EG) aqueous solution and left at room temperature for 24 hours. The ethylene glycol aqueous solution has, for example, an ethylene glycol:water ratio of 1:1 by weight. The hydration treatment can increase the proportion of silanol groups on the surface of the particles 1.

[0062] The liquid 2 produced in step P108 is filtered, and the particles are taken out and dried to obtain particles 2 (step P110). For example, the particles are dried at 45° C. for 24 hours. Note that step P108 (hydration treatment) and step P110 do not necessarily have to be performed.

[0063] The particles 2 obtained in step P110 are added to a shell source liquid and maintained at a predetermined temperature for a predetermined time while stirring (step P112). As in step P104, a 100% TEOS liquid is used as the shell source liquid, and the liquid is maintained at room temperature for 24 hours. In step P112, a second outer shell layer 320 is formed on the first outer shell layer 310 (FIG. 1). Steps P104 and P112 are also referred to as the "outer shell layer formation step."

[0064] The liquid 3 produced in step P112 is filtered, and the particles on which the first outer shell layer 310 and the second outer shell layer 320 have been formed are taken out and dried to obtain particles 3 (step P106). For example, the particles are dried at 45°C for 24 hours. The particles 3 correspond to the fine particles P of the embodiment.

[0065] The spherical porous silica material doped with a phase-change material prepared in step P102 may be prepared in advance or may be prepared in step P102. The spherical porous silica material doped with a phase-change material can be synthesized by mixing a predetermined amount of spherical porous silica material 100 with a predetermined amount of liquid phase-change material 200L that has been melted by heating above its melting point. The liquid phase-change material 200L is introduced into and retained in the pores 10 of the spherical porous silica material 100 by capillary force. Furthermore, the pore diameter of the spherical porous silica material 100 into which the phase-change material is doped can be enlarged, for example, by subjecting the base spherical porous silica material to a treatment.

[0066] 10 is an example, and some steps may be omitted. Other examples of the manufacturing method will be described in the following examples of the particles. [Example of fine particles]

[0067] The microparticles contained in the coolant of this embodiment will be described in more detail using Examples 1 to 3 and Comparative Examples 1 to 3, but the microparticles contained in the coolant of the present invention are not limited to the following Examples. All of the Examples and Comparative Examples are microparticles in which the same type of phase change material is filled into the pores of spherical porous silica of approximately the same shape (particle diameter, pore diameter, pore volume, etc.). The Examples and Comparative Examples differ in the presence or absence of an outer shell, the number of layers of the outer shell, the thickness of the outer shell, and the raw material (shell source) of the outer shell. In Examples 1 to 3 and Comparative Examples 1 to 3, normal paraffin (RT90HC, Rubitherm) was used as the phase change material.

[0068] <Sample manufacturing method> Fig. 11 is an explanatory diagram conceptually showing a method for producing a spherical porous silica material 100 used in Examples 1 to 3 and Comparative Examples 1 to 3. Like Fig. 1, Fig. 11 shows the internal structure of a spherical porous silica material with a portion cut away.

[0069] The spherical porous silica used in Examples 1 to 3 and Comparative Examples 1 to 3 was obtained by enlarging the pore diameter of a base spherical porous silica 100A (hereinafter also referred to as a base spherical porous silica) by treating it with reference to JP-A Nos. 2011-111332 and 2007-45701.

[0070] The base spherical porous silica 100A (top panel of Figure 11) was synthesized by the same method as described in Japanese Patent No. 5,480,461, except that the surfactant used was changed from hexadecyltrimethylammonium chloride (C16Cl) to octadecyltrimethylammonium chloride (C18Cl). The surfactant 12A remaining in the pores 10A of the spherical porous silica 100A is C18Cl. The central pore diameter of the pores in the spherical porous silica 100A is 2.0 nm.

[0071] 2.26 g of swelling agent 14 (trimethylbenzene, TMB), 30 cc of ethanol, and 30 cc of pure water were mixed / dispersed in 1.0 g of spherical porous silica 100A, and the mixture was kept at 100°C for three days. Swelling agent 14 penetrated the hydrophobic parts of surfactant 12A, resulting in spherical porous silica 100B with an expanded pore size of 5.5 nm. The synthesized spherical porous silica 100B was calcined at 550°C for 8 hours to remove surfactant 12A and swelling agent 14, yielding spherical porous silica 100.

[0072] A predetermined amount of liquid phase change material (linear paraffin) that had been melted by heating above its melting point was mixed with a predetermined amount of spherical porous silica 100, thereby introducing the phase change material into the pores 10 of the spherical porous silica 100.

[0073] First, the method for producing fine particles according to the second embodiment will be described with reference to FIG. Spherical porous silica containing normal paraffin as a phase-change material and a liquid shell source (100% TEOS) were prepared (step P102), and the prepared spherical porous silica was added to the liquid shell source and kept at room temperature for 24 hours while stirring (step P104). This resulted in the formation of a first outer shell layer on the surface of the spherical porous silica (Figure 1).

[0074] The liquid 1 produced in step P104 was filtered, and the particles on which the first outer shell layer had been formed were taken out and dried at 45° C. for 24 hours to obtain particles 1 (step P106).

[0075] Next, particle 1 was immersed in an ethylene glycol (EG) aqueous solution and left at room temperature for 24 hours (hydration treatment), to obtain liquid 2 (step P108). The ethylene glycol aqueous solution had an ethylene glycol:water ratio of 1:1 by weight. Liquid 2 produced in step P108 was filtered to remove the particles, which were then dried at 45°C for 24 hours to obtain particle 2 (step P110). Particle 2 had an increased proportion of silanol groups on the surface of the first outer shell layer.

[0076] The particles 2 obtained in step P110 were added to a liquid of the shell source (TEOS 100%) and kept at room temperature for 24 hours while stirring (step P112). This resulted in the formation of a second shell layer on the first shell layer (Figure 1). The liquid 3 produced in step P112 was filtered, and the particles with the first and second shell layers formed were taken out and dried at 45°C for 24 hours to obtain the microparticles of Example 2 (step P106).

[0077] The microparticles of Example 3 were obtained by sequentially performing all of the steps of the microparticle production process of Example 1 except for steps P108 and P110. That is, like the microparticles of Example 2, the microparticles of Example 3 also have a shell portion with a two-layer structure (first outer shell layer and second outer shell layer).

[0078] The microparticles of Example 1 and Comparative Examples 2 and 3 were obtained by sequentially performing steps P102, P104, and P106 in the microparticle production process shown in FIG. 10. That is, the microparticles of Example 1 and Comparative Examples 2 and 3 are microparticles in which one layer of outer shell is formed on the surface of a spherical porous silica body. That is, these microparticles have only a first outer shell layer as the outer shell. Example 1 and Comparative Examples 2 and 3 differ from each other in the raw materials (shell sources) of the outer shell, which are 100% TEOS, TEOS / ethanol, and perhydropolysilazane (hereinafter also referred to as PHPS), respectively. The microparticles of Comparative Example 1 are microparticles without an outer shell.

[0079] <Comparison of outer shell thickness> The difference in durability of the microparticles due to differences in the thickness of the outer shell will be explained using the above-mentioned Examples 1 and 2 and Comparative Example 1. Here, durability is evaluated based on the change in the packing rate of the phase change material and the change in the ratio of the effective heat storage material when immersed in an organic solvent.

[0080] FIG. 12 is a scanning electron microscope (SEM) image of the microparticles of Examples 1 and 2. FIG. 13 is an SEM image of the microparticles of Comparative Example 1. FIG. 14 is a diagram showing the specifications of each microparticle obtained from the SEM image. FIG. 14 shows the average particle diameter and shell thickness of the microparticles. The average particle diameter was determined by measuring the diameters of 200 microparticles using the SEM image and taking the arithmetic mean. Assuming that the outer shells of the microparticles of Examples 1 and 2 have a uniform thickness, the thickness of the outer shell was calculated using the average particle diameter of each microparticle as follows. Since Comparative Example 1 is a spherical porous silica material without an outer shell, the average particle diameter of Comparative Example 1 was subtracted from the average particle diameter of Examples 1 and 2, and the result divided by 2 was used as the shell thickness of each of Examples 1 and 2.

[0081] 14, the microparticles of Example 1 have a shell thickness of 0.55 μm. The microparticles of Example 2 have a shell thickness of 0.11 μm, which is thicker than the microparticles of Example 1. The microparticles of Comparative Example 1 do not have a shell.

[0082] Figure 15 shows the characteristics of the microparticles obtained by thermal analysis. Figure 15 shows the changes in the phase-change material packing ratio, heat storage density, and effective heat storage ratio before and after immersion in an organic solvent as a durability evaluation of the microparticles. The phase-change material present in the pores of spherical porous silica is divided into effective heat storage materials and ineffective heat storage materials. Effective heat storage materials generate latent heat through melting and solidification (described in detail later). Therefore, since a large amount of effective heat storage materials is desirable for the microparticles, the durability test focuses on the change in the effective heat storage ratio. For the durability test, 0.1 g of microparticles was added to 10 ml of toluene (liquid) as an organic solvent and kept at 60°C for 3 hours while stirring. The particles were then filtered and dried at 45°C for 24 hours for evaluation.

[0083] FIG. 16 shows the results of the durability test. As shown in FIGS. 15 and 16, in the microparticles of Comparative Example 1, almost no effective heat storage material remained after immersion in toluene. In contrast, in the microparticles of Example 1, although the effective heat storage material decreased after immersion in toluene, more than half remained. Furthermore, in the heat storage material of Example 2, the filling rate of the effective heat storage material did not change even after immersion. In other words, it can be said that the formation of an outer shell in the microparticles suppressed the elution of the effective heat storage material. Furthermore, by thickening the outer shell, the elution of the effective heat storage material could be further suppressed. In the microparticles of Example 2, as described above, the outer shell layer formation step was performed twice (FIG. 3: steps P104 and P112), which is thought to have improved the density of the outer shell. The microparticles of Examples 1 and 2 were able to suppress the elution of the effective heat storage material when immersed in an organic solvent.

[0084] The filling ratio represents the proportion of the total pore volume occupied by the introduced phase change material (hereinafter also referred to as "PCM"), and can be estimated by simultaneous thermogravimetry and differential thermal analysis (TG-DTA). In this example, the measurements were performed using a simultaneous thermogravimetry and differential thermal analysis instrument, Thermoplus TG-8120 (manufactured by RIGAKU).

[0085] 17 is a diagram showing a TGA (Thermogravimetric analysis) curve of the phase-change material. The weight loss at 150 to 700°C was taken as the organic fraction derived from the PCM, and the filling rate of the PCM in the pores was calculated. Specifically, this was calculated using the following (Equation 1).

[0086] Filling rate [vol%] = organic fraction / PCM density / pore volume × 100 … (Equation 1)

[0087] The PCM density of the PCM held in the porous silica material in the microparticles can be measured, for example, by the following method: the microparticles are heated to evaporate the PCM gas, and the PCM density can be calculated using mass information obtained by analyzing the gas by gas chromatography-mass spectrometry (GC / MS).

[0088] In the examples and comparative examples, spherical porous silica materials of approximately the same shape were used, and the pore volume was 1.30 to 1.80 [ml / g]. The pore volume [ml / g] was estimated from the measured nitrogen adsorption isotherm using a BET (Brunauer, Emmett, and Teller) plot.

[0089] Figure 18 shows DSC curves of phase change materials. Figure 18(a) shows a typical differential scanning calorimetry (DSC) curve for erythritol, and Figure 18(b) shows a typical DSC curve for normal paraffin. As shown in the figure, the difference between the endothermic peak and the exothermic peak represents the degree of supercooling. Also, as shown in the figure, the peak area of ​​the endothermic curve (shown hatched in the figure) corresponds to the amount of heat storage.

[0090] The effective heat storage material ratio represents the ratio of PCM that can generate latent heat by melting / solidifying out of the total PCM occupying the pores, and can be estimated by differential scanning calorimetry (DSC) (latent heat storage density [J / g]). In this example, differential scanning calorimetry was performed using a DSC Q1000 differential scanning calorimeter (manufactured by TA Instruments) at a temperature range of -20°C to 150°C and a heating / cooling rate of 10°C / min. Meanwhile, the ineffective heat storage material is the total PCM minus the effective heat storage material.

[0091] The effective heat storage material can be calculated using the following (Equation 2) and (Equation 3). Effective heat storage material [vol%] = apparent latent heat / PCM latent heat × 100 … (Equation 2) Apparent latent heat = heat storage amount / PCM density / pore volume ... (Equation 3)

[0092] <Effects of hydration treatment> Here, the effect of carrying out the hydration treatment (FIG. 10: step P108) in the method for producing fine particles having a two-layered shell structure will be described with reference to FIGS.

[0093] Fig. 19 is an SEM image of the microparticles of Examples 2 and 3. Fig. 20 is a diagram showing the parameters obtained from the SEM images of the microparticles of Examples 2 and 3 and Comparative Example 1. Fig. 20 shows the average particle diameter and shell thickness of the microparticles, as in Fig. 14, and the average particle diameter and shell thickness were calculated in the same manner as in Fig. 14.

[0094] As described above, the microparticles of Example 2 were produced by carrying out all the steps shown in Fig. 10 and were subjected to a hydration treatment. The microparticles of Example 3 were produced by carrying out all the steps of the microparticle production process of Example 2 in order except for steps P108 and P110, and were not subjected to a hydration treatment.

[0095] As shown in FIG. 20, the thickness of the outer shell of the microparticles in Example 2 was 0.11 μm, and the thickness of the outer shell of the microparticles in Example 3 was 0.08 μm. The thickness of the outer shell could be increased by performing a hydration treatment. In the method for producing microparticles, if a hydration treatment is performed after the formation of the first outer shell layer, the proportion of silanol groups on the surface of the first outer shell layer increases, making it easier to form the second outer shell layer and increasing the thickness of the outer shell. Note that the thickness of the outer shell of the microparticles in Example 3 is thicker than the outer shell thickness of the microparticles in Example 1 (0.055 μm in FIG. 14), and it can be said that the second outer shell layer is formed. In other words, although the second outer shell layer can be formed without performing a hydration treatment, the thickness of the outer shell can be increased by performing a hydration treatment.

[0096] 21 is a diagram showing the specifications obtained by thermal analysis of the fine particles of Examples 2 and 3 and Comparative Example 1. FIG. 21 shows the results of the same durability evaluation (immersion in toluene) as in FIG.

[0097] FIG. 22 shows the results of the durability test. As shown in FIGS. 21 and 22, in the microparticles of Comparative Example 1, almost no effective heat storage material remained after immersion in toluene. In contrast, in the microparticles of Example 3, although the effective heat storage material decreased after immersion in toluene, more than half remained. Furthermore, in the microparticles of Example 2, the filling rate of the effective heat storage material did not change even after immersion in toluene. That is, in the method for producing microparticles having a multi-layered outer shell, by performing a hydration treatment between the formation of the outer shell layers, the thickness of the outer shell can be increased, and the elution of the heat storage material after immersion in an organic solvent can be further suppressed. Furthermore, the microparticles of Example 3 have a two-layered outer shell with a thickness of 0.08 μm, which is thicker than the microparticles of Example 1 (FIG. 14: single-layered outer shell, thickness 0.055 μm), but the proportion of effective heat storage material after immersion in an organic solvent is the same as that of the microparticles of Example 1. From these results, it is considered that the denseness of the outer shell of the microparticles of Example 3 was low. That is, in the method for producing microparticles having a shell with a multi-layer structure, the density of the shell can be improved by carrying out a hydration treatment.

[0098] <Comparison of shell sources> Here, TEOS and PHPS are used as the raw materials (shell source) for the outer shell portion, and the difference in durability of the fine particles due to the difference in shell source will be described with reference to FIGS. FIG. 23 shows the main specifications of the shell source. As shown in the figure, in the microparticles of Examples 1 to 3, a 100% TEOS liquid was used as the shell source. In the microparticles of Comparative Example 2, ethanol was used as the solvent, and a TEOS solution with a 1:1 weight ratio of TEOS to ethanol was used as the shell source. In the microparticles of Comparative Example 3, a PHPS solution was used as the shell source. Here, Durazane 2200 (manufactured by Merck) and Durazane 2800 (manufactured by Merck) were mixed in a weight ratio of 1:1 as the PHPS. The solvent for Durazane 2200 and Durazane 2800 was dibutyl ether (hereinafter also referred to as DBE). The PHPS concentration of Durazane 2200 was 20%, and the PHPS concentration of Durazane 2800 was 15%. Durazane 2200 does not contain a catalyst and has a slow curing speed, while Durazane 2800 contains an amine-based catalyst and has a very fast curing speed. 23 also lists xylene as a solvent for PHPS. In other examples, other PHPS such as Durazane 2600 (manufactured by Merck) may be used as the PHPS. Durazane 2600 uses xylene as a solvent, has a PHPS concentration of 15%, contains an amine-based catalyst, and has a fast curing speed.

[0099] Fig. 24 is an SEM image of the microparticles of Example 1. Fig. 25 is an SEM image of the microparticles of Comparative Examples 1 and 2. Fig. 26 is an SEM image of the microparticles of Comparative Example 3. Fig. 27 is a diagram showing specifications obtained from the SEM images of the microparticles of Example 1 and Comparative Examples 1 to 3. Fig. 27 shows the average particle diameter and shell thickness of the microparticles, as in Fig. 14, and the average particle diameter and shell thickness are calculated in the same manner as in Fig. 14.

[0100] As described above, Example 1 and Comparative Examples 2 and 3 were produced by sequentially performing steps P102 to P106 of the production process shown in Fig. 10, and the outer shells had a single-layer structure. As shown in Fig. 27, the shell source of the outer shells of the microparticles of Example 1 was 100% TEOS, the shell source of the outer shells of the microparticles of Comparative Example 2 was TEOS / ethanol (weight ratio 1:1), and the shell source of the outer shells of the microparticles of Comparative Example 3 was PHPS. The microparticles of Comparative Examples 2 and 3 had thinner shells than the microparticles of Example 1.

[0101] 28 is a diagram showing the specifications obtained by thermal analysis of the fine particles of Example 1 and Comparative Examples 1 to 3. Fig. 28 shows the results of the same durability evaluation (immersion in toluene) as in Fig. 15.

[0102] Fig. 29 shows the results of the durability test. As shown in Figs. 28 and 29, in the microparticles of Comparative Example 1 (without an outer shell), almost no effective heat storage material remains after immersion in toluene (after the durability test). In the microparticles of Comparative Example 2, even before immersion in toluene, the filling rate of the effective heat storage material is about half that of Comparative Example 1, indicating a low filling rate of the effective heat storage material. Since the shell source of the microparticles of Comparative Example 2 contains ethanol, it is thought that the proportion of effective heat storage material decreases due to the interaction between ethanol and the phase change material when the outer shell is formed. Furthermore, in the microparticles of Comparative Example 2, almost no effective heat storage material remains after immersion in toluene, similar to the microparticles of Comparative Example 1.

[0103] Although the microparticles of Comparative Example 3 had a lower phase-change material loading rate than the microparticles of Comparative Example 1 (without a shell) before toluene immersion, the loading rate of the effective heat storage material was not as low as that of the microparticles of Comparative Example 2. Therefore, it is believed that there was almost no effect of the interaction between the phase-change material and PHPS / DBE during shell formation. Although the microparticles of Comparative Example 3 still had more effective heat storage material remaining after toluene immersion than the microparticles of Comparative Examples 1 and 2, the loading rate of the effective heat storage material was lower than that of Example 1. It is believed that the effective heat storage material was eluted and partially inactivated by toluene immersion. In other words, when 100% TEOS is used as the shell source, the density of the outer shell can be improved compared to when PHPS is used as the shell source, and the elution of the effective heat storage material can be more effectively suppressed. When the outer shell is incompletely dense (has many defects), the organic solvent penetrates into the pores of the spherical porous silica and dissolves the phase-change material, which then flows out.

[0104] FIG. 30 is an explanatory diagram conceptually illustrating the formation of the outer shell portion. FIG. 30(a) shows an example in which the shell source is TEOS, and FIG. 30(b) shows an example in which the shell source is PHPS. In FIG. 30, the shell source TEOS is denoted by the symbol 300t, and the shell source PHPS is denoted by the symbol 300p. The pore diameters of the pores 10 in the spherical porous silica materials 100 shown in FIG. 30(a) and FIG. 30(b) are the same. TEOS has a small molecular diameter, so it can crosslink within the pores 10 and block the pores, as shown in the figure. PHPS has a large molecular diameter, so it can crosslink the upper part of the pores 10 and block the pores. As shown in FIG. 30(a), if the shell source TEOS can crosslink within the pores and block the pores, the crosslinking distance is shortened, forming a highly dense outer shell portion. This reduces the penetration of organic solvents and further suppresses the elution of the phase-change material. Therefore, it is preferable that the molecular diameter of the shell source of the outer shell portion is smaller than the pore diameter of the spherical porous silica. On the other hand, if the shell source PHPS, whose molecular diameter is equal to or larger than the pore diameter of the spherical porous silica, bridges the upper part of the pore 10 and blocks the pore, as shown in Figure 30(b), the crosslinking distance will be longer and the density will be lower. Furthermore, if elemental analysis of the outer shell portion of the microparticle is performed and, for example, nitrogen atoms (N) remain in the outer shell, it can be inferred that the shell source is PHPS, and the molecular diameter can be estimated.

[0105] As described above, the microparticles of the examples have an outer shell formed of solid silica crystals, compared to the microparticles of Comparative Example 1, and therefore can suppress the dissolution of the effective heat storage material when immersed in an organic solvent, thereby improving the durability of the microparticles.

[0106] Furthermore, the microparticles of the examples had a shell thickness of 0.55 μm or more, which was sufficient to further suppress the elution of the effective heat storage material, compared with the microparticles of comparative examples 2 and 3. The pores had high regularity and the central pore diameter was 1 nm or more and 20 nm or less, so a sufficient heat storage density and heat storage capacity could be obtained.

[0107] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0108] In the above embodiment, the heat transport system 1100 dissipates heat from the battery CE mounted on the electric vehicle, but other heat sources such as fuel cells, inverters, motor generators, etc. may also be used. Also, the coolant can be used to cool various objects such as air conditioning equipment and plants.

[0109] In the above embodiment, a radiator is used as the second heat exchanger 120, but a chiller on the low-pressure side of the refrigeration cycle may also be used. That is, the second heat exchanger 120 can dissipate heat using a refrigerant or air.

[0110] The present invention has been described above based on embodiments and examples, but the above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit and scope of the claims, and the present invention includes equivalents thereof. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0111] The present invention can also be realized as the following application examples. [Application example 1] A cooling liquid comprising a base liquid and monodisperse microparticles contained in the base liquid, The microparticles are a spherical porous silica body having a plurality of substantially cylindrical pores formed therein; a phase-change material contained in the plurality of pores of the spherical porous silica material; an outer shell portion formed of solid silica crystals and closing at least a part of the plurality of pores of the spherical porous silica material; In the spherical porous silica material, the plurality of pores have a uniform pore diameter and are arranged radially from the center of the spherical porous silica material toward the surface thereof; coolant. [Application example 2] The cooling liquid according to Application Example 1, The thickness of the outer shell of the fine particles is 0.055 μm or more. coolant. [Application example 3] The cooling liquid according to Application Example 1, the absolute value of the zeta potential of the surface of the microparticles when the microparticles are dispersed in the base liquid is 16.2 mV or more; coolant. [Application example 4] The cooling liquid according to Application Example 1, The concentration of the fine particles is 30% by weight or less. coolant. [Application example 5] The cooling liquid according to Application Example 1, the central pore diameter of the plurality of pores of the spherical porous silica material contained in the fine particles is 1 nm or more and 20 nm or less; coolant. [Application Example 6] The cooling liquid according to Application Example 1, The plurality of pores of the spherical porous silica material of the fine particles are The standard deviation of the pore size distribution curve in the range of pore sizes greater than 1 nm is within 20% of the central pore diameter. coolant. [Application Example 7] The cooling liquid according to Application Example 1, the diameter of the spherical porous silica particles contained in the fine particles is 10 nm or more and 3000 nm or less; coolant. [Application Example 8] The cooling liquid according to Application Example 1, The plurality of pores of the spherical porous silica material of the fine particles are The pore volume is 0.9 [ml / g] or more, and the specific surface area per unit pore volume is 1.4 × 10 9 [m 2 / m 3 ] is less than or equal to coolant. [Application Example 9] The cooling liquid according to Application Example 1, the phase change material contained in the fine particles is at least one of sugar alcohol and paraffin; coolant. [Application Example 10] The coolant according to any one of Application Examples 1 to 9, the shell portion of the fine particles has a molecular size of a raw material smaller than the pore diameters of the plurality of pores of the spherical porous silica material; coolant. [Explanation of symbols]

[0112] 10...pore 12A...Surfactant 14...Swelling agent 62...Plumbing 100, 100A, 100B...Spherical porous silica 110...1st heat exchanger 120…Second heat exchanger 130...Coolant tank 140...valve 150...Pump 200, 200L, 200S...phase change materials 300...Outer shell 310...First outer layer 320...Second outer shell layer 1100...Heat transport system CE…Battery CL…Cooling liquid L: Base liquid P…fine particles

Claims

1. A cooling liquid comprising a base liquid and monodisperse microparticles contained in the base liquid, The microparticles are a spherical porous silica body having a plurality of substantially cylindrical pores formed therein; a phase-change material contained in the plurality of pores of the spherical porous silica material; an outer shell portion formed of solid silica crystals and closing at least a part of the plurality of pores of the spherical porous silica material; In the spherical porous silica material, the plurality of pores have a uniform pore diameter and are arranged radially from the center of the spherical porous silica material toward the surface thereof; coolant.

2. 2. The coolant of claim 1, The thickness of the outer shell of the fine particles is 0.055 μm or more. coolant.

3. 2. The coolant of claim 1, the absolute value of the zeta potential of the surface of the microparticles when the microparticles are dispersed in the base liquid is 16.2 mV or more; coolant.

4. 2. The coolant of claim 1, The concentration of the fine particles is 30% by weight or less. coolant.

5. 2. The coolant of claim 1, the central pore diameter of the plurality of pores of the spherical porous silica material contained in the fine particles is 1 nm or more and 20 nm or less; coolant.

6. 2. The coolant of claim 1, The plurality of pores of the spherical porous silica material of the fine particles are The standard deviation of the pore size distribution curve in the range of pore sizes greater than 1 nm is within 20% of the central pore diameter; coolant.

7. 2. The coolant of claim 1, the diameter of the spherical porous silica particles contained in the fine particles is 10 nm or more and 3000 nm or less; coolant.

8. 2. The coolant of claim 1, The plurality of pores of the spherical porous silica material of the fine particles are The pore volume is 0.9 [ml / g] or more, and the specific surface area per unit pore volume is 1.4 × 10 9 [m 2 / m 3 ]or less, coolant.

9. 2. The coolant of claim 1, the phase change material contained in the fine particles is at least one of sugar alcohol and paraffin; coolant.

10. 10. The coolant according to any one of claims 1 to 9, the shell portion of the fine particles has a molecular size of a raw material smaller than the pore diameters of the plurality of pores of the spherical porous silica material; coolant.

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