Coolant and heat pump refrigerant

Abstract

To provide a coolant and a heat pump refrigerant that can efficiently cool a device without occupying a large space.SOLUTION: A coolant includes a temperature sensitive gel including a temperature sensitive polymer having hydrophilicity at a temperature lower than a lower critical solution temperature and hydrophobicity at a temperature higher than the lower critical solution temperature, and a polar solvent that wets the temperature sensitive polymer, the temperature sensitive gel undergoing a volume phase transition accompanied by an endothermic reaction in a case where a temperature rise exceeding the lower critical solution temperature occurs.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to refrigerants and refrigerants for heat pumps. [Background technology]

[0002] Cooling methods for electronic devices are broadly classified into air-cooling, water-cooling, and phase-change cooling.

[0003] In air-cooling electronic devices, an air current is generated by a fan. Heat is transferred from a heat source inside the electronic device to the air carried by the air current. This removes heat from the heat source, and the heat source is cooled.

[0004] In liquid cooling of electronic devices, a pump is used to generate a circulating liquid flow, and heat is transferred from a heat source inside the electronic device to the liquid that is circulated by the liquid flow, thereby removing heat from the heat source and cooling the heat source.

[0005] In cooling electronic devices using phase change cooling, heat is transferred from the heat source inside the electronic device to a liquid, causing the liquid to change into a gas. This removes the latent heat required to change the liquid into a gas from the heat source, cooling the heat source. The gas that has changed from liquid is cooled at a location away from the heat source and changes back into liquid. The liquid that has changed from gas returns to the area around the heat source. Cooling electronic devices using phase change cooling has attracted attention as a pumpless technology that does not require a pump.

[0006] Patent Document 1 discloses a cooling device. In this cooling device, a refrigerant liquid evaporates by absorbing heat generated by a heat generating element immersed in the refrigerant liquid as latent heat, turns into refrigerant vapor, and retains heat in the form of heat of vaporization. The refrigerant vapor releases the heat of vaporization to the outside through the housing wall or through the housing wall and a heat dissipation member. The refrigerant vapor that has released the heat of vaporization condenses and becomes refrigerant liquid again. The condensed refrigerant liquid returns to the pooled refrigerant liquid by running along the housing wall or directly dropping. This allows the refrigerant to change phase to cool the heat generating element (paragraphs 0012, 0015, and 0024). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2019-140247 A Summary of the Invention [Problem to be solved by the invention]

[0008] Cooling electronic devices using air cooling requires additional equipment such as a fan. Cooling electronic devices using liquid cooling requires additional equipment such as a pump. Cooling electronic devices using phase change cooling requires a space to change gas into liquid at a position away from the heat source and return the liquid to the area around the heat source. For example, the cooling device disclosed in Patent Document 1 requires a space to condense refrigerant vapor above a heat generating element to change it into refrigerant liquid, and to allow the refrigerant vapor to fall and return it to the area around the heat generating element.

[0009] Therefore, in cooling electronic devices using air cooling, water cooling, and phase change cooling, the cooling elements occupy a large space. This problem also occurs in cooling devices other than electronic devices.

[0010] In view of this problem, an aspect of the present disclosure is to provide a coolant and a refrigerant for a heat pump that can efficiently cool equipment without occupying a large space. [Means for solving the problem]

[0011] The cooling material of the first aspect of the present disclosure comprises a thermosensitive polymer that is hydrophilic at temperatures lower than a lower critical solution temperature and hydrophobic at temperatures higher than the lower critical solution temperature, and a polar solvent that wets the thermosensitive polymer, and is provided with a thermosensitive gel that undergoes a volume phase transition accompanied by an endothermic reaction when a temperature rise occurs above the lower critical solution temperature.

[0012] A refrigerant for a heat pump according to a second aspect of the present disclosure includes the cooling material according to the first aspect of the present disclosure and a liquid refrigerant into which the cooling material is mixed. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a diagram illustrating a schematic diagram of the microstructure of the coolant of the first embodiment at a temperature lower than the lower critical solution temperature (LCST). [Diagram 2] FIG. 2 is a diagram illustrating a schematic diagram of the microstructure of the coolant of the first embodiment at a temperature higher than the lower critical solution temperature. [Diagram 3] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 4] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Diagram 5] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 6] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 7] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 8] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 9] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 10] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 11] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 12] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 13] FIG. 2 is a perspective view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 14] FIG. 2 is a plan view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 15]FIG. 2 is a plan view illustrating a schematic example of a shape of a coolant in the first embodiment. [Figure 16] 1 is a perspective view illustrating a coolant and a circuit board cooled by the coolant according to a first embodiment; [Figure 17] FIG. 2 is a perspective view illustrating a coolant and a condenser cooled by the coolant in the first embodiment. [Figure 18] FIG. 2 is an exploded perspective view illustrating a coolant and a condenser cooled by the coolant according to the first embodiment. [Figure 19] 1 is a perspective view illustrating a coolant and a cylindrical heating element cooled by the coolant according to a first embodiment; [Figure 20] 10 is a cross-sectional view illustrating a schematic diagram of a coolant and a heat generating element cooled by the coolant according to a second embodiment. FIG. [Figure 21] FIG. 11 is a diagram illustrating a schematic diagram of a temperature change in a state of a coolant in the second embodiment. [Figure 22] 13 is a cross-sectional view illustrating a schematic diagram of a coolant and a heat generating element cooled by the coolant in a first modified example of the second embodiment. FIG. [Diagram 23] FIG. 11 is a cross-sectional view illustrating a coolant according to a third embodiment. [Figure 24] FIG. 13 is a diagram illustrating a schematic diagram of a temperature change in a state of a coolant in the fourth embodiment. [Diagram 25] FIG. 2 is a schematic diagram illustrating a state in which a first released polar solvent is trapped between a first thermosensitive gel and a second thermosensitive gel. [Figure 26] FIG. 13 is a diagram illustrating a schematic diagram of a temperature change in a state of a coolant in a first modified example of the fourth embodiment. [Figure 27] FIG. 11 is a diagram illustrating a schematic diagram of a temperature change in a state of a coolant in a reference example. [Figure 28] FIG. 11 is a cross-sectional view that illustrates a heat pump including a heat pump refrigerant according to a fifth embodiment. [Figure 29] FIG. 13 is a diagram illustrating a schematic diagram of a temperature change in a state of a coolant provided in a heat pump refrigerant of the fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or equivalent elements are denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0015] 1. First embodiment 1.1 Microstructure of the coolant Fig. 1 is a diagram showing a schematic diagram of the microstructure of the coolant of the first embodiment at a temperature lower than the lower critical solution temperature (LCST). Fig. 2 is a diagram showing a schematic diagram of the microstructure of the coolant of the first embodiment at a temperature higher than the LCST.

[0016] The coolant 1 of the first embodiment shown in Figs. 1 and 2 comes into contact with the surface of a heat generating body and absorbs heat from the surface with which it comes into contact, thereby lowering the temperature of the surface or suppressing an increase in the surface temperature.

[0017] As shown in FIGS. 1 and 2, the cooling material 1 comprises a temperature-sensitive gel 11 .

[0018] The thermosensitive gel 11 is a solid having gel-like properties. Therefore, the cooling material 1 made of the thermosensitive gel 11 can be attached to the surface of a heat generating body. The cooling material 1 can be attached even to a surface that faces in the horizontal direction, on which it is difficult to stably attach a cooling material made of a solid that does not have gel-like properties. The thermosensitive gel 11 attached to the surface comes into contact with the surface to which it is attached, and is thermally bonded to the heat generating body.

[0019] As shown in FIGS. 1 and 2, the thermosensitive gel 11 includes a thermosensitive polymer 21 and a polar solvent 22 .

[0020] When the temperature of the thermosensitive gel 11 rises above the LCST, the state of the thermosensitive polymer 21 changes from a predominantly hydrophilic state in which the hydrophilic portions contained in the thermosensitive polymer 21 are more prevalent than the hydrophobic portions contained in the thermosensitive polymer 21 to a predominantly hydrophobic state in which the hydrophobic portions contained in the thermosensitive polymer 21 are more prevalent than the hydrophilic portions contained in the thermosensitive polymer 21. As a result, the thermosensitive polymer 21 changes from hydrophilic to hydrophobic.

[0021] Therefore, when the temperature rises above the LCST, the thermosensitive gel 11 undergoes hydrophobic hydration accompanied by an endothermic reaction, and the hydrophobic hydration triggers a volume phase transition accompanied by an endothermic reaction. Therefore, when the temperature rises above the LCST, the thermosensitive gel 11 absorbs the heat required to cause a volume phase transition, i.e., the reaction heat of the endothermic reaction accompanying the volume phase transition, from the surface of the heat generating body.

[0022] Furthermore, when a temperature rise exceeding the LCST occurs, the fluidity of the polar solvent 22 that has penetrated into the network formed by the thermosensitive polymer 21 increases due to hydrophobic hydration. Furthermore, a chain of micro-condensations of the thermosensitive polymer 21 causes macro-condensation of the thermosensitive polymer 21. As a result, a part of the polar solvent 22, which is a component other than the thermosensitive polymer 21 that forms the network, is pushed out from the network. Therefore, when a temperature rise exceeding the LCST occurs, the thermosensitive gel 11 contracts and releases a part of the polar solvent 22 that has moistened the thermosensitive gel 11 (hereinafter, also referred to as "released polar solvent") 31. As a result, the thermosensitive gel 11 absorbs the heat required to release the released polar solvent 31 from the surface of the heating element.

[0023] The released polar solvent 31 includes polar solvent released in liquid form and polar solvent released in gas form. The reason why the released polar solvent 31 includes polar solvent released in gas form is that the released polar solvent 31 is released with an increase in temperature, and the released polar solvent 31 is heated when it is released. Since the released polar solvent 31 includes polar solvent released in gas form, the thermosensitive gel 11 absorbs the latent heat required to evaporate all or part of the released polar solvent 31 from the surface of the heating element. All or part of the polar solvent released in liquid may evaporate. When all or part of the polar solvent released in liquid evaporates, the latent heat required to evaporate all or part of the polar solvent released in liquid can be absorbed from the surface of the heating element.

[0024] The thermosensitive gel 11 absorbs not only the reaction heat of the endothermic reaction accompanying the volume phase transition, but also the heat required to release the released polar solvent 31 and the latent heat required to evaporate all or part of the released polar solvent 31 from the surface of the heating element. In this way, the thermosensitive gel 11 absorbs multiple types of heat with different properties from the surface of the heating element, thereby effectively lowering the surface temperature or effectively suppressing an increase in the surface temperature. As a result, the thermosensitive gel 11 can efficiently cool the heating element without requiring a fan, pump, etc., and without occupying a large space.

[0025] A part of the released polar solvent 31 may be released from the surface of the thermosensitive gel 11 that is in contact with the heating element. However, most of the released polar solvent 31 is released from the opposite surface of the thermosensitive gel 11 that is opposite to the surface that is in contact with the heating element. This is because the heat absorbed by the thermosensitive gel 11 from the heating element is transferred from the surface that is in contact with the heating element to the opposite surface, so that the position of the thermosensitive gel 11 that changes from hydrophilic to hydrophobic also moves from the surface that is in contact with the heating element to the opposite surface, and the released polar solvent 31 is also squeezed out from the surface that is in contact with the heating element to the opposite surface.

[0026] The thermosensitive gel 11 has a larger heat capacity than metal. Therefore, when the thermosensitive gel 11 absorbs heat in an insulated closed space, the temperature of the thermosensitive gel 11 rises more slowly than when the metal absorbs heat in an insulated closed space. Therefore, when the temperature of a heating element continues to rise in an insulated closed space, the thermosensitive gel 11 can cool the heating element more effectively than metal.

[0027] 1.2 Temperature-sensitive polymers The thermosensitive polymer 21 is a stimuli-responsive polymer that is temperature responsive. The thermosensitive polymer 21 is hydrophilic at temperatures lower than the LCST and is hydrophobic at temperatures higher than the LCST. The LCST is lower than the temperature that the heating element reaches when it generates heat without being cooled by the coolant 1. Therefore, when the heating element generates heat, the temperature rises beyond the LCST.

[0028] The thermosensitive polymer 21 forms a network. The network may be formed by fixing molecular chains by crosslinking or bonding, or by entangling molecular chains. The network includes a thermosensitive component. The thermosensitive component is a molecule or a unit.

[0029] The thermosensitive polymer 21 is, for example, (1) at least one polymer selected from the group consisting of cellulose derivatives, poly(N-alkyl(meth)acrylamide), derivatives of poly(N-alkyl(meth)acrylamide), poly(N-vinyl alkylamide), derivatives of poly(N-vinyl alkylamide), poly(N-vinyl pyrrolidone), derivatives of poly(N-vinyl pyrrolidone), poly(2-alkyl-2-oxazoline), derivatives of poly(2-alkyl-2-oxazoline), polyvinyl ether, derivatives of polyvinyl ether, polyvinyl alkyl ether, derivatives of polyvinyl alkyl ether, copolymers of polyethylene oxide and polypropylene oxide, derivatives of copolymers of polyethylene oxide and polypropylene oxide, poly(oxyethylene vinyl ether) and derivatives of poly(oxyethylene vinyl ether); (2) a copolymer of at least two polymers selected from the above group; and (3) A crosslinked product of at least one polymer selected from the group consisting of the at least one polymer and a copolymer of the at least two polymers. The composition includes at least one selected from the group consisting of:

[0030] The cellulose derivative includes, for example, at least one selected from the group consisting of methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, and hydroxypropyl methyl cellulose.

[0031] The poly(N-alkyl(meth)acrylamide) includes, for example, at least one selected from the group consisting of poly(N-isopropyl(meth)acrylamide), poly(N-normal propyl(meth)acrylamide), poly(N-methyl(meth)acrylamide), poly(N-ethyl(meth)acrylamide), poly(N-normal butyl(meth)acrylamide), poly(N-isobutyl(meth)acrylamide) and poly(Nt-butyl(meth)acrylamide).

[0032] The poly(N-vinyl alkylamide) includes, for example, at least one selected from the group consisting of poly(N-vinyl isopropylamide), poly(N-vinyl normal propylamide), poly(N-vinyl normal butylamide), poly(N-vinyl isobutylamide) and poly(N-vinyl-t-butylamide).

[0033] The poly(2-alkyl-2-oxazoline) includes, for example, at least one selected from the group consisting of poly(2-ethyl-2-oxazoline), poly(2-isopropyl-2-oxazoline) and poly(2-normal propyl-2-oxazoline).

[0034] The polyvinyl alkyl ether includes, for example, at least one selected from the group consisting of polyvinyl methyl ether and polyvinyl ethyl ether.

[0035] Here, "(meth)acrylic" means "acrylic" or "methacrylic".

[0036] The LCST of the thermosensitive polymer 21 varies depending on the type of the thermosensitive polymer 21. For example, when the thermosensitive polymer 21 is poly(N-isopropylacrylamide) (PNIPAM), the LCST of the thermosensitive polymer 21 is 32°C. When the thermosensitive polymer 21 is hydroxypropyl cellulose (HPC), the LCST of the thermosensitive polymer 21 is 45°C to 46°C. When the thermosensitive polymer 21 is poly(N-cyclopropylacrylamide) (PNCPAM), the LCST of the thermosensitive polymer 21 is 49°C. When the thermosensitive polymer 21 is poly(2-ethyl-2-oxazoline) (PEtOx), the LCST of the thermosensitive polymer 21 is 62°C to 65°C.

[0037] The thermosensitive polymer 21 has a molecular structure having a hydrophobic group and a hydrophilic group, and has amphiphilicity. The LCST of the thermosensitive polymer 21 can be changed by substituting either or both of the hydrophobic group and the hydrophilic group.

[0038] The LCST of the thermosensitive polymer 21 is affected by the actual use environment, such as pH, ion amount, etc. For this reason, the thermosensitive polymer 21 is designed in consideration of the actual use environment.

[0039] 1.3 Polar Solvents The polar solvent 22 penetrates into the network formed by the thermosensitive polymer 21 and wets the thermosensitive polymer 21 .

[0040] The polar solvent 22 includes, for example, at least one selected from the group consisting of water and flame-retardant polar solvents. The flame-retardant polar solvent includes, for example, an ionic liquid. The ionic liquid includes, for example, an imidazolium salt. The imidazolium salt includes, for example, at least one selected from the group consisting of an imidazolium salt represented by chemical formula (1) and an imidazolium salt represented by chemical formula (2). In chemical formula (1), R 1 ,R 2 and R 3 is an alkyl group having 1 to 12 carbon atoms, and X is a halogen. In the chemical formula (2), R 1 is an alkyl group having 1 to 6 carbon atoms, and R 2 is a group represented by the chemical formula (3), and X is Cl, Br, BF 4 ,BPh 4 ,PF 6 ,NO 3 ,[(CF 3 SO 2 ) 2 N] or [(CN) 2 In the chemical formula (3), A is a direct bond, a phenylene group, or a group represented by the chemical formula (4).

[0041] [ka]

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] 1.4 Hydrophilic polymers The thermosensitive gel 11 may contain a hydrophilic polymer. When the thermosensitive gel 11 contains a hydrophilic polymer, the affinity of the thermosensitive gel 11 with a polar solvent can be increased.

[0046] The hydrophilic polymer is, for example, (1) at least one polymer selected from the group consisting of polyethylene glycol (PEG), 2-methacryloyloxyethyl phosphorylcholine (MPC), poly(meth)acrylic acid, poly(meth)acrylates, alginic acid, alginates, hyaluronic acid, hyaluronates, chitosan, and cellulose derivatives; (2) a copolymer of at least two polymers selected from the above group; and (3) A crosslinked product of at least one polymer selected from the group consisting of the at least one polymer and a copolymer of the at least two polymers. The composition includes at least one selected from the group consisting of:

[0047] The cellulose derivative includes, for example, at least one selected from the group consisting of carboxymethyl cellulose, methyl cellulose, ethyl cellulose, and hydroxyethyl cellulose.

[0048] Here, "(meth)acrylic" means "acrylic" or "methacrylic".

[0049] When the thermosensitive gel 11 contains a hydrophilic polymer, the volume phase transition can be made gentle by randomly copolymerizing the thermosensitive polymer 21 and the hydrophilic polymer. Also, by imparting an interpenetrating polymer network (IPN) structure to the thermosensitive polymer 21 and the hydrophilic polymer, the LCST of the thermosensitive polymer 21 can be generally maintained.

[0050] 1.5 Preparation of thermosensitive gel When producing a thermosensitive gel 11, for example, a solution containing a pre-crosslinked precursor of a thermosensitive polymer 21 and a polar solvent 22 is prepared, and the prepared solution is subjected to a gelling process such as a process for crosslinking the pre-crosslinked precursor.

[0051] 1.6 Coolant Shape Figures 3 to 13 are perspective views that diagrammatically illustrate examples of shapes of the coolant of the first embodiment. Figures 14 and 15 are plan views that diagrammatically illustrate examples of shapes of the coolant of the first embodiment.

[0052] The coolant 1 may have any shape. The coolant 1 is given a shape suitable for the application of the coolant 1.

[0053] For example, the coolant 1 may have a disk-like shape as shown in FIG. 3, a rectangular plate-like shape as shown in FIG. 4, or the like. The coolant 1 may have a flat plate-like shape other than the disk-like shape and the rectangular plate-like shape. When the coolant 1 has a flat plate-like shape, the surface area of ​​the coolant 1 that comes into contact with the heat generating body can be increased. Therefore, when the coolant 1 has a flat plate-like shape, a heat generating body having a surface with a large area can be efficiently cooled. Therefore, when it is desired to cool a wide area in an open space, the coolant 1 is desirably given a flat plate-like shape.

[0054] Alternatively, the cooling material 1 may have a plate-like or cloth-like outer shape with a plurality of holes formed therein, as shown in Fig. 5. When the cooling material 1 has such a shape, it can cool a wide area even when the amount of the thermosensitive gel 11 provided in the cooling material 1 is small.

[0055] Alternatively, the coolant 1 may have a thread-like or string-like shape as shown in FIG. 6. When the coolant 1 has a thread-like or string-like shape, the coolant 1 can be brought into contact with the heat generating body by wrapping the coolant 1 around the surface of the heat generating body, filling the inside of the heat generating body with the coolant 1, or the like. When the coolant 1 has a thread-like or string-like shape, the entire coolant 1 is connected, so that the entire coolant 1 can be drawn by drawing one end of the coolant 1. Therefore, when the coolant 1 has a thread-like or string-like shape, the coolant 1 can be easily replaced when it deteriorates.

[0056] Alternatively, the cooling material 1 may have a mesh-like shape as shown in FIG. 7. When the cooling material 1 has a mesh-like shape, it can also efficiently cool a heat generating body having a surface with a large area. When the cooling material 1 has a mesh-like shape, it may be a cloth-like fabric made of multiple woven threads. When the threads have a core-sheath structure described below, the cooling material 1 has the same effect as the core-sheath structure described below. The multiple threads may be one type of thread, or two or more types of threads. Two or more types of threads may have different LCSTs. When two or more types of threads have different LCSTs, the cooling material 1 undergoes a volume phase transition accompanied by an endothermic reaction and shrinks when a temperature rise occurs that exceeds each of the two or more different LCSTs. For this reason, the cooling rate is slowed down, but the cooling capacity can be maintained for a long time. The cooling material 1 may be a laminate of multiple cooling materials having a mesh-like shape. When the cooling material 1 is the laminate, the cooling rate can be increased.

[0057] Alternatively, the coolant 1 may have a spherical shape as illustrated in FIG.

[0058] Alternatively, the coolant 1 may have a conical shape, such as that shown in Fig. 9. The coolant 1 may have a pyramidal shape other than a conical shape.

[0059] Alternatively, the coolant 1 may have a round bar shape as shown in Fig. 10, a square bar shape as shown in Fig. 11, or the like. The coolant 1 may have a bar shape other than the round bar shape and the square bar shape.

[0060] Alternatively, the coolant 1 may have a coiled shape as shown in Fig. 12. When the coolant 1 has a coiled shape, the coolant 1 can be formed by winding a coolant having a filamentary shape.

[0061] Alternatively, the coolant 1 may have a folding screen shape as shown in FIG.

[0062] Alternatively, the coolant 1 may have a granular shape as shown in FIG. 14 or a pulverized shape as shown in FIG. 15. When the coolant 1 has a pulverized shape, the coolant 1 can be formed by pulverizing a flat-shaped coolant to obtain a solid. When the coolant 1 has a pulverized shape, the coolant 1 has an irregular shape, for example, a block shape, a flake shape, or the like. When the coolant 1 has a granular or pulverized shape, the coolant 1 can be brought into contact with the heat generating element by filling the inside of the heat generating element with the coolant 1, or the like. For this reason, when it is desired to cool a narrow range in a closed space such as the inside of a tube or an electronic component, the coolant 1 is desirably given a granular or pulverized shape.

[0063] When the coolant 1 cools a heat-generating body in a closed space, it is preferable to install a fan that generates an airflow that hits the coolant 1 and the heat-generating body. This allows the coolant 1 to efficiently cool the heat-generating body. When the coolant 1 cools a heat-generating body in an open space, the coolant 1 can efficiently cool the heat-generating body.

[0064] 1.7 Examples of coolant use FIG. 16 is a perspective view that typically illustrates the coolant and a circuit board cooled by the coolant of the first embodiment.

[0065] 16 is a heating element having a flat plate shape. Therefore, the circuit board 41 has a first main surface 41a and a second main surface 41b. The first main surface 41a and the second main surface 41b are on opposite sides to each other.

[0066] 16 has a flat plate shape and is attached to the second main surface 41b of the circuit board 41. In this way, the coolant 1 comes into contact with the second main surface 41b and cools the circuit board 41. Instead of the coolant 1 attached to the second main surface 41b, or in addition to the coolant 1 attached to the second main surface 41b, a coolant attached to the first main surface 41a may be provided.

[0067] Fig. 17 is a perspective view that typically illustrates the coolant and a condenser cooled by the coolant of the first embodiment. Fig. 18 is an exploded perspective view that typically illustrates the coolant and a condenser cooled by the coolant of the first embodiment.

[0068] 17 and 18 is a heating element having a cylindrical shape, and therefore has an outer peripheral surface 42a and a top surface 42b.

[0069] The coolant 1 shown in Figs. 17 and 18 includes a first portion 51 and a second portion 52. The first portion 51 has a sheet-like shape, is flexible, and is wrapped around the outer peripheral surface 42a of the condenser 42 and attached to the outer peripheral surface 42a. As a result, the first portion 51 comes into contact with the outer peripheral surface 42a and cools the condenser 42. The second portion 52 has a sheet-like shape, and is attached to the top surface 42b of the condenser 42. As a result, the second portion 52 comes into contact with the top surface 42b and cools the condenser 42.

[0070] 17 and 18 show a state in which the coolant 1 is in contact with the entire outer peripheral surface 42a and the top surface 42b of the condenser 42 to cool the condenser 42. However, the coolant 1 may be in contact with only a portion of the outer peripheral surface 42a and the top surface 42b of the condenser 42 to cool the condenser 42.

[0071] The coolant 1 may cool electronic components other than the capacitor 42 having a cylindrical shape.

[0072] FIG. 19 is a perspective view that typically illustrates the coolant and the cylindrical heating element cooled by the coolant of the first embodiment.

[0073] 19 has a cylindrical shape. Therefore, inside the cylindrical heating element 43, an intra-cylinder space 43s is formed.

[0074] The coolant 1 shown in FIG. 19 has a thread-like shape. The coolant 1 is filled in the cylindrical space 43s of the cylindrical heating element 43. When the coolant 1 has a thread-like shape, when it becomes necessary to replace the coolant 1 with a new coolant, the entire coolant 1 can be easily taken out of the cylindrical space 43s by pulling one end of the coolant 1. Therefore, the coolant 1 can be easily replaced with a new coolant. When the coolant 1 is filled in the cylindrical space 43s, the coolant 1 may have a granular or pulverized shape. The coolant 1 may be filled in a space formed in a heating element other than the cylindrical heating element 43 or an object that contacts the heating element. For example, the coolant 1 may be filled in a hole formed in a box-shaped heating element, a shallow rectangular heating element, a housing of a container that contacts the heating element, or the like.

[0075] When the thermosensitive gel 11 is attached to the heating element, the thermosensitive gel 11 is fixed to the heating element by a fixing member such as an adhesive, tape, screw, wire, etc. When the thermosensitive gel 11 is fixed to the heating element by a fixing member such as an adhesive or tape arranged between the thermosensitive gel 11 and the heating element, the fixing member is preferably dotted on the surface of the thermosensitive gel 11 facing the heating element. This makes it possible to suppress the cooling being hindered by the fixing member compared to when the fixing member is arranged on the entire facing surface. Alternatively, when the thermosensitive gel 11 is attached to the heating element, the thermosensitive gel 11 is fixed to the heating element by a chemical bond such as silane coupling.

[0076] The coolant 1 is used at a temperature lower than the combustion temperature of the thermosensitive polymer 21. For example, when the thermosensitive polymer 21 is a cellulose derivative having a combustion temperature of 200°C or higher, the coolant 1 is used at approximately 150°C or lower.

[0077] 2. Second embodiment The following describes the differences between the second embodiment and the first embodiment. For points that are not described, the second embodiment employs the same configuration as that employed in the first embodiment.

[0078] FIG. 20 is a cross-sectional view that typically illustrates a coolant and a heat generating element cooled by the coolant according to the second embodiment.

[0079] The cooling material 2 of the second embodiment shown in FIG.

[0080] The impermeable layer 12 covers the thermosensitive gel 11. The impermeable layer 12 covers the entire surface of the thermosensitive gel 11 and contacts the entire surface of the thermosensitive gel 11. The impermeable layer 12 is hydrophobic or waterproof. Therefore, the impermeable layer 12 does not allow the polar solvent 22 to pass through. As a result, the thermosensitive gel 11 is contained in a space surrounded by the impermeable layer 12. In addition, it is possible to prevent the released polar solvent 31 released by the thermosensitive gel 11 from leaking from within the space to the outside of the space. The released polar solvent 31 is confined within the space and is retained between the thermosensitive gel 11 and the impermeable layer 12. The retained released polar solvent 31 is absorbed by the thermosensitive gel 11 when a temperature drop exceeding the LCST occurs. This allows the coolant 2 to be used repeatedly for cooling.

[0081] The impermeable layer 12 is made of, for example, at least one selected from the group consisting of polyvinylidene chloride, silicone gel, polyethylene, and polyurethane.

[0082] When the impermeable layer 12 has adhesiveness, the adhesiveness of the impermeable layer 12 can be utilized to attach the coolant 2 to the heating element 61, thereby making it possible to attach the coolant 2 to the heating element 61. Therefore, when the impermeable layer 12 has adhesiveness, a fixing member such as an adhesive for fixing the coolant 2 to the heating element 61 is not necessary.

[0083] FIG. 21 is a diagram illustrating a schematic diagram of a temperature change in the state of the coolant in the second embodiment.

[0084] 21 , when the temperature T1 of the heating element 61 is lower than the LCST (Ta) of the thermosensitive gel 11, the thermosensitive gel 11 retains the polar solvent 22 without releasing it, and has a volume Va. Therefore, no polar solvent 22 exists between the thermosensitive gel 11 and the impermeable layer 12.

[0085] When the temperature T1 of the heating element 61 becomes higher than the LCST (Ta) of the thermosensitive gel 11, the thermosensitive polymer 21 contained in the thermosensitive gel 11 changes from hydrophilic to hydrophobic. As a result, the thermosensitive gel 11 contracts and has a volume Va' smaller than the volume Va. At that time, the thermosensitive gel 11 releases the released polar solvent 31. The released polar solvent 31 accumulates between the thermosensitive gel 11 and the impermeable layer 12 and has a volume w.

[0086] When the temperature T1 of the heating element 61 becomes lower than the LCST (Ta) of the thermosensitive gel 11 again, the thermosensitive gel 11 swells and regains the volume Va. At that time, the thermosensitive gel 11 absorbs the accumulated released polar solvent 31. Therefore, the released polar solvent 31 is no longer present between the thermosensitive gel 11 and the impermeable layer 12.

[0087] FIG. 22 is a cross-sectional view that typically illustrates a coolant and a heat generating element cooled by the coolant in a first modified example of the second embodiment.

[0088] In the first modified example of the second embodiment, as shown in FIG. 22, the impermeable layer 12 covers the thermosensitive gel 11. The impermeable layer 12 covers a part of the surface of the thermosensitive gel 11 and contacts a part of the surface of the thermosensitive gel 11. The heating element 61 covers the remaining part of the surface of the thermosensitive gel 11 and contacts the remaining part of the surface of the thermosensitive gel 11. This allows the thermosensitive gel 11 to be accommodated in a space surrounded by the impermeable layer 12 and the heating element 61. In addition, it is possible to prevent the released polar solvent 31 released by the thermosensitive gel 11 from leaking out of the space from within the space. The released polar solvent 31 is confined in the space and is held between the thermosensitive gel 11 and the impermeable layer 12 or between the thermosensitive gel 11 and the heating element 61. The held released polar solvent 31 is absorbed by the thermosensitive gel 11 when a temperature drop exceeding the LCST occurs. This allows the coolant 2 to be repeatedly used for cooling.

[0089] 3. Third embodiment The following describes the differences between the third embodiment and the first embodiment. For points that are not described, the third embodiment employs the same configuration as that employed in the first embodiment.

[0090] FIG. 23 is a cross-sectional view that typically illustrates a coolant according to the third embodiment.

[0091] The coolant 3 of the third embodiment shown in FIG. 23 has a filamentary shape.

[0092] As shown in FIG. 23, the cooling material 3 comprises a first temperature-sensitive gel 71, a second temperature-sensitive gel 72 and an impermeable layer 12.

[0093] The first thermosensitive gel 71 includes a first thermosensitive polymer and a first polar solvent, similar to the thermosensitive gel 11 provided in the cooling material 1 of the first embodiment. The first thermosensitive polymer is hydrophilic at a temperature lower than the first LCST and is hydrophobic at a temperature higher than the first LCST. The first polar solvent moistens the first thermosensitive polymer. When a temperature rise exceeding the first LCST occurs, the first thermosensitive gel 71 undergoes a first volume phase transition accompanied by an endothermic reaction. When a temperature rise exceeding the first LCST occurs, the first thermosensitive gel 71 contracts and releases a part of the first polar solvent (hereinafter also referred to as "first released polar solvent").

[0094] The second thermosensitive gel 72 includes a second thermosensitive polymer and a second polar solvent, similar to the thermosensitive gel 11 provided in the cooling material 1 of the first embodiment. The second thermosensitive polymer is hydrophilic at a temperature lower than the second LCST and is hydrophobic at a temperature higher than the second LCST. The second polar solvent wets the second thermosensitive polymer. When the temperature rises beyond the second LCST, the second thermosensitive gel 72 undergoes a second volume phase transition accompanied by an endothermic reaction. When the temperature rises beyond the second LCST, the second thermosensitive gel 72 contracts and releases a part of the second polar solvent (hereinafter also referred to as "second released polar solvent").

[0095] The first LCST of the first thermosensitive gel 71 and the second LCST of the second thermosensitive gel 72 are different from each other. Making the first LCST and the second LCST different from each other may be achieved by making the first thermosensitive polymer and the second thermosensitive polymer provided in the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, different types of polymers from each other, or not. Therefore, the first thermosensitive polymer and the second thermosensitive polymer may be polymers obtained by crosslinking the same type of polymer with the same type of crosslinking agent, or not.

[0096] The first temperature-sensitive gel 71 and the second temperature-sensitive gel 72 are in contact with each other.

[0097] The cooling material 3 has a core-sheath structure. The first thermosensitive gel 71 constitutes the core. The second thermosensitive gel 72 constitutes the sheath that covers the core. Therefore, the first thermosensitive gel 71 has a thread-like shape. The second thermosensitive gel 72 covers the outer peripheral surface of the first thermosensitive gel 71 and is in contact with the outer peripheral surface of the first thermosensitive gel 71.

[0098] The impermeable layer 12 covers the sheath. Therefore, the impermeable layer 12 covers the outer peripheral surface of the second thermosensitive gel 72 and contacts the outer peripheral surface of the second thermosensitive gel 72. The impermeable layer 12 is hydrophobic or waterproof. Therefore, the impermeable layer 12 does not allow the first polar solvent and the second polar solvent provided in the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, to pass through. As a result, the first thermosensitive gel 71 and the second thermosensitive gel 72 are contained in a space surrounded by the impermeable layer 12. In addition, the first released polar solvent and the second released polar solvent released by the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, can be prevented from leaking from within the space to the outside of the space. This allows the coolant 3 to be used repeatedly for cooling.

[0099] The impermeable layer 12 is made of, for example, at least one selected from the group consisting of polyvinylidene chloride, silicone gel, polyethylene, and polyurethane.

[0100] The second LCST of the second thermosensitive gel 72 is lower than the first LCST of the first thermosensitive gel 71. The second LCST can be made lower than the first LCST by imparting strong hydrophilicity to the first thermosensitive polymer of the first thermosensitive gel 71 to increase the first LCST, and imparting weak hydrophilicity to the second thermosensitive polymer of the second thermosensitive gel 72 to decrease the second LCST. The first LCST can be adjusted by adjusting the LCST of the first thermosensitive gel 71 itself by selecting the first thermosensitive gel 71, adjusting the ion concentration, adjusting the pH, etc. The second LCST can also be adjusted by adjusting the LCST of the second thermosensitive gel 72 itself by selecting the second thermosensitive gel 72, adjusting the ion concentration, adjusting the pH, etc.

[0101] When the temperature rise exceeds the second LCST (Tb) of the second thermosensitive gel 72, the second thermosensitive polymer included in the second thermosensitive gel 72 changes from hydrophilic to hydrophobic. The change from hydrophilic to hydrophobic of the second thermosensitive polymer occurs before the change from hydrophilic to hydrophobic of the first thermosensitive polymer included in the first thermosensitive gel 71. As a result, the second thermosensitive gel 72 becomes a wall that does not allow the first released polar solvent released by the first thermosensitive gel 71 to pass through. This makes it possible to suppress the first released polar solvent from leaking out of the coolant 3. When the second thermosensitive polymer changes from hydrophilic to hydrophobic, the second thermosensitive gel 72 releases a second released polar solvent. The second released polar solvent includes a polar solvent released from the inner peripheral surface of the second thermosensitive gel 72 and a polar solvent released from the outer peripheral surface of the second thermosensitive gel 72. The former polar solvent is absorbed into the first thermosensitive gel 71. Therefore, when the second thermosensitive gel 72 changes from hydrophilic to hydrophobic, the first thermosensitive gel 71 swells. The latter polar solvent accumulates between the outer peripheral surface of the second thermosensitive gel 72 and the inner peripheral surface of the impermeable layer 12.

[0102] When the temperature of the first thermosensitive gel 71 rises above the first LCST after the temperature of the second thermosensitive gel 72 rises above the second LCST, the first thermosensitive polymer contained in the first thermosensitive gel 71 changes from hydrophilic to hydrophobic. When the first thermosensitive polymer changes from hydrophilic to hydrophobic, the first thermosensitive gel 71 releases a first released polar solvent. The released first released polar solvent is released from the outer peripheral surface of the first thermosensitive gel 71. The released first released polar solvent accumulates between the outer peripheral surface of the first thermosensitive gel 71 and the inner peripheral surface of the second thermosensitive gel 72.

[0103] As a result, the coolant 3 not only absorbs heat from the heat generating body in accordance with the heat capacity of the coolant 3, but also absorbs heat required for the endothermic reactions accompanying the first volume phase transition and the second volume phase transition caused by the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, from the surface of the heat generating body, and absorbs heat required for the first thermosensitive gel 71 and the second thermosensitive gel 72 to release the first releasing polar solvent and the second releasing polar solvent, respectively, from the surface of the heat generating body.

[0104] The first released polar solvent and the second released polar solvent released by the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, do not permeate the impermeable layer 12. Therefore, the first released polar solvent and the second released polar solvent remain inside the coolant 3 and do not leak out to the outside of the coolant 3. The first released polar solvent and the second released polar solvent remaining inside the coolant 3 are absorbed by the second thermosensitive gel 72 when a temperature drop occurs that exceeds the second LCST of the second thermosensitive gel 72, and are absorbed by the first thermosensitive gel 71 when a temperature drop occurs that exceeds the first LCST of the first thermosensitive gel 71. This prevents the coolant 3 from losing the first polar solvent and the second polar solvent provided in the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively. This allows the coolant 3 to be used repeatedly.

[0105] The impermeable layer 12 may be omitted. In the case where the impermeable layer 12 is omitted, the second released polar solvent released from the outer peripheral surface of the second thermosensitive gel 72 contains the polar solvent released as a gas. This allows the coolant 3 to absorb the heat required to evaporate the polar solvent released as a gas from the surface of the heating element.

[0106] 4 Fourth embodiment The following describes the differences between the fourth embodiment and the first embodiment. For points that are not described, the fourth embodiment employs the same configuration as that employed in the first embodiment.

[0107] FIG. 24 is a diagram illustrating a schematic diagram of a temperature change in the state of the coolant in the fourth embodiment.

[0108] The cooling material 4 of the fourth embodiment shown in FIG. 24 comprises a first thermosensitive gel 71, a second thermosensitive gel 72 and an impermeable layer 12.

[0109] The first thermosensitive gel 71 includes a first thermosensitive polymer and a first polar solvent, similar to the thermosensitive gel 11 provided in the cooling material 1 of the first embodiment. The first thermosensitive polymer is hydrophilic at a temperature lower than the first LCST and is hydrophobic at a temperature higher than the first LCST. The first polar solvent moistens the first thermosensitive polymer. When a temperature rise exceeding the first LCST occurs, the first thermosensitive gel 71 undergoes a first volume phase transition accompanied by an endothermic reaction. When a temperature rise exceeding the first LCST occurs, the first thermosensitive gel 71 contracts and releases a part of the first polar solvent (hereinafter also referred to as "first released polar solvent").

[0110] The second thermosensitive gel 72 includes a second thermosensitive polymer and a second polar solvent, similar to the thermosensitive gel 11 provided in the cooling material 1 of the first embodiment. The second thermosensitive polymer is hydrophilic at a temperature lower than the second LCST and is hydrophobic at a temperature higher than the second LCST. The second polar solvent wets the second thermosensitive polymer. When the temperature rises beyond the second LCST, the second thermosensitive gel 72 undergoes a second volume phase transition accompanied by an endothermic reaction. When the temperature rises beyond the second LCST, the second thermosensitive gel 72 contracts and releases a part of the second polar solvent (hereinafter also referred to as "second released polar solvent").

[0111] The first LCST of the first thermosensitive gel 71 and the second LCST of the second thermosensitive gel 72 are different from each other. Making the first LCST and the second LCST different from each other may be achieved by making the first thermosensitive polymer and the second thermosensitive polymer provided in the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, different types of polymers from each other, or not. Therefore, the first thermosensitive polymer and the second thermosensitive polymer may be polymers obtained by crosslinking the same type of polymer with the same type of crosslinking agent, or not.

[0112] The first temperature-sensitive gel 71 and the second temperature-sensitive gel 72 are in contact with each other.

[0113] The second thermosensitive gel 72 envelops the first thermosensitive gel 71. The second thermosensitive gel 72 covers the entire surface of the first thermosensitive gel 71. The second thermosensitive gel 72 may not envelop the first thermosensitive gel 71 and may be in contact with only a portion of the surface of the first thermosensitive gel 71.

[0114] The impermeable layer 12 encases the second thermosensitive gel 72. The impermeable layer 12 covers the entire surface of the second thermosensitive gel 72 and contacts the entire surface of the second thermosensitive gel 72. The impermeable layer 12 is hydrophobic or waterproof. Therefore, the impermeable layer 12 does not allow the first polar solvent and the second polar solvent provided in the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, to pass through. As a result, the first thermosensitive gel 71 and the second thermosensitive gel 72 are contained in a space surrounded by the impermeable layer 12. In addition, the first released polar solvent and the second released polar solvent released by the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, can be prevented from leaking from within the space to the outside of the space. This allows the coolant 4 to be used repeatedly for cooling.

[0115] The impermeable layer 12 is made of, for example, at least one selected from the group consisting of polyvinylidene chloride, silicone gel, polyethylene, and polyurethane.

[0116] The second LCST (Tb) of the second thermosensitive gel 72 is higher than the first LCST (Ta) of the first thermosensitive gel 71. The second LCST (Tb) is made higher than the first LCST by imparting weak hydrophilicity to the first thermosensitive polymer contained in the first thermosensitive gel 71 to lower the first LCST (Ta) and imparting strong hydrophilicity to the second thermosensitive polymer contained in the second thermosensitive gel 72 to raise the second LCST (Tb). The first LCST can be adjusted by adjusting the LCST of the first thermosensitive gel 71 itself by selecting the first thermosensitive gel 71, adjusting the ion concentration, adjusting the pH, etc. The second LCST can also be adjusted by adjusting the LCST of the second thermosensitive gel 72 itself by selecting the second thermosensitive gel 72, adjusting the ion concentration, adjusting the pH, etc.

[0117] The volume Va of the first thermosensitive gel 71, the concentration Da of the first thermosensitive polymer in the first thermosensitive gel 71, the volume Vb of the second thermosensitive gel 72, and the concentration Db of the second thermosensitive polymer in the second thermosensitive gel 72 at a temperature lower than the first LCST (Ta) of the first thermosensitive gel 71 are determined so that the second thermosensitive gel 72 can absorb the first released polar solvent released by the first thermosensitive gel 71 when a temperature rise exceeding the first LCST (Ta) occurs. For example, at a temperature lower than the first LCST (Ta), the volume Vb of the second thermosensitive gel 72 is set to be equal to or larger than the volume Va of the first thermosensitive gel 71, and the concentration Db of the second thermosensitive polymer is set to be the same as the concentration Da of the first thermosensitive polymer.

[0118] 24, when the temperature T1 of the heating element 61 is lower than the first LCST (Ta) of the first thermosensitive gel 71, the first thermosensitive gel 71 on the inside retains the first polar solvent without releasing it, and has a volume Va. The second thermosensitive gel 72 on the outside retains the second polar solvent without releasing it, and has a volume Vb. Therefore, the first polar solvent and the second polar solvent are not present between the first thermosensitive gel 71 and the second thermosensitive gel 72, and between the second thermosensitive gel 72 and the impermeable layer 12.

[0119] When the temperature T1 of the heating element 61 becomes higher than the first LCST (Ta) of the first thermosensitive gel 71, the first thermosensitive polymer in the first thermosensitive gel 71 changes from hydrophilic to hydrophobic. The change from hydrophilic to hydrophobic of the first thermosensitive polymer occurs before the change from hydrophilic to hydrophobic of the second thermosensitive polymer in the second thermosensitive gel 72. At that time, the first thermosensitive gel 71 releases the first released polar solvent. Also, the second thermosensitive gel 72 absorbs the first released polar solvent. Therefore, the first thermosensitive gel 71 contracts and has a volume Va' smaller than the volume Va. Also, the second thermosensitive gel 72 expands and has a volume Vb' larger than the volume Vb. The first released polar solvent does not accumulate between the first thermosensitive gel 71 and the second thermosensitive gel 72.

[0120] When the temperature T1 of the heating element 61 becomes higher than the second LCST (Tb) of the second thermosensitive gel 72 after the temperature T1 of the heating element 61 becomes higher than the first LCST (Ta) of the first thermosensitive gel 71, the second thermosensitive polymer contained in the second thermosensitive gel 72 changes from hydrophilic to hydrophobic. At that time, the second thermosensitive gel 72 releases the second released polar solvent. As a result, the second thermosensitive gel 72 contracts and has a volume Vb'' smaller than the volume Vb'. The second released polar solvent accumulates between the second thermosensitive gel 72 and the impermeable layer 12 and has a volume w.

[0121] When the temperature T1 of the heating element 61 becomes lower than the first LCST (Ta) of the first thermosensitive gel 71 again, the first thermosensitive gel 71 swells and has a volume Va again. The second thermosensitive gel 72 swells and has a volume Vb again. At that time, the first thermosensitive gel 71 and the second thermosensitive gel 72 absorb the accumulated second releasing polar solvent. Therefore, the first releasing polar solvent and the second releasing polar solvent are no longer present between the first thermosensitive gel 71 and the second thermosensitive gel 72, and between the second thermosensitive gel 72 and the impermeable layer 12.

[0122] As a result, the coolant 4 not only absorbs heat from the heating element in accordance with the heat capacity of the coolant 4, but also absorbs heat required for the endothermic reactions accompanying the first volume phase transition and the second volume phase transition caused by the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, from the surface of the heating element, and absorbs heat required for the first thermosensitive gel 71 and the second thermosensitive gel 72 to release the first releasing polar solvent and the second releasing polar solvent, respectively, from the surface of the heating element.

[0123] In addition, the first released polar solvent 81 and the second released polar solvent 82 released by the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, do not permeate the impermeable layer 12. Therefore, the first released polar solvent 81 and the second released polar solvent 82 remain inside the coolant 4 and do not leak out to the outside of the coolant 4. The remaining first released polar solvent 81 and the second released polar solvent 82 are absorbed by the second thermosensitive gel 72 when a temperature drop exceeding the second LCST occurs, and are absorbed by the first thermosensitive gel 71 when a temperature drop exceeding the first LCST occurs. This prevents the coolant 4 from losing the first polar solvent and the second polar solvent provided in the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively. This allows the coolant 4 to be used repeatedly.

[0124] FIG. 25 is a diagram showing a schematic diagram of a state in which the first released polar solvent released by the first thermosensitive gel is accumulated between the first thermosensitive gel and the second thermosensitive gel.

[0125] 25, when the first released polar solvent 81 released by the first thermosensitive gel 71 accumulates between the first thermosensitive gel 71 and the second thermosensitive gel 72, the first thermosensitive gel 71 and the second thermosensitive gel 72 are separated from each other by the accumulated first released polar solvent 81. This may result in a decrease in the cooling effect of the coolant 4 on the heat-generating body.

[0126] The thermosensitive gel provided in the cooling material 1 of the first embodiment is one thermosensitive gel 11. Therefore, in the cooling material 1 of the first embodiment, the properties of the thermosensitive gel change suddenly in a narrow temperature range near one LCST, and a sudden heat absorption occurs. Therefore, the heating element can be cooled suddenly.

[0127] In contrast, the thermosensitive gel provided in the cooling material 4 of the fourth embodiment is a combination of multiple thermosensitive gels each having multiple different LCSTs. Therefore, in the cooling material 4 of the fourth embodiment, the polar solvent and other contents are exchanged between the multiple thermosensitive gels. In addition, in a wide temperature range spanning the multiple LCSTs, the properties of the thermosensitive gel change gradually, and gradual heat absorption occurs. Therefore, the heating element can be cooled gradually. Therefore, it is possible to respond to gradual changes in the heating element. This feature becomes more prominent as the number of LCSTs of the multiple thermosensitive gels provided in the cooling material increases. This is because, as the number of multiple LCSTs increases, the change in the properties of the thermosensitive gel becomes multi-stage, and heat absorption becomes multi-stage.

[0128] FIG. 26 is a diagram illustrating a schematic diagram of a temperature change in the state of the coolant in the first modified example of the fourth embodiment.

[0129] In a first variant of the fourth embodiment, at a temperature lower than the first LCST (Ta), the volume Vb of the second thermosensitive gel 72 is made the same as the volume Va of the first thermosensitive gel 71, and the concentration Db of the second thermosensitive polymer is made lower than the concentration Da of the first thermosensitive polymer, so that the second thermosensitive gel 72 can absorb the first released polar solvent released by the first thermosensitive gel 71 when a temperature rise exceeding the first LCST (Ta) of the first thermosensitive gel 71 occurs. By making the concentration Db of the second thermosensitive polymer lower than the concentration Da of the first thermosensitive polymer, the second thermosensitive gel 72 is able to absorb the first released polar solvent released by the first thermosensitive gel 71 because the molecular spacing in the second thermosensitive gel 72 is wider than the molecular spacing in the first thermosensitive gel 71, and the amount of polar solvent that the second thermosensitive gel 72 can hold is greater than the amount of polar solvent that the first thermosensitive gel 71 can hold.

[0130] 26, in the first modified example, when the temperature T1 of the heating element 61 is lower than the first LCST (Ta) of the first thermosensitive gel 71, the first thermosensitive gel 71 on the inside holds the first polar solvent without releasing it, and has a volume Va. The second thermosensitive gel 72 on the outside holds the second polar solvent without releasing it, and has a volume Vb. Therefore, the first polar solvent and the second polar solvent are not present between the first thermosensitive gel 71 and the second thermosensitive gel 72, and between the second thermosensitive gel 72 and the impermeable layer 12.

[0131] When the temperature T1 of the heating element 61 becomes higher than the first LCST (Ta) of the first thermosensitive gel 71, the first thermosensitive polymer in the first thermosensitive gel 71 changes from hydrophilic to hydrophobic. The change from hydrophilic to hydrophobic of the first thermosensitive polymer occurs before the change from hydrophilic to hydrophobic of the second thermosensitive polymer in the second thermosensitive gel 72. At that time, the first thermosensitive gel 71 releases the first released polar solvent. Also, the second thermosensitive gel 72 absorbs the first released polar solvent. Therefore, the first thermosensitive gel 71 contracts and has a volume Va' smaller than the volume Va. Also, the second thermosensitive gel 72 expands and has a volume Vb' larger than the volume Vb. The first released polar solvent does not accumulate between the first thermosensitive gel 71 and the second thermosensitive gel 72.

[0132] When the temperature T1 of the heating element 61 becomes higher than the second LCST (Tb) of the second thermosensitive gel 72 after the temperature T1 of the heating element 61 becomes higher than the first LCST (Ta) of the first thermosensitive gel 71, the second thermosensitive polymer contained in the second thermosensitive gel 72 changes from hydrophilic to hydrophobic. At that time, the second thermosensitive gel 72 releases the second released polar solvent. As a result, the second thermosensitive gel 72 contracts and has a volume Vb'' smaller than the volume Vb'. The second released polar solvent accumulates between the second thermosensitive gel 72 and the impermeable layer 12 and has a volume w.

[0133] When the temperature T1 of the heating element 61 becomes lower than the first LCST (Ta) of the first thermosensitive gel 71 again, the first thermosensitive gel 71 swells and has a volume Va again. The second thermosensitive gel 72 swells and has a volume Vb again. At that time, the first thermosensitive gel 71 and the second thermosensitive gel 72 absorb the accumulated second releasing polar solvent. Therefore, the first releasing polar solvent and the second releasing polar solvent are no longer present between the first thermosensitive gel 71 and the second thermosensitive gel 72, and between the second thermosensitive gel 72 and the impermeable layer 12.

[0134] As a result, the coolant 4 not only absorbs heat from the heating element in accordance with the heat capacity of the coolant 4, but also absorbs heat required for the endothermic reactions accompanying the first volume phase transition and second volume phase transition caused by the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively, from the surface of the heating element, and absorbs heat required for the first thermosensitive gel 71 and the second thermosensitive gel 72 to release the first releasing polar solvent and the second releasing polar solvent 82, respectively, from the surface of the heating element.

[0135] In addition, the second released polar solvent 82 released by the second thermosensitive gel 72 does not permeate the impermeable layer 12. Therefore, the first released polar solvent and the second released polar solvent 82 remain inside the coolant 4 and do not leak out to the outside of the coolant 4. The remaining first released polar solvent and the second released polar solvent 82 are absorbed by the second thermosensitive gel 72 when a temperature drop exceeding the second LCST occurs, and are absorbed by the first thermosensitive gel 71 when a temperature drop exceeding the first LCST occurs. This prevents the coolant 4 from losing the first polar solvent and the second polar solvent provided in the first thermosensitive gel 71 and the second thermosensitive gel 72, respectively. This allows the coolant 4 to be used repeatedly.

[0136] FIG. 27 is a diagram showing a schematic diagram of the temperature change of the coolant state in the reference example.

[0137] In the reference example, at a temperature lower than the first LCST (Ta) of the first thermosensitive gel 71, the volume Vb of the second thermosensitive gel 72 is made smaller than the volume Va of the first thermosensitive gel 71, and the concentration Db of the second thermosensitive polymer is made lower than the concentration Da of the first thermosensitive polymer.

[0138] 27, when the temperature T1 of the heating element 61 is lower than the first LCST (Ta) of the first thermosensitive gel 71, the first thermosensitive gel 71 on the inside holds the first polar solvent without releasing it, and has a volume Va. The second thermosensitive gel 72 on the outside holds the second polar solvent without releasing it, and has a volume Vb. Therefore, the first polar solvent and the second polar solvent are not present between the first thermosensitive gel 71 and the second thermosensitive gel 72, and between the second thermosensitive gel 72 and the impermeable layer 12.

[0139] When the temperature T1 of the heating element 61 becomes higher than the first LCST (Ta), the first thermosensitive polymer in the first thermosensitive gel 71 changes from hydrophilic to hydrophobic. At that time, the first thermosensitive gel 71 releases the first releasing polar solvent. At that time, the second thermosensitive gel 72 absorbs a part of the first releasing polar solvent. Therefore, the first thermosensitive gel 71 contracts and has a volume Va' smaller than the volume Va. Also, the second thermosensitive gel 72 expands and has a volume Vb' larger than the volume Vb. However, the second thermosensitive gel 72 cannot absorb the entire first releasing polar solvent 81. Therefore, a part of the first releasing polar solvent 81 accumulates between the first thermosensitive gel 71 and the second thermosensitive gel 72.

[0140] When the temperature T1 of the heating element 61 becomes higher than the second LCST (Tb) after the temperature T1 of the heating element 61 becomes higher than the first LCST (Ta), the second thermosensitive polymer in the second thermosensitive gel 72 changes from hydrophilic to hydrophobic. At that time, the second thermosensitive gel 72 releases the second releasing polar solvent. Therefore, the second thermosensitive gel 72 shrinks and has a volume Vb'' smaller than the volume Vb'. The second releasing polar solvent accumulates between the second thermosensitive gel 72 and the impermeable layer 12 and has a volume w. At this time, the first releasing polar solvent 81 remains between the first thermosensitive gel 71 and the second thermosensitive gel 72. The first releasing polar solvent 81 that remains may inhibit the transfer of heat and reduce the ability of the coolant 4 to cool the heating element.

[0141] Next, an example of a method for producing the coolant 4 will be described.

[0142] When the coolant 4 is produced, a first solution containing a pre-crosslinked precursor of a first thermosensitive polymer and a first polar solvent is prepared.

[0143] Next, the prepared first solution is subjected to a gelation process such as a process for crosslinking the pre-crosslinking precursor, thereby producing a first thermosensitive gel 71 containing a first thermosensitive polymer and a first polar solvent.

[0144] Subsequently, a second solution is prepared, which includes a pre-crosslinked precursor of a second thermosensitive polymer and a second polar solvent.

[0145] Subsequently, the prepared second solution is applied to the surface of the produced first thermosensitive gel 71 .

[0146] Next, the applied second solution is subjected to a gelling process such as a process for crosslinking the pre-crosslinking precursor, thereby producing a second thermosensitive gel 72 containing a second thermosensitive polymer and a second polar solvent.

[0147] A cooling material having a multilayer structure with three or more layers can be produced by repeatedly applying a polymer solution containing a pre-crosslinked precursor of another thermosensitive polymer and another polar solvent to the surface of a thermosensitive gel containing one thermosensitive polymer and one polar solvent, and then performing a gelling process on the applied polymer solution to produce a thermosensitive gel containing another thermosensitive polymer and another polar solvent. When this process is repeated, the volume, thickness, etc. of the thermosensitive gel can be adjusted by changing the number of times the process is repeated.

[0148] Instead of applying the solution to the surface of the thermosensitive gel, the thermosensitive gel may be immersed in the solution. When the thermosensitive gel is immersed in the solution, the volume, thickness, etc. of the thermosensitive gel can be adjusted by changing the time for which the thermosensitive gel is immersed in the solution.

[0149] The cooling material 4 may include three or more types of thermosensitive gels. In this case, the volume of the outer thermosensitive gel is preferably made larger than the volume of the inner thermosensitive gel. When the volume of the outer thermosensitive gel is the same as or smaller than the volume of the inner thermosensitive gel, the concentration of the outer thermosensitive gel is preferably made lower than the concentration of the inner thermosensitive gel, and the amount of polar solvent that the outer thermosensitive gel can contain is preferably made larger than the amount of polar solvent that the inner thermosensitive gel can contain.

[0150] 5 Fifth embodiment The following describes the differences between the fifth embodiment and the first embodiment. For points that are not described, the fifth embodiment employs the same configuration as that employed in the first embodiment.

[0151] FIG. 28 is a cross-sectional view that diagrammatically illustrates a heat pump including the heat pump refrigerant of the fifth embodiment.

[0152] 28 circulates a heat pump refrigerant 101 of the fifth embodiment along a circulation path 102 in a circulation direction D. The temperature of the circulated heat pump refrigerant 101 is high in a first section 111 of the circulation path 102 and is low in a second section 112 of the circulation path 102.

[0153] 28, the heat pump refrigerant 101 includes the coolant 2 of the second embodiment and a liquid refrigerant 121. The heat pump refrigerant 101 may include the coolant 4 of the fourth embodiment instead of the coolant 2 of the second embodiment.

[0154] The coolant 2 has a particulate shape. The coolant 2 is mixed into the liquid refrigerant 121. The coolant 2 is dispersed in the liquid refrigerant 121 and circulated together with the liquid refrigerant 121 along the circulation path 102 in the circulation direction D. Therefore, the temperature of the coolant 2 is high in the first section 111 of the circulation path 102 and is low in the second section 112 of the circulation path 102.

[0155] FIG. 29 is a diagram that illustrates a schematic diagram of a temperature change in a state of a coolant provided in the heat pump refrigerant of the fifth embodiment.

[0156] As shown in FIG. 29, when the coolant 2 is transported to the first section 111 and has a high temperature, a volume phase transition accompanied by an endothermic reaction occurs. At that time, the polar solvent 22 contained in the thermosensitive gel 11 becomes easy to move. As a result, the thermosensitive gel 11 releases the released polar solvent 31 and contracts. The released polar solvent 31 remains inside the impermeable layer 12. All or part of the released polar solvent 31 evaporates. The change ΔH in the enthalpy H at this time is positive (ΔH>0). Also, the change ΔS in the entropy S at this time is positive (ΔS>0). Also, when the temperature is T, the change ΔG=ΔH-TΔS in the Gibbs free energy G of the system composed of the thermosensitive gel 11 and the released polar solvent 31 at this time is negative (ΔG<0) under the condition that the environmental temperature in the refrigerant to which the system is exposed is sufficiently high.

[0157] On the other hand, when the coolant 1 is transported to the second section 112 and has a low temperature, it undergoes a volume phase transition accompanied by an exothermic reaction. At that time, all or part of the evaporated released polar solvent 31 is condensed. The thermosensitive gel 11 also absorbs the remaining released polar solvent 31 and swells. The change ΔH in enthalpy H at this time is negative (ΔH<0). The change ΔS in entropy S at this time is negative (ΔS<0). The change ΔG=ΔH-TΔS in Gibbs free energy G of the system composed of the thermosensitive gel 11 and the released polar solvent 31 at this time is negative (ΔG<0) under the condition that the environmental temperature in the refrigerant to which the system is exposed is sufficiently low.

[0158] Therefore, when the coolant 1 is transported to the first section 111 and has a high temperature, it undergoes a volume phase transition accompanied by an endothermic reaction to absorb the heat of reaction, increases the entropy S to absorb heat, and evaporates all or part of the released polar solvent 31 to absorb the latent heat.

[0159] On the other hand, when the coolant 1 is transported to the second section 112 and has a low temperature, it undergoes a volume phase transition accompanied by an exothermic reaction, releasing heat of reaction, reducing the entropy S and releasing heat, and condensing the evaporated released polar solvent 31, releasing latent heat.

[0160] As a result, the heat pump refrigerant 101 consisting of the coolant 2 and the liquid refrigerant 121 has a higher heat transport capacity than a heat pump refrigerant consisting only of the liquid refrigerant 121. This allows the amount of heat pump refrigerant 101 used to be reduced.

[0161] The present disclosure is not limited to the above-described embodiments, and may be replaced with a configuration that is substantially the same as the configuration shown in the above-described embodiments, a configuration that has the same action and effect, or a configuration that can achieve the same purpose. [Explanation of symbols]

[0162] 1,2,3,4 Cooling material, 11 Thermosensitive gel, 12 Impermeable layer, 21 Thermosensitive polymer, 22 Polar solvent, 31 Emitting polar solvent, 41 Circuit board, 41a First main surface, 41b Second main surface, 42 Capacitor, 42a Outer peripheral surface, 42b Top surface, 43 Cylindrical heating element, 43s Cylindrical space, 51 First portion, 52 Second portion, 61 Heating element, 71 First thermosensitive gel, 72 Second thermosensitive gel, 81 First emitting polar solvent, 82 Second emitting polar solvent, 91 Heat pump, 101 Heat pump refrigerant, 102 Circulation path, 111 First section, 112 Second section, 121 Liquid refrigerant, D Circulation direction.

Claims

1. A thermosensitive gel comprising: a thermosensitive polymer that is hydrophilic at a temperature lower than a lower critical solution temperature and hydrophobic at a temperature higher than the lower critical solution temperature; and a polar solvent that wets the thermosensitive polymer, the thermosensitive gel undergoing a volume phase transition accompanied by an endothermic reaction when a temperature rise exceeds the lower critical solution temperature. A cooling material comprising:

2. The temperature-sensitive gel contracts and releases a portion of the polar solvent when the temperature rise occurs. The coolant of claim 1.

3. The thermosensitive gel is covered with an impermeable layer that does not allow the polar solvent to pass therethrough. The coolant according to claim 1 or 2.

4. The impermeable layer contains at least one selected from the group consisting of polyvinylidene chloride, silicone gel, polyethylene, and polyurethane. The coolant according to claim 3.

5. the lower critical solution temperature is a first lower critical solution temperature, the thermosensitive polymer is a first thermosensitive polymer, the polar solvent is a first polar solvent, the volume phase transition is a first volume phase transition, the thermosensitive gel is a first thermosensitive gel, The thermosensitive gel includes a second thermosensitive polymer that is hydrophilic at a temperature lower than a second lower critical solution temperature different from the first lower critical solution temperature and that is hydrophobic at a temperature higher than the second lower critical solution temperature, and a second polar solvent that wets the second thermosensitive polymer. The second thermosensitive gel is in contact with the first thermosensitive gel and undergoes a second volume phase transition when a temperature change that exceeds the second lower critical solution temperature occurs. The coolant according to claim 1 or 2.

6. The coolant has a filamentous shape, the first thermosensitive gel is a core; The second thermosensitive gel is a sheath that covers the front core, The second lower critical solution temperature is lower than the first lower critical solution temperature. The coolant according to claim 5.

7. an impermeable layer that covers the sheath and is impermeable to the first polar solvent and the second polar solvent; The coolant according to claim 6.

8. The impermeable layer contains at least one selected from the group consisting of polyvinylidene chloride, silicone gel, polyethylene, and polyurethane. The coolant of claim 7.

9. The second lower critical solution temperature is higher than the first lower critical solution temperature. The coolant according to claim 5.

10. The second thermosensitive gel envelops the first thermosensitive gel. The coolant of claim 9.

11. At a temperature lower than the first lower critical solution temperature, the volume of the second thermosensitive gel is greater than the volume of the first thermosensitive gel. The coolant of claim 9.

12. At a temperature lower than the first lower critical solution temperature, the concentration of the second thermosensitive polymer in the second thermosensitive gel is lower than the concentration of the first thermosensitive polymer in the first thermosensitive gel. The coolant of claim 9.

13. The thermosensitive polymer is (1) At least one polymer selected from the group consisting of cellulose derivatives, polyvinyl ethers, polyvinyl ether derivatives, poly(N-alkyl(meth)acrylamides), poly(N-alkyl(meth)acrylamides) derivatives, poly(N-vinyl alkylamides), poly(N-vinyl alkylamides) derivatives, poly(N-vinyl pyrrolidone), poly(N-vinyl pyrrolidone) derivatives, poly(2-alkyl-2-oxazolines), poly(2-alkyl-2-oxazolines) derivatives, polyvinyl alkyl ethers, polyvinyl alkyl ether derivatives, copolymers of polyethylene oxide and polypropylene oxide, derivatives of copolymers of polyethylene oxide and polypropylene oxide, poly(oxyethylene vinyl ethers) and poly(oxyethylene vinyl ether) derivatives; (2) a copolymer of at least two polymers selected from the above group; and (3) A crosslinked product of at least one polymer selected from the group consisting of the at least one polymer and a copolymer of the at least two polymers. At least one selected from the group consisting of The coolant according to claim 1 or 2.

14. The thermosensitive gel is (1) at least one polymer selected from the group consisting of polyethylene glycol, 2-methacryloyloxyethyl phosphorylcholine, poly(meth)acrylic acid, poly(meth)acrylates, alginic acid, alginates, hyaluronic acid, hyaluronates, chitosan, and cellulose derivatives; (2) a copolymer of at least two polymers selected from the above group; and (3) A crosslinked product of at least one polymer selected from the group consisting of the at least one polymer and a copolymer of the at least two polymers. At least one selected from the group consisting of The coolant according to claim 1 or 2.

15. The polar solvent includes at least one selected from the group consisting of water and an ionic liquid. The coolant according to claim 1 or 2.

16. The cooling material has a plate-like, thread-like, mesh-like, spherical, cone-like, rod-like, string-like, coil-like, folding screen-like, granular or pulverized shape, or a plate-like or cloth-like outer shape with a plurality of holes formed therein. The coolant according to claim 1 or 2.

17. A coolant according to claim 3; a liquid refrigerant into which the cooling material is mixed; A refrigerant for a heat pump comprising:

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