JP7670085B2 - Radiative cooling device - Google Patents

Description

This disclosure relates to a radiative cooling device.

Patent Document 1 discloses a radiative cooling device that includes a bag and a working fluid. The bag has a heat receiving part that is connected to a heat generating element, and a radiative cooling part that has thermal radiation properties. The working fluid is sealed inside the bag and transports heat from the heat receiving part to the radiative cooling part by undergoing a phase change. The bag of the radiative cooling device is soft, flexible, or stretchable, and expands and contracts due to the phase change of the working fluid.

JP 2022-64592 A

However, in the case of the device of Patent Document 1, heat is transferred from a heating element arranged on the outside of the bag to the working fluid inside the bag via a heat receiving portion that constitutes part of the bag. For this reason, there is room for improvement in the efficiency of heat transfer from the heating element to the working fluid.

The present disclosure aims to improve the efficiency of heat transfer from a heating element to a working fluid in a configuration in which a phase-changing working fluid is sealed inside a bag that has a radiative cooling section with thermal radiation properties and can expand and contract.

The radiative cooling device of the first aspect of the present disclosure comprises a bag having a radiative cooling part with thermal radiation properties, which is expandable and contractible, a heating element disposed inside the bag, and a working fluid sealed inside the bag and which transports heat from the heating element to the radiative cooling part by undergoing a phase change, and the heating element is disposed in a portion of the bag in an expanded state where the working fluid in liquid phase accumulates.

In the radiative cooling device of the first aspect, the liquid phase working fluid in the bag changes to a gas phase (steam) due to the heat of the heating element. This phase change of the working fluid increases the internal pressure of the bag, and the bag expands. The expansion of the bag increases the radiation area of the bag. In addition, when the heat of the steam is transferred to the radiative cooling section, the thermal energy of the heat transferred to the radiative cooling section is released as electromagnetic waves. When the heat of the steam is taken away by the radiative cooling section, the working fluid changes from a gas phase to a liquid phase. That is, the working fluid condenses from the vapor to droplets. These droplets fall down the inner surface of the bag by their own weight, and a working fluid pool is formed in the bag. Here, in the radiative cooling device of the first aspect, the heating element is arranged inside the bag and in a part of the bag in an expanded state where the liquid phase working fluid pools, so that the heat of the heating element can be directly transferred to the working fluid. As a result, in the above cooling device, the efficiency of heat transfer from the heating element to the working fluid can be improved, for example, compared to a configuration in which heat is transferred from a heating element arranged outside the bag to the working fluid in the bag through a part of the bag. Furthermore, when the temperature of the heating element drops, the internal pressure of the bag drops as the temperature of the working fluid drops, causing the bag to shrink from its expanded state.

The radiative cooling device of the second aspect of the present disclosure is the radiative cooling device of the first aspect, in which the heat generating body is a heat exchanger having a flow path through which a heat medium flows, and the bag body is fitted with a circulation path for circulating the heat medium from the outside of the bag body to the heat exchanger inside.

In the second embodiment of the radiative cooling device, the heat medium is sent from outside the bag body through a circulation path to the heat exchanger. Heat exchange is then carried out between the heat medium and the working fluid via the heat exchanger, and the heat medium cooled by the heat exchange is sent to the outside of the bag body through the circulation path. In this way, the second embodiment of the radiative cooling device can continuously cool the heat medium circulated through the circulation path.

The third aspect of the radiative cooling device of the present disclosure is the radiative cooling device of the first aspect, in which the heating element is fixed to the inner surface of the bag body.

In the third aspect of the radiative cooling device, the heating element is fixed to the inner surface of the bag, so that the heating element can be held in a predetermined position in the part of the bag where the working fluid accumulates in the expanded state, compared to a configuration in which the heating element can move freely inside the bag.

The radiative cooling device of the fourth aspect of the present disclosure is the radiative cooling device of the first aspect, which has a core body that can rotate around an axis and to which a rotational moment is applied, and the bag body is stored in a roll around the core body and unfolds and expands due to an increase in internal pressure.

In the fourth aspect of the radiative cooling device, the bag is stored in a roll around the core, allowing it to be stored compactly when not in use.

The radiative cooling device of the fifth aspect of the present disclosure is the radiative cooling device of the fourth aspect, further comprising a guide member that is disposed at a distance from the axis of the core body and contacts the bag body to suppress rotation of the bag body around the core body.

In the radiative cooling device of the fifth aspect, when the bag body is deployed, the guide member comes into contact with the bag body, suppressing rotation of the bag body around the core body. This prevents the bag body from flapping when rotated, and allows the bag body to be deployed stably in a specified direction. Similarly, when the bag body is rolled up for storage, the guide member comes into contact with the bag body, suppressing rotation of the bag body around the core body. This prevents the bag body from flapping when rotated, and allows the bag body to be stored stably.

The sixth aspect of the radiative cooling device of the present disclosure is the fifth aspect of the radiative cooling device, in which the length of the heating element is 1.5 times or less than the diameter of the core body when viewed in a cross section perpendicular to the rotation axis of the core body.

In the radiative cooling device of the sixth aspect, the length of the heating element is 1.5 times or less than the diameter of the core body when viewed in a cross section perpendicular to the rotation axis of the core body. This makes it possible to suppress damage to the bag body caused by the heating element when the bag body is stored and deployed, compared to a configuration in which the length of the heating element exceeds 1.5 times the diameter of the core body, for example.

The seventh aspect of the radiative cooling device of the present disclosure is the fifth aspect of the radiative cooling device, in which the heating element has a curved portion that curves to fit along the outer periphery of the core body.

In the seventh aspect of the radiative cooling device, the heating element has a curved portion that curves to fit the outer circumference of the core body, so when storing the bag body in a roll around the core body, the heating element can be easily wrapped around the core body, making the bag body storage operation smooth.

The radiative cooling device of the eighth aspect of the present disclosure is the radiative cooling device of the fourth aspect, in which the heating element is made of a flexible material.

In the radiative cooling device of the eighth aspect, the heating element is made of a flexible material, so that when the bag is rolled up around the core, the heating element can easily follow the deformation of the bag, making the bag storage operation smooth.

The radiative cooling device of the ninth aspect of the present disclosure is the radiative cooling device of the fifth aspect, in which a support member that supports the bag body is arranged on the opposite side of the guide member, sandwiching the bag body.

In the ninth aspect of the radiative cooling device, the bag body is supported by a support member, so the bag body is less likely to bend during deployment and can be deployed in the desired direction.

According to the present disclosure, in a configuration in which a phase-changing working fluid is sealed inside a bag that has a radiative cooling section with thermal radiation properties and can expand and contract, it is possible to improve the efficiency of heat transfer from a heating element to the working fluid.

FIG. 1 illustrates a radiative cooling device according to an embodiment of the present disclosure, with the bag deployed. This shows a state in which the bag body shown in FIG. 1 is stored. 2 is a view of the core body and the guide member shown in FIG. 1 as viewed from the deployment direction of the bag body. 1 is a radiative cooling device according to another embodiment of the present disclosure, showing the bag deployed. FIG. 13 is a plan view showing the inner surface of the bag in a radiative cooling device according to another embodiment of the present disclosure. 1 is a radiative cooling device according to another embodiment of the present disclosure, showing the bag deployed. 1 is a radiative cooling device according to another embodiment of the present disclosure, showing the bag deployed. FIG. 1 illustrates an application example of the radiative cooling device of the present disclosure.

The following describes a radiative cooling device 20 according to one embodiment of the present disclosure.

As shown in Figs. 1 and 2, the radiative cooling device 20 includes a bag body 40, a heating element HE, and a working fluid F. The radiative cooling device 20 also includes a core body 30 and a guide member 50. Note that the present disclosure is not limited to the above configuration, and may include a radiative cooling device 20 including a core body 30 and a guide member 50.

(Core body)
3, the core body 30 has a shaft portion 30A and a winding portion 30B. The winding portion 30B is a portion for winding up the bag body 40, and is provided on the outer periphery of the central portion of the shaft portion 30A.

The core body 30 is configured to be rotatable around its axis. Specifically, both ends 30C of the shaft portion 30A constituting the core body 30 are rotatably supported by a pair of bearing portions 32. The pair of bearing portions 32 are fixed to a pair of support frames 34 that are arranged opposite each other in the axial direction of the core body 30 (in other words, the axial direction of the shaft portion 30A).

The core body 30 is configured to be applied with a rotational moment (in other words, a rotational force, a torque). Specifically, the rotational moment is applied by a constant-force spring 36 attached to the core body 30. The constant-force spring 36 is a spring that has a constant elastic force regardless of the length extended from the natural length attached to the core body 30. The constant-force spring 36 is also exteriorized with one end connected to a rod-shaped connecting member 35 that connects and fixes a pair of support frames 34. The other end of the constant-force spring 36 is connected to a winding section 30D provided on the shaft section 30A of the core body 30. When the bag body 40 described later is deployed, the core body 30 rotates (rotates counterclockwise in FIG. 1), and the constant-force spring 36 is pulled out from the connecting member 35 side and wound up on the winding section 30D of the core body 30. On the other hand, when the bag body 40 is stored, the core body 30 rotates in the opposite direction to when it is deployed (clockwise in FIG. 1), and the constant force spring 36 is wound back toward the connecting member 35. In other words, the constant force spring 36 returns to its original state. In this embodiment, the connecting member 35 is disposed on the opposite side of the pair of support frames 34 from the deployment direction of the bag body 40 so as not to interfere with the bag body 40.

(Bag body)
As shown in FIG. 1, the bag body 40 is stored in a roll around the core body 30 and is configured to be deployed (see FIG. 1) when the internal pressure increases. As shown in FIG. 1, one end of the bag body 40 is connected to the winding part 30B of the core body 30, and the other end is a free end. Therefore, when the internal pressure of the bag body 40 increases, the bag body 40 expands (inflates) and is deployed. On the other hand, when the internal pressure of the bag body 40 decreases, the bag body 40 shrinks (contracts) and is wound up in a roll around the core body 30 and stored. Specifically, when the internal pressure (deployment force) of the bag body 40 exceeds the rotational moment (storage force) applied to the core body 30, the core body 30 rotates (rotates counterclockwise in FIG. 1) and the bag body 40 is deployed. On the other hand, when the internal pressure of the bag body 40 in the deployed state becomes less than the rotational moment applied to the core body 30, the core body 30 rotates in the reverse direction (clockwise in FIG. 1), and the bag body 40 is wound up by the winding section 30B and stored in a roll (see FIG. 2). As shown in FIG. 1, the bag body 40 in this embodiment is deployed so that the other end, which is a free end, is located above the one end connected to the winding section 30B in the direction of gravity. In other words, in this embodiment, the bag body 40 is deployed obliquely upward with respect to the horizontal direction.

The bag body 40 also has a radiative cooling section 44 that has thermal radiation properties. This radiative cooling section 44 may constitute a part of the bag body 40, or may constitute the entire bag body 40. In this embodiment, the entire bag body 40 is constituted by the radiative cooling section 44. The inside of this bag body 40 is sealed.

The bag body 40 has a degree of flexibility that allows it to be deployed and stored. In this embodiment, as an example, the bag body 40 is made of a flexible material such as vinyl. This allows the bag body 40 to be deployed and stored.

The bag body 40 is at least partially made of a heat-emitting material. Specifically, at least the surface of the radiative cooling section 44 of the bag body 40 is made of a heat-emitting material such as a heat-emitting film. The entire radiative cooling section 44 may be made of a heat-emitting material such as a heat-emitting film, or the bag body 40 may be made of a heat-emitting material such as a heat-emitting film.

(Hydraulic fluid)
A fluid is sealed inside the bag 40. This fluid includes a working fluid F that transfers heat from the heating element HE in the bag 40 to the radiative cooling unit 44 with a phase change. As the working fluid F, for example, water or a fluorocarbon substitute may be used. However, the type of the working fluid F is not limited to these.

(Heater)
A heating element HE is disposed inside the bag body 40. Specifically, as shown in FIG. 1, the heating element HE is disposed in a portion of the bag body 40 in an expanded state where the liquid-phase working fluid F accumulates. Here, as shown in FIG. 1, the bag body 40 of this embodiment is deployed so that the other end, which is a free end, is located above the one end in the direction of gravity, so that in the deployed state (expanded state), the liquid-phase working fluid F accumulates on the one end side. In this embodiment, as an example, the portion of the bag body 40 supported by (the portion in contact with) the support member 52 is a low portion of the bag body 40. Therefore, in the example of FIG. 1, the liquid-phase working fluid F accumulates in this low portion. The heating element HE is disposed in the pool of the working fluid F.

The heating element HE in this embodiment is, as an example, a heat exchanger. This heat exchanger has a flow path through which a heat medium flows inside. A circulation path 31 that circulates the heat medium to this heat exchanger is attached to the bag body 40. Specifically, a first flow path 31A and a second flow path 31B that constitute the circulation path 31 are attached to the bag body 40. The first flow path 31A and the second flow path 31B each extend in a direction perpendicular to the deployment direction of the bag body 40, that is, in the width direction of the bag body 40, and penetrate the bag body 40. The first flow path 31A and the bag body 40 are sealed. The second flow path 31B and the bag body 40 are also sealed. This maintains airtightness inside the bag body 40.

The heating element HE is fixed to the inner surface of the bag body 40. Specifically, when the bag body 40 is in an expanded state, the heating element HE is fixed to the inner surface (lower surface) located below the bag body 40. The heating element HE is also fixed to the bag body 40 using an adhesive or the like.

2, the length L of the heating element HE may be 1.5 times or less than the diameter d of the core body 30 when viewed in a cross section perpendicular to the rotation axis of the core body 30. The length of the heating element HE is the length along the tangent direction passing through the intersection of the center line connecting the center of the heating element HE and the center of the core body 30 with the outer circumferential surface of the core body 30 when the stored state of the bag body 40 is viewed in a cross section perpendicular to the rotation axis of the core body 30.

Also, as shown in Figs. 1 and 2, the heating element HE may have a curved portion HEC that curves to follow the outer periphery of the core body 30. When the bag body 40 is stored in a rolled state, as shown in Fig. 2, the curved portion HEC of the heating element HE follows the outer periphery of the core body 30.

In addition, since the heating element HE in this embodiment is a heat exchanger, it is preferable to use a metal material with excellent thermal conductivity. Examples of such metal materials include aluminum and copper.

(Guide member)
The guide member 50 is arranged apart from the axis of the core body 30 and is configured to contact the bag body 40 to suppress the rotation of the bag body 40 around the core body 30. Specifically, the guide member 50 is arranged above the core body 30. In this embodiment, as an example, the guide member 50 is arranged in the deployment direction of the bag body 40 (right side in FIG. 2) from the core body 30. The guide member 50 is rod-shaped, and both ends are fixed to a pair of support frames 34. The guide member 50 is curved at a portion that contacts the bag body 40 in a cross-sectional view perpendicular to the axis of the core body 30. Specifically, the guide member 50 in this embodiment has a circular outer shape in a cross-sectional view.

As shown in FIG. 1, when the heat of the heating element HE is transferred to the working fluid F in the bag body 40 wound in a roll shape around the core body 30, the working fluid F is heated. When the working fluid F is heated, the working fluid F changes phase from liquid to gas phase, and steam V is generated. At this time, the internal pressure of the bag body 40 increases with the rise in temperature of the working fluid F, and the bag body 40 expands. Then, the core body 30 rotates, and the bag body 40 is deployed. When the bag body 40 is deployed, the guide member 50 comes into contact with the bag body 40 and guides the bag body 40 in the deployment direction. In this embodiment, the deployment direction of the bag body 40 is diagonally upward from the horizontal direction, as described above.

When the steam V generated inside the bag body 40 reaches the radiative cooling section 44, the heat of the steam V is transferred to the radiative cooling section 44, and the thermal energy of the heat transferred to the radiative cooling section 44 is released as electromagnetic waves EW. When the heat of the steam V is thus taken away by the radiative cooling section 44, the steam V changes from the gas phase to the liquid phase, and the steam V condenses into droplets D. These droplets D fall due to their own weight.

The above operations are repeated, and the heat of the heating element HE is transported to the radiative cooling section 44 of the bag body 40 by a so-called thermosiphon method accompanied by a phase change of the working fluid F, and the heating element HE is cooled via the core body 30 by emitting thermal energy from the radiative cooling section 44 as electromagnetic waves EW.

When the heating element HE is cooled and the temperature of the core body 30 drops, the internal pressure of the bag body 40 drops with the fall in temperature of the working fluid F, causing the bag body 40 to contract from its expanded state, and is wound up and stored in a roll by the rotation of the core body 30. When storing the bag body 40, the guide member 50 comes into contact with the bag body 40 and guides the bag body 40 in the storing direction.

As described above, the core body 30, the bag body 40, and the guide member 50 of this embodiment constitute a radiative cooling device 20 that functions as a radiator that cools the heat generating body HE by emitting thermal energy of the heat generating body HE as electromagnetic waves EW.

As shown in Figs. 1 and 2, a support member 52 that supports the bag body 40 is disposed on the opposite side of the guide member 50 across the bag body 40. Specifically, the support member 52 is disposed below the guide member 50 and supports the bag body 40 from below. In this embodiment, the support member 52 has a flat upper surface, and supports the bag body 40 on this flat surface. Also, in this embodiment, as shown in Fig. 1, in the deployed state of the bag body 40, the portion supported by the support member 52 is lower than the other portions, and liquid phase hydraulic fluid F is stored in this portion. A heating element HE is disposed in this liquid pool.

Next, the operation of this embodiment will be described.
In the radiative cooling device 20 of this embodiment, the liquid-phase working fluid F in the bag body 40 changes to a gas phase (steam V) due to the heat of the heating element HE. This phase change of the working fluid F increases the internal pressure of the bag body 40, and the bag body 40 expands. The expansion of the bag body 40 increases the radiation area of the bag body 40. In addition, when the heat of the steam V is transferred to the radiative cooling section 44, the thermal energy of the heat transferred to the radiative cooling section 44 is released as an electromagnetic wave. When the heat of the steam V is taken away by the radiative cooling section 44, the working fluid F changes from a gas phase to a liquid phase (droplets D). That is, the working fluid F is condensed from the steam V to droplets D. The droplets D fall along the inner surface of the bag body 40 due to their own weight, and a working fluid pool is formed in the bag body 40. Here, in the radiative cooling device 20 of this embodiment, the heating element HE is disposed inside the bag body 40 and in a portion where the liquid-phase working fluid F accumulates in the expanded bag body 40, so that the heat of the heating element HE can be directly transferred to the working fluid F. As a result, in the radiative cooling device 20, the efficiency of heat transfer from the heating element HE to the working fluid F can be improved, compared to a configuration in which heat is transferred from the heating element HE disposed outside the bag body 40 to the working fluid F inside the bag body 40 via a part of the bag body 40, for example.

In this embodiment, the surface of the radiative cooling section 44 of the bag body 40 is made of a thermally radiative material, so that the heat from the heating element HE can be radiated efficiently.

In addition, in the radiative cooling device 20 of this embodiment, the heat medium is sent from the outside of the bag body 40 through the circulation path 31 to the heat exchanger. Then, heat exchange is performed between the heat medium and the working fluid F via the heat exchanger, and the heat medium cooled by the heat exchange is sent to the outside of the bag body 40 through the circulation path 31. In this way, in the radiative cooling device 20, the heat medium circulated through the circulation path 31 can be continuously cooled.

By fixing the heating element HE to the inner surface of the bag body 40, the heating element HE can be held in a predetermined position in the portion of the bag body 40 where the working fluid F accumulates in the expanded state, compared to a configuration in which the heating element HE can move freely within the bag body 40. Since the bag body 40 can be held in a predetermined position in this way, the heat of the heating element HE can be stably transferred to the working fluid F.

In the radiative cooling device 20 of this embodiment, the bag body 40 is stored in a roll around the core body 30, so it can be stored compactly when not in use. Therefore, even if the bag body 40 is installed outdoors, for example, as long as the bag body 40 is in a stored state, damage to the bag body 40 can be suppressed even in bad weather, etc.

In the radiative cooling device 20 of this embodiment, when the bag body 40 is deployed, the guide member 50 comes into contact with the bag body 40, suppressing the rotation of the bag body 40 around the core body 30. Therefore, the bag body 40 does not flap due to rotation, and the bag body 40 can be stably deployed in a specified direction. Similarly, when the bag body 40 is rolled up and stored, the guide member 50 comes into contact with the bag body 40, suppressing the rotation of the bag body 40 around the core body 30. Therefore, the bag body 40 does not flap due to rotation, and the bag body 40 can be stably stored.

In the radiative cooling device 20 of this embodiment, the length L of the heating element HE is 1.5 times or less than the diameter d of the core body 30 when viewed in a cross section perpendicular to the rotation axis of the core body 30. This makes it possible to suppress damage to the bag body 40 caused by the heating element HE when the bag body 40 is stored and deployed, compared to a configuration in which the length L of the heating element HE exceeds 1.5 times the diameter d of the core body 30, for example.

In the radiative cooling device 20 of this embodiment, the heating element HE has a curved portion HEC that curves to follow the outer circumference of the core body 30. This makes it easier to wrap the heating element HE around the core body 30 when storing the bag body 40 in a roll around the core body 30, making the storing operation of the bag body 40 smooth. In addition, it is possible to prevent the heating element HE from scratching the inner surface of the bag body 40 when storing the bag body 40.

In the radiative cooling device 20 of this embodiment, the bag body 40 is supported by the support member 52, so the bag body is less likely to bend during deployment and can be deployed in the desired direction.

[Other embodiments]
In the above embodiment, the heating element HE is made of a metal material having excellent thermal conductivity, but the present disclosure is not limited to this configuration. For example, the heating element HE may be made of a material having flexibility. By making the heating element HE of a material having flexibility in this way, when the bag body 40 is stored in a roll shape around the core body 30, the heating element HE is likely to follow the deformation of the bag body 40, and the storing operation of the bag body 40 becomes smooth. In addition, it is possible to suppress the heating element HE from scratching the inner surface of the bag body 40 when storing the bag body 40. It is preferable that the heating element HE is made of a material having excellent thermal conductivity and flexibility.

In the above embodiment, the upper surface of the support member 52 that supports the bag body 40 in the expanded state is flat, but the present disclosure is not limited to this configuration. The portion of the support member 52 that supports the bag body 40 may be curved. Specifically, the support member 52 may have a circular cross section. By making the support member 52 have a circular cross section in this manner, it is possible to prevent the support member 52 from scratching the outer surface of the bag body 40.

In the above embodiment, a rotational moment is applied to the core body 30 by the constant force spring 36, but the present disclosure is not limited to this configuration. For example, instead of the constant force spring 36, one end of a linear member may be attached to the shaft portion 30A of the core body 30, and a weight may be attached to the other end of this linear member. Even in this case, a rotational moment can be applied to the core body 30. Also, for example, instead of the constant force spring 36, a rotational moment may be applied to the core body 30 from an electric motor.

In the above embodiment, the bag body 40 is expanded diagonally upward to return the droplets D due to its own weight to the core body 30 located below, but the present disclosure is not limited to this configuration. For example, as shown in FIG. 5, a plurality of wicks 58 may be provided on the inner surface of the bag body 40 from one end to the other end of the bag body 40. For example, a hydrophilic porous polymer is used for the plurality of wicks 58. Each of the plurality of wicks 58 extends in a direction perpendicular to the core body 30 when the bag body 40 is stored in a roll shape. In addition, the plurality of wicks 58 are arranged at intervals in the axial direction of the core body 30. The plurality of wicks 58 may have either the same shape or different shapes. By providing a plurality of wicks 58 on the inner surface of the bag body 40 in this way, the droplets D condensed in the radiative cooling unit 44 can be transported to the position where the heating element HE is arranged by the capillary force generated by the plurality of wicks 58. By using multiple wicks 58, as shown in FIG. 4, even if the deployment direction of the bag body 40 is horizontal, the droplets D can be easily returned to the core body 30 side. This allows the droplets D to be transported to one end side (the end side of the core body 30) of the bag body 40 to form a liquid pool. Note that the wicks 58 may be provided on the entire inner surface of the bag body 40.

In the above embodiment, the cross-sectional shape of the guide member 50 is circular, but the present disclosure is not limited to this configuration. For example, it is sufficient that only the portion that contacts the bag body 40, like the guide member 50, is curved in an arc. Similarly, it is sufficient that only the portion that contacts the bag body 40 (the portion that supports the bag body 40) of the support member 52 is curved in an arc.

In the above embodiment, the fluid is sealed inside the bag body 40, but the present disclosure is not limited to this configuration. For example, as shown in FIG. 6, the configuration may be such that the hydraulic fluid F is supplied and discharged from the outside into the bag body 40. Specifically, the device includes a tank 60 that stores the hydraulic fluid F, a pipe 62 that connects the tank 60 and the bag body 40, a conveying device 64 that feeds and discharges the hydraulic fluid F between the tank 60 and the bag body 40, and a control unit 70 that controls the conveying device 64. The conveying device 64 is configured to convey the hydraulic fluid F from the tank 60 to the bag body 40, as well as to convey the hydraulic fluid F from the bag body 40 to the tank 60. As a result, in addition to the function of expanding the bag body 40 from a contracted state, the device has the function of contracting the bag body 40 from an expanded state. Specifically, the conveying device 64 is provided in the pipe 62. As an example, the conveying device 64 has a pump 66 and a valve 68. The pump 66 is a bidirectional pump, and can be switched between a state in which it operates to transport the hydraulic fluid F from the tank 60 to the bag body 40 and a state in which it operates to transport the hydraulic fluid F from the bag body 40 to the tank 60. The valve 46 operates to adjust the flow rate of the hydraulic fluid F flowing through the pipe 62 and to open and close the internal flow path of the pipe 62. The control unit 70 is configured by a computer having a processor, memory, etc., and is electrically connected to the transport device 64. This control unit 70 has a function of controlling the transport device 64. As shown in FIG. 6, when the heating element HE generates heat, the hydraulic fluid F is transported from the tank 60 to the bag body 40 by the transport device 64. Then, when the heating element HE generates heat while the hydraulic fluid F is transported to the bag body 40, the hydraulic fluid F is heated to generate steam V, and the pressure inside the bag body 40 increases. As a result, the bag body 40 expands from a contracted state and is deployed. When the internal pressure of the bag body 40 decreases and the bag body 40 contracts from the expanded state, the bag body 40 is wound up in a roll and stored. At this time, when the hydraulic fluid F is transported from the bag body 40 to the tank 60 by the transport device 64, the hydraulic fluid F is stored in the tank 60. In this manner, even in the above embodiment, the hydraulic fluid F can be fed in and out between the tank 60 and the bag body 40 by the transport device 64. Here, the control unit 70 may control the transport device 64 so that the amount of hydraulic fluid F supplied to the bag body 40 is adjusted to an appropriate amount according to the temperature of the heating element HE when the heating element HE is generating heat. In this case, the same action and effect as in the above embodiment can be obtained.

In the above embodiment, the bag body is stored in a roll on the core body, but the present disclosure is not limited to this configuration. For example, as shown in FIG. 7, the bag body 40 may be placed on a base, and the bag body 40 placed on the base may be expanded upward. Note that the bag body 40 may be stored, for example, folded.

[Application example]
Next, an example to which the technology of the present disclosure can be applied will be described.

As shown in FIG. 8, the radiative cooling device 20 in the above-mentioned embodiment may be used, for example, as a radiator for an outdoor unit serving as a heating element HE installed on the roof of a building 80. That is, the radiative cooling device 20 functions as a radiator for the outdoor unit by connecting the core body 30 to the heating element HE, which is the outdoor unit. This allows the heat of the outdoor unit to be released as electromagnetic waves EW from the radiative cooling section 44. The building 80 is, for example, a building or a factory. According to this application example, the outdoor unit, which requires a large output, can be efficiently cooled. In addition, since the performance of the outdoor unit increases as the ambient temperature decreases, the use of the radiative cooling device 20 is expected to further improve the performance of the outdoor unit. Note that the above application example of the present disclosure is just one example.

The above describes one embodiment of the technology disclosed in this application, but the technology disclosed in this application is not limited to the above, and can of course be implemented in various modifications within the scope of the gist of the technology.

The following is further disclosed regarding the above embodiment.

(Appendix 1)
A bag body having a radiative cooling part having thermal radiation properties and capable of expanding and contracting;
A heating element disposed inside the bag;
A working fluid that is sealed inside the bag and transports heat from the heating element to the radiative cooling unit by undergoing a phase change;
Equipped with
A radiative cooling device, wherein the heating element is disposed in a portion of the expanded bag where the working fluid in liquid phase is accumulated.

(Appendix 2)
The heating element is a heat exchanger having a flow path through which a heat medium flows,
2. The radiative cooling device of claim 1, wherein the bag body is provided with a circulation path for circulating the heat medium from the outside of the bag body to the heat exchanger inside the bag body.

(Appendix 3)
3. The radiative cooling apparatus of claim 1 or 2, wherein the heating element is fixed to an inner surface of the bag.

(Appendix 4)
The rotor has a core body that is rotatable around an axis and to which a rotational moment is applied,
The bag body is stored in a roll around the core body and expands when the internal pressure increases.
The radiative cooling device according to any one of claims 1 to 3.

(Appendix 5)
5. The radiative cooling device of claim 4, further comprising a guide member arranged at a distance from the axis of the core body and in contact with the bag body to suppress rotation of the bag body around the core body.

(Appendix 6)
6. The radiative cooling device of claim 5, wherein the length of the heating element is 1.5 times or less than the diameter of the core body when viewed in a cross section perpendicular to the rotation axis of the core body.

(Appendix 7)
7. The radiative cooling device of claim 5, wherein the heating element has a curved portion that curves along an outer periphery of the core body.

(Appendix 8)
8. The radiative cooling device of any one of claims 4 to 7, wherein the heating element is made of a flexible material.

(Appendix 9)
The radiative cooling device according to any one of appendix 5 to appendix 7, wherein a support member for supporting the bag body is arranged on the opposite side of the guide member with the bag body sandwiched therebetween.

20 Radiation cooling device 30 Core body 40 Bag body 44 Radiation cooling part 50 Guide member 52 Support member HE Heating element F Working fluid

Claims (9)

A bag body having a radiative cooling part having thermal radiation properties and capable of expanding and contracting;
A heating element disposed inside the bag;
A working fluid is sealed inside the bag and transports heat from the heating element to the radiative cooling unit by undergoing a phase change;
A radiative cooling device, wherein the heating element is disposed in a portion of the bag body in an expanded state where the working fluid in liquid phase accumulates. The heating element is a heat exchanger having a flow path through which a heat medium flows,
The radiative cooling device according to claim 1, wherein the bag body is provided with a circulation path for circulating the heat medium from the outside of the bag body to the heat exchanger inside the bag body. The radiative cooling device of claim 1, wherein the heating element is fixed to the inner surface of the bag body. The rotor has a core body that is rotatable around an axis and to which a rotational moment is applied,
The bag body is stored in a roll around the core body and expands when the internal pressure increases.
10. The radiative cooling device of claim 1. The radiative cooling device according to claim 4, further comprising a guide member arranged at a distance from the axis of the core body and contacting the bag body to suppress rotation of the bag body around the core body. The radiative cooling device of claim 5, wherein the length of the heating element is 1.5 times or less than the diameter of the core body when viewed in a cross section perpendicular to the rotation axis of the core body. The radiative cooling device according to claim 5, wherein the heating element has a curved portion that curves along the outer periphery of the core body. The radiative cooling device of claim 4, wherein the heating element is made of a flexible material. The radiative cooling device according to claim 5 , wherein a support member for supporting the bag body is arranged on the opposite side of the guide member across the bag body.