A cooling panel system

Abstract

A cooling panel system (1) comprising a first cooling panel (10), the first cooling panel (10) comprising: at least one microchannel unit (12), each microchannel unit (12) comprising plurality of microchannels (14) extending in a longitudinal direction (L) of the microchannel unit (12), for transporting a fluid cooling medium, and a layer of heat-emitting material (26) having a thermal emissivity of at least 0,83 and a solar reflectivity of at least 0,9 arranged on a surface (28) of the at least one microchannel unit (12), said surface (28) being configured to be an upper sky-facing surface during operation of the cooling panel system (1), the cooling panel system (1) further comprising: a feeding pipe (16) extending along a first longitudinal end (18) of the at least one first microchannel unit (12), which feeding pipe (16) is connected to each microchannel (14) for supplying the cooling medium thereto, and a discharge pipe (20) extending along a second longitudinal end (22) of the at least one microchannel unit (12), which discharge pipe (20) is connected to each microchannel (14) and arranged to recirculate the cooling medium from the microchannel unit (12) to a heat exchanger.

Description

Field of the Invention

[0001] The present disclosure relates to a cooling panel system. In particular, the disclosure relates to a cooling panel system comprising a plurality of microchannels and a heat emitting material.Background of the Invention

[0002] Cooling of buildings typically includes circulation of a cooling medium through an evaporator unit for removing heat and humidity from the air, and through a condensing unit from which heat is released to the outside of the building. A compressor is used to move the refrigerant, and fans provide an airstream over the evaporator and the condenser for moving the air. The process may be energy demanding.

[0003] By utilizing passive cooling strategies in the cooling system, energy may be saved, as these do not require any electrical input.

[0004] An atmospheric window refers to a specific portion of the electromagnetic spectrum that can travel through the Earth's atmosphere without significant absorption or scattering. The window allow electromagnetic radiation of particular wavelengths to reach the Earth's surface from space and may, vice versa, be used to passively eject heat from earth to space through radiative cooling.

[0005] While solutions for passive radiative cooling in buildings are known, there is a need for an improved solution with regards to energy efficiency and assembly.Summary

[0006] In view of the above, an object of the present disclosure is to provide an enhanced cooling panel system. Another object is to provide such a system which provides a more effective heat transfer from a cooling medium to the sky than previously known systems. A further object is to provide such a cooling system which allows for improved assembly and disassembly, whereby the installation cost and complexity may be reduced. A further object is to provide a modular cooling panel system which may be adapted to different needs.

[0007] According to a first aspect of the present disclosure, a cooling panel system comprising a first cooling panel is provided, the first cooling panel comprising: at least one microchannel unit, each microchannel unit comprising plurality of microchannels extending in a longitudinal direction of the microchannel unit, for transporting a fluid cooling medium, and a layer of heat-emitting material having a thermal emissivity of at least 0,83 and a solar reflectivity of at least 0,9 arranged on a surface of the at least one microchannel unit, said surface being configured to be an upper sky-facing surface during operation of the cooling panel system, the cooling panel system further comprising: a feeding pipe extending along a first longitudinal end of the at least one first microchannel unit, which feeding pipe is connected to each microchannel for supplying the cooling medium thereto, and a discharge pipe extending along a second longitudinal end of the at least one microchannel unit, which discharge pipe is connected to each microchannel and arranged to recirculate the cooling medium from the microchannel unit to a heat exchanger.

[0008] The solution builds on the realization that by providing cooling panels comprising microchannel units, and by arranging a heat emitting material on their sky-facing surface, efficient cooling with low energy consumption may be provided.

[0009] By providing the heat-emitting material with a thermal emissivity of at least 0,83 and a solar reflectivity of at least 0,9, the heat may be emitted in the wavelength range from 8 to 13 µm, thus allowing it to be emitted through the atmospheric window. The heat emitting material thus emits heat to space using the atmospheric window, while also reflecting sunlight. The combination of high thermal emissivity and solar reflectivity even allows for that the cooling medium, during passage through the cooling panel, may be brought down to temperatures well below the temperature of the ambient air. Such sub-ambient heat transfer is not achievable by the use of conventional cooling panels. The enhanced heat transfer may further be accomplished both during night and day. Hence, the cooling panel system according to the present disclosure greatly enhances the cooling effect as compared to conventional cooling panel systems exhibiting lower emissivity and solar reflectivity.

[0010] The cooling effect is further enhanced due to the microchannels of the microchannel units providing a high surface-area to volume ratio between the fluid cooling medium and the microchannels. Thus, heat may be efficiently transferred away from the cooling panel via the walls of the microchannels, and the heat emitting material.

[0011] According to one embodiment, the first cooling panel comprises 200-400 microchannels per meter along a transverse direction. The microchannels may have an inner width or diameter of 0,25-0,5 cm.

[0012] Hereby, good heat transfer may be ensured while still allowing sufficient flow of the fluid cooling medium.

[0013] According to one embodiment, the first cooling panel comprises at least two microchannel units.

[0014] By forming the cooling panel from a plurality of microchannel units, such as at least two microchannel units, the size of the cooling panel may be varied using the same basic component, whereby a modular system may be provided.

[0015] Furthermore, by allowing each microchannel unit to comprise a lower number of microchannels, production may be facilitated.

[0016] The smaller size of each microchannel unit may further facilitate transportation as well as assembly of the system.

[0017] It should be understood that, in other embodiments, the cooling panel may comprise one single microchannel unit.

[0018] According to one embodiment, the at least two microchannel units are connected to a common feeding pipe.

[0019] Hereby, by using the same feeding pipe for a plurality of microchannel units, the number of components of the system may be reduced. Furthermore, the feeding pipe may be used in connecting the microchannel units to each other, which may decrease the number of components of the system.

[0020] According to one embodiment, the at least two microchannel units are connected to a common discharge pipe.

[0021] Hereby, by using the same discharge pipe for a plurality of microchannel units, the number of components of the system may be reduced. Furthermore, the discharge pipe may be used as one means of connecting the microchannel units to each other in forming a cooling panel.

[0022] According to one embodiment, the feeding pipe comprises at least one slot for fluid connection of the at least one microchannel unit to the feeding pipe, the number of slots corresponding to the number of microchannel units.

[0023] The slot may thus both provide for fluid and mechanical connection between the microchannel unit and the feeding pipe.

[0024] Hereby, the assembly of the cooling panel may be facilitated as the microchannel units may be held in place within the slots prior to further fixation, such as by soldering.

[0025] According to one embodiment, the discharge pipe comprises at least one slot for fluid connection of the at least one microchannel unit to the discharge pipe, the number of slots corresponding to the number of microchannel units.

[0026] Hereby, the assembly of the cooling panel may be facilitated as the microchannel units may be held in place within the slots prior to further fixation, such as by soldering.

[0027] According to one embodiment, the feeding pipe and the discharge pipe have the same design.

[0028] Hereby, since the same components may be used for both the feeding pipe and the discharge pipe, a modular system may be provided.

[0029] According to one embodiment, the heat-emitting material is a heat emitting film configured to emit heat to space through the atmospheric window.

[0030] Hereby, heat may be efficiently emitted from the cooling panel system, both during daytime and nighttime.

[0031] According to one embodiment, the heat-emitting material has a thermal emissivity of at least 0,89 and a solar reflectivity of at least 0,92.

[0032] According to one embodiment, wherein the first cooling panel is arranged at an angle to a horizontal plane, such as at an angle of 8-12° degrees.

[0033] Hereby, the accumulation of water and particles on the cooling panel surface may be reduced or prevented.

[0034] According to one embodiment, the cooling panel system further comprises a second cooling panel having at least one microchannel unit, the second cooling panel being arranged beside the first cooling panel such that the longitudinal extension of the at least one microchannel unit of the second cooling panel is parallel to the longitudinal extension of the at least one microchannel unit of the first cooling panel.

[0035] Hereby, a modular system may be provided in which any number of cooling panels may be arranged next to each other such as to increase the effect of the passive cooling. The system may thus be adapted to the available space and / or cooling needs.

[0036] Furthermore, transportation and assembly may be facilitated due to the size of the parts of the system being adaptable.

[0037] According to one embodiment, the second cooling panel is arranged to receive the cooling medium from a feeding pipe being coaxial with the feeding pipe arranged at the first cooling panel.

[0038] Hereby, a system with lower complexity and a lower number of different components may be provided as there is no need for e.g. elbow pipes between two adjacent cooling panels.

[0039] Furthermore, a space efficient solution may be provided in which the efficiency of the system may be increased due to reduced number of bends and connections. The reduced number of bends reduces the system pressure drop for the circulated liquid and hence creates a system with better efficiency.

[0040] According to one embodiment, the second cooling panel is arranged to discharge the cooling medium to a discharge pipe being coaxial with, the discharge pipe arranged at the first cooling panel.

[0041] Hereby, a system with lower complexity and a lower number of different components may be provided as there is no need for e.g. elbow pipes between two adjacent cooling panels.Brief Description of the Drawings

[0042] These and other aspects of the present inventive concept will now be described in more detail, with reference to the appended drawings showing an example embodiment of the inventive concept, wherein: Fig. 1 is a schematical perspective view of a cooling panel system. Fig. 2 is a schematical perspective view of a cooling panel of the cooling panel system. Fig. 3 is a schematic perspective view of a part of the cooling panel illustrating the connection between the microchannel units and the feeding pipe. Fig. 4 is a schematic perspective view of the connection between a pair of cooling panels. Detailed Description of Example Embodiments

[0043] In the present detailed description, various embodiments of the invention are described.

[0044] Fig. 1 is a schematical perspective view of a cooling panel system 1. The cooling panel system 1 is typically mounted on the roof of a building to provide a passive cooling solution for said building.

[0045] The cooling panel system 1 comprises at least one cooling panel 10. In Fig. 1, a cooling panel system 1 comprising thirty-two cooling panels is illustrated. The cooling panels 10 are arranged in eight rows, each row having four cooling panels 10 arranged side by side.

[0046] Straight feeding pipes 16 and discharge pipes 20 connect all cooling panels 10 of a row. The feeding pipes 16 and discharge pipes 20 are in turn connected to a heat exchange circuit (not shown) in which the fluid cooling medium, after having emitted heat in the cooling panel system 1, is used in the cooling of the building on which the cooling panel system 1 is arranged.

[0047] By being divided into several cooling panels, the cooling panel system 1 allows for a modular solution in which the number of cooling panels could easily be adapted to the available space and cooling needs. The modularity is further enhanced by the fact that the pipes of the system are preferably of the same design regardless of their use within the system (e.g. for feeding or discharge).

[0048] Fig. 2 illustrates a cooling panel 10 of the cooling panel system 1. The cooling panel 10 comprises at least one microchannel unit 12. The cooling panel is supported at an angle α relative to a horizontal plane, such that accumulation of water and particles on the cooling panel surface may be reduced or prevented. The angle α may be 8-12°, such as 10°.

[0049] In Fig. 2, each cooling panel 10 comprises ten microchannel units 12. However, in other embodiments, each cooling panel 10 may comprise a lower or higher number of microchannel units 12, such as one single microchannel unit 12.

[0050] Each microchannel unit 12 comprises a plurality of microchannels 14 extending in a longitudinal direction L of the microchannel unit 12 between a first longitudinal end 18 and a second longitudinal end 22.

[0051] The microchannel units 12 are preferably made of extruded aluminum profiles. The microchannels 14 are thus formed during the extrusion of the microchannel units 12. The microchannels units 12 may have a rounded rectangular cross-sectional shape. The cross-sectional shape of the microchannels 14 may for example be rectangular, square or circular.

[0052] The microchannel units 12 are configured for transportation of a fluid cooling medium in the longitudinal direction L. The microchannels 14 are illustrated as thin dashed lines (as better seen in Fig. 3), since they are enclosed within the microchannel unit 12. While the microchannels 14 are only illustrated on the lowermost microchannel unit 12 in Fig. 2, it is understood that also the remaining microchannel units 12 comprise corresponding microchannels 14.

[0053] The plurality of microchannels 14 of a microchannel unit 12 extends in parallel to each other. When the cooling panel 10 comprises several microchannel units 12, the microchannels 14 of a first microchannel unit 12 extends in parallel to the microchannels 14 of the further microchannel units 12. Furthermore, when the cooling system 1 comprises a plurality of cooling panels 10 arranged beside each other, such as the cooling panels of one of the rows of the cooling system in Fig. 1, the microchannels 14 of all cooling panels 10 of to the same row extends essentially in parallel to each other.

[0054] The microchannel unit(s) 12 may comprise 200-400 microchannels 14 per meter, such as 250-290 microchannel units per meter, along a transverse direction T. The transverse direction T being perpendicular to the longitudinal direction L.

[0055] A feeding pipe 16 is extends along the first longitudinal end 18 of the at least one microchannel unit 12. The feeding pipe 16 thus extends in a direction which is essentially perpendicular to the longitudinal direction L. In other words, the feeding pipe 16 extends in the transverse direction T. The feeding pipe 16 is connected to each microchannel 14 to provide the fluid coolant medium thereto, as will be further explained in relation to Fig. 3.

[0056] A discharge pipe 20 is arranged at the second longitudinal end 22 of the at least one microchannel unit 14. The discharge pipe 20 thus extends in a direction being essentially perpendicular to the longitudinal direction L. In other words, the feeding pipe extends in the transverse direction T. The discharge pipe 20 is configured to collect and recirculate the cooled fluid cooling medium leaving the microchannels 14 and circulate it via the heat exchanger in order to cool the building.

[0057] The feeding and / or discharge pipes 16, 20 may comprise aluminum pipes. The pipes may have a diameter of 20-60 mm, such as 25-27 mm.

[0058] The feeding pipes 16 and the discharge pipes 20 may be of the same design, whereby a modular system may be provided since the same pipe can be used either as a feeding pipe 16 or a discharge pipe 20.

[0059] A heat emitting material 26 is arranged on a surface 28 of the at least one microchannel unit 14. The surface 28, is an upper surface of the microchannel unit 14. In other words, the surface 28 is a sky-facing surface. The heat emitting material 26 has a thermal emissivity of at least 0,83 and a solar reflectivity of at least 0,9. The heat emitting material 26 allows passive radiation of heat to space by emitting heat in the wavelength of 8 to 13 µm, allowing the heat to pass through the atmospheric window.

[0060] The heat emitting material 26 may be arranged on the microchannel units 12 in the form of a film, such as an adhesive film. To increase the durability of the film and lower the accumulation of particles on its surface, the film may be provided with a hard coat.

[0061] An insulation plate (not shown in the figures) may further be provided. The insulation plate may be arranged at a lower surface of the microchannel unit(s) 12. The isolation plate may thus provide structural support to the microchannel unit(s) 12 and, when the cooling plate 10 comprises a plurality of microchannel units 12, contributing to connecting the microchannel units 12 to each other.

[0062] The insulation plate may be formed by a sandwich material comprising a XPS Foam layer sandwiched between first and second glass fiber layers. For example, the XPS Foam layer may have a thickness of 20-38 mm, such as 26 mm, and the glass fiber layers may each have a thickness of 1- 5 mm, such as 2 mm.

[0063] The insulation plate may be attached to the microchannel unit(s) 12 by tape. Preferably, the tape is provided as strips running along the longitudinal direction L of the microchannel units 12. A distance may be provided between the strips of tape to prevent condensate water from being trapped between the microchannel units 12 and the insulation plate.

[0064] A frame 30 may further be arranged around the microchannel unit(s) 12 forming the cooling panel 10. The frame 30 may comprise four side frame parts 30a-d arranged along each side of the cooling panel 10.

[0065] Furthermore, the frame 30 may comprise one or more cross-beams 30e extending below the microchannel units 12 in addition to, or instead of, the insulation plate. The frame 30 may comprise or consist of aluminum. Alternatively, the frame 30 may comprise or consist of stainless steel.

[0066] The frame 30 may in turn be connected to a support structure for mounting of the cooling panel 10 to the building at a desired angle.

[0067] Fig. 3 shows the connection between the microchannel units 12 and the feeding pipe 16.

[0068] The feeding pipe 16 in Fig. 3 comprise a plurality of elongated slots 24. Each slot 24 is configured to receive an end portion of one microchannel unit 12. Once the end portion of the microchannel unit 12 has been inserted into the slot 24, the microchannel units 12 may be attached to the feeding pipe 16 through soldering or welding, such as laser welding. The distance between a pair of adjacent microchannel units 12 may be 1-5 mm, such as 2 mm to provide enough space for the solder or weld.

[0069] In the same way, the discharge pipe 20 may comprise slots configured to receive second, opposite, end portions of the microchannel units 12.

[0070] Fig. 4 shows a connection between a pair of cooling panels 10. As shown in Fig. 4, when the cooling panel system 1 comprises at least two cooling panels 10 arranged beside each other, the feeding and / or discharge pipe 16, 20 of a first cooling panel 10 may be connected to the feeding and / or discharge pipe 16, 20 of an adjacent cooling panel by a connector 32.

[0071] The connector 32 may be a clamped connector fixated by one or more screws or bolts. As the screws or bolts are loosened, the connector 32 may be configured to be translated along the feeding pipes 16 of the first and second cooling panel 10. Thus, by providing a sufficient distance between the adjacent cooling panels 10 for allowing translation of the connector 32 to the side, a simple way of separating the cooling panels 10 from each other may be provided. A cooling panel 10 may thus be easily connected to, or disconnected from, the cooling panel system 1 by loosening the connector and pushing it away from the cooling panel to be disassembled. Thereafter, the cooling panel 10 may be lifted straight up for removal or replacement.

[0072] Even though the solution has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art.

[0073] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A cooling panel system (1) comprising a first cooling panel (10), the first cooling panel (10) comprising: at least one microchannel unit (12), each microchannel unit (12) comprising plurality of microchannels (14) extending in a longitudinal direction (L) of the microchannel unit (12), for transporting a fluid cooling medium, and a layer of heat-emitting material (26) having a thermal emissivity of at least 0,83 and a solar reflectivity of at least 0,9 arranged on a surface (28) of the at least one microchannel unit (12), said surface (28) being configured to be an upper sky-facing surface during operation of the cooling panel system (1), the cooling panel system (1) further comprising: a feeding pipe (16) extending along a first longitudinal end (18) of the at least one first microchannel unit (12), which feeding pipe (16) is connected to each microchannel (14) for supplying the cooling medium thereto, and a discharge pipe (20) extending along a second longitudinal end (22) of the at least one microchannel unit (12), which discharge pipe (20) is connected to each microchannel (14) and arranged to recirculate the cooling medium from the microchannel unit (12) to a heat exchanger.

2. The cooling panel system according to claim 1, wherein the first cooling panel comprises 200-400 microchannels per meter along a transverse direction.

3. The cooling panel system (1) according to claim 1, wherein the at least one microchannel unit (12) comprises, or consists of, extruded aluminum.

4. The cooling panel system (1) according to claim 1, wherein the first cooling panel (10) comprises at least two microchannel units (12).

5. The cooling panel system (1) according to claim 4, wherein the at least two microchannel units (12) are connected to a common feeding pipe (16).

6. The cooling panel system (1) according to claim 4, wherein the at least two microchannel units (12) are connected to a common discharge pipe (20).

7. The cooling panel system (1) according to claim 1, wherein the feeding pipe (16) comprises at least one slot (24) for fluid connection of the at least one microchannel unit (12) to the feeding pipe (16), the number of slots (24) corresponding to the number of microchannel units (12).

8. The cooling panel system (1) according to claim 1, wherein the discharge pipe (20) comprises at least one slot for fluid connection of the at least one microchannel unit to the discharge pipe (20), the number of slots corresponding to the number of microchannel units (12).

9. The cooling panel system (1) according to claims 7 and 8, wherein the feeding pipe (16) and the discharge pipe (20) have the same design.

10. The cooling panel system (1) according to claim 1, wherein the heat-emitting material (26) has a thermal emissivity of at least 0,89 and a solar reflectivity of at least 0,92.

11. The cooling panel system (1) according to claim 1, wherein the first cooling panel (10) is arranged at an angle (α) to a horizontal plane, such as at an angle (α) of 8-12° degrees.

12. The cooling panel system (1) according to claim 1 further comprising a second cooling panel having at least one microchannel unit (12), the second cooling panel being arranged beside the first cooling panel (10) such that the longitudinal extension of the at least one microchannel unit (12) of the second cooling panel is parallel to the longitudinal extension of the at least one microchannel unit (12) of the first cooling panel (10).

13. The cooling panel system according to claim 13, wherein the second cooling panel is arranged to receive the cooling medium from a feeding pipe being coaxial with, the feeding pipe (16) arranged at the first cooling panel (10).

14. The cooling panel system (1) according to claim 13, wherein the second cooling panel (10) is arranged to discharge the cooling medium to a discharge pipe being coaxial with, the discharge pipe (20) arranged at the first cooling panel (10).

Images