MU JUNWEI (CN)
YANG GUO (CN)
FILATAU SVIATASLAU ALEHAVICH (CN)
| US20040069460A1 | 2004-04-15 | |||
| JP2007150013A | 2007-06-14 | |||
| JP2015219639A | 2015-12-07 | |||
| JPH0933181A | 1997-02-07 | |||
| DE102008000415A1 | 2009-08-27 | |||
| US5560423A | 1996-10-01 | |||
| US20080216994A1 | 2008-09-11 | |||
| US20190354148A1 | 2019-11-21 |
| CLAIMS 1. A flat foldable heat pipe (100A, 100B, 400), comprising: a sealed container (102) formed at least partly of flexible sheets (104A,104B, 702A, 702B) jointed at peripheral portions; a spacer (106, 202A, 202B, 202C, 204 A, 204B, 204C, 206A, 206B, 208 A, 208B, 208C, 210, 300A, 300B, 300C, 300D) housed in the container (102), the spacer (106, 202A, 202B, 202C, 204 A, 204B, 204C, 206A, 206B, 208A, 208B, 208C, 210, 300A, 300B, 300C, 300D) having walls defining channels (110) and exerting a capillary force; and a working fluid (108A, 108B) enclosed in the container (102), wherein one or more walls of the spacer (106, 202 A, 202B, 202C, 204 A, 204B, 204C, 206 A, 206B, 208A, 208B, 208C, 210, 300A, 300B, 300C, 300D) have a non-uniform thickness in a cross section and define additional channels (112) between surfaces of the walls facing the flexible sheets (104A,104B, 702A, 702B) and the flexible sheets (104A,104B, 702A, 702B). 2. The flat foldable heat pipe (100A, 100B, 400) of claim 1, wherein the channels (110) are suitable for transporting the working fluid ( 108 A) in a vapor state and the additional channels (112) are suitable for transporting the working fluid (108B) in a liquid state. 3. The flat foldable heat pipe (100A, 100B, 400) of claim 1 or 2, wherein the spacer (106, 202A, 202B, 202C, 204A, 204B, 204C, 206A, 206B, 208A, 208B, 208C, 210, 300A, 300B, 300C, 300D) is made in one piece with one of the flexible sheets (104A,104B, 702A, 702B). 4. The flat foldable heat pipe (100A, 100B, 400) of any of claims 1 to 3, wherein the one or more walls of the spacer (106, 202A, 202B, 202C, 204A, 204B, 204C, 206A, 206B, 208A, 208B, 208C, 210, 300A, 300B, 300C, 300D) with non-regular thickness are provided with longitudinal grooves defining the additional channels (112). 5. The flat foldable heat pipe (100A, 100B, 400) of claim 4, wherein the longitudinal grooves are provided with irregularities and/or protruding elements, the irregularities and/or protruding elements forming a capillary structure. 6. The flat foldable heat pipe (100A, 100B, 400) of claim 4, wherein the longitudinal grooves are provided with porous coating forming a capillary structure. 7. The flat foldable heat pipe (100A, 100B, 400) of any of claims 4 to 6, wherein the longitudinal grooves are provided with through holes. 8. The flat foldable heat pipe (100A, 100B, 400) of any of claims 1 to 7, further comprising porous sheets (402A, 402B, 602A, 602B, 606, 610) housed in the container (102) that sandwich the spacer (106, 202A, 202B, 202C, 204A, 204B, 204C, 206A, 206B, 208A, 208B, 208C, 210, 300 A, 300B, 300C, 300D). 9. The flat foldable heat pipe (100A, 100B, 400) of claim 8, wherein the porous sheets (402 A, 402B, 602 A, 602B, 606, 610) exert a capillary force for transporting the working fluid (108A, 108B). 10. The flat foldable heat pipe (100A, 100B, 400) of claim 8 or 9, wherein the porous sheets (402 A, 402B, 602 A, 602B, 606, 610) are more flexible in a direction along the channels (110) than in a direction across the channels (110). 11. The flat foldable heat pipe (100A, 100B, 400) of claim 10, wherein the porous sheets (402A, 402B, 602A, 602B, 606, 610) comprise a mesh made of first wires (502 A) extending in a direction along the channels (110) and second wires (502B) extending in a direction across the channels (110), the first wires (502 A) having a smaller diameter than the second wires (502B). 12. The flat foldable heat pipe (100A, 100B, 400) of claim 10 or 11, wherein the porous sheets (402 A, 402B, 602A, 602B, 606, 610) comprise a mesh made of first wires (502A) extending in the direction along the channels (110) and second wires (502B) extending in the direction across the channels (110), wherein each of the second wires (502B) is arranged essentially along a straight line. 13. The flat foldable heat pipe (100A, 100B, 400) of claim 10, wherein the porous sheets (402 A, 402B, 602A, 602B, 606, 610) comprise one or more of through holes (604A, 604B), grooves, and ribs (608), that extend in the direction across the channels (110). 14. The flat foldable heat pipe (100A, 100B, 400) of any of claims 10 to 13, wherein the porous sheets (402A, 402B, 602A, 602B, 606, 610) have weakened areas (612) that align with the additional channels (112). 15. The flat foldable heat pipe (100A, 100B, 400) of claim 14, wherein the weakened areas (612) of the porous sheets (402 A, 402B, 602 A, 602B, 606, 610) comprise one or more of grooves, dimples and through holes. 16. The flat foldable heat pipe (100A, 100B, 400) of any of claims 1 to 15, wherein the flexible sheets (104A,104B, 702A, 702B) comprise ribs (704A, 704B) extending in a direction across the channels (110). 17. The flat foldable heat pipe (100A, 100B, 400) of claim 16, wherein the ribs (704A, 704B) on the flexible sheets (104A,104B, 702A, 702B) are arranged with gaps (1000) that align with the additional channels (112). |
TECHNICAL FIELD
The present disclosure relates generally to the field of electronic devices; and more specifically, to flat foldable heat pipe.
BACKGROUND
With the rapid development in electronic device technologies, the demand for cooling systems capable of dissipating heat at high efficiency for the electronic devices is increased. To counter or dissipate the heat generated, the electronic device may include a heat dissipating device, such as a heat pipe. The purpose of the heat pipe is to move the heat from the point of generation to another suitable location for dissipation. The heat pipe is a sealed, usually evacuated chamber which contains a liquid coolant. The liquid coolant or internal fluid changes phase as it absorbs and dissipates heat. The coolant changes from liquid to vapour as heat is transferred to it from heat source in the electronic device, and changes from vapour back to liquid as it dissipates the heat to the surrounding environment.
Depending on overall shape and architecture of an internal space in the electronic device, the heat pipes can operate according to some basic principles or its combinations. For instance, traditional heat pipes have mostly one-dimensional transport of heat, where liquid recirculate through a porous body due to capillary forces. Vapour chambers based heat pipes mostly have two-dimensional transport of heat, with liquid recirculating through the porous body due to capillary forces. Thermo-syphon or loop thermo-syphon-based heat pipes have liquid recirculate through the channels due to gravity forces. Loop heat pipes have liquid recirculate through the channels due to capillary forces. Moreover, in pulsating heat pipes, liquid recirculate (oscillate) in the loop of channels due to capillary forces, expansion of internal fluid during evaporation, and collapsing of internal fluid during condensation. Generally, water is used as an internal fluid of the heat pipe. A pressure of the water inside the heat pipe is generally below atmospheric pressure, so the atmospheric pressure creates uniform mechanical load on an outer surface of the heat pipe. In order to avoid deformation of walls of the heat pipe under such mechanical load, material of walls is metallic (usually copper, aluminium, titanium, steel and the like). High strength of such metallic walls and provide a solution that overcomes at least partially the problems encountered in the prior art, and provide an improved heat pipe having polymeric walls in which wall collapsing of the polymeric walls is decreased without increasing of thickness of the polymeric wall, (or the thickness of the heat pipe or distance between supporting structures in the heat pipes).
The object of the present disclosure is achieved by the solutions provided in the enclosed independent claims. Advantageous implementations of the present disclosure are further defined in the dependent claims.
In one aspect, the present disclosure provides a flat foldable heat pipe, comprising: a sealed container formed at least partly of flexible sheets jointed at peripheral portions; a spacer housed in the container, the spacer having walls defining channels and exerting a capillary force; and a working fluid enclosed in the container, wherein one or more walls of the spacer have a non-uniform thickness in a cross section and define additional channels between surfaces of the walls facing the flexible sheets and the flexible sheets.
The present disclosure provides an improved flat foldable heat pipe which manifest almost no wall collapsing or much lower wall (i.e., flexible sheets) collapsing in comparison to the conventional heat pipes. The wall collapsing of the flat foldable heat pipe of the present disclosure in comparison to conventional heat pipes is decreased without increasing thickness of the flexible sheet (or thickness of the flat foldable heat pipe or a distance between supporting structures of the spacer). The thickness of the spacer of the present disclosure is variable (i.e. thickness of the spacer near channels is larger compared to thickness far from the channel). Due to non-uniform thickness of the spacer, under uniform mechanical load from atmospheric pressure the flexible sheets move in both the channels and the additional channels, as a result deformation of the flexible sheets is spread, and thus deformation above the channels is less compared to deformation of flat foldable heat pipes with conventional shape of spacers with uniform thickness. Thus, non-uniform structure of the spacer and the flexible sheets lead to less deformation of the flexible sheets during vacuuming (and under internal vacuum during operation of flat foldable heat pipe) and an improved flexibility performance during folding of the flat foldable heat pipe. In an implementation form, the channels are suitable for transporting the working fluid in a vapor state and the additional channels are suitable for transporting the working fluid in a liquid state.
As the vapor state of the working fluid is transported through the channels with decreased deformation of flexible sheets, and the liquid state of the working fluid is transported through the additional channels, therefore an internal space of the flat foldable heat pipe is increased, wh i ch further improves the thermal performance of the flat foldable heat pipe.
In a further implementation form, the spacer is made in one piece with one of the flexible sheets.
By virtue of using the spacer in one piece with one of the flexible sheets, strength of the flexible structure is improved.
In a further implementation form, the one or more walls of the spacer with non-regular thickness are provided with longitudinal grooves defining the additional channels.
The additional channels defined by the longitudinal grooves improve the thermal performance of the flat foldable heat pipe due to increased space for flow of liquid form of working liquid (liquid form of working liquid flows along the longitudinal grooves.
In a further implementation form, the longitudinal grooves are provided with irregularities and/or protruding elements, the irregularities and/or protruding elements forming a capillary structure.
The capillary structure is beneficial for transportation of the working fluid with high capillary pressure, and it is also beneficial for low thermal resistance with increased porous heat transfer surface.
In a further implementation form, the longitudinal grooves are provided with porous coatrng forming a capillary structure.
The capillary structure formed due to the porous coating is beneficial for transportation of the working fluid with high capillary pressure, and it is also beneficial for low thermal resistance with increased porous heat transfer surface. In a further implementation form, the longitudinal grooves are provided with through holes.
The through holes of the longitudinal grooves are used for interconnection between grooves, which are formed between the flexible sheets and a space between the spacer.
In a further implementation form, the flat foldable heat pipe further comprises porous sheets housed in the container that sandwich the spacer.
The porous sheets housed in the container are used to hold the flexible sheets. Therefore, when the container is vacuumed, the porous sheets reduce the deformation of the flexible sheets.
In a further implementation form, the porous sheets exert a capillary force for transporting the working fluid.
As, the porous sheets exert the capillary force for transporting the working fluid, therefore, the porous sheets are used as an additional way for transportation of the working fluid in the liquid state in the flat foldable heat pipe.
In a further implementation form, the porous sheets are more flexible in a direction along the channels than in a direction across the channels.
Such irregular flexibility of the porous sheets improves folding of the flat foldable heat pipe and also avoids collapsing of the flexible sheets.
In a further implementation form, the porous sheets comprise a mesh made of first wires extending in a direction along the channels and second wires extending in a direction across the channels, the first wires having a smaller diameter than the second wires.
As the porous sheet comprises a mesh made of the first and the second wires with different diameters, and with irregular flexibility. Therefore, such irregular flexibility of the first and second wires of the mesh improves folding of the flat foldable heat pipe and also avoids collapsing of the flexible sheets at the same time.
In a further implementation form, the porous sheets comprise a mesh made of first wires extending in the direction along the channels and second wires extending in the direction across the channels, wherein each of the second wires is arranged essentially along a straight line. As the second wires of the porous sheets are extending in the direction across the channels, and each of the second wires is arranged essentially along a straight line. Therefore, the folding and flexibility of the flat foldable heat pipe is improved.
In a further implementation form, the porous sheets comprise one or more of through holes, grooves, and ribs, that extend in the direction across the channels.
As one or more through holes, grooves, and ribs, of the porous sheets are extending in the direction across the channels, therefore, the porous sheets are very flexible for deformation along the channels.
In a further implementation form, the porous sheets have weakened areas that align with the additional channels.
As the porous sheets have weakened areas align with the additional channels, therefore, deformation of flexible sheets under uniform mechanical load is spread more in to weakened areas, so the deformation of flexible sheets near non-weakened areas (above the channels) is less.
In a further implementation form, the weakened areas of the porous sheets comprise one or more of grooves, dimples and through holes.
The weakened areas of the porous sheets that align with the additional channels comprises one or more of grooves, dimples and through holes for creation of an anisotropic flexibility of the porous sheets.
In a further implementation form, the flexible sheets comprise ribs extending in a direction across the channels.
As the ribs of the flexible sheets are extending in a direction across the channels, thus the flexible sheets are more flexible towards direction along the channels and less flexible towards direction across the channels. Moreover, the ribs of the flexible sheets avoid the flexible sheets to collapse near the additional channels and under vacuum conditions.
In a further implementation form, the ribs on the flexible sheets are arranged with gaps that align with the additional channels. The gaps between the ribs of the flexible sheets on the area of additional channels lead to redistribution of deformation of the flexible sheets which leads to less deformation of the flexible sheets above the channels.
It is to be appreciated that all the aforementioned implementation forms can be combined. It has to be noted that all devices, elements, circuitry, units and means described in the present application could be implemented in the software or hardware elements or any kind of combination thereof. All steps which are performed by the various entities described in the present application as well as the functionalities described to be performed by the various entities are intended to mean that the respective entity is adapted to or configured to perform the respective steps and functionalities. Even if, in the following description of specific embodiments, a specific functionality or step to be performed by external entities is not reflected in the description of a specific detailed element of that entity which performs that specific step or functionality, it should be clear for a skilled person that these methods and functionalities can be implemented in respective software or hardware elements, or any kind of combination thereof. It will be appreciated that features of the present disclosure are susceptible to being combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
Additional aspects, advantages, features and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative implementations construed in conjunction with the appended claims that follow.
BRIEF DESCRIPTION OF THE DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers. Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
FIG. 1A is a cross-sectional view of a flat foldable heat pipe, in accordance with an embodiment of the present disclosure;
FIG. 1 B is an exploded view of the flat foldable heat pipe, in accordance with an embodiment of the present disclosure;
FIGs. 2A-2L are illustrations of a spacer for the flat foldable heat pipe, in accordance with various embodiment of the present disclosure;
FIGs. 3A, 3B, 3C, and 3D are illustrations of channels of the spacer for the flat foldable heat pipe, in accordance with different embodiments of the present disclosure;
FIG. 4 is an illustration of an exploded view of the flat foldable heat pipe, in accordance with an embodiment of the present disclosure;
FIG. 5 is an illustration of a porous sheet of the flat foldable heat pipe, in accordance with an embodiment of the present disclosure;
FIGs. 6A-6D are illustrations of porous sheets of the flat foldable heat pipe, in accordance with various embodiments of the present disclosure;
FIG. 7 is an illustration of the flat foldable heat pipe, in accordance with another embodiment of the present disclosure;
FIG. 8 is an illustration of a section of the flat foldable heat pipe along the channels, in accordance with an embodiment of the present disclosure;
FIG. 9 is an illustration of a flexible sheet of the flat foldable heat pipe, in accordance with an embodiment of the present disclosure;
FIG. 10 is an illustration of an exploded view of the flat foldable heat pipe, in accordance with an embodiment of the present disclosure;
FIG. 11 is an illustration of the flat foldable heat pipe, in accordance with another embodiment of the present disclosure; and
FIG. 12A-12B are illustrations of cross-sectional view of the flat foldable heat pipe of FIG. 11, in accordance with different embodiments of the present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non- underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION OF EMBODIMENTS
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognize that other embodiments for carrying out or practicing the present disclosure are also possible.
FIG. 1A is a cross-sectional view of a flat foldable heat pipe, in accordance with an embodiment of the present disclosure. With reference to FIG. 1A there is shown a flat foldable heat pipe 100A that comprises a sealed container 102, flexible sheets 104A and 104B, a spacer 106, a working fluid 108A (in a vapour form) and 108B (in a liquid form), channels 110 and additional channels 112. There is further shown sealing 114A and 114B.
The present disclosure provides a flat foldable heat pipe 100A, comprising: a sealed container 102 formed at least partly of flexible sheets 104A and 104B jointed at peripheral portions; a spacer 106 housed in the container 102, the spacer 106 having walls defining channels 110 and exerting a capillary force; and a working fluid 108 A enclosed in the container 102, wherein one or more walls of the spacer 106 have a non-uniform thickness in a cross section and define additional channels 112 between surfaces of the walls facing the flexible sheets 104A and 104B and the flexible sheets 104A and 104B.
The flat foldable heat pipe 100A of the present disclosure is implemented as part of a cooling system of an electronic device. Herein, the electronic device may be any electronic device which may be foldable, including a laptop, a mobile phone, a computer, a tablet, a camera and the like. In such electronic device, some heat generation components such as an arithmetic element and an integrated circuit are built in a highly dense manner, a heat spot in which a temperature increases locally occurs, and the temperature becomes a cause of limiting arithmetic operation speed, a cause of reducing durability, or the like. The flat foldable heat pipe 100A of the present disclosure as part of the cooling system for the electronic device provides means for heat releasing and cooling in the electronic device. The sealed container 102 is formed at least partly of flexible sheets 104A and 104B, jointed at peripheral portions. The sealed container 102 is configured to transfer heat due to combination of processes of evaporation and condensation. In an example the sealed container 102 (or simply referred to as the container 102) have a pipe-like shape or any other shape suitable for heat transfer in foldable electronic devices.
The flexible sheets 104A and 104B are the outer surfaces of the flat foldable heat pipe 100A. In an example, the flexible sheets 104A and 104B may have micro-patterns arranged on an inner surface and (or) on an outside surface. The flexible sheets 104A and 104B corresponds to flexible walls, for example thin polymeric walls made of one or more polymers (e.g., polyethylene terephthalate) which are used to form the sealed container 102 of the flat foldable heat pipe 100A.
The spacer 106 may also be referred to as a flexible spacer, a flexible film, a flexible plate with parallel channels (i.e. channels 110) of variable thickness and a non-uniform (or nonregular) structure. In an example, the direction of the parallel channels (i.e. channels 110) of the spacer 106 is selected based on layout of application as well as operational principle of the flat foldable heat pipe 100A. In an example, material of the spacer 106 is polyethylene terephthalate. The spacer 106 may include supporting structures for example in shape of dumbbells.
The working fluid 108A and 108B is used for dissipation of heat generated in a given electronic device by evaporation and condensation of the working fluid 108 A and 108B. The working fluid 108 A and 108B may realize different principles of operations such as loop thermo-syphon, loop heat pipe, thermo-syphon, pulsating heat pipe for dissipation of heat generated in the electronic device. The working fluid 108 A and 108B is selected according the physical properties such as very high surface tension, good thermal stability, high latent heat, high thermal conductivity, and low liquid and vapour viscosities. Further, the type of working fluid 108 A and 108B used for the flat foldable heat pipe 100A depends on the operating temperature range of the electronic device. For example, helium is used as the working fluid 108A and 108B for temperature range from -271 °C to -269 °C, methanol is used as the working fluid 108A and 108B for temperature range from 10 °C to 130 °C and water is usually used as the working fluid 108A and 108B for temperature range from 30 °C to 200 °C. Other types of the working fluid 108A and 108B may include, but is not limited to ammonia, acetone, ethanol, mercury and nitrogen.
The channels 110 and the additional channels 112 are also referred to as space suitable for transporting the working fluid 108A and 108B. In an example, the channels 110 may also be referred to as vapour channels, and the additional channels 112 may also be referred as liquid channels.
The sealing 114A and 114B are used to join the peripheral portions of the flexible sheets 104A and 104B so as to form the sealed container 102. The sealing 114 A and 114B are selected according to the physical properties as well as on the operating temperature range of the electronic device. In an example, the sealing 114A and 114B are referred to as a sealable end cap.
The spacer 106 is housed in the container 102. The spacer 106 has walls defining channels 110 and exerting a capillary force, and the working fluid 108A and 108B is enclosed in the container 102. In other words, the spacer 106 is encapsulated within the flexible sheets 104A and 104B of the container 102. The spacer 106 is covered from both sides (e.g., top and bottom sides) by the flexible sheets 104A and 104B, and the uncovered walls of the spacers 106 defines channels 110 within the container 102, as shown in the FIG. 1 A. Moreover, the container 102 is vacuumed (i.e., an internal space of the container 102 is vacuumed) from atmosphere, and the container 102 is filled with (or charged by) the working fluid 108A and 108B. The working fluid 108A and 108B circulate (or recirculate) through the container 102 due to the capillary force (or pressure) exerted by the spacer 106. Thereafter, the flexible sheets 104A and 104B deforms (or undergoes deformation) in a direction perpendicular to the plain of the flat foldable heat pipe 100A. The flexible sheets 104A and 104B moves due to the non-regular thickness of the spacer 106. In an example, the flexible sheets 104A and 104B moves not only in to the channels 110, but also into the grooves, which are formed between the flexible sheets 104A and 104B and a space between the channels 110 of the spacer 106. In other words, due to the non-uniform thickness of the spacer 106, the deformation of the flexible sheets 104A and 104B is partially spread to the grooves between the channels 110 of the spacer 106. The deformation of the flexible sheets 104A and 104B is smaller as compared to the conventional heat pipes, as material of the conventional flexible sheets moves only to the channel region, and not in the grooves due to the uniform thickness of the conventional spacers. Thus, the non-uniform thickness of the spacer 106 results in a smaller deformation of the flexible sheets 104A and 104B as compared to conventional designs.
One or more walls of the spacer 106 have a non-uniform thickness in a cross section and define additional channels 112 between surfaces of the walls facing the flexible sheets 104A and 104B and the flexible sheets 104A and 104B. In other words, one or more walls of the spacer 106 have a non-uniform thickness, such that the thickness of one or more walls of the spacer 106 near the channels 110 is larger as compared to the thickness far away from the channels 110. Alternatively, the thickness of material of the spacer 106 is increased near edge of the channels 110. Moreover, the non-uniform thickness of the one or walls of the spacer 106 results in the formation of the additional channels 112. The additional channels 112 are defined between the surfaces of the walls of the spacer 106 and the flexible sheets 104A and 104B of the container 102, where the walls of the spacer 106 are facing the flexible sheets 104A and 104B. Therefore, in between the flexible sheets 104A and 104B and the spacer 106 two kinds of channels are formed, such as the channels 110 (near the parallel channels of the spacer 106), and the additional channels 112 in between the flexible sheets 104A and 104B and side surfaces of the walls of the spacer 106.
In accordance with an embodiment, the channels 110 are suitable for transporting the working fluid 108A in a vapor state and the additional channels 112 are suitable for transporting the working fluid 108B in a liquid state. During operation of the flat foldable heat pipe 100A, the working fluid 108A and 108B may have two different states, such as a vapor state of the working fluid 108 A, and a liquid state of the working fluid 108B. The vapor state of the working fluid 108A is transported through the channels 110, and the liquid state of the working fluid 108B is transported through the additional channels 112 defined due to the non-uniform thickness of the one or walls of the spacer 106. Further, deformation of the flexible sheets 104A and 104B under vacuum is more uniform, and the flexible sheets 104A and 104B deformation near channels 110 is smaller as compared to the conventional spacer design with uniform shape. Therefore, the channels 110, and the additional channels 112 increases an internal space of the flat foldable heat pipe 100A, which results in better thermal performance due to increased cross section for vapor circulation. In accordance with an embodiment, the spacer 106 is made in one piece with one of the flexible sheets 104A and 104B. As the spacer 106 is made in one piece with one of the flexible sheets 104A and 104B, such as by using same material (e.g., polyethylene terephthalate) for the flexible sheets 104A and 104B and the spacer 106, which results in high strength of the flexible sheets 104A and 104B. In an example, the spacer 106 is made in one piece with one of the flexible sheets 104A and 104B at the time of manufacturing of the flat foldable heat pipe 100A.
In accordance with an embodiment, the one or more walls of the spacer 106 with non-regular thickness are provided with longitudinal grooves defining the additional channels 112. In an example, one or more walls of the spacer 106 have non-regular thickness (or non- regularities) either on both sides of spacer 106, or only on one side of the spacer 106. If in a case, the spacer 106 has non-regular thickness on one side only, then the longitudinal grooves are provided on one side of the spacer 106, therefore the additional channels 112 are defined on one side of the spacer 106 for transportation of the liquid state of the working fluid 108B. In another example, the spacer 106 has non-regular thickness on both sides, then the longitudinal grooves are provided on both sides of the spacer 106, and the additional channels 112 are defined on both sides of the spacer 106 for transportation of the liquid state of the working fluid 108B. The additional channels 112 increases the internal space of the flat foldable heat pipe 100A, and also improve the thermal performance of the spacer 106.
In accordance with an embodiment, the longitudinal grooves are provided with irregularities and/or protruding elements, the irregularities and/or protruding elements forming a capillary structure. In other words, due to the irregularities and (or) protruding elements of the longitudinal grooves, the spacer 106 have micro-patterns on an area of the longitudinal grooves, which results in the formation of the capillary structure on both sides of the spacer 106. The capillary structure is beneficial for transportation of the working fluid 108A and 108B with high capillary pressure.
In accordance with an embodiment, the longitudinal grooves are provided with porous coating forming a capillary structure. In other words, the spacer 106 have porous coating on the surface, which results in the formation of the capillary structure, and further used for transportation of the liquid state of the working fluid 108B with high capillary pressure. In accordance with an embodiment, the longitudinal grooves are provided with through holes. Alternatively stated, the longitudinal grooves of the spacer 106 have through holes (or additional through holes). The through holes of the longitudinal grooves are used for interconnection between the longitudinal grooves, which are formed between the flexible sheets 104A and 104B and a space between the spacer 106.
In accordance with an embodiment, the flat foldable heat pipe 100A further comprising porous sheets housed in the container 102 that sandwich the spacer 106. In other words, the porous sheets (or thin porous sheets) with a porosity are placed between the spacer 106 and the flexible sheets 104A and 104B of the container 102. In an example, the porous sheets correspond to a mesh with different diameters of wires, where thick wires of the mesh are placed across the channels 110, and thin wires of the mesh are placed along the channels 110. In another example, the porous sheets correspond to a sheet with long narrow holes which are arranged perpendicular to the channels 110 from the spacer 106. In another example, the porous sheets correspond to a sheet with ribs or grooves, which are arranged perpendicular to the channels 110 from the spacer 106. In a yet another example, the porous sheets correspond a porous material with holes, which are arranged in such way, that the porous sheet is more flexible in the direction along the channels 110 and less flexible in the direction across the channels 110. The porous sheets housed in the container 102 are used to hold the flexible sheets 104A and 104B. Therefore, when the container 102 is vacuumed, the porous sheets reduces the deformation of the flexible sheets 104A and 104B.
In accordance with an embodiment, the porous sheets exert a capillary force for transporting the working fluid 108A and 108B. The porous sheets are used as an additional way for transportation of the working fluid 108B in the liquid form in the flat foldable heat pipe 100A, such as by creation of a capillary force (or pressure), which acts as a driving force to circulate (or re-circulate) the working fluid 108B in the liquid form through the porous sheets of the flat foldable heat pipe 100A.
In accordance with an embodiment, the porous sheets are more flexible in a direction along the channels 110 than in a direction across the channels. In an example, the porosity of the porous sheet is formed by holes, protrusions (or patterns), which are arranged in such a way that the porous sheet is softer during bending towards direction along the channels 110 as compared to the bending towards direction across the channels 110 (e.g., the vapour channel). Therefore, the structure of the porous sheet is more flexible during folding the flat foldable heat pipe 100A in the direction along the channels 110. Moreover, the porous sheet is used to hold the flexible sheets 104A and 104B, because deformation of the flexible sheets 104A and 104B during vacuum state goes in opposite direction as compared to the folding of the flat foldable heat pipe 100A. Such irregular flexibility of the porous sheets improves folding of the flat foldable heat pipe 100A and also avoids collapsing of the flexible sheets 104A and 104B.
In accordance with an embodiment, the porous sheets comprise a mesh made of first wires extending in a direction along the channels 110 and second wires extending in a direction across the channels 110, the first wires having a smaller diameter than the second wires. In other words, the porous sheets comprise a non-regular mesh made of the first and the second wires with different diameters, and with irregular flexibility. The second wires are thicker as compared to the first wires. Moreover, the first wires (or thin wires) are very soft and extended (or arranged) along the channels 110, which avoids destruction during folding the flat foldable heat pipe 100A. In an example, the second wires (or thick wires) have high strength and are extended across the channels 110 so as to avoid deformation of the flexible sheets 104A and 104B. Therefore, the irregular flexibility of the wires of the porous sheets (or of mesh) is beneficial to fold the flat foldable heat pipe 100A, and also avoids to collapse the flexible sheets 104A and 104B.
In accordance with an embodiment, the porous sheets comprise a mesh made of first wires extending in the direction along the channels 110 and second wires extending in the direction across the channels 110, wherein each of the second wires is arranged essentially along a straight line. As the second wires have high strength as compared to the first wires, therefore the first wires are woven (or corrugated) over and under the second wires. Moreover, the second wires of the porous sheets are extending in the direction across the channels 110, and each of the second wires is arranged essentially along a straight line. Therefore, the porous sheets are more flexible in a direction along the channels 110. Thus, the folding and flexibility of the flat foldable heat pipe 100A is improved.
In accordance with an embodiment, the porous sheets comprise one or more of through holes, grooves, and ribs, that extend in the direction across the channels 110. As one or more of the through holes (e.g., narrow holes), the grooves, and the ribs (e.g., micro-ribs) of the porous sheets extends in the direction across the channels 110. Therefore, the porous sheets are very flexible for deformation along the channels 110.
In accordance with an embodiment, the porous sheets have weakened areas that align with the additional channels 112. In other words, the weakened areas of the porous sheets are aligned with the additional channels 112 and also with the area of the groove of the spacer 106. Therefore, larger deformations of porous sheets can be achieved during folding of flat foldable heat pipe towards direction along the channels keeping small deformation of the flexible sheets 104A and 104B across the channels under uniform mechanical load. Thus, the porous sheets with irregular flexibility are suitable for folding together with other structures of the flat foldable heat pipe 100A along the channels 110 and avoid deformation of the flexible sheets 104A and 104B, which have direction across channels 110.
In accordance with an embodiment, the weakened areas of the porous sheets comprise one or more of grooves, dimples and through holes. In other words, the weakened areas of the porous sheets that align with the additional channels 112 comprises one or more grooves, dimples and through holes for creation of an anisotropic flexibility. Therefore, most part of the flexible sheets 104A and 104B deformation is allocated near the groove of the spacer 106. Further, such a re-distribution of stress in the materials leads to less deformation of the flexible sheets 104A and 104B near the channels 110.
In accordance with an embodiment, the flexible sheets 104A and 104B comprise ribs extending in a direction across the channels 110. In other words, the flexible sheets 104A and 104B have non-regular micro-patterns in form of ribs (or micro-ribs) across the channels 110. The flexible sheets 104A and 104B with such ribs is more flexible towards direction along the channels 110 and less flexible towards direction across the channels 110. In addition, the ribs of the flexible sheets 104A and 104B are beneficial to avoid collapse of the flexible sheets 104A and 104B near the channels 110 (under vacuum).
In accordance with an embodiment, the ribs on the flexible sheets 104A and 104B are arranged with gaps that align with the additional channels 112. The gaps between the ribs of the flexible sheets 104A and 104B on the area of additional channels 112 lead to redistribution of deformation of the flexible sheets 104A and 104B which leads to less deformation of the flexible sheets. Thus the most part of deformation of the flexible sheets 104A and 104B is allocated near the groove of the spacer 106, which results in less deformation of the flexible sheets 104A and 104B near channels 110.
In an example, material of the flexible sheets 104A and 104B and the spacer 106 may be PET (Polyethylene terephthalate), PEN (Polyethylene naphthalate), EVOH (Ethylene vinyl alcoho), PVdC (Polyvinylidenechloride), PA (polyamide), PAN (Polyacrylonitrile), COC (Cyclic olefin copolyme), PEEK (Polyether ether ketone) or any combination of above materials, with inorganic coating and laminated together. In an example, material of porous sheets and micro ribs may include Polymer or metallic mesh, Pillars and grooves (metal or polymer) produced by etching or lithography or hot embossing, Metallic or polymer fibres, Sintered metallic or polymer particles, Artificial roughness produced by cutting, Artificial roughness produced by deposition of particles, Artificial roughness produced by abrasive milling.
In an example, a maximum deformation of the flexible sheet with different types of porous sheets and spacer is provided in the table 1. A design N1 of a conventional flat foldable heat pipe having uniform copper mesh of porous sheets and uniform thickness of spacer have a deformation of 0.0366 millimetres (mm) above the channels. A design N2 of a flat foldable heat pipe 100A having uniform copper mesh of porous sheets and non-uniform thickness of spacer have a deformation of 0.0255 mm which is 30 percentages less than conventional design N1 of the flat foldable heat pipe. A design N3 of a flat foldable heat pipe 100A having non-uniform copper mesh of porous sheets and uniform thickness of spacer have a deformation of 0.0316 mm which is 14 percentages less than conventional design N1 of the flat foldable heat pipe. A design N4 of a flat foldable heat pipe 100A having non-uniform copper mesh of porous sheets and non-uniform thickness of spacer have a deformation of 0.0217 mm which is 41 percentages less than conventional design N1 of the flat foldable heat pipe. The designs N2, N3, N4 have width of channel as 0.8 mm and distance between two channels as 1.2 mm. The material of spacer 106 is polyethylene terephthalate. The material of the flexible sheets 104A and 104B is polyethylene terephthalate film with thickness of 0.03 mm.
Table 1
The uniform spacer has uniform thickness of D 1= D 2=0.2 mm. The non-uniform spacer has variable thickness of D 1=0.1 mm and D 2=0.2 mm. This is shown and described further in FIG. 2L. The uniform copper mesh with uniform wires have first and second wire diameters as dl=d2=0.03 mm and total thickness as 0.06 mm. The non-uniform copper mesh has first and second wires diameters as dl=0.02 mm and d2=0.04 mm and total thickness as 0.06 mm. This is shown and described further in FIG. 5.
The present disclosure provides an improved flat foldable heat pipe 100A which have lower wall (i.e. flexible sheets 104A and 104B) collapsing in comparison to conventional heat pipes. The wall collapsing of the flat foldable heat pipe 100A of the present disclosure in comparison to conventional heat pipes is decreased without increasing thickness of the flexible sheet 104A and 104B or thickness of the flat foldable heat pipe 100A or a distance between supporting structures of the spacer 106. The thickness of the spacer 106 of the present disclosure is variable, such as the thickness of the spacer near channels 110 is larger compared to thickness far from the channels 110. Due to non-uniform thickness of spacer 106, flexible sheets 104A and 104B move in both the channels 110 and the additional channels 112 under uniform load, as a result of which deformation of the flexible sheets 104A and 104B is spread, and thus deformation is less as compared to deformation of flexible sheets of flat foldable heat pipes with conventional shape of spacers with uniform thickness. Thus, non-uniform structure of the spacer 106 and the flexible sheets 104A and 104B lead to less deformation of flexible sheets 104A and 104B under vacuum and improved flexibility performance during folding of the flat foldable heat pipe 100A. FIG. IB is an exploded view of a flat foldable heat pipe, in accordance with an embodiment of the present disclosure. FIG. IB is described in conjunction with FIG. 1A. With reference to FIG. IB there is shown a flat foldable heat pipe 100B that comprises the flexible sheets 104A and 104B, the spacer 106, and channels 110.
The flexible sheets 104A and 104B are the outer surfaces of the flat foldable heat pipe 100B. The flexible sheets 104A and 104B corresponds to flexible walls, for example thin polymeric walls made of one or more polymers which are used to form the sealed container 102 of FIG. 1 A of the flat foldable heat pipe 100B.
The spacer 106 may also be referred to as a flexible spacer or a flexible film or a flexible plate with parallel channels (i.e. the channels 110) of variable thickness and a non-uniform (or non-regular) structure. In an example, the direction of the channels 110 of the spacer 106 is selected based on layout of application and operational principle of the flat foldable heat pipe 100B. The spacer 106 is encapsulated within the flexible sheets 104A and 104B to form the container 102 of FIG. 1 A. The spacer 106 is covered from both sides (e.g., top and bottom sides) by the flexible sheets 104A and 104B, and the uncovered walls of the spacers 106 defines channels 110.
In accordance with an embodiment, the channels 110 are suitable for transporting the working fluid 108 A of FIG. 1 A in the vapor state. Such as, during operation of the flat foldable heat pipe 100B, the vapor state of the working fluid 108A is transported through the channels 110.
FIGs. 2A, 2B, and 2C are illustrations of a spacer for a flat foldable heat pipe, in accordance with various embodiment of the present disclosure. With reference to FIG. 2A there is shown a spacer 202A. With reference to FIG. 2B there is shown a spacer 202B. With reference to FIG. 2C there is shown a spacer 202C. The spacers 202A, 202B and 202C have different shapes each having non-regular thickness (i.e. increased thickness) from both sides.
The spacers 202 A, 202B, and 202C corresponds to the spacer 106 of FIG. 1 A. In accordance with an embodiment, the one or more walls of the spacer (such as the spacers 202A, 202B and 202C) with non-regular thickness are provided with longitudinal grooves defining the additional channels (such as the additional channels 112 of FIG. 1A). The spacers 202A, 202B and 202C are provided with longitudinal grooves on both sides to enable formation of r additional channels (such as the additional channels 112 of FIG. 1A) which transport working fluid (such as the working fluid 108B FIG.
1A) in the liquid state. In an example, each of the spacers 202 A, 202B and 202C have different shapes based on user requirement such as cost, speed and amount of heat dissipation and the like.
FIGs. 2D, 2E, 2F are illustrations of a spacer for a flat foldable heat pipe, in accordance with various embodiment of the present disclosure. With reference to FIG. 2D there is shown a spacer 204A. With reference to FIG. 2E there is shown a spacer 204B. With reference to FIG. 2F there is shown a spacer 204C. The spacers 204A, 204B, and 204C have different shapes each having non-regular thickness (i.e., increased thickness) from one side.
In accordance with an embodiment, the one or more walls of the spacer (such as the spacers 204A, 204B and 204C) with non-regular thickness are provided with longitudinal grooves defining the additional channels (such as the additional channels 112 of FIG. 1A). The spacers 204A, 204B and 204C are provided with longitudinal grooves on one side to enable formation of the additional channels (such as the additional channels 112 of FIG. 1 A) which transport the working fluid (such as the working fluid 108B FIG. 1 A) in the liquid state.
FIGs. 2G, 2H are illustrations of a spacer for a flat foldable heat pipe, in accordance with another embodiment of the present disclosure. With reference to FIG. 2G there is shown a spacer 206A. With reference to FIG. 2H there is shown a spacer 206B. The spacers 206A and 206B have different shapes each having non-regular thickness (i.e. increased thickness) from one side and have integrated other side.
In accordance with an embodiment, the one or more walls of the spacer (such as the spacers
206A and 206B) with non-regular thickness are provided with longitudinal grooves defining the additional channels (such as the additional channels 112 of FIG. 1 A). The spacers 206 A and 206B are provided with longitudinal grooves on one side to enable formation of the additional channels (such as the additional channels 112 of FIG. 1A) which transport the working fluid (such as the working fluid 108B FIG. 1A) in the liquid state. Each of the spacers 206 A and 206B have the other side integrated together with adjacent spacer in order to form deep channels instead of through holes for transporting of the working fluid (such as the working fluid 108 A FIG. 1 A) in a vapor state. FIGs. 21, 2J, 2K are illustrations of a spacer for a flat foldable heat pipe, in accordance with another embodiment of the present disclosure. With reference to FIG. 21 there is shown a spacer 208A. With reference to FIG. 25 there is shown a spacer 208B. With reference to FIG. 2K there is shown a spacer 208C. The spacers 208A, 208B, and 208C have different shapes each having non-regular thickness (i.e. increased thickness) from both sides.
In accordance with an embodiment, the one or more walls of the spacer (such as the spacers 208A, 208B and 208C) with non-regular thickness are provided with longitudinal grooves defining the additional channels (such as the additional channels 112 of FIG. 1A). The spacers 208A, 208B and 208C are provided with longitudinal grooves on both sides to enable formation of the additional channels (such as the additional channels 112 of FIG. 1A) which transport the working fluid (such as the working fluid 108B FIG. 1A) in the liquid state.
In accordance with an embodiment, the longitudinal grooves are provided with irregularities and/or protruding elements, the irregularities and/or protruding elements forming a capillary structure. The spacer 208A has micro-patterns on an area of the longitudinal grooves for forming the capillary structure, and for transporting the working fluid (such as the working fluid 108B FIG. 1 A) in the liquid state with a high capillary pressure.
In accordance with an embodiment, the longitudinal grooves are provided with porous coating forming a capillary structure. The spacer 208B has porous coating on the surface for transporting the working fluid in the liquid state with the high capillary pressure.
In accordance with an embodiment, the longitudinal grooves are provided with through holes. The additional through holes of the spacer 208C are used for interconnection between the longitudinal grooves.
FIG. 2L is an illustration of a spacer for a flat foldable heat pipe, in accordance with another embodiment of the present disclosure. With reference to FIG. 2L there is shown a spacer
210.
The spacer 210 has a width of channel W1 as 0.8 mm (millimetres) and distance between two channels W2 as 1.2 mm. In an example, the width of channel W1 may be 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 mm up to 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 mm. The distance between two channels W2 is greater than the width of channel Wl. In an example, the distance between two channels W2 may be 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 mm up to 1.0, 1.1, 1.2, 1.3, 1.4, or 1.6 mm. Further, the spacer 210 is a non-uniform spacer having variable thickness of D1 as 0.1 mm and D2 as 0.2 mm.
FIGs. 3A, 3B, 3C, and 3D are illustrations of channels of a spacer for a flat foldable heat pipe, in accordance with different embodiments of the present disclosure. With reference to FIG. 3A, there is shown a spacer 300A. With reference to FIG. 3B, there is shown a spacer 300B. With reference to FIG. 3C, there is shown a spacer 300C. With reference to FIG. 3D, there is shown a spacer 300D.
The FIGs. 3A, 3B, 3C, and 3D show different possible shape of channels of spacers 300A and 300D. The spacer 300A has a shape of channels which is generally used in the flat foldable heat pipes (such as the flat foldable heat pipe 100A of FIG. 1A). The spacer 300B has channels with branched shape. The spacer 300C has channels having PHP (Pulsating Heat Pipe) like shape. The spacer 300D has channels which are L-shaped. A direction of the channels is selected based on layout of an application of the flat foldable heat pipe (such as flat foldable heat pipe 100A of FIG. 1A), and according to an operational principle of the flat foldable heat pipe (such as flat foldable heat pipe 100A of FIG. 1 A).
FIG. 4 is an illustration of an exploded view of a flat foldable heat pipe, in accordance with an embodiment of the present disclosure. FIG. 4 is described in conjunction with FIG. 1 A and IB. With reference to FIG. 4 there is shown a flat foldable heat pipe 400. The flat foldable heat pipe 400 comprises porous sheets 402 A and 402B. There is further shown the flexible sheets 104A and 104B, the spacer 106, and the channels 110.
In accordance with an embodiment, the porous sheets 402A and 402B are housed in the container (such as container 102) that sandwich the spacer 106. The porous sheets 402A and 402B may also be referred to as thin porous sheets. The porous sheets 402 A and 402B are arranged between the flexible sheets 104A and 104B and the spacer 106. Specifically, the porous sheet 402A is arranged between the flexible sheets 104A and the spacer 106 and the porous sheet 402B is arranged between the flexible sheets 104B and the spacer 106.
In accordance with an embodiment, the porous sheets 402A and 402B exert a capillary force for transporting the working fluid (such as working fluid 108B). The porous sheets 402A and 402B are used as additional way for transporting the liquid form of working fluid and creation of capillary pressure (e.g., driving force for working fluid circulation).
In accordance with an embodiment, the porous sheets 402A and 402B are more flexible in a direction along the channels 110 than in a direction across the channels 110. A porous structure of such porous sheets 402 A and 402B is arranged in such way that the porous sheets 402 A and 402B are softer during bending towards direction along the channels 110 as compared to the bending towards direction across the channels 110. The porous sheets 402A and 402B are very flexible during folding of the flat foldable heat pipe 400, but at the same time can hold the flexible sheets 104A and 104B, because deformation of the flexible sheets 104A and 104B during vacuuming goes in opposite direction as compared to the folding of the flat foldable heat pipe 400.
FIG. 5 is an illustration of a porous sheet of a flat foldable heat pipe, in accordance with an embodiment of the present disclosure. FIG. 5 is described in conjunction with FIG. 4. With reference to FIG. 5 there is shown the porous sheet 402A with first wires 502A, and second wires 502B.
In accordance with an embodiment, the porous sheets (such as porous sheet 402 A) comprise a mesh made of first wires 502A extending in a direction along the channels (such as channels 110 of FIG. 1 A) and second wires 502B extending in a direction across the channels (such as channels 110 of FIG. 1A), the first wires 502 A having a smaller diameter than the second wires 502B. The first wires 502A and the second wires 502B are made of metal (e.g., copper metal). The porous sheet 402 A have a non-regular mesh with different diameters of the first wires 502A and the second wires 502B, and have irregular flexibility. The first wires 502 A are very soft and arranged along the channels (such as channels 110 of FIG. 1A), so that to avoid the destruction of the porous sheet 402A during folding of the flat foldable heat pipe (such as flat foldable heat pipe 400 of FIG. 4). The second wires 502B (with high strength) are arranged across the channel (such as the channels 110 of FIG. 1A) to avoid deformation of flexible sheets (such as the flexible sheet 104A). As a result, such irregular flexibility of mesh suits folding of the flat foldable heat pipe (such as flat foldable heat pipe 400 of FIG. 4) and at the same time avoid the flexible sheets to collapse. In accordance with an embodiment, the porous sheets (such as porous sheet 402A) comprise a mesh made of the first wires 502A extending in the direction along the channels (such as channels 110 of FIG. 1A) and the second wires 502B extending in the direction across the channels (such as channels 110 of FIG. 1A), wherein each of the second wires 502B is arranged essentially along a straight line. The second wires 502B is arranged essentially along the straight line and the first wires 502A is arranged above or below alternatively on the second wire 502B to form the mesh. In other words, the first wires 502A are corrugated over and under the second wires 502B, therefore the porous sheets are more flexible in the direction along the channels.
The first wires 502A have a diameter dl of 0.02mm and pitch pi. The second wires 502B have a diameter d2 of 0.04 mm and pitch p2, wherein dl < d2 and (or) pi > p2.
FIGs. 6A-6D are illustrations of porous sheets of a flat foldable heat pipe, in accordance with various embodiments of the present disclosure. FIGs. 6A-6D are described in conjunction with FIG. 1A and IB. With reference to FIG. 6A there is shown porous sheets 602A and 602B. There is further shown the spacer 106.
In accordance with an embodiment, the porous sheets 602A and 602B comprise through holes 604A and 604B that extend in the direction across the channels (such as the channels 110 of the FIG.1A). The porous sheets 602 A and 602B have holes 604 A and 604B which are narrow and rectangular in shape. Such porous sheets 602 A and 602B are very flexible for deformation along the channels (such as the channels 110 of the FIG.l A), however larger deformations of porous sheets 602A and 602B are possible during folding of flat foldable heat pipe along the channels keeping low deformation of flexible sheets in the direction across the channels (such as the channels 110 of the FIG.l A). As a result, such porous sheets 602A and 602B with irregular flexibility suits for folding along the channels (such as the channels 110 of the FIG.l A) and avoid deformation of the flexible sheets (such as flexible sheets 104A and 104B of the FIG. 1 A), which have direction across channels.
With reference to FIG. 6B there is shown porous sheet 606. There is further shown the spacer
106.
In accordance with an embodiment, the porous sheet 606 comprise through ribs 608 that extend in the direction across the channels (such as the channels 110 of the FIG.l A). The porous sheet 606 have ribs 608 which are micro-ribs. Such porous sheet 606 with irregular flexibility suits for folding along the channels (such as the channels 110 of the FIG.1A) and avoid deformation of the flexible sheets (such as the flexible sheets 104A and 104B of the FIG. 1 A), which have direction across channels.
With reference to FIG. 6C and 6D there is shown porous sheets 610. There is further shown the flexible sheet 104A and the spacer 106.
In accordance with an embodiment, the porous sheets 610 have weakened areas 612 that align with the additional channels (such as the additional channels 112 of FIG. 1A). The weakened areas 612 enable creation of anisotropic flexibility. The weakened areas 612 may also be referred to as areas of groove.
In accordance with an embodiment, the weakened areas 612 of the porous sheets 610 comprise one or more of grooves, dimples and through holes. By virtue of the through hole on the weakened areas 612, most part of deformation will be allocated near the weakened areas 612. Such re-distribution of stress in the materials will lead to less deformation of flexible sheet 104A of FIG. 1A near working fluid 108A in a vapor state, i.e. near the channels.
FIG. 7 is an illustration of a flat foldable heat pipe, in accordance with an embodiment of the present disclosure. FIG. 7 are described in conjunction with FIG. 1 A and IB. With reference to FIG. 7 there is shown a flexible sheet 702A. There is further shown the flexible sheet 104A and the spacer 106.
In accordance with an embodiment, the flexible sheets (such as the flexible sheet 702A) comprise ribs 704A extending in a direction across the channels (such as the channels 110 of the FIG. 1A). The flexible sheets (such as the flexible sheet 702 A) have non-regular micro-patterns in form of ribs 704 A across the channels (such as the channels 110). The flexible sheet 702A with such ribs 704A is more flexible towards the direction along the channels (such as the channels 110) and less flexible towards the direction across the channels (such as the channels 110). As a result, the flexible sheet 702A avoid collapsing under vacuum near the working fluid 108A of FIG. 1 A in a vapor state.
FIG. 8 is an illustration of a section of a flat foldable heat pipe along the channels, in accordance with an embodiment of the present disclosure. The FIG.8 shows a cross-sectional view along cross section A-A of the flat foldable heat pipe of FIG. 7. FIG. 8 is described in conjunction with FIG. 1 A, IB and 7. With reference to FIG. 8 there is shown a flexible sheet 702B. There is further shown the flexible sheet 702A and the spacer 106.
In accordance with an embodiment, the flexible sheets 702A and 702B comprise ribs 704A and 704B extending in a direction across the channels (such as the channels 110 of the FIG. 1A). The flexible sheet 702 A comprises ribs 704 A, and the flexible sheet 702B comprises ribs 704B. The ribs 704A of the flexible sheet 702A avoid the flexible sheet 702A to collapse with the flexible sheet 702B near the channels (such as the channels 110 of the FIG. 1A). Moreover, the ribs 704B of the flexible sheet 702B avoid the flexible sheet 702B to collapse with the flexible sheet 702A near the channels (such as the channels 110 of the FIG. 1 A).
FIG. 9 is an illustration of a flexible sheet of a flat foldable heat pipe, in accordance with an embodiment of the present disclosure. FIG. 9 are described in conjunction with FIG. 7. With reference to FIG. 9 there is shown the flexible sheet 702A which include ribs 704A. The flexible sheet 702A with such ribs 704A is more flexible towards direction along the channels (such as the channels 110) and less flexible towards direction across the channels (such as the channels 110). As a result, the flexible sheet 702 A avoid collapsing under vacuum near the working fluid 108A of FIG. 1A in a vapor state, i.e. near the channels.
FIG. 10 is an illustration of an exploded view of a flat foldable heat pipe, in accordance with an embodiment of the present disclosure. FIG. 10 is described in conjunction with FIG. 1 A, IB and 7. With reference to FIG. 10 there is shown the flexible sheet 104A, the flexible sheet 702A and the spacer 106. The flexible sheet 702A includes the ribs 704A.
In accordance with an embodiment, the ribs 704A on the flexible sheets (such as flexible sheet 702A) are arranged with gaps 1000 that align with the additional channels (such as the additional channels 112 of FIG. 1A). Such gaps 1000 between the ribs 704 A on the area of working fluid 108B in a liquid state lead to re-distribution of deformation of flexible sheet 702A, and the most part of deformation will be allocated near the gaps 1000. Therefore, such gaps 1000 leads to less deformation of the flexible sheet 702 A near working fluid 108 A in a vapor state.
FIG. 11 is an illustration of a flat foldable heat pipe, in accordance with an embodiment of the present disclosure. FIG. 11 is described in conjunction with FIG. 1 A, IB, 7 and 10. With reference to FIG. 11 there is shown the flexible sheet 702A, the ribs 704A and the spacer
106.
The area of flexible sheet 702A near channels (such as the channels 110 of FIG. 1 A) is more soft during bending towards the direction along the channels (such as the channels 110) as compared to the bending towards the direction across the channels (such as the channels 110). The areas of flexible sheet 702 A near the spacer 106 is more soft during bending towards the direction across the channels (such as channels 110) as compared to the bending towards the direction along the channels (such as the channels 110). An average thickness of the flexible sheet 702A with the ribs 704A and 704B on the areas near the channels (such as channels 110) is larger compared to average thickness of the flexible sheet 702 A near the spacers 106. Further, the ribs 704A on the flexible sheets 702A are arranged with the gaps 1000 that align with the additional channels (such as the additional channels 112 of FIG. 1A).
FIG. 12A-12B are illustrations of cross-sectional view of a flat foldable heat pipe of FIG. 11, in accordance with different embodiments of the present disclosure. FIG. 12A-12B are described in conjunction with FIG. 1 A, IB, 7 and 10. With reference to FIG. 12A-12B there is shown the flexible sheet 702A, the ribs 704A, the flexible sheet 702B, the ribs 704B and the spacer 106.
FIG. 12A is cross-sectional view along cross section B-B of the flat foldable heat pipe of FIG. 11. FIG. 12B is cross-sectional view along cross section C-C of the flat foldable heat pipe of FIG. 11. The areas of the flexible sheet 702A and 702B near channels (such as the channels 110 of FIG. 1A) is more soft during bending towards direction along the channel (such as the channels 110) as compared to the bending towards direction across the channels (such as the channels 110). The areas of the flexible sheet 702A and 702B near the spacer 106 is more soft during bending towards the direction across the channels (such as the channels 110) as compared to the bending towards the direction along the channels (such as the channels 110). (Average thickness of the flexible sheet 702A and 702B with the ribs 704A and 704B on the areas near channels (such as the channels 110) is larger compared to average thickness of the flexible sheet 702 A and 702B near the spacers 106). Further, the ribs 704 A and 704B on the flexible sheets 702 A and 702B respectively in FIG. 12B are arranged with the gaps 1000 that align with the additional channels (such as the additional channels 112 of FIG. 1A).
Modifications to embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as "including", "comprising", "incorporating", "have", "is" used to describe and claim the present disclosure are intended to be construed in a non-exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural. The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments. The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". It is appreciated that certain features of the present disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the present disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable combination or as suitable in any other described embodiment of the disclosure.
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