Heat pipe and method of manufacturing a heat pipe

Abstract

A heat pipe (100, 200, 300, 400, 500, 600, 700) is provided having an envelope (102, 202, 302) with working fluid, a wick (108, 206, 504) inner layer, and a flexible bellows (104). The envelope has a condenser end, an evaporator end, and an adiabatic portion between the condenser end and the evaporator end. The wick inner layer is disposed on an inner surface of the envelope for transporting condensed working fluid from the condenser end to the evaporator end. The adiabatic portion includes perforations of the envelope wall forming passages for vapor and compression regions (106, 204, 502) in which the envelope wall is offset toward a central axis of the envelope. The flexible bellows covers the compression regions and defines passages (112) for the vapor, ends of the flexible bellows being sealed to the envelope wall outside the perforations.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to heat pipes, and more particularly to heat pipes and methods of manufacturing heat pipes. BACKGROUND

[0002] A heat pipe is a special device that can transport heat over a large distance due to the combination of the following processes: (a) evaporation of a liquid phase of an internal working medium from a porous structure (wick), (b) transport of a gas phase of the internal medium through a vapor channel, (c) condensation of the gas phase of the internal medium on the wick, and (d) transport of the liquid phase of the internal medium through the wick from the condensation area to the evaporation area in one closed loop inside a sealed envelope (shell).

[0003] In known methods, different application fields of heat pipes consider that there is no strong mechanical interconnection between the cooler block and the heater block. In this case, for example, the cooler block can move in space relative to the heater block. In existing heat pipes, one end of the heat pipe is fixed and the other end moves in the vertical direction by ±1.5 millimeters (mm). To avoid damaging the heat pipe or to avoid the heat pipe from separating from the cooler block and the heater block, the heat pipe should be flexible, i.e., the reaction force from either the heater block or the cooler block on the heat pipe should be low, e.g., less than 2.5 Newton units (N). Existing heat pipes are flat heat pipes that have a reaction force of about 25 N to 50 N during such movement, which is far from the low value (e.g., 2.5 N) required for flexibility.

[0004] Several known solutions address this problem by attaching a bellows-shaped portion to the heat pipe. However, the known solutions have problems for manufacturing heat pipes in a mass production mode. In addition, the mesh on the curved area of the heat pipe is not attached to the substrate (wall), which results in low capillary force. The known solutions also use a wick that is located near the outer wall instead of being located in the center of the heat pipe, which results in high elongation, high stress, and ultimately, damage to the heat pipe. The known solutions also propose adding springs in the heat pipe, but do not completely solve the damage problem and also occupy internal space, resulting in low thermal performance. The known solutions also propose complex designs that have many components that need to be assembled during the manufacturing process. Therefore, these designs are not suitable for mass production. Furthermore, the known solutions propose locating the wick close to the flexible wall in the heat pipe, which causes the wick layer to move away from the neutral plane (a zero stress area near the axis of the heat pipe) and become elongated during bending, which results in an increase in the reaction force and can damage the wick.

[0005] Therefore, there is a need to address the above technical problems in existing systems or techniques to create a heat pipe that is suitable for mass production and has reduced reaction force, thereby having flexibility. SUMMARY

[0006] An object of the present invention is to provide a heat pipe and a method of manufacturing a heat pipe, which is suitable for mass production and has reduced reaction force from a heating block or a cooling block, thereby having flexibility.

[0007] This object is achieved by the features of the independent claims. Further implementation forms are evident from the dependent claims, the description and the figures.

[0008] The present invention provides a heat pipe with small reaction force for mass production and a method of manufacturing the heat pipe.

[0009] According to a first aspect, a heat pipe is provided. The heat pipe comprises an envelope with a working fluid, a core inner layer and a flexible bellows. The envelope has a condenser end, an evaporator end and an adiabatic portion between the condenser end and the evaporator end. The core inner layer is arranged on an inner surface of the envelope for transporting condensed working fluid from the condenser end to the evaporator end. The adiabatic portion comprises perforations of the wall of the envelope forming channels for vapor and compression regions in which the wall of the envelope is offset towards a central axis of the envelope. The flexible bellows covers the compression regions and defines the channels for vapor, the end portions of the flexible bellows being sealed to the wall of the envelope outside the perforations.

[0010] Compared to conventional heat pipes, the heat pipe according to the present invention has reduced reaction force, thereby having flexibility. For example, in one implementation, a reaction force of less than 2.5 Newton units (N) has been achieved. Furthermore, the heat pipe is simple in design, suitable for mass production. At the same time, the heat performance of the heat pipe is comparable to conventional non-flexible heat pipes for mass production, which indicates that the design is simple, flexible and has no drawbacks in terms of heat performance.

[0011] In a first possible implementation, the perforations of the wall of the envelope comprise longitudinal through-holes made by two opposite sides of the envelope.

[0012] In a second possible implementation, the compression regions comprise planar channels for transporting the condensed working fluid, the planar channels each having a tapered portion at both ends.

[0013] In a third possible implementation, the planar channels are arranged substantially in a plane of the central axis of the envelope.

[0014] In a fourth possible implementation, the flexible bellows has an elliptical cross-section.

[0015] In a fifth possible implementation, the compression regions are provided with fixation means provided on the wall of the envelope, the wall of the envelope being offset towards the central axis of the envelope.

[0016] In a sixth possible implementation, the securing means is one of a wire wrap, a foil wrap, and a contact resistance weld.

[0017] In a seventh possible implementation, the perforations of the wall of the envelope include one or more additional through-holes forming the passage for the vapor.

[0018] In an eighth possible implementation, the perforations of the wall of the envelope extend to a substantial portion of the circumference of the envelope.

[0019] In a ninth possible implementation, the wall and / or core layer of the envelope in the compression region is provided with one or more transverse grooves and / or through-holes.

[0020] In a tenth possible implementation, a core outer layer is arranged on an inner surface of the flexible bellows, the core outer layer being in communication with the core inner layer.

[0021] In an eleventh possible implementation, a second core outer layer is arranged on an outer surface of the envelope in the compression region, the second core outer layer being in communication with the core inner layer.

[0022] In a twelfth possible implementation, the condenser end is flat to the evaporator end.

[0023] In a thirteenth possible implementation, an outer surface of the flexible bellows is provided with a layer of low thermal conductive material.

[0024] In a fourteenth possible implementation, the core includes one or more of sintered particles, mesh, fibers, and grooves.

[0025] According to a second aspect, there is provided a method of manufacturing a heat pipe. The method comprises providing an envelope having a condenser end, an evaporator end, and an adiabatic portion therebetween. The method comprises arranging a core layer on an inner surface of the envelope for transporting condensed working fluid from the condenser end to the evaporator end. The method comprises perforating a wall of the envelope in the adiabatic portion to form a passage for the vapor. The method comprises offsetting the wall of the envelope towards a central axis of the envelope to define a compression region in the adiabatic portion. The method comprises covering the compression region with a flexible bellows to define the passage for the vapor, end portions of the flexible bellows being sealed to the wall of the envelope outside the perforations. The method comprises filling the envelope with the working fluid. The method comprises sealing the condenser end and the evaporator end of the envelope.

[0026] According to a third aspect, a method of manufacturing a heat pipe is provided. The method comprises providing an envelope having a condenser end, an evaporator end and a thermally insulating portion therebetween. The method comprises perforating a wall of the envelope in the thermally insulating portion to form a passage for vapour. The method comprises arranging a wick layer on an inner surface of the envelope for transporting condensed working fluid from the condenser end to the evaporator end. The method comprises offsetting the wall of the envelope towards a central axis of the envelope to define a compression region in the thermally insulating portion. The method comprises covering the compression region with a flexible bellows to define the passage for vapour, end portions of the flexible bellows being sealed to the wall of the envelope outside the perforations. The method comprises filling the envelope with the working fluid. The method comprises sealing the condenser end and the evaporator end of the envelope.

[0027] According to a fourth aspect, a method of manufacturing a heat pipe is provided. The method comprises providing an envelope having a condenser end, an evaporator end and a thermally insulating portion therebetween. The method comprises perforating a wall of the envelope in the thermally insulating portion to form a passage for vapour. The method comprises offsetting the wall of the envelope towards a central axis of the envelope to define a compression region in the thermally insulating portion. The method comprises arranging a wick layer on an inner surface of the envelope for transporting condensed working fluid from the condenser end to the evaporator end. The method comprises covering the compression region with a flexible bellows to define the passage for vapour, end portions of the flexible bellows being sealed to the wall of the envelope outside the perforations. The method comprises filling the envelope with the working fluid. The method comprises sealing the condenser end and the evaporator end of the envelope.

[0028] The technical problem in the prior art is solved, where the technical problem is that in order to avoid damaging the heat pipe or to avoid the heat pipe detaching from the cooler block and the heater block, the heat pipe should be flexible, i.e. the counter force from either of the heater block or the cooler block on the heat pipe should be reduced, e.g. below 2.5 N.

[0029] Thus, in contrast to the prior art, according to the heat pipe and the method of manufacturing a heat pipe, the heat pipe is flexible due to the reduced counter force compared to conventional heat pipes. The heat pipe is simple in design, suitable for mass production. At the same time, the heat performance of the heat pipe is comparable to conventional non-flexible heat pipes produced in large scale, which indicates that the design is simple, flexible and has no drawbacks in terms of heat performance.

[0030] These and other aspects of the application are apparent from the following description, taken in conjunction with the accompanying drawings, illustrating one or more implementations of the application. BRIEF DESCRIPTION OF DRAWINGS

[0031] The implementations of the application will be described, by way of example only, with reference to the drawings, in which:

[0032] Figure 1A A heat pipe with a flexible corrugated tube is shown as an embodiment of the present invention;

[0033] Figure 1B The embodiment of the present invention is shown in the form of a flexible bellows prior to the manufacturing process. Figure 1A An exemplary view of a heat pipe;

[0034] Figure 1C The implementation of the present invention is shown. Figure 1A A perspective view of the heat pipe;

[0035] Figure 1D The implementation of the present invention is shown. Figure 1A A longitudinal cross-sectional view of the heat pipe;

[0036] Figure 1E The implementation of the present invention is shown. Figure 1A A cross-sectional view of the heat pipe;

[0037] Figure 2 A heat pipe having one or more lines forming a connection between one or more compression walls is shown as an implementation of the present invention;

[0038] Figure 3 A heat pipe with additional through-holes for steam flow is shown as an implementation of the present invention;

[0039] Figure 4 A heat pipe with additional orifices for steam flow is shown as an implementation of the present invention;

[0040] Figure 5 A heat pipe with a cut upper wall is shown as an embodiment of the present invention;

[0041] Figure 6 A heat pipe having additional vapor holes in the wall of the heat pipe is shown as an implementation of the present invention;

[0042] Figure 7 A heat pipe illustrating an embodiment of the present invention;

[0043] Figure 8 This invention illustrates a heat pipe mechanical testing scheme for implementing the present invention;

[0044] Figure 9 A graph illustrating the mechanical response of a heat pipe under cyclic loading over time is shown to illustrate an implementation of the present invention.

[0045] Figures 10A to 10B A flowchart illustrating a first method for manufacturing a heat pipe according to an embodiment of the present invention;

[0046] Figures 11A to 11Ba flowchart of a second method of manufacturing a heat pipe for an implementation of the present invention; and

[0047] Figures 12A to 12B a flowchart of a third method of manufacturing a heat pipe for an implementation of the present invention. DETAILED DESCRIPTION

[0048] Implementations of the present invention provide a flexible heat pipe with small reaction force for mass production.

[0049] The following implementations of the present invention are described with reference to the drawings, wherein the solutions of the present invention are more easily understood by those skilled in the art.

[0050] The terms "first", "second", "third", and "fourth" (if any) in the description of the present invention, claims, and above drawings are used to distinguish similar objects, and are not necessarily used to describe a particular sequence or order. It should be understood that the terms so used are interchangeable under appropriate circumstances, such that the implementations of the present invention described herein are capable of accomplishing the same object regardless of the sequence or order in which steps are performed. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, method, system, product, or apparatus that comprises a list of steps or units is not necessarily limited to the steps or units explicitly listed, but can include other steps or units not explicitly listed or inherent to such process, method, product, or apparatus.

[0051] Figure 1AA heat pipe 100 with a flexible bellows 104 is shown that implements the present invention. The heat pipe 100 includes an envelope 102 with a working fluid, a wick 108 inner layer, and a flexible bellows 104. The envelope 102 has a condenser end, an evaporator end, and an adiabatic section between the condenser end and the evaporator end. The wick 108 inner layer is disposed on an inner surface of the envelope 102 for transporting condensed working fluid from the condenser end to the evaporator end. The adiabatic section includes perforations of the wall of the envelope 102 that form a passage for vapor and compression regions 106 in which the wall of the envelope 102 is offset toward a central axis of the envelope 102. The flexible bellows 104 covers the compression regions 106 and defines a passage 112 for vapor, with end portions of the flexible bellows 104 sealed to the wall of the envelope 102 outside the perforations. The perforations of the wall of the envelope 102 optionally include longitudinal through-holes 110 made by two opposite sides of the envelope 102. The envelope 102 can be a copper tube. The wick 108 can be a sintered wick or a sintered porous structure that includes sintered powder, a mesh wick, or one or more grooves. Optionally, the wick 108 includes one or more of sintered particles, a mesh, fibers, and grooves. The wick 108 is optionally located on two opposite sides of the inner surface of the envelope 102 and an intermediate region of the envelope 102 that includes the longitudinal through-holes 110. The remaining region of the intermediate region is pressed together in such a way that a portion of the wall and one or more layers of the wick 108 form a flat plate near the axis of the heat pipe 100. Optionally, one felt, one or more grooves, a non-sintered mesh, or multiple felts are used for the sintered porous structure.

[0052] The envelope 102 has a structure for liquid / fluid circulation. The region of the heat pipe 100 with the longitudinal through-holes 110 is encapsulated to the flexible bellows 104. In the region of the heat pipe 100, the open side of the flexible bellows 104 undergoes a soldering procedure together with the envelope 102 on the region without the longitudinal through-holes 110. The soldering procedure can be performed in such a way that the passage 112 is formed between the inner surface of the flexible bellows 104 and the region of the envelope 102 with the longitudinal through-holes 110.

[0053] Reference is made to Figure 1A , Figure 1BAn exemplary view 101 of a heat pipe 100 with a flexible bellows 104 during the manufacturing process is shown to illustrate an implementation of the present invention. The heat pipe 100 includes a jacket 102, a flexible bellows 104, a compression region, a core 108 inner layer, and a longitudinal through hole 110. For manufacturing, a round heat pipe is used with the jacket 102 as a copper wall and the core 108 as a sintered core layer. Optionally, a core 108 outer layer is disposed on an inner surface of the flexible bellows 104, which is in communication with the core 108 inner layer. Optionally, a second core 108 outer layer is disposed on an outer surface of the jacket 102 in the compression region 106, which is in communication with the core 108 inner layer. Optionally, an outer surface of the flexible bellows 104 is provided with a layer of low thermal conductive material. Optionally, a material of the flexible bellows 104 is different from a material of the wall. Two holes are formed on both sides of a middle region of the jacket 102, and the remaining compression region 106 or wall is compressed together in the middle region in such a way that a portion of the wall and one or more layers of the core 108 become flat plates near the axis of the heat pipe 100. The remaining wall of the jacket 102 is not fully compressed, so that the open holes have the function of the longitudinal through hole 110 for circulating vapor between the end of the heat pipe 100 and the volume of the flexible bellows 104. The flexible bellows 104 can be moved to the middle region of the heat pipe 100 so as to cover the region of the heat pipe 100 with the longitudinal through hole 110 and the compression region 106. The compression region 106 can include a flat channel for transporting condensed working fluid, which has one tapered portion at each end, respectively. The flat channel can be disposed in a plane of the central axis of the jacket 102. The plane can be a neutral plane. The core 108 of the heat pipe 100 is located in the middle of the cross section of the heat pipe 100, near the neutral plane where the stress is minimal during bending. Thus, the deformation of the core 108 and the remaining portion of the wall is very small, and the stress and reaction force are also significantly reduced, thereby providing flexibility of the heat pipe 100. The ends of the flexible bellows 104 are welded to the jacket 102. After that, the condenser end to the evaporator end is flat. The wall of the jacket 102 and / or the core 108 layers in the compression region 106 can also be provided with one or more transverse grooves and / or through holes to further reduce the reaction force and increase the flexibility of the heat pipe 100.

[0054] The heat pipe 100 can be manufactured by the following steps: (i) producing a round heat pipe with the core 108 as a sintered core; (ii) performing one or more technical operations, for example, (a) cutting the longitudinal through holes 110 on the sides of the heat pipe 100 according to the length of the flexible area, (b) pressing the two walls and the core 108 together to the axis of the heat pipe 100, (c) inserting the heat pipe 100 into the flexible bellows 104, (d) welding the flexible bellows 104 to the heat pipe 100, and (e) filling the heat pipe 100 with water. The one or more technical operations are suitable for mass production mode of production. The cost increase of the heat pipe 100 is negligible compared to the round heat pipe. Since the flexible bellows 104 needs to be connected to the core 108, any size of the wave can be chosen, and the bending of the flexible bellows 104 is achieved with minimal force.

[0055] Optionally, the flexible bellows 104 has an elliptical cross-section. The flexible bellows 104 can be other shapes, for example, flat shape. Optionally, the outer shell of the heat pipe 100 outside the flexible bellows 104 can be flat, round, or any other shape.

[0056] Referring to Figure 1A and Figure 1B , Figure 1C A perspective view 103 of the heat pipe 100 of an implementation of the present invention is shown. The perspective view 103 is achieved after the manufacturing process. The perspective view 103 includes the envelope 102 and the flexible bellows 104.

[0057] Referring to Figure 1A and Figure 1B , Figure 1D A longitudinal cross-sectional view 105 of the heat pipe 100 of an implementation of the present invention is shown. The longitudinal cross-sectional view 105 includes the envelope 102, the flexible bellows 104, the compression area 106, the core 108, the longitudinal through holes 110, and the channels 112.

[0058] Referring to Figure 1A and Figure 1B , Figure 1E A cross-sectional view 107 of the heat pipe 100 of an implementation of the present invention is shown. The cross-sectional view 107 of the heat pipe 100 includes the envelope 102, the flexible bellows 104, the compression area 106, the core 108, and the longitudinal through holes 110. Optionally, the diameter of the envelope 102 is changed.

[0059] Figure 2A heat pipe 200 with one or more wires 210 forming a connection between one or more compression walls of an implementation of the present invention is shown. The heat pipe 200 includes an envelope 202, a compression region 204, a wick 206, a through hole 208, and one or more wires 210. The compression region 204 or one or more compression walls are secured using the one or more wires 210 of the heat pipe 200 to control the reaction force during bending. The compression region 204 is provided with a securing means disposed on the walls of the envelope 202 that are offset towards the central axis of the envelope 202. The securing means is one of a wire wrap, a foil wrap, and a contact resistance weld.

[0060] Figure 3 A heat pipe 300 with additional through holes 304A-304N for steam flow of an implementation of the present invention is shown. The heat pipe 300 includes an envelope 302 and additional through holes 304A-304N. The perforation of the walls of the envelope 302 includes the additional through holes 304A-304N that form channels for steam.

[0061] Figure 4 A heat pipe 400 with additional holes 402 for steam flow of an implementation of the present invention is shown. The heat pipe 400 includes one or more additional steam holes 402. To achieve a low reaction force, for example, less than 2.5 N, the compression region of the envelope of the heat pipe 400 is configured to be as long as possible. In the heat pipe 400, the additional steam holes 402 for steam can be configured to be as small as possible, but the steam pressure drop is higher for stable operation of the heat pipe 400. To achieve stable operation of the heat pipe 400, one or more additional steam holes 402 can be created within the compression region, as shown in Figure 3 and Figure 4 Optionally, the number and shape of such additional steam holes 402 can be different.

[0062] Figure 5 A heat pipe 500 with a cut upper wall of an implementation of the present invention is shown. The heat pipe 500 includes a compression region 502 and a wick 504. To reduce the reaction force of the heat pipe 500, one of the remaining walls of the compression region 502 is removed, and the thermal problem of the heat pipe 500 can be addressed by optimizing the thickness and shape of the wick 504. Thus, the perforation of the walls of the envelope of the heat pipe 500 extends to a major portion of the circumference of the envelope.

[0063] Figure 6 A heat pipe 600 of an implementation of the present invention is shown, in which the walls of the envelope and / or the wick layer in the compression region are provided with transverse grooves or through holes 602 to further reduce the reaction force and increase the flexibility of the heat pipe 600. The heat pipe 600 includes one or more transverse grooves or through holes 602.

[0064] Figure 7A heat pipe 700 is shown that implements the present application. The heat pipe 700 is in contact with a heater 702, a cooler 704, and includes one or more temperature sensors 706A-706D. The heat pipe 700 can be manufactured with sample walls. The heater 702 and the cooler 704 can be 40 millimeters (mm) wide. The temperature sensor 706A can be placed at the surface of the envelope of the heat pipe 700 at the center point of the heater 702 with 20 mm width on either side of the envelope. The temperature sensor 706D can be placed at the surface of the envelope at the center point of the cooler 704 with 20 mm width on either side of the envelope. The heat pipe 700 can be used for thermal testing, where the core of the heat pipe 700 is sintered copper powder. For thermal testing, the heat pipe 700 is configured using a round heat pipe taken from a mass production factory, and a side hole is cut in the round heat pipe. The walls are pressed against each other, and the flexible bellows of the heat pipe 700 are welded. Alternatively, the walls are pressed against each other using a bonding method, and the walls are pressed against the flexible bellows.

[0065] Thermal testing of the heat pipe 700 is performed after mechanical testing, and the following results are recorded:

[0066]

[0067] The temperature difference between the two ends of the heat pipe 700 is in the range of 1.5°C to 2.5°C in the heating power range of 40 to 50 watts. Similar results can be obtained in mass production of the heat pipe 700, where the overall dimensions of the heat pipe 700 are equal. Thus, the thermal performance of the heat pipe 700 is improved. The thermal testing shows that the heat pipe 700 has low reaction force, simple design, and is suitable for mass production. The thermal performance of the flexible heat pipe 700 is the same as that of the inflexible round heat pipe.

[0068] Figure 8 A scheme 800 of heat pipe mechanical testing is shown that implements the present application. The scheme 800 includes a grip of a tensile machine 802 connected to a first hinge 806A and a second hinge 806B that hold the envelope of a heat pipe. The scheme 800 includes a tight connector 808 that tightly fixes the first end of the envelope of the heat pipe for processing at a point 804A. The second end of the heat pipe is hinged at a point 804B by the first hinge 806A and the second hinge 806B. Using the scheme 800, the mechanical property testing of the heat pipe is performed by measuring the mechanical reaction during 20 loading cycles, which can be performed using the tensile machine and the tool.

[0069] Reference Figure 8 , Figure 9A graph 900 showing mechanical response of the heat pipe over time for an implementation of the present invention is shown. As shown in graph 900, the grip is cycled ±1.5mm 20 times, which is the displacement of the point during the mechanical property test. The speed of movement of the grip can be less than 0.2mm per second. During the cyclic loading, the reaction force of the heat pipe is recorded. The reaction force of the heat pipe can be lower than 2.5N over the 20 loading cycles, while the reaction force of a round heat pipe without the flexible bellow is higher than 20N.

[0070] Figures 10A to 10B A flowchart of a first method of manufacturing a heat pipe for an implementation of the present invention. At step 1002, a jacket having a condenser end, an evaporator end, and an adiabatic portion therebetween is provided. At step 1004, a wick layer is disposed on an inner surface of the jacket for transporting condensed working fluid from the condenser end to the evaporator end. At step 1006, the wall of the jacket in the adiabatic portion is perforated to form a passage for vapor. At step 1008, the wall of the jacket is offset toward a central axis of the jacket to define a compression region in the adiabatic portion. At step 1010, the compression region is covered with a flexible bellow to define the passage for vapor, the ends of the flexible bellow being sealed to the wall of the jacket outside the perforations. At step 1012, the jacket is filled with working fluid. At step 1014, the condenser end and the evaporator end of the jacket are sealed.

[0071] Figures 11A to 11B A flowchart of a second method of manufacturing a heat pipe for an implementation of the present invention. At step 1102, a jacket having a condenser end, an evaporator end, and an adiabatic portion therebetween is provided. At step 1104, the wall of the jacket in the adiabatic portion is perforated to form a passage for vapor. At step 1106, a wick layer is disposed on an inner surface of the jacket for transporting condensed working fluid from the condenser end to the evaporator end. At step 1108, the wall of the jacket is offset toward a central axis of the jacket to define a compression region in the adiabatic portion. At step 1110, the compression region is covered with a flexible bellow to define the passage for vapor, the ends of the flexible bellow being sealed to the wall of the jacket outside the perforations. At step 1112, the jacket is filled with working fluid. At step 1114, the condenser end and the evaporator end of the jacket are sealed.

[0072] Figures 12A to 12BA flowchart of a third method of manufacturing a heat pipe for an implementation of the present invention. At step 1202, a jacket having a condenser end, an evaporator end, and an adiabatic section therebetween is provided. At step 1204, the wall of the jacket in the adiabatic section is perforated to form a passage for vapor. At step 1206, the wall of the jacket is offset toward the central axis of the jacket to define a compression region in the adiabatic section. At step 1208, a core layer is disposed on the inner surface of the jacket for transporting condensed working fluid from the condenser end to the evaporator end. At step 1210, the compression region is covered with a flexible bellows to define the passage for vapor, the ends of the flexible bellows being sealed to the wall of the jacket outside the perforations. At step 1212, the jacket is filled with working fluid. At step 1214, the condenser end and the evaporator end of the jacket are sealed.

[0073] The heat pipe of the present invention provides a simple design that is suitable for mass production. At the same time, the thermal performance of the heat pipe is comparable to conventional non-flexible heat pipes used for mass production, which indicates that the simple design does not have a disadvantage in thermal performance.

[0074] While the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A heat pipe (100, 200, 300, 400, 500, 600, 700) characterized by, Comprising: an envelope (102, 202, 302) with a working fluid, the envelope (102, 202, 302) having a condenser end, an evaporator end and an adiabatic portion between the condenser end and the evaporator end, a core (108, 206, 504) inner layer arranged on an inner surface of the envelope (102, 202, 302) for transporting condensed working fluid from the condenser end to the evaporator end, wherein the adiabatic portion comprises perforations of the envelope (102, 202, 302) wall forming a channel for the vapor and a compression region (106, 204, 502) in which the envelope (102, 202, 302) wall is offset towards a central axis of the envelope (102, 202, 302), a flexible bellows (104) covering the compression region (106, 204, 502) and defining a channel (112) for the vapor, the flexible bellows (104) ends being sealed to the envelope (102, 202, 302) wall outside the perforations.

2. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to claim 1, characterized in that, The perforations of the envelope (102, 202, 302) wall comprise longitudinal through holes (110) made by two opposite sides of the envelope (102, 202, 302).

3. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to claim 1, characterized in that, The compression region (106, 204, 502) comprises a planar channel for transporting the condensed working fluid, the planar channel (112) having one tapered portion at each end.

4. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to claim 3, characterized in that The planar channel is arranged substantially in a plane of the central axis of the envelope (102, 202, 302).

5. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to any one of claims 1 to 4, characterized in that, The flexible bellows (104) has an elliptical cross-section.

6. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to any one of claims 1 to 4, characterized in that, The compression region (106, 204, 502) is provided with a fixing means provided on the envelope (102, 202, 302) wall offset towards the central axis of the envelope (102, 202, 302).

7. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to claim 6, characterized in that The fixing means is one of a wire, a foil wrap and a contact resistance weld.

8. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to any one of claims 1 to 4, characterized in that, The perforations of the envelope (102, 202, 302) wall comprise one or more additional through holes (304A-304N, 402) forming the channel for the vapor.

9. The heat pipe according to any one of claims 1 to 4, characterized in that, The perforations of the envelope (102, 202, 302) wall extend to a major portion of a circumference of the envelope (102, 202, 302).

10. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to any one of claims 1 to 4, characterized in that, The envelope (102, 202, 302) wall and / or core (108, 206, 504) layer in the compression region (106, 204, 502) are provided with one or more transverse grooves and / or through holes (602).

11. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to any one of claims 1 to 4, characterized in that, A core (108, 206, 504) outer layer is arranged on an inner surface of the flexible bellows (104), the core outer layer being in communication with the core (108, 206, 504) inner layer.

12. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to any one of claims 1 to 4, characterized in that, A second core (108, 206, 504) outer layer is disposed on an outer surface of the envelope (102, 202, 302) in the compression region (106, 204, 502), the second core outer layer being in communication with the core (108, 206, 504) inner layer.

13. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to any one of claims 1 to 4, characterized in that, The condenser end to the evaporator end is flat.

14. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to any one of claims 1 to 4, characterized in that, An outer surface of the flexible bellows (104) is provided with a layer of low thermal conductive material.

15. The heat pipe (100, 200, 300, 400, 500, 600, 700) according to any one of claims 1 to 4, characterized in that, The core (108, 206, 504) comprises one or more of sintered particles, mesh, fibers, and grooves.

16. A method of manufacturing a heat pipe (100, 200, 300, 400, 500, 600, 700), characterized by, Comprising: providing an envelope (102, 202, 302) having a condenser end, an evaporator end, and an adiabatic portion therebetween, disposing a core (108, 206, 504) layer on an inner surface of the envelope (102, 202, 302) for transporting condensed working fluid from the condenser end to the evaporator end, perforating a wall of the envelope (102, 202, 302) in the adiabatic portion to form a passage for vapor, offsetting the wall of the envelope (102, 202, 302) toward a central axis of the envelope (102, 202, 302) to define a compression region (106, 204, 502) in the adiabatic portion, covering the compression region (106, 204, 502) with a flexible bellows (104) to define the passage (112) for vapor, end portions of the flexible bellows (104) being sealed to the wall of the envelope (102, 202, 302) outside the perforations, filling the envelope (102, 202, 302) with the working fluid, sealing the condenser end and the evaporator end of the envelope (102, 202, 302).

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