Boiling type heat conduction pipe and method for manufacturing boiling type heat conduction pipe

Abstract

The invention provides a boiling type heat conduction pipe and a manufacturing method of the boiling type heat conduction pipe, which can maintain high heat conductivity from the boiling type heat conduction pipe to a liquid refrigerant and obtain high heat conduction efficiency. The boiling-type heat transfer pipe is provided with a plurality of rows of fins (11) protruding radially outward from the outer peripheral surface of the pipe body and formed in a spiral shape along the central axis of the pipe body. The fin (11) has a leg section (11a) and a pair of projecting sections (11b, 11c). Cavity parts (13) which are continuous in the circumferential direction are defined between adjacent fins (11) in the tube axis direction. The side wall surface (13b) of the cavity part (13) is provided with a recessed part (23) which is recessed in the direction of the tube axis, and the bottom surface (13a) of the cavity part (13) is provided with a plurality of flat boss parts (17) which press-connect an extension piece extending from the recessed part (23) to the bottom surface (13a).

Description

Technical Field

[0001] This invention relates to a boiling-type heat pipe used in a heat exchanger that boils the refrigerant outside the pipe, and a method for manufacturing the boiling-type heat pipe. Background Technology

[0002] Boiling-type heat pipes are assembled in the evaporators of vapor compression refrigeration machines, such as turbine refrigeration machines and spiral refrigeration machines, which serve as heat exchangers. They are immersed in liquid refrigerants (such as Freon, liquid nitrogen, etc.) to heat the liquid refrigerant to boiling. Various heat-conducting surface shapes have been proposed as such boiling-type heat pipes.

[0003] For example, Patent Document 1 describes a technique that promotes the boiling of the liquid refrigerant within the cavity and promotes the turbulence of the liquid refrigerant and the vaporized medium on the outer surface of the tube, thereby improving thermal conductivity. Furthermore, Patent Document 2 describes a material protrusion extending circumferentially and axially on the side of the fins formed on the outer periphery of the heat-conducting tube (pipe), covering the bottom of the grooves between the fins. This structure increases the proportion of the groove bottom covered by the material protrusion, thereby improving the evaporation efficiency of the liquid refrigerant.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 4-236097

[0007] Patent Document 2: Japanese Patent Publication No. 2015-500456 Summary of the Invention

[0008] The technical problem that the invention aims to solve

[0009] However, in recent years, to address environmental issues such as reducing CO2 emissions, inverter control, which precisely controls the evaporator to heat the liquid refrigerant to boiling point, has been widely adopted in refrigeration equipment to improve energy efficiency. However, even with inverter control, the heat transfer rate from the heat pipe to the liquid refrigerant may not be sufficient depending on operating conditions, requiring further improvements in heat transfer efficiency.

[0010] Based on the technologies described in Patent Documents 1 and 2, a certain degree of improvement in thermal conductivity can be expected. However, in Patent Document 1, the small protrusions are formed at the bottom of the groove, and the corner angle at the root of the protrusion is greater than 90 degrees. In order to promote nucleation boiling within the mold cavity, multiple foaming points with acute angles are needed within the mold cavity. However, with the shape of the small protrusions that only have obtuse angles, it is difficult to ensure multiple foaming points, and a large effect on promoting nucleation boiling cannot be expected.

[0011] On the other hand, the material protrusion described in Patent Document 2 is machined on the side of the fin, which easily makes the corner angle acute. However, since no protrusion is formed at the bottom of the groove where the superheat is highest, the effect of promoting nucleation boiling is small. In addition, the material protrusion extends out significantly into the cavity, hindering the flow of vaporized refrigerant within the cavity. Since refrigerant vapor and refrigerant liquid exist within the cavity, the heat exchange caused by refrigerant evaporation at the gas-liquid interface is greater than the aforementioned effect of nucleation boiling. Therefore, it is difficult to say that the material protrusion in Patent Document 2, which hinders vapor flow, is a suitable shape.

[0012] Therefore, the object of the present invention is to provide a boiling heat pipe that can maintain a high thermal conductivity from the boiling heat pipe to the liquid refrigerant and obtain a high thermal conductivity, as well as a method for manufacturing the boiling heat pipe.

[0013] Technical solutions for solving technical problems

[0014] According to one aspect of the present invention, the following structure is provided.

[0015] (1) A boiling type heat pipe, wherein it has multiple rows of fins that protrude radially outward from the outer periphery of the tube body and are formed in a spiral shape along the central axis of the tube body. Each fin has a leg erected on the outer periphery of the tube body and a pair of protrusions extending in opposite directions in the tube axis direction of the radially outward front end of the leg. Adjacent fins in the tube axis direction are divided into a continuous cavity in the circumferential direction by the protrusion of one fin extending in a close manner to each other, the protrusion of the other fin, and the pair of legs facing each other. A recessed portion is formed on the side wall of the cavity in the tube axis direction. A plurality of flat bosses are formed on the bottom surface of the cavity, which press the extensions extending from the recesses onto the bottom surface.

[0016] (2) (1) In the manufacturing method of the boiling type heat pipe, while pressing the outer periphery of multiple rolling discs onto the outer periphery of the tube body, the outer periphery of the tube body is plastically deformed, and multiple rows of fins protruding radially outward from the outer periphery of the tube body are formed into a spiral shape along the central axis of the tube body. A cutting disc with a cutting edge formed on the outer periphery is inserted between adjacent fins in the tube axis direction of the tube body. The side of the fins is cut out by the cutting edge to form the recess and the extension. After the cutting disc is inserted, a pressing disc is inserted between the fins to press the extension into the bottom of the groove between the fins to form the boss at the bottom of the groove. The front end of the fin after being inserted into the pressing disc is pressed radially inward to form a pair of protrusions.

[0017] Invention Effects

[0018] According to the present invention, a high thermal conductivity can be maintained from the boiling heat pipe to the liquid refrigerant, resulting in a high thermal conductivity. Attached Figure Description

[0019] Figure 1 This is a partial three-dimensional cross-sectional view of the axial section of a boiling heat pipe.

[0020] Figure 2 It is a rough, enlarged cross-sectional view showing a portion of the outer circumference of a boiling heat pipe.

[0021] Figure 3 This roughly indicates a cut using line III-III. Figure 2 The diagram shows a partial cross-sectional perspective view of the fin legs with the protrusions removed.

[0022] Figure 4 It is along Figure 2 The cross-sectional view of line IV-IV is shown.

[0023] Figure 5 This is a cross-sectional view of a boiling heat pipe disposed in a liquid refrigerant, with the cross-section orthogonal to the tube axis.

[0024] Figure 6 This is an explanatory diagram showing the process of liquid refrigerant being heated in the cavity to generate evaporation bubbles.

[0025] Figure 7 This is a schematic front view of the main part of a processing device that forms fins or the like on the outer surface of a tube.

[0026] Figure 8 yes Figure 7 Side view of the processing device shown.

[0027] Figure 9 It is a cross-sectional view schematically showing the machining of the fins by the gear disk and the press-fit disk.

[0028] Figure 10 This is an illustrative diagram schematically showing the state of the fins after being cut by the gear disc.

[0029] Figure 11 This is an explanatory diagram schematically showing the protrusions and cutting blades after the pressing disc is inserted between the fins.

[0030] Figure 12 It is an explanatory diagram that shows the sequence of finishing processes for the fins in a specific area.

[0031] Figure 13 This is a process illustration diagram that roughly shows how the shape of the fins changes in stages due to the processing of the tube body by the disc assembly.

[0032] Figure 14 This is a schematic diagram of a test apparatus used to evaluate the thermal conductivity of boiling heat pipes.

[0033] Figure 15 These are explanatory diagrams showing the dimensions of the fins and ribs as shown in Tables 2 and 3.

[0034] Figure 16 It is a graph showing the relationship between heat flux and total thermal conductivity in Experiment Examples 1 to 3.

[0035] Figure 17 It is a photograph showing a situation where gear disks and pressing disks are inserted between the formed fins, resulting in a boss at the bottom of the groove.

[0036] Figure 18 It means Figure 17 A cross-sectional photograph of the side of the fin shown.

[0037] Figure 19 It is a photograph showing the process of using a gear disk to flatten a pair of protrusions to create embossing. Detailed Implementation

[0038] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0039] <Structure of a Boiling-Type Heat Pipe>

[0040] Figure 1 This is a partial three-dimensional cross-sectional view showing the axial cross-section of the boiling-type heat pipe of the present invention. Figure 2 It is a rough, enlarged cross-sectional view showing a portion of the outer circumference of a boiling heat pipe. Figure 1 The boiling-type heat pipe 100 shown is composed of a metal tube 10 extending in one direction. Multiple rows of fins 11 are formed along the circumferential direction TD on the outer peripheral surface of the tube 10. Figure 2 A continuous circumferential cavity 13 is formed between the fins 11. Additionally, multiple rows of ribs 15 are formed spirally on the inner circumferential surface of the tube body 10. It should be noted that the ribs 15 can be omitted, and the inner circumferential surface of the tube body 10 can be a smooth cylindrical inner surface.

[0041] like Figure 2 As shown, the fins 11 protrude radially outward from the outer circumference of the tube body 10, along... Figure 1 The central axis Lc of the tube 10 shown is formed in a spiral shape. There may be one or more rows of fins 11. In this specification, the tube axis direction of the boiling-type heat pipe 100 is denoted as Ax, the circumferential direction as TD, and the radial direction as RD.

[0042] Each fin 11 has a leg 11a erected on the outer circumferential surface of the tube body 10 and a pair of protrusions 11b and 11c. The radially outer front ends of the legs 11a of the pair of protrusions 11b and 11c are formed into two strands, extending in opposite directions in the tube axis direction Ax. Furthermore, the protrusions 11b and 11c of one fin 11 in a pair of adjacent fins 11 extend from the legs 11a respectively, facing each other with a gap between their respective ends. This creates a continuous circumferential cavity 13.

[0043] Multiple bosses 17 are formed on the bottom surface 13a of the cavity portion 13. Although detailed description will be given later, the bosses 17 are formed by pressing the material or chips obtained from cutting the legs 11a of the fins 11 onto the bottom surface 13a, and are formed to be flat by being in close contact with the bottom surface 13a.

[0044] Figure 3 This roughly indicates a cut using line III-III. Figure 2 The figure shows a partial cross-sectional perspective view of the fin 11 with the legs 11a removed and the protrusions 11b and 11c removed. Figure 3 This is a diagram that models the shapes of fins 11 and bosses 17, and may not necessarily match the actual shapes. For example... Figure 3 As shown, each boss portion 17 is arranged at equal intervals along the circumferential TD direction on the bottom surface 13a of the cavity portion 13. Furthermore, a plurality of protrusions and recesses 19 are formed on the side wall surface 13b of the cavity portion 13. These protrusions and recesses 19 have multiple protrusions 21 that protrude in the tube axis direction Ax and extend radially along the RD direction, and recesses 23 formed between adjacent protrusions 21. The boss portions 17 are formed extending from the recesses 23 of the plurality of protrusions and recesses 19. That is, a recess 23 that is recessed along the tube axis direction Ax is formed on the side wall surface 13b of the cavity portion 13, and a plurality of flat boss portions 17 extending from the recesses 23 and pressed against the bottom surface 13a are formed on the bottom surface 13a of the cavity portion 13. The protrusions 21 protrude from the circumferential TD edge of the recess 23 in the tube axis direction Ax and extend radially. Although details will be described later, for the recessed portion 19, the mark formed by cutting off the leg 11a of the fin 11 becomes the recess 23, and the extension piece (hereinafter also referred to as the cutting piece) formed by this cutting becomes the main material for forming the boss portion 17. In addition, the protrusion 21 includes burrs formed by the plastic deformation of the side wall surface 13b when the leg 11a is cut off.

[0045] Figure 4 It is along Figure 2The cross-sectional view of line IV-IV is shown. The cavity 13 is formed by being surrounded by the protrusion 11b of one fin 11 that extends in a close manner to each other, the protrusion 11c of another fin 11, and a pair of legs 11a, 11a that are opposite to each other.

[0046] The boss portion 17 and the concave-convex portion 19 form multiple steps on the bottom surface 13a and side wall surface 13b of the generally smooth cavity portion 13. Although detailed description will be given later, by providing multiple steps in the cavity portion 13, the corners with steps become foaming points, thereby promoting nucleation boiling.

[0047] In addition, such as Figure 2 As shown, embossing 25 is formed on the outer peripheral surface of the boiling-type heat pipe 100 at predetermined intervals along the circumferential direction. The embossing 25 connects adjacent protrusions 11b and 11c in the tube axis direction Ax by recessing them inward toward the radial direction RD. The connection points of the protrusions 11b and 11c with embossing 25 are provided at multiple locations along the circumferential direction TD of the tube body 10. Here, the connection points are provided across 3 rows of fins 11, but they may also be provided across 1, 2, or 4 or more rows of fins 11.

[0048] The aforementioned connecting portion becomes a narrow section in the cross-section of the cavity 13 in the tube axis direction Ax of the tube body 10, where the cross-sectional area is smaller than that of the section outside the connecting portion. That is, the continuous cavity 13 in the circumferential direction TD becomes a shape that locally narrows at the circumferential position of the embossing 25. Through this narrow section, the cavity 13 is divided into multiple small sections SG along the circumferential direction TD. By arranging the embossing 25 at equal intervals along the circumferential direction, small sections SG are formed at certain intervals in the circumferential direction. It should be noted that the embossing 25 is preferably arranged at certain intervals in the circumferential direction, but is not limited to this; it can be arranged with a specific periodicity or randomly.

[0049] The aforementioned boiling-type heat pipe 100 is made of thermally conductive metal materials such as copper, copper alloy, aluminum, aluminum alloy, iron, stainless steel, titanium, and titanium alloy. In particular, it is more preferably made of a material with high thermal conductivity, such as copper or copper alloy.

[0050] <The function of boiling heat pipes>

[0051] Next, the heat conduction function of the boiling-type heat pipe 100 will be explained.

[0052] Figure 5This is a cross-sectional view of the boiling-type heat pipe 100 disposed within the liquid refrigerant, with the cross-section orthogonal to the pipe axis. The boiling-type heat pipe 100 is disposed within the liquid refrigerant 31 in the evaporator, with the pipe axis horizontal, and heated water 33 is supplied into the boiling-type heat pipe 100. The liquid refrigerant 31 is then heated, generating evaporation bubbles 37 on the bottom surface 13a and sidewall surface 13b of the cavity 13. As indicated by arrow FL, the generated evaporation bubbles 37 move from the lower side of the cavity 13 upwards along the pipe circumference, from the upper side of the boiling-type heat pipe 100 towards the liquid surface of the liquid refrigerant 31 (not shown). Additionally, a portion of the evaporation bubbles 37... Figure 4 The gap between the protrusions 11b and 11c of the fins 11 shown flows outward toward the outside of the cavity 13 and toward the liquid surface of the liquid refrigerant 31.

[0053] Figure 6 This is an explanatory diagram showing the situation where liquid refrigerant 31 is heated in the cavity 13 to generate evaporation bubbles 37. Figure 6 A small section SG of the cavity 13 described above is shown in partial cross-section. The interior of the cavity 13 is... Figure 5 The liquid refrigerant 31 shown is filled. When heating water 33 for heating is supplied into the boiling-type heat pipe 100, as... Figure 4 As shown, the liquid refrigerant 31 inside the cavity 13 is heated by heat conduction Q1 from the outer peripheral surface of the tube 10, i.e., the bottom surface 13a of the cavity 13, and by heat conduction Q2 from the fins 11. At this time, heat transfer from the bottom surface 13a of the cavity 13, which is close to the heated water 33, to the liquid refrigerant 31 becomes particularly active.

[0054] In this structure, a plurality of protrusions 17 are formed on the bottom surface 13a of the boiling-type heat pipe 100. The stepped corners of these protrusions 17 become foaming points, thereby enhancing the nuclear boiling promotion effect. Furthermore, a plurality of irregular portions 19 are formed on the sidewall surface 13b of the cavity portion 13, increasing the surface area of ​​the sidewall surface 13b. This promotes heat transfer from the sidewall surface 13b to the liquid refrigerant 31. Moreover, the corners of the irregular portions 19 become foaming points, further enhancing the nuclear boiling promotion effect. The protrusions 21 and protrusions 17 of the irregular portions 19 are formed by cutting the sidewall surface 13b, thus locally thinning the fins 11 themselves. As a result, due to the reduced heat capacity of the fins 11, heat input from the heat pipe is easily transferred to the fins 11, improving the heat transfer efficiency to the liquid refrigerant 31.

[0055] As described above, when the nuclear boiling promotion effect is enhanced, the generated multiple evaporation bubbles 37 rise toward the liquid surface of the liquid refrigerant 31, so inside the cavity 13, the liquid refrigerant 31 moves circumferentially in a manner that follows the flow of the evaporation bubbles 37.

[0056] Heated by the boiling heat pipe 100, a heating layer 30 of liquid refrigerant 31 is formed in the cavity 13 along the bottom surface 13a and the side wall surface 13b. Figure 4 (The diagram shows a schematic representation of a dispersed area of ​​tiny dots). When the evaporation bubbles 37 of the liquid refrigerant 31 generated by heating pass through the cavity 13, if the inner surface of the cavity 13 is covered by the evaporation bubbles 37 and thus does not come into contact with the liquid refrigerant 31, heat transfer to the liquid refrigerant 31 is hindered. Therefore, it is ideal to form a heating layer 30 such that the inner surface of the cavity 13 is always covered by the liquid refrigerant 31, and to allow the evaporation bubbles 37 to flow along the circumferential TD further inside the heating layer 30.

[0057] According to this method, in Figure 4 The inner side of the heating layer 30 shown, Figure 5 The liquid refrigerant 31 shown moves gradually in the circumferential direction TD in a manner that follows the flow of the evaporator 37, continuously supplying fresh liquid (new liquid refrigerant 31) to the inner surface of the cavity 13. As a result, the heat exchange efficiency within the cavity 13 is improved. In this structure, since the boss 17 is flat due to its contact with the bottom surface 13a, and the unevenness 19 of the sidewall 13b is cut to suppress the amount of protrusion from the sidewall 13b, it is difficult to obstruct the flow of the liquid refrigerant 31 and the evaporator 37 within the cavity 13. Thus, the flow of the liquid refrigerant 31 and the evaporator 37 within the small partition SG becomes smooth.

[0058] Here, the portion of the cavity 13 with embossed 25 formed and the portion without embossed 25 formed are distinguished and are also referred to as the "narrow portion". Figure 2 The protrusions 11b and 11c shown are narrow sections where the embossing 25 is formed, and the other sections are not narrow sections.

[0059] In the cavity 13, a narrow section with embossed 25 is formed, and the protrusions 11b and 11c are recessed radially inward. As a result, the liquid refrigerant 31 flowing in the cavity 13 is stirred in the narrow section, making the flow of the liquid refrigerant 31 turbulent. This also promotes the replacement of fresh liquid and further improves the heat exchange efficiency.

[0060] Furthermore, the narrow section is formed by a radial inward indentation on the radially outer side of the cavity 13, and the radial protrusion on the bottom surface 13a side of the cavity 13 is minimal. Therefore, the flow of the evaporator 37 moving along the bottom surface 13a of the cavity 13 is not obstructed by the narrow section, and the flow resistance of the liquid refrigerant 31 at the narrow section is low. Thus, the gas-liquid two-phase flow of the evaporator 37 and the liquid refrigerant 31 flowing from the lower direction above the boiling heat pipe 100 is not hindered, and the liquid refrigerant 31 can be smoothly supplied to the entire circumference of the cavity 13. Additionally, in the cavity 13 above the boiling heat pipe 100, gas-liquid separation is achieved using the buoyancy of the evaporator 37, promoting the supply of liquid refrigerant 31.

[0061] Furthermore, the cross-sectional shape of the cavity 13 in the axial direction Ax gradually changes along the circumferential direction, reaching its minimum cross-sectional area in the narrow section where the embossing 25 is formed. Therefore, the flow FL of the liquid refrigerant 31 flowing in the cavity 13 narrows in the narrow section, thus increasing flow resistance and decreasing flow velocity. Consequently, in the cavity 13 near the front side of the flow direction in the narrow section, the liquid refrigerant 31 in the heating layer 30 is continuously heated in its original position. As a result, heat input from the inner surface of the cavity 13 to the liquid refrigerant 31 accumulates, promoting the generation of evaporation bubbles 37.

[0062] That is, by arranging multiple narrow sections along the circumference of the cavity 13, multiple small partitions SG are formed in the cavity 13, each separated by a narrow section. The circumferential movement of the liquid refrigerant 31 is suppressed in each small partition SG, and the heating of the liquid refrigerant 31 within each small partition SG is promoted. Thus, by locally heating the liquid refrigerant 31 at multiple locations along the circumference of the cavity 13, the generation efficiency of the evaporation bubble 37 is improved.

[0063] Here, the aforementioned thermal conductivity efficiency is described in further detail. Regarding the flow of the gas-liquid two-phase flow within the heat pipe, examples such as "Refrigerant Condensation - From Basics to Applications" and the Japan Society for Refrigeration and Air Conditioning Professional Book Series (ISBN 978-4889671315), page 277, illustrate a flow path with a rectangular cross-section orthogonal to the pipe axis. In this flow path, the liquid flowing inside the pipe is attracted to the rectangular corners (four corners) due to surface tension, forming a thin liquid film on the straight sections (edges). This thin liquid film reduces the thermal resistance from the heat pipe to the vapor. Therefore, heat movement from the heat-conducting surface becomes easier, improving thermal conductivity. It has been confirmed that the thermal conductivity of such a rectangular pipe is higher than that of a circular pipe with the same flow path cross-sectional area. Although the above-mentioned literature describes the phenomenon of condensation, the same applies to the phenomena of evaporation and boiling.

[0064] On the other hand, in the boiling-type heat pipe 100 of this structure, besides... Figure 4 The cavity portion 13 shown has a corner portion (region Ac), a boss portion 17 is formed on the bottom surface 13a, and a protrusion portion 21 is formed on the side wall surface 13b. Multiple corner portions exist within the flow path. As described above, the corner portions themselves are effective in promoting nucleation boiling. Furthermore, the liquid film is also attracted to the corner portions due to surface tension, thus forming a thin liquid film portion at the edge or surface connected to the corner portion. Specifically, Figure 4 and Figure 6 The area Ap shown can be used as an example of the location where a thin liquid film occurs.

[0065] By forming multiple thin liquid film sections as shown in region Ap, heat conduction from the heat pipe to the liquid refrigerant 31 is promoted. Furthermore, evaporation is facilitated from the gas-liquid interface, thus activating the generation of evaporation bubbles 37, resulting in high thermal conductivity. Thus, the boiling-type heat pipe 100 according to this structure differs from conventional structures with small protrusions at the bottom of the groove within the cavity section 13, having an exceptionally large number of corner sections. Therefore, the area of ​​the edges and surfaces connected to the corner sections is increased, forming a thin liquid film section over a large area, making heat exchange more active. Moreover, since multiple corner sections individually contribute to nucleation boiling, the synergistic effect of the thin liquid film section and the corner sections significantly improves thermal conductivity.

[0066] Based on the above, the boiling-type heat pipe 100 of this structure can synergistically promote the generation of evaporation bubbles 37 through the aforementioned effects of nuclear boiling promotion based on the protrusions 17 and the concave-convex portions 19, the increased heat transfer effect based on the increased surface area, the stirring effect of the liquid refrigerant 31, and the localized heating effect based on the small partitions SG. Therefore, evaporation bubbles 37 can be generated efficiently under all heat flux conditions, thereby improving thermal conductivity.

[0067] <Manufacturing Method of Boiling Type Heat Pipe>

[0068] Next, the manufacturing method of the boiling-type heat pipe 100 will be described.

[0069] Figure 7 This is a front view schematically showing the main part of the processing device for forming fins, etc., on the outer surface of the tube body 10. Figure 8 yes Figure 7 Side view of the processing device shown. Figure 7 The shown support shaft 41 is in the Figure 8The mandrel 43 shown is positioned at a central angle of 120° around its center, and the mandrels are arranged at equal intervals along the circumference. A disc assembly 47, consisting of multiple overlapping circular discs, is coaxially fixed to the three support shafts 41, serving as a tool for forming fins, cavities, and grooves. Each support shaft 41 is supported so that it can rotate around its axis. By rotating these support shafts 41, the tube 10 is pressed against the circumferential end of the disc while rotating in the opposite direction to the rotation of the support shafts 41, thereby forming the fins 11 and the cavity portion 13 through plastic deformation. Furthermore, each support shaft 41 is positioned torsionally relative to the tube axis, thereby allowing the tube 10 to be processed into a spiral shape while being conveyed along the tube axis direction Ax.

[0070] By using the disk assembly 47 configured in this way, spiral fins 11 are formed on the surface of the aforementioned tube body 10. The radially outer front end of the fin 11 is flattened to form various shapes such as protrusions 11b, protrusions 11c, cavities 13, bosses 17, and concave-convex parts 19. Here, an example of three spiral fins 11 formed by three support shafts 41 will be described, but the number of fins 11 is not limited to this and can be adjusted appropriately.

[0071] Figure 7 The disk assembly 47 shown includes rolling disks RD1 to RD13, a cutting disk (gear disk GD1), a pressing disk PD, a connecting disk (gear disk GD2), and finishing disks FD1 to FD5. The rolling disks RD1 to RD13 are used for the staged forming (rolling) of the fins 11. The cutting disk, using gear disk GD1, forms the aforementioned protrusions 19 and the aforementioned extensions, i.e., the cutting blades 51. The pressing disk PD forms bosses 17 by pressing the cutting blades 51 between the fins 11. The connecting disk, using gear disk GD2, forms embossing 25 on the protrusions 11b and 11c. The finishing disks FD1 to FD5 are used to flatten and finish the front ends of the fins. The disk assembly 47 is also formed on three shafts 41, but gear disk GD2 is only disposed on one of the three shafts 41, with spacers on the other two shafts 41 instead of gear disk GD2.

[0072] The rolling discs RD1 to RD13 shown here are examples; the dimensions and number of sheets may be varied depending on the object being formed. Furthermore, a gear disc GD1 is used as the cutting disc here, but it is not limited to this. The cutting disc can be any disc with a cutting edge formed on its outer circumference; it can be a gear other than a spur gear, or a disc with a dedicated cutting edge. Additionally, the connecting disc may be a disc that has protrusions at an appropriate circumferential spacing, replacing the gear disc GD2.

[0073] The pipe body 10 is moved from the upstream side to the downstream side in the processing direction (from...) Figure 7The tubes are conveyed from left to right and fins 11 of a specified radial height are formed sequentially by rolling discs RD1 to RD13 in region SC1. In region SC1, rolling discs RD1 to RD9, whose outer diameter gradually increases in the processing direction along the tube axis Ax, and rolling discs RD10 to RD13, whose fin shape is adjusted at their front ends, are arranged.

[0074] In the next area SC2, a gear disk GD1 and a press-fit disk PD are configured. The gear disk GD1 cuts the side of the formed fin 11. The press-fit disk PD forms a boss 17.

[0075] Figure 9 This is a schematic cross-sectional view illustrating the machining of fins 11 by gear disk GD1 and pressing disk PD. Gear disk GD1 is a disk with spur gears formed on its outer circumference, and its diameter is slightly smaller than that of the preceding rolling disk RD13. When gear disk GD1 is inserted between a pair of fins 11 machined by rolling disk RD13, the side surfaces of fins 11 are removed using the cutting edge and end face of the spur gears, forming cutting blades.

[0076] Here, each disk of the aforementioned disk assembly 47 is a rigid body, but the fins 11 are soft protrusions that are easily elastically deformed. Therefore, when the gear disk GD1 is inserted between the fins 11, the fins 11 elastically deform along the side of the gear disk GD1 while contacting the teeth of the gear disk GD1 and being machined.

[0077] Figure 10 This is an explanatory diagram schematically showing the fin 11 after being cut by the gear disk GD1. The sidewall surface 13b of the fin 11 is cut by the gear disk GD1 to the midpoint of the radial height of the fin 11. As a result, the sidewall surface of the fin 11 is formed as a thin-walled recess 23 and protrusions 21 are formed on both sides of the circumferential TD of the recess 23. These protrusions 21 are formed by plastic deformation accompanying the cutting and protrude in the tube axis direction Ax. The cutting blade 51 that removes the fin 11 extends from the sidewall surface 13b. The protrusions 21 may also contain burrs. The cutting blade 51 is formed protruding in the tube axis direction Ax in the same way as the protrusions 21. The diameter of the gear disk GD1 is set to a size where the outer periphery of the disk does not reach the outer peripheral surface of the tube body 10 (the bottom surface between the fins 11). Therefore, the protrusions 21 are formed between the top of the radially outer front end of the fin 11 and the midpoint of the sidewall surface 13b. In addition, the cutting blade 51 is formed at the lowest height position of the protrusion 21.

[0078] Next, Figure 9 The press-in disc PD shown is inserted between the fins 11, which have protrusions 21 and cutting blades 51.

[0079] Figure 11This diagram schematically illustrates the protrusion 21 and the cutting blade 51 after the press-fit disc PD is inserted between the fins 11. The protrusion 21 is sheared or extended by the press-fit disc PD from a portion protruding from the side wall surface 13b of the fin 11 in the tube axis direction Ax. Additionally, the cutting blade 51 is pressed against the bottom surface of the tube body 10 to form a boss 17. A portion of the cutting debris after the protrusion 21 is sheared or extended is pressed against the bottom surface of the tube body 10 by the press-fit disc PD, forming the boss 17 together with the cutting blade 51. It should be noted that the diameter of the press-fit disc PD is smaller than that of the rolling disc RD13, and it is pressed in to a degree that the cutting blade 51 does not sink into the bottom surface of the tube body 10.

[0080] On the surface of the protrusion 21, multiple uneven scratches are formed by the shearing action of the pressing disc PD. In addition, the boss 17 formed by the cutting disc 51 is pressed tightly against the bottom surface 13a of the cavity 13 by the pressing action of the pressing disc PD, and has multiple steps protruding radially outward from the bottom surface 13a.

[0081] Therefore, as Figure 9 As shown, after the fins 11 with the press-in disk PD inserted are inserted, multiple protrusions 21 and bosses 17 are formed between each other.

[0082] Next, in region SC3, using finishing discs FD1 to FD5 and gear disc GD2, the top of the vertically arranged fins 11 is flattened to form the shape of the cavity portion 13.

[0083] Figure 12 This is an explanatory diagram showing the sequence of finishing processes for fins 11 in region SC3. In step St.1, finishing discs FD1 and FD2 are pressed sequentially onto the top of fins 11, flattening the top of fins 11. As a result, the top of fins 11 extends along the tube axis direction Ax. In step St.2, by pressing finishing disc FD3 between fins 11, a thin-walled portion 53 is formed at the front end of each fin 11. This finishing disc FD3 is positioned... Figure 8 The three support shafts 41 shown are each pressed into the fin 11 by a finishing disc FD. As a result, as shown in St. 3, thin-walled portions 53 are formed on both sides of the fin 11 in the axial direction Ax. It should be noted that a disc with a wavy edge on its outer periphery in the circumferential direction can also be used instead of the finishing disc FD3. In this case, the front end of the fin 11 is split into a Y-shape in the cross section in the axial direction Ax, forming a protruding portion.

[0084] Next, in the St.4 process, the gear disk GD2 is pressed onto the multi-row fins 11, forming a pattern on the circumferential TD at specified intervals. Figure 2The embossing 25 is shown. That is, embossing 25 is formed at the intersection of the tooth tip of the gear disk GD2 and the front end of the fin 11, so that the thin-walled portion 53 extends in the tube axis direction. The gear disk GD2 extends the thin-walled portion 53 to form adjacent protrusions 11b and 11c in the tube axis direction Ax, and these protrusions 11b and 11c are connected to each other by being recessed radially inward at multiple locations along the circumferential direction TD.

[0085] Then, in the St.5 process, the finishing discs FD4 and FD5 are pressed onto the fin 11, so that the thin-walled portion 53 other than the position of the embossing 25 extends in the tube axis direction Ax to form the protrusions 11b and 11c, and the shape of the cavity portion 13 is adjusted.

[0086] Figure 13 This is a process illustration diagram that roughly shows the step-by-step changes in the shape of the fins 11 caused by the processing of the tube body 10 through the disc assembly 47. Figure 13 In the middle, processing is performed sequentially from left to right. First, for the fins 11 formed by the rolling discs RD1 to RD13, a cutting disc 51 is formed by the gear disc GD1, and the cutting disc 51 is pressed into the bottom surface of the groove by the pressing disc PD, thereby forming the boss portion 17. In addition, although not shown in the figure, Figure 11 The sidewall surface 13b of the fin 11 shown has a concave-convex portion 19.

[0087] Next, the top of the fin 11 is flattened using finishing discs FD1 and FD2, and a thin-walled portion 53 is formed using finishing disc FD3. Then, embossing 25 is formed using gear disc GD2, and the shape of the cavity portion 13 is adjusted using finishing discs FD4 and FD5. It should be noted that the ribs 15 on the inner circumferential surface of the tube body 10 are formed sequentially using the same tools (not shown) as the fins 11.

[0088] In the above steps, the fins 11 and the cavity 13 are formed continuously, but the fins 11 and the cavity 13 can also be formed through different processes. Furthermore, the method for forming the fins 11 is not limited to rolling; other processing methods such as cutting can also be used.

[0089]

Example

[0090] Next, the results of evaluating the thermal conductivity of the boiling-type heat pipe 100 using the above structure will be explained.

[0091] Figure 14This is a schematic diagram of a test apparatus for evaluating the thermal conductivity of boiling-type heat pipes. The test apparatus is a structure in which a condenser 61 and an evaporator 63 of a stainless steel shell-and-tube heat exchanger are connected by steam piping and liquid piping. Multiple test heat pipes 65, each with an effective thermal conductivity length of 974 mm, are horizontally arranged in the center of the evaporator 63. Liquid refrigerant 31 is filled inside the evaporator 63, and the test heat pipes 65 are immersed in the liquid refrigerant within the evaporator 63. Heated water stored in a tank 67 is supplied to the test heat pipes 65 of the evaporator 63. The temperature of the heated water supplied to the test heat pipes 65 of the evaporator 63 is regulated to a constant temperature by a cooling brine heat exchanger containing cooling coils 69 disposed within the tank 67 or in the liquid piping, and an electric heater 71. The flow rate of the heated water is regulated to a constant flow rate using an automatic regulating valve and a regulator.

[0092] The heated water is supplied into the test heat pipe 65 from one end, i.e., the inlet side. The heated water discharged from the outlet side of the other end of the test heat pipe 65 returns to the tank 67. Then, the liquid refrigerant 31 heated by the heated water inside the test heat pipe 65 evaporates into refrigerant vapor, which is supplied to the condenser 61 through the vapor piping.

[0093] Multiple heat-conducting tubes 73 (effective length 974 mm) are horizontally arranged in the condenser 61, with O-rings securing the ends of the tubes. A brine solution supplied from tank 75 is provided to each heat-conducting tube 73. The refrigerant vapor from the evaporator 63 is cooled and depressurized by the heat-conducting tubes 73, condensing and liquefying on the outer surface of the tubes. A baffle is provided at the refrigerant vapor inlet of the condenser 61 to prevent direct contact between the refrigerant vapor supplied from the evaporator 63 and the heat-conducting tubes 73. The liquefied liquid refrigerant 31 returns to the evaporator 63 under gravity through liquid piping.

[0094] In the test apparatus described above, the saturated evaporation pressure within the evaporator 63 is measured using an absolute pressure transmitter from the pressure outlet located at the top of the evaporator 63. The inlet and outlet temperatures of the heated water are measured at both ends of the test heat-conducting tube 65 using a pre-calibrated platinum resistance thermometer. Specifically, for the inlet and outlet temperatures of the heated water, a temperature measuring device is used that has been pre-calibrated to ±0.05℃ by combining a platinum resistance thermometer (Pt 100Ω, JIS-A grade) with a temperature correction device (ISO-Tech Millik 0.5mA type 923-0.5MA) and a secondary standard thermometer (resistance thermometer). This device is set at both ends of the test heat-conducting tube 65 for measurement. The platinum resistance thermometer is positioned so that its front end forms the center of the flow path at both ends of the test heat-conducting tube 65. The flow rate of the heated water is measured using a volumetric flow meter located at the outlet side of the test heat-conducting tube 65. The test conditions are shown in Table 1. It should be noted that, regarding the number of heat conduction tubes in the evaporator test, the preliminary verification confirmed that there was no change in the tendency between 1 tube and 3 tubes.

[0095] Table 1

[0096]

[0097] The overall thermal conductivity Ko [kW / (m²] based on the outer surface area Ao of the tube 2 ·K)], heat conductance of heating water Qs [kW], outer surface area of ​​the pipe Ao [m 2 The logarithmic mean temperature difference ΔTm [K] between the refrigerant and the heated water is shown in equations (1) to (4) below. It should be noted that the outer surface area Ao of the tube is based on a smooth surface assumed according to the outer diameter of the fins of the test heat-conducting tube.

[0098]

[0099] Here, Ws is the heating water flow rate [kg / s], and cp s It is the specific heat of heating water [kJ / (kg·K)], T s,in It is the inlet temperature of the heated water [°C], T s,out Here, Tr is the outlet temperature of the heated water (°C), Do is the outer diameter of the fins of the test heat pipe (m), and L is the effective length of the heat pipe (m). The refrigerant saturation temperature Tr is obtained from the measured saturated vapor pressure using the refrigerant thermophysical property database (REFPROP Ver.10). The heat flux qo based on the external heat transfer area is [kW / m²]. 2 ] is defined by equation (5).

[0100]

[0101] In addition, the heat transfer rate ho [kW / (m²] based on the external heat conduction area of ​​the pipe 2 ·K)] is defined by equation (6).

[0102]

[0103] Assuming the thermal conductivity h on the inside of the tube i [kW / (m 2 ·K)〕 is consistent with the expression in the form of Dittus-Boelter, and is defined by equation (7).

[0104]

[0105] Here, κ s It is the thermal conductivity of heated water [kW / (m·K)], Pr s This is the Prandtl number for heating water. Additionally, the Reynolds number (Re) for heating water... s The representative length is set as the maximum inner diameter D of the machining section. imax [m] is defined by equation (8).

[0106]

[0107] It should be noted that the Dittus-Boelter coefficient DBC in the formula... i The values ​​were obtained using preliminary experiments conducted using the Wilson-Plot method.

[0108] Tables 2 and 3 show the dimensions and number of fins of the heat-conducting tubes used in Experimental Examples 1 to 3.

[0109] Figure 15 This is an explanatory diagram showing the dimensions of fins 11 and ribs 15 as shown in Tables 2 and 3.

[0110] Table 2

[0111]

[0112] Table 3

[0113]

[0114] In each of the test heat pipes, the aforementioned fins and cavities are formed on the outer circumferential surface of the pipe, and the ribs shown in Table 3 are formed on the inner circumferential surface of the pipe. The test heat pipe of Test Example 1 is the boiling type heat pipe 100 of the above embodiment. The test heat pipes of Test Examples 2 and 3 are test heat pipes used for comparison with Test Example 1, and both have embossed protrusions 11b and 11c forming the cavity 13 that are flattened at equal intervals along the circumferential direction, but do not have bosses 17 and concave-convex portions 19. Test Example 2 was prepared using the test conditions of Test Example 1 in Japanese Patent Application Publication No. 2021-134952, and Test Example 3 was prepared using the test conditions described in Japanese Patent Application Publication No. 2017-20736.

[0115] For the heat-conducting tubes tested in Examples 1-3 above, the overall thermal conductivity Ko, representing the thermal conductivity from the radially inner side of the tube's inner circumference to the radially outer side of the tube's outer circumference, was determined. The results are shown below. Figure 16 .

[0116] Figure 16 This is a graph showing the relationship between heat flux qo and total thermal conductivity Ko in experimental examples 1-3. For example... Figure 16 As shown, across the entire region of heat flux, the overall thermal conductivity of Experimental Example 1 is greater than that of Experiments 2 and 3. In the cases of Experiments 2 and 3, the maximum overall thermal conductivity is 7.5 kW / (m²). 2 The overall thermal conductivity was around K), but in the case of Experimental Example 1, the overall thermal conductivity increased significantly with the increase of heat flux, with the heat flux being around 20 kW / m². 2 Reaching 8kW / (m 2 K). For example, at a heat flux of 40 kW / m². 2 Before and after, the overall heat transfer coefficient of Experimental Example 1 was more than 1.3 times that of Experimental Example 3, and the difference between Experimental Example 1 and Experimental Examples 2 and 3 increased significantly. Therefore, the heat exchanger using the experimental heat pipe (boiling type heat pipe 100) of Experimental Example 1 can maintain a high heat transfer rate from the heat pipe to the liquid refrigerant and can carry out efficient heat transfer throughout the entire operating range.

[0117] Next, the results of cutting the heat pipe of Experiment Example 1 and observing the shape of the heat pipe surface will be explained.

[0118] Figure 17 This is a photograph showing a situation where gear disks GD1 and press-in disks PD are inserted between the formed fins 11, resulting in a boss 17 at the bottom of the groove. Figure 17 Equivalent to Figure 13 The location of region P1. For example... Figure 17 As shown, multiple protrusions 17 are formed in the grooves between the fins 11, and steps rising from the bottom of the groove are formed on the outer edge of the protrusions 17. The corners with steps become foaming points, which enhance the effect of promoting nucleoboiling.

[0119] Figure 18 It means Figure 17 A cross-sectional photograph of the side of the fin 11 is shown. On the side of the fin 11, a concave-convex portion 19, including the aforementioned protrusions 21 and recesses 23, is formed according to the tooth spacing of the gear disk. The circumferential spacing between adjacent pairs of protrusions 21 increases as they move further outward radially. Here, if the expansion angle of a pair of protrusions 21 is set as θp, the circumferential spacing between a pair of protrusions 21 is set as Pp, the indentation depth of the gear disk tooth tip (i.e., the depth from the outer periphery of the fin 11 to the root of the recess 23) is set as tp, and the circumferential length of the root is set as Wp, then the dimensions are as follows.

[0120] θp: 31.9°

[0121] Pp: 0.89mm

[0122] TP: 0.37mm

[0123] Wp: 0.21mm

[0124] The extension angle θp is in the range of 20° to 50°, which facilitates the formation of the protrusion 21 and enables the stirring effect of the liquid flow within the cavity 13, thereby improving heat exchange efficiency. Therefore, this is preferable. In addition, if the ratio of the height Hf to the depth tp of the fin 11, tp / Hf, is in the range of 0.5 to 0.9, the material volume used to cut the fin 11 to form the boss 17 is appropriate, and the boss 17 of the desired size can be formed. Therefore, this is also preferable.

[0125] Figure 19 This is a photograph showing the process of flattening a pair of protrusions 11b and 11c with a gear disk GD2 to form embossing 25. Figure 19 Corresponding to Figure 13 The location of region P2. For example... Figure 19 As shown, the surface of the tube body 10 is covered by protrusions 11b and 11c formed by multiple rows of fins in the circumferential direction TD. The protrusions 11b and 11c formed by three rows of fins are flattened in one step by the gear disk GD2 to form a connected embossed pattern 25.

[0126] Here, if the circumferential spacing of the embossing 25 is set to Pe, the circumferential width of the embossing 25 is set to We, the distance between embossings is set to Lh, and the gap between the protrusions 11b and 11c is set to Lg, then the dimensions are as follows.

[0127] Pe: 0.619mm

[0128] We: 0.174mm

[0129] Lh: 0.408mm

[0130] Lg: 0.106mm

[0131] The circumferential spacing Pe of the embossing 25 and the inter-embossing distance Lh are preferably longer than the circumferential spacing Pp of the pair of protrusions 21 (Pe > Pp, Lh > Pp). Thus, by arranging at least one concave-convex portion 19 in a partition of the cavity portion 13 divided by the embossing 25, the heat conduction effect can be improved.

[0132] Thus, the present invention is not limited to the above-described embodiments. Combining the various structures of the embodiments with each other, making changes and applications based on the description in the specification and well-known technologies by those skilled in the art are also contemplated by the present invention and are included within the scope of protection.

[0133] As stated above, the following matters are disclosed in this specification.

[0134] (1) A boiling type heat pipe having multiple rows of fins that protrude radially outward from the outer periphery of the pipe body and are formed in a spiral shape along the central axis of the pipe body. Each fin has a leg erected on the outer periphery of the pipe body and a pair of protrusions extending in opposite directions in the direction of the pipe axis of the leg. Adjacent fins in the direction of the pipe axis are divided into a continuous cavity in the circumferential direction by the protrusion of one fin extending in a close manner to each other, the protrusion of the other fin, and the pair of legs facing each other. A recessed portion is formed on the side wall of the cavity in the direction of the pipe axis. A plurality of flat bosses are formed on the bottom surface of the cavity, whereby an extension plate extending from the recess is pressed against the bottom surface.

[0135] According to this boiling-type heat pipe, multiple protrusions formed on the bottom surface of the cavity section enable efficient heat transfer to the outer side of the heat pipe via protrusions near the center of the heat pipe. Furthermore, the increased surface area of ​​the bottom surface within the cavity section due to the protrusions also facilitates efficient heat transfer. Additionally, the protrusions are formed with steps that bulge from the bottom surface of the cavity section, and the multiple corners of these steps become foaming points, promoting nucleated boiling. As a result, the liquid refrigerant moves in a manner following the flow of the evaporating bubbles, continuously supplying fresh liquid to the bottom surface of the cavity section, enabling efficient heat transfer. Moreover, since the protrusions are formed from extensions extending from the sidewall of the cavity section, the volume of the protrusions can be ensured without the need for additional material. Furthermore, the thin-walled nature of the fins facilitates heat input from the heat pipe to the entire fin, improving the efficiency of heat transfer to the liquid refrigerant.

[0136] (2) According to (1), a boiling type heat pipe is provided, wherein a plurality of protrusions are formed on the side wall of the cavity portion, and the plurality of protrusions have protrusions that protrude from the recesses toward the pipe axis and extend radially.

[0137] According to this boiling-type heat pipe, the surface area is increased due to the unevenness of the sidewalls, thereby promoting heat transfer from the sidewalls. In addition, the corners of the unevenness become foaming points, enhancing the nucleation boiling effect.

[0138] (3) According to (1) or (2) the boiling type heat pipe, wherein the connecting portion that connects the adjacent protrusions in the tube axis direction by being concave to each other in the radial direction is provided in a plurality of locations along the circumferential direction, the connecting portion being a narrow portion in the cross section of the cavity in the tube axis direction with a cross section area smaller than the cross section area other than the connecting portion, the cavity being divided into a plurality of small sections by the narrow portion along the circumferential direction.

[0139] According to this boiling-type heat pipe, multiple connecting points are arranged circumferentially to link the protrusions together, thereby forming narrow sections in the cavity. As a result, the cross-sectional area of ​​the pipe along the axial direction is smaller at the connecting points than at other circumferential locations, narrowing the flow of liquid refrigerant. This inhibits the flow of liquid refrigerant, making it easier to heat it at the same location and promoting the formation of evaporation bubbles. In other words, the liquid refrigerant is locally heated at multiple circumferential locations within the cavity, efficiently generating evaporation bubbles.

[0140] (4) The boiling type heat pipe according to (3), wherein the connecting portion is provided across multiple rows of the cavity portions.

[0141] According to this boiling-type heat pipe, each small section, divided circumferentially in the multi-row cavity section, is formed equally. Thus, the liquid refrigerant is heated under the same conditions, enabling less uneven heat exchange.

[0142] (5) A boiling heat pipe according to any one of (1) to (4), wherein the boss portion is disposed at equal intervals along the circumference on the bottom surface of the cavity portion.

[0143] According to this boiling-type heat pipe, the arrangement of the bosses in the cavity becomes more uniform, which can reduce the generation of uneven heat conduction.

[0144] (6) A method for manufacturing a boiling heat pipe, which is a method for manufacturing a boiling heat pipe according to any one of (1) to (5), wherein, while pressing the outer periphery of multiple rolling discs onto the outer periphery of the tube body, the outer periphery of the tube body is plastically deformed, and multiple rows of fins protruding radially outward from the outer periphery of the tube body are formed into a spiral shape along the central axis of the tube body. A cutting disc with a cutting edge formed on the outer periphery is inserted between adjacent fins in the tube axis direction of the tube body, and the side surface of the fins is cut out by the cutting edge to form the recess and the extension piece. After the cutting disc is inserted, a pressing disc is inserted between the fins to press the extension piece into the bottom of the groove between the fins to form the boss at the bottom of the groove. The front end of the fin after being inserted into the pressing disc is pressed radially inward to form a pair of the protrusions.

[0145] According to the manufacturing method of this boiling-type heat pipe, multiple bosses are formed by cutting the side of the fins and pressing the extension plates into the bottom of the groove. This allows for efficient heat transfer to the outside of the heat pipe through the bosses near the center of the heat pipe. Furthermore, by increasing the surface area of ​​the bottom surface within the cavity through the formation of the bosses, efficient heat transfer is also achieved. In addition, steps formed by bulging from the bottom surface of the cavity are created in the bosses, and the multiple corners of these steps become foaming points, promoting nucleated boiling. As a result, the liquid refrigerant moves in a manner following the flow of the evaporating bubbles, continuously supplying fresh liquid to the bottom surface of the cavity, enabling efficient heat transfer. Moreover, since the bosses are formed by extension plates extending from the sidewall of the cavity, the volume of the bosses can be ensured without the need for additional material. Furthermore, the fins themselves are thin-walled, making it easier for the heat input of the heat pipe to be transferred to the entire fin, thereby improving the heat transfer efficiency to the liquid refrigerant.

[0146] (7) The method for manufacturing a boiling heat pipe according to (6) wherein, by inserting the cutting disc, a plurality of protrusions are formed on the side wall of the cavity, the plurality of protrusions having protrusions that protrude from the recesses toward the pipe axis and extend radially, and the pressing disc cuts off a portion of the protruding protrusions.

[0147] According to the manufacturing method of this boiling-type heat pipe, the surface area is increased due to the unevenness of the sidewall, thereby promoting heat transfer from the sidewall. Furthermore, the corners of the unevenness become foaming points, enhancing the nucleation boiling effect. Moreover, by inserting the pressing plate, a portion of the protrusions extending from the side of the fins is removed, maintaining the flowability of the liquid refrigerant within the cavity.

[0148] (8) The method for manufacturing a boiling heat pipe according to (6) or (7), wherein the cutting disk is a gear disk with straight teeth formed on its outer periphery.

[0149] According to the manufacturing method of this boiling-type heat pipe, by using a common spur gear as the cutting disk, the equipment cost can be reduced.

[0150] (9) A method for manufacturing a boiling-type heat pipe according to any one of (6) to (8), wherein adjacent protrusions in the tube axis direction are connected to each other by being recessed radially inward at multiple locations along the circumferential direction, forming a narrow portion in the cross-section of the cavity in the tube axis direction with a cross-sectional area smaller than the cross-sectional area other than the connecting portion, and the cavity is divided into multiple small sections along the circumferential direction.

[0151] According to the manufacturing method of this boiling-type heat pipe, narrow sections are formed in the cavity by providing connecting portions at multiple locations along the circumference, where the protrusions are connected by recesses. These narrow sections become uniformly spaced circumferentially, allowing the liquid refrigerant to be heated under the same conditions. Thus, the liquid refrigerant is heated uniformly circumferentially, enabling heat exchange with less unevenness. Furthermore, by forming a closed space, the cross-sectional area of ​​the pipe axis is smaller at the connecting portions than at other circumferential locations, narrowing the flow of the liquid refrigerant. This suppresses the flow of the liquid refrigerant, making it easier to heat it at the same location and promoting the formation of evaporation bubbles. In other words, the liquid refrigerant is locally heated at multiple locations along the circumference within the cavity, efficiently generating evaporation bubbles.

[0152] Explanation of reference numerals in the attached figures

[0153] 10: Pipe body

[0154] 11: Fins

[0155] 11a: Legs

[0156] 11b, 11c: Protruding parts

[0157] 13: Cavity

[0158] 13a: Bottom surface

[0159] 13b: Sidewall

[0160] 15: Ribs

[0161] 17: Bossed section

[0162] 19: Uneven parts

[0163] 21: Protrusion

[0164] 23: concave part

[0165] 25: Embossing

[0166] 30: Heating layer

[0167] 31: Liquid refrigerant

[0168] 33: Add hot water

[0169] 37: Evaporation bubble

[0170] 41: Support shaft

[0171] 43: Mandrel

[0172] 47: Disk Set

[0173] 51: Cutting disc (extension disc)

[0174] 53: Thin-walled section

[0175] 61: Condenser

[0176] 63: Evaporator

[0177] 65: Test heat pipe

[0178] 67: Can

[0179] 69: Cooling coil

[0180] 71: Electric heater

[0181] 73: Heat pipe

[0182] 75: Can

[0183] 100: Boiling-type heat pipe

[0184] RD1~RD13: Rolling Dies

[0185] GD1, GD2: Gear disks

[0186] PD: Press-in disc

[0187] FD1~FD5: Finishing discs.

Claims

1. A boiling-type heat pipe, characterized in that, It has multiple rows of fins that protrude radially outward from the outer periphery of the tube and are formed in a spiral shape along the central axis of the tube. The fins each have legs that are vertically arranged on the outer circumferential surface of the tube body, and a pair of protrusions whose radially outer front ends extend in opposite directions in the tube axis direction of the tube body. In the axial direction, adjacent fins are separated by a continuous circumferential cavity, enclosed by the protrusions of one fin extending close to each other, the protrusions of the other fin, and a pair of opposing legs. A recessed portion is formed on the side wall surface of the cavity in the direction of the tube axis. A plurality of flat bosses are formed on the bottom surface of the cavity, which press the extension piece extending from the recess onto the bottom surface.

2. The boiling-type heat pipe according to claim 1, characterized in that, Multiple protrusions and recesses are formed on the sidewall of the cavity, and each protrusion and recess has a protrusion that protrudes from the recess toward the tube axis and extends radially.

3. The boiling-type heat pipe according to claim 1, characterized in that, The connecting portions, which connect adjacent protrusions in the axial direction of the tube by being recessed radially inward to each other, are provided at multiple locations along the circumferential direction. The connecting portion is a narrow section in the cross-section of the cavity in the tube axis direction, whose cross-sectional area is smaller than that of the section outside the connecting portion. The cavity is divided into multiple small sections along the circumferential direction by the narrow section.

4. The boiling-type heat pipe according to claim 2, characterized in that, The connecting portions, which connect adjacent protrusions in the axial direction of the tube by being recessed radially inward to each other, are provided at multiple locations along the circumferential direction. The connecting portion is a narrow section in the cross-section of the cavity in the tube axis direction, whose cross-sectional area is smaller than that of the section outside the connecting portion. The cavity is divided into multiple small sections along the circumferential direction by the narrow section.

5. The boiling-type heat pipe according to claim 3, characterized in that, The connecting portion is provided across multiple rows of the cavity portions.

6. The boiling-type heat pipe according to claim 4, characterized in that, The connecting portion is provided across multiple rows of the cavity portions.

7. The boiling-type heat pipe according to any one of claims 1 to 6, characterized in that, The bosses are evenly spaced along the circumference on the bottom surface of the cavity.

8. A method for manufacturing a boiling-type heat pipe, which is the method for manufacturing a boiling-type heat pipe according to claim 1, characterized in that, While pressing the outer periphery of multiple rolling discs onto the outer periphery of the tube, the outer periphery of the tube is plastically deformed, forming multiple rows of fins protruding radially outward from the outer periphery of the tube into a spiral shape along the central axis of the tube. A cutting disc with cutting edges formed on its outer periphery is inserted between adjacent fins in the axial direction of the tube body. The cutting edges are used to cut the side surfaces of the fins to form the recesses and the extensions. After the cutting disc is inserted, a pressing disc is inserted between the fins to press the extension pieces into the bottom of the grooves between the fins, thereby forming the boss at the bottom of the grooves. The front end of the fin, after being inserted into the pressing plate, is pressed radially inward to form a pair of protrusions.

9. The method for manufacturing a boiling-type heat pipe according to claim 8, characterized in that, By inserting the cutting disc, a plurality of protrusions and recesses are formed on the sidewall surface of the cavity. These protrusions and recesses have protrusions that project from the recesses toward the tube axis and extend radially. The pressing disc removes a portion of the protruding protrusion.

10. The method for manufacturing a boiling-type heat pipe according to claim 8, characterized in that, The cutting disk is a gear disk with straight teeth formed on its outer periphery.

11. The method for manufacturing a boiling-type heat pipe according to claim 9, characterized in that, The cutting disk is a gear disk with straight teeth formed on its outer periphery.

12. The method for manufacturing a boiling-type heat pipe according to any one of claims 8 to 11, characterized in that, The protrusions adjacent to each other in the tube axis direction are connected by being recessed radially inward at multiple locations along the circumference, forming a narrow portion in the cross-section of the cavity in the tube axis direction with a cross-sectional area smaller than the cross-sectional area outside the connection location, and the cavity is divided into multiple small sections along the circumference.

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