Evaporator suitable for flat plate type LHP capillary core integrated sintering process and integrated forming process of evaporator

Abstract

The invention belongs to the technical field of flat plate type loop heat pipes, and particularly relates to an evaporator suitable for a flat plate type LHP capillary core integrated sintering process and an integrated forming process of the evaporator. Comprising a shell, a heating surface arranged at the bottom of the shell, a steam cavity arranged in the shell, a capillary core, a plurality of heat conduction ribs, an annular shrinkage rib and a compensation cavity, the steam cavity is provided with a steam outlet, and the compensation cavity is provided with a liquid inlet. The heat-conducting ribs are distributed on the heating surface at intervals, the annular shrinkage ribs are arranged on the heating surface around the heat-conducting ribs, and gaps are reserved between the annular shrinkage ribs and the heat-conducting ribs and between the annular shrinkage ribs and the shell; a gap between the annular contraction rib and the heat conduction rib forms a steam cavity; the capillary core is arranged between the heat conduction rib and the compensation cavity, makes contact with the upper surfaces of the capillary core and the heat conduction rib, the outer surface of the annular contraction rib and the inner surface of the shell and is used for separating the steam cavity from the compensation cavity. Good heat conductivity, sealing performance and reliability of the evaporator can be achieved, and therefore the suitability of large-scale application is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of flat-plate loop heat pipes, and in particular relates to an evaporator suitable for a flat-plate LHP capillary wick integrated sintering process and an integrated molding process thereof. Background Art

[0002] As a highly efficient passive heat transfer element, the LHP (flat loop heat pipe) can effectively address the thermal management constraints faced by the rapid development of electronic devices. The LHP's operating principle is as follows: the evaporator, as the component in direct contact with the heat source, transfers heat to the surface of the capillary wick via heat conduction. The liquid working fluid adhering to the capillary wick undergoes a phase change upon heating, producing vapor. As the vapor accumulates, the pressure differential across the wick gradually increases, eventually reaching the working fluid circulation condition within the system. At this point, the superheated vapor enters the condenser via the steam channel and the steam pipeline, where it is condensed into a subcooled liquid working fluid and returned to the compensation chamber via the liquid pipeline. Finally, under the action of capillary suction, the liquid working fluid returns to the capillary wick surface and begins the next phase change. As this process continues, the working fluid begins to establish a stable circulation within the system, achieving heat transfer and transmission. The LHP manufacturing process generally involves determining the heat source size, designing the wick dimensions, and then, after directly sintering or cutting the resulting wick, determining the evaporator structure and system assembly based on its final dimensions. Examples include wire mesh wicks and their pressed parts, and directly sintered metal powder wicks. Because wick production typically takes a long time and is complex, and because wick structures vary from mold to mold, evaporators must be individually matched, making mass production difficult.

[0003] The LHP capillary wick sintering process primarily involves pre-loading the wick into the evaporator before sintering. This process allows for precise alignment with evaporators of varying shapes and sizes, is simple to operate, and offers low cost. However, there are several challenges: Firstly, the lack of a steam channel between the wick and the heating surface hinders the timely discharge of steam; secondly, the wick shrinks after sintering, creating a gap between the wick and the evaporator housing. This can easily cause the wick to fall off, leading to system startup failure.

[0004] Therefore, it is necessary to provide an improved evaporator suitable for the flat-plate LHP capillary wick integrated sintering process to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide an evaporator suitable for the integrated sintering process of a flat-plate LHP capillary wick and its integrated molding process, which can solve the complex process of designing a corresponding evaporator structure according to the capillary wick structure after the traditional capillary wick is sintered, so that there is no need for a one-to-one match between the capillary wick and the evaporator, while achieving good heat transfer, sealing and reliability of the evaporator, and improving the adaptability of large-scale applications.

[0006] To achieve the above-mentioned object, the present invention provides a flat-plate loop heat pipe evaporator, comprising a shell, a heating surface arranged at the bottom of the shell, a steam chamber arranged inside the shell, a capillary wick, a plurality of heat-conducting ribs, an annular contraction rib and a compensation chamber;

[0007] The steam chamber is provided with a steam outlet, and the compensation chamber is provided with a liquid inlet;

[0008] The heat-conducting ribs are distributed on the heating surface at intervals, and the annular shrinkage ribs are arranged on the heating surface around the heat-conducting ribs, with gaps between the annular shrinkage ribs and the heat-conducting ribs and the shell; the gaps between the annular shrinkage ribs and the heat-conducting ribs form the steam chamber;

[0009] The capillary core is arranged between the heat-conducting rib and the compensation cavity, and the capillary core contacts the upper surface of the heat-conducting rib, the outer surface of the annular contraction rib and the inner surface of the shell, so as to separate the steam cavity and the compensation cavity.

[0010] Furthermore, the steam outlet is provided on the lower side wall of the shell and is communicated with the steam chamber, and the liquid inlet is provided on the upper side wall of the shell and is communicated with the compensation chamber.

[0011] Furthermore, the end of each heat-conducting rib is spaced equidistant from the annular contraction rib, and the gaps between the heat-conducting ribs form steam channels, which are communicated with the steam chamber.

[0012] Furthermore, the height of the annular shrinkage rib is higher than the thickness of the heat-conducting rib; the top of the capillary wick is higher than the top of the annular shrinkage rib, so as to completely cover the annular shrinkage rib.

[0013] Furthermore, the height and spacing of each heat-conducting rib are equal, and the height is less than 3mm, and the spacing is less than the thickness and width of the heat-conducting rib; further, the thickness of the heating surface is 0.5mm to 2mm. The height of the annular shrinkage rib (5) is 6mm to 7mm, and the rib width is 0.5mm to 1mm.

[0014] Furthermore, a spring support frame is provided above the capillary core, a cover plate is provided on the top of the shell, the spring support frame and the cover plate are connected with a spring for pressing the capillary core, and the cross-sectional area of ​​the spring support frame is smaller than the cross-sectional area of ​​the cover plate.

[0015] The present invention further provides an integrated molding process for the flat-plate loop heat pipe evaporator as described in any one of the above, comprising:

[0016] Processing the initial structure of the evaporator, the initial structure comprising a shell, a heating surface disposed at the bottom of the shell, an annular shrinkage rib disposed on the heating surface, and a plurality of heat-conducting ribs;

[0017] Filling the gaps between the heat-conducting ribs and the gaps between the heat-conducting ribs and the annular shrinkage ribs with sodium carbonate powder and pressing them tightly;

[0018] Filling the capillary wick powder onto the sodium carbonate powder and between the annular shrinkage rib and the shell, pressing tightly, and then vacuum sintering; wherein the filling height of the capillary wick powder is higher than the height of the annular shrinkage rib;

[0019] After sintering is completed, the sodium carbonate powder is removed to obtain an evaporator.

[0020] Furthermore, the sodium carbonate powder is removed by washing, dissolving and removing with water.

[0021] Furthermore, the capillary wick powder comprises nickel powder, copper powder and other powders having a melting point lower than that of the shell material.

[0022] Furthermore, the molding process also includes: placing a spring support frame and a spring on the top of the capillary core, and placing a cover plate above the spring and then welding them.

[0023] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technology:

[0024] 1. The present invention forms a steam chamber and steam channels by adding heat-conducting ribs to the evaporator heating surface. Simultaneously, shrinkage ribs are added to the heating surface to address the shrinkage problem of the capillary wick after sintering, ensuring that the capillary wick can separate the steam chamber and the compensation chamber, preventing system leakage, stabilizing system operation, and enhancing the system's heat transfer performance.

[0025] 2. This invention employs thermally conductive ribs and contraction ribs, pre-filled with sodium carbonate powder between the ribs. After sintering, the ribs are rinsed with clean water to dissolve the sodium carbonate powder, forming steam channels and a steam cavity, reducing flow resistance on the steam side. The provision of contraction ribs specifically for the capillary wick during sintering eliminates the shrinkage issue associated with sintering the capillary wick, ensuring a sealed seal between the steam cavity and the compensation chamber, making it particularly suitable for use as an evaporator in LHP.

[0026] 3. During LHP operation, the capillary wick must maintain close contact with the thermally conductive ribs on the evaporator's heating surface to reduce the contact thermal resistance between the capillary wick and the heating surface. The height of the sodium carbonate powder in the present invention is slightly lower than the height of the thermally conductive ribs, ensuring close contact between the capillary wick and the ribs after filling. A spring support structure is also added to tightly fit the capillary wick and the ribs using elastic force, thereby reducing the contact thermal resistance.

[0027] 4. This invention utilizes an integrated structure in which the heating surface, heat-conducting ribs, contraction ribs, and shell are directly machined. This eliminates the need for welding between the heating surface and shell, reduces the thickness of the heating surface, and allows for faster transfer of heat from the heat source into the evaporator, thereby lowering the system's thermal resistance. Furthermore, the integrated structure of the heat-conducting ribs and heating surface reduces the contact thermal resistance between the heat source and the capillary wick, improving the evaporator's heat transfer coefficient while ensuring pressure-bearing performance.

[0028] 5. The evaporator of the present invention is flexible and can theoretically be configured into any geometric shape. This allows the evaporator to accommodate multiple heat sources over a large area or irregularly shaped heat sources. This breaks the limitations of traditional square and round evaporators, providing more design options and adaptability.

[0029] 6. From a process perspective, the cleaned evaporator of the present invention, after metal processing, can be directly sintered in one piece. This sintering process offers multiple advantages, including short processing cycles, simple operation, low cost, repeatable operation, and large-scale production. These features make the entire process more convenient and flexible. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of the flat-plate loop heat pipe evaporator of the present invention;

[0031] Figure 2 Schematic diagram of the structure of a flat-plate loop heat pipe evaporator without a capillary wick;

[0032] Figure 3 is a cross-sectional view of a flat-plate loop heat pipe evaporator without a capillary wick;

[0033] Figure 4 A cross-sectional view of a flat-plate loop heat pipe evaporator with a capillary wick after integral sintering.

[0034] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0035] 1- heating surface, 2- heat-conducting ribs, 3- steam channels, 4- steam chamber, 5- contraction ribs, 6- capillary wick, 7- spring support frame, 8- shell, 9- steam outlet, 10- liquid inlet, 11- compensation chamber, 12- cover plate. DETAILED DESCRIPTION

[0036] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0037] See also Figure 1-4 The present invention provides a flat-plate loop heat pipe evaporator comprising a housing 8, a heating surface 1 disposed at the bottom of the housing 8, a steam chamber 4 disposed within the housing 8, a capillary wick 6, a plurality of heat-conducting ribs 2, an annular contraction rib 5, and a compensation chamber 11. The steam chamber 4 is provided with a steam outlet 9, and the compensation chamber 11 is provided with a liquid inlet 10. The steam chamber 4 and the compensation chamber 11 are separated by the capillary wick 6 and are located at the bottom and top of the housing 8, respectively.

[0038] Several heat-conducting ribs 2 are distributed at intervals on the heating surface 1, and an annular shrinkage rib 5 is arranged on the heating surface 1 around the heat-conducting rib 2, with gaps left between the heat-conducting rib 2 and the shell 8; the gap between the annular shrinkage rib 5 and the heat-conducting rib 2 forms the steam chamber 4.

[0039] The capillary wick 6 is arranged between the heat-conducting rib 2 and the compensation chamber 11, and the capillary wick 6 contacts the upper surface of the heat-conducting rib 2, the outer surface of the annular contraction rib 5 and the inner surface of the shell 8, for separating the steam chamber 4 and the compensation chamber 11.

[0040] This arrangement, by adding heat-conducting ribs 2 to the evaporator heating surface 1, forms a steam chamber 4 and steam channels 3. Simultaneously, adding shrinkage ribs 5 to the heating surface 1 addresses the shrinkage problem of the capillary wick after sintering, ensuring that the capillary wick 6 can separate the steam chamber 4 from the compensation chamber 11, preventing system leakage, stabilizing system operation, and enhancing the system's heat transfer performance.

[0041] In particular, the cross-sectional shape of the heating surface 1 is circular, elliptical, or polygonal. The evaporator of the present invention offers flexibility and can theoretically be configured into any geometric shape. This allows the evaporator to accommodate large areas with multiple heat sources or irregularly shaped heat sources. This overcomes the limitations of traditional square and circular evaporators, providing greater design options and adaptability.

[0042] The evaporator shell 8 is arranged around the upper side of the heating surface 1, forming a cylindrical cavity structure with the heating surface 1. At the same time, a shrinkage rib 5 structure lower than the height of the cylindrical cavity is added to the upper surface of the heating surface 1, and an annular cavity structure is formed between the shrinkage rib 5 and the shell 8. Figure 3 shown.

[0043] The steam outlet 9 is provided on the lower side wall of the shell 8 and communicates with the steam chamber 4 . The liquid inlet 10 is provided on the upper side wall of the shell 8 and communicates with the compensation chamber 11 .

[0044] The lower surface of the heating surface 1 is smooth and can fit closely with the heat source. The upper surface of the heating surface 1 is provided with multiple heat-conducting ribs 2. The end of each heat-conducting rib 2 is equidistant from the annular contraction rib 5. The gaps between the heat-conducting ribs 2 form steam channels 3, which are connected to the steam chamber 4 and further to the steam outlet 9. In particular, an immersed gas pipeline is provided in the steam chamber 4, which is connected to the steam outlet 9.

[0045] The height of the annular shrinkage rib 5 is higher than the thickness of the heat-conducting rib 2 ; the top of the capillary wick 6 is higher than the top of the annular shrinkage rib 5 , so as to completely cover the annular shrinkage rib 5 .

[0046] The height and spacing of each heat-conducting rib 2 are equal, and the height is less than 3mm, and the spacing is less than the thickness and width of the heat-conducting rib 2; the height of the annular shrinkage rib 5 is 6mm~7mm, and the rib width is 0.5mm~1mm; the thickness of the heating surface 1 is 0.5mm~2mm.

[0047] A spring support frame 7 is provided above the capillary wick 6, and a cover plate 12 is provided on top of the housing 8. A spring is connected between the spring support frame 7 and the cover plate 12 to compress the capillary wick 6. The spring force tightly fits the capillary wick 6 and the thermally conductive rib 2, thereby reducing contact thermal resistance. The cross-sectional area of ​​the spring support frame 7 is smaller than that of the cover plate 12.

[0048] Specifically, the spring support frame 7 is an annular structure, with an outer diameter equal to the diameter of the compensation cavity 11 and an inner diameter equal to the diameter of the compensation cavity 11 minus the spring diameter. The spring support frame 7 does not completely cover or isolate the capillary wick 6, allowing the compensation cavity 11 and the capillary wick 6 to communicate.

[0049] The steam outlet 9 is connected to the steam chamber 4, and the liquid inlet 10 is connected to the compensation chamber 11. The steam chamber 4 and the compensation chamber 11 must be separated by the capillary core 6; the steam outlet 9 and the liquid inlet 10 are respectively welded to the external pipeline to form a steam pipeline and a liquid pipeline.

[0050] The present invention further provides an integrated molding process for the flat-plate loop heat pipe evaporator as described in any one of the above, comprising:

[0051] 1) The initial structure of the evaporator is processed, which includes a shell 8, a heating surface 1 provided at the bottom of the shell, an annular shrinkage rib 5 provided on the heating surface 1, and a plurality of heat-conducting ribs 2; the heating surface 1, the heat-conducting ribs 2, the shrinkage ribs 5, and the shell 8 are processed and formed as a whole; before the capillary wick is integrally sintered, the structure of the evaporator is designed and processed according to the heat source requirements, and special attention should be paid to the processing effect of the shrinkage rib 5; the evaporator is degreased, derusted, cleaned, and dried. The evaporator structure is as follows: Figure 2 and Figure 3 shown.

[0052] 2) Sodium carbonate powder is filled in the gaps between the heat-conducting ribs 2 and the gaps between the heat-conducting ribs 2 and the annular shrinkage ribs 5 and compacted; the height of the compacted sodium carbonate powder is slightly lower than the height of the heat-conducting ribs 2;

[0053] 3) Then, the capillary core powder is filled onto the sodium carbonate powder and between the gap between the annular shrinkage rib 5 and the shell 8, and pressed, and then placed in a vacuum sintering furnace for integral sintering; wherein, the filling height of the capillary core powder after pressing is higher than the height of the annular shrinkage rib 5; after sintering is completed, the capillary core 6 is in close contact with the upper side of the thermal conductive rib 2, and can also be in close contact with the outer side of the shrinkage rib 5 after shrinkage; the part not filled with the capillary core powder is the compensation cavity 11.

[0054] 4) After sintering, the sodium carbonate powder is removed to obtain an evaporator. The sodium carbonate powder is preferably removed by washing and dissolving with water, forming steam channels 3 and steam chambers 4. Since the capillary wick powder has a high hardness after sintering, it can be solidified above the thermal ribs 2, thereby forming steam channels 3 and steam chambers 4.

[0055] In some embodiments, the capillary wick powder comprises nickel powder, copper powder, or other powder having a melting point lower than that of the shell material.

[0056] Specifically, the molding process further includes: after cleaning to remove sodium carbonate powder and drying, placing a spring support frame 7 between the capillary wick 6 and the cover plate 12, welding the cover plate 12, and forming a compensation cavity 11 between the cover plate 12 and the capillary wick 6. The elastic force of the spring support frame 7 is utilized to secure the capillary wick 6 a second time, ensuring a tight fit between the capillary wick 6 and the heating rib 2, thereby preventing the capillary wick 6 from falling off due to excessive pressure in the steam chamber 3 during operation of the flat-plate LHP.

[0057] In particular, the heating surface 1 , the heat-conducting ribs 2 , the shrinkage ribs 5 and the housing 8 are made of materials such as copper or stainless steel; the spring support frame 7 and the cover plate 12 are made of the same material as the housing 8 .

[0058] When the evaporator of the present invention is working, the liquid enters the compensation chamber 11 from the liquid inlet 10 and is stored in the compensation chamber 11. Then the liquid flows into the capillary wick 6. The liquid in the capillary wick 6 is vaporized under the action of the heating surface 1 and the heat-conducting ribs 2. The steam passes through the steam channel 3 and is then collected by the steam chamber 4 or the submerged gas pipeline channel, and finally discharged from the steam outlet 9.

[0059] In summary, the evaporator provided by the present invention is suitable for the flat-plate LHP capillary wick integrated sintering process, the capillary wick powder is directly pre-filled into the evaporator, and then the evaporator filled with the capillary wick powder is sintered, and its main features are: 1) The lower surface of the heating surface 1 is smooth and can fit tightly with the heat source, and a plurality of spaced-apart heat-conducting ribs 2 are provided on the upper surface of the heating surface 1, and steam channels 3 are formed between the heat-conducting ribs 2; 2) The evaporator shell 8 is arranged around the upper side of the heating surface 1, and at the same time, a shrinkage rib 5 structure lower than the cavity height is added to the upper surface of the heating surface 1; 3) A spring support frame 7 is placed in the compensation cavity 11, and after the evaporator cover 12 and the shell 8 are welded, the capillary wick 6 is fixed for a second time by using the elastic force of the spring support frame 7, so that the capillary wick 6 and the heating ribs 2 fit tightly. The present invention can solve the difficult problem of assembling the capillary wick and the evaporator in the LHP (i.e., the complex process of designing the corresponding evaporator structure based on the capillary wick structure after the traditional capillary wick is sintered), so that the capillary wick and the evaporator do not need to be matched one-to-one, thereby improving the production efficiency of the LHP, reducing the manufacturing cost, and enabling the large-scale application of the flat-plate LHP; at the same time, the evaporator can achieve good heat transfer, sealing and reliability.

[0060] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A flat-plate loop heat pipe evaporator, characterized in that: The invention comprises a shell (8), a heating surface (1) arranged at the bottom of the shell (8), and a steam chamber (4), a capillary wick (6), a plurality of heat-conducting ribs (2), an annular contraction rib (5) and a compensation chamber (11) arranged inside the shell (8); the steam chamber (4) is provided with a steam outlet (9), and the compensation chamber (11) is provided with a liquid inlet (10); The heat-conducting ribs (2) are distributed at intervals on the heating surface (1); the annular shrinkage ribs (5) are arranged on the heating surface (1) around the heat-conducting ribs (2), and gaps are left between the heat-conducting ribs (2) and the shell (8); the gaps between the annular shrinkage ribs (5) and the heat-conducting ribs (2) form the steam chamber (4); The capillary core (6) is arranged between the heat-conducting rib (2) and the compensation chamber (11), and the capillary core (6) is in contact with the upper surface of the heat-conducting rib (2), the outer surface of the annular contraction rib (5) and the inner surface of the shell (8), so as to separate the steam chamber (4) and the compensation chamber (11).

2. The flat-plate loop heat pipe evaporator according to claim 1, characterized in that: The steam outlet (9) is arranged on the lower side wall of the shell (8) and is communicated with the steam chamber (4); the liquid inlet (10) is arranged on the upper side wall of the shell (8) and is communicated with the compensation chamber (11).

3. The flat-plate loop heat pipe evaporator according to claim 1, characterized in that: The end of each heat-conducting rib (2) is spaced equidistant from the annular contraction rib (5); the gaps between the heat-conducting ribs (2) form a steam channel (3); and the steam channel (3) is connected to the steam chamber (4).

4. The flat-plate loop heat pipe evaporator according to claim 1, characterized in that: The height of the annular shrinkage rib (5) is higher than the thickness of the heat-conducting rib (2); the top of the capillary core (6) is higher than the top of the annular shrinkage rib (5), so as to completely cover the annular shrinkage rib (5).

5. The flat-plate loop heat pipe evaporator according to claim 1, characterized in that: The height and spacing of each heat-conducting rib (2) are equal, and the height is less than 3 mm, and the spacing is less than the thickness and width of the heat-conducting rib (2); the height of the annular shrinkage rib (5) is 6 mm to 7 mm, and the rib width is 0.5 mm to 1 mm; And / or, the thickness of the heating surface (1) is 0.5 mm to 2 mm.

6. The flat-plate loop heat pipe evaporator according to any one of claims 1 to 5, characterized in that: A spring support frame (7) is provided above the capillary core (6), a cover plate (12) is provided on the top of the shell (8), the spring support frame (7) and the cover plate (12) are connected by a spring for pressing the capillary core (6), and the cross-sectional area of ​​the spring support frame (7) is smaller than the cross-sectional area of ​​the cover plate (12).

7. An integrated molding process for a flat-plate loop heat pipe evaporator according to any one of claims 1 to 6, characterized in that: include: Processing the initial structure of the evaporator, the initial structure comprising a shell (8), a heating surface (1) arranged at the bottom of the shell, an annular shrinkage rib (5) arranged on the heating surface (1), and a plurality of heat-conducting ribs (2); Filling the gaps between the heat-conducting ribs (2) and the gaps between the heat-conducting ribs (2) and the annular shrinkage ribs (5) with sodium carbonate powder and compacting them; Filling the capillary core powder onto the sodium carbonate powder and between the gap between the annular shrinkage rib (5) and the shell (8), and pressing, and then vacuum sintering; wherein the filling height of the capillary core powder is higher than the height of the annular shrinkage rib (5); After sintering is completed, the sodium carbonate powder is removed to obtain an evaporator.

8. The integrated molding process of the flat-plate loop heat pipe evaporator according to claim 7, characterized in that: The sodium carbonate powder is removed by washing with water.

9. The integrated molding process of the flat-plate loop heat pipe evaporator according to claim 7, characterized in that: The capillary wick powder comprises nickel powder and / or copper powder.

10. The integrated molding process of the flat-plate loop heat pipe evaporator according to any one of claims 7 to 9, characterized in that: The molding process also includes: placing a spring support frame (7) and a spring on the top of the capillary core (6), and placing a cover plate (12) above the spring and then welding them.

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