A "positive meniscus" capillary wick for high heat flux loop heat pipes

Abstract

The present invention provides a "positive meniscus" capillary wick for a high heat flux density loop heat pipe, comprising an inner capillary wick, a tube shell and an outer capillary wick; the outer capillary wick is sintered inside the tube shell, and the inner capillary wick and the outer capillary wick are interference-fitted and installed inside the tube shell; the inner capillary wick comprises a capillary wick body, an inner steam channel and a liquid main channel; a first chamfer is arranged on one side of the capillary wick body; the outer capillary wick comprises an inner thread and an outer steam channel; a second chamfer is processed on one side of the outer capillary wick; the second chamfer has the same chamfer slope as the first chamfer; the outer capillary wick and the capillary wick body are made of porous materials. The present invention has a simple structure and low process difficulty, solves the problem of the contradiction between the evaporation area and the steam exhaust channel area under high heat flux density conditions, and significantly improves the high heat flux density heat transfer capacity of the loop heat pipe.

Description

Technical Field

[0001] The invention relates to the technical field of radiators with large heat capacity and high heat flux density, and in particular to a "positive meniscus" capillary wick used for a high heat flux density loop heat pipe. Background Art

[0002] Loop heat pipes have the advantages of large heat transfer, long heat transfer distance, unidirectional heat transfer, flexible layout, high reliability, long service life, and excellent anti-gravity ability. High-power heat flux devices such as CPU, GPU, IGBT, LED, T / R components, etc. have heat flux densities of up to hundreds of watts per square centimeter, requiring loop heat pipes to have high heat flux density heat transfer capabilities.

[0003] High heat flux loop heat pipes need to solve two conflicting core problems:

[0004] (1) Increase the evaporation area and reduce the heat load per unit area on the capillary wick surface;

[0005] (2) Increase the area of ​​the steam exhaust channel and reduce the exhaust steam flow resistance loss.

[0006] Traditional loop heat pipes use an "inverted meniscus" design, that is, the direction of the applied heat flow is opposite to the direction of the capillary wick meniscus. In this design, the evaporation of the working fluid occurs on the surface of the capillary wick that is in interference fit with the evaporator shell. A steam discharge channel must be established at the boundary between the shell and the capillary wick. There are two main technical solutions for existing technologies:

[0007] (1) The steam exhaust channel is built on the capillary wick or the shell. This design uses an isotropic capillary wick and simply decomposes the surface area of ​​the capillary wick into the evaporation area and the exhaust area. During operation, only the interference fit between the capillary wick and the shell participates in phase change heat transfer, and the uncontacted part of the capillary wick is the exhaust channel. This design has a simple structure and low process difficulty, and is only suitable for heat flux density not higher than 10W / cm 2 application scenarios.

[0008] (2) The steam exhaust channel is built on the capillary core, and the internal thread of the tube shell is filled with a double-aperture porous material (the small aperture is used for phase change, and the large aperture is used for exhaust) - this design uses a double-aperture capillary core on the outer layer and an isotropic capillary core on the inner layer, which expands the surface area of ​​the capillary core, and all the surface area of ​​the capillary core is involved in phase change and exhaust; during operation, the small aperture on the surface of the capillary core is used for phase change, and the large aperture is used for exhaust; this design is suitable for heat flux density not higher than 100W / cm 2 However, due to the need to sinter a double-aperture capillary core, the design structure is complex and the process is difficult.

[0009] Therefore, there is an urgent need to design a solution with simple structure and low process difficulty to solve the contradiction between the evaporation area and the steam discharge channel area under high heat flux density conditions, so as to significantly improve the high heat flux density heat transfer capacity of the loop heat pipe. Summary of the invention

[0010] In order to solve the above technical problems, the present invention discloses a "positive meniscus" capillary wick for a high heat flux density loop heat pipe. The technical solution of the present invention is implemented as follows:

[0011] A "positive meniscus" capillary wick for a high heat flux density loop heat pipe, comprising an inner capillary wick, a tube shell and an outer capillary wick;

[0012] The outer capillary core is sintered inside the tube shell, and the inner capillary core is interference-fitted with the outer capillary core and installed inside the tube shell;

[0013] The inner capillary wick comprises a capillary wick body, an inner steam channel and a liquid trunk;

[0014] A first chamfer is provided on one side of the capillary core body;

[0015] The inner steam channel is opened on the outer surface of the capillary core body and is located on the side provided with the first chamfer; the liquid channel is opened in the center of the inner capillary core and is located on the other side provided with the first chamfer;

[0016] The outer capillary wick comprises an inner thread and an outer steam channel;

[0017] One side of the outer capillary core is processed with a second chamfer;

[0018] The second chamfer has the same slope as the first chamfer;

[0019] The inner thread is arranged on the inner side of the outer capillary core; the outer steam channel is arranged on the side of the outer capillary core processed with the second chamfer;

[0020] The length and width of the outer steam channel are the same as the length and width of the inner steam channel;

[0021] The outer capillary core and the capillary core body are made of porous materials.

[0022] Preferably, the porous material is made of nickel.

[0023] Preferably, the inner capillary core has a pore size of 1-5 μm, a porosity of 60%-80%, and a permeability of 10 -13 -10 -12 m 2 , equivalent thermal conductivity 0.1-5W / (m·K).

[0024] Preferably, the outer capillary core has a pore size of 0.1-2 μm, a porosity of 50%-70%, and a permeability of 10 -14 -10 - 13 m 2 , equivalent thermal conductivity>50W / (m·K).

[0025] Preferably, the outer capillary core has a thickness of 0.95-1.05 mm.

[0026] Preferably, the inner surface of the outer capillary core is etched, and the etching amount is less than 0.01 mm.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The outer capillary core has a high equivalent thermal conductivity, and the inner thread structure is the evaporation surface and exhaust channel, which can be applied to heat flux density of hundreds of watts per square centimeter;

[0029] Only two capillary cores of the same property need to be sintered, which has a simple structure and low process difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0031] The same parts are denoted by the same reference numerals. It should be noted that the words "front", "rear", "left", "right", "upper" and "lower" used in the following description refer to directions in the drawings, and the words "bottom" and "top", "inner" and "outer" refer to directions toward or away from the geometric center of a specific component, respectively.

[0032] Figure 1 A cross-sectional view of a "positive meniscus" capillary wick for a high heat flux density loop heat pipe;

[0033] Figure 2 Schematic diagram of the structure of the inner capillary core;

[0034] Figure 3 It is a schematic diagram of the structure of the outer capillary core sintered in the shell and tube;

[0035] Figure 4 It is a cross-sectional view of the structure of the outer capillary core sintered in the shell and tube;

[0036] Figure 5 It is a partial schematic diagram of the evaporation surface of the "positive meniscus" capillary wick;

[0037] Figure 6 Schematic diagram of capillary drive and surface evaporation.

[0038] In the above drawings, the figure numbers represent:

[0039] 1. Inner capillary wick

[0040] 1-1. Capillary wick body

[0041] 1-2. Inner steam channel

[0042] 1-3. Liquid mains

[0043] 1-4. First chamfer

[0044] 2. Tube shell

[0045] 3. Outer capillary wick

[0046] 3-1. Internal thread

[0047] 3-2. Outer steam channel

[0048] 3-3. Second chamfer

[0049] 4. Porous media skeleton

[0050] 5. Liquid working fluid

[0051] 6. Steam working fluid

[0052] 7. Meniscus

[0053] 8. External heat source DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0055] Example 1

[0056] In a specific embodiment, Figure 1 , Figure 2 , Figure 3 and Figure 4 As shown, a "positive meniscus" capillary wick for a high heat flux density loop heat pipe includes an inner capillary wick 1, a tube shell 2 and an outer capillary wick 3.

[0057] The outer capillary core 3 is sintered inside the tube shell 2, and the inner capillary core 1 is interference-fitted with the outer capillary core 3 and installed inside the tube shell 2;

[0058] The inner capillary wick 1 comprises a capillary wick body 1-1, an inner steam channel 1-2 and a liquid trunk channel 1-3;

[0059] One side of the capillary core body 1-1 is processed with a first chamfer 1-4;

[0060] The inner steam channel 1-2 is opened on the outer surface of the capillary core body 1-1, the length of the inner steam channel 1-2 is less than the length of the inner capillary core 1, and the inner steam channel 1-2 is opened on the side of the capillary core body 1-1 processed with the first chamfer 1-4;

[0061] The liquid trunk channel 1-3 is opened at the center of the inner capillary core 1, the depth of the liquid trunk channel 1-3 is less than the length of the inner capillary core 1, and the liquid trunk channel 1-3 is opened on the other side of the capillary core body 1-1 processed with the first chamfer 1-4;

[0062] The outer capillary core 3 comprises an inner thread 3-1 and an outer steam channel 3-2;

[0063] One side of the outer capillary core 3 is processed with a second chamfer 3-3, and the slope of the second chamfer 3-3 is consistent with the slope of the first chamfer 1-4 of the inner capillary core 1;

[0064] The inner side of the outer capillary core 3 is processed with an internal thread 3-1;

[0065] An outer steam channel 3-2 is provided on one side of the second chamfer 3-3 of the outer capillary core 3, and the length and width of the outer steam channel 3-2 are equal to the length of the inner steam channel 1-2; the outer capillary core 3 is a porous material, and has the characteristics of small average pore size, high porosity, large permeability, and high equivalent thermal conductivity, and the equivalent thermal conductivity is greater than 50W / (m·K); an outer capillary core 3 with a thickness of about 1mm is sintered inside the tube shell 2, and the inner circle is trimmed by a lathe to adjust the roundness and straightness of the inner circle, the thickness of the porous layer and the structure of the inner thread 3-1 of the porous layer, and the inner surface is etched by chemical etching after machining, and the surface plugging caused by machining is opened;

[0066] The inner capillary core 1 is a porous material, and the pore size, porosity and permeability of the inner capillary core 1 are greater than those of the outer capillary core 3. The equivalent thermal conductivity of the inner capillary core 1 is low, which should be less than 5W / (m·K); after the inner capillary core 1 is sintered, the outer circle is trimmed by a lathe to adjust the roundness, straightness and size of the outer circle, so as to facilitate interference assembly. The outer surface does not need to be etched after machining.

[0067] The inner capillary core 1 and the outer capillary core 3 are interference-fitted into a whole by adopting the method of thermal expansion and contraction, and the inner steam channel 1-2 and the outer steam channel 3-2 are in the same direction.

[0068] Using the technical solution of this embodiment, Figure 5 , Figure 6 As shown, the outer capillary wick 3 is a porous material formed by sintering, and the porous material is composed of a large number of densely grouped tiny gaps divided by a solid porous medium skeleton 4. The capillary force generated between the tiny gaps absorbs the liquid working medium 5 into the outer capillary wick 3, and the liquid working medium 5 infiltrates the outer capillary wick 3. The liquid working medium 5 forms a concave meniscus 7 under the action of surface tension. The heat of the external heat source 8 is directly transferred to the outer capillary wick 3 through the tube shell 2. At this time, the heat direction of the applied external heat source 8 is the same as the direction of the meniscus 7 formed by the liquid working medium 5 between the porous medium skeleton 4, forming a "positive meniscus". At this time, the surface area of ​​the inner thread 3-1 of the outer capillary core 3 is the evaporation surface, and the heating area is greatly increased compared with the traditional "inverted meniscus" design. After the liquid working medium 5 is heated and evaporated, the steam working medium 6 enters the threaded channel between the inner thread 3-1 of the outer capillary core 3 and the outer surface of the inner capillary core 1 and merges into the outer steam channel 3-2 of the outer capillary core 3 and the inner steam channel 1-2 of the inner capillary core 1.

[0069] This embodiment adopts the technical solution of "positive meniscus", that is, the heat direction of the applied external heat source 8 and the direction of the meniscus 7 formed by the working fluid between the multi-medium skeletons 4 are the same. Compared with the prior art, only two capillary cores of the same properties need to be sintered, the structure is simple, the process difficulty is small, the outer capillary core 3 has a high equivalent thermal conductivity, and the internal thread 3-1 structure is both an evaporation surface and an exhaust channel, which can be applied to a heat flux density of hundreds of watts per square centimeter.

[0070] In a preferred embodiment, the inner capillary core 1 and the outer capillary core 3 are both made of sintered nickel porous materials.

[0071] In a preferred embodiment, the inner capillary core 1 has a pore size of 1-5 μm, a porosity of 60%-80%, and a permeability of 10 -13 -10 -12 m 2 , equivalent thermal conductivity 0.1-5W / (m·K), the pore size of the outer capillary core 3 is 0.1-2μm, the porosity is 50%-70%, and the permeability is 10 -14 -10 -13 m 2 , equivalent thermal conductivity>50W / (m·K).

[0072] In a preferred embodiment, the outer capillary core 3 has a thickness of 0.95-1.05 mm, and more preferably, a thickness of 1 mm.

[0073] In a preferred embodiment, the inner surface of the outer capillary core 3 is etched, and the etching amount is less than 0.01 mm.

[0074] The present invention overcomes the shortcomings of the prior art and provides a "positive meniscus" capillary wick for a high heat flux density loop heat pipe, which can achieve a heat flux density of hundreds of watts per square centimeter, has a simple structure, and has low process difficulty, and significantly improves the high heat flux density heat transfer capacity of the loop heat pipe.

[0075] It should be pointed out that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A "positive meniscus" capillary wick for a high heat flux density loop heat pipe, characterized in that: It includes an inner capillary core, a tube shell and an outer capillary core; The outer capillary core is sintered inside the tube shell, and the inner capillary core is interference-fitted with the outer capillary core and installed inside the tube shell; The inner capillary wick comprises a capillary wick body, an inner steam channel and a liquid trunk; A first chamfer is provided on one side of the capillary core body; The inner steam channel is opened on the outer surface of the capillary core body and is located on the side provided with the first chamfer; the liquid channel is opened in the center of the inner capillary core and is located on the other side provided with the first chamfer; The outer capillary wick comprises an inner thread and an outer steam channel; One side of the outer capillary core is processed with a second chamfer; The second chamfer has the same chamfer slope as the first chamfer; The inner thread is arranged on the inner side of the outer capillary core; the outer steam channel is arranged on the side of the outer capillary core processed with the second chamfer; The length and width of the outer steam channel are the same as the length and width of the inner steam channel; The outer capillary core and the capillary core body are made of porous materials; The pore size, porosity and permeability of the inner capillary core are all greater than those of the outer capillary core.

2. A "positive meniscus" capillary wick for a high heat flux density loop heat pipe according to claim 1, characterized in that: The porous material is made of nickel.

3. A "positive meniscus" capillary wick for a high heat flux density loop heat pipe according to claim 2, characterized in that: The inner capillary core has a pore size of 1-5 μm, a porosity of 60%-80%, and a permeability of 10 -13 -10 -12 m 2 , equivalent thermal conductivity 0.1-5W / (m·K).

4. A "positive meniscus" capillary wick for a high heat flux density loop heat pipe according to claim 3, characterized in that: The pore size of the outer capillary core is 0.1-2 μm, the porosity is 50%-70%, and the permeability is 10 -14 -10 -13 m 2 , equivalent thermal conductivity>50W / (m·K).

5. A "positive meniscus" capillary wick for a high heat flux density loop heat pipe according to claim 4, characterized in that: The thickness of the outer capillary core is 0.95-1.05 mm.

6. A "positive meniscus" capillary wick for a high heat flux density loop heat pipe according to claim 5, characterized in that: The inner surface of the outer capillary core is etched, and the etching amount is less than 0.01 mm.

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