CN115507685A - A "Positive Meniscus" Capillary Wick for High Heat Flux Loop Heat Pipes - Google Patents

Abstract

The invention provides a positive meniscus capillary core for a high heat flow density loop heat pipe, which comprises an inner layer capillary core, a pipe shell and an outer layer capillary core; an outer-layer capillary core is sintered inside the tube shell, and the inner-layer capillary core and the outer-layer capillary core are in interference fit and are arranged inside the tube shell; the inner-layer capillary core comprises a capillary core main body, an inner-layer steam channel and a liquid main channel; a first chamfer is arranged on one side of the capillary core main body; the outer layer capillary core comprises internal threads and an outer layer steam channel; a second chamfer is processed on one side of the outer capillary core; the slope of the second chamfer is the same as that of the first chamfer; the outer capillary wick and the capillary wick main body are made of porous materials. The invention has simple structure and small process difficulty, solves the problem of contradiction between the evaporation area and the steam discharge channel area under the working condition of high heat flow density, and obviously improves the heat transfer capacity of the loop heat pipe with high heat flow density.

Description

A "Positive Meniscus" Capillary Wick for High Heat Flux Loop Heat Pipes

technical field

The invention relates to the technical field of large heat and high heat flux radiators, in particular to a "positive meniscus" capillary core for high heat flux loop heat pipes.

Background technique

The loop heat pipe has the advantages of large heat transfer, long heat transfer distance, one-way heat transfer, flexible layout, high reliability, long working life, and excellent anti-gravity ability. High-power heat-flux devices such as CPU, GPU, IGBT, LED, T/R components and other heat-flux devices can reach hundreds of watts per square centimeter, requiring loop heat pipes to have high heat-flux heat transfer capabilities.

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

(1) Increase the evaporation area and reduce the heat load per unit area of the capillary surface;

(2) Increase the area of the steam discharge channel to reduce the flow resistance loss of the exhaust steam.

The traditional loop heat pipe adopts an "inverted meniscus" design, that is, the direction of the applied heat flow is opposite to that of the meniscus of the capillary core. 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, and a steam discharge channel must be established at the boundary between the shell and the capillary wick. There are mainly two technical solutions in the existing technology:

(1) The steam discharge channel is built on the capillary core or the shell. This design uses an isotropic capillary core, and simply decomposes the surface area of the capillary core into evaporation area and exhaust area. During operation, only the interference fit part of the capillary core and the shell participates in the phase transformation heat, and the non-contact part of the capillary core 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.

(2) The steam discharge channel is established on the capillary core, and the inner thread of the shell is filled with a double-aperture porous material (small pore size for phase change, large pore size for steam exhaust) - the outer layer of this design uses a double-pore wick, The inner layer adopts an isotropic capillary core, which expands the surface area of the capillary core, and all the surface area of the capillary core participates in phase change and steam exhaust; during operation, the small pore size on the surface of the capillary core is used for phase change, and the large pore size is used for steam exhaust; this design It is suitable for application scenarios where the heat flux density is not higher than 100W/cm ² , but due to the need to sinter the double-aperture capillary core, the design structure is complex and the process is difficult.

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

Contents of the invention

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

A "positive meniscus" capillary core for a high heat flux loop heat pipe, comprising 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 includes a capillary main body, an inner steam channel and a liquid main channel;

One side of the capillary main body is provided with a first chamfer;

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

The outer capillary core includes an internal thread and an outer steam channel;

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

The slope of the second chamfer is the same as that of the first chamfer;

The internal thread is arranged inside the outer capillary; the outer steam channel is arranged on the side of the outer capillary processed with a second chamfer;

The length and width of the outer layer steam channel are the same as the length and width of the inner layer steam channel;

The outer capillary core and the capillary core body are porous materials.

Preferably, the porous material is made of nickel.

Preferably, the pore diameter of the inner capillary core is 1-5 μm, the porosity is 60%-80%, the permeability is ^10-13-10-12 m ² , and the equivalent thermal conductivity is ^0.1-5W /(m·K).

Preferably, the pore diameter of the outer capillary core is 0.1-2 μm, the porosity is 50%-70%, the permeability is 10 ^-14 -10 ^{- 13} m ² , and the equivalent thermal conductivity is >50W/(m·K).

Preferably, the thickness of the outer capillary core is 0.95-1.05mm.

Preferably, the inner surface of the outer capillary core is etched, and the etching amount is <0.01 mm.

Compared with prior art, the beneficial effect of the present invention is:

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

It only needs to sinter two kinds of isotropic capillary cores, the structure is simple, and the process difficulty is small.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only It is an embodiment of the present invention, and those skilled in the art can also obtain other drawings based on these drawings without any creative work.

Wherein the same components 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 the directions in the drawings, and the words "bottom" and "top "Face", "inner" and "outer" refer to directions toward or away from, respectively, the geometric center of a particular component.

Figure 1 is a cross-sectional view of a "positive meniscus" capillary wick for a high heat flux loop heat pipe;

Fig. 2 is the structural representation of inner layer capillary core;

Fig. 3 is the structural representation of shell sintering outer layer capillary core;

Fig. 4 is a structural cross-sectional view of the sintered outer capillary core of the tube shell;

Fig. 5 is a partial schematic diagram of the "positive meniscus" capillary wick evaporation surface;

Figure 6 is a schematic diagram of capillary drive and surface evaporation.

In the above-mentioned accompanying drawings, each figure number sign represents respectively:

1. Inner capillary core

1-1. Capillary main body

1-2. Inner layer steam channel

1-3. Liquid main road

1-4. First chamfering

2. Shell

3. Outer capillary core

3-1. Internal thread

3-2. Outer steam channel

3-3. Second chamfering

4. Porous media skeleton

5. Liquid working medium

6. Steam working medium

7. Meniscus

8. External heat source

detailed description

The following clearly and completely describes the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1

In a specific embodiment, as shown in Fig. 1, Fig. 2, Fig. 3 and Fig. 4, a "positive meniscus" capillary wick for a high heat flux loop heat pipe includes an inner capillary wick 1 , shell 2 and outer capillary core 3.

The outer capillary core 3 is sintered inside the shell 2, and the inner capillary core 1 and the outer capillary core 3 are interference fit and installed inside the shell 2;

The inner capillary core 1 includes a capillary core main body 1-1, an inner layer steam channel 1-2 and a liquid main channel 1-3;

One side of the capillary main body 1-1 is processed with a first chamfer 1-4;

The inner layer steam channel 1-2 is provided on the outer surface of the capillary wick main body 1-1, the length of the inner layer steam channel 1-2 is less than the length of the inner layer capillary wick 1, and the inner layer steam The channel 1-2 is opened on the side of the capillary main body 1-1 processed with the first chamfer 1-4;

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

The outer capillary core 3 includes an internal thread 3-1 and an outer steam channel 3-2;

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;

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

One side of the second chamfer 3-3 of the outer layer capillary core 3 has an outer layer steam channel 3-2, and the length and width of the outer layer steam channel 3-2 are the same as those of the inner layer steam channel 1-2. The lengths are equal; the outer capillary core 3 is a porous material with a small average pore size, high porosity, high permeability, and high equivalent thermal conductivity. The equivalent thermal conductivity is greater than 50W/(m K); The outer capillary core 3 with a thickness of about 1 mm is sintered inside the 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 internal thread 3-1 of the porous layer, and chemical etching is used after machining The inner surface is etched by means of etching, and the surface plugged holes generated by machining are opened;

The inner capillary core 1 is a porous material, and the pore diameter, porosity, and permeability of the inner capillary core 1 are greater than that of the outer capillary core 3, and the equivalent thermal conductivity of the inner capillary core 1 is low. Less than 5W/(m·K); after the inner capillary core 1 is sintered and formed, 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.

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

Using the technical solution of this embodiment, as shown in Figure 5 and Figure 6, the outer capillary core 3 is a porous material formed by sintering, and the porous material is formed by dividing a solid porous medium skeleton 4 into a large number of densely clustered tiny voids. composition. The capillary force generated between the tiny gaps sucks the liquid working medium 5 into the outer capillary core 3, and the liquid working medium 5 infiltrates the outer capillary core 3, and 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 core 3 through the tube shell 2. At this time, the heat direction of the applied external heat source 8 is in line with the direction of the meniscus 7 formed between the porous medium skeleton 4 by the liquid working medium 5 The same, forming a "positive meniscus". At this time, the surface area of the internal thread 3-1 of the outer capillary 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 The thread channel between the internal thread 3-1 entering the outer capillary 3 and the outer surface of the inner capillary 1 merges into the outer steam channel 3-2 of the outer capillary 3 and the inner layer of the inner capillary 1 Steam channels 1-2.

This embodiment adopts the technical solution of "positive meniscus", that is, the direction of the heat applied by the external heat source 8 is the same as that of the meniscus 7 formed by the working fluid between the multi-media skeletons 4 . Compared with the existing technology, it only needs to sinter two kinds of isotropic capillary cores, the structure is simple, the process difficulty is small, the outer capillary core 3 equivalent thermal conductivity is high, and the internal thread 3-1 structure is an evaporation surface and an exhaust channel , applicable to heat flux densities of hundreds of watts per square centimeter.

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

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

In a preferred embodiment, the thickness of the outer capillary core 3 is 0.95-1.05 mm. More preferably, the thickness is 1 mm.

In a preferred embodiment, the inner surface of the outer capillary core 3 is etched, and the etching amount is <0.01mm.

The present invention overcomes the deficiencies of the prior art, and provides a "positive meniscus" capillary core for high heat flux loop heat pipes, which can realize a heat flux density of hundreds of watts per square centimeter, and has a simple structure and low process difficulty , significantly improving the high heat flux heat transfer capability of the loop heat pipe.

It should be pointed out that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be Included within the protection scope of the present invention.

Claims (6)

1. A "positive meniscus" capillary core for a high heat flux loop heat pipe, characterized in that it includes an inner capillary core, a 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 includes a capillary main body, an inner steam channel and a liquid main channel; One side of the capillary main body is provided with a first chamfer; The inner steam channel is opened on the outer surface of the capillary core body and is located on the side with the first chamfer; the liquid main channel is opened in the center of the inner capillary core and is located on the other side with the first chamfer; The outer capillary core includes an internal thread and an outer steam channel; One side of the outer capillary core is processed with a second chamfer; The slope of the second chamfer is the same as that of the first chamfer; The internal thread is arranged inside the outer capillary; the outer steam channel is arranged on the side of the outer capillary processed with a second chamfer; The length and width of the outer layer steam channel are the same as the length and width of the inner layer steam channel; The outer capillary core and the capillary core body are porous materials. 2. A "positive meniscus" capillary wick for a high heat flux loop heat pipe according to claim 1, wherein the porous material is made of nickel. 3. A "positive meniscus" capillary wick for high heat flux loop heat pipes according to claim 2, characterized in that the inner capillary wick has a pore diameter of 1-5 μm and a porosity of 60% -80%, permeability 10 ^-13 -10 ^-12 m ² , equivalent thermal conductivity 0.1-5W/(m·K). 4. A "positive meniscus" capillary wick for high heat flux loop heat pipes according to claim 3, characterized in that the outer capillary wick 3 has a pore diameter of 0.1-2 μm and a porosity of 50 %-70%, permeability 10 ^-14 -10 ^-13 m ² , equivalent thermal conductivity >50W/(m·K). 5. A "positive meniscus" capillary wick for high heat flux loop heat pipes according to claim 4, characterized in that the thickness of the outer capillary wick is 0.95-1.05 mm. 6. A "positive meniscus" capillary wick for a high heat flux loop heat pipe according to claim 5, wherein the inner surface of the outer capillary wick is etched, and the engraved Erosion <0.01mm.

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