CN108662934B - Foam metal-fiber composite capillary core applied to loop heat pipe and processing method thereof - Google Patents
Foam metal-fiber composite capillary core applied to loop heat pipe and processing method thereof Download PDFInfo
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- 239000006260 foam Substances 0.000 title claims abstract description 146
- 239000000835 fiber Substances 0.000 title claims abstract description 124
- 239000002131 composite material Substances 0.000 title claims abstract description 35
- 238000003672 processing method Methods 0.000 title claims abstract description 13
- 229910052751 metal Inorganic materials 0.000 claims abstract description 117
- 239000002184 metal Substances 0.000 claims abstract description 117
- 239000011148 porous material Substances 0.000 claims description 61
- 239000002994 raw material Substances 0.000 claims description 29
- 238000005245 sintering Methods 0.000 claims description 29
- 239000007769 metal material Substances 0.000 claims description 19
- 239000000945 filler Substances 0.000 claims description 18
- 239000000843 powder Substances 0.000 claims description 15
- 239000007787 solid Substances 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 9
- 239000011812 mixed powder Substances 0.000 claims description 9
- 238000001035 drying Methods 0.000 claims description 7
- 238000002844 melting Methods 0.000 claims description 7
- 230000008018 melting Effects 0.000 claims description 7
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 4
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 3
- 239000004202 carbamide Substances 0.000 claims description 3
- 238000004140 cleaning Methods 0.000 claims description 3
- 239000011780 sodium chloride Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims 1
- 230000008859 change Effects 0.000 abstract description 42
- 238000012546 transfer Methods 0.000 abstract description 21
- 238000001704 evaporation Methods 0.000 abstract description 20
- 230000008020 evaporation Effects 0.000 abstract description 20
- 230000035699 permeability Effects 0.000 abstract description 5
- 238000002360 preparation method Methods 0.000 abstract description 4
- 238000002407 reforming Methods 0.000 abstract 1
- 230000005499 meniscus Effects 0.000 description 10
- 239000007788 liquid Substances 0.000 description 9
- 238000010586 diagram Methods 0.000 description 5
- 229920001410 Microfiber Polymers 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 238000011049 filling Methods 0.000 description 4
- 239000003658 microfiber Substances 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 230000017525 heat dissipation Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 238000013461 design Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 239000006262 metallic foam Substances 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 239000013526 supercooled liquid Substances 0.000 description 2
- 238000004506 ultrasonic cleaning Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D15/00—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies
- F28D15/02—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes
- F28D15/04—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure
- F28D15/046—Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls ; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies in which the medium condenses and evaporates, e.g. heat pipes with tubes having a capillary structure characterised by the material or the construction of the capillary structure
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- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Sustainable Development (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Powder Metallurgy (AREA)
- Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
Abstract
The invention discloses a foam metal-fiber composite capillary core applied to a loop heat pipe and a processing method thereof, belonging to the technical field of porous medium phase change and flow. The capillary core of the invention takes foam metal as a framework, fibers reform the foam metal framework macropores to form interfiber micropores, and a porous structure with double apertures is realized in one space. The processing method of the invention takes foam metal as a framework, the appearance is easy to control during preparation, the prepared capillary core is light in weight, higher in porosity, high in mechanical strength and flexible, the fiber is used for reforming the foam metal framework, the prepared capillary core has the flowing heat transfer characteristics of high capillary suction force, high permeability, low effective heat conductivity and high surface evaporation rate, and the capillary core is applied to a loop heat pipe, so that the heat transfer and mass transfer in the loop heat pipe can be enhanced, the back heat leakage is reduced, the operation temperature and phase change interface of the loop heat pipe are stabilized, the loop heat pipe is accelerated to start, and the operation performance of the loop heat pipe is improved.
Description
Technical Field
The invention relates to the technical field of porous medium phase change and flow, in particular to a foam metal-fiber composite capillary core applied to a loop heat pipe and a processing method thereof, which can be used in the fields of electronic equipment cooling, aviation thermal control and the like.
Background
Loop Heat Pipe (LHP) is a high-efficiency passive heat transfer device for transferring heat by using phase change of working medium, and has the advantages of no moving parts, good heat transfer performance, long transmission distance, etc. The loop heat pipe is a separated heat pipe composed of an evaporator, an evaporation pipeline, a condenser, a liquid pipeline and a compensation cavity. And a capillary core is arranged at the evaporator to provide power and a phase change heat exchange place for the system. The working process of the loop heat pipe system is as shown in fig. 1: after the heat dissipation part is attached to the evaporator 5, heat is led into the capillary core 10 through the wall surface of the evaporator 5, the internal working medium is subjected to phase change after the capillary core 10 is heated, a phase change interface is formed, steam enters the condenser 7 through the steam pipeline 6 to be condensed into supercooled liquid, the supercooled liquid flows back to the compensation cavity 9 through the liquid pipeline 8, the liquid in the compensation cavity 9 continuously supplements the liquid evaporated in the capillary core 10, and the heat of the heat dissipation part is continuously transferred to the outside in the evaporation-condensation circulation process.
When the loop heat pipe system operates, the phase change occurs in the capillary core, and the capillary core provides capillary suction force for the system, so that the loop heat pipe system is the only power source of the whole system. The capillary core commonly used at present mainly comprises a single metal powder sintering capillary core, and a filler is added on the basis to sinter the capillary core into a double-aperture capillary core, wherein small holes can increase the suction force of the capillary core, large holes reduce the flow resistance of working media, and the capillary core is favorable for separating steam and compensating liquid in time, but the advantage disappears after the filler is added to a certain amount. The metal powder sintered capillary core is usually prepared by a cold press molding sintering method, and after powder is mixed, pressurizing is carried out to lead loose pores in the capillary core to be extruded, and closed pores or semi-open pores are formed after the extruded pores are sintered, so that pore channels are reduced, and the porosity is reduced; if loose sintering is carried out, the powder inside the capillary core is not easy to adhere, and the mechanical strength is low.
In order to strengthen the phase change of the working medium in the capillary core, the capillary core is usually made of a metal material with higher heat conductivity, the effective heat conductivity of the capillary core is increased, the back heat leakage is larger when the system is operated, the temperature of the compensation cavity is increased, the operation temperature of the system is increased, and meanwhile the fluctuation of the operation of the system is increased. The phase change occurs after the temperature of the liquid in the compensation cavity is increased, the internal pressure is increased, and the running resistance of the system is increased. When the system is operated, the evaporation rate of the working medium is gradually increased along with the increase of the heat load, the phase change interface is not timely moved inwards due to the fact that the working medium is not supplemented, the thickness of the steam layer is increased, and the operation stability of the system is affected due to the increase of the capillary core thermal resistance. Therefore, designing a capillary wick with high evaporation rate, low effective heat conductivity and excellent performance, which can stabilize the evaporation interface, is a problem that needs to be solved at present.
Through searching, patent publication about capillary core design of loop heat pipe is already known, such as Chinese patent application number: 2004101030689, filing date: 12 months and 30 days 2004, the invention is named: the application discloses a two-phase capillary pump loop composite capillary core and a preparation method thereof, wherein the composite capillary core comprises a large-aperture inner core, a small-aperture outer core is arranged on the outer side of the inner core, the permeability of the composite structure capillary core of the application is increased, and the high-efficiency CPL can be developed; another example is chinese patent application No.: 2016102861131, filing date: 28 days of 2016, 4 months, the invention is named: the powder microfiber composite porous capillary core is formed by mixing and sintering metal powder and microfiber, and the metal powder is connected through microfiber to realize a small-aperture dual-aperture porous medium structure formed by microfiber among the powder and a large-aperture dual-aperture porous medium structure formed among the particle powder; the unique structure of the capillary core endows the capillary core with flow heat transfer characteristics of high capillary suction force, low flow resistance, high surface evaporation rate and low effective heat conductivity; the heat pipe is applied to a loop heat pipe system, can strengthen heat and mass transfer inside, stabilize an evaporation phase change interface of working media, reduce heat leakage to a compensation cavity, eliminate or weaken temperature fluctuation of system operation, and further improve the operation performance of the loop heat pipe. The above application has all made optimal design to loop heat pipe capillary core structure, helps improving whole operational performance, but its still has the room of further promotion.
Disclosure of Invention
1. Technical problem to be solved by the invention
The invention aims to overcome the defects of poor structural performance of a capillary core and influence on the running stability of a loop heat pipe in the prior art, and provides a foam metal-fiber composite capillary core applied to the loop heat pipe and a processing method thereof, and the foam metal-fiber composite capillary core applied to the loop heat pipe can fully utilize pores in the capillary core, reduce the thickness and the quality of the capillary core, and take foam metal as a framework, and has high mechanical strength and certain flexibility; when the loop heat pipe system operates, the capillary core has higher surface heat transfer coefficient, the overall effective heat transfer coefficient is lower, and the heat dissipation is ensured while the back heat leakage is reduced; in terms of structure, the capillary core has more pores and larger porosity, and small holes formed among fibers enable the capillary core to have enough capillary suction force, and meanwhile, an adhesion surface is provided for a phase change interface, so that the phase change interface is stabilized, the large pore diameter formed by a foam metal framework is used for reducing the resistance of working medium flowing, the size of a system can be effectively reduced, the applicability is enhanced, and the performance of a loop heat pipe is further improved; in the aspect of preparation, the foam metal is finished by machining, the foam metal can be manufactured according to the shape and the size required by the capillary core, the sintering is not easy to deform, the size and the shape are controllable, and the capillary core processing method is simple and convenient to operate and suitable for popularization and application.
2. Technical proposal
In order to achieve the above purpose, the technical scheme provided by the invention is as follows:
the invention relates to a foam metal-fiber composite capillary core applied to a loop heat pipe system, which is of a double-aperture porous medium structure and comprises the following components: fibers, metal foam frameworks, fiber pores, and metal foam framework pores; the fibers are distributed in the foam metal frameworks, small-pore-diameter fiber pores are formed among the fibers, and large-pore-diameter foam metal framework pores are formed among the foam metal frameworks.
Further, the foam metal skeleton is made of foam metal material with heat conductivity exceeding 100W/mK.
Further, the foam metal framework is made of foam metal materials with the pore diameter of 50-150 um.
Further, the fiber is made of metal material with length-diameter ratio of 5-10 and length of 10-40 um.
The invention discloses a processing method of a foam metal-fiber composite capillary core applied to a loop heat pipe system, which comprises the following steps:
step one, preparing a fiber raw material and a foam metal raw material, placing the foam metal into a sintering mold, uniformly mixing the fiber raw material with a filler to form powder, and uniformly placing the mixed powder into the foam metal to enable the mixed powder to fill the foam metal pores;
step two, placing the sintering mold into a vacuum furnace for sintering for 30-50min;
and thirdly, taking out and demolding after cooling to below 100 ℃ along with a furnace after sintering, cleaning for 2-3 hours by adopting ultrasonic waves, and then drying to obtain the capillary core sample.
Further, the filler in the first step is NaCl or Na 2 CO 3 Or urea.
Further, in the first step, the solid volume ratio of the fiber raw material to the filler is 1: (0.6-1).
Further, in the first step, the solid volume ratio of the foam metal to the fiber raw material is 1: (1-3).
Further, in the second step, the sintering temperature is 40% -50% of the melting point of the fiber raw material.
Further, in the third step, the mixture is dried for 3 to 5 hours at the temperature of between 90 and 110 ℃.
3. Advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following remarkable effects:
(1) The foam metal-fiber composite capillary core applied to the loop heat pipe system has excellent heat transfer capacity: specifically, the foam metal skeleton has large-pore-diameter pores and small-pore-diameter pores formed among fibers; when the working medium flows in a single phase in the capillary core, the working medium is mainly performed in the foam metal framework, and the single-phase flow resistance is low; the fibers provide an attachment surface for the evaporation phase change interface, and the small-aperture pores formed among the fibers greatly increase the capillary suction force of the capillary core; in terms of heat transfer, the foam metal framework is prepared by modifying fibers, so that the half-open Kong Bikong in the capillary core is greatly reduced, and the porosity of the obtained capillary core is high in utilization rate; meanwhile, the wettability of the capillary core is enhanced, and the contact area with working media is enlarged; the fiber structure strengthens heat transfer and enhances evaporation of the phase change interface. Therefore, the foam metal-fiber composite capillary core is a high-performance capillary core with high permeability, high suction property and high surface evaporation property.
(2) The foam metal-fiber composite capillary core applied to the loop heat pipe system has the advantages of strong applicability, high porosity and high porosity utilization rate: specifically, the foam metal is taken as a framework, the foam metal can be finished through machining, the foam metal can be manufactured according to the shape and the size required by the capillary core, the sintering is not easy to deform, and the size and the shape are controllable; the amount of added fiber can be calculated based on the desired porosity. The foam metal framework is used as a support, and the prepared capillary core has higher mechanical strength and certain flexibility, and is more suitable for loop heat pipes. The foam metal is light in weight and high in porosity, and the self macropores are modified by adding some fibers, so that the internal pores of the foam metal are fully utilized, and the double-pore-diameter structure capillary core capable of simultaneously having macropores and micropores in the same space is obtained. Therefore, the capillary core provided by the invention is a double-aperture capillary core with strong applicability, light weight and high pore utilization rate.
(3) The foam metal-fiber composite capillary core applied to the loop heat pipe system has the advantages of small heat transfer area, lower heat conductivity and stable loop heat pipe operation temperature: specifically, the contact area of the fiber and the foam metal framework is small, and the sintered neck formed after sintering is small, so that the specific surface area of the capillary core is greatly increased, and the heat exchange area with working medium is increased; the heat transfer area is reduced, and the effective heat conductivity coefficient of the capillary core is reduced. The heat loaded to the evaporator is absorbed by the capillary core and transferred to the phase-change interface, and the heat is phase-changed by working medium in the capillary core to be taken away; the effective heat conductivity coefficient of the capillary core is low, the temperature of working medium in the compensation cavity is low due to back heat leakage, the running temperature of the loop heat pipe is reduced, and pressure and temperature fluctuation caused by bubble generation and collapse in the compensation cavity are reduced.
(4) The foam metal-fiber composite capillary core applied to the loop heat pipe system is beneficial to accelerating the starting of the loop heat pipe and stabilizing a phase change interface: specifically, the foam metal is made of a metal material with high heat conductivity, the heat transfer coefficient of the surface of the capillary core is high, and heat is conducted to the working medium of the capillary core to be absorbed and evaporated quickly; the foam metal framework greatly reduces the resistance of steam escape and stabilizes the phase change interface; the capillary core has small overall effective heat conductivity coefficient, small back heat leakage, small influence of heat on the temperature of the compensation cavity, slow internal pressure rising and quick establishment of pressure difference for starting operation of the whole system, and quickens the starting operation of the system. The fibers are attached to the foam metal framework, more attaching surfaces are provided for the phase change interface, more evaporation meniscus is formed, the evaporation phase change of the working medium is strengthened, meanwhile, the curvature radius of the meniscus is reduced, and the stability of the interface is enhanced.
Drawings
FIG. 1 is a schematic diagram of a prior art loop heat pipe;
FIG. 2 is a schematic diagram of a metal foam-fiber composite wick for loop heat pipes according to the present invention;
fig. 3 is a schematic diagram showing a phase change interface of a foam metal skeleton and a foam metal skeleton of a filling fiber according to the present invention, wherein (a) is a schematic diagram of a phase change interface of a metal skeleton, and (b) is a schematic diagram of a phase change interface of a metal skeleton of a filling fiber.
Schematic reference numeral description: 1. a fiber; 2. a foam metal skeleton; 3. fiber pores; 4. foam metal skeleton pores; 5. an evaporator; 6. a steam line; 7. a condenser; 8. a liquid line; 9. a compensation chamber; 10. a capillary wick; 11. a foam metal skeleton phase change meniscus; 12. fiber-filled foam metal phase-change meniscus.
Detailed Description
For a further understanding of the present invention, the present invention will be described in detail with reference to the drawings.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
The invention is further described below with reference to examples.
Example 1
As shown in fig. 2 and 3, a foam metal-fiber composite capillary core for a loop heat pipe system according to the present embodiment is a dual-pore porous medium structure, and includes: fiber 1, foam metal skeleton 2, fiber pore 3 and foam metal skeleton pore 4; the fiber 1 is distributed in the foam metal framework 2, the fiber 1 reforms the foam metal framework 2, small-aperture fiber pores 3 are formed among the fibers 1, large-aperture foam metal framework pores 4 are formed among the foam metal frameworks 2, namely, the foam metal frameworks 2 have large-aperture pores, and the fiber pores 3 exist in the foam metal framework pores 4, so that the capillary core simultaneously shows working medium flow characteristics shared by the large-aperture and the small-aperture pores in one space, namely, the small holes can increase the suction force of the capillary core, and the large holes reduce the working medium flow resistance.
In the embodiment, the foam metal skeleton 2 is made of foam metal materials with heat conductivity exceeding 100W/mK, such as foam copper, foam aluminum, foam silver and the like, the pore diameter of the foam metal is 50um, and the fiber 1 is made of metal materials with length-diameter ratio of 5 and length of 10 um; the foam metal and the fiber 1 are matched to form a high-performance capillary core with strong applicability, light weight, high porosity, high permeability, high suction performance, high surface evaporation rate and low effective heat conductivity coefficient, the foam metal forms a framework of the capillary core, the foam metal has large-aperture pores, and the foam metal has light weight, high porosity and high mechanical strength and has certain flexibility; the fiber 1 reforms the inner hole of the foam metal framework 2, fully utilizes the hole inside the capillary core, reduces the thickness and the quality of the capillary core, ensures that the capillary core has certain flexibility and enhances the applicability of the capillary core; secondly, the capillary core takes foam metal as a framework, pressurization is not needed in preparation, the risk of closed pores and semi-open pores generated due to more powder contact caused by pressurization is avoided, and meanwhile, the size and the filling quantity of the fiber 1 can be selected according to the suction force and the porosity required by the capillary core.
The processing method of the foam metal-fiber composite capillary core applied to the loop heat pipe system comprises the following steps of:
step one, preparing a fiber raw material and a foam metal raw material, placing the foam metal into a sintering mold, uniformly mixing the fiber raw material with a filler to form powder, and uniformly placing the mixed powder into the foam metal to enable the mixed powder to fill the foam metal pores;
specifically, preparing foam metal with the pore diameter of 50um and fiber metal material with the length-diameter ratio of 5 and the length of 10um, uniformly mixing the fiber metal with a filler, wherein the filler adopts NaCl, and the solid volume ratio of the fiber metal raw material to the filler is 1:0.6; the solid volume ratio of the foam metal raw material to the fiber metal raw material is 1:1, a step of; the porosity and the porosity of the capillary core are regulated by the filler, and the mixed powder is uniformly distributed by putting the mould into ultrasonic waves for 20-40min (30 min in the specific embodiment) after the fiber 1 fills the pores of the foam metal because the length of the fiber 1 is smaller than the pore diameter of the foam metal; the accurate proportion of each raw material is critical in the embodiment, and the fiber 1 is fully filled by strictly controlling the proportion of the raw materials, so that the defects of reduced porosity of a capillary core, increased heat conductivity, increased flow resistance, reduced running performance of a loop heat pipe, increased back heat leakage and the like caused by excessive filling of the fiber 1 are avoided; the defects of overlarge porosity of the capillary core, reduced number of pore channels of the capillary core, reduced capillary suction force of the capillary core, reduced number of meniscus of a phase change interface, increased curvature radius of the meniscus, reduced system operation stability and the like caused by the fact that the fiber 1 is too little are avoided, and the performance of the capillary core is comprehensively ensured.
Step two, placing the sintering mold into a vacuum furnace for sintering for 30min; specifically, the sintering temperature is 40-50% of the melting point of the fiber raw material; more specifically, the whole die is put into a vacuum furnace to be preheated to 350-400 ℃ (specifically, 350 ℃ in the embodiment), and is kept warm for 30-40min (30 min in the embodiment) and then is continuously heated to 40-50% of the melting point of the fiber raw material, and is kept warm for 30-40min (30 min in the embodiment), so that the fibers 1 and the fibers 1 are bonded with the foam metal skeleton 2; when the temperature reaches 40% of the melting point of the fiber raw material, the powder contact part starts to fuse, and when the temperature reaches 50%, the powder sintering neck phenomenon appears, so that the capillary core has certain strength.
And thirdly, cooling the capillary core to below 100 ℃ along with a furnace after sintering, taking out and demolding, cleaning with deionized water by adopting ultrasonic waves for 2 hours until the filler is cleaned, and then putting into a drying box for drying for 3 hours at the temperature of 100 ℃ to obtain a capillary core sample.
When the capillary core of the embodiment works in a system, heat is loaded into the capillary core 10 by the evaporator 5, a working medium forms a gas-liquid interface in the capillary core 10, the fiber 1 and the foam metal framework 2 provide an adhesion surface for the gas-liquid interface, the pore diameter of the fiber pore 3 is smaller, the stability of the interface is enhanced, meanwhile, the heat exchange area is increased, the heating of the working medium is facilitated, the evaporation phase change is promoted, the heat is taken away, and the back leakage heat is reduced. As shown in fig. 3 in comparison, in the fig. (a), the phase change interface is simply attached to the foam metal skeleton 2, the pore diameter of the foam metal skeleton pore 4 is larger, and the capillary suction force and the quantity of phase change meniscus 11 of the foam metal skeleton can be provided are smaller; in the figure (b), the fiber 1 reforms the inner pore diameter of the foam metal skeleton 2, the phase change interface is attached between the foam metal skeleton 2 and the fiber 1, the formed small pore diameter can provide larger capillary suction force, and meanwhile, the existence of the fiber 1 provides more attaching surfaces for the foam metal skeleton 2, more foam metal phase change meniscus 12 filled with the fiber is formed, and the stability of the interface is enhanced.
When the loop heat pipe system operates in the embodiment, the larger foam metal skeleton pores 4 in the foam metal skeleton 2 are beneficial to the flow of working media, and the vapor subjected to phase change is quickly separated from the evaporator 5, so that the system resistance is effectively reduced, and the system stability is increased; the smaller fiber pores 3 among the fibers 1 increase the suction force of the capillary core 10, the working medium with phase change is timely supplemented, the phase change interface is stable in a certain range, and the risk that the system cannot operate due to deeper movement of the phase change interface of the capillary core 10 is greatly reduced; and the evaporation rate of the capillary core 10 is higher, so that most of heat of electronic elements is taken away due to phase change of working media, and meanwhile, the effective heat conductivity coefficient of the capillary core 10 is lower, so that the back heat leakage of the system is effectively reduced, and the system is more stable.
It should be noted that, the capillary wick 10 in this embodiment has an excellent heat transfer capability, and the specific analysis is as follows: the foam metal skeleton 2 is provided with large-aperture pores and small-aperture pores formed among the fibers 1, when working medium flows in a single phase in the capillary core 10, the working medium is mainly carried out in the foam metal skeleton 2, the single-phase flow resistance is low, the fibers 1 provide an attachment surface for an evaporation phase change interface, and the capillary suction force of the capillary core 10 is greatly increased by the small-aperture pores among the fibers 1; in terms of heat transfer, the foam metal framework 2 is modified by the fiber 1, so that the semi-open holes and closed holes in the capillary core 10 are greatly reduced, the porosity and the utilization rate of the capillary core 10 are higher, the wettability of the capillary core 10 is enhanced, and the contact area with working media is enlarged; the structure of the fiber 1 is favorable for enhancing heat transfer and enhancing evaporation of a phase change interface; therefore, the foam metal-fiber composite wick of the present embodiment is a high-performance wick with high permeability, high suction property, high surface evaporation property.
Secondly, the foam metal-fiber composite capillary core of the embodiment is prepared by taking foam metal as a framework, the foam metal can be machined and finished, the foam metal can be machined and manufactured according to the required shape and size of the capillary core 10, the sintering is not easy to deform, and the addition amount of the fiber 1 can be calculated according to the required porosity, so that the porosity, the size and the appearance of the capillary core 10 are easy to control; secondly, the foam metal framework 2 is used as a support, and the prepared capillary core 10 has higher mechanical strength and certain flexibility and is more suitable for loop heat pipes; and thirdly, the foam metal is light in weight and high in porosity, the fiber 1 is added to modify the macropores of the foam metal, the internal pores of the foam metal are fully utilized, and finally the light and high-porosity dual-pore capillary core is prepared.
And the foam metal-fiber composite capillary core of the embodiment also has the performances of small heat transfer area, lower heat conductivity and the like, and can stabilize the running temperature of the loop heat pipe. In particular, many scholars have conducted extensive research on loop heat pipe temperature wave action, and consider that compensating for pressure and temperature fluctuations within the cavity is a major factor in system operating temperature fluctuations; the foam metal-fiber composite capillary core of the embodiment has small contact area between the fiber 1 and the foam metal framework 2, and the sintered neck formed after sintering is small, so that the specific surface area of the capillary core 10 is greatly increased, and the heat exchange area with working media is increased; at the same time, the heat transfer area is reduced, and the effective heat conductivity of the capillary wick 10 is reduced. The heat loaded to the evaporator 5 is absorbed by the capillary core 10 and transferred to the phase change interface, and the heat is phase-changed by working medium in the capillary core 10 to be taken away; the effective heat conductivity coefficient of the capillary core 10 is reduced, and the temperature of working medium in the compensation cavity 9 is lower due to back heat leakage, so that the operating temperature of the loop heat pipe is reduced, and meanwhile, pressure and temperature fluctuation caused by bubble generation and collapse in the compensation cavity 9 are reduced.
Finally, the foam metal-fiber composite capillary core of the embodiment is also beneficial to accelerating the starting of the loop heat pipe and stabilizing the phase change interface. Specifically, the foam metal is made of a metal material with high heat conductivity, the heat transfer coefficient of the surface of the capillary core 10 is high, and the heat is transferred to the capillary core 10 to be absorbed and evaporated quickly; the foam metal framework 2 greatly reduces the resistance of steam escape and stabilizes the phase change interface; the capillary core 10 has smaller overall effective heat conductivity coefficient, smaller back heat leakage, smaller influence of heat on the temperature of the compensation cavity 9, slower internal pressure rise, and the whole system quickly establishes pressure difference for starting operation, thereby accelerating the starting operation of the system; the fiber 1 is attached to the foam metal framework 2, more attaching surfaces are provided for the phase change interface, more evaporation meniscus is formed, the evaporation phase change of the working medium is enhanced, meanwhile, the curvature radius of the meniscus is reduced, and the stability of the interface is enhanced.
Example 2
The basic structure of the foam metal-fiber composite capillary core applied to the loop heat pipe system in this embodiment is the same as that in embodiment 1, except that the foam metal skeleton in this embodiment is made of foam metal material with aperture of 150um, and the fiber is made of metal material with length-diameter ratio of 10 and length of 40 um.
The processing method of the foam metal-fiber composite capillary core applied to the loop heat pipe system in this embodiment is basically the same as that in embodiment 1, except that:
in the first step, the filling agent is Na 2 CO 3 Selecting foam metal with pore diameter of 150umA material, and a fiber metal material with an aspect ratio of 10 and a length of 40um, wherein the solid volume ratio of the fiber raw material to the filler is 1:1, the solid volume ratio of foam metal to fiber raw material is 1:3, a step of; after foam metal pores in the mould are filled, putting the mould into ultrasonic waves for 20min to uniformly distribute mixed powder;
step two, placing the sintering die into a vacuum furnace for sintering for 50min, specifically, firstly placing the whole die into the vacuum furnace for preheating to 400 ℃, keeping the temperature for 40min, then continuously heating to 40-50% of the melting point of the fiber raw material, and keeping the temperature for 40min;
and step three, ultrasonic cleaning is adopted for 3 hours, and drying is carried out at 110 ℃ for 5 hours.
Example 3
The basic structure of the foam metal-fiber composite capillary core applied to the loop heat pipe system in this embodiment is the same as that in embodiment 1, except that the foam metal skeleton in this embodiment is made of foam metal material with aperture of 100um, and the fiber is made of metal material with length-diameter ratio of 8 and length of 30 um.
The processing method of the foam metal-fiber composite capillary core applied to the loop heat pipe system in this embodiment is basically the same as that in embodiment 1, except that:
in the first step, the filler is urea, foam metal material with the aperture of 100um and fiber metal material with the length-diameter ratio of 8 and the length of 30um are selected, and the solid volume ratio of the fiber raw material to the filler is 1:0.8, the solid volume ratio of foam metal to fiber raw material is 1:2; after foam metal pores in the mould are filled, putting the mould into ultrasonic waves for 40min to uniformly distribute mixed powder;
step two, placing the sintering die into a vacuum furnace for sintering for 40min, specifically, firstly placing the whole die into the vacuum furnace for preheating to 360 ℃, keeping the temperature for 35min, then continuously heating to 40-50% of the melting point of the fiber raw material, and keeping the temperature for 35min;
and step three, ultrasonic cleaning is adopted for 2.5 hours, and drying is carried out at the temperature of 90 ℃ for 4 hours.
The invention and its embodiments have been described above by way of illustration and not limitation, and the invention is illustrated in the accompanying drawings and described in the drawings in which the actual structure is not limited thereto. Therefore, if one of ordinary skill in the art is informed by this disclosure, the structural mode and the embodiments similar to the technical scheme are not creatively designed without departing from the gist of the present invention.
Claims (6)
1. A processing method of a foam metal-fiber composite capillary core applied to a loop heat pipe system is characterized by comprising the following steps of: the capillary core is a dual-aperture porous medium structure, comprising: the foam metal framework comprises fibers (1), foam metal frameworks (2), fiber pores (3) and foam metal framework pores (4); the fibers (1) are distributed in the foam metal frameworks (2), small-pore-diameter fiber pores (3) are formed among the fibers (1), and large-pore-diameter foam metal framework pores (4) are formed among the foam metal frameworks (2); the foam metal framework (2) is made of foam metal materials with the heat conductivity exceeding 100W/mK; the foam metal framework (2) adopts foam metal materials with the pore diameter of 50-150 um; the fiber (1) adopts a metal material with the length-diameter ratio of 5-10 and the length of 10-40 um;
the processing method comprises the following steps:
step one, preparing a fiber raw material and a foam metal raw material, placing the foam metal into a sintering mold, uniformly mixing the fiber raw material with a filler to form powder, and uniformly placing the mixed powder into the foam metal to enable the mixed powder to fill the foam metal pores;
step two, placing the sintering mold into a vacuum furnace for sintering for 30-50min;
and thirdly, taking out and demolding after cooling to below 100 ℃ along with a furnace after sintering, cleaning for 2-3 hours by adopting ultrasonic waves, and then drying to obtain the capillary core sample.
2. The method for processing the foam metal-fiber composite capillary core applied to the loop heat pipe system according to claim 1, wherein the method comprises the following steps of: the filler in the first step is NaCl, na 2 CO 3 Or urea.
3. The method for processing the foam metal-fiber composite capillary core applied to the loop heat pipe system according to claim 1, wherein the method comprises the following steps of: in the first step, the solid volume ratio of the fiber raw material to the filler is 1: (0.6-1).
4. A method of manufacturing a metal foam-fiber composite wick for use in a loop heat pipe system according to claim 3, wherein: in the first step, the solid volume ratio of the foam metal to the fiber raw material is 1: (1-3).
5. A method for processing a foam metal-fiber composite capillary core applied to a loop heat pipe system according to any one of claims 1-3, wherein: the sintering temperature in the second step is 40% -50% of the melting point of the fiber raw material.
6. A method for processing a foam metal-fiber composite capillary core applied to a loop heat pipe system according to any one of claims 1-3, wherein: and step three, drying for 3 to 5 hours at the temperature of between 90 and 110 ℃.
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| CN110267493B (en) * | 2019-06-12 | 2023-12-01 | 华南理工大学 | Flexible ultrathin liquid absorption core with hierarchical porous structure and manufacturing method thereof |
| CN110303153B (en) * | 2019-06-28 | 2021-04-27 | 安泰环境工程技术有限公司 | Method for processing capillary core and method for assembling capillary core and tube shell |
| CN111185725B (en) * | 2020-01-10 | 2021-07-23 | 中国矿业大学 | Gradient-aperture porous copper liquid absorption core for loop heat pipe and preparation method thereof |
| CN111189346B (en) * | 2020-01-10 | 2021-06-08 | 中国矿业大学 | Porous copper-wood fiber/polystyrene double-layer composite capillary core for loop heat pipe and preparation method thereof |
| CN111442674B (en) * | 2020-03-17 | 2021-10-26 | 广州视源电子科技股份有限公司 | Method for processing heat dissipation plate |
| EP4019252A1 (en) * | 2020-12-23 | 2022-06-29 | ABB Schweiz AG | Heat-transfer device and method to produce such a device |
| CN115351280B (en) * | 2022-08-22 | 2024-01-19 | 西北有色金属研究院 | Integrated preparation method of evaporator for loop heat pipe |
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