With the rapid development of two-phase heat exchangers,the further improvement of the capillary performance of their internal wick faces a great challenge.As an important technology in the surface treatment of alumin...With the rapid development of two-phase heat exchangers,the further improvement of the capillary performance of their internal wick faces a great challenge.As an important technology in the surface treatment of aluminum alloys,anodic oxidation has been widely used to develop various functional nanostructures.In this study,nanopores with diameters of 30–40 nm were fabricated on the surface of aluminum fibers through anodic oxidation under an oxalic acid system.Results showed that anodizing increased the specific surface area of the aluminum braid by 163 times,and changed its surface wettability from hydrophobic to superhydrophilic.A significant reduction in the effective capillary radius can substantially increase the capillary force of aluminum braids on the basis of capillary theory.Therefore,the nanoporous aluminum braids can be used as a novel wick in the vapor chamber to improve its capillary performance.Capillary rate-of-rise tests with ethanol and acetone were performed to characterize the capillary of this novel wick structure.Infrared thermal imaging was utilized to monitor the capillary rise of aluminum braided wicks.The capillary force of the anodized wicks was greater than that of a normal wick,and the maximum capillary rise height was 81 mm.The nanoporous aluminum braided wicks prepared by anodizing could be applied in heat transfer.展开更多
The present study fabricated a series of capillary wicks for loop heat pipes (LHPs), using two different methods, the cold-pressing sintering and direct loose sintering, and experimentally investigated the effect of d...The present study fabricated a series of capillary wicks for loop heat pipes (LHPs), using two different methods, the cold-pressing sintering and direct loose sintering, and experimentally investigated the effect of different methods, compositions and sintering parameters on their properties in terms of porosity, permeability and pore radius. Porosity and pore radius were measured by the Archimedes method and Scanning Electron Microscope (SEM), respectively. Permeability of the wicks was compared by calculation using empirical equation. Results show that capillary wicks were successfully fabricated by using two different methods; the optimal capillary wick was found to be sintered at 650°C for 30 min, using direct loose sintering technique, with 90% nickel and 10% copper. The wicks could reach the porosity of 70.07% and the permeability of 10?13 m2 order, with mean pore radius of 0.54 μm.展开更多
Oxide-reduced copper powder can be produced efficiently at low cost. The volume shrinkage, porosity, maximum pore size, permeability and thermal conductivity of wicks sintered from two oxide-reduced （OR） powders wer...Oxide-reduced copper powder can be produced efficiently at low cost. The volume shrinkage, porosity, maximum pore size, permeability and thermal conductivity of wicks sintered from two oxide-reduced （OR） powders were compared with one from water-atomized （WA） powder. The green specimens were sintered at temperatures from 800 to 1000 ℃ in a tube furnace under a reduction stream of 10% hydrogen and 90% argon. The results show that the property variations of OR - 100 and WA wicks due to porosity changes have a similar tendency and range. Nine hundred degree celsius is a recommended sintering temperature for producing ideal wicks for use in heat pipes. A smaller maximum pore size can be obtained by increasing the green density.2007 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V.展开更多
The possibility of mimicking desirable properties from nature accelerates material improvement and generates commercial interests. For heat pipe development, many attempts have been made in heat pipe wicks to enhance ...The possibility of mimicking desirable properties from nature accelerates material improvement and generates commercial interests. For heat pipe development, many attempts have been made in heat pipe wicks to enhance its capillary performance by mimicking biology. Constructing biporous, composite, or nanopillar wicks with aim of achieving hierarchical structure has been found in many studies. Mimicking beetle shell surface to obtain hybrid wettability shows biomimetic potential in heat pipe wicks. This paper firstly reviews some fundamental studies in biomimetics, establishing a general idea of surface wetting and capillary effect. MR/scanning of two live plants （Musa X Paradisiaca and Salix Flamingo） provides the possibility of visualising internal structures in vivo and obtaining rates of water transport in xylem vessels. In addition, by investigating the work inspired directly or indirectly from biomimetics, the role that biomimetics plays in modern heat pipe technology is revealed. Our innovation which syntheses a low level of hierarchical structure and integrates integral wicks for different heat pipe sections including evaporator, adiabatic, and condenser is introduced. Mathematical modelling in terms of capillary pressure and capillary rise rate to characterise such new structure is provided.展开更多
Electronic skins can monitor minute physiological signal variations in the human skins and represent the body’s state,showing an emerging trend for alternative medical diagnostics and human-machine interfaces.In this...Electronic skins can monitor minute physiological signal variations in the human skins and represent the body’s state,showing an emerging trend for alternative medical diagnostics and human-machine interfaces.In this study,we designed a bioinspired directional moisture-wicking electronic skin(DMWES)based on the construction of heterogeneous fibrous membranes and the conductive MXene/CNTs electrospraying layer.Unidirectional moisture transfer was successfully realized by surface energy gradient and push-pull effect via the design of distinct hydrophobic-hydrophilic difference,which can spontaneously absorb sweat from the skin.The DMWES membrane showed excellent comprehensive pressure sensing performance,high sensitivity(maximum sensitivity of 548.09 kPa^(−1)),wide linear range,rapid response and recovery time.In addition,the single-electrode triboelectric nanogenerator based on the DMWES can deliver a high areal power density of 21.6μW m^(−2) and good cycling stability in high pressure energy harvesting.Moreover,the superior pressure sensing and triboelectric performance enabled the DMWES for all-range healthcare sensing,including accurate pulse monitoring,voice recognition,and gait recognition.This work will help to boost the development of the next-generation breathable electronic skins in the applications of AI,human-machine interaction,and soft robots.展开更多
The Lady of Shalott is considered to be one of Alfred Lord Tennyson’s masterpieces.The poem conversely demonstrates art and life,the aesthetic and the political,are fully interwoven:the involvement in the social worl...The Lady of Shalott is considered to be one of Alfred Lord Tennyson’s masterpieces.The poem conversely demonstrates art and life,the aesthetic and the political,are fully interwoven:the involvement in the social world which is symbolically the destination of the Lady in the poem.The Lady who is the emblem of such an artwork can be ascribed qualities,for instance,self-containment,objectified otherness,removal from the fluidity of life,and participation in a higher order of existence,for which it is autonomy.Kermode points out that“the Romantic artwork often identifies itself with an emblematic image of autonomy and femininity”,inextricably interlinked.Her mirror shows her only“Shadows of the world”.The Lady’s web flies“Out”and floats“wide”when she“turns round”with“that desire of making an impression upon another mind”,when she seeks to address Lancelot.The mirror reconnects the Lady’s art to the real world beyond her window.Though the artist is unable to see it during the process of production,her artistic web,once out in a wider space than the tower and freed from the loom,is a true representation of outward things,the actions,and events of Camelot.This paper examines that the traditional referentiality of Tennyson’s‘The Lady of Shalott’can be better understood by supplementing the poet’s medieval sources,of little more than tangential relevance to the poem,with Homeric influences.The poem is similar to a fairytale,however,I have given an alternate reality of the Lady of Shallot in my version of a fairytale,where the characters remain the same but the fairytale takes a happy ending rather than a tragic death.My version is different from Tennyson’s since I believe the lady deserves to be jovial.Sir Lancelot was unaware of her fascination and feelings for him,as she could hardly express her feelings due to her imprisonment.She is so taken by him that she stops her work and looks at Camelot,though she risks the mysterious curse.The mirror breaks and her web magically floats out of the window on its own.She realizes that she is cursed.展开更多
Miniature cylindrical metal powder sintered wick heat pipe （sintered heat pipe） is an ideal component with super-high thermal efficiency for high heat flux electronics cooling. The sintering process for sintered wic...Miniature cylindrical metal powder sintered wick heat pipe （sintered heat pipe） is an ideal component with super-high thermal efficiency for high heat flux electronics cooling. The sintering process for sintered wick is important for its quality. The sintering process was optimally designed based on the equation of the heat transfer limit of sintered heat pipe. Four-step sintering process was proposed to fabricate sintered wick. The sintering parameters including sintering temperature, sintering time, sintering atmosphere and sintering position were discussed. The experimental results showed that the proper sintering temperature was 950 ℃ for Cu powder of 159μm and 900 ℃ for Cu powders of 81 and 38 μm, respectively, while the wick thickness was 0.45 mm and sintering time was 3 h. The optimized sintering time was 3 h for 0.45 and 0.6 mm wick thickness and 1 h for 0.75 mm wick thickness, respectively, when copper powder diameter was 159μm and sintering temperature was 950 ℃. Redox reduction reaction between H2 and CuO during sintering could produce segmentation cracks in Cu powders as a second structure. Sintering at vertical position can effectively avoid the generation of gap between wick and the inner wall of pipe.展开更多
The intensified boiling and condensation wick structures of heat column were designed and manufactured by ploughing-extrusion （P-E） machining method.The forming process and mechanism were analyzed.The results show t...The intensified boiling and condensation wick structures of heat column were designed and manufactured by ploughing-extrusion （P-E） machining method.The forming process and mechanism were analyzed.The results show that the P-E depth plays a decisive role in forming of wick structure.The larger the P-E depth is,the better the surface characteristics are.Only when the groove spacing is in a certain range,superior surface structure can be formed in the wick.The better enhancement boiling structure forms at P-E depth of 0.3 mm,ringed groove spacing of 0.4 mm,and interior angle of radial groove of 3°;the better enhancement condensation structure forms at P-E depth of 0.3 mm,ringed groove spacing of 0.4 mm,and axial grooves spacing of π/3 mm.展开更多
With the rapid rising of heat flux and reduction of heat dissipating space of microelectronic devises, flattened sintered heat pipe has become an ideal conducting element of use in the electronic cooling field. A manu...With the rapid rising of heat flux and reduction of heat dissipating space of microelectronic devises, flattened sintered heat pipe has become an ideal conducting element of use in the electronic cooling field. A manufacturing technology named phase change flattening process is presented to fabricate the flattened grooved-sintered wick heat pipe （GSHP for short）. Deformation geometry of flattened GSHP and the elasto-plastic deformation of flattening process are analyzed theoretically and verified by experiments. The results show that the vapor pressure inside sintered heat pipe during flattening process is determined by the saturated vapor pressure equation; the width and vapor area of flattened heat pipe change greatly as the flattening proceeds; the maximum equivalent strain distributes at the interface between wick and vapor in the fiat section; the buckling phenomenon can be well eliminated when the flattening temperature reaches 480 K; phase change flattening punch load increases with flattening temperature and displacement.展开更多
A novel phase change heat sink was fabricated for packaging cooling of high power light emitting diode （LED）. 3D structures as enhanced boiling structure in the evaporation surface were composed of a spiral micro-gr...A novel phase change heat sink was fabricated for packaging cooling of high power light emitting diode （LED）. 3D structures as enhanced boiling structure in the evaporation surface were composed of a spiral micro-groove along circumferential direction and radial micro-grooves which were processed by ploughing-extrusion （P-E） and stamping, respectively. Meanwhile, the cycle power of refrigerant was supplied by wick of sintered copper powder on internal surface of phase change heat sink. Operational characteristics were tested under different heat loads and refrigerants. The experimental results show that phase change heat sink is provided with a good heat transfer capability and the temperature of phase change heat sink reaches 86.8 ℃ under input power of 10 W LED at ambient temperature of 20 ℃.展开更多
基金the Natural Science Foundation of Guangdong Province,China(No.2021B1515020087)the National Natural Science Foundation of China(No.51775197).
文摘With the rapid development of two-phase heat exchangers,the further improvement of the capillary performance of their internal wick faces a great challenge.As an important technology in the surface treatment of aluminum alloys,anodic oxidation has been widely used to develop various functional nanostructures.In this study,nanopores with diameters of 30–40 nm were fabricated on the surface of aluminum fibers through anodic oxidation under an oxalic acid system.Results showed that anodizing increased the specific surface area of the aluminum braid by 163 times,and changed its surface wettability from hydrophobic to superhydrophilic.A significant reduction in the effective capillary radius can substantially increase the capillary force of aluminum braids on the basis of capillary theory.Therefore,the nanoporous aluminum braids can be used as a novel wick in the vapor chamber to improve its capillary performance.Capillary rate-of-rise tests with ethanol and acetone were performed to characterize the capillary of this novel wick structure.Infrared thermal imaging was utilized to monitor the capillary rise of aluminum braided wicks.The capillary force of the anodized wicks was greater than that of a normal wick,and the maximum capillary rise height was 81 mm.The nanoporous aluminum braided wicks prepared by anodizing could be applied in heat transfer.
基金Supported by Shandong Provincial Program of Science and Technology Develop-ment(Grant No.2007GG1HZ06004)
文摘The present study fabricated a series of capillary wicks for loop heat pipes (LHPs), using two different methods, the cold-pressing sintering and direct loose sintering, and experimentally investigated the effect of different methods, compositions and sintering parameters on their properties in terms of porosity, permeability and pore radius. Porosity and pore radius were measured by the Archimedes method and Scanning Electron Microscope (SEM), respectively. Permeability of the wicks was compared by calculation using empirical equation. Results show that capillary wicks were successfully fabricated by using two different methods; the optimal capillary wick was found to be sintered at 650°C for 30 min, using direct loose sintering technique, with 90% nickel and 10% copper. The wicks could reach the porosity of 70.07% and the permeability of 10?13 m2 order, with mean pore radius of 0.54 μm.
文摘Oxide-reduced copper powder can be produced efficiently at low cost. The volume shrinkage, porosity, maximum pore size, permeability and thermal conductivity of wicks sintered from two oxide-reduced （OR） powders were compared with one from water-atomized （WA） powder. The green specimens were sintered at temperatures from 800 to 1000 ℃ in a tube furnace under a reduction stream of 10% hydrogen and 90% argon. The results show that the property variations of OR - 100 and WA wicks due to porosity changes have a similar tendency and range. Nine hundred degree celsius is a recommended sintering temperature for producing ideal wicks for use in heat pipes. A smaller maximum pore size can be obtained by increasing the green density.2007 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences. Published by Elsevier B.V.
文摘The possibility of mimicking desirable properties from nature accelerates material improvement and generates commercial interests. For heat pipe development, many attempts have been made in heat pipe wicks to enhance its capillary performance by mimicking biology. Constructing biporous, composite, or nanopillar wicks with aim of achieving hierarchical structure has been found in many studies. Mimicking beetle shell surface to obtain hybrid wettability shows biomimetic potential in heat pipe wicks. This paper firstly reviews some fundamental studies in biomimetics, establishing a general idea of surface wetting and capillary effect. MR/scanning of two live plants （Musa X Paradisiaca and Salix Flamingo） provides the possibility of visualising internal structures in vivo and obtaining rates of water transport in xylem vessels. In addition, by investigating the work inspired directly or indirectly from biomimetics, the role that biomimetics plays in modern heat pipe technology is revealed. Our innovation which syntheses a low level of hierarchical structure and integrates integral wicks for different heat pipe sections including evaporator, adiabatic, and condenser is introduced. Mathematical modelling in terms of capillary pressure and capillary rise rate to characterise such new structure is provided.
基金support from the Contract Research(“Development of Breathable Fabrics with Nano-Electrospun Membrane,”CityU ref.:9231419)the National Natural Science Foundation of China(“Study of Multi-Responsive Shape Memory Polyurethane Nanocomposites Inspired by Natural Fibers,”Grant No.51673162)+1 种基金Startup Grant of CityU(“Laboratory of Wearable Materials for Healthcare,”Grant No.9380116)National Natural Science Foundation of China,Grant No.52073241.
文摘Electronic skins can monitor minute physiological signal variations in the human skins and represent the body’s state,showing an emerging trend for alternative medical diagnostics and human-machine interfaces.In this study,we designed a bioinspired directional moisture-wicking electronic skin(DMWES)based on the construction of heterogeneous fibrous membranes and the conductive MXene/CNTs electrospraying layer.Unidirectional moisture transfer was successfully realized by surface energy gradient and push-pull effect via the design of distinct hydrophobic-hydrophilic difference,which can spontaneously absorb sweat from the skin.The DMWES membrane showed excellent comprehensive pressure sensing performance,high sensitivity(maximum sensitivity of 548.09 kPa^(−1)),wide linear range,rapid response and recovery time.In addition,the single-electrode triboelectric nanogenerator based on the DMWES can deliver a high areal power density of 21.6μW m^(−2) and good cycling stability in high pressure energy harvesting.Moreover,the superior pressure sensing and triboelectric performance enabled the DMWES for all-range healthcare sensing,including accurate pulse monitoring,voice recognition,and gait recognition.This work will help to boost the development of the next-generation breathable electronic skins in the applications of AI,human-machine interaction,and soft robots.
文摘The Lady of Shalott is considered to be one of Alfred Lord Tennyson’s masterpieces.The poem conversely demonstrates art and life,the aesthetic and the political,are fully interwoven:the involvement in the social world which is symbolically the destination of the Lady in the poem.The Lady who is the emblem of such an artwork can be ascribed qualities,for instance,self-containment,objectified otherness,removal from the fluidity of life,and participation in a higher order of existence,for which it is autonomy.Kermode points out that“the Romantic artwork often identifies itself with an emblematic image of autonomy and femininity”,inextricably interlinked.Her mirror shows her only“Shadows of the world”.The Lady’s web flies“Out”and floats“wide”when she“turns round”with“that desire of making an impression upon another mind”,when she seeks to address Lancelot.The mirror reconnects the Lady’s art to the real world beyond her window.Though the artist is unable to see it during the process of production,her artistic web,once out in a wider space than the tower and freed from the loom,is a true representation of outward things,the actions,and events of Camelot.This paper examines that the traditional referentiality of Tennyson’s‘The Lady of Shalott’can be better understood by supplementing the poet’s medieval sources,of little more than tangential relevance to the poem,with Homeric influences.The poem is similar to a fairytale,however,I have given an alternate reality of the Lady of Shallot in my version of a fairytale,where the characters remain the same but the fairytale takes a happy ending rather than a tragic death.My version is different from Tennyson’s since I believe the lady deserves to be jovial.Sir Lancelot was unaware of her fascination and feelings for him,as she could hardly express her feelings due to her imprisonment.She is so taken by him that she stops her work and looks at Camelot,though she risks the mysterious curse.The mirror breaks and her web magically floats out of the window on its own.She realizes that she is cursed.
基金Project(50905119)supported by the National Natural Science Foundation of ChinaProject(20120171120036)supported by New Teachers'Fund for Doctor Stations,Ministry of Education,ChinaProject(S2012040007715)supported by Natural Science Foundation of Guangdong Province,China
文摘Miniature cylindrical metal powder sintered wick heat pipe （sintered heat pipe） is an ideal component with super-high thermal efficiency for high heat flux electronics cooling. The sintering process for sintered wick is important for its quality. The sintering process was optimally designed based on the equation of the heat transfer limit of sintered heat pipe. Four-step sintering process was proposed to fabricate sintered wick. The sintering parameters including sintering temperature, sintering time, sintering atmosphere and sintering position were discussed. The experimental results showed that the proper sintering temperature was 950 ℃ for Cu powder of 159μm and 900 ℃ for Cu powders of 81 and 38 μm, respectively, while the wick thickness was 0.45 mm and sintering time was 3 h. The optimized sintering time was 3 h for 0.45 and 0.6 mm wick thickness and 1 h for 0.75 mm wick thickness, respectively, when copper powder diameter was 159μm and sintering temperature was 950 ℃. Redox reduction reaction between H2 and CuO during sintering could produce segmentation cracks in Cu powders as a second structure. Sintering at vertical position can effectively avoid the generation of gap between wick and the inner wall of pipe.
基金Project(U0834002) supported by the Joint Funds of NSFC-Guangdong of ChinaProject(2009ZM0121) supported by the Fundamental Research Funds for the Central Universities,China
文摘The intensified boiling and condensation wick structures of heat column were designed and manufactured by ploughing-extrusion （P-E） machining method.The forming process and mechanism were analyzed.The results show that the P-E depth plays a decisive role in forming of wick structure.The larger the P-E depth is,the better the surface characteristics are.Only when the groove spacing is in a certain range,superior surface structure can be formed in the wick.The better enhancement boiling structure forms at P-E depth of 0.3 mm,ringed groove spacing of 0.4 mm,and interior angle of radial groove of 3°;the better enhancement condensation structure forms at P-E depth of 0.3 mm,ringed groove spacing of 0.4 mm,and axial grooves spacing of π/3 mm.
基金Project(50905119)supported by the National Natural Science Foundation of ChinaProject(2012M510205)supported by China Postdoctoral Science Foundation+1 种基金Project(PEMT1206)supported by the Open Foundation of Guangdong Province Key Laboratory of Precision Equipment and Manufacturing Technology,ChinaProject(S2012040007715)supported by Natural Science Foundation of Guangdong Province,China
文摘With the rapid rising of heat flux and reduction of heat dissipating space of microelectronic devises, flattened sintered heat pipe has become an ideal conducting element of use in the electronic cooling field. A manufacturing technology named phase change flattening process is presented to fabricate the flattened grooved-sintered wick heat pipe （GSHP for short）. Deformation geometry of flattened GSHP and the elasto-plastic deformation of flattening process are analyzed theoretically and verified by experiments. The results show that the vapor pressure inside sintered heat pipe during flattening process is determined by the saturated vapor pressure equation; the width and vapor area of flattened heat pipe change greatly as the flattening proceeds; the maximum equivalent strain distributes at the interface between wick and vapor in the fiat section; the buckling phenomenon can be well eliminated when the flattening temperature reaches 480 K; phase change flattening punch load increases with flattening temperature and displacement.
基金Projects(50436010,50930005)supported by the National Natural Science Foundation of ChinaProject(U0834002)supported by the Joint Fund of NSFC-Guangdong of China
文摘A novel phase change heat sink was fabricated for packaging cooling of high power light emitting diode （LED）. 3D structures as enhanced boiling structure in the evaporation surface were composed of a spiral micro-groove along circumferential direction and radial micro-grooves which were processed by ploughing-extrusion （P-E） and stamping, respectively. Meanwhile, the cycle power of refrigerant was supplied by wick of sintered copper powder on internal surface of phase change heat sink. Operational characteristics were tested under different heat loads and refrigerants. The experimental results show that phase change heat sink is provided with a good heat transfer capability and the temperature of phase change heat sink reaches 86.8 ℃ under input power of 10 W LED at ambient temperature of 20 ℃.
