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 column wicking technique was applied to estimate the surface free energy of cellulose, the importance of which is to obtain a real effective capillary radius, Reff, initially from the plot of Washburn penetration ...The column wicking technique was applied to estimate the surface free energy of cellulose, the importance of which is to obtain a real effective capillary radius, Reff, initially from the plot of Washburn penetration distance versus time. Since the cellulose sample could not be packed with good reproducibility, therefore, Reff can not be obtained readily from the slope of the plot. A method was developed in this paper by uniting all apparent packing heights with a unique value to deduce a real effective capillary radius. Based on the defined critical packing height related to the critical packing density, the surface free energy and acid-base properties of cellulose Sigma C8002 were estimated.展开更多
Wicking geotextile(WG)is considered as a possible countermeasure to reduce water content in unsaturated soil.In this research,rainfall tests were carried out to verify the drainage performance of WG.And capillary rise...Wicking geotextile(WG)is considered as a possible countermeasure to reduce water content in unsaturated soil.In this research,rainfall tests were carried out to verify the drainage performance of WG.And capillary rise tests were conducted to study the effect of WG on the prevention of capillary rise.Test results indicated that WG with good drainage performance could drain gravitational and capillary water out of kaolinite soil.For kaolinite soil column with water content of 12%and compaction degree of 90%,the whole process of capillary rise in soil column with a layer of WG was a typical two-stage mode,and the maximum capillary height was about 380 mm,which provided that the WG could work as a barrier to prevent capillary rise effectively.In addition,the total vertical influential regions of WG in kaolinite soil above and below the WG layer were 400 and 100 mm,respectively.展开更多
After a brief review of existing methods for fabric wetting and wicking measurement,a new numerical approach based on dynamic image acquisition and analysis was proposed to study the liquid wetting and wicking propert...After a brief review of existing methods for fabric wetting and wicking measurement,a new numerical approach based on dynamic image acquisition and analysis was proposed to study the liquid wetting and wicking properties of woven fabrics.A measuring system was first developed to record on-site the images of liquid ascending in fabrics for a certain period of time.The hardware and software platforms and the experimental methods were described,and the image processing and analysis as well as other related algorithms were discussed in detail.The liquid front curves and rising rates in wetting and wicking were eventually obtained towards different fabrics.From liquid wicking curves,relationship between liquid ascending height and liquid ascending time agrees well with the Washburn theory.The data comparison between the numerical measurement and the traditional test proves the reliability of the numerical results.展开更多
Plasma etching technology is used to treat Polypropylene fiber with different fineness. The result shows that the plasma etching treatment is useful to improve the wicking property of polypropylene, although too much ...Plasma etching technology is used to treat Polypropylene fiber with different fineness. The result shows that the plasma etching treatment is useful to improve the wicking property of polypropylene, although too much time of treatment may be converse to the wicking property. A surface roughness theory is applied to explain the reason why the plasma can improve the wicking property. In this experiment, fibers with different treating time under certain voltage(180 V) and pressure(0.1 mm Hg)are used as experimental sample.展开更多
An exponential model is proposed for the description of wicking, which is suitable for describing the whole process of wicking. Results are discussed and verified by the experimental data. Exponential model can be use...An exponential model is proposed for the description of wicking, which is suitable for describing the whole process of wicking. Results are discussed and verified by the experimental data. Exponential model can be used to predict the wicking process in longitudinal and planar textiles.展开更多
A stochastic approach based on a 3D 3-state Potts model combined with Monte Carlo simulation was used to study the equilibrium wicking height of liquids in vertical cylindrical capillaries. The Lifshitz-van der Waals ...A stochastic approach based on a 3D 3-state Potts model combined with Monte Carlo simulation was used to study the equilibrium wicking height of liquids in vertical cylindrical capillaries. The Lifshitz-van der Waals and Lewis acid-base theories were adopted to characterize the apolar and polar interactions in the spin system. The evolution of the spin system was driven by the difference in total energy for two successive states. To verify the model, equilibrium wicking height of water, formamide, heptane, and octane in capillaries of different radii were examined and the corresponding computer simulations were implemented. Good agreement was obtained between the simulation and experimental results. It shows the potential of the proposed approach to be applied in this area.展开更多
In this research, the wicking characteristics of fabrics were used as an essential and effective indicator to investigate the satisfaction of heat and moisture. Due to the popularization of silk fabrics recently it ha...In this research, the wicking characteristics of fabrics were used as an essential and effective indicator to investigate the satisfaction of heat and moisture. Due to the popularization of silk fabrics recently it has become an interesting topic to know about the wicking behavior of silk fabrics in water. The absorptive capability of the silk textile makes clothing comfortable even for a hotter environment. Silk fabrics are comfortable in the summer, and warm in the winter. Silk fabric can usually contain about 11 percent of its weight in moisture but the range varies from 10% to as much as 30%. In this paper, the wicking behavior of silk fabric in both warp and weft directions was investigated in terms of wicking height, wicking rate, mass increase distribution per centimeter of wicking height, the velocity of wicking height, and durability of wicking height after removal of the wicking liquid reservoir. The experimental results show that the wicking height in both the warp and weft directions had a good correlation with the time. The wicking rate was comparable in both weft and warp directions, but at the start of the wicking phase, weft direction wicking was quicker than warp direction. The mass increase in fabric per centimeter of wicking height was inversely proportional to wicking height. The mass of moisture carried in the fabric did not significantly differ in the direction of the weft and warp.展开更多
Wicking is a crucial property for comfort in human beings.The body continuously produces energy through metabolic processes and maintains comfort by dissipating this energy into the environment.Two important aspects o...Wicking is a crucial property for comfort in human beings.The body continuously produces energy through metabolic processes and maintains comfort by dissipating this energy into the environment.Two important aspects of maintaining comfort are the evaporation of sweat and the avoidance of overheating,particularly in warm and uncomfortable environments.This research investigates the wicking properties of blended knit fabrics made of different proportions of cotton,polyester,and elastane fibers.It focuses on how a higher percentage of polyester influences wicking performance.Additionally,the impact of multiple washing cycles on wicking properties was analyzed.The original state of the fabrics was assessed after several wash cycles,including after one wash,three washes,and ten washes.Ten weft-knitted blended fabrics were prepared for the study.The findings revealed differences in wicking performance between the fabrics in their original state after one wash and after ten washes.Notably,the wicking performance after ten wash cycles was nearly identical to that after three wash cycles.It helps determine whether multiple wash cycles are necessary in different scenarios.展开更多
In today's fast-paced modern life, whether for fitness training, outdoor adventures, or daily commutes, we all yearn for quick-dry apparel that can rapidly wick away moisture and keep our bodies dry and comfortabl...In today's fast-paced modern life, whether for fitness training, outdoor adventures, or daily commutes, we all yearn for quick-dry apparel that can rapidly wick away moisture and keep our bodies dry and comfortable. As a standout in functional textiles, quick-dry fabrics are becoming the top choice for more and more people, thanks to their exceptional moisture-wicking performance and rapid drying capabilities.展开更多
The effect of particle size,pH of medium,and presence of lubricant on the swelling behaviour,water uptake properties and disintegrant performance of polacrilin potassium was examined.Particle size did not affect the b...The effect of particle size,pH of medium,and presence of lubricant on the swelling behaviour,water uptake properties and disintegrant performance of polacrilin potassium was examined.Particle size did not affect the bulk swelling of disintegrant particles when measured as settling volume,but increased the water uptake and decreased the disintegration time of tablets containing this disintegrant.An increase in the pH of the medium from acidic to neutral increased the bulk swelling of the particles,whereas it decreased water uptake and disintegrant performance.Addition of lubricant had no effect on settling volume,but decreased the water uptake rate and the disintegrant performance significantly.It is concluded that wicking,i.e.capillary action,rather than swelling,is the major factor that contributes to the disintegration behaviour of polacrilin potassium.展开更多
Laser target components consist of multicomponent porous and nonporous materials that are adhesively bonded together.In order to assess the extent and quantity of adhesive wicking into porous foam, micro X-ray compute...Laser target components consist of multicomponent porous and nonporous materials that are adhesively bonded together.In order to assess the extent and quantity of adhesive wicking into porous foam, micro X-ray computed tomography(CT)and image processing software have been utilized. Two different laser target configurations have been assessed in situ and volume rendered images of the distribution and quantities of adhesive have been determined for each.展开更多
Phase change heat transfer devices like heat pipes are widely utilized in temperature control and heat transfer.However,the traditional single uniform wick makes it hard to meet the requirements of capillary pressure ...Phase change heat transfer devices like heat pipes are widely utilized in temperature control and heat transfer.However,the traditional single uniform wick makes it hard to meet the requirements of capillary pressure and permeability for high-performance heat pipes,thus limiting the improvement of heat transfer performance.In this paper,a gradient structure wick sintered by 316 L stainless steel powder is designed.The capillary performance is tested and characterized through permeability test experiments and capillary rise infrared test experiments.Moreover,the influence of different particle sizes of sintered powder on the capillary performance of the wick structure is studied.The experimental results indicate that the capillary pressure and permeability of the gradient structure wick are significantly improved compared with the traditional single structure wick.Its capillary performance parameter S(K·Pcap)is enhanced by more than 30%,providing an effective alternative for the wick of two-phase heat exchange devices.展开更多
The loop heat pipe with a flat evaporator is mainly divided into two forms:rectangular evaporator and disk-shaped evaporator.The rectangular evaporator has advantages such as low heat leakage,a thin shell,and a large ...The loop heat pipe with a flat evaporator is mainly divided into two forms:rectangular evaporator and disk-shaped evaporator.The rectangular evaporator has advantages such as low heat leakage,a thin shell,and a large contact area compared to the disk-shaped evaporator.However,most of the research on rectangular evaporators focuses onworking fluids such as water,methanol,and acetone,when theseworking fluids are in operation,the internal pressure of the evaporator is less than atmospheric pressure.Ammonia,propylene,and other working fluids can also be utilized in the loop heat pipe,these working fluids demonstrate better performance when operating within other temperature intervals,for example,the operating temperature range of ammonia is−20℃to 50℃,however,in an atmospheric pressure environment,it is very difficult for the shell of the rectangular evaporator to withstand the saturated vapor pressure of the working fluid.This paper designs a rectangular flat plate loop heat pipe that can use ammonia as the working fluid.The internal reinforcing structure is used to improve the pressure strength of the shell.The secondary wick connects the compensation chamber and the capillary wick hydraulically.The experiment indicates that this kind of rectangular evaporator is unaffected by the position,and the secondary wick can effectively supply liquid under different angles.The thermal resistance of the evaporator wall was analyzed,and it was found that the thermal resistance of the evaporator wall was the main component of the thermal resistance of the system.The heat transfer capacities of 460 W@0.5 m and 200W@10 m were tested.The test results indicate that by setting a reinforcing structure inside the flat plate evaporator,the evaporator can withstand internal pressure.Combined with the design of the secondary wick,the flat plate evaporator can use working fluids with different pressures,expanding the range of available working fluids.展开更多
Centered or striped wick structures have been used to develop ultrathin heat pipes.Differing from traditional heat pipes,the centered or striped wick structures leave noncontact container surfaces with the wick struct...Centered or striped wick structures have been used to develop ultrathin heat pipes.Differing from traditional heat pipes,the centered or striped wick structures leave noncontact container surfaces with the wick structure.In this study,experiments andnumerical analyseswere conductedtoinvestigate the influenceof thesenoncontact surfaces.In the experiments,a strip-shaped wick structure was placed vertically,the top was sandwiched between wider rods and the bottom was immersed in a working fluid.The rod width was greater than the wick width;thus,noncontact surfaces were left between the rod and the wick structure.The heat was applied from the rod to the wick structure,and the evaporation heat transfer characteristics of the working fluid from the wick structure were evaluated.Water was used as the working fluid.The experiments were conducted by varying the rod and wick widths.The experimental results were obtained when the wick structures were placed separately.In the numerical analyses,the temperature and heat flux distributions in the rod were obtained.From the experimental and numerical results,it was confirmed that the noncontact surfaces caused the heat flux in the rod near both surfaces of the wick structure to concentrate,which increased the evaporation thermal resistance of the wick structure.A reduction in the noncontact surface area by increasing the wick width was found to be effective in decreasing the evaporation thermal resistance and increasing themaximumheat transfer rate of the wick structure.The separation of the wick structure increased the evaporation surface area.However,its effectiveness was limited when the heat transfer rate was small.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
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.
基金This work is financially supported by the Chinese Education Ministry and Donghua University of China (No. 2B01).
文摘The column wicking technique was applied to estimate the surface free energy of cellulose, the importance of which is to obtain a real effective capillary radius, Reff, initially from the plot of Washburn penetration distance versus time. Since the cellulose sample could not be packed with good reproducibility, therefore, Reff can not be obtained readily from the slope of the plot. A method was developed in this paper by uniting all apparent packing heights with a unique value to deduce a real effective capillary radius. Based on the defined critical packing height related to the critical packing density, the surface free energy and acid-base properties of cellulose Sigma C8002 were estimated.
基金Projects(41872240,41672280)supported by the National Natural Science Foundation of ChinaProject(2016-1-16-2)supported by Science and Technology Project of Jilin Province Transportation,ChinaProject(SJCX18-0052)supported by the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China。
文摘Wicking geotextile(WG)is considered as a possible countermeasure to reduce water content in unsaturated soil.In this research,rainfall tests were carried out to verify the drainage performance of WG.And capillary rise tests were conducted to study the effect of WG on the prevention of capillary rise.Test results indicated that WG with good drainage performance could drain gravitational and capillary water out of kaolinite soil.For kaolinite soil column with water content of 12%and compaction degree of 90%,the whole process of capillary rise in soil column with a layer of WG was a typical two-stage mode,and the maximum capillary height was about 380 mm,which provided that the WG could work as a barrier to prevent capillary rise effectively.In addition,the total vertical influential regions of WG in kaolinite soil above and below the WG layer were 400 and 100 mm,respectively.
基金the Research Funds for the Central Universities,China(No.1302-1)The Project Sponsored SRF for ROCS,SEM,China
文摘After a brief review of existing methods for fabric wetting and wicking measurement,a new numerical approach based on dynamic image acquisition and analysis was proposed to study the liquid wetting and wicking properties of woven fabrics.A measuring system was first developed to record on-site the images of liquid ascending in fabrics for a certain period of time.The hardware and software platforms and the experimental methods were described,and the image processing and analysis as well as other related algorithms were discussed in detail.The liquid front curves and rising rates in wetting and wicking were eventually obtained towards different fabrics.From liquid wicking curves,relationship between liquid ascending height and liquid ascending time agrees well with the Washburn theory.The data comparison between the numerical measurement and the traditional test proves the reliability of the numerical results.
文摘Plasma etching technology is used to treat Polypropylene fiber with different fineness. The result shows that the plasma etching treatment is useful to improve the wicking property of polypropylene, although too much time of treatment may be converse to the wicking property. A surface roughness theory is applied to explain the reason why the plasma can improve the wicking property. In this experiment, fibers with different treating time under certain voltage(180 V) and pressure(0.1 mm Hg)are used as experimental sample.
文摘An exponential model is proposed for the description of wicking, which is suitable for describing the whole process of wicking. Results are discussed and verified by the experimental data. Exponential model can be used to predict the wicking process in longitudinal and planar textiles.
基金Science Foundation of Zhejiang Sci-Tech University(ZSTU),China(No.0901804-Y)
文摘A stochastic approach based on a 3D 3-state Potts model combined with Monte Carlo simulation was used to study the equilibrium wicking height of liquids in vertical cylindrical capillaries. The Lifshitz-van der Waals and Lewis acid-base theories were adopted to characterize the apolar and polar interactions in the spin system. The evolution of the spin system was driven by the difference in total energy for two successive states. To verify the model, equilibrium wicking height of water, formamide, heptane, and octane in capillaries of different radii were examined and the corresponding computer simulations were implemented. Good agreement was obtained between the simulation and experimental results. It shows the potential of the proposed approach to be applied in this area.
文摘In this research, the wicking characteristics of fabrics were used as an essential and effective indicator to investigate the satisfaction of heat and moisture. Due to the popularization of silk fabrics recently it has become an interesting topic to know about the wicking behavior of silk fabrics in water. The absorptive capability of the silk textile makes clothing comfortable even for a hotter environment. Silk fabrics are comfortable in the summer, and warm in the winter. Silk fabric can usually contain about 11 percent of its weight in moisture but the range varies from 10% to as much as 30%. In this paper, the wicking behavior of silk fabric in both warp and weft directions was investigated in terms of wicking height, wicking rate, mass increase distribution per centimeter of wicking height, the velocity of wicking height, and durability of wicking height after removal of the wicking liquid reservoir. The experimental results show that the wicking height in both the warp and weft directions had a good correlation with the time. The wicking rate was comparable in both weft and warp directions, but at the start of the wicking phase, weft direction wicking was quicker than warp direction. The mass increase in fabric per centimeter of wicking height was inversely proportional to wicking height. The mass of moisture carried in the fabric did not significantly differ in the direction of the weft and warp.
文摘Wicking is a crucial property for comfort in human beings.The body continuously produces energy through metabolic processes and maintains comfort by dissipating this energy into the environment.Two important aspects of maintaining comfort are the evaporation of sweat and the avoidance of overheating,particularly in warm and uncomfortable environments.This research investigates the wicking properties of blended knit fabrics made of different proportions of cotton,polyester,and elastane fibers.It focuses on how a higher percentage of polyester influences wicking performance.Additionally,the impact of multiple washing cycles on wicking properties was analyzed.The original state of the fabrics was assessed after several wash cycles,including after one wash,three washes,and ten washes.Ten weft-knitted blended fabrics were prepared for the study.The findings revealed differences in wicking performance between the fabrics in their original state after one wash and after ten washes.Notably,the wicking performance after ten wash cycles was nearly identical to that after three wash cycles.It helps determine whether multiple wash cycles are necessary in different scenarios.
文摘In today's fast-paced modern life, whether for fitness training, outdoor adventures, or daily commutes, we all yearn for quick-dry apparel that can rapidly wick away moisture and keep our bodies dry and comfortable. As a standout in functional textiles, quick-dry fabrics are becoming the top choice for more and more people, thanks to their exceptional moisture-wicking performance and rapid drying capabilities.
文摘The effect of particle size,pH of medium,and presence of lubricant on the swelling behaviour,water uptake properties and disintegrant performance of polacrilin potassium was examined.Particle size did not affect the bulk swelling of disintegrant particles when measured as settling volume,but increased the water uptake and decreased the disintegration time of tablets containing this disintegrant.An increase in the pH of the medium from acidic to neutral increased the bulk swelling of the particles,whereas it decreased water uptake and disintegrant performance.Addition of lubricant had no effect on settling volume,but decreased the water uptake rate and the disintegrant performance significantly.It is concluded that wicking,i.e.capillary action,rather than swelling,is the major factor that contributes to the disintegration behaviour of polacrilin potassium.
文摘Laser target components consist of multicomponent porous and nonporous materials that are adhesively bonded together.In order to assess the extent and quantity of adhesive wicking into porous foam, micro X-ray computed tomography(CT)and image processing software have been utilized. Two different laser target configurations have been assessed in situ and volume rendered images of the distribution and quantities of adhesive have been determined for each.
文摘Phase change heat transfer devices like heat pipes are widely utilized in temperature control and heat transfer.However,the traditional single uniform wick makes it hard to meet the requirements of capillary pressure and permeability for high-performance heat pipes,thus limiting the improvement of heat transfer performance.In this paper,a gradient structure wick sintered by 316 L stainless steel powder is designed.The capillary performance is tested and characterized through permeability test experiments and capillary rise infrared test experiments.Moreover,the influence of different particle sizes of sintered powder on the capillary performance of the wick structure is studied.The experimental results indicate that the capillary pressure and permeability of the gradient structure wick are significantly improved compared with the traditional single structure wick.Its capillary performance parameter S(K·Pcap)is enhanced by more than 30%,providing an effective alternative for the wick of two-phase heat exchange devices.
基金Science Foundation for Distinguished Young Scholars 2020-JCJQ-ZQ-042.
文摘The loop heat pipe with a flat evaporator is mainly divided into two forms:rectangular evaporator and disk-shaped evaporator.The rectangular evaporator has advantages such as low heat leakage,a thin shell,and a large contact area compared to the disk-shaped evaporator.However,most of the research on rectangular evaporators focuses onworking fluids such as water,methanol,and acetone,when theseworking fluids are in operation,the internal pressure of the evaporator is less than atmospheric pressure.Ammonia,propylene,and other working fluids can also be utilized in the loop heat pipe,these working fluids demonstrate better performance when operating within other temperature intervals,for example,the operating temperature range of ammonia is−20℃to 50℃,however,in an atmospheric pressure environment,it is very difficult for the shell of the rectangular evaporator to withstand the saturated vapor pressure of the working fluid.This paper designs a rectangular flat plate loop heat pipe that can use ammonia as the working fluid.The internal reinforcing structure is used to improve the pressure strength of the shell.The secondary wick connects the compensation chamber and the capillary wick hydraulically.The experiment indicates that this kind of rectangular evaporator is unaffected by the position,and the secondary wick can effectively supply liquid under different angles.The thermal resistance of the evaporator wall was analyzed,and it was found that the thermal resistance of the evaporator wall was the main component of the thermal resistance of the system.The heat transfer capacities of 460 W@0.5 m and 200W@10 m were tested.The test results indicate that by setting a reinforcing structure inside the flat plate evaporator,the evaporator can withstand internal pressure.Combined with the design of the secondary wick,the flat plate evaporator can use working fluids with different pressures,expanding the range of available working fluids.
文摘Centered or striped wick structures have been used to develop ultrathin heat pipes.Differing from traditional heat pipes,the centered or striped wick structures leave noncontact container surfaces with the wick structure.In this study,experiments andnumerical analyseswere conductedtoinvestigate the influenceof thesenoncontact surfaces.In the experiments,a strip-shaped wick structure was placed vertically,the top was sandwiched between wider rods and the bottom was immersed in a working fluid.The rod width was greater than the wick width;thus,noncontact surfaces were left between the rod and the wick structure.The heat was applied from the rod to the wick structure,and the evaporation heat transfer characteristics of the working fluid from the wick structure were evaluated.Water was used as the working fluid.The experiments were conducted by varying the rod and wick widths.The experimental results were obtained when the wick structures were placed separately.In the numerical analyses,the temperature and heat flux distributions in the rod were obtained.From the experimental and numerical results,it was confirmed that the noncontact surfaces caused the heat flux in the rod near both surfaces of the wick structure to concentrate,which increased the evaporation thermal resistance of the wick structure.A reduction in the noncontact surface area by increasing the wick width was found to be effective in decreasing the evaporation thermal resistance and increasing themaximumheat transfer rate of the wick structure.The separation of the wick structure increased the evaporation surface area.However,its effectiveness was limited when the heat transfer rate was small.
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.
