In order to study reasonable sintering technological parameters and appropriate copper powder size range of micro heat pipe (MHP) with the sintered wick, the forming principle of copper powders in wicks and MHP's ...In order to study reasonable sintering technological parameters and appropriate copper powder size range of micro heat pipe (MHP) with the sintered wick, the forming principle of copper powders in wicks and MHP's heat transfer capabilities were first analyzed, then copper powders with different cell sizes and dispersions were sintered in RXL-12-11 resistance furnace under the protection of the hydrogen at different sintering temperatures for different durations of sintering time, and finally the sintered wicks' scanning electron microscope (SEM) images and their heat transfer capabilities were analyzed. The results indicate that the wick sintered with copper powders of larger cell size or smaller size range has better sintering properties and larger heat transfer capabilities; and that the increase of either sintering temperatures or sintering time also helps to improve the wick's sintering properties and heat transfer capabilities, and the former affects more obviously than the latter. Considering both its manufacturing cost and performance requirements, it is recommended that copper powders with the size range of 140-170 μm are sintered at 900-950℃ for 30-60 min in practical manufacturing. In addition, two approaches to improve wick's porosity are also proposed through theoretical analysis, which suggests that the larger the wick's porosity, the better the heat transfer capabilities of the MHP.展开更多
In order to improve the capillary force of grooved wick, a novel skew-grooved wick structure was proposed for micro heat pipes. Risen meniscus experiments were carried out to research the capillary force of the skew-g...In order to improve the capillary force of grooved wick, a novel skew-grooved wick structure was proposed for micro heat pipes. Risen meniscus experiments were carried out to research the capillary force of the skew-grooved and rectangle-grooved wick and a comparison of capillarity between the two wick structures was explored. A theoretical capillary force model of skew-grooved wick structure was also developed to calculate its effective capillary radius by comparing with the rectangle-grooved wick. From the experimental results, the maximum capillary force of the skewed-grooved wick is 8.62% larger than that of the rectangle-grooved wick. From the theoretical analysis, because the skewed-grooved wick has a smaller effective capillary radius, its maximum capillary force is 8.64% larger than that of the rectangle-grooved wick. The results indicate that the skew-grooved wick provides larger capillary force than the rectangle-grooved wick.展开更多
The temperature control in electronic packaging is the key in numerous applications,to avoid overheating and hardware failure.Due to high capability of heat transfer,good temperature uniformity,and no power consumptio...The temperature control in electronic packaging is the key in numerous applications,to avoid overheating and hardware failure.Due to high capability of heat transfer,good temperature uniformity,and no power consumption,heat pipes can be widely used for heat dissipation of electronic components.This paper reports an experimental thermal analysis of different capillary structures for heat pipes.The wicks considered are metal screens,axial microgrooves,and sintered metal powder.The heat pipes are made of copper,a 200 mm length tube and a 9.45 mm external diameter.Working fluid used was distilled water.The devices are investigated in three positions:0,90,and 270°to the horizontal under powers of 5 up to 45 W.The results show that in horizontal(0°)and with the evaporator under the condenser(270°),the heat pipes showed similar results.Nevertheless,in the reverse condition(the position against the gravity with the evaporator above the condenser,90°),the heat pipe with sintered wick presented the best thermal performance,as it has the lowest thermal resistance and supported a higher power.Besides that,the sintered powder capillary structure demonstrates the most homogeneous thermal behavior for every position,making the most suitable for applications susceptible to diverse inclinations.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 diffe...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℃ for 30min,using direct loose sintering technique,with 90% nickel and 10% copper.The wicks could reach the porosity of 70.07% and the permeability of 10-13m2 order,with mean pore radius of 0.54μm.展开更多
基金Key Project(50436010, U0834002) supported by the National Natural Science Foundation of ChinaProjects(50675070, 50705031) supported by the National Natural Science Foundation of China+1 种基金Project(8151064101000058) supported by the Natural Science Foundation of Guangdong Province,ChinaProject(E200909) supported by the Natural Science Foundation of Heilongjiang Province, China
文摘In order to study reasonable sintering technological parameters and appropriate copper powder size range of micro heat pipe (MHP) with the sintered wick, the forming principle of copper powders in wicks and MHP's heat transfer capabilities were first analyzed, then copper powders with different cell sizes and dispersions were sintered in RXL-12-11 resistance furnace under the protection of the hydrogen at different sintering temperatures for different durations of sintering time, and finally the sintered wicks' scanning electron microscope (SEM) images and their heat transfer capabilities were analyzed. The results indicate that the wick sintered with copper powders of larger cell size or smaller size range has better sintering properties and larger heat transfer capabilities; and that the increase of either sintering temperatures or sintering time also helps to improve the wick's sintering properties and heat transfer capabilities, and the former affects more obviously than the latter. Considering both its manufacturing cost and performance requirements, it is recommended that copper powders with the size range of 140-170 μm are sintered at 900-950℃ for 30-60 min in practical manufacturing. In addition, two approaches to improve wick's porosity are also proposed through theoretical analysis, which suggests that the larger the wick's porosity, the better the heat transfer capabilities of the MHP.
基金Project(U0834002) supported by the Key Program of NSFC-Guangdong Joint Funds of ChinaProject(51005079) supported by the National Natural Science Foundation of China+1 种基金Project(2009ZM0121) supported by the Fundamental Research Funds for the Central Universities in ChinaProject(LYM09024) supported by the Training Program for Excellent Young Teachers with Innovation of Guangdong University, China
文摘In order to improve the capillary force of grooved wick, a novel skew-grooved wick structure was proposed for micro heat pipes. Risen meniscus experiments were carried out to research the capillary force of the skew-grooved and rectangle-grooved wick and a comparison of capillarity between the two wick structures was explored. A theoretical capillary force model of skew-grooved wick structure was also developed to calculate its effective capillary radius by comparing with the rectangle-grooved wick. From the experimental results, the maximum capillary force of the skewed-grooved wick is 8.62% larger than that of the rectangle-grooved wick. From the theoretical analysis, because the skewed-grooved wick has a smaller effective capillary radius, its maximum capillary force is 8.64% larger than that of the rectangle-grooved wick. The results indicate that the skew-grooved wick provides larger capillary force than the rectangle-grooved wick.
文摘The temperature control in electronic packaging is the key in numerous applications,to avoid overheating and hardware failure.Due to high capability of heat transfer,good temperature uniformity,and no power consumption,heat pipes can be widely used for heat dissipation of electronic components.This paper reports an experimental thermal analysis of different capillary structures for heat pipes.The wicks considered are metal screens,axial microgrooves,and sintered metal powder.The heat pipes are made of copper,a 200 mm length tube and a 9.45 mm external diameter.Working fluid used was distilled water.The devices are investigated in three positions:0,90,and 270°to the horizontal under powers of 5 up to 45 W.The results show that in horizontal(0°)and with the evaporator under the condenser(270°),the heat pipes showed similar results.Nevertheless,in the reverse condition(the position against the gravity with the evaporator above the condenser,90°),the heat pipe with sintered wick presented the best thermal performance,as it has the lowest thermal resistance and supported a higher power.Besides that,the sintered powder capillary structure demonstrates the most homogeneous thermal behavior for every position,making the most suitable for applications susceptible to diverse inclinations.
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℃ for 30min,using direct loose sintering technique,with 90% nickel and 10% copper.The wicks could reach the porosity of 70.07% and the permeability of 10-13m2 order,with mean pore radius of 0.54μm.
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