To study the heat and mass transfer characteristics of alkali metals in a combined porous wick in high-temperature heat pipes,a three-dimensional(3-D)numerical model is constructed by using the finite volume method,Da...To study the heat and mass transfer characteristics of alkali metals in a combined porous wick in high-temperature heat pipes,a three-dimensional(3-D)numerical model is constructed by using the finite volume method,Darcy’s theory,and the theory of local thermal equilibrium.The research finds that the pressure drop of fluids flowing through a combined porous wick exhibits an increasing trend with increasing flow velocity at the inlet and with decreasing permeability of the porous media;a combined porous wick of lower porosity and permeability and larger fluid velocity at the inlet is found to have a less uniformly distributed fluid velocity;the different temperatures of the fluid at the inlet mainly influence the inlet section of the computational model,while having negligible effect thereon in the axial direction(this embodies the thermal homogeneity of such heat pipes).The result reveals that the temperature change in fluids at the inlet does not significantly affect the overall temperature distribution in a combined wick.展开更多
In order to study the effect of Al_(2)O_(3) nanoparticles in the cavitation-based strengthening process of magnesium alloys,the impact of a micro-jet generated by bubble collapse has been considered.The strengthening ...In order to study the effect of Al_(2)O_(3) nanoparticles in the cavitation-based strengthening process of magnesium alloys,the impact of a micro-jet generated by bubble collapse has been considered.The strengthening mechanism is based on the transfer of the energy of cavitation due to bubble collapse to Al_(2)O_(3) particles,which then undergo collision with the surface of the sample.The hardness,surface morphology,element content and chemical state of the strengthened samples have been analyzed by microhardness tests,SEM(scanning electron microscopy)and XPS(X-ray photoelectron spectroscopy)techniques.The results show that:after 5 min of strengthening,nanoparticles can be found on the surface of the sample through SEM.Combined with XPS tests,the content of Al_(2)O_(3) in the sample can be significantly increased,indicating that Al_(2)O_(3) particles penetrate into the surface and increase its hardness by 29.1 HV.展开更多
基金supported by the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20180177)the Science and Technology Foundation of Xuzhou,China(Grant No.KH17007)the Natural Science Foundation for Colleges and Universities of Jiangsu Province,China(Grant No.17KJB460015,No.18KJB460028).
文摘To study the heat and mass transfer characteristics of alkali metals in a combined porous wick in high-temperature heat pipes,a three-dimensional(3-D)numerical model is constructed by using the finite volume method,Darcy’s theory,and the theory of local thermal equilibrium.The research finds that the pressure drop of fluids flowing through a combined porous wick exhibits an increasing trend with increasing flow velocity at the inlet and with decreasing permeability of the porous media;a combined porous wick of lower porosity and permeability and larger fluid velocity at the inlet is found to have a less uniformly distributed fluid velocity;the different temperatures of the fluid at the inlet mainly influence the inlet section of the computational model,while having negligible effect thereon in the axial direction(this embodies the thermal homogeneity of such heat pipes).The result reveals that the temperature change in fluids at the inlet does not significantly affect the overall temperature distribution in a combined wick.
基金the University Natural Science Research Programme of Jiangsu Province(Grant No.18KJB460028)Project of Xuzhou University of Technology(Grant No.XKY2019215)+1 种基金the Natural Science Foundation of Jiangsu Province(Grant No.BK20180177)the Xuzhou Science&Technology Project(Grant No.KC18014).
文摘In order to study the effect of Al_(2)O_(3) nanoparticles in the cavitation-based strengthening process of magnesium alloys,the impact of a micro-jet generated by bubble collapse has been considered.The strengthening mechanism is based on the transfer of the energy of cavitation due to bubble collapse to Al_(2)O_(3) particles,which then undergo collision with the surface of the sample.The hardness,surface morphology,element content and chemical state of the strengthened samples have been analyzed by microhardness tests,SEM(scanning electron microscopy)and XPS(X-ray photoelectron spectroscopy)techniques.The results show that:after 5 min of strengthening,nanoparticles can be found on the surface of the sample through SEM.Combined with XPS tests,the content of Al_(2)O_(3) in the sample can be significantly increased,indicating that Al_(2)O_(3) particles penetrate into the surface and increase its hardness by 29.1 HV.
