This paper put forward a new-type vortex generator enhancing heat exchange of solar air-drier and air-heater on the gas side,and investigated the mechanism of heat transfer enhancement and drag reduction by the influe...This paper put forward a new-type vortex generator enhancing heat exchange of solar air-drier and air-heater on the gas side,and investigated the mechanism of heat transfer enhancement and drag reduction by the influence of vortex generators on the coherent structure of turbulent boundary layer.The flow and heat transfer characteristics of rectangle channel with bevel-cut half-elliptical column vortex generators were obtained using large eddy simulation(LES)and the hydromechanics software FLUENT6.3.The instantaneous properties of velocity,temperature and pressure in channel were gained.The coherent structure of turbulent boundary layer flow was showed,and the characteristic of vortex induced by inclined-cut semi-ellipse vortex generator and its influence on turbulent coherent structure were analyzed.And the effect mechanism of turbulent coherent structure on flow field,pressure field and temperature field was discussed.Based on the results,the heat transfer coefficient and drag reduction of the new vortex generator with different pitch angles were compared.Sometimes,the coherent effects of the increased wall heat transfer and the decreased skin friction do not satisfy the Reynolds analogy.The turbulent coherent structure can be controlled through the geometry of the vortex generator,so the heat transfer and drag reduction can also be controlled.Then we can seek suitable form of vortex generator and structure parameters,in order to achieve the enhanced heat transfer and flow of drag reduction in the solar air-heater and solar air-drier.展开更多
The electronic structure and optical properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were studied using density-functional theory(DFT) within generalized gradient approximation(GGA).Th...The electronic structure and optical properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were studied using density-functional theory(DFT) within generalized gradient approximation(GGA).The band structure along the higher symmetry axes in the Brillouin zone,the density of states(DOS) and the partial density of states(PDOS) were presented.The calculated energy band structures show that both YZnAsO and LaZnAsO are indirect gap semiconductors with band gap of 1.173 1 eV and 1.166 5 eV,respectively.The DOS and PDOS show the hybridization of Y-O/La-O atom orbits and Zn-As atom orbits.The dielectric function,reflectivity,absorption coefficient,refractive index,electron energy-loss function and optical conductivity were presented in an energy range from 0 to 25 eV for discussing the optical properties of YZnAsO and LaZnAsO.展开更多
基金Supported by National Natural Science Foundation of China(50676027)
文摘This paper put forward a new-type vortex generator enhancing heat exchange of solar air-drier and air-heater on the gas side,and investigated the mechanism of heat transfer enhancement and drag reduction by the influence of vortex generators on the coherent structure of turbulent boundary layer.The flow and heat transfer characteristics of rectangle channel with bevel-cut half-elliptical column vortex generators were obtained using large eddy simulation(LES)and the hydromechanics software FLUENT6.3.The instantaneous properties of velocity,temperature and pressure in channel were gained.The coherent structure of turbulent boundary layer flow was showed,and the characteristic of vortex induced by inclined-cut semi-ellipse vortex generator and its influence on turbulent coherent structure were analyzed.And the effect mechanism of turbulent coherent structure on flow field,pressure field and temperature field was discussed.Based on the results,the heat transfer coefficient and drag reduction of the new vortex generator with different pitch angles were compared.Sometimes,the coherent effects of the increased wall heat transfer and the decreased skin friction do not satisfy the Reynolds analogy.The turbulent coherent structure can be controlled through the geometry of the vortex generator,so the heat transfer and drag reduction can also be controlled.Then we can seek suitable form of vortex generator and structure parameters,in order to achieve the enhanced heat transfer and flow of drag reduction in the solar air-heater and solar air-drier.
基金Project(50474051) supported by the National Natural Science Foundation of China
文摘The electronic structure and optical properties of the tetragonal phase quaternary arsenide oxides YZnAsO and LaZnAsO were studied using density-functional theory(DFT) within generalized gradient approximation(GGA).The band structure along the higher symmetry axes in the Brillouin zone,the density of states(DOS) and the partial density of states(PDOS) were presented.The calculated energy band structures show that both YZnAsO and LaZnAsO are indirect gap semiconductors with band gap of 1.173 1 eV and 1.166 5 eV,respectively.The DOS and PDOS show the hybridization of Y-O/La-O atom orbits and Zn-As atom orbits.The dielectric function,reflectivity,absorption coefficient,refractive index,electron energy-loss function and optical conductivity were presented in an energy range from 0 to 25 eV for discussing the optical properties of YZnAsO and LaZnAsO.
