Different sized single droplets of Cu-6%Sn alloy were prepared by drop on demand(DOD)technique.The secondarydendrite arm spacing was measured and correlated with the droplet cooling rate by a semi-empirical formula.Th...Different sized single droplets of Cu-6%Sn alloy were prepared by drop on demand(DOD)technique.The secondarydendrite arm spacing was measured and correlated with the droplet cooling rate by a semi-empirical formula.The microstructure ofdroplets was observed by optical microscopy(OM)and electro backscatter diffraction(EBSD).The dendrite feature of singledroplets depends on solidification rate,cooling medium and flight distance.When droplets collide with each other at temperaturesbetween solidus and liquidus,the dendrites and grains are refined obviously possibly because the collision enhances the heat transfer.The cooling rate of colliding droplets is estimated to be more than4×104K/s based on a Newton’s cooling model.The dendritesgrow along the colliding direction because of the temperature gradient induced by the internal flow inside the droplets.展开更多
Laminar natural convection heat transfer inside air-filled, rectangular enclosures partially heated from below and cooled at one side is studied numerically. A computational code based on the SIMPLE-C algorithm is use...Laminar natural convection heat transfer inside air-filled, rectangular enclosures partially heated from below and cooled at one side is studied numerically. A computational code based on the SIMPLE-C algorithm is used for the solution of the system of the mass, momentum, and energy transfer governing equations. Simulations are performed for a complete range of heater size, for Rayleigh numbers based on the height of the cavity ranging from 10~3to 10~6, and for height-to-width aspect ratios of the cavity spanning from 0.25 to 4. It is found that the heat transfer rate increases with increasing the heater size and the Rayleigh number, while it decreases with increasing the aspect ratio of the cavity. Dimensionless heat transfer correlations are also proposed.展开更多
基金Project(51301143)supported by the National Natural Science Foundation of ChinaProject(2014M560727)supported by the National Postdoctoral Foundation of China+1 种基金Project(2015GZ0228)supported by the Sichuan Province Science-Technology Support Plan,ChinaProject(2682014CX001)supported by the Science and Technology Innovation Project of SWJTU University,China
文摘Different sized single droplets of Cu-6%Sn alloy were prepared by drop on demand(DOD)technique.The secondarydendrite arm spacing was measured and correlated with the droplet cooling rate by a semi-empirical formula.The microstructure ofdroplets was observed by optical microscopy(OM)and electro backscatter diffraction(EBSD).The dendrite feature of singledroplets depends on solidification rate,cooling medium and flight distance.When droplets collide with each other at temperaturesbetween solidus and liquidus,the dendrites and grains are refined obviously possibly because the collision enhances the heat transfer.The cooling rate of colliding droplets is estimated to be more than4×104K/s based on a Newton’s cooling model.The dendritesgrow along the colliding direction because of the temperature gradient induced by the internal flow inside the droplets.
文摘Laminar natural convection heat transfer inside air-filled, rectangular enclosures partially heated from below and cooled at one side is studied numerically. A computational code based on the SIMPLE-C algorithm is used for the solution of the system of the mass, momentum, and energy transfer governing equations. Simulations are performed for a complete range of heater size, for Rayleigh numbers based on the height of the cavity ranging from 10~3to 10~6, and for height-to-width aspect ratios of the cavity spanning from 0.25 to 4. It is found that the heat transfer rate increases with increasing the heater size and the Rayleigh number, while it decreases with increasing the aspect ratio of the cavity. Dimensionless heat transfer correlations are also proposed.
