Nucleation and Undercooling of Acoustically Levitated Water Drops
Water drops are undercooled to temperatures more than 16 K below its freezing point with a piezoelectric-type acoustic levitator,because of the efficient elimination of heterogeneous nuclei in containerless state.The experimental results show that the undercooling level increases linearly with the rise of cooling rate in the range of 3～14 K/min and can be enhanced by either diminishing the drop surface area or reducing the sound pressure.The effects of surface area and sound pressure on undercoolability are explained in the light of the surface nucleation model.The strong influence of cooling rate on undercoolings indicates that the nucleation rate of ice has relatively weak dependence on undercooling as compared with the case of homogeneous nucleation.Further analyses based on the classic nucleation theory show that the small nucleation prefactor in surface nucleation accounts for this weak dependence.These results suggest that levitating small water drops with low sound pressure and high cooling rate is helpful to obtain large undercoolings.
water acoustic levitation undercooling nucleation rate
C.L.Shen W.J.Xie B.Wei
Department of Applied Physics Northwestern Polytechnical University,Xian 710072,P.R.China
国际会议
南京
英文
107-113
2007-09-09（万方平台首次上网日期，不代表论文的发表时间）