Abstract:

Ice slurries of nanosilica fluid at different concentrations were prepared by dispersing silica nanoparticles in aqueous solutions of either ethylene glycol or sodium chloride. Images of ice crystal particles in ice slurries were obtained by a microscopic observation system. The resulting size distributions of ice crystals were compared to normal, log-normal, Gamma, and Weibull distributions so as to investigate nanosilica effect on average diameter and size distribution of ice particles and to study dimensional change of ice particles during storage of ice slurries. The experimental results indicated that ice particle sizes were fitted well with Gamma distribution before and after addition of nanosilica. Nanosilica played an important role in grain refinement such that sizes of ice particles decreased linearly with increasing concentrations of nanosilica. When ethylene glycol aqueous solution was base fluid, nanosilica addition effectively inhibited growth of ice particles during slurry storage. When sodium chloride aqueous solution was base fluid, concentration of nanosilica had to be increased from 0.25% to 0.75% for similar inhibition effect. Therefore, nanosilica could be used to reduce particle size and to control growth of ice crystals, which has an important application for flow and heat transfer improvement of ice slurry.

Key words: ice slurry, particle size distribution, particle size evolution, nanoparticles, silica

摘要：

分别以乙二醇水溶液和氯化钠水溶液为基液配制不同浓度的二氧化硅纳米流体并以此制备冰浆，通过显微装置获得冰晶图像，将实验得到的粒径分布与正态分布、对数正态分布、Gamma分布和Weibull分布进行对比，探讨纳米二氧化硅对冰晶平均粒径与分布特性的影响，同时观测储存过程中冰晶粒径演化规律。结果表明：加入纳米二氧化硅前后冰晶粒径分布均可用Gamma分布描述；纳米二氧化硅可起到细化晶粒的作用，而且添加浓度越高冰晶颗粒越小；当基液为乙二醇水溶液时，加入纳米二氧化硅可较好地抑制储存过程中的冰晶粒径增长，但基液为氯化钠水溶液时，纳米二氧化硅浓度需达到0.75%，才可抑制冰晶增大。研究结果证明，一定浓度的纳米二氧化硅流体可作为制冰溶液，起到减小冰晶粒径并控制冰晶生长的作用，这对冰浆流动和传热性能的改善具有重要的应用价值。

关键词: 冰浆, 粒度分布, 粒径演化, 纳米粒子, 二氧化硅