接触角和质量分数对液滴冻结过程的影响

本文通过FLUENT软件的凝固/熔化模型，模拟了接触角及质量分数对纯水和氯化钠溶液在冷表面冻结过程的影响，选择铜片为亲水表面，纳米膜表面为疏水表面，对液滴在不同表面特性条件下的冻结过程进行实验研究。结果表明：液滴在冷表面的冻结特性与接触角、质量分数有关。当溶液质量分数一定时，接触角越小，液滴冻结速度越快，完全冻结时间越短；在冻结过程的初始时刻，接触角越小，液滴底部温度越低；当冻结时刻相同、液滴高度一致时，液滴表面的温度和液相分数均比液滴内部低；接触角相同时，溶液质量分数与液滴的开始冻结温度成反比，与完全冻结时间成正比。对比实验结果与模拟可知，不同质量分数的氯化钠液滴在接触角为60°和100°时，冻结时间的变化趋势一致，但实验值大于模拟值。

Effect of Contact Angle and Mass Fraction on Droplet Freezing Process

The solidification/melting model of FLUENT software was used to numerically study the influence of contact angle and mass fraction on the freezing process of pure water and sodium chloride solution on the cold surface. Meanwhile, copper was chosen as the hydrophilic surface and nanometer film as the hydrophobic surface, and the freezing process of droplets under different surface characteristics was experimentally studied. The results show that the freezing characteristics of the droplet on the surface of the plate are related to the surface contact angle and mass fraction. When the solution mass fraction is fixed, a smaller contact angle results in a faster droplet freezing rate and a shorter complete freezing time. At the beginning of the freezing process, the smaller the contact angle, the lower the bottom temperature of the droplet. When the freezing time and the droplet height were the same, the temperature and liquid fraction on the surface of the droplet were lower than those inside the droplet. At the same contact angle, the solution mass fraction is inversely proportional to the initial freezing temperature of the droplet and directly proportional to the complete freezing time. The comparison between the experimental results and the simulation results shows that the freezing time of different mass fractions of sodium chloride droplets exhibits the same trend when the contact angle is 60° and 100°, but the experimental value is greater than the simulated value.