Modeling the crystallization of a water droplet inside the vacuum chamber is the first step to model the vacuum spray ice-slurry production system. This paper models the droplet which is transformed from a high temperature to zero temperature, then super cooling liquid, and then to the liquid-solid phase, and finally to the solid phase. Heat and mass transfer occurred rapidly during this process. The modeling results show that the evaporation or the sublimation governs the heat transfer process. Both diffusion model and convection model agrees with the experimental data relatively well, because the heat transferred with convection or conduction is at a much less order of magnitude compared with the latent heat transferred with the phase change. The temperature variation of the droplet during the whole crystallization process is given, which shows that the liquid-solid phase takes up most of the time and is the most important process. The motion of the droplet during the crystallization process is also investigated, with gravity, buoyancy and viscous drag considered. The falling distance obtained from our model is better than what obtained by assuming free falling with only gravity. Results obtained from this paper will provide valuable reference for a better design of the vacuum chamber.%模拟真空室内水滴结晶过程是模拟真空雾化法制备冰浆系统的第一步。模拟了液滴在真空室内从较高的温度降温到零度，之后到一定的过冷度，然后发生相变为液一固两相，到最后为全部固相的整个过程。在该过程中热质传递迅速发生，模拟结果表明蒸发或者升华控制了整个过程。以扩散模型和以对流模型所得到的结果都与实验结果在一定程度上吻合，这是因为通过对流或者导热所传递的热量比相变潜热要小几个数量级。在整个结晶过程中液滴温度的变化表明：液固相变要占据较长的时间，是一个更为重要的过程。考虑重力、浮力和粘滞力的影响给出了液滴在结晶过程中的运动方程。从该模型计算出的液滴结晶过程中下降距离比仅考虑重力作用下给出的要准确。研究结果为更好的设计真空闪蒸室提供了理论依据和参考。
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