Numerical analysis of crystallization and freezing of flying droplet in artificial snowmaking

Artificial snowmaking is a kind of spray freezing, including heat and mass transfer and crystallization. The freezing process of flying droplets is complex, involving various transient characteristics. In this paper, the aim is to explore the transient characteristics of flying droplet freezing process during artificial snowmaking. A numerical model of flying droplet freezing is established combining with heat transfer theory and crystallization kinetics after experimental validation. The model incorporates the compressible flow, gas throttling, air entrainment and droplet trajectory to reveal the transient properties of flying droplet. The influence of ambient and operating parameters on the freezing time is comprehensively studied, such as the initial droplet temperature, diameter and velocity, the ambient temperature, humidity and pressure and the Mach number of airflow from nozzle. It is found that the influence of ambient temperature, droplet diameter, and Mach number is more significant on droplet freezing. When the ambient temperature is −5 °C and the Mach number is 3, the lowest temperature of 50 μm droplets can reach −7.13 °C. Finally, a critical criterion for snowmaking is proposed, which provides a new approach to compensate for the insufficient ambient temperature by adjusting the initial droplet diameter and Mach number.