Ratio analysis of two mechanisms of static droplet evaporation driven by pressure difference
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When droplet moving in the steam-water separator, the gas pressure will decrease due to flow resistance and the liquid-vapor equilibrium at the droplet surface will be broken. The droplet evaporates continuously as a result. The fast evaporation mechanism and thermal balance evaporation mechanism are presented for the droplet evaporation at cases of pressure variation. The droplet phase change model due to pressure variation is formulated. Subsequently, the effects of pressure difference on the droplet evaporation characteristics are analyzed. The ratio analysis of the two mechanisms is conducted. The droplet evaporation map over the ratio of two mechanisms is drawn. The numerical results indicate that the pressure difference significantly influences the droplet evaporation characteristics. Under most conditions, the droplet evaporation characteristics are dominated by the combined action of two mechanisms. For large pressure difference and small droplets, the fast evaporation mechanism dominates the evaporation process, and vice versa. With increasing pressure difference between the droplet and the surrounding environment, the droplet evaporates faster and the percentage of fast evaporation mechanism decreases gradually. The present work can lay the foundation for further investigation on the moving droplet evaporation.
Keywordsdroplet evaporation map pressure difference ratio analysis fast evaporation mechanism thermal balance evaporation mechanism
The authors are grateful for the support of this research by the National Key R&D Program of China (No. 2017YFE0106200), Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of Education (ARES-2018-02), and Science and Technology on Reactor System Design Technology Laboratory (HT-KFKT-09-2018004).
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