[Objective] The radiators of indirect air-cooling towers in inland nuclear power plants are prone to freezing and cracking under the coupling effect of low winter temperature and crosswind. To solve this practical engineering problem, this study fills the research gap regarding the performance of anti-freeze roller shutters under complex wind conditions. It quantitatively clarifies the correlation between the shutter drop distance and anti-freezing performance, aiming to ensure the safe, stable and economic operation of nuclear power units in winter. 

[Methods] A typical large-scale industrial indirect air-cooling tower for inland nuclear power generation is selected as the core research object in this study. A refined full-scale three-dimensional numerical model of the cooling tower is established and verified through mesh independence analysis based on FLUENT fluid simulation software. Combined with real field meteorological monitoring data, the typical winter temperature and wind field parameters of the plant site are accurately configured. Two representative operating conditions, namely the no-wind static condition and the 4 m/s typical winter crosswind condition, are adopted to systematically simulate and analyze the effects of varying drop distances of anti-freeze roller shutters on the overall outlet water temperature and the spatial water temperature distribution characteristics of each cooling sector of the tower. 

[Results] The simulation results indicate that the drop distance of the anti-freeze roller shutter presents a significant positive linear correlation with the tower outlet water temperature. For the investigated tower type, every 1-meter increase in the shutter drop distance steadily raises the outlet water temperature by approximately 0.5 ℃. Under both no-wind and 4 m/s crosswind conditions, the outlet water temperature exceeds the critical anti-freezing threshold of 20 ℃ when the shutter drops by 36 m, covering about 75% of the total air inlet height. Crosswind severely disturbs the uniformity of the internal flow field, leading to unbalanced heat exchange among different sectors with a maximum water temperature difference of 3 ℃. The 110° windward area and 65° leeward area are identified as freezing-vulnerable sectors. Increasing the shutter drop distance can effectively weaken the wind-induced water temperature attenuation and greatly balance the water temperature distribution across all sectors. 

[Conclusion] Based on extensive numerical simulation data and statistical analysis, empirical formulas for calculating the optimal overall shutter drop distance corresponding to different target outlet water temperatures under the two typical winter wind conditions are derived. A targeted local anti-freezing enhancement strategy is proposed for freezing-prone sectors, which requires an extra 6 m drop distance on the basis of overall unified regulation. The research findings provide a reliable quantitative basis and practical technical support for precise anti-freezing regulation and stable high-efficiency winter operation of indirect air-cooling towers in inland nuclear power plants.