Analysis of structural improvement and potential energy recovery in the rain zone of natural draft wet cooling tower

To address the issues of mismatched resistance and heat transfer characteristics in the rain zone of natural draft wet cooling towers (NDWCT), as well as the insufficient utilization of potential energy, this paper proposes a potential energy recovery model. This model quantifies the recoverable potential energy in the rain zone based on the distribution characteristics of water droplets in the NDWCT. The recovered energy is then used to drive fans, improving both the resistance and heat transfer performance of the NDWCT. Using the NDWCT of a 1000 MW nuclear power unit as the research object, eight types of water collection plates with a coverage rate of 25 % were designed. These plates are used to collect circulating water to drive water turbines , which in turn power the fans. Calculations show that all designs can recover more than 450 kW of potential energy from falling water. After determining the recoverable potential energy, the thermal performance of NDWCT, HNDWCT (High-level water collecting natural draft wet cooling tower), NDWCT with dry-wet hybrid rain zone, and NDWCT with both dry-wet hybrid rain zone and potential energy recovery was compared under different environmental crosswind conditions. The results show that the performance of HNDWCT declines sharply under higher crosswind speeds. When the crosswind speed reaches 8 m/s, its heat exchange capacity decreases by 51.6 % compared to windless conditions, leaving it at only 63.1 % of the heat exchange capacity of NDWCT, with an outlet water temperature 3.66 °C higher than that of NDWCT. In contrast, the cooling tower modified with the dry-wet hybrid rain zones and potential energy recovery technology was less affected by crosswinds, with cooling capacity reductions of 5.4 % and 10.3 % at 4 m/s and 8 m/s crosswinds, respectively, whereas NDWCT exhibited reductions of 7.1 % and 11.1 %. Additionally, the former demonstrated superior performance under all crosswind conditions, the outlet water temperatures under windless, 4 m/s, and 8 m/s crosswind conditions decreased by 0.49 °C, 0.65 °C, and 0.53 °C, respectively, with heat exchange capacity improvements of 4.4 %, 6.3 %, and 5.3 %. Compared to traditional dry-wet hybrid rain zone towers, the cooling tower with the dry-wet hybrid rain zones and potential energy recovery technology is less affected by environmental crosswinds. The outlet water temperature decreased by 0.11 °C, 0.2 °C, and 0.17 °C under windless, 4 m/s, and 8 m/s wind conditions, respectively.