A novel performance improvement technology of wet cooling towers with the dry-wet hybrid rain zone by auxiliary fans

To address the bottleneck of limited air supply in the central region of super-large wet cooling towers, this study proposes a novel technology that combines the dry-wet hybrid rain zone with auxiliary fans. Using numerical simulations, the effects of fan number and arrangement layout on the internal flow field structure and heat transfer performance of the cooling tower were systematically investigated, and the economic feasibility of the proposed technology was evaluated. The results indicate that a reasonable fan arrangement layout has a more significant impact on overall tower performance than simply increasing the power of individual fans. Among the tested configurations, the III-1 arrangement layout achieved the best performance in improving the tower's ability to draw in ambient air. With a total auxiliary fan power of 200 kW, this configuration increased ventilation rate, water temperature drops, cooling efficiency, and Merkel number by 2.77 %, 0.24 °C, 1.68 %, and 3.45 %, respectively, compared with the dry-wet hybrid rain zone tower; the corresponding improvements compared with an original usual cooling tower were 4.37 %, 0.68 °C, 9.03 %, and 18.52 %, respectively. Techno-economic analysis indicates that, compared with the original usual tower power generation unit, the coal consumption rate and the carbon emissions of the unit are reduced by 0.75 g/kWh and 7336.36 t/a, respectively; under typical economic parameters (cooling efficiency gain coefficient of 1.1 g/kWh, construction cost coefficient of 2500 RMB/kW, and discount rate of 6 %), the payback period is about one year, and remains below four years even under extreme conditions, indicating strong economic viability.