Abstract: [Objectives]　Taking a natural draft wet cooling tower in a power plant as the research object, this study addresses the problem of excessive air velocity in the outer zone under the unequal-height layout, which leads to reduced heat and mass transfer efficiency. Therefore, an optimization method involving a denser layout in the outer zone is proposed to improve airflow distribution and thermal performance. [Methods]　First, the filling with a spacing of 30 mm in the outer zone is replaced by filling with a spacing of 26 mm to design five denser layout schemes with different heights. Then, a three-dimensional numerical model is established to simulate and analyze the temperature field, as well as the thermal performance of both the outer zone and the whole tower under each scheme. Finally, by comparing the performance indicators under typical operating conditions in different seasons, a relatively optimal filling denser layout scheme is determined. [Results]　The results show that the filling denser layout can improve the uniformity of the temperature field inside the cooling tower. Under design operating conditions, both the water temperature drop and Merkel number increase with greater denser layout height, but the rate of increase shows a diminishing trend. The optimal denser layout schemes differ under typical operating conditions in different seasons. Through comprehensive comparison, densifying the bottom 1.00 m of the filling in the outer zone is identified as a relatively optimal scheme. Under design operating conditions, this scheme can increase the water temperature drop and the Merkel number by 0.135 ℃ and 0.09 respectively, and can achieve significant optimization effectiveness under different operating conditions in different seasons. [Conclusions]　This optimization method can effectively enhance the thermal performance of cooling towers, thereby providing a theoretical basis and engineering reference for research on optimizing filling layout in cooling towers.

Key words: thermal power generation, natural draft wet cooling tower, filling zone, unequal-height filling, outer zone optimization, denser layout, thermal performance, numerical simulation