[en] Highlights: • The performance of non-uniform fillings for wet cooling towers is studied in lab. • Non-uniform fillings can alleviate adverse effect of crosswind on cooling towers. • P4 is optimal non-uniform pattern if giving the priority to energy conservation. • P3 is the optimal pattern if considering water-saving characteristic preferentially. A thermal-state model experimental study was performed to investigate the drag characteristic and thermal performance of non-uniform fillings for wet cooling towers under crosswind conditions, several valuable performance parameters, including cooling efficiency, drag coefficient, ventilation rate, heat transfer coefficient and Merkel number, etc. were analyzed in this paper. Experimental researches proved that the non-uniform fillings are not sensitive to the crosswind, and can alleviate the adverse effect of crosswind on wet cooling towers. From the perspective of drag characteristic and thermal performance, the P4 pattern is the optimal non-uniform pattern under crosswind conditions, which has the higher ventilation rate, heat transfer coefficient, Merkel number and lower drag coefficient within the experimental crosswind velocity range. However, the P3 pattern has the lower evaporation loss and the outstanding relatively water-saving performance. Therefore, studies in this paper revealed that the optimal non-uniform pattern should be selected by terms of comprehensive consideration of energy conservation and water-saving. The P4 pattern is the optimal non-uniform pattern if giving the priority to energy conservation, and conversely, the P3 is the optimal pattern if considering water-saving characteristic preferentially.

[en] Highlights: • Thermal performance is experimentally studied for wet cooling tower with axial fan. • Forced ventilation improves the inlet air uniformity under crosswind condition. • Water temperature drop enhances by 6.46–13.35% at forced ventilation pattern. • Merkel number enhances by 0.69–5.62% at forced ventilation pattern. -- Abstract: In this paper, an axial fan was introduced for thermal performance improvement of super-large natural daft wet cooling towers (S-NDWCTs), and the model experiment was performed to study the thermal performance of S-NDWCTs installed with an axial fan under windless and crosswind conditions. The experimental results manifested that, compared with traditional natural ventilation pattern, the thermal performance of forced ventilation is outstanding by analyzing the inlet air uniformity coefficient, cooling water temperature drop, Merkel number, etc. Moreover, the cooling water temperature drop is proportional to fan power under windless condition, and it enhances approximately by 12.06% at 3.77 W fan power, compared with natural ventilation pattern. Under crosswind conditions, the inlet air uniformity coefficient (ψ) and the water temperature difference on the water basin surface at forced ventilation pattern are more uniform than those of natural ventilation pattern, and ψ at 2.67 W condition increases by 8.08% compared with natural ventilation pattern while the crosswind velocity reaches to 0.6 m/s. Additionally, the cooling water temperature drop and Merkel number at forced ventilation pattern are also higher than those of natural ventilation pattern. Compared with natural ventilation pattern, these two parameters enhance by 6.46–13.35% and 0.69–5.62%, respectively within the experimental crosswind velocity ranges (0–0.6 m/s).

[en] Highlights: • Field tests of the NDWCT were implemented before and after structural improvement. • The effects of structural improvements on the NDWCT were analyzed. • Structural improvements enhanced the ventilation and thermal performance of NDWCT. • The Merkel number increased significantly after structural improvement. -- Abstract: In order to improve the operating performance of the natural draft wet cooling towers (NDWCTs), some structural improvement measures, including adding air-deflectors, using non-uniform fillings, and adding air-ducts, were taken in one large-scale NDWCT in China. The effects of structural improvement on the ventilation and thermal performance were researched based on the field test method. Field test results showed that, in the crosswind velocity range of 1.15–3.2 m/s (test condition), the thermal and ventilation performance decrease gradually with the rising of crosswind velocity, but the structural improvement weakens the adverse influence of crosswind. Compared with before structural improvement, the intake air uniformity coefficient, the ratio factor of ventilation rate, the temperature uniformity coefficient, and the ratio factor of Merkel number increase by about 36.6%, 15.5%, 5.5%, and, 14.5%, respectively. It manifested that the structural improvement for the NDWCT can improve the thermal and ventilation performance to a great extent.