Effect mechanism of wind shields on the thermal performance for mechanical draft wet cooling towers

Abstract

Environmental crosswind is demonstrated to be disadvantageous for the thermal characteristics of mechanical draft cooling towers. To mitigate the adverse effect of crosswind, this study proposes an innovative structural retrofit by adding wind shields with simple structure for both single and double air inlet cooling towers. Numerical investigations are conducted to clarify the effect mechanism of wind shields on tower thermal performance under different crosswinds, through assessing the ventilation rate, the water temperature drop, the air flow field and water temperature field, etc. Results demonstrate that wind shields can eliminate transverse vortices to improve the distribution homogeneity of airflow velocity and water temperature, of which the effects are greatly affected by crosswind velocity and angle. Based on this mechanism, the thermal performance of these cooling towers is prominently strengthened by wind shields when crosswind angle exceeds 45°. The positive effect of wind shields is the most noticeable under a crosswind angle of 90° and a crosswind velocity of 10 m/s, which recovers 17.2 % and 9.4 % of the water temperature drop, and 33.1 % and 19.5 % of the ventilation rate, respectively for the single and double air inlet cooling tower. Present findings can promote applications of wind shields in practical engineering.