Comparative study on the thermal characteristics of natural draft wet cooling tower with internal and external auxiliary fans

Abstract

Auxiliary ventilation is an innovative approach for strengthening the thermal performance of natural draft wet cooling towers, which can be implemented with internal and external fans. In this study, a three-dimensional numerical model for cooling tower with these fans is established, with consideration of the existence or absence of air deflectors. To comparatively study the thermal performance of the above cooling towers, some critical parameters such as the air mass flow rate and circulating water temperature drop are computed, and the airflow and water temperature field are also investigated. Results manifest that external fans can enhance the air mass flow rate greater than internal fans under various crosswind velocities, while they are more effective in increasing the water temperature drop under a lower and a higher crosswind velocity, with a maximum increment of 8.5% and 10.0%, respectively. The addition of air deflectors narrows the high-velocity area, thus improving the uniformity of air distribution. The positive effect of air deflectors enhances with the increase of crosswind velocity, which decreases the water temperature drop of cooling tower with internal fans and that with external fans by 10.3% and 5.6% at most, respectively. This study can promote the engineering applications of auxiliary fans.