New method to decrease the air recirculation of mechanical draft wet cooling tower group by increasing height of fan duct

Abstract

The air recirculation will increase the temperature and moisture content of air entering the mechanical draft wet cooling tower group (MCT group) and seriously reduce the cooling capacity. This study proposes to increase the height of the fan duct to reduce air recirculation. The aerodynamic field outside the MCT group is reconstructed to improve the cooling capacity of MCT group. A 3D model is established to explain the influence mechanism of air recirculation and the change of the thermal performance of MCT group. The main research variables are crosswind speed and direction. The numerical results show that, after the retrofit, the air recirculation rate of leeward MCT is reduced by 10.9 % on average and 16.0 % at most under the crosswind angle of 0°, 16.8 % mean and 25.0 % maximum under 45°, 1.0 % average and 2.0 % at most under 90°. The water temperature drop is increased by 0.5 °C on average and 0.8 °C at most under 0°, 0.7 °C mean and 1.1 °C maximum under 45°, 0.1 °C on average and 0.2 °C at most under 90°, compared to original MCT group.