Numerical simulation of the influence of flue gas discharge patterns on a natural draft wet cooling tower with flue gas injection

•The discharge pattern with distributed flue gas vents is proposed.•The effect of discharge site and direction on the efficiency of tower is discussed.•The influence of the flue gas flow rate on the NDWCT performance is studied.•The optimal vents quantity and discharge direction are given.•The optimization model that can be generalize the result to other NDWCTs is proposed. This paper introduces a distributed arrangement of flue gas emissions and presents conclusions on the optimal placement and quantity of flue gas vents in a certain horizontal plane of a natural draft wet cooling tower (NDWCT). An NDWCT set up based on the arrangement of flue gas vents established herein will raise efficiency with the increase of radial distance and flue gas vents. The authors found a way to inject flue gas at a certain angle, which can make the flue gas and humid air in the tower swirl upward, thereby increasing the pumping force of the cooling tower and further improving the cooling tower efficiency. When the incident angle is parallel to the generatrix of the hyperboloid cooling tower, the cooling tower efficiency is maximized. The flue gas flowrate effect on the cold-water temperature was also investigated based on determining the optimal value of the radial distance, quantity, and angle of the flue gas vent reach. Moreover, the formula that can be generalize the result to other NDWCTs is obtained to reach the optimal emission mode of flue gas. Comparing with the case before improved, the flow rate of NDWCT increases by 822.05 kg/s (18.9%), and the cold-water temperature decreases by 1.12 k, under a 200% flue gas flowrate.