Investigation on a good combination of inlet air spray pre-cooling and Y-type windbreak in a natural draft dry cooling tower

Abstract

Crosswind affects the airflow of natural draft dry cooling towers (NDDCTs), which will in turn affect the trajectory of spray water droplets and will impair the pre-cooling effect of NDDCTs. This study develops 3-D models to simulate the operation of a 120 m high NDDCT with seven spray pre-cooling schemes and Y-type windbreak, aiming to optimize their combination. The simulation finds that: (1) The one-circle arranged spray nozzles increase the tower's heat rejection rate up to 7.01 % (increased from 123.68 MW to 132.35 MW) compared with no spray while the linear-arranged spray nozzles increase the heat rejection rate up to 5.84 % (increased from 123.68 MW to 130.90 MW); (2) The three-circle nozzle arrangement produces the highest heat rejection rate as 147.99 MW with an 22.89 % improvement compared with no spray, while the one-circle nozzle arrangement with the radius of 21.50 m produces the lowest heat rejection rate as 129.10 MW with an 7.21 % improvement; the water evaporation ratio follows the order of one-circle at the radius 41.50 m as 100.00 %, two-circle as 99.00 % and three-circle as 98.52 % is the last; (3) The two-circle arranged spray nozzles with the radii of 31.50 m and 41.50 m, the total water flowrate of 14.8 kg/s and nozzle number of 74 are found to be a good combination with the Y-type windbreak for performance improvement of the NDDCT, which improves the heat rejection performance of the NDDCT well (with 15.84 % improvement, i.e., increased from 120.42 MW at no spray to 139.49 MW) with moderate water consumption (not too high and not too low) of 14.8 kg/s and high water evaporation ratio of 99.00 %.