Exploratory research on annular-arranged moist media to improve cooling capacity of natural draft dry cooling tower and thermo-flow characteristics of its radiators

Abstract

The well-arranged moist media should be a promising solution to improve the thermal performance of the natural draft dry cooling tower (NDDCT) by the synchronous implementations of air inflow field optimization and inflow air pre-cooling. In the present study, a 3D numerical model coupling a full-scale NDDCT and annular-arranged moist media was established, and the effects of the introduced moist media were explored by numerical simulation. Results show that the moist media are effective to increase the cooling capacity of the NDDCT under crosswind, with the maximum increment of 20.9% achieved at the medium wind speed of 8 m/s. The cooling capacity of the tower after the action of the moist media under the wind speed of 4 m/s exceeds the original maximum one. Through air inflow field optimization provided by the media, thermo-flow characteristics of the delta-form radiators improve. Performance deviation among the radiators alleviates, and the two cooling columns of each radiator almost have identical performance. With the further implementation of inflow air pre-cooling, each radiator, especially its cooling column right downstream the medium, obtains a further performance improvement. Under crosswind, inflow air pre-cooling is generally superior to air inflow field optimization on promoting tower performance, but the opposite result is achieved at the wind speed near 8 m/s. From the view of cost-effectiveness, the introduced moist media are most efficient at the wind speed of 6 m/s, and a 1.50 MW increment in the cooling capacity of the tower can be achieved by every 1 kg/s water evaporation.