As the core heat transfer unit of natural draft dry cooling tower (NDDCT), the air side flow and heat transfer characteristics of cooling deltas are very crucial to the overall performance of NDDCT and its system. Based on one real running NDDCT for an air cooling turbo-generator unit about 1000 MW, the field experimental study was carried out around two typical cooling deltas with an intersection angle about 90° between their two angular bisectors. For the two chosen cooling deltas individually located in the windward cooling sector and the lateral cooling sector relative to the local prevailing wind direction, the local face wind velocities, wind temperatures and tube bundle wall temperatures were measured along the windward side of each cooling column, so as to analyze their distribution characteristics and then reveal the generality of cooling delta air side flow and heat transfer characteristics. Gathered data in a long period show that the uneven distribution of air side flow usually exists for most cooling deltas either at the windward side or tower lateral side, which causes the cooling performance difference between the two cooling columns in one cooling delta. Usually, the tube bundle wall temperature is higher for cooling column with lower face wind velocity, where the cooling efficiency is relatively poor. The tube bundle wall temperature is lower for cooling column with higher face wind velocity, where the anti-freezing is essentially required especially in winter. So the aerodynamic field around cooling deltas should be reconstructed to improve its both cooling performance and anti-freezing performance. © 2020 Chin. Soc. for Elec. Eng.
