Ventilation enhancement for a natural draft dry cooling tower in crosswind via windbox installation

A natural draft dry cooling tower (NDDCT) is demanded to save water for power generation in arid area, but its performance could be degraded greatly by the crosswind. To overcome the degradation, this paper proposes the installation of a windbox, which consists of windbreaks, an enclosure, a back barricade and a wind top to improve the pressure distribution outside the heat exchanger bundle of a NDDCT, so as to increase the ventilation rate under crosswind condition. Full dimensional computational fluid dynamics (CFD) modelling was conducted for the windbox installed around the NDDCT of a large scale coal-fired power plant. Different configurations of the windbox were studied. The flow characteristics along the streamline in the NDDCT were analyzed and quantified by adopting the concept of flow loss factor (FLF). Based on simulation and experiments, the installation of the windbox is shown to be effective. The windbox with a 120 m radius enclosure and a full size louver-type top could improve the ventilation rate of a NDDCT by similar to 60% in gale crosswind condition, and keep high performance in breeze crosswind condition. Consequently, an annual reduction of coal consumption of 30,000-45,000 tons could be achieved on a 1000 MW unit, which is similar to 3000,000-4500,000 $/a.