Cooling performance of natural draft hybrid system with parallel air path

The flexibility of the dry cooling system in thermal power plant needs to be improved to suit the load undulation caused by the increased renewable energy power. For overcoming the weakness of conventional cooling system, a natural draft hybrid (dry/wet) cooling system (NDHCS) is proposed to fully take advantage of dry and wet cooling technologies, which comprises the wet and dry cooling sections with parallel air flow path. The three-dimensional numerical models are developed to investigate the thermal-flow performances of the NDHCS under various environment and operation conditions, by which the flow fields near the NDHCS as well as the heat and mass transfer between circulating water and cooling air are obtained. The results show that both the dry and wet cooling sections dominate the cooling capacity of the hybrid system but the performance of the former is inferior to the latter in most of the cases. Low ambient humidity, large spraying water flow ratio in the wet cooling section and small wind speed are of benefit to the thermal performance of hybrid cooling system. For the dry and wet cooling sections themselves, the cooling performance can be improved thanks to the ambient wind under specific conditions. Besides, NDHCS can effectively avoid visible plume especially under windy conditions.