Performance of a novel natural draft hybrid cooling system with serial airside heat exchange

Natural draft dry cooling system (NDDCs) of thermal power plants is susceptibly affected by ambient conditions. Moreover, the flexibility of cold-end system must be improved to satisfy load fluctuations in power grids caused by the rapid spread of power generation capacity from unpredictable renewable energy sources. To overcome the shortage of traditional cooling systems, a natural draft hybrid cooling system (NDHCs) with airside in series is proposed. Based on the control equations of flow, heat and mass transfer, an iterative algorithm is developed to predict the performance of NDHCs. Compared with the natural draft dry cooling system (NDDCs), natural draft wet cooling system (NDWCs) and recently proposed Pre-cooled NDDCs, the annual performances of NDHCs are investigated based on the practical weather data. The results indicate that NDHCs shows more priority in the areas rich in coal but short of water. Compared with the NDDCs, the operation cost of NDHCs drops 46.89 $/h. In terms of requirements for flexible operation, NDHCs can improve the dispatchability of power plants with varying the water mass flow rate ratio. With increasing water of the wet section, heat load varies about 48%. Moreover, NDHCs can avoid visible plumes and further pollution caused by the plumes effectively, since the saturated air is warmed by dry section and within the sub-saturated region.