Performance prediction and cost-effectiveness analysis of a novel natural draft hybrid cooling system for power plants

Natural draft dry cooling system (NDDCs) utilizes ambient air as cooling medium and is susceptible the ambient conditions. Natural draft wet cooling system (NDWCs) can provide adequate cooling capacity by consuming large amount of water but forms visible plumes. A novel natural draft hybrid cooling system (NDHCs) which consists of both dry and wet components is proposed in this study as a means to be in conflict with the protection and conservation of water resources. With full consideration of its control equations of flow, heat and mass transfer, an iterative algorithm is developed to predict the performance of NDHCs. Coupled to a practical coal-fired power unit, the annual performances of the three systems, as well as the trade-off of the water consumption rate and saved coal consumption rate are explored. The results indicate that during extreme hot days, NDHCs shows more priority over NDDCs and NDWCs. The annual performance of NDHCs is better than NDDCs and NDWCs due to its parallel connection of air, which brings more air passing through the tower. Compared with NDDCs, the playback period of the modification is only 1 year though there is a slightly underestimation due to the structure difference of tower. Furthermore, NDHCs can avoid plumes and further pollution caused by the plumes effectively, since the saturated/supersaturated air will be warmed by the air from dry section and within the sub-saturated region.