Subregional modulation of axial flow fans to reduce condensate supercooling of air-cooled steam condenser in cold days

Abstract

For the air-cooled steam condensers (ACSCs) in the power station, the power consumption of axial flow fans accounts for a large proportion of the auxiliary power, which can be optimized by their rotational speed modulation. In this work, the subregional modulation strategies of axial flow fans in cold days are studied to reduce the supercooling of condensate in ACSCs as much as possible. For the steam-side and air-side heat transfer coupling in ACSCs, the macro heat exchanger model is adopted with the steam thermo-flow process solved, where the water phase state change is characterized by the steam enthalpy. Besides, the exhausted steam condensation in the down-flow bundles and the residual steam condensation in the up-flow bundles are both taken into consideration. Under the working conditions of choking turbine back pressure for an ideal power generating efficiency, the inlet temperature and flow rate of cooling air for each condenser cell are obtained, the condensate outlet temperature of the up-flow bundles and the total fan power consumption are calculated in terms of different modulation methods. The results show that the subregional modulation is superior to the uniform modulation with the maximum power conservation of 362.8 kW, which can be recommended in the practical operation of axial flow fans for ACSCs in winter.