Optimization Study Of Water Flow Distribution For Natural Draft Dry Cooling System Under Crosswinds

Indirect dry cooling system in thermal power plants uses air as cooling medium to cooling the circulating water in air-cooled heat exchanger.In wind condition,ambient winds will significantly affect the thermo-hydraulic performance of air-cooled heat exchanger and cooling tower.So effective measures should be taken to reduce the impact caused by ambient winds.By establishing the coupling model of air-cooled heat exchanger,cooling tower and condenser,the research of the thermo-hydraulic performance of indirect dry cooling system under different water flow redistribution schemes in wind conditions are achieved.The velocity,pressure and temperature fields of cooling air at various wind speeds are presented and the variation law of outlet water temperature and tubing back pressure are obtained.Through the optimization study of water redistribution,finding that heterogeneous water distribution between different segments has a significant impact on the thermo-flow performance of air-cooled heat exchanger and cooling tower.According to the characteristic that the cooling efficiency of windward sectors will improve while the cooling efficiency of lateral ones will decrease under crosswinds,four different schemes of circulating water flow heterogeneous distribution are designed.In these schemes,the water flow rate of windward sectors increaseds gradually,and the water flow rate of lateral sectors decreases gradually.Under the same water flow redistribution scheme,when the ambient wind speed changes,transfer the circulating water flow from lateral sectors to windward sectors can effectively improve the cooling performance of air-cooled heat exchanger,and reduce the oulet water temperature and turbine back pressure.The optimization effect will improve with the increase of wind speed.The comparison of the four distribution schemes shows that when the wind speed is greater than 8m/s,the outlet water temperatures and turbine back pressures of these four redistribution schemes are all less than the uniform distribution.And greater extent of heterogeneous water distribution corresponds to lower outlet water temperature and lower turbine back pressure.A theoretical-numerical iterative calculation process is established to obtain the optimized water redistribution schemes under different wind conditions.The final result shows that utilizing the optimized water redistribution under certain wind speed can gain the lowest outlet water temeprature and turbine back pressure.