Performance Evaluation Of Direct Air-cooled Steam Condenser With Fan Inlet Swirl Reducer

Due to the shortage of water resources,direct air-cooled units have been rapidly popularized in areas that are rich in coal and short of water.Direct air-cooled condenser uses air instead of water as cooling medium,and its p erformance is easily affected by ambient wind.Optimizing the flow fields of air-cooled system under the effect of ambient wind for improving the flow and heat transfer characteristics is of great importance.Under the effect of the ambient wind,the negative pressure area will be formed at the inlet of the axial flow fans,especially near the wall of the air inlet barrel.The air in the negative pressure area is generally in the eddy current state,forming a local flow dead zone,which will reduce the air flow of the air cooling unit,and seriously affect the heat exchange performance of the air-cooled steam condenser.On the basis of a representative 600 MW direct air-cooled unit,the numerical analysis model of the effect of ambient wind on the heat transfer performance of air-cooled island in single row air-cooled unit and plant environment is established.Starting from weakening the vortex at the air inlet of the air cooling unit and reducing the range of negative pressure area,eight kinds of fan inlet swirl reducer are designed,the flow field characteristics of the unit after the installation of the device are obtained,and the influence of the swirl reducer on the heat exchange efficiency of the direct air condenser is analyzed.The optimization effect of the above 8 kinds of structure parameters of the swirl reducer is compared,and the device with the better performance is selected to explore the best location in the air-cooled island.The results show that the installation of swirl reducer can alleviate the flow distortion at the fan inlet,obviously weaken the vortex at the fan inlet,narrow the negative pressure area at the fan inlet,effectively increase the fan output,reduce the average temperature at the fan inlet,and greatly improve the heat exchange efficiency of the air cooling unit.Under the eight simulated size conditions,when the side wall is hyperbolic,the height is 4m,the inlet diameter is 7m,and the outlet diameter is 5m,the heat transfer performance of the air cooling unit increases the most.Considering the air cooling island as a whole,the best effect is that the swirl reducers are installed beneath the edge air cooling unit.When the ambient air blows from the back or side of the boiler house,the swirl reducers can increase the distance of the hot air and restrain the adverse effect of the hot air recirculation;when the air comes from the front of the boiler house,it can effectively avoid the reverse flow of the air cooling unit on the windward side,so as to improve the heat exchange efficiency of the air condenser.