Numerical Investigation On The Fluid Flow And Heat Transfer Of V-type Direct Air-cooled Condenser Unit

The direct air-cooled units,with its excellent water-saving performance,saved a large amount of water resources for the rich coal and poor water areas in northern China,greatly alleviate the contradiction between electric power development and water resources.The arrangement mode of direct air-cooled units can significantly affect its heat transfer performance.In this thesis,the "V" type air-cooled unit,which is different from the traditional arrangements,will be studied to explore the flow and heat transfer characteristics of the "V" type air-cooled unit under different environmental conditions,which will provide more important theoretical basis for further optimization of the air-cooled unit structure.In this thesis,a 600 MW direct air-cooled unit is used as the research object,and the numerical simulation method is used to study the flow and heat transfer characteristics of the "V" type air-cooled unit.Firstly,the flow and heat transfer characteristics of the "V" type air-cooled unit and "(?)" type air-cooled unit are comparatively analyzed in different ambient wind direction and wind speed,and the heat transfer performance of the "V" type air-cooled unit is studied indifferent ambient air temperature.Secondly,in view of the adverse effect of environmental wind on the "V" type air-cooled unit,a diversion device,with an angle decreases step by step,is put forward,and is added at the bottom of the air-cooled unit,and the diversion effect of the diversion device with different structure size and arrangement is analyzed.The aim is to seek the optimal arrangement of the diversion device.The research shows that the "(?)" type air-cooled unit by the environmental wind impact is more significant than the "V" type air-cooled unit,and when the ambient wind speed is large,the former has poor heat transfer performance.In the different ambient wind direction,the heat transfer performance of the "V" type air-cooled unit is the worst at the angle of 45° wind direction.The cooling capacity of the air is reduced by the increase of the ambient temperature,which makes the heat transfer of the "V" type air-cooled unit deteriorate rapidly,and the heat transfer amount decreases linearly with the increase of the ambient temperature.The increase of the width of the guide plate can partially suppress the influence of environmental wind on the finned tube bundles of windward side of the "V" type air-cooled unit.The optimal width of the guide plate is 6m,and the heat transfer capacity of the "V" type air-cooled unit with 6m wide guide plate compared to 2m wide guide plate has been increased by 4%.The influence analysis of the inclination angle change of the guide plate is obtained that the parallel arrangement of the guide plate is more easier to generate vortex than the guide plate with decreasing angle on the leeward side of the guide plate.However,when the inclined angle of the guide plate is too large,the vortex will also be generated on the leeward side.The existence of the vortex mainly affects the diversion effect of the deflector on the leeward side fin tube bundle of the "V" type air-cooled unit.The optimal tilting angle of the diversion device is 45°,and it is more reasonable to arrange in the way of 5° decreasing layer by layer.The variation of the guide plate spacing will affect the diversion effect of the finned tube bundles on the windward side and leeward side of the "V" type air-cooled unit,and the optimal diversion spacing is 3m.The increase of the layer number of the diversion device can make the guide air flow more uniform and stable.When the ambient wind speed is 11m/s,the heat transfer capacity of the "V" type air-cooled unit installed 4 layers of guide plates is higher than that of 1 layer of guide plate by 10.1%.