Numerical Study On The Structure Optimization Of Air-cooled Unit Guiding Device Adapted To Ambient Conditions

With its excellent water-saving capacity,direct air-cooled technology has been rapidly developed in water-scarce areas in northern country,and has made great contributions to the development of power in the coal-rich and water-deficient areas in the north of country.The heat exchange performance of the direct air cooling unit is greatly affected by the ambient wind.On the one hand,the suction capacity of the fan decreases,and on the other hand,there are local high temperatures at the bottom corners of the radiator.The thesis optimizes the design of the direct air-cooled unit under the influence of the ambient wind field to improve the flow state of the cooling air to obtain the purpose of enhancing heat transfer.Based on the 600 MW direct air-cooled unit,the numerical simulation method is used to study the flow and heat transfer performance of the air-cooled unit under the influence of the ambient wind field.Firstly,the influence of different ambient wind speeds on the flow and heat transfer performance of the direct air cooling unit is simulated and analyzed,and the flow and heat transfer characteristics of the air cooling unit with baffles installed inside,outside,inside and outside are compared and analyzed.Secondly,the optimal design of the inner and outer deflectors of the air-cooling unit is carried out,the influence of the number,inclination and width of the deflectors on the heat transfer performance of the air-cooled unit is analyzed,and the optimal layout of the deflector is obtained.Research shows that when the ambient wind speed increases,the air volume of the fan decreases,the average temperature of the air at the outlet of the radiator increases,and the performance between the cooling air and the radiator weakens.When the ambient wind speed is 2m/s,the fan air volume and the average temperature of the radiator outlet on the windward side are 497.22m~3/s and 317.33 K,respectively.When the wind speed increases to 10m/s,the fan air volume decreases by 31% and the average temperature increases by 13.15 K.Compared with the other two baffle installation methods,the inside and outside of the air cooling unit comprehensive application of the baffle is more advantageous.When the ambient wind speed is 8m/s,the average air temperature at the outlet of the radiator on the windward side is the lowest,which is reduced to 317.49 K.The average temperature of the outlet air of the radiator on the windward side of the air-cooling unit with separate internal and external baffles is324.93 K and 319.63 K,respectively.It can not only increase the air volume of the fan,but also eliminate the local high temperature at the bottom of the radiator.Taking the average temperature of the outlet of the radiator on the windward side as the objective function,and optimizing the design of the number,inclination and width of the inner and outer deflectors of the direct air cooling unit,the layout of the deflector with the lowest average temperature of the radiator outlet on the windward side is obtained.The optimal number,inclination and width of internal and external deflectors are respectively 6 and 4,30° and 60°,1m and 7m.Compared with the direct air-cooled unit without baffle,the average temperature of the radiator outlet on the windward side is 318.74 K.The heat exchange effect between the radiator and the air of the air-cooled unit with the optimized baffle of the structure size is improved.The average temperature of the radiator outlet on the windward side is 314.53 K and reduced by 4.21 K.The air-cooled unit radiator outlet speed and temperature distribution are more even.