Study On Improvement Of Structure And Arrangement Of New Type Air-cooled Unit And The Related Heat Transfer Characteristics

Due to growing power demand of China and the contradiction between poor water and plentiful coals in North China,the direct air-cooled unit has developed rapidly,which benefits people enormously.Although the "?" shaped structure of direct air-cooled unit is widely used,its operation process has many deficiencies.Based on the previous researches,this paper proposes a new type air-cooled unit and layout improvements for promoting the structure of air-cooled island to achieve the increase and utilization of air flow furthest for enhancing its heat transfer characteristics and improving the overall economic efficiency of the power plant.Those have important practical significance for improving traditional direct air cooling technology.The aim of this paper is to solve the heat transfer problems of air-cooled unit,to ensure the safety and long-term operation of the air cooled condenser unit.Firstly,taking the 600 MW unit of Long-shan power plant and frustum cone-like air-cooled unit as the comparative object,according to the principle of bladeless fan,a new type air-cooled unit which sets the induced air ring at the lower part of the cooling wall and supplies air from the fan side is proposed.The Fluent software is carried out to analyze the effect of the slit width of the outlet and the inclination on heat transfer characteristics of the new type air-cooled unit,determine the optimal width and inclination,and obtain a better structure for the new type air-cooled unit.Secondly,on the basis of the new type air-cooled unit,a groove and a convex groove deflector are added inside the air-cooled unit for reducing air backflow to ensure the maximum efficiency of air utilization.The deflector structure with the best heat transfer effect is obtained by analyzing temperature distribution and streamlined diagram.Thirdly,the layout of the new air-cooled unit is improved,the disperse air supply of air cooling island is changed to centralized air supply,a fan which worked for two or three air-cooled units were simulated at the same time.Finally,the heat transfer characteristics and economical efficiency of air-cooled units under different layouts were compared and analyzed,and obtain the most conducive to heat transfer effect and the most economical system of the optimized direct air-cooled unit and layout improvements.These improvements provide an important reference for advancing traditional direct air-cooled technology.