Numerical Research On Flow Field Optimization Of Air-cooled Condenser Unit

Large capacity and high parameter in thermal power plant steam turbine unit continues to increase in our courmtry. At the same time these plants not only cost much more coal but also consume large amounts of water. Using air-cooling technology is the key to solve the water shortage in northern China coal-rich region.In the past10years, domestic and foreign scholars have done much research on air cooling unit. The cold end of direct air-cooling unit, air condenser is a key factor to the thermal efficiency of the air cooling units. For the air cooling condenser arrangement in the natural wind field, therefore directly affected by environmental wind field. Natural wind speed, wind direction and flow field distribution play decisive role in the normal and stable operation of air cooling unit. According to the present direct air-cooling system, environment of the adverse impact of horizontal wind is one of the outstanding problems which need to be solved.Numerical analysis method is applied in this article, with a list of air cooling island unit as the research object, studies air flow and heat transfer characteristics of finned tube bundle of the unit before and after with guiding device.(1) In the environment under no wind, analyses the air flow field changes and heat transfer characteristics of the column before and after the optimization of each unit.Get inlet and outlet air velocity and temperature distribution of the finned tube bundle on the first unit as well as air mass flow rate through the various units and the changing rule of the heat load.(2) According to the fan flow rate and total heat transfer of finned tube bundle of each unit, the research content include:the air flow characteristics inside the units is analyzed under9,21m/s wind speed; the9m/s at1,8units and21m/s at1,2,4,8units finned tube bundle inlet and outlet air velocity and temperature distribution. Results show that the ambient wind had great influence on the upstream flow field of air cooling unit, fan can not work normally,so the thermal performance is lower than those of the downstream unit.After air cooling unit diversion transformation of flow field in optimizing the organization at9m/s, the cooling air flow rate in downstream unit increased, heat transfer ability of the condenser is higher than that of without leading device. (3) Compared the import and export of velocity and temperature distribution at the bottom of the finned tube bundle under environmental wind speed for3,6,9,12,15,18,21m/s. The result shows:fan flow rate of the first five units is low, heat transfer ability is poor at the bottom of the finned tube bundle. From the6th to the8th unit, fan flow rate increases gradually, speeds up the unit inside and outside air flow, the bottom of the tube bundle of heat transfer capability is greatly increased. At9m/s, finned tube bundle heat transfer ability is the lowest. After the installation guide plate, the internal air flow is accelerated, the heat transfer ability at the bottom of finned tube bundle also strengthened, internal and external velocity and temperature field tends to be more uniform.