Research On Affecting Of Ambient Wind To Heat Transfer Of Direct Air-Cooled Condenser

In northern China, the area of pithead power plant is severe shortage of water resources, especially in the dry season, so the construction of power plants is restricted because of the large amount of water needed. Direct air-cooled technology, which has outstanding water-saving features to solve the bottleneck problem of scarcity of water resources, has been widely used. But the effect of heat transfer of direct air-cooled condenser (DACC) is highly influenced by the external environment. Ambient winds, especially, lead to severe mal-heat transfer of the DACC, and increase back pressure of the direct air-cooled turbine, so that the safety and economy of direct air cooling system(DACS) are affected. The affecting of ambient winds on the DACS is one of the problems to be solved urgently.In this thesis the ambient winds studied include prevailing ambient wind and wind from the boiler. A homemade 1000MW DACC which locates in Ningxia province was geometrically and mathematically modeled. The impact rules of ambient prevailing wind on DACC are studied based on Computational Fluid Mechanics(CFD). Horizontal slabs, windbreak nets, wind guiding baffles and wind guiding nets installed under the DACC platform to improve fan flow rate were studied mathematically. And also the affects of wind from the boiler on the fan flow rate and heat transfer of DACC were studied mathematically.The results show that: the reduction of mass flow, cyclone, hot air recirculation and down-draught phenomenon caused by the prevailing ambient winds are the main factors of affecting heat transfer of DACC; Horizontal slabs installed has leaded to vacuum region at the inlets of upwind fans move forth the DACC, so the fans runtime environment is improved; If a full size windbreak net is installed, the ambient wind move above the air-cooled platform more, reducing wind speed passing through the entrance of fans, the vacuum under the windward air-cooled condenser units will be reduced, so the inlet flowrate increased without affecting on the downstream fans; The presented approach of installing wind guiding nets is a better way to overcome the defects of installing wind guiding baffles, wind guiding nets combines the advantages of wind guiding baffles and windbreak net; the reduction of mass flow and hot air recirculation phenomenon are the two important factors of worsening heat transfer effect of DACS by the wind from the boiler, the installation of full size wind windbreak net all around the direct air-cooled island is an effective measure for increasing the amount of airflow rate.