Research On Flow And Heat Transfer Performance Of Direct Air-cooled Condenser In Power Plant

Because of its property of water-saving, direct air-cooled technology in powerplant has been widely used in northwest China,which has lots of coal but little waterresources. In the thesis，both the flow and heat transfer performance of the single rowtube and the complex flow in the air-cooled condenser unit were studied for an1000MW direct air-cooled power plant.By use of numerical and experimental methods, both the flow and heat transferperformance of the single row finned tube were studied. Fistly, the effects of the headwind velocity value and distribution on the heat transfer performance of the finned tubewere investigated through numerical computation. Under uniform surface velocitydistribution, the heat transfer coefficient of the finned tube increases with the head windvelocity value,but the growth rate gradually slows down. Under the same wind flowrate, two different kinds of velocity distributions，increased and decreased along thesteam flow direction of the finned tube, were analyzed. It is shown that the first kind ofvelocity distribution was not conducive to the finned tube heat exchanger while thesecond kind was.Then, the heat transfer performance of the finned tube was studied with experiment.The experimental heat transfer coefficient with head wind velocity is consistent with thenumerical results. The effects of the above head wind velocity distributions on the heattransfer performance obtained by experimental and numerical methods are alsoconsistent. The dimensionless correlations of the finned tube were developed based onthe experimental data, and the correlations varied for different head wind velocitydistributions.The numerical and experimental results showed that both the head wind velocityvalue and distribution have significant impact on the heat transfer performance of thefinned tube. The velocity distribution decreased along the steam flow in the finned tubeis conducive to the finned tube heat exchanger.In addition, the internal flow field of direct air-cooled condenser unit wasnumerically simulated, and the internal air field distribution of the unit was worked out.Under actual operation, the internal head wind velocity distribution is not conducive tothe tube heat exchanger. So a direct air-cooled unit guiding device was proposed tooptimize the internal flow field. Simulation results showed that the air guiding devicecould adjust the internal flow field of the direct air cooling unit and improve the heat transfer performance of the running direct air-cooled condenser.