XIE Mingyuan, ZHAO Shun'an

Abstract: Setting up an air duct at the outlet of mechanical draft cooling tower can reduce air dynamic pressure and energy consumption of the fan. In this paper, CFD software FLUENT is used to simulate the air flow in duct, which proves that air flow in duct is a rotating turbulent jet. This study is made on the effects of different height and diffusion angle. Results show that, with the increase of diffusion angle, the air volume and kinetic energy recovery rate increase first and then decrease. The optimal diffusion angle is 18° when height of air duct is 1/2D,and the optimal diffusion angle is 20° when height of air duct is 1/3D. That extends the limits of the design specification where the diffusion angle is not more than 15°. The results of the study can be used for reference when designing and renovating the air duct.

Keywords: air duct; height; diffusion angle; flow field analysis; kinetic energy recovery

(Journal of China Institute of Water Resources and Hydropower Research, Vol. 16, No. 3, 2018)