摘要
Abstract
The diffusion layer was applied to model the species transport of air and vapour in the reflux-flow condensation tube equipped on the air cooled condenser, and the VOF approach in multiphase flow was implemented to solve the governing equations, with the mass and momentum source term calculated using Lee model and CSF model respectively. Nine computational cases were accomplished for the two-phase flow in a prototype tube (1000mm length, 5mm width, 50mm altitude, in 60° inclination to horizontal). The numerical results show that, the heat flux through the condensation wall fluctuates at the tube outlet zone, and the influence of the non-condensable gas to the vapour condensation cannot be ignored when inlet mass fraction of the air is more than 1.0%. From the numerical scalar field of species concentration, it is found that the vapour condensation performance deteriorates in prototype tube thanks to the air concentration gradient in the diffusion layer. The transient computed results are shown to effectively capture the observed complex flow characteristics including film dangling, climbing and droplet entrainment, which enhance vapour condensation by destroying the stability and integrity of the diffusion layer. Furthermore, the predicted gas-liquid velocity profiles in these conditions are analyzed. The flow pattern of the condensate film on tube wall is also successfully predicted, which is good agreement with the rivulet flow.关键词
空冷凝汽器/逆流管/扩散层/多相流/凝结/流动/数值模拟Key words
air cooled condenser (ACC)/reflux tube/diffusion layer/multiphase flow/condensation/flow/numerical simulation分类
能源科技
