Modeling deposition of particles in typical horizontal ventilation duct flows
Modeling deposition of particles in typical horizontal ventilation duct flows
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DOI：
10.1016/j.enconman.2008.06.035
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发表时间：
2008-12
影响因子：
10.4
通讯作者：
Jinping Zhang;Angui Li;Desheng Li
中科院分区：
文献类型：
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作者：
Jinping Zhang;Angui Li;Desheng Li
在供暖、通风和空调（HVAC）系统中，气流通过通风管道携带的颗粒对人体健康有不利影响。了解通风管道中的颗粒沉积速率有助于模拟建筑物内颗粒的暴露情况，并更全面地了解颗粒的命运。为了实现这些目标，在3.0m/s、7.0m/s和9.0m/s三种空气速度下，通过雷诺平均纳维-斯托克斯(RANS)-拉格朗日模拟，预测了颗粒在光滑水平方形通风管道中不同内表面的沉积速率。在粒子运动的计算中考虑了阻力、升力、重力、惯性力和湍流扩散。讨论了弛豫时间、颗粒大小、空气速度、湍流发展曲线和表面方向对预测颗粒沉积速率（无量纲沉积速度）的影响。结果表明：对于大于10μm的颗粒，3种不同风速下，光滑水平方形通风管内的垂直壁面沉积速率均随无量纲弛豫时间的增加而增加，随无量纲弛豫时间的增加而略有下降；侧壁沉积速率最大值为0.12。随着无量纲松弛时间的增加，底板沉积速率增大，达到最大值9.6。在不同风速下，随着无因次松弛时间的增加，顶板沉积速率先逐渐减小后迅速减小至零。上限沉积速率最大值为0.054。在紊流型发展充分的水平风管中，颗粒在顶板、壁面和底板的沉积速率均低于紊流型发展的水平风管。颗粒沉积速率主要取决于摩擦速度（空气速度）和颗粒大小。随着风速的增加，风道地板、壁面和顶板沉积速率的差异减小。拉格朗日模拟的结果对于更准确地预测和理解典型通风管道中的颗粒沉积具有重要价值。
Particles carried by airflows through ventilation ducts in heating, ventilation and air-conditioning (HVAC) systems have adverse effects on human health. Knowledge of particle deposition rates in ventilation ducts is useful for modeling exposures to particles within buildings and more completely understanding particle fates. To meet these objectives, deposition rates of particles to various internal surfaces in a smooth horizontal square ventilation duct are predicted by Reynolds-Averaged Navier-Stokes (RANS)-Lagrangian simulation at all three air speeds of 3.0m/s, 7.0m/s and 9.0m/s. Drag, lift force, gravity, inertial force and turbulent diffusions are considered in the computation of particle motion. The influences of relaxation time, particle size, air speed, turbulent flow development profiles and surface orientations on predicted deposition rates (dimensionless deposition velocities) of particles is discussed. For particles larger than 10μm, it is shown that vertical wall deposition rates in a smooth horizontal square ventilation duct where the turbulent flow profiles is fully developed first increase with dimensionless relaxation time increase and then slightly decrease with dimensionless relaxation time increasing at three different air speeds. The maximum of the sidewall deposition rates is 0.12. Floor deposition rates increase with dimensionless relaxing time increase and attain the maximum value of 9.6. Ceiling deposition rates firstly gradually decrease and then rapidly decrease to zero with dimensionless relaxing time increasing at different air speeds. The maximum of the ceiling deposition rates is 0.054. Particle deposition rates to the ceiling, wall and floor in the horizontal duct with a fully developed turbulent flow profile are all lower than that in the horizontal duct with a developing turbulent flow profile. Particle deposition rates are mainly dependent on friction velocity (air speed) and particle size. The differences in deposition rates to the duct floor, wall and ceiling decrease with increasing air speed. The results of Lagrangian simulations in this work are valuable for more accurately predicting and understanding particle deposition in typical ventilation ducts.