空气稳定性对室内人体持续与间歇呼气的影响

空气稳定性概念来源于大气稳定性,在室内环境下反映室内空气的稳定程度.本文利用暖体假人实验,研究了室内空气稳定性对呼气扩散规律的作用.分别针对无通风、混合通风及置换通风3种方式,以及间歇与持续呼气两种形式,组合后形成7组对照实验.通过烟气实验及热球风速仪测量对呼气轨迹进行了可视化及速度测量.结果表明,稳定和中性两种室内空气状态下人体呼气的扩散规律不同.不论是持续射流还是间歇的呼气过程,空气稳定性对其扩散影响显著,影响其轨迹弯曲程度及速度衰减.同时,间歇呼气较持续射流湍流发展更充分,污染物与周围空气迅速掺混,且呼气气流更加平坦.此外,即使两种状态下的Ar与体表温度都接近,由于向上运动受到抑制,稳定的空气相对中性状态下呼出的气流更水平,而且由于气流与周围空气掺混能力减弱,速度衰减低于中性状态.

Effect of Air Stability on the Continuous and Periodic Exhalation Flow of a Person

The concept of air stability is derived from atmospheric stability, which represents the extent of stability of room air.Experiments on thermal manikin were performed to investigate the effect of air stability on the dispersion of exhaled flow.Seven cases with the combination of three ventilation patterns (no ventilation, mixing ventilation and displacement ventilation) and two breathing modes (continuous and periodic) were applied.The trajectory of exhaled flow was visualized and measured by smoke visualization and velocity measurement, respectively.The results show that both the continuous and periodic exhalation are significantly affected by the air stability with respect to the trajectory and velocity decay.Meanwhile, the turbulence highly develops in the periodic flow, making the contaminant mix well with the ambient air and the flow flatter in comparison with continuous jet.As the stable condition restrains the upward movement of the flow, it becomes flatter under stable condition compared with neutral condition even though they have similar Ar and body plume.In addition, the velocity decay is smaller for stable condition because it entrains less ambient air.