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The impact of indoor thermal stratification on the dispersion of human speech droplets
Indoor Air ( IF 5.8 ) Pub Date : 2020-09-01 , DOI: 10.1111/ina.12737
Fan Liu 1, 2 , Hua Qian 1, 3 , Zhiwen Luo 2 , Xiaohong Zheng 1, 4
Affiliation  

Exhaled jets from an infected person are found to be locked at a certain height when thermal stratification exists in rooms, causing a potential high risk of disease transmission. This work is focused on the theoretical analysis of the dynamic characteristics of human speech droplets and the residual droplet nuclei in both thermally uniform and stratified environments. Results show that most droplets generated from human speaking can totally evaporate or deposit to the ground within 1.5‐2 m. For small droplets of < 80μm, thermal stratification shows a more significant impact on their residues. The lock‐up height of the droplet nuclei is a function of droplet size and the temperature gradient, and within this lock‐up layer, these droplet nuclei can travel a long distance, much more than 2m. For medium droplets of 80‐180 μm, thermal stratification can weaken the evaporation and accelerate the deposition processes, equivalent to a higher relative humidity (RH). Accordingly, more droplets can deposit to the ground, reducing the exposure to large droplets in close proximity to the source. Large droplets of > 180μm show no dependence on stratification and RH. These findings can have implications for developing effective engineering methods to limit the spread of infectious disease.

中文翻译:

室内热分层对人类语音飞沫扩散的影响

当房间内存在热分层时,发现感染者呼出的喷气被锁定在一定高度,从而导致疾病传播的潜在高风险。这项工作的重点是在热均匀和分层环境中对人类语音液滴和残留液滴核的动态特性进行理论分析。结果表明,大多数人说话产生的飞沫可以在 1.5-2 m 范围内完全蒸发或沉积到地面。对于 < 80μm 的小液滴,热分层对其残留的影响更为显着。液滴核的锁定高度是液滴尺寸和温度梯度的函数,在这个锁定层内,这些液滴核可以行进很长的距离,远超过 2m。对于 80-180 μm 的中等液滴,热分层可以减弱蒸发并加速沉积过程,相当于更高的相对湿度 (RH)。因此,更多的液滴可以沉积在地面上,从而减少对靠近源的大液滴的暴露。> 180μm 的大液滴显示不依赖于分层和 RH。这些发现可能对开发有效的工程方法以限制传染病的传播产生影响。
更新日期:2020-09-01
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