The impact of indoor thermal stratification on the dispersion of human speech droplets

Liu, F., Qian, H., Luo, Z. ORCID: https://orcid.org/0000-0002-2082-3958 and Zheng, X. (2021) The impact of indoor thermal stratification on the dispersion of human speech droplets. Indoor Air, 31 (2). pp. 369-382. ISSN 1600-0668 doi: 10.1111/ina.12737

Abstract/Summary

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 1.5-2m. 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 80-180μm, 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.

Item Type	Article
URI	https://reading-clone.eprints-hosting.org/id/eprint/92001
Identification Number/DOI	10.1111/ina.12737
Refereed	Yes
Divisions	Interdisciplinary Research Centres (IDRCs) > Walker Institute Science > School of the Built Environment > Urban Living group Science > School of the Built Environment > Energy and Environmental Engineering group
Publisher	Wiley
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