AI Chat Paper
Note: Please note that the following content is generated by AMiner AI. SciOpen does not take any responsibility related to this content.
{{lang === 'zh_CN' ? '文章概述' : 'Summary'}}
{{lang === 'en_US' ? '中' : 'Eng'}}
Chat more with AI
Powered by AMiner. Clicking this button will take you away from SciOpen.
Home Building Simulation Article
Article Link
Cite
EndNote(RIS) BibTeX
Collect
Submit Manuscript
Show Outline
Outline
Show full outline
Hide outline
Outline
Show full outline
Hide outline
Research Article

Numerical study of the lock-up phenomenon of human exhaled droplets under a displacement ventilated room

Naiping Gao1( ), Qibin He2, Jianlei Niu3
Institute of Refrigeration and Thermal Engineering, School of Mechanical Engineering, Tongji University, 1239# Siping Road, Shanghai, China
Shenzhen Institute of Building Research, 29#, three Road, Meiao, Shangmeilin, Shenzhen, China
Department of Building Services Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China
Show Author Information

Abstract

This paper adopts an Eulerian-Lagrangian approach to investigate the lock-up phenomenon (or trap phenomenon) of human exhaled droplets in a typical office room under displacement ventilation (DV). A particle-source-in-cell (PSI-C) scheme is used to correlate the concentration with the Lagrangian particle trajectories in computational cells. Respiratory droplets with sizes of 0.8 μm, 5 μm and 16 μm are released from a numerical thermal manikin (NTM). The influence factors including indoor temperature gradient, heat source configuration and exhalation modes are studied. It is found that large temperature gradient would result in trap phenomenon of small exhaled droplets (smaller than 5 μm). The intensive heat source near the NTM could help to transport the small droplets to the upper zone and decrease the concentration level in the trapped zone. Both nose-exhaled and mouth-exhaled small droplets would be trapped at the breathing height when temperature gradient is sufficiently high. However, the trap height of the droplets from mouth is a little bit higher. Because of large gravitational force, it is difficult for the thermal plume to carry 16 µm respiratory droplets to the upper zone.

Keywords

thermal plumedisplacement ventilationhuman exhaled dropletstrap phenomenonLagrangian simulation

References

 
E Bjorn, PV Nielsen (2002). Dispersal of exhaled air and personal exposure in displacement ventilated rooms. Indoor Air, 12: 147-164.
Crossref Google Scholar
 
H Brohus, PV Nielsen (1996). Personal exposure in displacement ventilated rooms. Indoor Air, 6: 157-167.
Crossref Google Scholar
 
C Chen, B Zhao (2010). Some questions on dispersion of human exhaled droplets in ventilation room: answers from numerical investigations. Indoor Air, 20: 95-111.
Crossref Google Scholar
 
CYH Chao, MP Wan (2006). A study of the dispersion of expiratory aerosols in unidirectional downward and ceiling-return type airflows using a multiphase approach. Indoor Air, 16: 296-312.
Crossref Google Scholar
 
CYH Chao, MP Wan, L Morawska, GR Johnson, ZD Ristovski, M Hargreanes, K Mengersen, S Corbett, Y Li, X Xie, D Katoshevski (2009). Characterization of expiration air jets and droplet size distributions immediately at the mouth opening. Journal of Aerosol Science, 40: 122-133.
Crossref Google Scholar
 
CYH Chao, MP Wan, GNS To (2008). Transport and removal of expiratory droplets in hospital ward environment. Aerosol Science and Technology, 42: 377-394.
Crossref Google Scholar
 
B Friberg, S Friberg, LG Burman, R Lundholm, R Ostensson (1996). Inefficiency of upward displacement operating theatre ventilation. Journal of Hospital Infection, 33: 263-272.
Crossref Google Scholar
 
N Gao, J Niu, L Morawska (2008). Distribution of respiratory droplets in enclosed environments under different air distribution methods. Building Simulation, 1: 326-335.
Crossref Google Scholar
 
NP Gao, JL Niu, M Perino, P Heiselberg (2009). The airborne transmission of infection between flats in high-rise residential buildings: Particle simulation. Building and Environment, 44: 402-410.
Crossref Google Scholar
 
PY Hamey (1982). The evaporation of airborne droplets. Msc Thesis, Bedford-shire, UK, Granfield Institute of Technology, 48-58.
 
K Han, XP Zhu, F He, LG Liu, LJ Zhang, HL Ma, XY Tang, T Huang, G Zeng, BP Zhu (2009). Lack of Airborne Transmission during Outbreak of Pandemic (H1N1) 2009 among Tour Group Members, China, June 2009. Emerging Infectious Diseases, 15: 1578-1581.
Crossref Google Scholar
 
Q He, J Niu, N Gao, T Zhu, J Wu (2011). CFD study of exhaled droplet transmission between occupants under different ventilation strategies in a typical office room. Building and Environment, 46: 397-408.
Crossref Google Scholar
 
Y Li, PV Nielsen, M Sandberg (2011). Displacement ventilation in hospital environments. ASHRAE Journal, 53: 86-88.
Google Scholar
 
A Mangili, MA Gendreau (2005). Transmission of infectious diseases during commercial air travel. Lancet, 365: 989-996.
Crossref Google Scholar
 
L Morawska, GR Johnson, ZD Ristovski, M Hargreaves, K Mengersen, S Corbett, CYH Chao, Y Li, D Katoshevski (2009). Size distribution and sites of origin of droplets expelled from the human respiratory tract during expiratory activities. Journal of Aerosol Science, 40: 256-269.
Crossref Google Scholar
 
E Mundt (1995). Displacement ventilation systems—Convection flows and temperature gradients. Building and Environment, 30: 129-133.
Crossref Google Scholar
 
KW Mui, LT Wong, CL Wu, ACK Lai (2009). Numerical modeling of exhaled droplets nuclei dispersion and mixing in indoor environments. Journal of Hazardous Materials, 167: 736-744.
Crossref Google Scholar
 
S Murakami, S Kato, S Nagano, S Tanaka (1992). Diffusion characteristics of airborne particles with gravitational settling in a convection-dominant indoor flow field. ASHRAE Transaction, 98(1): 82-97.
Google Scholar
 
M Nicas, WW Nazaroff, A Hubbard (2005). Toward understanding the risk of secondary airborne infection: Emission of respirable pathogens. Journal of Occupational and Environmental Hygiene, 2: 143-154.
Crossref Google Scholar
 
PV Nielsen, I Olmedo, MR Adana, P Grzelecki, RL Jensen (2012). Airborne cross-infection risk between two people standing in surroundings with a vertical temperature gradient. HVAC & R Research, in press. DOI: .
Crossref Google Scholar
 
H Qian, Y Li, P Nielsen, C Hyldgaard, T Wong, A Chwang (2006). Dispersion of exhaled droplet nuclei in a two-bed hospital ward with three different ventilation systems. Indoor Air, 16: 111-128.
Crossref Google Scholar
 
S Seepana, ACK Lai (2012). Experimental and numerical investigation of interpersonal exposure of sneezing in a full-scale chamber. Aerosol Science and Technology, 46: 485-493.
Crossref Google Scholar
 
H Skistad, E Mundt, PV Nielsen, K Hagstrom, J Railio (2004). Displace-ment ventilation in non-industrial premises. Brussels: Rehva.
 
BG Wagner, BJ Coburn, S Blower (2009). Calculating the potential for within-flight transmission of influenza A (H1N1). BMC Medicine, 7: 81.
Crossref Google Scholar
 
MP Wan, CYH Chao (2007). Transport characteristics of expiratory droplets and droplets nuclei in indoor environments with different ventilation airflow patterns. Journal of Biomechanical Engineering, 129: 341-353.
Crossref Google Scholar
 
Z Zhang, Q Chen (2006). Experimental measurements and numerical simulations of particle transport and distribution in ventilated rooms. Atmospheric Environment, 40: 3396-3408.
Crossref Google Scholar
 
B Zhao, Y Zhang, X Li, X Yang, D Huang (2004). Comparison of indoor aerosol particle concentration and deposition in different ventilated rooms by numerical method. Building and Environment, 39: 1-8.
Crossref Google Scholar
Building Simulation
Volume 5 Issue 1,
March 2012
Pages 51-60
DOI: 10.1007/s12273-012-0068-5
Cite this article:
Gao N, He Q, Niu J. Numerical study of the lock-up phenomenon of human exhaled droplets under a displacement ventilated room. Building Simulation, 2012, 5(1): 51-60. https://doi.org/10.1007/s12273-012-0068-5

876

Views

38

Crossref

N/A

Web of Science

40

Scopus

0

CSCD

Altmetrics
Received: 12 December 2011
Revised: 15 January 2012
Accepted: 02 February 2012
Published: 14 March 2012
© Tsinghua University Press and Springer-Verlag Berlin Heidelberg 2012
Return