Numerical investigation of particle transport and inhalation using standing thermal manikins

Li, Xiangdong; Inthavong, Kiao; Ge, Qinjiang; Tu, Jiyuan

doi:10.1016/j.buildenv.2012.11.014

Cited by 39 publications

(16 citation statements)

References 19 publications

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“…Dygert et al (2009) indicated that the strength of the thermal plume is relatively insensitive to the temperature distribution on the human body surface, as long as the area-weighted average temperature on the human body surface is the same. Existing human simulation usually assigned a uniform temperature to the body surface in numerical simulation, and the body surface temperature ranged from 28℃ to 33.7℃ (Murakami et al 1999;Jakie et al 2010;Zhang et al 2011;Salmanzadeh et al 2012;Li et al 2013). Jackie et al (2010) calculated the intake fraction (iF) in the indoor environment when the body surface was fixed at 32℃ and 28℃ and found that a 4℃ change in body surface temperature influenced the intake fraction by less than 10%.…”

Section: Investigated Scenariosmentioning

confidence: 99%

The ventilation needed to control thermal plume and particle dispersion from manikins in a unidirectional ventilated protective isolation room

Yang

Zhao

2015

Build. Simul.

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Infection is a major cause of death for the immunocompromised patients whose immune mechanisms are deficient. The most effective way of protecting these patients is the total environment protection such as protective isolation room (PIR). Unidirectional airflow ventilation is usually used in PIR. The supply air velocity in PIR can affect not only the cleanliness level of the room and total environment protection effects to the patients, but also the energy consumption and initial equipment investment of the room. Computational fluid dynamics (CFD) program is used to simulate the airflow field and the concentration distribution of the particles from human body and breathing. Three scenarios when the manikin is standing, sitting and lying are investigated in this study. The intensities of supply airflow with different velocities and the upward airflow induced by thermal plume with different postures are compared. The qualitative and quantitative analysis of the simulation results show that the required supply air velocity to control the thermal plume and particle dispersion from human body and breathing is at least 0.25 m/s when the manikin is standing or sitting, and 0.2 m/s when the manikin is lying. Keywordsunidirectional airflow ventilation, computational fluid dynamics (CFD), air distribution, protective isolation Article History

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Section: Investigated Scenariosmentioning

confidence: 99%

The ventilation needed to control thermal plume and particle dispersion from manikins in a unidirectional ventilated protective isolation room

Yang

Zhao

2015

Build. Simul.

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“…This interaction would not only change the local airflow distribution in the vicinity of the human body, but certainly affect the local evaporation factors (air pressure, temperature and etc.). It was proved by the previous studies that even small changes of the local airflow would cause very different transport trajectories of the particles and droplets [7,20]. Most importantly, since the ascending thermal plume was capable of carrying contaminants from the near-floor level into the breathing zone [22], the inhalability and infection risks could be significantly enlarged after considering the human body thermal effect.…”

Section: Introductionmentioning

confidence: 99%

“…When individual coughs, the size of the expelled droplets could be diversely ranged from 0.1 μm to 1000 μm [4][5][6], which is wide enough to cause both viral and bacterial infections [5]. Also, such a wide size range implies that the transport and dispersion of the droplets could be completely different [7] after expelling through the same cough. Unlike the large droplets that would quickly deposit to the floor due to high inertia and mass, small droplets would be easily carried by the local airflow and tend to suspend in the air for longer time.…”

Section: Introductionmentioning

confidence: 99%

Thermal effect of human body on cough droplets evaporation and dispersion in an enclosed space

Yan

2019

Building and Environment

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A B S T R A C TThis study numerically investigated the thermal effect of human body on the time-dependent dispersion of cough droplets with evaporation process. The thermal flow of human body was imitated using a 3D thermal manikin with real body features, while a recent developed multi-component Eulerian-Lagrangian approach was used to address the effects of inhomogeneous temperature and humidity fields on droplet evaporation. By comparing the results yielded without and with the human body heat, the outcomes demonstrated strong impact of human body heat on the droplets mass fraction and local air velocity distributions. Inspirable droplets could potentially drop into respirable droplets by evaporation, although the evaporation rate was not significantly affected by body heat. The thermal effect of human body revealed its vital impacts on the time-dependent droplets dispersion. Due to the buoyancy driven thermal flow, both the vertical velocity and displacement of small droplets (≤20 μm) were completely reversed from descending to ascending, while the deposition time of large droplets (≥50 μm) were significantly delayed. With the reduced droplet size by evaporation and droplets lifted into breathing zone by human thermal effect, the inhalability and infection risks of cough droplets would be much higher in real occupied indoor spaces.

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“…A common estimation of the droplet density and initial concentration of non-volatile compounds is ρ nv = 1000 kg/m 3 and C nv = 1.8% [8], which results in an equilibrium diameter of d d,e = 0.262d d,0 . This means that as water evaporates, some free-falling large droplets could become airborne [10], leading to an elevated number density of inhalable droplets in the breathing zone and an increased probability of infection [11,12].…”

Section: Introductionmentioning

confidence: 99%

Modelling of evaporation of cough droplets in inhomogeneous humidity fields using the multi-component Eulerian-Lagrangian approach

Shang

Yan

et al. 2018

Building and Environment

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124

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A B S T R A C TThis study employed a multi-component Eulerian-Lagrangian approach to model the evaporation and dispersion of cough droplets in quiescent air. The approach is featured with a continuity equation being explicitly solved for water vapor, which allows comprehensively considering the effects of inhomogeneous humidity field on droplets evaporation and movement. The computational fluid dynamics (CFD) computations based on the approach achieved a satisfactory agreement with the theoretical models reported in the literature. The results demonstrated that the evaporation-generated vapor and super-saturated wet air exhaled from the respiratory tracks forms a "vapor plume" in front of the respiratory track opening, which, despite the short life time, significantly impedes the evaporation of the droplets captured in it. The study also revealed that due to the droplet size reduction induced by evaporation, both the number density of airborne droplets and mass concentration of inhalable pathogens remarkably increased, which can result in a higher risk of infection. Parametric studies were finally conducted to evaluate the factors affecting droplet evaporation. Summary: The study demonstrated the importance of considering inhomogeneous humidity field when modelling the evaporation and dispersion of cough droplets. The multi-component Eulerian-Lagrangian model presented in this study provides a comprehensive approach to address different influential factors in a wide parametric range, which will enhance the assessment of the health risks associated with droplet exposure.

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Numerical investigation of particle transport and inhalation using standing thermal manikins

Cited by 39 publications

References 19 publications

The ventilation needed to control thermal plume and particle dispersion from manikins in a unidirectional ventilated protective isolation room

The ventilation needed to control thermal plume and particle dispersion from manikins in a unidirectional ventilated protective isolation room

Thermal effect of human body on cough droplets evaporation and dispersion in an enclosed space

Modelling of evaporation of cough droplets in inhomogeneous humidity fields using the multi-component Eulerian-Lagrangian approach

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