Experimental Study on Displacement and Mixing Ventilation Systems for a Patient Ward

Yin, Yonggao; Xu, W.; Gupta, Jitendra; Guity, Arash; Marmion, Paul; Manning, Andy; Gulick, Bob; Zhang, Xiaosong; Chen, Qingyan

doi:10.1080/10789669.2009.10390885

Cited by 94 publications

(78 citation statements)

References 19 publications

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“…They indicated that it should be possible to reduce the risk of aerosol transmission by altering the ventilation parameters in healthcare environments. This has been verified by our previous study [5] which showed that ventilation systems play a very important role in the contaminant distribution in an inpatient room. Qian et al [6] indicated that the downward laminar airflow pattern recommended by the CDC was impossible to achieve due to turbulent flow mixing and thermal buoyancy.…”

Section: Introductionsupporting

confidence: 79%

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Distributions of respiratory contaminants from a patient with different postures and exhaling modes in a single-bed inpatient room

Yin

Gupta

Zhang

et al. 2011

Building and Environment

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a b s t r a c tThis study investigated contaminant transport and evaluated the ventilation performance in a single-bed inpatient room. The study performed comparative experimental analysis on the distributions of respiratory contaminants breathed out and coughed out by a patient in a full-scale chamber, which simulated a single-bed inpatient room. The contaminant exhaled by the patient was simulated by an SF 6 tracer gas and 3-mm particles at steady-state conditions. The differences in the contaminant distribution between the coughing and breathing cases were insignificant for the mixing ventilation case, while for the displacement ventilation, the contaminant concentrations in the upper part of the room were higher for the coughing case. The contaminant concentrations in the inpatient room for the case with the patient sitting on the bed were lower than those for the patient supine on the bed for the displacement ventilation under the same supply airflow rate. The SF 6 tracer gas and 3-mm particles released at a notable initial velocity for simulating a cough could give similar contaminant distributions in the inpatient room. Therefore, the experimental data can be used to validate a CFD model, and the validated CFD model can be used to investigate transient coughing and breathing processes.

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Section: Introductionsupporting

confidence: 79%

“…Our previous study [5] concluded that the tracer gas and 3-mm particles can be used to simulate contaminant release from a patient if the release is at a negligible velocity. This type of release includes breathing and talking.…”

Section: Simulation Of Contaminant By Tracer Gas and Particles Due Tomentioning

confidence: 99%

Distributions of respiratory contaminants from a patient with different postures and exhaling modes in a single-bed inpatient room

Yin

Gupta

Zhang

et al. 2011

Building and Environment

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“…It should be highlighted that the influence of boundary conditions could be comparable to that of the air distribution methods. In addition, the relative importance of the 2 functions of DV, namely diluting pollutants vertically and increasing pollutants dispersion horizontally, may change with distance and vertical location of the exhaust opening . It is therefore important to clarify the exact boundary conditions when interpreting a specific finding.…”

Section: Current Understanding Of Airborne Transmission Indoorsmentioning

confidence: 99%

Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review

2018

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This article reviews past studies of airborne transmission between occupants in indoor environments, focusing on the spread of expiratory droplet nuclei from mouth/nose to mouth/nose for non-specific diseases. Special attention is paid to summarizing what is known about the influential factors, the inappropriate simplifications of the thermofluid boundary conditions of thermal manikins, the challenges facing the available experimental techniques, and the limitations of available evaluation methods. Secondary issues are highlighted, and some new ways to improve our understanding of airborne transmission indoors are provided. The characteristics of airborne spread of expiratory droplet nuclei between occupants, which are influenced correlatively by both environmental and personal factors, were widely revealed under steady-state conditions. Owing to the different boundary conditions used, some inconsistent findings on specific influential factors have been published. The available instrumentation was too slow to provide accurate concentration profiles for time-dependent evaluations of events with obvious time characteristics, while computational fluid dynamics (CFD) studies were mainly performed in the framework of inherently steady Reynolds-averaged Navier-Stokes modeling. Future research needs in 3 areas are identified: the importance of the direction of indoor airflow patterns, the dynamics of airborne transmission, and the application of CFD simulations.

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“…Well-mixed ventilation (WMV) is common for commercial buildings and residences where the air conditioning system operates. BDV and WMV are two widely utilized schemes and are also wellstudied in previous literature (Yin et al 2009;Lai and Wong 2010). Therefore, these two ventilation schemes were applied in the experimentation.…”

Section: Experimental Apparatus and Measurementsmentioning

confidence: 99%

Lagrangian particle modeling in the indoor environment: A comparison of RANS and LES turbulence methods (RP-1512)

Liu

Novoselac

2014

HVAC&R Research

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Indoor particulate contaminants can be generated in many ways, commonly from human activities, infiltration of HVAC systems, or resuspension from indoor surfaces. Most of these sources are transient and generate nonuniform particle distribution in the space. This study used experimental and numerical methods to investigate the dispersion of three different particle sizes (0.7, 2.5, and 7 μm) emitted from typical source positions. A test room and simplified thermal manikins were employed to mimic a realistic indoor environment, and experimental data were compared with particle modeling using the Lagrangian method coupled with Reynolds averaged NavierStokes (RANS) and large eddy simulation (LES) computational fluid dynamics (CFD) turbulence models. Particle dispersion was studied for two ventilation patterns: buoyancy-driven ventilation and well-mixed ventilation. The results provided a comparison of Lagrangian-RANS particle modeling, Lagrangian-LES particle modeling, and experimental data considering nonuniform temporal and spatial particle concentrations. Experimental and modeling results were evaluated with three different metrics: peak normalized concentration at various locations, peak-concentration occurrence time, and mean exposure defined as the averaged concentration in the occupant's breathing zone. The results show that Lagrangian-LES more accurately predicts concentration fluctuation during particle emission. Considering long-term exposure, however, both methods show similar results.

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Experimental Study on Displacement and Mixing Ventilation Systems for a Patient Ward

Abstract: In hospital patient wards, exhalation flow from a patient with airborne infectious diseases

Cited by 94 publications

References 19 publications

Distributions of respiratory contaminants from a patient with different postures and exhaling modes in a single-bed inpatient room

Distributions of respiratory contaminants from a patient with different postures and exhaling modes in a single-bed inpatient room

Airborne spread of expiratory droplet nuclei between the occupants of indoor environments: A review

Lagrangian particle modeling in the indoor environment: A comparison of RANS and LES turbulence methods (RP-1512)

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