TR-PIV measurement of exhaled flow using a breathing thermal manikin

Li, Feng; Yao, Susu; Sun, Hejiang; Jiang, Nan; Liu, Junjie

doi:10.1016/j.buildenv.2015.11.001

Cited by 28 publications

(26 citation statements)

References 37 publications

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“…PIV measurement uncertainties are influenced by various error sources, which can be either systematic or statistical errors . Statistical errors are mainly due to random sampling, while systematic errors relate to the experimental setup and procedure with likely sources of error originating from tracking behavior, seeding density, background noise, etc. Indoor airflow measurements with 2‐dimensional PIV have systematic errors less than 2% …”

Section: Methodsmentioning

confidence: 99%

Entrainment and its implications on microclimate ventilation systems: Scaling the velocity and temperature field of a round free jet

Kabanshi

Sandberg

2019

Indoor Air

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Research on microclimate ventilation systems, which mostly involve free jets, points to delivery of better ventilation in breathing zones. While the literature is comprehensive, the influence of contaminant entrainment in jet flows and its implications on the delivery of supplied air is not fully addressed. This paper presents and discusses entrainment characteristics of a jet issued from a round nozzle (0.05 m diameter), in relation to ventilation, by exploring the velocity and temperature fields of the jet flow. The results show a trend suggesting that increasing the Reynold number (Re) reduces ambient entrainment. As shown herein, about 30% concentration of ambient air entrained into the bulk jet flow at Re 2541 while Re 9233 had about 13% and 19% for Re = 6537/12 026 at downstream distance of 8 diameters (40 cm). The study discusses that “moderate to high” Re may be ideal to reduce contaminant entrainment, but this is limited by delivery distance and possibly the risk of occupant discomfort. Incorporating the entrainment mixing factor (the ratio of room contaminants entrained into a jet flow) in performance measurements is proposed, and further studies are recommended to verify results herein and test whether this is general to other nozzle configurations.

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Section: Methodsmentioning

confidence: 99%

Entrainment and its implications on microclimate ventilation systems: Scaling the velocity and temperature field of a round free jet

Kabanshi

Sandberg

2019

Indoor Air

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“…The flow techniques used were particle image velocimetry (PIV), smoke particles visualization, and a Schlieren imaging technique. PIV is a commonly used technique for visualizing the instantaneous velocity field on a relevant plane across a breathing zone . The speed and direction of the target velocity field can be calculated accurately from the imaged seeding particles.…”

Section: Experimental and Cfd Techniquesmentioning

confidence: 99%

“…PIV is a commonly used technique for visualizing the instantaneous velocity field on a relevant plane across a breathing zone. 59,[68][69][70]102,[175][176][177][178] The speed and direction of the target velocity field can be calculated…”

Section: Flow Techniquesmentioning

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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“…Jet influence area is determined by normalizing all velocities ( u / u z ) at a distance of mouth plane using centerline velocity ( u cz ). The limit of the jet diffusion area is usually considered at u / u cz =0.05 . The results are shown in Figure .…”

Section: Resultsmentioning

confidence: 99%

“…Because exhalation flow is a transient process and turbulence is expected, a phase‐averaged approximation to the study of velocity fields is selected. This method has already been used in different breathing studies . Fifty exhalation processes (N=50) have been captured for test M and test F .…”

Section: Methodsmentioning

confidence: 99%

Experimental analysis of the air velocity and contaminant dispersion of human exhalation flows

2016

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Human exhalation flow is a potential source of pathogens that can constitute a cross-infection risk to people in indoor environments. Thus, it is important to investigate the characteristics of this flow, its development, area of influence, and the diffusion of the exhaled contaminants. This paper uses phase-averaged particle image velocimetry together with a tracer gas (CO ) to study two different exhalation flows over time: the exhalation of an average male (test M) and an average female (test F), using a life-sized thermal manikin in a supine position. The exhalation jets generated for both tests are similar in terms of symmetrical geometry, vorticity values, jet opening angles, and velocity and concentration decays. However, there is a difference in the penetration length of the two flows throughout the whole exhalation process. There is also a time difference in reaching maximum velocity between the two tests. It is also possible to see that the tracer gas dispersion depends on the momentum of the jet so the test with the highest velocity decay shows the lowest concentration decay. All these results are of interest to better understand cross-infection risk.

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TR-PIV measurement of exhaled flow using a breathing thermal manikin

Cited by 28 publications

References 37 publications

Entrainment and its implications on microclimate ventilation systems: Scaling the velocity and temperature field of a round free jet

Entrainment and its implications on microclimate ventilation systems: Scaling the velocity and temperature field of a round free jet

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

Experimental analysis of the air velocity and contaminant dispersion of human exhalation flows

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