Effect of supply velocity and heat generation density on cooling and ventilation effectiveness in room with impinging jet ventilation system

Yamasawa, Haruna; Kobayashi, Tomohiro; Yamanaka, Tatsuhiko; Choi, Narae; Cehlin, Mathias; Ameen, Arman

doi:10.1016/j.buildenv.2021.108299

Cited by 31 publications

(13 citation statements)

References 34 publications

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“…The binary mass diffusion coefficient is determined by the Fuller correlation [ 44 , 45 ]. The flow turbulence is modeled via the shear stress transport (SST) k - ω model [ 46 ]. The governing equation for the mean age of air (MAA) [ 47 ] is:

where τ is MAA in second, μ eff is the effective viscosity, and Sc t is the turbulent Schmidt number, 0.7 [ 48 ].…”

Section: Models and Methodsmentioning

confidence: 99%

Transmission mitigation of COVID-19: Exhaled contaminants removal and energy saving in densely occupied space by impinging jet ventilation

Qin

Zhang

et al. 2023

Building and Environment

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where τ is MAA in second, μ eff is the effective viscosity, and Sc t is the turbulent Schmidt number, 0.7 [ 48 ].…”

Section: Models and Methodsmentioning

confidence: 99%

Transmission mitigation of COVID-19: Exhaled contaminants removal and energy saving in densely occupied space by impinging jet ventilation

Qin

Zhang

et al. 2023

Building and Environment

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“…One of the room setups in the numerical investigation by Yamasawa et al 29 . was chosen, as shown in Figure 2.…”

Section: Methodsmentioning

confidence: 99%

“…Further details are provided in Section 4.1. The latter is based on the room setup in a previous study by Yamasawa et al 29 ; the numerical investigation was conducted under isothermal conditions in the present study, whereas it was under cooling operation in the previous study. Further details are provided in Section 4.2.…”

Section: Fundamental Study By Numerical Approachmentioning

confidence: 99%

“…Therefore, the influence of the turbulence inlet boundary condition on turbulence transfer within the room was investigated and compared with that in the simple room model. One of the room setups in the numerical investigation by Yamasawa et al 29 was chosen, as shown in Figure 2. The geometrical configuration, mesh layout, turbulence model, algorithm, and advection term scheme were identical to those used in the previous study.…”

Section: Complex Room Modelmentioning

confidence: 99%

“…Further details are provided in Section 4.1. The latter is based on the room setup in a previous study by Yamasawa et al 29 …”

Section: Fundamental Study By Numerical Approachmentioning

confidence: 99%

See 2 more Smart Citations

Influence of inlet turbulent condition on the formation mechanism of local scalar concentrations

Yamasawa

Hirayama

Kuga

et al. 2022

Japan Architectural Review

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In the existing ventilation design, the ventilation rate is defined by the time‐averaged flow rate, and the fluctuating (turbulence) component is not typically considered. However, inlet turbulent conditions are also assumed to have some influence on the formation of contaminant distributions. Therefore, the influence of turbulent kinetic energy at the inlet boundary on scalar transportation in an indoor environment needs to be elucidated when discussing the ventilation rate setpoint via the supply inlet in terms of local contaminant concentration control. This study discusses the impact of turbulent kinetic energy in the ventilation design on scalar transfer and its distribution within an enclosed space. To understand the influence of various inlet turbulent boundary conditions on scalar transfer, a computational fluid dynamics analysis was conducted using two different room models: a simple room and a room with a ventilation system that creates a large velocity gradient. The results indicate that scalar transfer within the room is not solely dominated by the averaged velocity input at the inlet boundary but is also strongly affected by the turbulence conditions at the inlet boundary. The numerical results indicate the possibility of a new ventilation design strategy that simultaneously considers the transfer of turbulent components and contaminants.

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Performance of combination of local exhaust system and floor‐supply displacement ventilation system as prevention measure of infection in consulting room

Yoshihara,

Yamanaka,

Kobayashi

et al. 2023

Japan Architectural Review

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Droplet nuclei and tiny enough droplets to move as an aerosol are regarded as one of the modes of infection transmission SARS‐CoV‐2. Various measures have been taken to prevent it worldwide. Nevertheless, many scenarios cannot be avoided close‐distance conversations, for example, in a consulting room, restaurant, or crowded train. A consulting room has significant potential for doctors to contact infected patients. Therefore, this study proposes a novel approach combining a local exhaust ventilation (LEV) and floor‐supply displacement ventilation system (FSDV) in a consulting room. This study assumes that two persons (doctor and patient) are sitting face to face and talking without a mask in a simple room regarded as a consulting room. The velocity and volume of exhaled air from talking were acquired through field measurements. Then, computational fluid dynamics (CFD) steady analysis was carried out, using the results of exhaled air measurement with various parameters (hood height, hood flow rate, horizontal hood position, and air flow rate). The capture efficiency for tracer gas and contribution distribution for the hood (SVE5: scale for ventilation efficiency 5) have been calculated to reveal the hood's capture performance. In addition, infection risk for the doctor was also calculated using the Wells–Riley model to estimate the infection performance of this ventilation system. By measuring exhaled air from talking, a speed of 0.30 m/s, a volume of 5.21 L/min, and a vertical angle of 11.9° were obtained, and these values were installed into CFD. The CFD results showed that hood flow rate significantly impacts capture efficiency at SA 120 m3/h (6 ACH), and horizontal hood position significantly impacts at SA 1000 m3/h (50 ACH). SVE5 also showed hood's effective area is greatly influenced by the flow rate balance between the hood and the other exhaust routes. Under high air supply conditions: SA 1000 m3/h (50 ACH), there was almost no airborne transmission risk for a doctor with or without a hood. However, under 120 m3/h (6 ACH) conditions, the combination of the hood and FSDV system could reduce an infection risk sufficiently. The hood should be located above the infected person's head to keep the counter person's infectious risk low, indicating that the introduction of the hood is reasonable in the consulting room, where it is easy to find where the infected person is.

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Effect of supply velocity and heat generation density on cooling and ventilation effectiveness in room with impinging jet ventilation system

Cited by 31 publications

References 34 publications

Transmission mitigation of COVID-19: Exhaled contaminants removal and energy saving in densely occupied space by impinging jet ventilation

Transmission mitigation of COVID-19: Exhaled contaminants removal and energy saving in densely occupied space by impinging jet ventilation

Influence of inlet turbulent condition on the formation mechanism of local scalar concentrations

Performance of combination of local exhaust system and floor‐supply displacement ventilation system as prevention measure of infection in consulting room

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