Résumé
This investigation presents results of Computational Fluid Dynamics (CFD) modelling of aerosol behaviour within an arbitrary 'realistic' 100m2 office environment, with dynamic and variable respiratory droplet release profile applied based on published findings (Morawska et al., 2009). A multitude of ventilation strategies and configurations have been applied to the base model to compare the effectiveness of reducing the concentration of suspended aerosols over time. A key finding of the investigation indicates a relatively low sensitivity to increasing outside air percentage, and that the benefit from this strategy is heavily dependent on the in-duct droplet decay factor. The application of local recirculating air filtration systems with MERV-13 filters mounted on occupant desks proved significantly more effectiveness than increasing outside air concentration from 25% to 100% in reducing the quantity of suspended aerosols. This highlights that the ventilation industry should perhaps focus on opportunities to integrate filtration systems into furniture, partitions, cabinetry etc., and that an appliance-based solution may be more beneficial for reducing COVID-19 transmission in buildings (and likely more straightforward) than modifications to central ventilation systems, particularly in the application of refurbishments and retrofits. © 2022 17th International Conference on Indoor Air Quality and Climate, INDOOR AIR 2022. All rights reserved.
Résumé
We have modeled the transmission of coronavirus 2019 in the isolation room of a patient suffering from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the Royal Brompton Hospital in London. An adaptive mesh computational fluid dynamics model was used for simulation of three-dimensional spatial distribution of SARS-CoV-2 in the room. The modeling set-up is based on data collected in the room during the patient stay. Many numerical experiments have been carried out to provide an optimal design layout of the overall isolation room. Our focus has been on (1) the location of the air extractor and filtration rates, (2) the bed location of the patient, and (3) consideration of the health and safety of the staff working in the area. © 2023 Author(s).
Résumé
New Zealand and many countries gained heightened awareness of indoor air quality (IAQ) issues, and increased investment, according to the World Health Organization (WHO) guidelines, to improve their IAQ and reduce air pollution in commercial and residential buildings. Additionally, some countries have introduced new standards for indoor environments, such as the New Zealand "healthy homes” standard. At the same time, COVID-19 pandemic forced many people to spend much more time in indoor spaces, due to stay-at-home, or lockdown orders by governments. This increased attention on other aspects of indoor environmental quality, such as occupants' satisfaction with thermal comfort parameters, presents an additional parameter for research and in the development of standards. From a medical perspectives, infectious respiratory diseases, such as influenza or COVID-19, are transmitted by airborne droplets. In this work, we assess a Polyester Filter and UV light (PFUV) dehumidifier device performance in an office with two occupants (one uninfected and the other one infected with a disease with airborne transmission using computational fluid dynamics (CFD) approach. Two positions for locating the PFUV dehumidifier in an office with a scenario in which one person is exhaling infected air and the other occupant must inhale and exhale from the shared air. The CFD model illustrated the best position of the device to distribute the air velocity contours. Further, based on the CFD model which was validated via the IAQ and comfort kit (Testo 400) thermal comfort analysis showed that the room is slightly cold. Copyright © 2022 by ASME.
Résumé
With the growing scarcity of semiconducting devices stemming from volatile prices, shortened supplies, and increasing demand that are attributed to the Covid-19 pandemic, manufacturers are looking for efficient ways to facilitate the production of nanoscale semiconducting devices. Thermal atomic layer etching (ALE) is a promising method that can overcome the obstacles encountered during the production of semiconducting devices via conventional approaches by delivering precise dosages of reagent to etch monolayers of substrate surface material in a cyclic operation. However, thermal ALE has not been extensively studied and characterized to become fully embraced by the semiconductor manufacturing industry. Recent work by our group has led to the development of a multiscale computational fluid dynamics modeling framework that was used to optimally design a desirable reactor configuration for the thermal ALE process. Despite this progress, additional research is needed to ensure that the film quality is maintained in the presence of operational disturbances. Therefore, the present work is focused on the development of a multivariable Run-to-Run (R2R) control system to mitigate the impact of critical operational disturbances. It is demonstrated that the developed multivariable R2R control system can efficiently overcome the negative effects of unknown disturbances that may impact film uniformity by regulating input variables within a minimal number of batch runs.
Résumé
Assessing and improving the safety of social settings is pivotal for the reopening of facilities and institutions during the pandemic. Recent discoveries now suggest that the predominant medium of SARS-CoV-2 transmission is exposure to infectious respiratory aerosols. Airborne viral spread is particularly effective in indoor environments-which have been strongly implicated in high transmission rates and super-spreading events. This study focuses on computational fluid dynamics models developed to study the specific ventilation features of an indoor space and their effects on indoor particle spread. A case study is conducted on a typical classroom at the Cooper Union. Masked occupants are modeled in the room as aerosol sources to compare the performance of different ventilation settings on the exhaust rates of airborne particles. Simulation results reveal that increasing ventilation rates accelerate particle evacuation. Visualization and segregated data comparisons indicate regions of particle accumulation induced by the design and geometry of the classroom in relation to its occupants. Visualization is also used to observe a uniform distribution of airborne particles after only 10 minutes of simulated time-confirming the need for safety measures beyond the six feet distancing guideline. © 2021 by ASME.