ABSTRACT
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.
ABSTRACT
The application of ultraviolet germicidal irradiation (UVGI) technology inside the heating, ventilation, and air-conditioning (HVAC) air ducts to purify circulating air and improve indoor air quality has attracted extensive interest during the COVID-19 pandemic. In this study, a new view-factor-based mathematical model was developed to calculate the irradiation distribution for a typical twin-tube UV lamp placed at the center of a square duct, in which the contributions from direct emissive irradiance, specular reflection irradiance, and diffuse reflection irradiance were quantified. Furthermore, the “projection area” method was introduced to mathematically estimate the shadowing effects between the two lamps by considering multiple-lamp scenarios in real in-duct UVGI system designs. Subsequently, a computational fluid dynamics (CFD) simulation was employed to compute the average received UV dose and disinfection efficiency of the system. The mathematical model combined with the CFD simulation was validated using the experimental data. It is concluded that by increasing the UV lamps, UV lamp power, and using more reflective duct wall materials, the in-duct UVGI disinfection performance can be improved. For the multiple-lamp arrangements, placing lamps perpendicular to the airflow in the same row results in a more uniform irradiance distribution and higher overall irradiation than placing them in different rows along the duct, thus increasing the disinfection efficiency. In addition, the duct wall with highly diffusive reflection provides a more uniform irradiance distribution and overall higher average radiation, thus providing better disinfection performance for an in-duct UVGI reactor.
ABSTRACT
BACKGROUND: Ultraviolet germicidal irradiation (UVGI) technologies have emerged as a promising adjunct to manual cleaning, however, their potential to shorten cleaning times remains unexplored. METHODS: A <10-minute disinfection procedure was developed using a robotic UVGI platform. The efficacy and time to perform the UVGI procedure in a CT scan treatment room was compared with current protocols involving manual disinfection using biocides. For each intervention, environmental samples were taken at 12 locations in the room before and after disinfection on seven distinct occasions. RESULTS: The mean UVC dose at each sample location was found to be 13.01 ± 4.36 mJ/cm2, which exceeded published UVC thresholds for achieving log reductions of many common pathogens. Significant reductions in microbial burden were measured after both UVGI (P≤.001) and manual cleaning (P≤.05) conditions, with the UVGI procedure revealing the largest effect size (r = 0.603). DISCUSSION: These results support the hypothesis that automated deployments of UVGI technology can lead to germicidal performance that is comparable with, and potentially better than, current manual cleaning practices. CONCLUSIONS: Our findings provide early evidence that the incorporation of automated UVGI procedures into cleaning workflow could reduce turnaround times in radiology, and potentially other hospital settings.
Subject(s)
Radiology , Robotics , Disinfection/methods , Hospitals , Humans , Ultraviolet RaysABSTRACT
Awareness of indoor air quality (IAQ) in crowded places such as schools and offices has increased since 2020 due to the COVID-19 pandemic. In addition, countries' shifting away from containment and towards living with COVID-19 is expected to increase demand for risk mitigation via air-purification devices. In this work, we use Computational Fluid Dynamics (CFD) analysis to investigate the impact of adding an air-purification technology on airflow in an enclosed space. We model a Polyester Filter and UV light (PFUV) dehumidifier in an office with two occupants: one infected with an airborne infectious disease, such as COVID-19; and the other uninfected. We compare three cases where the infected occupant coughs: with no device, and with the device at two different orientations. We construct a CFD model using ANSYS® 2021 Fluent and the Discrete Phase Model (DPM) for the particle treatment. Thermal comfort is assessed using the Testo 400 IAQ and comfort kit. We find that both the device operation and the placement alter the airflow contours, significantly reducing the potential for the uninfected occupant to inhale the vapour expelled by the infected occupant, potentially impacting the likelihood of disease transmission. The device improved thermal comfort measured by Predicted Mean Vote (PMV), Predicted Percentage Dissatisfied (PPD).
Subject(s)
Air Pollution, Indoor , COVID-19 , Cough , Humans , Hydrodynamics , PandemicsABSTRACT
Advanced building design technology is being proposed to eliminate all pathogens, including COVID-19, inside buildings naturally before they attack the human body. Pathogens comprise viruses, fungi, molds, protozoans, and bacteria that cause deadly diseases in humans. Thus, in this research, the application of solar irradiance through an outer glazing wall of the building forming Ultraviolet Germicidal Irradiation (UVGI) derived from sunlight has been performed to eliminate all pathogens inside the buildings before the pathogens attack the human body to cause deadly disease. Based on the findings that all pathogens, including COVID-19, can be killed with short-range wavelengths of 254-280 UVGI by disrupting their nucleic acid bonds, the pathogens are forced to malfunction in their biochemical functions and eventually the pathogens are caused to die. Simply, utilization of the outer glazing wall of a building to kill pathogens by controlling the photophysical reaction shall indeed be an interesting field of science to eliminate pathogens inside the building before those pathogens penetrate the human body.
ABSTRACT
The rapid increase in global cases of COVID-19 illness and death requires the implementation of appropriate and efficient engineering controls to improve indoor air quality. This paper focuses on the use of the ultraviolet germicidal irradiation (UVGI) air purification technology in HVAC ducts, which is particularly applicable to buildings where fully shutting down air recirculation is not feasible. Given the poor understanding of the in-duct UVGI system regarding its working mechanisms, designs, and applications, this review has the following key research objectives:â¢Identifying the critical parameters for designing a UVGI system, including the characterization of lamp output, behavior of the target microbial UV dose-response, and evaluation of the inactivation performance and energy consumption.â¢Elucidating the effects of environmental factors (air velocity, air temperature, and humidity) on the UVGI system design parameters and optimization of the in-duct UVGI design.â¢Summarizing existing UVGI system designs in the literature and illustrating their germicidal and energy performance in light of COVID-19 mitigation.