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Analysis of COVID-19 clusters involving vertical transmission in residential buildings in Hong Kong region

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Building Simulation 2023年第5期16卷 701-711页

作者： Pengcheng Zhao Department of Mechanical Engineering The University of Hong KongPokfulamHong KongChina

Multiple clusters of coronavirus disease 2019(COVID-19)in Hong Kong have involved vertical transmissions in residential buildings,wherein the flats of confirmed cases were often vertically aligned.Data on the buildings and cases associated with 19 such clusters were retrieved and compared with the corresponding data on the entirety of Hong Kong region.Vertical transmissions usually occurred in old high-rise buildings with small flat areas and low estate prices during winter.In addition,infection occurred frequently among the elderly and among upstairs neighbours of index cases.Virus-laden aerosols may have been transmitted between flats mostly via shared drainpipes,and the vertical distribution of the confirmed cases in a building varied by its drainage system design.For buildings with their entire drainpipes installed indoors,both the upstairs and downstairs neighbours of the index case flats could be infected.By comparison,buildings with their drainage stacks installed outdoors had lower infection risks and demonstrated a clearer pattern of vertical transmission:most infected cases resided upstairs from the index case flats,indicating that the virus spread could be dominated by the stack effect.This study provides valuable data and analysis for developing epidemic control strategies for residential buildings.

关键词： drainage system high-rise building infection SARS-CoV-2 stack effect ventilation

The influence of airtightness on contaminant spread in MURBs in cold climates

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Building Simulation 2022年第2期15卷 249-264页

作者： Philip Mckeen Zaiyi Liao Department of Architectural Science Ryerson UniversityTorontoM5B2K3Canada

Tall buildings in cold climates have unique challenges in maintaining indoor air quality due to stack effect.During the heating season,interior air buoyancy creates large pressure differentials in vertical shafts that can drive airflow from lower floors into upper floors.This pressure differential can result in the spread of contaminants throughout a building.Most recently,concern over COVID-19 has increased attention to the potential spread of airborne diseases in densely populated buildings.For many multi-unit residential buildings,suite ventilation has traditionally relied upon fresh air supplied through a mechanically pressurized corridor.In cold climates,large pressure differentials created by stack-effect can reduce the effectiveness of this approach.Multizone and CFD simulations are employed to analyze airflow and contaminant spread due to stack effect.Simulations are conducted on an idealized model of a 10-storey building using a range of experimentally derived airtightness parameters.Simulations demonstrate stack effect can reduce corridor ventilation to suites and even reverse the airflow for leakier buildings.Reduced airflow to suites can result in the accumulation of contaminants.Reversal of the airflow can allow contaminants from a suite to spread throughout the building.Contaminant spread is illustrated as a function of mechanical ventilation,building airtightness,and ambient temperatures.Strategies to reduce the influence of stack effect on mechanically pressurized corridors are discussed.

关键词： MURBs ventilation contamination spread stack effect

A numerical study on smoke behaviors in inclined tunnel fires under natural ventilation

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Journal of Safety Science and Resilience 2022年第2期3卷 169-178页

作者： Jie Kong Wenjiao You Zhisheng Xu Hui Liu Haihang Li College of Quality&Safety Engineering China Jiliang UniversityHangzhou 310018China Zhejiang Police College Hangzhou 310053China School of Civil Engineering Central South UniversityChangsha 410075China

To investigate the effect of tunnel slope on hot gas movement and smoke distribution in a slopping tunnel fire,a series of tunnel fire models are built by fire dynamics simulator(FDS),with a slope varies from 0 to 10%.Parameters such as ceiling temperature and airflow velocity are measured.The results indicate that the relationship between smoke back-layering length and tunnel slope can be described as an exponential function.The smoke temperature at the downstream exit first increased and then decreased with a higher slope.The airflow velocity at downstream outlet increased nonlinearity when tunnel slope was less than 8%.In the slope tunnel,the fire smoke spread process can be divided into three stages.Fire smoke spreads upstream to the peak distance,subsequently,the upstream smoke layer decreases gradually,the tunnel fire reaches a quasi-steady state.The backflow characteristics of smoke in sloped tunnels are coupled with the downstream length and outlet smoke temperature.In the initial stage of a slope tunnel fire,smoke spreads upstream for a long distance,endangering human health.

关键词： Tunnel fire Slope stack effect Smoke movement Back-layering length

Gaseous pollutant transport from an underground parking garage in a Mediterranean multi-story building—effect of temporal resolution under varying weather conditions

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Building Simulation 2021年第5期14卷 1511-1523页

作者： Rivka Reichman Yael Dubowski Faculty of Civil and Environmental Engineering Technion-Israel Institute of TechnologyHaifa32000Israel

Indoor air dynamics and quality in high density residential buildings can be complex as it is affected by both building parameters,pollution sources,and outdoor meteorological conditions.The present study used CONTAM simulations to investigate the intra-building transport and concentration of an inert pollutant continuously emitted from an underground garage of a 15-floor building under moderate Mediterranean weather.The effects of outdoor meteorological conditions(air temperature,wind speed and direction)on indoor distribution of the emitted pollutant was tested under constant conditions.The importance of using actual transient meteorological data and the impact of their temporal resolution on calculated concentrations and exposure levels were also investigated.Vertical profiles of air exchange rate(AER)and CO concentration were shown to be sensitive to indoor-outdoor temperature difference,which controls the extent of the stack effect and its importance relative to wind effect.Even under constant conditions,transient mode simulations revealed that the time needed for pollutant distribution to reach steady state can be quite long(>24h in some cases).The temporal resolution(Ih vs.8h)of the meteorological data input was also found to impact calculated exposure levels,in an extent that varied with time,meteorological conditions and apartment position.

关键词： CONTAM indoor air quality high rise residential buildings stack effect wind effect inter-flat dispersion variable meteorological data effect

Assessing cooling energy reduction potentials by retrofitting traditional cavity walls into passively ventilated cavity walls

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Building Simulation 2021年第4期14卷 1295-1309页

作者： Ri Na Zhigang Shen Department of Civil and Environmental Engineering University of DelawareNewarkDE19716USA The Durham School of Architecture Engineering and Construction University of Nebraska LincolnLincolnNE68588USA

A major roadblock in achieving substantial building energy reduction is the low performance of old buildings that account for a significant portion of the building energy consumption.Finding low-cost energy retrofit solutions that do not disrupt occupants’daily life during the retrofitting is the key to successful building energy retrofit initiatives.In this paper,a novel and low-cost exterior wall retrofitting solution is introduced,and its performance in reducing space cooling load was quantitatively evaluated to demonstrate its feasibility and effectiveness.The primary goal of this paper is to provide a quantitative assessment of the cooling-energy savings potential by using the proposed new wall system.The intended retrofitting targets are the large amount of existing cavity-wall buildings located in hot climate regions.The quantification of the before-after heat-flux reduction was conducted through a 3-dimensional steady-state low turbulence computational fluid dynamics(CFD)model,which is validated by benchmarking its prediction against the published experimental case results.The outcomes of the investigation suggest that this simple low-cost solution has great potentials in reducing buildings’summer cooling load in hot climate regions.The applicability of this solution is not limited to retrofitting existing buildings.New energy-efficient building designs can also adopt this solution in their envelope systems.

关键词： low-cost energy retrofit building envelope cavity wall stack effect space cooling energy reduction CFD