Impact of Ventilation Strategy on the Transmission of Outdoor Pollutants into Indoor Environment Using CFD

Abstract

The transition to remote working due to the pandemic has accentuated the importance of clean indoor air, as people spend a significant portion of their time indoors. Amongst the various determinants of indoor air quality, outdoor pollution is a significant source. While conventional studies have certainly helped to quantify the long-term personal exposure to pollutants and assess their health impact, they have not paid special attention to the mechanism of transmission of pollutants between the two environments. Nevertheless, the quantification of infiltration is essential to determine the contribution of ambient pollutants in indoor air quality and its determinants. This study evaluates the transmission of outdoor pollutants into the indoor environment using 3D computational fluid dynamics modelling with a pollution dispersion model. Naturally ventilated buildings next to an urban canyon were modelled and simulated using Ansys Fluent and validated against wind tunnel results from the Concentration Data of Street Canyons database. The model consisted of two buildings of three storeys each, located on either side of a road. Two line-source pollutants were placed in the street, representing traffic emissions. Three internal rooms were selected and modelled on each floor and implemented with various ventilation strategies. Results indicate that for a canyon with an aspect ratio of 1, indoor spaces in upstream buildings are usually less polluted than downstream ones. Although within the canyon, pollution is 2–3 times higher near the upstream building. Cross ventilation can minimise or prevent infiltration of road-side pollutants into indoor spaces, while also assisting in the dispersion of ambient pollutants. The critical configuration, in terms of air quality, is single-sided ventilation from the canyon. This significantly increases indoor pollutant concentration regardless of the building location. The study reveals that multiple factors determine the indoor–outdoor links, and thorough indexing and understanding of the processes can help designers and urban planners in regulating urban configuration and geometries for improved indoor air quality. Future works should look at investigating the influence of indoor emissions and the effects of different seasons.

Potential Pollutants and Indoor Air Quality Variables Association towards Implementation of the Breathing Architecture Concept: A Review

“…Several factors that cause the decline of IAQ include tobacco smoke, dampness, mold, or household pollution that produces several pollutant gases [3] [4], and it is exacerbated by insufficient air circulation inside. Otherwise, air pollution reduction will increase life expectancy and well-being [5]. Therefore, improving IAQ through sufficient ventilation is essential [6] as it could change indoor air pollutants with fresh air.…”

Large eddy simulation of sneeze plumes and particles in a poorly ventilated outdoor air condition: A case study of the University of Houston main campus

“…Such fluidal movements of fresh and old air are often affected by complex urban morphology that varies with different coordinations of obstructing structures and features (e.g., buildings and corridors in between). There have been extensive efforts to produce more realistic representations of urban surface features that can affect ventilation efficiency by using generic buildings in tangible and digital forms crafted and generated based on the ground- and satellite-based light detection and ranging (LIDAR) measurements supported by computer-aided design (CAD) techniques ( Farea et al, 2015 ; Mohammadi and Calautit, 2021 ; Juan et al, 2022 ; Hadavi and Pasdarshahri, 2020 ; Brozovsky et al, 2021 ; Liu et al, 2019 ; Nikkho et al, 2017 ). Supported by such enhanced details of urban aerodynamics available for use, many CFD studies have effectively captured near-surface airflows and the consequent dispersion of air pollutants in outdoor environments supported by turbulence schemes, such as the Reynolds-Averaged Navier-Strokes (RANS) model ( Ding and Lam, 2019 ; Buccolieri et al, 2015 ; San Jose et al, 2021 ; Hadžiabdić et al, n.d. ) and Unsteady RANS (URANS) model ( Gousseau et al, 2011 ; Rajasekarababu et al, 2022 ).…”

Research on air pollution characteristics and planning strategy of urban street environment

“…The flow field and pollutant distribution inside streets show spatial variations due to the various geometric characteristics of street canyons [17] , which also affect the interaction between indoor and outdoor air of street buildings. Especially for naturally ventilated buildings, street air pollution is a key factor affecting indoor air quality [18][19] . Studying the air pollution characteristics of street canyons is conductive to provide references for the ventilation design of street buildings.…”