Impact of Indoor-Outdoor Temperature Difference on Building Ventilation and Pollutant Dispersion within Urban Communities

Abstract

Mechanical ventilation consumes a huge amount of global energy. Natural ventilation is a crucial solution for reducing energy consumption and enhancing the capacity of atmospheric self-purification. This paper evaluates the impacts of indoor-outdoor temperature differences on building ventilation and indoor-outdoor air pollutant dispersion in urban areas. The Computational Fluid Dynamics (CFD) method is employed to simulate the flow fields in the street canyon and indoor environment. Ventilation conditions of single-side ventilation mode and cross-ventilation mode are investigated. Air change rate, normalized concentration of traffic-related air pollutant (CO), intake fraction and exposure concentration are calculated to for ventilation efficiency investigation and exposure assessment. The results show that cross ventilation increases the air change rate for residential buildings under isothermal conditions. With the indoor-outdoor temperature difference, heating could increase the air change rate of the single-side ventilation mode but restrain the capability of the cross-ventilation mode in part of the floors. Heavier polluted areas appear in the upstream areas of single-side ventilation modes, and the pollutant can diffuse to middle-upper floors in cross-ventilation modes. Cross ventilation mitigates the environmental health stress for the indoor environment when indoor-outdoor temperature difference exits and the personal intake fraction is decreased by about 66% compared to the single-side ventilation. Moreover, the existence of indoor-outdoor temperature differences can clearly decrease the risk of indoor personal exposure under both two natural ventilation modes. The study numerically investigates the building ventilation and pollutant dispersion in the urban community with natural ventilation. The method and the results are helpful references for optimizing the building ventilation plan and improving indoor air quality.

Numerical Analysis of the Effects of Different Window-Opening Strategies on the Indoor Pollutant Dispersion in Street-Facing Buildings

“…But, the natural ventilation effect is greatly affected by external climate conditions (such as wind speed, wind direction, and temperature differences), and it is difficult to ensure a stable ventilation effect. To examine the dispersion patterns of pollutants in urban settings under natural ventilation, researchers' studies have focused on analyzing pollutant dispersion in street canyons through CFD simulations [5][6][7][8][9], wind/water tunnel experiments [2,[10][11][12], and field measurements [13][14][15]. The primary source of pollutant exposure within street canyons stems from vehicle emissions, which vary across vehicle models and emission levels under distinct driving conditions.…”

On-site airborne pathogen detection for infection risk mitigation

“…Four different open source CFD softwares, PALM, OpenFOAM, NS3dLab, and fire dynamics simulator (FDS), have been applied to investigate the SARS-CoV-2 exposure levels in generic public places, enclosed/semi-enclosed restaurants, airplanes, negative-pressure wards, as well as outdoor spaces. 114,123–129 CFD models are also used to investigate the transport of pathogen bioaerosol in the respiratory airways, which could contribute to better exposure assessment. 130 In the CFD models, the Eulerian–Lagrangian-coupled framework has been normally adopted respectively for flow field (Eulerian method) and particle motion (Lagrangian method).…”

A frontal air intake may improve the natural ventilation in urban buses

“…31 for a general review on the subject). CFD simulations have also been usefull to asses the air quality and associated thermal comfort levels inside cars 32 , natural ventilated rooms 33 and buildings within urban communities 34 , to mention a few. Briefly (the details can be consulted in the Methods section), the numerical model solves the internal and external air flow formed simultaneously along a real-sized bus traveling at a representative speed of U = 50km/h (13.9m/s) and having a certain distribution of open windows.…”