Integrated assessment of indoor and outdoor ventilation in street canyons with naturally-ventilated buildings by various ventilation indexesShow others and affiliations
2020 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 169, article id 106528Article in journal (Refereed) Published
Abstract [en]
The integrated assessments of indoor and outdoor ventilation are still rare so far. As a novelty, this paper aims to quantify the influence of street aspect ratios (building height/street width, H/W = 0.5–5) and window sizes (1 m × 1 m, 1.5 m × 1.5 m) on indoor-outdoor ventilation in two-dimensional streets with single-sided naturally-ventilated buildings. Numerical simulations with RNG k-ε model are validated against experimental data and the grid independence are tested as well. Air change rates per hour (ACH, h−1) are adopted for assessing indoor-outdoor ventilation by mean flows (ACHmean) and turbulent fluctuations (ACHturb) respectively. Age of air(τ), purging flow rate (PFR) and its corresponding ACHPFR are used to evaluate overall ventilation capacities.
Shallower streets experience better indoor-outdoor ventilation. Outdoor ACHPFR drop from 14.69 to 17.55 h−1 to 3.96–3.97 h−1 as H/W rises from 0.5 to 3. In extremely deep canyon (H/W = 5), two-counter-rotating vortices produce much smaller velocity at low-level regions (U/Uref~10−3-10−5), resulting in small ACHPFR for outdoor (~0.76–0.91 h−1) and indoor in 1–13th floors (~0.03–0.61 h−1). When H/W = 0.5–1, leeward 5–6th floors experience smaller ACHPFR(e.g.~1.13–1.40 h−1 as H/W = 1) than the other floors (e.g. ~1.54–9.52 h−1 as H/W = 1). Particularly, as H/W = 2–3, leeward-side indoor ACHPFR in the middle floors (except the first and top two floors) are nearly constants (~1.02–1.69 h−1) and much smaller than windward-side ACHPFR(~1.41–4.35 h−1) which increase toward upper floors. Besides, the smaller window size reduces indoor ACHPFR by 19.38%~88.28%, but hardly influences outdoor ventilation. Moreover, both outdoor and indoor ACHPFR are greater than ACHmean but smaller than ACHmean + ACHturb. Although further investigations are still required, this paper provides an insight and scientific foundation on integrated indoor-outdoor ventilation evaluation with various effective ventilation indexes.
Place, publisher, year, edition, pages
Elsevier, 2020. Vol. 169, article id 106528
Keywords [en]
Computational fluid dynamics (CFD), Urban ventilation, Building natural ventilation, Air change rate per hour (ACH), Age of air, Purging flow rate (PFR)
National Category
Civil Engineering
Research subject
Sustainable Urban Development
Identifiers
URN: urn:nbn:se:hig:diva-31206DOI: 10.1016/j.buildenv.2019.106528ISI: 000532293800011Scopus ID: 2-s2.0-85075610964OAI: oai:DiVA.org:hig-31206DiVA, id: diva2:1376069
Funder
The Swedish Foundation for International Cooperation in Research and Higher Education (STINT), CH2017-72712019-12-062019-12-062021-02-17Bibliographically approved