Outdoor thermal comfort: Analyzing the impact of urban configurations on the thermal performance of street canyons in the humid subtropical climate of Sydney
|نوع نگارش مقاله||
scopus – master journals – JCR
۴٫۲۷۶ در سال ۲۰۲۰
۲۶ در سال ۲۰۲۱
۰٫۹۰۱ در سال ۲۰۲۰
|شاخص Quartile (چارک)||
Q1 در سال ۲۰۲۰
خرید محصول توسط کلیه کارت های شتاب امکان پذیر است و بلافاصله پس از خرید، لینک دانلود محصول در اختیار شما قرار خواهد گرفت و هر گونه فروش در سایت های دیگر قابل پیگیری خواهد بود.
فهرست مطالب مقاله:
Abstract The quality of outdoor space is becoming increasingly important with the growing rate of urbanization. Visual, acoustic, and thermal balance degradation are all negative im- pacts associated with outdoor comfort in dense urban fabrics. Urban morphology thus needs assessment and optimization to ensure favorable outdoor thermal comfort (OTC). This study aims to evaluate the thermal performance of streets in residential zones of Liverpool, NSW, Australia, and tries to improve their comfort index (Physiological Equivalent Temperature) to reveal optimum urban configurations. This evaluation is done by investigating the following urban design factors affecting OTC using computational simulation techniques: street orienta- tion, aspect ratio, building typology, and surface coverage. Our findings reveal that street canyon orientation is the most influential factor (46.42%), followed by aspect ratio (۳۰٫۵۹%). Among the influential meteorological parameters (air temperature, wind speed, humidity and solar radiation), wind velocity had the most significant impact on the thermal comfort of the outdoor spaces in this coastal region, which typically experiences intense airflow. The results of our analysis can be utilized by multiple stakeholders, allowing them to under- stand and extract the most vital design factors which contextually influence the thermal com- fort of outdoor spaces. Outdoor thermal comfort has a direct effect on the health and wellbeing of occupants of outdoor spaces.
|بخشی از متن مقاله:|
Urban heat Island (UHI) phenomenon, which refers to the higher temperature level in cities than in surrounding areas (Piselli et al., 2018), is a critical problem caused by ur- banization and associated climate change (Akbari et al.,
2016). The high temperature in urban areas can increase energy spending owing to a high rate of cooling demand, thus increasing the pressure on the electricity grid during heat waves (Pyrgou et al., 2017). An increase in ambient temperature can also negatively affect an individuals’ health (Santamouris et al., 2017). Comfort, in conjunction with health, is being increasingly used to define wellbeing in the built environment (Bluyssen, ۲۰۱۰). There has thus been an increasing interest in studies concerning outdoor comfort (Srivanit and Jareemit, 2020). The value of well- designed open spaces in contributing towards a high qual- ity of life is now acknowledged more than ever (Klemm et al., 2015). Outdoor thermal comfort (OTC) is one of the most influential factors which directly impacts the perceived quality of urban open spaces (Zhao et al., 2018) and thus the participation in outdoor activities (Lai et al.,
2014). As a consequence, thermal comfort in outdoor space has recently attracted considerable attention for the sustainable design of cities (Emmanuel, 2016).
The effect of UHI can exacerbate in cities with a hot and humid climatic condition characterized by high air tem- perature, high humidity and low wind speed levels. Humid tropical climates tend to suffer the consequences of heat island effect twice as much as other regions. This also holds true for urban environments with humid subtropical cli- mates (such as Sydney) during the summer. More than ۳۳% of the world’s population live in such cities, which cover one of the five climate classes of Koppen’s (Cfa: humid subtropical climate, Cwa: dry-winter humid subtropical climate, Af: tropical rainforest climate, Am: tropical monsoon climate, Aw: tropical savanna climate with dry- winter characteristics). Such cities are exposed to hot and humid weather condition for a considerable period of time (Binarti et al., 2020). On the other hand, long periods of warm weather make outdoor and semi-outdoor spaces more favorable. People thus prefer to spend their time in open environments, in the absence of air-conditioning (Baruti et al., 2019).
The geometrical properties of urban blocks and con- struction materials are important factors affecting UHI (Falasca et al., ۲۰۱۹; Kantzioura et al., ۲۰۱۵). Well- designed outdoor spaces and thermally comfortable out- door environments can enhance public health and well- being (Hendel et al., 2017; Jiang et al., 2019), tourism (Ge et al., 2017), the use of open spaces, and level of social interactions (Huang et al., 2019). Studies have found that people’s activities in outdoor spaces decrease in summer with an increase in air temperature (Ta) (Lin et al., 2012). Urban outdoor areas lacking microclimatic considerations in their design thus tend to be avoided and remain unused (Lenzholzer, ۲۰۱۲), due to the lack of a practical and applicable design guideline for urban planning (Lenzholzer,
This study investigates the thermal environment of outdoor spaces in the humid subtropical climate of Sydney,
NSW, Australia, and proposes an OTC-based urban planning guideline by deploying computational optimization pro- cesses. This process incorporates the use of parametric design and simulation techniques to optimize the thermal performance of street canyons. We evaluate the current thermal environment of selected case studies and subse- quently optimize influential urban planning factors that embody the micro-climatic condition of the selected location.
۱٫۱٫ Thermal perception in outdoor environments
Thermal perception in outdoor spaces is a complex issue that can be affected by climatic characteristics of regions (Indraganti, 2010). Based on a study conducted in highly- dense urban contexts, three elements: weather condition (solar radiation, humidity, and wind speed); personal health factors; and psychological parameters, affect an individuals’ outdoor thermal sensation significantly (Sharmin and Steemers, 2020).
Among environmental factors, air Temperature is the most determining microclimatic factor affecting thermal sensation (Liu et al., ۲۰۱۶; Tan et al., 2019). Thermal comfort is also dependent on other climatic factors of radiant temperature and wind speed (Niu et al., 2015; Tan et al., 2019). Air movement with a velocity higher than
1.5 m/s has profound effects on the thermal sensation of users of outdoor spaces (Ali-Toudert and Mayer, ۲۰۰۶; Johansson and Emmanuel, 2006). Besides the pattern of solar radiation, various design factors can also lead to UHI phenomena (Ouali et al., 2018). Modifying a building’s layouts can result in a significant difference in the level of thermal comfort of outdoor spaces, especially in moderate climate conditions (Ouali et al., 2020). Many studies have investigated different strategies focusing on OTC improve- ments, namely ventilation (Hong and Lin, 2015), materials (Taleghani, 2018), vegetation (Besir and Cuce, ۲۰۱۸; Zo¨lch et al., 2016) and water bodies (Steeneveld et al., 2014). Besides this, various geometrical parameters of urban canyons, such as aspect ratio (H/W) and orientation affect environmental conditions such as solar access, wind status, air and surface temperature (Deng and Wong, 2020). Aspect ratio and Street Canyon Orientation are the most important factors in urban planning concerning outdoor thermal comfort (Bakarman and Chang, ۲۰۱۵; De and Mukherjee,
2018; Deng et al., 2016; Huang and Li, ۲۰۱۷; Taleghani et al., 2015). The following sub-section provides a brief overview of these two factors, and the urban surface con- dition factor, as influencers of OTC.
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