Research On Outdoor Thermal Environment Of Urban Residential Areas In Xi'an

Urban residential areas are areas where people have activities frequently,and outdoor thermal environment changes directly affect people's daily life.Therefore,having a nice and comfortable living environment is the common goal of people.In recent years,due to the acceleration of urbanization in Xi'an,hot islands,haze and other phenomena have become an important issue affecting urban development.To solve these environmental problems,it is necessary to improve the outdoor thermal environment in urban residential areas.The government has made corresponding requirements on the architectural planning and design,and the green building design is rapidly promoted.As an important part of green building design,outdoor thermal environment in residential areas has become an important topic in this field.Many scholars at home and abroad have carried out relevant research.At the same time,“Green Building Evaluation Standard” GB50378-2014 has corresponding requirements for the outdoor thermal environment of residential areas.It explicitly proposes that two aspects can be adopted to decrease the heat island intensity and improve outdoor thermal environment in residential areas: increasing the area of sun-shading measures for outdoor activities in residential areas,or using land covering materials with a solar radiation reflection coefficient of no less than 0.4 in a wide range of road surfaces and building roofs.As an important representative of cold regions,Xi'an has a unique geography and characteristic of microclimate.In order to find more improvement measures applicable to the Xi'an region's outdoor thermal environment,this project has developed aresearch system of outdoor thermal environment,aiming on the unique climate characteristics of Xi'an area.After a previous investigation of urban residential areas in Xi'an,the different planning,layout,space environment,land covering materials,sun-shading measures,greenbelt and greening condition of the residential areas in Xi'an were researched and recorded.From multiple residences,two representative residential areas in this district were selected for the questionnaire survey and field tests.It was found that the outdoor thermal environment of the residential area was not satisfied,and there was a situation where the heat island intensity was higher than1.5°C.Through the quantitative analysis of the relationship between the heat island intensity and outdoor thermal environment factors in residential area,such as land covering material,greening patterns and sun-shading measures,the cloud map of outdoor temperature distribution is established by GIS software;Combining CFD numerical simulation,it is proposed that a certain angle between the building and the dominant wind direction can be made in the building layout,guiding the air properly flow into the site for ventilation and temperature reduction of the residential area,enhancing the natural ventilation to improve the outdoor thermal environment in urban residential area of Xi'an area;Meanwhile,it is recommended to use permeable floor pavement of more than 61% in area proportion to optimize the outdoor thermal environment and reduce the heat island intensity of residential areas.The semi-permeable pavement structure can be adopted for the part with higher requirements for roadbed strength.Through this research,outdoor thermal environment optimization measures applicable to Xi'an area are proposed from aspects of residential area planning,layout,space environment,land covering materials(solar radiation reflection,moisture penetration and evaporation),sun-shading measures,greenbelt and greening pattern,so as to provide theoretical basis and technical guidance for the sound development,scientific and reasonable residential planning of urban residential areas in Xi'an.It has a direct practical significance and an important value for the more in-depth analysis of the outdoor thermal environment in residential areas in Xi'an,the improvement of living environment quality,and promotion of urban environmental construction.