Study On Thermal Environment Effect Of Geometrical In Urban Street In Summer

Urban street is one of the most important part in urban outdoor public space,which serves as a transportation function and provides a place for outdoor activities.Street plays an important role in heat dissipation and ventilation of urban thermal environment.It is conducive to improve urban heat island effect.Under this extreme climate background,such as the cold area in Beijing,high temperature and humidity in summer,it is significant to study the relationship between street geometry and thermal environment from the perspective of street gap scale.It can improve the comfort of urban residents,thermal environment,and save energy of streets.As the capital of China,Beijing is a megalopolis.Since 1961,the temperature in Beijing has been rising continuously,and the urban heat island effect has become increasingly prominent.Therefore,Beijing as the research area is representative and typical.Based on the urban climate background,this paper mainly studies the correlation between street geometry(street aspect ratio,orientation)and average radiant temperature,air temperature and thermal comfort.The research contents are as follows:Firstly,the orientation,greening forms,street side buildings and aspect ratio of 30 streets in central Beijing were investigated.It is found that the streets in the central city are distributed in a chessboard pattern in the north-south and east-west directions.The main roads and branch roads are more than the secondary ones,and the main roads are less dense and less in number.Afforestation form is one board two belt type more.There are many buildings along the street and the streets with uniform distribution of high-rise buildings,with the aspect ratio between 0.3 and 1.Envi-met software was used to establish models and conduct thermal environment simulation for 8 streets,and the hourly changes of average radiation temperature,air temperature and thermal environment as well as the horizontal distribution characteristics of each street were analyzed.According to the street morphology(street aspect ratio,street orientation),8 streets were classified,and the influence of street morphology on average radiation temperature,air temperature and thermal comfort was further discussed.Average radiation temperature is directly correlated with thermal comfort.According to the horizontal distribution,the low temperature zone of average radiation temperature almost overlaps the relatively comfortable zone of thermal comfort.Street orientation has a great influence on the amount of thermal environment,and the effect of aspect ratio on thermal environment is also changed by orientation.For two streets with similar aspect ratio but different orientation,the thermal environment of north-south street is always better than that of east-west street.When comparing the same orientation with different height and width,the heat environment of the street with larger height and width ratio is better.When the aspect ratio is about 0.3,the two oriented thermal environments are similar.However,when the ratio of height to width is about 0.5~1,the thermal environment of the streets in the two directions is quite different.For completed streets,the street aspect ratio can be changed by adjusting the building height on one side of the street to improve the thermal environment of the street.For streets to be built,the orientation and aspect ratio should be specified according to the street level.The study of the thermal environment effect mechanism of street geometry can provide Suggestions and Suggestions for the future urban design and urban planning,so as to improve the urban thermal environment.