Typed Study On The Thermal Comfort Regulation Effects Of Street Trees Under The Effect Of Solar Radiation In Xi'an

Urban street is not only the path of transportation,but also the important outdoor public space for urban residents.It's thermal environment directly affects the thermal comfort of urban residents.In summer,street trees can improve the urban street microclimate and intercept the quality of urban streets by blocking direct solar radiation.Studying the climate adaptive design theory of street tree-lined space,advocating street climate adaptive design practice and providing street users with comfortable walking environment have becoming an important subject that cannot be ignored in the field of landscape architecture planning.The subject of this thesis is urban streets in Xi'an,the urban streets in Xi'an has been classified into different types by street space design factors,the thermal environment of typical streets in summer and winter has been analyzed through field measure and computer simulation,thus proposed the key design factor which affect pedestrians' thermal comfort in summer and winter respectively,and the modification effect of treelined space has been special discussed,then design suggestion of tree-lined space has been proposal.The major study objects include:(1)Classification of urban street in Xi'an city based on pedestrian thermal comfort.Based on the theory of street thermal environment and pedestrians' thermal comfort,the street design factors which affect pedestrians' thermal comfort has been proposed,the classification level has been set up by degree of design factors,the streets in Xi'an have been classified by ‘function-orientation-width-aspect ratio-tree space type'.(2)Thermal environment analysis of typical streets.The microclimate field measured of 8 typical streets has been carried out in summer and winter,according to the air temperature data and sunlight simulation result,discussing the thermal environment features of these typical streets.(3)The thermal comfort assessment of typical streets in winter.The period in winter day when solar radiation is strong has been divided into two periods: morning and afternoon,and the full sun area is the most comfort zone,area in shadow all the time is the discomfort zone,area under sunshine only in the afternoon is sub-comfort zone,and area under sunshine only in the morning is sub-discomfort zone.The thermal comfort of street in winter is discussed with the area ratio of comfortable areas at all levels,proposed that the main factors affect the thermal comfort of streets in winter is the morphology of street canyon.(4)The thermal comfort assessment of typical streets in summer.The period in summer day when solar radiation is strong has been divided into three periods: morning,noon and afternoon,in each period,the area in building shadow is the comfort zone,and the area in tree shadow is the sub-comfort zone,and the area under sunlight is the discomfort zone,the thermal comfort level of streets in summer is assessment by the thermal comfort level of sidewalk.(5)The thermal comfort modification effect of street trees in typical streets.The thermal comfort regulation effect of street trees is assessment by the cooling effect and shading effect,and the result showed that trees space type and the street canyon morphology would influence the modification effect of street trees;the difference of thermal comfort regulation effect of 5 different tree species has been analyzed by field measured data,and the Leaf Area Index is the majority factor affecting the thermal comfort regulation effect of street trees;the design suggestions of stree trees were proposed,including how to choose the trees space type and tree species.