The Impact Of Urban Underlay On Outdoor Radiation Field And Thermal Environment

Solar radiation is a key element affecting the urban thermal environment.The hardened underlying surface and high-density building group make the urban space not only have short-wave direct radiation,scattered radiation,but also have strong reflected radiation and strong long-wave radiation.All of these radiations constitute a complex urban radiation field.The urban radiation field has an important impact on the building’s thermal loss,which in turn affects the building’s energy consumption;it also has an important impact on the thermal comfort of the human body in the outdoor environment.Therefore,the urban radiation field is an important research content in the urban environment and building energy conservation.In view of the above problems,this paper studies the impact of urban underlying surface on the outdoor radiation field and thermal environment.First of all,this paper expounds the concepts related to urban radiation field and urban thermal environment,the radiation composition in urban radiation field,the basic theory of radiation effect on urban environment and the research status quo of radiation field at domestic and abroad.The comparisons of the implementation principle and input & output of the current mainstream urban radiation field simulation tools are made.This paper combines field test data to compare the performance of different urban outdoor radiation field simulation tools for different underlying surface properties and urban building spatial structures.The study has found that Rayman has fast simulation and high sensitivity in calculations,but the output radiation parameters are fewer.ENVI-met can calculate the most radiation parameters,and SOLWEIG can be used for outdoor large space simulation.Then,the applicability analysis of urban radiation field is done for these three softwares.Secondly,this paper uses the measured data from Xi’an and Baotou to analyze the short-wave reflected radiation and long-wave radiation intensity above different underlying surfaces.The study has found that the reflected radiation intensity above the underlying surface of the asphalt is the smallest,and the difference in the reflected radiation intensity above the underlying surface of the paving brick and the concrete is not obvious.The long-wave radiation intensity above the three different artificial underlying surfaces is greater than the long-wave radiation intensity above the grass underlying surface,and the air temperature above the asphalt underlying surface is the highest.The air temperature above the artificial surface of Xi’an and Baotou is higher than the air temperature above the underlying surface of the grassland.In this paper,the simulation performance of the simulation tool is verified by a progressive method.The verification results show that the simulated values of the radiation field,air temperature and relative humidity in summer and winter are in good consistency with the measured values.For the study of different radiation field factors,the properties of different underlying surfaces in summer and winter(reflectivity of underlying surface,thermal conductivity of underlying surface materials,thermal storage performance of underlying surface materials)and the influences of architectural space above different underlying surfaces(distance,height,orientation and enclosure of block)on the urban radiation field are studied,and the similarities and differences of these factors’ influences on urban radiation field are compared.For the study of the thermal environment affecting the thermal environment,the reflectivity of the urban underlying surface in summer and winter and the ratio of the height of the building to the building spacing H/W of the radiation field change on the outdoor thermal environment are studied.At the end of the paper,the optimization strategy of the building space structure above the urban underlying surface and the underlying surface is proposed from the perspective of optimizing the urban radiation field and improving the urban thermal environment,in order to reduce the building energy consumption and improve the human body’s outdoor thermal comfort.The design proposes new ideas for optimizing the urban radiation field.