The Law Of Distribution For Complicated Radiation Fields In Urban Enclosed Buildings Space

The outdoor thermal environment is an important factor affecting the site planning,building design and building energy consumption,and solar radiation is the key factor affecting the outdoor thermal environment.With the continuous promotion of urbanization,the intensity of urban development is increasing,the form of the city’s underlying surface becomes more and more complex,and the solar short wave radiation is absorbed and reflected by the surface of the building with different orientation in the city,and causes the change of the long wave radiation energy of the building.The thermal design of traditional buildings simplifies the radiation heat because the early outdoor environment of buildings is relatively simple and the outdoor space is relatively open.But now the city is a highly concentrated area of the building,the dense building group has made the city a myriad of small,semi closed or completely closed enclosure.In the enclosed building space,it includes direct radiation,scattering,ground reflection,and long wave radiation of the sky,as well as the long and short wave reflection from the surface of the surrounding buildings,which affect and interact with each other,thus forming the complex radiation field that has an important impact on the indoor thermal environment.In view of the above situation,the paper carries out the related research on urban complex radiation field,with a view to provide the research foundation for urban planning,architectural design and building energy conservation.First,the basic concepts of radiation heat transfer and urban thermal environment are expounded.On the basis of this,the components of short wave radiation and long wave radiation in the surrounding space of building are analyzed.Based on the geometric relation of the radiation space,the spherical trigonometric method based on the space division of the hemispherical field is proposed to calculate the radiant angle coefficient between the surfaces,based on the geometric principle of spherical trigonometry and the Lambert cosine law.By comparing with other methods,it is proved that the method is suitable for calculating the radiation angle coefficient between each surface of the enclosed building space,and the operation is convenient and the precision is high.Secondly,based on the calculation model of the spatial radiation angle coefficient,the relationship between each surface of the short wave radiation in the enclosed building space and the relationship between the emission and reflection of the long wave radiation on each surface are analyzed,so as to perfect the calculation model of the intensity of the radiation field in the enclosed building space.At the same time,in the cities of Harbin,Lhasa,Xi’an and Sanya in the severe cold zone,cold zone and hot summer and warm winter zone,several relative enclosed spaces are selected for the field test,and the measured results of the short wave and long wave radiation intensity on the outward surface of the building are compared with the calculated results,and the accuracy of the calculated model is verified.It is also found that the enclosed building space has a significant increase in the radiation intensity of the long wave projection on the outer surface of the building.The higher the floor of the building or the smaller the distance between the buildings,it will increase the radiation intensity of the long wave projecting on the outer surface of the building.Finally,the paper expounds the formation mechanism of the complex radiation field of the city under the interaction of short wave and long wave in the enclosure.According to the one-dimensional unsteady heat transfer principle of the enclosure structure,the intensity model of the short wave and long wave coupling radiation field in the enclosure is established.According to the simulation analysis of four cities in Beijing,Xi’an,Fuzhou and Guangzhou,it is proved that the intensity of short wave radiation and long wave radiation on the surface of the building surface in the urban enclosure is very different from the open space in the suburb.The joint action of various radiation components leads to the change of net radiation heat of each building surface in the enclosure,which will eventually affect the heating energy consumption and air conditioning energy consumption of the building.In summary,the paper systematically sets up the distribution law of complex radiation field in the urban enclosed building space,and provides the design and analysis basis for the space layout of all kinds of buildings in the city and the energy saving analysis of the buildings in the future.