Research On The Effect Of Surface Heat Transfer Of Changes From Urban Underlaying Surface Material

The process of urbanization in China has developed rapidly since the new century?By the end of 2017,the urbanization rate in China reached 58.52%.The backside of the increase of urbanization rate is the rapid development of urbanization?The high-speed urbanization process has brought about drastic changes in the material of the underlying surface,reducing of Greenland water bodies,increasing of artificial buildings and the roughness of cities surface?The artificial material hinders the natural circulation and worsens the urban thermal environment because of its low thermal capacity,high thermal conductivity,high absorption of the sun,high emissivity,and an increase in the surface roughness which reduces the sky angle of view.In this paper,the total heat output of the city's underlying surface is taken as the object of study to explore the issues of infrared radiation energy,convective heat transfer energy,and latent heat energy output of materials of different underlying surfaces.These energy can be directly absorbed by the atmosphere.It can provide basic support for revealing the evolution of urban thermal environment in the process of urbanization.First,taking Chongqing University City as an example,through the analysis of satellite imagery and field research,this paper have drawn a detailed distribution of materials and changes in the underlying surface of the study area from 2005 to 2015.The results show that the material of the underlying surface is from the original Vegetation changes to exposed soil,concrete,asphalt,plastics,metals,etc.The proportion of vegetation area decreased from 93.61% in 2005 to 69.16% in 2015.The proportion of concrete,asphalt,metal,and plastic on the artificial underlying surface increased from 0% in 2005 to 26.15% in 2015.The proportion of water area is unchanged.Through field research,the area and height of the artificial structures in the target area were obtained,and the area expansion coefficient in the research target area was 1.678.Secondly,the energy output of the underlying surface was calculated and it was concluded that from 2005 to 2015,the energy output of the underlying surface increased year by year,the average annual increase rate was 0.37%,of which the summer energy output increase rate was 0.65%,and the spring energy output increase rate was 0.39%,the increase rate of energy output in autumn was 0.25%,and the increase rate of energy output in winter was 0.09%.Further research found that the energy increase rate in summer sunny days was 0.81%.At the same time,comparing infrared radiation heat transfer energy,convective heat transfer energy and latent heat energy output,infrared radiation energy has the greatest impact on the urban thermal environment on a dominant position.The range of convection energy/radiation energy ratio is-0.093~ 0.199,latent heat energy/radiation energy ratio range is 0.002~0.063.Finally,through the energy output analysis of the material of the underlying surface at typical times of typical weather conditions,the results show that different underlying surface materials have great difference on the energy output of the urban surface.According to the average annual total heat flux of materials,the general order is that asphalt,plastics are larger than concrete,tile roofs,metals,soil is bigger than water bodies,and vegetation;there are certain differences in summer sunny days,and the order is plastic and asphalt.,concrete,metal,tile roof,water body,soil and vegetation,the energy output of the artificial material underlying surface is far higher than the natural material underlying surface,the average total heat flux of the plastic is 170W/m2 higher than the vegetation;slightly in winter conditions Differently,sorting from big to small is generally plastic,asphalt,water,soil,vegetation,tile roof,concrete,vegetation and metal.The artificial underlay surface and the natural material underlay surface are not significantly different.The real reason is that in winter concrete,metal and tile roofs absorb heat from nearby air in a low-temperature environment.Sorting from big to small is asphalt,plastic,concrete,tile roof,metal,soil,water body,and vegetation;there are certain differences in summer sunny days,ranging from plastic to asphalt,concrete,metal,and tile roofs.Water,soil and vegetation,the energy output of the artificial material underlying surface is far higher than the natural material underlying surface,the average total heat flux of the plastic is 170W/m2 higher than the vegetation;slightly different in the winter,sorting from big to small For plastics,asphalt,water,soil,vegetation,tile roofs,concrete,vegetation and metal,the artificial underlay surface and the natural material underlay surface are not much different.The reason for this is that in winter with low temperatures,the concrete,metal,and tile roofs absorb heat from nearby air.