Research On Heat Transfer Process Of Typical Urban Underlying Surface And Design Of Visualization Platform

With the acceleration of urbanization in China,a large number of natural pervious underlying surfaces have been replaced by impervious hard underlying surfaces.These impervious underlying surfaces have good thermal conductivity,high thermal capacity and poor infiltration capacity,which have a serious impact on the urban thermal and water environment.In this study,we focus on four typical urban underlying surfaces,asphalt,cement,pervious brick,and lawn.Based on the theory of heat transfer and fluid mechanics,we establish a solar radiation model and a rainfall convection model to analyze the heat transfer process of thermal radiation,thermal conduction,and thermal convection of urban underlying surface under different meteorological conditions.The fitting effects of both models are good:For solar radiation model,0.89?R~2?0.99,3.72??MSE?6.00?,1.93??RMSE?2.45?,1.87??MAE?2.17?.For rainfall convection model,0.95?R~2?0.96,0.03??MSE?0.05?,0.17??RMSE?0.21?,0.15??MAE?0.2?.Results show that:1)Different meteorological factors have different effects on the land surface temperature of underlying surfaces.The correlation coefficients between air temperature,solar radiation and land surface temperature of cement and lawn are positive,which significantly promote the growth of land surface temperature of underlying surface.On the contrary,the correlation coefficients of relative humidity,wind speed and rainfall with the land surface temperature of cement and lawn are negative,which can inhibit the growth of the land surface temperature of the underlying surface.2)In the absence of rainfall,the land-surface temperature of asphalt,cement,and pervious brick underlying surface is higher than air temperature,which has a positive effect on urban near-surface air temperature.And the land surface temperature of asphalt is the highest,the mean temperature of cloudy weather is 19.1?,and that of sunny weather is 32.9?;In addition,the mean temperature of grass ground surface is the lowest,the cloudy weather is 14.7?,the sunny weather is 26.1?,which has a negative feedback effect on the urban near surface temperature.3)In the rainfall,the underlying surface transfers heat to the runoff in the form of convection,forcing the runoff temperature to rise.Among the four types of underlying surfaces,asphalt has the most obvious effect on runoff heating.The runoff temperature rises by about 1.5?after rain in rainy weather and 2.3?after rain in sunny showers.The effect of grassland on runoff temperature is minimal,and the runoff temperature changes little after rainfall.The runoff temperature difference before and after rainfall in rainy weather is about 0.2?,while that in sunny days is about 0.4?.The research suggests that in the hot and high–temperature site,it can reduce the surface temperature and improve the local thermal environment by paving lawn and pervious bricks.In the neighborhood of water body,the pervious underlying surface should be used to reduce the influence of the underlying surface on runoff water temperature.Finally,guided by the basic principle of software engineering,adopted B/S structure,based on the component interfaces,such as SQL Server,Microsoft Office,Ansys,according to the software development process standards,we build visualization platform to realize the simulation of heat transfer process of the underlying surface,as well as the storage,reading,statistics and analysis of the land surface temperature and gradient temperature of the underlying surface.