Impact Of The Ground Floor Overhead On The Summer Outdoor Thermal Environment In Chongqing Settlements

Rapid urbanization has led to the rapid growth of urban population,Due to complex landform,shortage of construction land,division of urban areas by mountains and rivers,dense residential buildings and uncoordinated layout of buildings,the surface ventilation resistance coefficient is large,so the outdoor thermal environment of residential areas in Chongqing is becoming worse and worse.In order to study the influence mechanism of the thermal environment of ground-floor elevated residential areas,the paper adopts the method of combining field measurement and numerical simulation to conduct the following researches on the ground-floor elevated residential areas in Chongqing.Firstly,the paper studies the present situation of ground-floor elevation of nine residential buildings in central urban areas of Chongqing,and selects a typical residential area in Chongqing as the subject.The outdoor thermal environmental parameters,such as air temperature,relative humidity,wind speed and black globe temperature at pedestrian height in July 2019 are measured so as to obtain the thermal environment characteristics of the residential area in summer.Meanwhile,it selects the evaluation index suitable for the outdoor thermal environment of Chongqing residential area to evaluate its outdoor thermal environment level.Secondly,based on the PHOENICS simulation platform,the paper establishes the spatial model of typical residential areas in Chongqing,selects the convective heat transfer model suitable for the outdoor thermal environment,and uses the measured data as the boundary conditions and verification basis to verify the accuracy of the simulation results.It selects different elevation positions and elevation rates,and conducts a simulation and prediction analysis of the thermal environment of the ground-floor elevated residential area on the basis of the above model.It is found that when the elevated floor is located at both ends of the building,the cooling effect of the residential area is the best,and the proportion of wind comfort zone area increases with the increase of elevation rate.Thirdly,the paper selects four common building layouts in Chongqing(determinant,alternate determinant,point group,wall clamp)and nine residential areas with different plot ratios and building densities.Based on the above platform and model,it studies the change characteristics of air dry-bulb temperature,air relative humidity,wind speed,wet bulb globe temperature and other parameters so as to explore the improvement effect of different factors on residential thermal environment.The results show that the cooling effect of the ground-floor elevation of the wall clamp layout building is the best,and the effect of ground-floor elevation on the thermal environment of the residential area with low plot ratio or high building density is better.Finally,based on the above results,the paper conducts a case study of a residential area in Shapingba District of Chongqing,and optimizes and adjusts the ground-floor elevation of the residential area.The results show that the temperature of the residential area decreases by about 1℃,and the wet bulb globe temperature decreases by about 2℃in summer.Through the above research,the paper reveals the influence of factors such as elevation position,elevation rate,building layout,building density and plot ratio on the outdoor thermal environment of the ground-floor elevated residential areas in Chongqing in summer,which can provide a strong support for the design and planning of groundfloor elevation of residential buildings in Chongqing and play a guiding role in improving the microclimate of the residential area.