| With the rapid development of cities,the global climate environment is in a changing state.Global warming intensifies the deterioration of urban thermal environment.Since the outbreak of COVID-19,people’s yearning for good outdoor climate has become more urgent.But in the outdoor space of old city blocks,due to the aging of facilities and disrepair,many old urban areas have more prominent thermal environment problems.Therefore,from the perspective of optimizing the block thermal environment,this paper discusses the spatial form optimization of Huaihe Road pedestrian block,in order to provide theoretical suggestions for the planning and design of commercial blocks in the old city.Firstly,on the basis of summarizing the relevant research on outdoor thermal comfort of urban blocks at home and abroad,this study combs and evaluates the current situation of thermal comfort of Huaihe Road pedestrian block;Secondly,through correlation analysis,regression analysis and other methods to screen the relevant spatial form indicators affecting the urban thermal environment,and combined with the current situation of the old city commercial block in Hefei,this paper constructs the original model of the typical commercial block,and discusses the influence mechanism of the block spatial form on the thermal environment of the old city commercial block from four aspects: the average building height of the block,the average height width ratio of the street,the green coverage rate and the underlying surface material;Finally,the spatial form optimization strategy of Huaihe Road pedestrian block is determined from the planning and application level.The main results are as follows:（1）Distribution characteristics of thermal environment in Huaihe Road pedestrian blockAs for the overall thermal environment of the block,the pedestrian height of Huaihe Road pedestrian block has a strong thermal load at 14:00 in summer,and the overall thermal environment is poor.The regional average PET value reaches 52.53 ℃ and the maximum PET value reaches 69.17 ℃.The North-South street and the interior of enclosed buildings are the areas with the largest heat load,while the areas with relatively high thermal comfort are mainly distributed in the areas with dense vegetation and the areas covered by building shadows.In terms of the thermal environment of the 15 building clusters divided into blocks,the thermal environment of clusters 1,2,3,8 and 11 is the worst,with an average PET value of more than 54 ℃,reaching the "extremely hot" level,accounting for 33.3%.There are 9 "hot clusters",accounting for 60% of the remaining "hot clusters".The analysis shows that the average PET values of all clusters have reached the "hot" level or above,and the overall thermal environment of the block needs to be improved.（2）Spatial form index affecting block thermal environmentThere is a correlation between block space form and block environment.By analyzing the current characteristics of the urban thermal environment and combing the relevant literature,the internal and external indicators of the block are analyzed respectively,and finally 10 spatial form indicators of the block are determined.Through correlation analysis and regression analysis,the results show that the impact of four indicators,including the average building height of the block,the average height width ratio of the street,green coverage and the material of the underlying surface,is more obvious.Through further regression analysis,it can be seen that the average building height of the block,the average height width ratio of the street and the greening coverage rate will have a significant negative impact on the average PET;The reflectivity of the underlying surface material will have a significant positive impact on the average PET.（3）Influence mechanism of block space form on thermal environmentThe formation of the outdoor thermal environment of the old city commercial block is a continuous development,complex and changeable process,which is composed of internal and external factors.The average building height of the block and the average height width ratio of the street are the internal factors affecting the outdoor thermal comfort of the commercial block in the old city.These two factors change the ventilation conditions of the street by affecting the air pressure difference between the buildings.At the same time,they will also have an important impact on the street shading effect.Both of them jointly affect the general direction of the development of the outdoor thermal environment of the block;Green coverage and underlying surface material are the external direct factors affecting the outdoor thermal comfort of the commercial block in the old city.The plane greening and vertical greening of the block will have an important impact on the humidity and temperature of the block,while the underlying surface material will directly affect the heat load near the ground of the block.The above four factors are interactive coupling,interaction and interaction,which will affect the outdoor thermal comfort of the block to varying degrees.The differences between these factors constitute the different regional microclimate and thermal environment of different urban commercial blocks.（4）Optimization strategy of spatial form of old city commercial blockBased on the above evaluation simulation and analysis of Huaihe Road pedestrian block in Hefei,this paper puts forward the spatial form optimization strategy of old city commercial block to improve the thermal environment conditions from the following three aspects.First of all,for the block form,we should pay attention to the control of the overall space form of the block and guide the highly diversified layout of block buildings.Secondly,for the street form,it is suggested that the streets in the commercial area should be constructed by classification and focus on the construction of open main commercial streets.The recommended height width ratio of the main street should be between 1-2,and the maximum height width ratio should not exceed 3.At the same time,with the construction of compact commercial inner street,it is recommended that the height width ratio of commercial inner street should be greater than or equal to 3,but not more than 6.Finally,in the future,it is suggested to measure the greening level of the block from the two dimensions of plane greening and vertical greening.The two greening forms should be comprehensively considered,overall layout and synchronous implementation.And strongly advocate the use of non endothermic ground with corresponding pavement technology to comprehensively improve the thermal environment of commercial blocks from many aspects.Figure [28] table [27] reference [81]... |
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