| Cities maintain their carrying capacity by expanding into the suburbs or increasing the density and height of buildings inward to ensure the continuation of the urbanization process.However,many artificial environments affect the thermal comfort of outdoor spaces due to underlying surface changes,which are not conducive to the sustainable development of cities.City square is the main outdoor space for citizens’ activities,and the thermal comfort of square directly affects the participation and health of citizens.Thermal comfort has obvious regional characteristics,and the adaptability of thermal comfort indicators to both Dwa climate and cold2 A climate areas in China is yet to be tested.In addition,there is a lack of strategies to adapt the thermal comfort transformation of city squares to other city squares in the same climate zone.Based on the above,it is urgent to act on the thermal comfort study of urban squares in Dalian.In this paper,Dalian city square is selected as the research object,and three typical city squares are screened according to the redefinition and spatial morphological characteristics of city squares.Field measurements,questionnaire research,statistical analysis and numerical simulation are used to study the summer thermal environment,and the common indexes of outdoor thermal comfort SET*,PET and UTCI are selected for correction and evaluation.The research results show that the thermal environment in Dalian is more comfortable in summer,and the citizens of Dalian are more likely to accept a cooler environment and prefer a cooler climate in summer;the neutral and preferred temperature values of SET*,PET and UTCI are ranked from smallest to largest as SET*<PET<UTCI;the acceptable temperature range is larger than the neutral temperature range,which are 2.1℃,2.1 ℃ and 4.1 ℃;for example,the range of SET* is lower than the original model,PET is closer to the original model,and UTCI is narrower than the original model;among the predictive ability of the three indicators,PET has the best adaptability,followed by SET* and UTCI.The numerical simulation of the city square using ENVI-met found that the thermal comfort of the city square was the worst at 14:00,and the thermal level was "hot".The worst thermal comfort was found in Tiger Beach Civic Square during the simulation time,followed by Navy Square and Zhongshan Square.The PET was high on the south and north sides of the buildings near the square,while the PET was low on the west and east sides of the buildings.The effect of water bodies on the thermal comfort of city squares is different.Meanwhile,water has no significant effect on the mean radiation temperature.Trees have a more vital ability to reduce PET than lawns.Lawns reduce wind speed.In the case of the complete absence of building shadows,the cooling effect of large lawns on PET is not significant,and the cooling impact of lawns on air temperature is not as strong as that on the mean radiation temperature.The article argues that the following three strategies can be adopted for the optimization of thermal comfort in urban plazas in cold 2A areas: choosing materials with an albedo of 0.6 for hard paving,setting up a large area of concentrated water,and alternately laying two types of hard materials with a more focused area.In summary,this paper analyzes the thermal comfort of Dalian city square,corrects each thermal benchmark and a thermal class of SET*,PET and UTCI,tests the applicability of SET*,PET and UTCI with respect to Dalian city,and optimizes and tests the thermal comfort of typical city squares.The results of this study provide scientific data and reference values for outdoor thermal comfort research in Dwa climate or cold-2A climate areas.They have guiding significance for designers to design outdoor spaces,contributing to creating more livable and vibrant sustainable urban square designs. |
