Study On Thermal Comfort Of Shaded Environment Within Urban Green Open Space In Wuhan

With the impact of climate change and urban construction,outdoor thermal comfort research has received more and more attention.Urban green open space is an important place for carrying public outdoor activities,the comfort of thermal environment directly affects the use of space.More and more studies have confirmed that shade is an important measure to improve outdoor thermal comfort.Therefore,the evaluation standard for thermal comfort,understand the factors affecting human thermal comfort and the difference in thermal comfort of shaded environments with different material space forms is important for better use of shade to improve outdoor thermal comfort.Based on this,the shaded environment of the typical green open spaces in Wuhan in hot summer and cold winter regions was selected as the research object,and the Physical Equivalent Temperature(PET)was used as an objective evaluation index of thermal comfort.The following work was carried out:(1)The study conducted a total of 26 thermal comfort surveys from July to October 2017,and obtained data on microclimate in outdoor shaded environments in summer and autumn in Wuhan(air temperature,relative humidity,globe temperature,and wind speed),and 2252 copies effective questionnaires.The microclimate and thermal comfort differences of the shaded environment in summer and autumn were analyzed and compared.It was found that,in addition to relative humidity,the microclimate differences in different shaded environments in autumn were significantly greater than those in summer.The better the degree of shaded,the lower the mean radiant temperature in the shaded environment.When the surface radiation effect in the afternoon increases,the mean radiant temperature difference in each shaded environment decreases.The diurnal variation of the mean radiation temperature of the shaded environment of the structure is smaller than the shaded environment of the plant.When the planting of greenery is rich,the cooling and humidifying effects of the plant are significant,but the humidity fluctuates greatly.In terms of thermal comfort,people's comfort in autumn is obviously better than summer.Microclimate has an important impact on people's microclimate perception.The specific manifestations are: The influence of relative humidity in autumn on microclimate perception is greater than that in summer,and air temperature is an important factor affecting microclimate perception in summer.Greening is the focus of attention when it comes to improving the outdoor space environment.People prefer plant shade even in hot summer or relatively comfortable autumn.(2)Based on the surveys,the corresponding PET for each questionnaire was calculated.By establishing the relationship between subjective sensation and objective thermal comfort,it was determined that the neutral PET in summer in shaded environment of green open spaces in Wuhan is 23.9?,and the thermal comfort range is 19.2? to 28.5?.The neutral PET in autumn is 21.6?,and the thermal comfort range is 12.5 to 30.7?.The mean radiation temperature was the main factor that affected the thermal comfort of shaded environment in summer and at different periods.The air temperature and mean radiation temperature were the mean factors that affected the thermal comfort of shaded environment in autumn and at different periods.In addition to the negative impact of wind speed on thermal comfort,all other microclimatic factors have a positive effect on thermal comfort.(3)The study statistically analyzed the thermal comfort and microclimate preferences of different populations in the summer and autumn seasons from gender,age,and activity type.The results showed that women's thermal sensitivity was higher than that of men in summer and autumn.In the summer,the elderly are more sensitive to the humidity than the young people.The young and middle-aged are more sensitive to wind speed and sunshine than the elderly.The young people in autumn are more sensitive to heat and sunshine than the elderly.In summer,as people increase their activity,they will more warm.When activity is small,people are less sensitive to humidity.As the amount of activity in the fall increases,people's demand for thermal environment decreases.(4)The study explored the differences in thermal comfort of different material space forms shaded environments,which included shaded,surface types,shaded layer heights,shaded types,and plant different planting patterns and structures.It was found that shading degree,shading layer height,community structure,land surface type,and shading type had a significant effect on PET in summer.In addition to shading types in autumn,other material space forms had a significant effect on the thermal comfort of shaded environment in autumn.What's more,the effect of material space forms on thermal comfort in autumn is greater than in summer.The study reveals the effect of the outdoor shaded environment micro-climate and material space shape on thermal comfort,which provides a reference standard for the evaluation of the thermal comfort of the outdoor shaded environment in Wuhan.In order to provide a theoretical basis for creating a comfortable outdoor environment and building a pleasant living environment.