Outdoor Thermal Comfort Study For A Whole Year In Guangzhou

With the rapid development of urbanization in China,and the density growth of urban population,building and traffic,the urban thermal environment is becoming worse.How to create a healthy and comfortable outdoor environment is important for the sustainable development of society,which requires accurate outdoor thermal comfort model to guide.However,the research on outdoor thermal comfort in China is insufficient,and the thermal comfort model is relatively lack,so the research on outdoor thermal environment still use models established in Europe and America area.However,because of people's thermal adaptability,the adaptability of outdoor thermal comfort models established in European and American area need to be verified in our country.Therefore,it is imperative to study the outdoor thermal comfort in China.We made a research on outdoor thermal comfort in Guangzhou from June 2016 to May 2017,through recording the environment parameters and making questionnaire survey at the same time.Finally,a total of 4675 effective questionnaires have been obtained.Firstly,this paper analyzes the thermal comfort and thermal acceptable degree in each season in Guangzhou.We find that the thermal comfort slightly hot in spring,the worst in summer,the best in autumn,and half of the time people feel comfortable in winter.People tend to accept warmer environment in winter,cooler environment in summer,and neutral or warmer environment in transition season.Moreover,this paper analyzes the relationship between thermal sensation and thermal comfort.The results show that no matter the human body is in thermal balance or not,people can feel comfortable.Secondly,this paper verifies the adaptability of PET(Physiological Equivalent Temperature),PMV(Predicted Mean Vote),SET~*(Standard Effective Temperature~*)and UTCI(Universal Thermal Climate Index)in Guangzhou.The results show that the adaptability of PET is the best,which is almost consistent with actual MTSV(Mean Thermal since the Vote)between 12? and 36?.However,in the colder environment,PET overestimates the cold feeling of people.On the contrary,in the hotter environment,PET overestimates the hot feeling of people.PMV overestimates the actual MTSV about 0.3 between-1.0 and 3.0,and when PMV<-1.5,PMV greatly overestimates the cold sensation of people.SET~* overestimates the change of people's thermal sensation,which overestimates people's MTSV when SET~*>17?,and underestimates the MTSV value when SET~*<17?.UTCI generally overestimates people's MTSV.The deviation between the TSV predicted by UTCI and the actual MTSV increases with the decrease of UTCI when UTCI<26?,and when UTCI>32?,UTCI overestimates people's actual thermal sensation about half of the thermal class.Thirdly,this paper revises the adaptability of PET,PMV,SET~* and UTCI,including thermal neutral value,thermal class and thermal preference.We find that the neutral values obtained by descriptive analysis would be bigger in hot season than in cool or clod season,but the neutral values obtained by probit analysis are contrary.The thermal comfort zones in the year of PET,PMV,SET~* and UTCI are 18.6~ 24.4?,-0.3 ~ 0.8,24.2 ~29.1?,20.0~25.5? respectively.the thermal comfort zone of PET is closest to its original comfort zone,and the thermal comfort zone of PMV and SET~* are both higher than their original comfort zones,and the lower limit value of UTCI is 11? higher than its original comfort zone.Besides,the preference value of each model in spring,summer and autumn are below their neutral values,and the preference value in summer is the largest difference with its neutral value,while the preference value in winter is higher than its neutral value.Finally,this paper analyzes the effects of thermal comfort factors on human thermal sensation.We find that the influence of air temperature on human thermal sensation is the biggest(When air temperature rises 5? on average,human thermal sensation will rise one thermal class),followed by wind speed,and relative humidity is the smallest.In addition,by multiple linear stepwise regression analysis,this paper establishes the outdoor thermal comfort empirical models in the year and each season in Guangzhou,so that we can know the relationship between thermal comfort factors and TSV(Thermal Sensation Vote).To sum up,this paper analyses the present outdoor thermal comfort situation,verifies and corrects the adaptability of PET,PMV,SET~* and UTCI,establishes the outdoor thermal comfort empirical models,in Guangzhou.This study has certain reference value for city planning and holding outdoor activities in Guangzhou,and has certain academic value for the further outdoor thermal comfort study in domestic and even in subtropical areas.