Study On Human Dynamic Thermal Comfort Under Different Walking Metabolic Levels In Guangzhou

The continuous progress of urbanization promotes people to improve the requirements of living standards.Because of production and life,people have to stay indoors for a long time,and more and more abundant leisure activities prefer to be carried out outdoors,which leads people to pay more and more attention to indoor and outdoor thermal comfort.There are a limited number of studies on the thermal comfort experienced by people while they walk,even though this state of motion is most common for daily commuting in modern societies.Whether humans are in an idle state,walking,or engaged in another type of movement,metabolic activity is the key influential factor in comfort.The predicted mean vote(PMV)model,the prevalent thermal comfort index,is restricted in terms of the accurate prediction of dynamic change in the thermal environment,such as that associated with walking.Therefore,this study explores the changes of thermal comfort in the dynamic process of walking,and improves the thermal comfort index used in the dynamic process.This provides the guidance basis for the formulation of human movement norms and urban planning.This survey was conducted in the indoor and outdoor spaces of Guangzhou from march to April 2019 and June to July 2019,respectively,through the combination of environmental parameter measurement,dynamic physiological index monitoring and subjective questionnaire survey.A total of 30 subjects were recruited to refer to different metabolic conditions with four different uniform walking speeds.16 groups of walking experiments were carried out(4 groups of experiments were repeated at each speed),and 480 valid questionnaires were recovered.In this paper,the collected environmental parameters,subjective thermal sensation voting and dynamic physiological index data are statistically analyzed to obtain the changes of human thermal comfort during dynamic walking in different spaces,and to reveal the corresponding relationship between physiological index changes and subjective thermal sensation voting.The results show that the environmental parameters of indoor space are relatively stable,while the environmental parameters in transition space fluctuate greatly,among which the fluctuation of ambient air velocity is the most obvious,and the influence on human thermal comfort is significant.In the observation of the change of metabolic rate of dynamic human body,it is found that the human body usually takes 3-5 minutes to reach the new metabolic level when walking indoors,and 9-11 minutes in the transition space,which is not synchronized with the change of human body’s thermal sensation.The change of thermal sensation lags behind the change of physiological index.Secondly,when studying the influence of disturbed wind speed on thermal comfort,it can be found that the wind speed fluctuation in transition space is obvious.If the influence of turbulent wind is ignored,the maximum heat storage of dynamic human body will be overestimated by about 20.Moreover,this paper explores the comfortable walking speed and obtains the range of comfortable walking speed in different test space.Thirdly,the adaptability of PMV、SET*、PET and UTCI thermal index in evaluating dynamic thermal comfort is analyzed and verified.Results show that all thermal models can not accurately evaluate thermal comfort in continuous motion under different metabolic conditions,and eliminate the possibility of PMV in evaluating dynamic thermal comfort.Finally,this paper improves the above thermal index model to make it suitable for the evaluation of human dynamic thermal comfort in the research area of this paper,obtains the improved thermal index model α PET 、 α UTCI and α SET,and analyzes the corresponding thermal index values of different thermal grades.So that whether the subjects were resting or walking,the thermal sensation can be estimated by simply calculating the thermal index.This study reveals the law of human thermal comfort during dynamic walking and provides guidance for human scientific walking.Moreover,the improvements of thermal comfort model in this paper extend the applicable evaluation scope,and establish the dynamic thermal comfort experience model in Guangzhou area.The results of this study provide guidance for urban planning and citizen travel in Guangzhou area,and have reference value for the future research of thermal comfort model at home and abroad.