Multi Dimensional Evaluation Of Outdoor Thermal Comfort In Severe Cold City

Comfortable outdoor space can not only improve people’s quality of life and extend the time people spend in outdoor,but also make the city more energetic and attractive.Recently,the outdoor thermal comfort has been paid more attention by urban planners and architects,which becomes a key issue of scholars in research field.It is known that kinds of shortages do happen to evaluate the outdoor thermal comfort intuitively with single meteorological parameters(wind speed,temperature,etc.),so thermal comfort indexes(UTCI,PET,SET*)are used internationally.Thermal comfort indexes can explain the comprehensive thermal environment’s impacts on human body,but the series of people’s subjective feelings are still lack of direct interpretations.In addition,the outdoor thermal comfort differs by different locations.At present,a lot of relative research have been carried out in the tropical,subtropical and temperate climate areas,and more systematic research in severely cold areas are needed and the database should be expended.This paper firstly divided the four seasons with the method of 5 days-mean temperature,based on the data of typical weather year of Harbin,and a 1 year field measurement and questionnaire survey was carried out in a series of selected experiment sites,such as squares,parks and pedestrian streets etc.Secondly,based on the results of field measurement and questionnaire survey,statistics analysis was carried out to analyze the field measurement and questionnaire survey data,including the outdoor environment seasonal changes,the sensitivity and relevance of thermal comfort,and the relationships between different subjective and objective influencing factors in different seasons.Finally,based on the forecast accuracy of the frequentlyused outdoor thermal comfort indexes,the applicability of the thermal comfort indexes in different seasons was quantified,and 3 subjective evaluation indexes(thermal sensation,thermal comfort,acceptability range)was proposed as the quantitative standard,based on which the multi-dimensional evaluation system of urban outdoor thermal comfort in severely cold areas was established,which is expected to provide references for the design and improvement of outdoor thermal environment in severely cold areas.According to the analysis of thermal sensation and thermal comfort,it was found that the thermal sensation and thermal comfort showed linearity relationship in winter in Harbin,while quadratic function relationships were shown in other seasons;in addition,the most comfort thermal sensation in spring and autumn was found to be “neutral”,while that in summer and winter is “slightly cold” and “slightly warm” respectively,which should be affected by thermal experience,preference and adaptation.According to the results of the relevance between thermal sensation and thermal comfort indexes,the slope in autumn was the steepest,meaning that people’s thermal comfort was much more sensitive to thermal sensation in autumn.This paper also carried out analysis of the relationships of thermal sensation,thermal comfort,acceptability and thermal comfort indexes(PET,SET* and UTCI).The neutral thermal sensation ranges,thermal comfort and acceptability range in different seasons were quantified.By comparing with former research results in other cities(Taiwan,Guangzhou and Europe),the range of neutral PET in winter in Harbin is lower in boundary value,which indicates the citizens in Harbin have more tolerance with coldness.The forecast accuracies of different indexes in different seasons were calculated,and it showed that UTCI is the highest in summer(62.3%)while PET in other seasons(spring,autumn and winter)is the highest(88.1%,68.9% and 61.1% respectively).Based on the above work,by quantifying 3 subjective evaluation indexes(thermal sensation,thermal comfort,acceptability range),the multi-dimensional outdoor thermal comfort evaluation method was putted forward.