Influences Of Outdoor Thermal Environmental Factors On Human Thermal Comfort

With the improvement of people’s life, people begin to spend more space and time on outdoor activities. Thermal comfort is directly related to health, travel and work efficiency of residents. With the frequent heat wave events and increasing urban heat island, outdoor thermal comfort becomes paid gradually attention. Although outdoor thermal comfort studies have been gradually carried out, there still exist the following defects:first, lack of systematic quantitative research on how thermal environmental factors affect human thermal comfort; second, indicators reflecting human thermal comfort has not been standardized, relationship between each indicator is not clear quantitatively; third, lack of domestic basic experimental research, samples were also extremely limited. Therefore, according to the above three points, it is necessary to study influence of environmental factors on outdoor thermal comfort based on domestic climate characteristics.A nearly two years of field measurements and questionnaires survey was carried out on the streets, parks, squares, schools in Changsha, Hunan. Thermal environmental parameters (including air temperature, relative humidity, wind speed and black ball temperature) and subjective thermal reaction of subjects (including thermal sensation vote, thermal comfort vote and thermal acceptability votes) were collected. A total of8150copies of valid samples were collected. By statistical methods, relationships between thermal sensation vote, thermal comfort vote and thermal acceptability vote were established a quantitatively. Then, influence of air temperature, humidity, wind speed, solar radiation on thermal sensation was separately analyzed. By multi-factor analysis of variance, significant degree of each factor on thermal sensation was quantitatively analysis. Last, relationship model including multiple thermal environmental factors was established.The results were as follows:first, thermal sensation, thermal comfort and thermal acceptability presence good correlation between each two, and thermal sensation and thermal comfort showed a parabolic relation, and thermal comfort and thermal acceptability showed a linear relationship. Second, thermal sensation has linear positive correlations with air temperature, solar radiation, and negative correlation with the wind. As air temperature rising1℃, thermal sensation rises0.141scale, and as difference of globe temperature and the air temperature rising1℃, thermal sensation raise0.084scale, and as wind raise lm/s, thermal sensation dropped0.354scale. Influence of humidity on thermal sensation remains to be further studied. Third, air temperature is the most important factor among all the thermal environmental factors with the extent of about65%, and solar radiation followed by the extent of about20%, the degree of influence of the absolute humidity and wind speed are very low, only to less than10%.The results show that the outdoor thermal environment has a significant influence on human thermal comfort, which can be a reliable theoretical basis for accurate assessment of outdoor thermal comfort, then provides a reliable theoretical evidence for creating a comfortable and healthy urban thermal environment.