The Human Body Thermal Comfort Objective Evaluation Study

In the study on human thermal comfort, the evaluation of thermal comfort is an important basis. Up to now, human thermal comfort is usually evaluated using subjective evaluation method (with a thermal comfort questionnaire). The subjective evaluation method is reliable and simple at most occasions. However, its evaluation result depends on subjects'judgments, therefore, the method is influenced by human subjective factors.Human mean skin temperature (MST) was closely related to thermal comfort and thermal sensation. Moreover, measurement of MST is simple. Therefore, in this study, MST was proposed as an objective index to evaluate human thermal comfort. This paper established an objective evaluation method of thermal comfort based on human MST. In this paper, analysis of human heart rate variability (HRV) was performed to provide a physiological proof for MST as an objective evaluation index of thermal comfort. Based on the proof, various MST calculation methods were evaluated, and the optimal calculation method was obtained. According to the MST samples calculated with the optimal calculation method, subjects'thermal comfort levels were evaluated, and a universal evaluation method was proposed. At last, application of the objective evaluation of thermal comfort based on human MST was discussed.The present work was described as follows.33 subjects'skin temperatures and HRV were measured at different environment temperatures (21~30°C). Also, their thermal sensation and thermal comfort were investigated with subjective questionnaire.Related with thermoregulation, the mechanism of human thermal comfort was discussed based on analysis of HRV. The results indicate that MST can be taken as an objective index to evaluate thermal comfort.The existing 26 types of MST calculation methods (the maximum of measurement sites is 17) were evaluated, and the most suitable calculation method of mean skin temperature for evaluation of human thermal comfort was obtained. Also, a new MST calculation method was proposed according to the distribution and change of 21 local skin temperatures. Subjects'thermal comfort was divided into three levels, including cold discomfort, comfort and warm discomfort. Based on the subjects'MST at each level, an evaluation rule of thermal comfort was obtained using Mahalanobis distance discrimination. The results indicated that most subjects'thermal comfort levels were correctly evaluated according to the rule, especially for the comfort level, the accuracy reached 90%.Based on the evaluation results of thermal comfort using MST, the indoor air diffusion performance of a floor-standing type air-conditioner was evaluated and the best inclination angles of the vanes in the outlet was determined for an optimal air diffusion. At last, the future work was presented.This study indicates that human MST can be used as a reasonable and effective objective index for evaluation of thermal comfort. The evaluation result does not depend on subjects'subjective judge on thermal comfort. Moreover, it relates to human physiological state, thus, can provide a basis for study on the mechanism of thermal comfort.