Thermal perception of non-uniform and dynamic air-conditioned environment in the elderly

Due to the decline of the elderly's thermophysiology, the elderly is more sensitive to changes in airflow. Traditional thermal sensation equation was a steady-state model only based on the average of surrounding thermal environment parameters, which cannot describe the thermal perception to the spatial uniformity and temporal fluctuation of the parameters. To characterize the thermal perception of non-uniform and dynamic air-conditioned environments in the elderly, this study determined the characteristics of thermal environment at twenty-four monitoring points (three heights and eight directions) around the elderly through laboratory test. Seven elderly participated in the experiment and were asked to fill in the questionnaire to obtain thermal perception. Different typical airflow with 26 °C set temperature of air-conditioner were set as the measuring conditions. Uniformity and fluctuation indexes were proposed to qualify the spatial and temporal distribution. The results showed that the average of the parameters was basically in the acceptable comfort zone. Through establishing the thermal sensation model based on the average, uniformity, and fluctuation indexes, thermal sensations were only significantly affected by fluctuation of temperature, velocity uniformity, turbulence, and average relative humidity. Compared to traditional model, established model can not only depict the elderly's strong perception of temperature change by temperature fluctuation index, but also refine the elderly's relatively weak perception of static average velocity into a strong perception of the velocity uniformity and turbulence. The R square of this model was 0.153 greater than that of traditional model.