Effects of Turbulent Air on Human Thermal Sensations in a Warm Isothermal Environment

Abstract

Air movement can provide desirable cooling in "warm" conditions, but it can also cause discomfort. This study focuses on the effects of turbulent air movements on human thermal sensations through investigating the preferred air velocity within the temperature range of 26 degrees C and 30.5 degrees C at two relative humidity levels of 35% and 65%. Subjects in an environmental chamber were allowed to adjust air movement as they liked while answering a series of questions about their thermal comfort and draft sensation. The results show that operative temperature, turbulent intensity and relative humidity have significant effects on preferred velocities, and that there is a wide variation among subjects in their thermal comfort votes. Most subjects can achieve thermal comfort under the experimental conditions after adjusting the air velocity as they like, except at the relative high temperature of 30.5 degrees C. The results also indicate that turbulence may reduce draft risk in neutral-to-warm conditions. The annoying effect caused by the air pressure and its drying effect at higher velocities should not be ignored. A new model of Percentage Dissatisfied at Preferred Velocities (PDV) is presented to predict the percentage of feeling draft in warm isothermal conditions.

Study on dynamic characteristics of natural and mechanical wind in built environment using spectral analysis

“…Arens et al [14] conducted experiments on two groups of airflow with the same average velocity and different fluctuant frequencies, and found that the airflow fluctuating at the frequency range of 0.7-1.0 Hz has more cooling effect. Xia et al [15] found that the airflow fluctuating at frequency range of 0.3-0.5 Hz would produce the strongest cooling effect and could improve the thermal sensation under warmneutral environment, which was consistent with Fanger's conclusions.…”

Relationship between thermal sensation and comfort in non-uniform and dynamic environments

“…Compared with the traditional uniform and steady environment, non-uniform environment produced by personalized ventilation [1,2], task air-conditioning [3][4][5] or heated/cooled seat [6] can thermally satisfy occupants within a much wider room air temperature range, resulting great potentials of energy saving. The fact that human body is more sensitive to cold than warm is confirmed by several well-organized experiments [7,8] and the resulting benefit for energy conservation by providing a dynamic environment with fluctuating air temperature [9] or air movement [10,11] in warm environment is reported. Human responses to non-uniform and dynamic environments are different from the ones to uniform and steady environments and proper assessment of thermal environment is the basis for well design of non-uniform or non-steady environments in buildings.…”

Investigation of transient thermal environments

“…On the other hand, higher air velocity can be accepted as a temperature offset measure in hot and humid conditions [9].…”