Investigation of transient thermal environments

Human beings are commonly exposed to transient thermal environments in their daily life. But most of the studies on indoor thermal environment have been conducted under steady-state conditions. The aim of this paper is to summarize the investigation on human responses to transient thermal environment carried out by the indoor environment group at Tsinghua University, and to predict the possibility of using their research findings in practice. Human responses to transients have some special characteristics, which could be beneficial to environmental control. Air movement is especially effective at realizing a transient thermal environment, offsetting higher air temperature or operative temperature in warm climates. Based on the analysis of measured data, the characteristics of air movement outdoors are different from artificial air supply such as fans or air supply outlets, in the probability distribution of their velocities, turbulence intensity, and power spectrum. Based on subjective experiments, it is evident that artificial air movement, which is mainly simulated with outdoor airflow characteristics, has the highest occupant preference in warm conditions. Experimentally simulated air movement improves not only whole-body cooling, but also local cooling as from personal air supplies. Finally, it is important that introducing simulated natural air movement into the space in warm or hot conditions could significantly decrease the buildingʹs energy consumption.