Investigation of Dynamic Thermal Comfort and Air Velocity Preference in Different Transient Environments in Summer

This research mainly focused on investigating dynamic thermal comfort in transient environments with desk fans. An experiment was conducted during the summer of 2018 in Changsha City. Three step change conditions (34–26–34 °C, 34–28–34 °C, 34–30–34 °C) were conducted with 20 subjects in a chamber room. Subjects can freely adjust desk fans in indoor conditions (26, 28, 30 °C). Thermal perceptions were responded, and physical variables were recorded simultaneously. The results show that overshoot in thermal sensations occurs after temperature down-step change and does not occur after up-step. The steady values of the thermal sensations after up-step change were lower than those in the previous environment before down-step, indicating that thermal sensation is affected by thermal experience before step change. Thermal sensation approached stability more quickly with the desk fan. Air movement preference varied over time and discrepancy occurred between the condition after heating and before cooling exposure. Additionally, desk fans could significantly improve thermal comfort of the subjects after step change.