Influence of manikin movement on temperature stratification in a displacement ventilated room

Temperature stratification generally exists in an indoor environment with floor-level air-supply systems, such as displacement ventilation (DV) and underfloor air distribution (UFAD). The systems with vertical temperature differences possess many advantages over mixing ventilation, including lower energy consumption and better indoor air quality. Some dynamic factors, including the movement of the human body, the door opening and closing processes, can disrupt or weaken the temperature stratification. However, the mechanisms by which these factors affect temperature stratification remain unclear. In this study, a series of experiments was conducted to investigate the temperature stratification of the DV system in an environmental chamber by adopting a moving manikin. We employed temperature stratification stability (TSS) and temperature stratification recovery time (TSRT) to quantify the influence of dynamic factors on temperature stratification. The primary and secondary factors which influencing TSS and TSRT were identified using orthogonal experiments among four important indices, i.e. manikin moving velocity (v), manikin moving duration (t), manikin heat generation intensity (P) and air change rate of the chamber (ACH). Results show factors destruct the mean TSS, ranked from the most to least significant, are v, ACH, P and t, and those for mean TSRT are v, t, P and ACH. In the manikin activity area, TSS increases with the vertical height. Manikin moving velocity exerts a primary effect on temperature stratification. There is a negative correlation between Re number and TSS in our experiment. The area affected by the movement is observed mainly around the manikin, not the whole chamber. The temperature stratification still exists after the termination of the manikin movement, but is relatively weakened. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Temperature stratification exists in indoor environments with floor-level air-supply systems, such as displacement ventilation and underfloor air distribution. Dynamic factors like human movement and door opening processes can disrupt or weaken the temperature stratification, but the mechanisms behind these effects are still unclear. Results from experiments with a moving manikin showed that factors like manikin moving velocity, duration, heat generation, and chamber air change rate significantly impact temperature stratification stability and recovery time.