The destructive time of temperature stratification during human movement and the recovery time after the human movement in the displacement ventilation system

School of Mechanical Engineering, Tongji University, Shanghai 201804, China

^* Corresponding author: gaonaiping@tongji.edu.cn

Abstract

Many factors such as human movement can weaken indoor temperature stratification and lead to the advantages of the displacement ventilation (DV) disappearing. Yet the investigation for the stratified destructive time during the human movement and the recovery time after human movement stops are still meagre so far. The concepts of dynamic steady-state and static steady-state are proposed to compute the stratified destructive time(T_b). The isothermal surface of 295K is engaged to explain the variation of T_b. At last, the stratified restoring time(T_c) after human movement stops are inquiries in our paper. The conclusion is as follows: Firstly, the value of T_b reaches a maximum value at the moving velocity of 1m/s, since the isothermal surface of 295K starts to be broken when the moving human velocity reaches 1.0m/s. However, the values of T_b remains about 50s for the human moving velocities between 2.4m/s to 4.0m/s. The reason is that the temperature stratification are disappear completely when the human moving velocity exceeds 2.4m/s. Finally, The Tc keeps in the 250s when the human moving velocity is between 1.2m/s to 2.0m/s. The current study provides new insights into the design of the DV system.