Variation of temperature stratification during and after the human movement in displacement ventilation

Abstract

Indoor temperature stratification can be weakened or even eliminated by human movement in displacement ventilation (DV). Thus far, the investigations of temperature destratification and stratification recovery during and after indoor human body movement are still very limited. This study investigated the influence of movement velocity (v), movement distance (A), human shoulder breadth (B), indoor heating load (P), and air change rate (ACH) on indoor temperature stratification. The concepts of the dimensionless degree of temperature destratification (φ), time required for temperature destratification (td), and time required for the recovery of temperature stratification (tr) were proposed to evaluate the robustness of such thermal stratification. The Richardson number (Ri) was a suitable dimensionless parameter for assessing the overall effects of influencing factors comprehensively. The results are as follows：(1) For the temperature destratification process during human movement, φ was linearly correlated with Ri number: φ = a × Ri. The symbol a was a dimensionless coefficient determined by boundary conditions. Likewise, there was a positive linear correlation between Ri and td. (2) For the recovery process of temperature stratification after the cessation of human movement, tr was only related to φ and indoor air change rate. tr had a negative relationship with φ when the ACH kept constant. Similarly, tr tended to a constant value when the ACH exceeded 6 h−1 with the constant φ value. This study can guide designers to strengthen the temperature stratified anti-disturbance performance by increasing the supply air volume and supply air temperature in the design stage of DV.