Effects of operation parameters on performances of stratum ventilation for heating mode

Abstract

Stratum ventilation is more energy-efficient as compared with mixing ventilation for cooling applications. However, due to the short development history of stratum ventilation, few studies on its heating applications are available. The heating operation of stratum ventilation is different from the cooling operation due to the distinct airflow patterns. This study comprehensively investigates the effects of the operation parameters on heating performances of stratum ventilation, using experimentally validated Computational Fluid Dynamics (CFD) simulations. The operation parameters include controllable supply vane angle, supply airflow rate and supply air temperature, and uncontrollable outdoor weather condition. The ventilation performance indices adopt local mean age of air (LMAA), CO2 removal efficiency (CRE), Predicted Mean Vote (PMV), vertical air temperature difference between head and ankle levels (ΔT) and energy utilization coefficient (EUC). By evaluating the individual effects of the operation parameters on the ventilation performances, the relative importance (i.e., relative sensitivity) of the operation parameters for each ventilation performance is identified. By comparing the individual effects and combined effects of the operation parameters on the ventilation performances, it is found that the variations of LMAA, CRE, PMV, ΔT and EUC caused by the combined effects can be accounted by the corresponding most important operation parameters by 86.5%, 85.6%, 78.8%, 65.7% and 70.2% respectively. Moreover, the outdoor weather condition does not significantly affect LMAA, CRE and EUC, but can transfer PMV and ΔT to discomfort level. Lastly, to facilitate heating applications of stratum ventilation, the constant-air-volume system is recommended and a simplified operation strategy is proposed.