Comparison study of contaminant distribution and indoor air quality in large-height spaces between impinging jet and mixing ventilation systems in heating mode

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Numerical simulations are performed to predict the spatial distributions of indoor gaseous contaminant and aerosol particles (represented by the CO2 produced by human respiration and the resuspended 2.5 μm particles caused by occupants’ walking, respectively) concentration in a large-height space equipped with impinging jet ventilation (IJV) and mixing ventilation (MV) systems in heating modes. The local age of air, contaminant concentration of the breathing zone and ventilation efficiency for the removal of contaminants are compared between the IJV and MV rooms for both the constant volume (CAV) and variable volume (VAV) systems with different outdoor temperatures. The numerical results indicate that the mean age of air in the breathing zone of IJV is about 37–47% less than that of MV due to the different airflow patterns. Both the CO2 and 2.5 μm particles distribute uniformly in the IJV room for the CAV and VAV systems, but the CO2 is mainly distributed in the middle region of the room height and the 2.5 μm particles concentrate at the floor level away from the exterior wall in the studied MV room, which results in the contaminant concentrations of the breathing zone in most studied cases of IJV being lower than those in MV. The results also show that the ventilation efficiency in the IJV is higher than that in the MV with the same supply and exhaust configurations of this study, suggesting that the former is more advantageous in providing good indoor air quality (IAQ) than the latter.