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Personalized air conditioning systems are widely used in sleeping environments, where a sleeping human body is always immobile through night. The ventilation performance optimization of air conditioning system becomes necessary, and the influences from different supply air parameters were investigated in this study, including supply air flow rate and temperature, supply air outlet height and fresh air flow rate. To understand the effects of supply air parameters on ventilation performance, the occupied zone air flow field, air change efficiency, CO2 concentrations and CO2 concentrations distributions inside the room were numerically studied. It was indicated that placing the supply air outlet at lower levels of 1.1 and 0.8 m could directly deliver cooling air to the thermal manikin, leading to a much higher air change efficiency of around 70%. The air temperature of the occupied zone could not be well cooled down for the supply air outlet at a height of 0.8 m. Meanwhile, the higher supply air flow rate may cause significant draft risk. Finally, considering the ventilation performance and draft risk, a set of the supply parameters is suggested for this personalized air conditioning system. [ABSTRACT FROM AUTHOR]

It was revealed in a previous related study that for an air conditioning (A/C) system used in a sleeping environment, the height of its supply air outlet would significantly affect its ventilation performance in terms of effectiveness. To further examine the underlying reasons of the differences in ventilation performance, the air flow field, distributions of mean age of air, air change efficiency and distributions of CO 2 concentrations inside an experimental bedroom were numerically studied using CFD method under five different settings, where its supply air outlet was positioned at 5 different heights. The study results suggested that positing a supply air outlet at a lower level was effective in both saving energy and removing the exhaled CO 2 in a breathing zone, and when a supply outlet was positioned at a higher level, less CO 2 was removed from the region near the mouth of a sleeper. [ABSTRACT FROM AUTHOR]