Effects of ceiling exhaust location on thermal comfort and age of air in room under impinging jet supply scheme

The impinging jet ventilation has addressed extensive attention in recent years because it can be used as both cooling and heating modes, which greatly affect the resultant indoor environment like thermal comfort and air quality. Previous works have explored the effects of geometrical parameters (e.g., supply duct shape and discharge height) while leaving the ceiling exhaust location unexplored yet. This study aims to investigate the effects of ceiling exhaust location on thermal comfort and mean age of air (MAA) under such impinging jet cooling pattern. Firstly, two locations both far from a heating source are compared (i.e. exhaust located on the same side as or the opposite of the inlet, named Room-U and Room-D respectively). Secondly, locating the exhaust right above the heating source (named Room-M) is compared with Room-U and Room-D. The results indicate that Room-M has the least neutral predictive mean vote (PMV) and the longest MAA. Thirdly, the steps to locate ceiling exhaust near the thermal plume are proposed and verified by applying them to improve the PMV of Room-M further (including a case with three heat sources). PMV decreases from 0.35 of Room-M to 0.28 of the further improved under the case with a sole source located on the floor center, and decreases from 0.88 of Room-M to 0.84 of an improved case when there are three sources uniformly distributed on the floor. In summary, locating the ceiling exhaust near the thermal plume removes heat efficiently in respect of cooling while locating it on the ceiling center may result in a longer age of air.