Ventilation Performance of Ceiling-Supplied Displacement Ventilation in Medium-Sized Office Room tested by Full-Scale Model Experiment. Part 1 Effect of Supply Air Conditions and Number of Occupants on Temperature and Human-Originated Contaminant Concentration Distributions

After the disaster of COVID-19, the displacement ventilation is in the spotlight, because of the high ventilation efficiency for the human-originated contaminant including droplet nuclei. However, the large diffusers for displacement ventilation tend to be avoided due to the high cost including installation and large floor area. On the other hand, the ceiling-supplied ventilation has many merits. In this paper, the ventilation efficiency of the ceiling-supplied displacement ventilation using developed supply diffuser units was examined by the full-scaled model experiment for medium-sized offices. The temperature and CO2 concentration emitted from person simulators as a tracer gas were measured, and the effects of air supply conditions and the number of occupants on the temperature and CO2 distribution were investigated. As a results, it was turned out that this ceiling-supplied displacement ventilation system has high ventilation efficiency and the normalized concentration of 0.5 can be obtained. Additionally, it is proved that the supply air velocity is an important parameter to determine the ventilation efficiency, and even if the occupant number is rather small, the ventilation efficiency is kept sufficiently good. Overall, it can be said that the ventilation efficiency of ceiling-supplied displacement ventilation is high and practical even in medium- sized office rooms.