Investigation in performance of a hybrid under-floor air distribution with improved desk displacement ventilation system in a small office

In this article, combining the under-floor air distribution (UFAD) system with improved desk displacement ventilation (DDV+), we tried to solve the barriers of both systems. Computational fluid dynamics (CFD) was employed for evaluation of the local thermal discomfort, the indoor air quality (IAQ), general thermal comfort indices, cooling energy saving and velocity/temperature gradient around the occupants. Then, the performance of the integration was compared with standalone UFAD and DDV+ systems. Three possible scenarios were considered for the air volume division between inlet diffusers in the hybrid system. As the results showed the optimum case was obtained by combining UFAD and DDV+ diffusers at 70% and 30% of total air volume, respectively. Improvements in IAQ, zero possibility of draft risk around occupants' ankles, suitable temperature/velocity profile around the occupants' heads and improvements in thermal sensation were achieved by a well-designed UFAD-DDV+ system with 16.6% reduction in energy consumption compared to a mixing ventilation system.