Effects of air inlet or outlet position of a fan coil unit ventilation system on smoke movement and fire severity

Abstract Air conditioning engineers design the inlet or outlet position of a fan coil unit (FCU) system according to thermal comfort and cost. However, the effect of the position on fire growth has not been considered. In this study, the effect of the relative inlet and outlet positions was investigated. Thirty cases were simulated using fire dynamics simulator (FDS). The simulation results revealed that the air inlet and outlet positions influence the smoke movement, doorway temperature and time to flashover. The air inlet is best installed near the door because the downward flowing cold air can cool the hot smoke exiting from the door. The air outlet positioned far from the doorway efficiently enables the smoky air to move outward, while it positioned near the doorway exhausts some fresh air. Furthermore, the air outlet position has a larger influence on flashover than the air inlet position. The air outlet immediately exhausts the smoke.