Personalised ventilation: evaluation of different air terminal devices.

The effectiveness of personalized ventilation based on air movement around a room's occupant largely depends on the supply air terminal device or ATD. Five different ATDs were tried and compared. A normal office workplace with a desk and mounted ATDs was simulated in a climate chamber. An office worker was simulated by a breathing thermal manikin. Tests were performed at various air temperatures of 26C and 20C and personalized air temperatures of 20, 23 and 26C provided by the ATD. The flow of personalized air was increased from less than 5 L/s up to 23 L/s. To identify the amount of personalised air inhaled by the manikin, tracer gas was used. The temperature loss from the body parts of the thermal manikin was recorded and correlated to human thermal comfort. The personal exposure effectiveness was increased in proportion to the increase of the airflow rate from the ATD until a constant maximum value was achieved. Any further increase of the airflow rate made no improvement to the personal exposure effectiveness. The highest personal exposure effectiveness was 0.6, achieved by a vertical desk grill followed by an ATD designed as a movable panel in both isothermal and non-isothermal conditions and an airflow rate below 15 L/s. These two ATDs must be combined with another ATD in order to improve occupants' thermal sensation in a warm environment.