A case study of the energy saving potential of stratum ventilation

Stratum ventilation is a recently proposed air distribution system. It works by creating a layer of fresher air in the occupants' breathing zone. This is achieved by placing large supply inlets along the side-walls of the room just above the height of the occupants. Fresh air is emitted into the room and gradually loses momentum. The supply velocity is sufficiently strong to provide fresh air directly to the occupants without space mixing. This technique has been proposed as a method to cope with elevated indoor temperatures in summer, which is required by several governments in East Asia for carbon reduction. Previous studies have shown that stratum ventilation provides good indoor air quality (IAQ) and thermal comfort. This paper is intended to demonstrate the energy saving potential of stratum ventilation by comparing its energy performance with that of displacement ventilation. A typical classroom is used as an example. Computational fluid dynamics (CFD) simulations were conducted to study airflow and pollutant transport in the classroom. The air quality and comfort performance (PPD, PD and local mean air age in the occupied zone) of the stratum case were found to be comparable to those of displacement ventilation. In addition, energy saving of the stratum ventilation case, under the current set-up, was found to be significant.