Experimental evaluation of an intermittent air supply system – Part 1: Thermal comfort and ventilation efficiency measurements

• Intermittent air jet strategy simulates some properties of natural wind: unsteady high-low velocity frequencies.
• The measured PMV is close to neutral in both warm and neutral to slightly cool environments with a reduced draft risk.
• The resulting ventilation has local air change index >1, air change rate of 3.74 h−1, and ventilation efficiency >50%.
• The system provides an effective airflow rate of 8 l/s when it is set to operate with an intermittent airflow of 10 l/s.
• The strategy has a high energy saving potential and qualifies to be used as a primary ventilation system.

Spaces with high occupancy density e.g.; classrooms, auditoriums and restaurants, provide challenges to ventilate at a lower energy use due to elevated temperatures. To meet occupants' thermal comfort requirements traditional systems use a lot of energy. Alternative ventilation strategies that optimize high air movements in the occupied zone allow human activities at elevated temperatures while attaining improve occupants' perception and acceptance of the indoor climate at a low energy use. This paper presents an experimental evaluation of a novel ventilation strategy for high occupancy spaces that provides fresh air and thermal comfort in the sitting zone through a controlled intermittent air jet system. The strategy uses ceiling mounted high momentum air jet diffusers (AJD) made from ventilation duct fitted with nozzles that generate confluent jets. The jets coalesce into a single two-dimensional jet which is directed downwards in the sitting zone. This paper presents an experimental evaluation/analysis of the proposed system with regard to ventilation efficiency and thermal comfort measurements in a classroom mockup. Results show that the system qualifies to be used as a primary ventilation system and has local air change index >1 inside the jet, and a ventilation efficiency >50%. The system also provides better thermal climate than mixing and displacement ventilation at elevated temperatures.