Hot air does not want to come down just because it can float above the cold one.
We published an experimental study on how to improve air change effectiveness of over-head mixing ventilation operating at heating conditions.
When warm supplied air is delivered at the ceiling level, buoyancy force prevents fresh air circulated throughout the occupied zone, especially in the region close to the floor. ASHRAE 62.1 pointed out that air change effectiveness (ACE) of overhead mixing ventilation is lower than 1. In worst scenarios at low supply airflow rates, our study shows that ACE could be lower than 0.5. In this study, we investigated how adjusting diffuser blades and changing exhaust locations could improve ACE significantly. Learn more about the study here.
Highlights
- Different strategies to improve air change effectiveness were examined.
- Proper adjustment of diffuser improved air change effectiveness up to 30%.
- Lower room-supply air temperature difference improved air change effectiveness.
- Locating return air inlet near floor improved air change effectiveness 70%.
- Diffuser adjustment may narrower the range of airflow rate, impacting ADPI.
Paper cite
Amai, Hideyuki, Shichao Liu, and Atila Novoselac. “Experimental study on air change effectiveness: Improving air distribution with all-air heating systems.” Building and Environment 125 (2017): 515-527.
