There are certain principles of air movement that, once understood, allow you to direct airflow as needed in an HVAC system. Understanding these principles will allow you to solve comfort problems that have plagued homeowners for decades. The use of the “Coanda Effect” is one of these principles. Once understood, the way you look at duct systems and registers will change forever.
The Coanda Effect is named in honor of Henri Coanda, a Romanian aerodynamics pioneer and aircraft inventor. This phenomenon is sometimes referred to as the surface effect in many publications. The Coanda Effect occurs when airflow is closely projected to a parallel surface, such as a ceiling or the walls of a duct system. When this occurs, airflow is affected by the parallel surface it is flowing with. In simpler terms, air clings to surfaces as it moves.