Arkansas HVACR NewsMagazine November 2019

S tate, National, Chapter News Tech News

principles or consumers will not value your pitch for improved comfort and efficiency. Coanda effect- Is the tendency of a fluid jet to stay attached to a convex surface. It is named after Romanian inventor Henri Coandă. The effect is demonstrated most popularly with the effects or air over an aircraft wing. The effect is desired when we use curved blade terminal devices to keep the air bumping along the ceiling outside the occupied zone. This also allows the air to meet targets of outside walls and windows. Bernouli principle-In fluid dynamics, Bernoulli's principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid's potential energy. The Bernouli principle is used when designing transitions and where accommodating proper face velocities for grille performance and filter performance. By employing the principle we can speed up or slow down the air to match system requirements. Terms commonly used in reference with terminal device catalogs are as follows; Drop is measured by the distance the majority of the air travels before entering the occupied zone. When scanning data in grille catalogs, drop distances are measured under isothermal conditions.

That is to say the temperature of the air introduced into the room is the same temperature as room air. When selecting grilles the distance stated in the data will be reduced by approximately 40% if introduced air has a delta of 20 degrees below the entrained or existing air in the space.

Throw is the most commonly reviewed term that identifies the distance the air will travel at velocities above 50 fpm. We should remember isothermal testing may necessitate adjustment for real time application.