Study the Effect of Ceiling Air Diffuser Blade and Lip Angles Using CFD

Abstract

The objective of the present work is to investigate the airflow characteristics inside a room through a 5-blade square louver face ceiling air diffuser using CFD to improve occupant's thermal comfort. Several blades angles (45°, 60° and 65°) and lip angles (0°, 5°, 10°, and 15°) were installed inside the room model. The realizable k-ε turbulence model was used to simulate all the 3D cases. In the paper, the results of 5-blade louver face diffuser with 60° blade angle and horizontal lip are compared with 5-blade louver face diffuser with 45° and 65° blade angles with horizontal lip. Then, the effect of lip angle is investigated and compared with the results from a diffuser with a 60° and horizontal lip. The results showed that the diffuser with a 65° blade angle provides jet air velocity higher than 60° beside air patterns cling with room ceiling, which enhances the surface (Coanda) effect and provides lower temperature gradients than 60°. Therefore, it is suitable to install in larger spaces in order to reduce drafts on space occupants and reduce installation costs. On the other hand, the results indicated that the diffuser model with a 45° blade angle and 0° lip angle provides cone-shaped air patterns without any being attached to the room ceiling, therefore this type is preferable for installation in rooms with larger height or inside areas that require relatively low noise levels. Moreover, increasing the diffuser lip angle to 15° allows air patterns relatively to leave the room ceiling, and reach thermal comfort conditions without draft faster than the 0° lip angle.