Wide angle 3D air diffusers are commonly employed in numerous industrial processing plants to expand and slow down process air flow prior to entering heat exchangers. The diffuser design itself is commonly compromised due to engineering design constraints such as space, cost and technical expertise. The air handling unit is often located in close proximity to the diffuser and heat exchanger installation, resulting in a complex underdeveloped velocity profile across the diffuser inlet and the subsequent heat exchanger core. A wide range of literature is available covering the performance and design of 2D diffusers with fully developed incident flow, however there is little available literature dealing with the 3D compound diffusion of such flows. The added complexity that arises from the undeveloped incident flow to the diffuser is also not fully defined.

The resulting flow regimes that are generated inside 3D wide angle diffusers typically found in New Zealand industries have been analysed both experimentally and computationally with an included angle range of 20 to 90º. The performance of each diffuser has been assessed in terms of the mass weighted velocity profile across the heat exchanger and the pressure recovery coefficient. CFD simulations have also been used to model additional design modifications with the models validated against the experimental cases presented. Flow treatment devices (guide vanes) have also been tested and simulated with substantial improvements in both the pressure recovery across the diffuser and a reduction in the mass weighted face velocity across the heat exchanger.