Different HVAC application scenarios with microperforated absorbers

* Presenting author
Day / Time: 21.03.2018, 10:20-10:40
Room: MW 1050
Typ: Regulärer Vortrag
Abstract: The usage of Microperforated Absorbers (MPAs) in HVAC-systems has been increasing within the last decade. MPAs offer distinctive advantagesto the conventional foam and fibrous absorbers like robustness, durability and the possibility to target a chosenfrequency band if a specially tuned multilayered arrangement of MPAs is used. By modeling the MPA's absorption characteristics with an effective density and bulkmodulus according to the Johnson-Champoux-Allard (JCA) approach and resolving the entire geometrywithin the Finite Element (FE) tool CFS++, we include that the combination of MPA and backingcavity is not locally reacting. By comparing transmission loss measurements of a simple expansion chamberwith simulation data, we demonstrate that the JCA approach works well for plane waves grazingacross the absorber as well as higher order modes impinging under oblique incident.Additionally MPAs are applied to a diffusor shaped expansion chamber and as flow conducting structures. Such an arrangement of MPAs challenges the aforementionedapproach and their application itself, since MPAs usually require a non-moving backing air volume forthe underlying acoustic mechanism to work. By comparing measurements of a generic silencerset-up with acoustic and flow simulation data, we semi-empirically incorporate flow effects by extending theJCA model.