Periodic assembly of multi-coupled parallel plates: vibration propagation and acoustic radiation

Résumé et principaux résultats

Article présenté à ICSV16, 16ème International Congress on Sound and Vibration, 5-9 juillet 2009, Cracovie - Pologne. Il concerne la propagation des vibrations et le rayonnement acoustique d'échangeurs de chaleur de type batterie à ailettes.
Abstract:
This study concerns the vibroacoustic behaviour of a heat exchanger - a finned coil - consisting of a succession of numerous identical parallel fins. This type of complete finned coil can not be numerically modelled with conventional FEM due to very-high computational costs. Therefore the structure periodicity is exploited to reduce the size of the model. The presented approach is based on the dynamic behaviour of a unit element which is duplicated to obtain the whole periodic structure. The finned coil structure is simplified for the study and consists of a finite periodic assembly of parallel plates multi-coupled by springs. In a first step, a vibration modelling is presented. The use of the transfer matrix formulation and the Floquet-Bloch's theorem allows the calculation of structure-borne wave propagation along the global structure. The main advantage of this approach is to provide a wave description suitable for a further acoustic radiation calculation. This description allows getting a more physical interpretation of the wave propagation along the periodic structure. The second step deals with the acoustic modelling. The basic idea is to sum the radiation of one baffled unit element for various angles for which phases are given by the wave propagation obtained in the first step. Then a numerical validation is done on a small structure, by comparing results from the presented method and the classical BEM approach. Finally, assumptions previously made and results obtained by simulation are discussed and several physical phenomena related to periodic structures are highlighted.

Commissions

MFCE - Matériel Frigorifique; Conditionnement d'air; Echangeurs

Thème

Acoustique générale et vibroacoustique

Mots-clés

Acoustique, Echangeurs, Echangeurs à ailettes, Vibrations

Auteurs

BESSAC François, GOSSE Guillaume