ASME-HT2012: 13-7 Application of Computational Heat Transfer
Heat and mass transfer enhancement by two elastic flaps oscillating in a laminar flow
Charbel Habchi1, Serge Russeil1,2,*, Daniel Bougeard1,2, Jean-Luc Harion1,2, Thierry Lemenand3, Dominique Della Valle3,4, Hassan Peerhossaini3
1EMDouai, EI, F-59500 Douai, France
2Université Lille Nord de France, F-59000 Lille, France
3Thermofluids, Complex Flows and Energy Research Group, LTN – CNRS UMR 6607, École Polytechnique, Nantes University, F-44306 Nantes, France
4ONIRIS, rue de la Géraudière, B.P. 82225, 44322 Nantes, France
Coherent flow structures can be readily produced by using vortex generators due to pressure gradients or shear instabilities. These vortices enhance the heat and mass transfer by promoting secondary convective motion in the flow cross section. Most of previous work has focused on vortex generators made of rigid tabs of different shapes. Recently, few numerical studies in the literature were interested in the use of flexible flaps, especially in micro-mixers. However, the oscillation of these flaps was induced by an external force, such as a magnetic field, and it is shown that, in the optimal conditions, this method can greatly enhance the mixing process. The present study deals with the use of such elastic flaps in multifunctional heat exchangers/reactors, without the use of an external excitation. In fact, the flaps are in direct interaction with the flow structure generated mainly by shear instabilities, and freely oscillate due to the force induced by the flow. To this end, an in-house partitioned numerical solver is developed by using the open source C++
library OpenFOAM. Finite volume method is used for both flow and solid domains. Strong coupling between the flow and the structure displacement is achieved by a block Gauss-Seidel implicit scheme with Aitken’s under-relaxation. The present geometry consists of two flaps inserted on opposite walls in a laminar channel flow. Two cases are studied! In the first the flaps are considered to be rigid, and in the second elastic flaps are considered. The passive scalar transport and energy equations are solved to investigate the effect of the flaps oscillation on the mass and heat transfer processes respectively. It is shown, that the use of elastic flaps induces chaotic behavior in the flow and enhances the scalar mixing and the heat transfer.
*Corresponding author: Tel.: +33.3.27.71.23.88; Fax: +33.3.27.71.29.15 E-mail address: serge.russeil@mines-douai.fr
