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Theoretical and numerical analysis of counter-flow parallel convective exchangers considering axial diffusion

Dichamp, Jules and Gournay, Frédéric de and Plouraboué, Franck Theoretical and numerical analysis of counter-flow parallel convective exchangers considering axial diffusion. (2016) International Journal of Heat and Mass Transfer, 107. 154-167. ISSN 0017-9310

(Document in English)

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Official URL: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.09.019


Abstract We perform a systematic analysis of heat transfer in a counter-current three dimensional convective exchanger, when the inlet/outlet influence is fully taken into account. The analysis, carried out for constant fluid properties, considers the various influences of the fluid/solid conductivity, the imposed convection, inlet/outlet far-field conditions, and lateral boundary conditions. Using a generalized Graetz mode decomposition which permits to consider, both transverse and longitudinal diffusion influence in the exchanger as well as in the inlets/outlets, we put forward several salient generic features of convection/conduction heat transfer. In all cases we found an optimal P\'clet number for the cold or hot effectiveness. Even if, as expected, the larger the P\'clet the larger the Nusselt number, high transfer performances are found to be poorly efficient and/or to necessitate non-compact elongated exchangers. Performance degradation arising at high P\'clet number are found to be related to â "convective leaksâ" taking place within outlets. A fully developed regime occurs at large P\'clet and/or for long exchangers, which is fully determined by the first eigenvalue of the generalized Graetz mode decomposition, which is an extension of classical Graetz analysis. Numerical results are found consistent with a generalized linear relation between effectiveness and the number of heat transfer units asymptotically established in the convection dominated regime. This study opens new perspectives for micro-heat exchangers where moderate convection provides the best effectiveness and compactness. This contribution is also useful for giving reference solutions to counter-flow exchangers with realistic inlet/outlet boundary conditions.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com The original PDF of the article can be found at http://www.sciencedirect.com/science/article/pii/S0017931015317038
HAL Id:hal-01405040
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - Toulouse INP (FRANCE)
Université de Toulouse > Institut National des Sciences Appliquées de Toulouse - INSA (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UT3 (FRANCE)
Université de Toulouse > Université Toulouse - Jean Jaurès - UT2J (FRANCE)
Université de Toulouse > Université Toulouse 1 Capitole - UT1 (FRANCE)
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Deposited On:29 Nov 2016 13:27

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