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TRANSIENT CONJUGATED UPWARD AND DOWNWARD MIXED CONVECTION IN A PARTIALLY HEATED THICK PIPE

DOI: 10.1615/ICHMT.2008.CHT.2050
16 pages

Abdeslam Omara
Université des Frères Mentouri Constantine 1, Département de Physique, Constantine, Algeria

Said Abboudi
Laboratoire Interdisciplinaire Carnot de Bourgogne, ICB UMR 6303 CNRS, Université Bourgogne Franche Comté (UBFC), UTBM, site de Sévenans 90010 Belfort cedex, France

Abstrakt

Transient conjugated downward and upward laminar mixed convection heat transfer in vertical pipe, submitted partially to a constant heat flux, has been investigated computationally. The governing Navier Stockes and energy equations were solved by a developed code using the finite volume method and Boussinesq's assumptions. Solutions were obtained for (Pr, Re, Gr)=(5, 100, 5·105), wall-to-fluid conductivity ratio K=10, 50 and 100 and pipe-thickness to diameter ratio Δ=0.05 and 0.25. From a parametric study, transient distribution of the normalized interfacial heat flux and of the friction coefficient ratio as a function of the axial coordinates as well as transient evolution of the vector velocities were obtained and effect of K and Δ were investigated. It was found that the magnitude and the extent of upstream and downstream heating increase monotonically with an increase of Δ or K. In turn, this heat flux redistribution has affected significantly the friction coefficient ratio and velocity field in the downstream and upstream adiabatic sections respectively for the downward and upward mixed convection cases.

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