Numerical correlation for natural convective flows in isothermal heated, inclined and convergent channels, for high Rayleigh numbers

A numerical study of natural convective flows, mainly for high Rayleigh numbers, in a sloped converging channel, for different inclination and convergence angles has been carried out, taking into account the lacks of the literature on some aspects of this configuration. Two-dimensional, laminar, transitional and turbulent simulations were obtained by solving the fully elliptic governing equations using two different general-purpose codes: Fluent and Phoenics. The low-Reynolds k-omega turbulence model has been employed. Special emphasis is made on the systematic comparisons of computational results with experimental and numerical data taken from literature for turbulent regime, so as on the transitional conditions, studying the influence of Rayleigh number and channel aspect ratio. A generalized turbulent correlation for the average Nusselt number has been obtained from numerical results in a channel with isothermal heated plates, for symmetric heating conditions. This correlation is valid for wide and not yet covered ranges of Rayleigh number (based on length of the channel) varying from 1010 to 1016, aspect ratio between 0.03 and 0.25, the converging angle from 1 degrees to 30 degrees and sloping angle from 0 degrees to 60 degrees. Finally, an application of this numerical correlation in two experimental prototypes is presented. (C) 2008 Elsevier Ltd. All rights reserved.