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Analysis of natural convection in tall vertical cavities heated by a linear heat flux and cooled isothermally

Lahcen El Moutaouakil (Department of Physics, Cadi Ayyad University, Marrakech, Morocco.)
Zaki Zrikem (Department of Physics, Cadi Ayyad University, Marrakech, Morocco.)
Abdelhalim Abdelbaki (Department of Physics, Cadi Ayyad University, Marrakech, Morocco.)

International Journal of Numerical Methods for Heat & Fluid Flow

ISSN: 0961-5539

Article publication date: 7 April 2015

149

Abstract

Purpose

This work is devoted to the numerical analysis of laminar natural convection in two-dimensional vertical cavities, filled with air and of high aspect ratios. One of the sidewalls is cooled isothermally while the other is heated by a uniform or linear heat flux whose average is located at mid-height of the wall. The paper aims to discuss these issues.

Design/methodology/approach

The governing equations are discretized by the finite volume method and solved, in transient regime, by using the SIMPLE algorithm.

Findings

The flow structure, air temperature field, local convective heat flux on the cold wall, variation of the temperature along the heated wall as well as its average and its maximum are analyzed for various combinations of the controlling parameters. These parameters are the linear heat flux slope γ (γ=0, 1 and −1, for a uniform, increasing and decreasing heat flux, respectively), the average Rayleigh number Ra m (103Ra m 3×104) and the aspect ratio A (10A80). It was found that for a given A and Ra m , the highest (lowest) mean temperature of the hot wall is obtained when the linear heating is descending (ascending). While the maximum temperature increases with the three controlling parameters.

Practical implications

Accurate correlations which allow calculating the average and maximum temperatures of the heated wall are developed for each type of heating. Also, an empirical relationship for the position of the maximum temperature is provided for γ=−1.

Originality/value

Despite its fundamental and practical interest, natural convection in cavities with 10A80 and submitted to non-uniform heat flux was not examined before. Development of original correlations.

Keywords

Citation

El Moutaouakil, L., Zrikem, Z. and Abdelbaki, A. (2015), "Analysis of natural convection in tall vertical cavities heated by a linear heat flux and cooled isothermally", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 25 No. 3, pp. 550-569. https://doi.org/10.1108/HFF-03-2014-0086

Publisher

:

Emerald Group Publishing Limited

Copyright © 2015, Emerald Group Publishing Limited

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