Interaction of surface radiation with natural convection in tall vertical cavities heated by a linear heat flux

Abstract

Purpose

A detailed numerical study is conducted on the effect of surface radiation on laminar natural convection in a tall vertical cavity filled with air. The cavity is heated and cooled, through its two vertical walls, by a linear or uniform heat flux q(y) and by a constant cold temperature, respectively. The horizontal walls are considered adiabatic. The paper aims to discuss these issues.

Design/methodology/approach

The radiosity method is employed to calculate the net radiative heat exchanges between elementary surfaces, while the finite volume method is implemented to resolve the governing equations of the fluid flow.

Findings

For each heat flux q(y) (ascending, descending or uniform), the effect of the emissivity ε (0ε1) on the local, average and maximum temperatures of the heated wall is determined as a function of the average Rayleigh number Ra_m (103Ra_m 6×104) and the cavity aspect ratio A (10A80). The effect of the coupling on the flow structures, convective and radiative heat transfers is also presented and analyzed. Overall, it is shown that surface radiation significantly reduces the local and average temperatures of the heated wall and therefore reduces the convective heat transfer between the active walls.

Practical implications

The studied configuration is of practical interest in several areas where overheating must be avoided. For this purpose, a simple design tool is developed to estimate the mean and the maximum temperatures of the hot wall in different operating conditions (Ra_m, A et ε).

Originality/value

The originality lies in the study of the interaction between surface radiation and natural convection in tall cavities submitted to a non-uniform heat flux and a constant cold temperature on the active walls. Also, the development of an original simplified calculation procedure for the hot wall temperatures.

Citation

El Moutaouakil, L., Zrikem, Z. and Abdelbaki, A. (2016), "Interaction of surface radiation with natural convection in tall vertical cavities heated by a linear heat flux", International Journal of Numerical Methods for Heat & Fluid Flow, Vol. 26 No. 6, pp. 1975-1996. https://doi.org/10.1108/HFF-12-2014-0378