Effects of the thermal boundary conditions at the sidewalls upon natural convection in rectangular enclosures heated from below and cooled from above

Steady laminar natural convection in air-filled, 2-D rectangular enclosures heated from below and cooled from above is studied numerically for a wide variety of thermal boundary conditions at the sidewalls. A specifically developed numerical model based on the SIMPLER algorithm is used for the solution of the mass, momentum and energy transfer governing equations. Simulations are performed for several values of both the width-to-height aspect ratio of the enclosure in the range between 0.66 and 8, and the Rayleigh number based on the cavity height in the range between 103 and 106, whose influence upon the flow patterns, the temperature distribution and the heat transfer rates are analyzed and discussed. Comparisons among the different thermal configurations considered are reported. In particular, with reference to the typical configuration wherein the sidewalls are adiabatic, it is found that the heat transfer effectiveness of the bottom wall increases (or slightly decreases) as each adiabatic sidewall is replaced by a cooled (or a heated) sidewall. An opposite behaviour is observed for the top wall. The heat transfer rate results obtained are expressed through dimensionless correlation-equations. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.