Numerical Investigation of Natural Convection in a Square Vented Enclosure Heated by Dual Horizontal Cylinders

This study presents a two-dimensional numerical investigation of natural convection in a square symmetrically vented enclosure heated by dual horizontal cylinders. The study aims to understand the coupled effects of the opening aspect ratio (W/L varying from 0.1 to 1.0) and Rayleigh number (Ra = 10⁴ to 10⁶) on flow and thermal fields. The governing equations for steady, laminar, incompressible flow were solved using the Finite Element Method (FEM) via COMSOL Multiphysics. Results demonstrate that at Ra = 10⁴, streamlines remain uniform with minor vortices, and the average Nusselt number (Nu) increases proportionally with the aspect ratio. At higher Ra (10⁵ and 10⁶), increasing the opening ratio from 0.1 to 0.5 enhances Nu by up to 35%, whereas further enlarging the opening (0.6 to 1.0) surprisingly reduces Nu due to flow bypass. Full openings completely suppress vortex generation. These quantitative findings provide critical insights for optimizing the cooling of electronic devices.