Unsteady Natural Convection inside a Porous Enclosure Heated from the Side

Experiments were conducted to study transient natural convection in a porous medium filling a differentially heated enclosure. Four porous media are considered consisting of spherical beads of diameter 0.2, 0.4, 0.6, and 0.8 cm. The aspect ratio of the enclosure, A = H/L, is 0.67. The investigations were carried out for Darcy-modified Rayleigh numbers between 285 and 9 x 10(4). The results indicate that heat transfer increases with increasing Darcy number, Da, for the same Rayleigh number The time needed for heat wave propagation through the porous medium from the hot isothermal wall to reach a steady state is reduced with increasing Darcy number and/or by increasing the Darcy-modified Rayleigh number for the same Da. The variation of Nusselt number and the Darcy-modified Rayleigh number with time has also been investigated experimentally.