Effect of a Side Wall on the Natural Convection Heat Transfer from a Vertical Row of Horizontal Square Rods

Abstract

Experimental study is carried out to investigate natural convection from a vertical array of three horizontal square rods fixed adjacent to a vertical adiabatic wall and tested under constant heat flux condition. The experimental rig is designed and constructed for this purpose with variable horizontal distance ratio (H/D) in the range (0.125 < H/D < 3.0). The vertical distance between the rods is changed to get ratio (S/D) ranges of (1.5 < S/D < 4). The Rayleigh number tested is in the range of (1.26 × 106 < Ra < 6.6 × 106) with variable heating levels. The finite volume computational method is used to determine the flow and thermal field around the array of the square rods in different experimental configurations. The computed fields confirm the discussion of the experimental behavior of each rod in the array at each test configuration. Results show that the main parameters affecting the heat dissipation rate of each of the rods are position of the rod in the array, relative vertical distance between the rods and horizontal distance to the adiabatic side wall. The chimney effect noticed between the rods and the adiabatic wall plays a big role in heat transfer enhancement at certain (H/D) values. Experiments show that the ability of the rods to dissipate heat was increased at the largest tested vertical distances with the same behavior noticed for the small horizontal distances relative to the adiabatic wall with a tendency of each rod to behave as a free rod as its horizontal distance to the wall is increased. A dimensionless empirical correlation for each rod was found. Another general correlation for the whole array is used to relate the experimental data of each rod according to its position in the array.