AN EXPERIMENTAL-STUDY OF FREE-CONVECTION HEAT-TRANSFER FROM AN ARRAY OF HORIZONTAL CYLINDERS PARALLEL TO A VERTICAL WALL

An experimental investigation of heat transfer from an array of three horizontal cylinders aligned vertically parallel to a single wall is presented. Three different cylinder center-to-center spacings for the array cylinders were examined, CC = 1.5D, 2D, and 4D. The wall-array spacings were varied from 0.081D to infinity. The cylinders were placed in a still air medium at atmospheric pressure and maintained at constant heat flux. Modified Rayleigh number, based on the diameter of the cylinders, ranged from 6.2 x 10(4) to 1.2 x 10(6). Results indicate that heat transfer is generally enhanced, but for some wall spacing to cylinder configurations the heat transfer can be minimally decreased. For cases where the heat transfer was enhanced the top cylinder in the array was observed to have the highest enhancement (22 percent) and the lowest cylinder was enhanced the least (5 percent). Flow visualization studies showed that the wall generated a chimney effect between the wall and the cylinders.