Natural Convection Cooling of a Stack of Three Horizontal Cylinders in Laminar Regime

The present work is intended to investigate the natural convection heat transfer from a stack of three solid horizontal cylinders numerically in a three dimensional computational domain. Simulations were conducted in the laminar flow regime of Rayleigh number spanning in the range (10(4) <= Ra <= 10(8)) and length to diameter ratio in the range (0.5 <= L/D <= 20). The thermal fields are visualized in terms of temperature contours while heat transfer characteristics are elucidated in terms of the average Nusselt number (Nu). The average Nusselt number shows a positive dependence on Ra for all L/D. Furthermore, the average Nu is found to be significantly higher for short cylinders and decreases with increase in L/D up to 15 and remain constant for long cylinders. In the present study, an attempt has been made to compare the present 3D simulation results for the extreme case of L/D=20 with the 2D numerical results of Rath and Dash [ 6] in order to justify the use of 2D simulations.