Optimization of natural convection heat transfer from a cylinder with high conductivity fins

The problem of laminar natural convection from a horizontal cylinder with one or more high conductivity fins on its outer surface was investigated numerically. The aim was to optimize the number, size, and location of the fin(s) for maximum natural convection heat convection, i.e., Nusselt number, over a wide range of Rayleigh numbers. The percentage improvement in heat transfer per fin(s) unit length, i.e., cost efficiency, was also studied. For all combinations of Rayleigh number, number of fin(s), and fin(s) location, the maximum Nusselt number occurred when using the longest fin(s). Placing two long fins, per each half of the cylinder for a total of four fins for a complete cylinder, one at the lower and the other at the top parts of the cylinder, resulted in the maximum Nusselt number over the entire range of Rayleigh numbers studied (10(3)-10(6)). The exact tangential location of these two fins was Rayleigh number dependent. The highest fin cost efficiency was achieved by using one or two optimally placed fin(s). The configuration for the highest fin cost efficiency did not always coincide with that of the maximum Nusselt number.