This book presents the natural convection heat transfer from a vertical cylinder with annular fins has been studied numerically. The present numerical investigation is able to capture a complete picture of natural convection over an annular finned vertical cylinder from where easy visualization of the plume structure and flow field over the fin-tube surface can be obtained pictorially. In this present study, numerical simulations of full Navier-Stokes equation along with energy equation have been conducted for vertical tube with annular fins of constant thickness by varying the Rayleigh number. Chapter 1 deals with the introduction and literature survey regarding the natural convection heat transfer from vertical cylinder with and without annular fins. In chapter 2, a complete numerical analysis of natural convection from vertical cylinder with annular fins by varying the fin diameter, fin spacing and Rayleigh number. In chapter 3, an entropy generation analysis of finned tube configuration has been carried out.