This Text Book deals the Study of natural convection heat transfer over a vertical cylinder immersed in air or embedded with porous media is one of the areas of research interest due to its wide range of Engineering & industrial applications. The first objective focuses on an experimental study of natural convection heat transfer in vertical cylinders embedded with and without porous medium at uniform wall temperature. The second objective is that the factorial design of experiments are conducted to analyze the natural convection in vertical circular cylinders embedded with and without porous media to find the effect of temperature (T), Aspect ratio (Ar), Radius ratio (R), Power supply (q) and their interaction effects on Nusselt number (Nu), Rayleigh number (Ra), heat transfer coefficient (h), and on viscous dissipation parameter ( ).