A numerical study is conducted to explore the natural convection heat transfer within a cylinder characterized by an irregular cross-sectional shape. The current study focuses on utilizing free convection phenomena to reduce the temperature of the cylinder. In this study, the fundamental equations governing the fluid flow around the cylinder’s surface are numerically solved using ANSYS FLUENT. The geometrical parameters of the cylinder are taken into consideration during the investigation for a particular range. The Rayleigh number (Ra) considered within the laminar zone for a wall temperature of 327 °C and surrounding temperature is taken as 27 °C. The research demonstrates that as the Rayleigh number and surface temperature increase, the Nusselt number also rises. However, this increase becomes marginal for elevated length-to-diameter ratios. Moreover, the rate of heat transfer exhibits a reduction as the length-to-diameter ratios increase. Indeed, the study’s findings offer valuable insights into the distribution of local coefficient of heat transfer along the surface of the cylinder.