Abstract: This study exploits computational fluid dynamics (CFD) to simulate the natural convection heat transfer behavior of the external wall of an electronic device. The simulation analyzes and calculates convective heat dissipation using Boussinesq approximation, aiming to understand the heat-transfer characteristics of the natural convection process occurring on the wall. The heat transfer characteristics are analyzed by categorizing them into two types—— the convective and radiative. Formulas for natural convection heat transfer coefficients are developed by analyzing natural convection processes on horizontal and vertical walls, as well as on cylindrical and spherical surfaces. Through an analysis of the natural convection heat transfer characteristics, approaches to improve heat transfer efficiency between the outer wall of electronic devices and the environment are proposed. Additionally, the radiation heat transfer behavior of the electronic device within its operational environment is investigated. The radiation heat transfer equation is simplified to determine the radiation heat transfer coefficient. Building upon these findings, a comprehensive heat transfer formula related to wall temperature is established by integrating convection and radiation heat transfer coefficients. Using this comprehensive heat transfer formula, the heat transfer amount can be quickly calculated when the outer wall temperature of the electronic device is known. The results enable a rapid calculation of heat transfer between the outer wall of the electronic device and its surrounding environment, and provide a more convenient and effective approach in the thermal management design and optimization of heat dissipation for electronic devices.