Abstract: Heat dissipation by electric appliances is closely related to the height above sea level. The performance of air cooling systems significantly differs in different heights above sea level. For example, the density, pressure, and temperature of air change with the change in altitude. These parameters critically affect the heat dissipation of electric appliances. To accurately create a thermal design of electric appliances based on different altitudes, a mathematical model of the main parameters of a fan at different altitudes is established. The effect of the changes in the flow state of fluid medium on heat transfer is also determined. By introducing altitude parameters, the originally established heat transfer equation for sea level is modified. The theory proposed in this study is verified through practical calculation and Icepak14.5 simulation. Results are consistent with international electrotechnical experimental data. It also provides a reference for the digital thermal design of computers and other electric appliances.

Key words: altitude, electric thermal design, fan’s law, laminar, turbulence