Horizontal-base and vertical-base heat sinks are simulated and optimized geometrically in order to improve performance of heat sink in natural convection heat transfer with software ICEPAK. At first

the numerical model is validated through comparison of results between the experiments which has already existed and the numerical simulation herein. Then

a series of heat sinks with different geometric parameters are simulated. The optimal geometric parameter will be found through comparing their performance. Fin thickness varied from 1 to 15 mm

fin spacing varied from 6.75 to 33.75 mm and fin height varied from 55 to 1395 mm. The result indicates that there are optimal fin thickness t and optimal fin space s at every fin height. The smallest thermal resistance of horizontal-base heat sinks for certain fin height tends to be a constant value as fin height is over 720 mm. The smallest thermal resistance of vertical-base heat sinks for certain fin height always decreases as fin height increases.