This paper reports on numerical simulations of passive cooling of an electronic component. The strategy is based on the fusion of a nano-enhanced phase change material (NePCM) by insertion of hybrid Cu-Al2O3 nanoparticles. This study analyzes the combined effects of the position of the electronic component and the inclination of the heat sink for rectangular and square geometries on the heat transfer and flow structure of liquid NePCM. The heat sink is heated by a protuberant heat source simulating the role of an electronic component generating a volumetric power. The electronic component is mounted on a substrate modeling the role of a motherboard. The development of a 2D mathematical model is based on the equations of conservation of mass, momentum, and energy. This system of equations is solved using the finite volume method and the SIMPLE algorithm for velocity–pressure coupling. The enthalpy-porosity approach is adopted to model the phase change. The results obtained show that the position of the electronic component and the inclination of the enclosure have important effects on the efficiency of the cooling strategy. The inclination of 90 deg and the position of δ = 0.5 represent the case where the cooling of the electronic component is efficient and operates safely with a minimum temperature difference recorded along it. The electronic component is well cooled in a rectangular heat sink than in a square one.