In this paper, a numerical study is carried out to investigate the melting process of a nano-enhanced phase change material (NePCM) in a latent heat thermal energy storage unit (LHTESU) with insertion of Cu nanoparticles. The use of such a strategy provides passive cooling of a protruding electronic component attached to a substrate. The governing equations of heat transfer are solved using the enthalpy-porosity technique and the finite volume method based using a personal FORTRAN code. An investigation of the effect of the PCM quantity is carried out taking into account three different values of the characteristic length lo (0.06 m, 0.08 m and 0.10 m) which represents the PCM quantity. The effect of nanoparticle characteristics, including volume fraction and shape factor on melting rate, are also discussed. The results showed that the maximum operating temperature of the electronic component decreases by 2.9 °C with an insertion of a nanoparticles fraction of 0.04 and a characteristic length of 0.08 m. For the same characteristic length, the melting time is 8630 s, 8460 s and 8290 s with nanoparticles fraction of 0.00, 0.02 and 0.04, respectively. With the nanoparticles fraction of 0.04, the amount of sensible heat stored within the PCM increases by 1.3% and the latent heat decreases by 1.1%. In addition, the insertion of nanoparticles with a shape factor of 16.1 reduces the maximum operating temperature of the electronic component by 2.5 °C. Correlations, giving the electronic component maximum working time and the plateau temperature, were developed using the asymptotic computational fluid dynamics technique (ACFD).