## 1 Introduction  
Phase change materials (PCMs) have a high ability to store thermal energy [1, 2]. Usually, they have high phase change enthalpy, hence during the phase change, absorb a great amount of energy at the low-temperature range (phase change temperature) [3]. Therefore, it seems that these materials can also be utilized to cool the electronic devices [4] due to their high energy storage capability [5]. [PERSON] et al. [6] performed a numerical study on the potential of microencapsulated phase change material (MEPCM) on holding the temperature increase in electronic devices. They used expanded graphite (EG) nanoparticles with fin to enhance the thermal conductivity of MEPCM, but preliminary results showed that although fin improves the thermal conductivity of the heat sink, it also reduces the latent heat storage capability. They investigated two distinct heat sinks, the first heat sink used fin and the second one utilized EG nanoparticles to improve MEPCM thermal conductivity. In the early stages, the performance of the former heat sink was much better than the latter one, but over time, the performance of the latter one became better. The authors also showed that if multiple PCM with different melting temperatures were used, thermal performance would be improved. The authors recommend that MEPCM with a higher melting temperature should be used near the heat source. By moving away from the heat source, the MEPCM melting temperature must also be reduced. [PERSON] et al. [7] applied three PCMs of RT25, RT35, and RT44 for cooling of the electronic device under heat fluxes of 2000, 2950 and 3750 W m\({}^{-2}\). They observed that the base temperature of electronic devices which are equipped with PCMs, was lower by 69.8, 80.44, and 74.44 \({}^{\circ}\)C than the simple device. The authors also investigated the effects of ambient temperature in the solidification duration and it was found that as the ambient temperature increased from 20 to 25 \({}^{\circ}\)C, the solidification time of RT44 HC raised by 94 min. This figure for the ambient temperature of 30 \({}^{\circ}\)C was 178 min. [PERSON] et al. [8] used paraffin PCM for the cooling of an electronic chipset. They also incorporated multi-walled carbon nanotubes (MWCNTs) nanoparticles to enhance the PCM thermal conductivity. Three heat sinks were prepared and examined to evaluate the effects of using PCM on the electronic device cooling. The first heat sink was simple, while the second and third ones were filled with PCM. In the third heat sink, in addition to PCM, nanoparticles of MWCNT were also added. It was found that adding MWCNTs into the PCM led to a cooling time reduction up to 6%. In the active mode, incorporation of PCM and NPCM reduced the rate of increases in temperature in the early stages of the heating process, while intensified the chipset temperature in the steady state conditions. [PERSON] et al. [9] conducted many experimental tests to examine the thermal behavior of a novel PCM-based heat sink. They found that PCM layer thickness, PCM thermal conductivity, heat storage density and finally power load has an impact on the thermal behavior. At high input power, the PCM role in the thermal performance of the heat sink was more obvious than the conditions in which the input power is low. Heat thermal storage improvement led to more operation time of the device prior to reaching the critical temperature. The authors also observed that the PCM thermal conductivity increases the safe operation time slightly. Also, they revealed that the PCM thickness efficacy on the safe operation time was more than the PCM thermal conductivity. [PERSON] et al. [10] compared the ability of a new low-melting-point alloy (LMPA) with paraffin of RT60 (both of them has approximately the same melting point). LMPA thermal conductivity was 50 times than the RT60 one. Also, LMPA volumetric latent heat storage was 2.1 times that of RT60. Results showed that using LMPA rather than the paraffin enlarged the safe operation time up to 50%.