1. Introduction :
1.1. Overview :
Electronics have become an inevitable part of this digital era. Hence, effective thermal management is one of the biggest concerns, not only for cost effectiveness but also for safety purposes. The miniaturization of electrical components has made this issue more complex. Working temperatures should be kept within a limited range to maintain the proper functioning of electronics. Conventional cooling systems (natural convection and forced convection) are insufficient to meet the cooling requirements for high-performance and smaller-sized electronic components. A temperature decrease of 1°C can lower the failure rate of electric components by as much as 4% [1].
Cooling systems can be broadly categorized as active cooling and passive cooling. A heat sink is utilized in active cooling to dissipate heat from the chip. Generally, it uses fins to increase the surface area for convection and to facilitate removing heat from the attached surface. A fan may be added to enhance the overall thermal performance of a heat sink. However, there are some drawbacks of using fans, such as noise and vibration. Therefore, the use of passive cooling systems is necessary to achieve high performance and longevity of electrical components.
A passive cooling system can be fabricated using PCM because of its ability to store and release a large amount of energy as latent heat during the phase transition process. PCM also has the capability of maintaining a constant temperature when transitions occur from solid to liquid states in most cases. Hence, PCM has started to be added to the heat sink in recent years to decrease the temperature rise in the electrical components. PCM-based thermal management systems offer effective working conditions for electronic components, enhance cooling performance, and reduce energy consumption [2,3]. Besides, several articles [4-6] have discussed the thermophysical properties, different types, phase transition behaviors and applications of phase change materials.
A thermal management system with and without PCM is investigated in this paper. COMSOL finite element simulation software is used to study the temperature distribution, rise time, effect of fin height, fin numbers and power supply on the base of the heat sink and compare the performance of different PCMs.
1.2. Literature review :
S.A. Isaacs et al. [7] have investigated the performance of heat sinks by using phase change materials. They evaluated the heat transfer and flow in pin-fin microgaps. It has been shown that the pin-fin structure can significantly increase the convective heat transfer coefficient in single-phase flow conditions. They used R245fa as a working fluid. Experimental investigations have been carried out by R. Baby and C. Balaji [8] by using n-eicosane as a phase change material that is placed inside a heat sink made from aluminum. They studied both the finned and un-finned heat sinks, and constant heat loads were applied. They found that the overall performance of the heat sink can be increased by filling the fins with PCMs.
Pakrouh et al. [9] numerically studied the pin fin heat sink with paraffin RT44 as a PCM. They estimated the effect of different geometrical parameters, such as height, thickness, and number of fins. They also considered volume expansion in phase transition as well as natural convection. Ali et al. [10] concluded the experimental performance of two types of pin fin heat sinks with n-eicosane and paraffin wax PCMs. They found that circular fins performed better than square fins with these PCMs, along with a 90% volume of fins. Kandasamy et al. [11] used a 3-D CFD model to compare the performance of rectangular-profile fins filled with paraffin wax as PCM. They found an increase in the cooling performance of a heat sink filled with PCM as compared to a heat sink without PCM when the power input is sufficiently high (power input > 2W).
Jaworski [12] performed a numerical simulation of a hollow circular pin fin heat sink filled with PCM and cooled by forced convection. Results showed that the thermal resistances of hollow round pin FHS were much lower than those of simple PCM-filled heat sinks. Arshad et al. [13] experimented with three types of square pin fins of length 1, 2, and 3 mm filled with PCMs (paraffin wax and n-eicosane). They found that 2 mm square fins performed better than other fin types. Siyabi et al.  [14] studied experimentally three different heat sinks to evaluate the effects of PCM combinations, thickness, melting temperature, and intensity of heat source. They concluded that the RT50-RT55 combination of PCMs increased the thermal regulation period as well as reduced the temperature of the heat sink. They also found that the thermal regulation period increased with the thickness of phase change materials.
Ashraf et al. [15] experimented with square and circular fins in a partially filled PCM container. They used six types of PCMs with power levels ranging from 4 to 8 watts. They found that square fins were most effective without using PCM, but with PCM, circular fins performed well. They also showed that paraffin wax performed best at an 8W power level. Liu et al. [16] explored the effects of power losses, fin height, air velocity, and the thickness of the phase change materials on the protection ability of the heat sink filled with PCM. They optimized the heat sink design to increase the thermal performance. They had found an 80-s protection period and a 100-s recovery time after optimization.