Thermal management of electronic devices using pin-fin based cascade microencapsulated PCM/expanded graphite composite

Microencapsulated phase change material (MEPCM) could be used for effective thermal management of electronic devices due to its large latent heat, phase change at nearly constant temperature, low volume expansion, and anti-leakage characteristics. Unfortunately, the low thermal conductivity of MEPCM hinders the heat dissipation rate from electronic devices especially at high heat flux conditions. Although the heat transfer capability of MEPCM could be accelerated by adding expanded graphite (EG) or inserting high thermal conductivity pin-fins, the latent heat energy storage capacity of MEPCM composite becomes less which reduces the corresponding operating time of limiting the electronic device temperature rise through solid-liquid phase change. In purpose of clarifying and optimizing this tradeoff effect on electronic device thermal management using MEPCM-EG composite with pin-fins, a numerical study is carried out through 3D lattice Boltzmann method with respect to different pin-fin configurations, EG content, PCM melting temperature, and heat flux conditions. The results indicate that the pin-fin array with medium fin number and fin thickness is beneficial for balancing the increased heat transfer capability and the decreased latent heat of MEPCM so that its optimum thermal performance is achieved. At the early working stage of electronic device, the pin-fin based MEPCM is demonstrated to be more effective than MEPCM-EG composite for controlling the electronic device temperature rise because of the direct contact between pin-fins and electronic heat sink base. However, as the electronic device working time evolves, the MEPCM-EG composite with network heat transfer channel is found to be more efficient for dissipating heat out of electronic device due to the relatively high average thermal conductivity throughout the whole heat sink system. Furthermore, the thermal performance of electronic device is found to be improved by inserting MEPCM-EG composite with cascade melting temperature decreasing from the heat sink base to heat sink cover. (C) 2019 Elsevier Ltd. All rights reserved.