Abstract
During the last decade, graphene foam emerged as a promising high porosity 3-dimensional (3D) structure for various applications. More specifically, it has attracted significant interest as a solution for thermal management in electronics. In this study, we investigate the possibility to use such porous materials as a heat sink and a container for a phase change material (PCM). Graphene foam (GF) was produced using chemical vapor deposition (CVD) process and attached to a thermal test chip using sintered silver nanoparticles (Ag NPs). The thermal conductivity of the graphene foam reached 1.3 W m−1 K−1, while the addition of Ag as a graphene foam silver composite (GF/Ag) enhanced further its effective thermal conductivity by 54%. Comparatively to nickel foam, GF and GF/Ag showed lower junction temperatures thanks to higher effective thermal conductivity and a better contact. A finite element model was developed to simulate the fluid flow through the foam structure model and showed a positive and a non-negligible contributions of the secondary microchannel within the graphene foam. A ratio of 15 times was found between the convective heat flux within the primary and secondary microchannel. Our paper successfully demonstrates the possibility of using such 3D porous material as a PCM container and heat sink and highlight the advantage of using the carbon-based high porosity material to take advantage of its additional secondary porosity.
Highlights
Organic phase change materials (PCMs) such as paraffin have been widely investigated as high latent thermal energy storage material capable of absorbing/releasing energy loads while being affordable, chemically stable and nontoxic with a low vapour pressure [2]
The movable approach based on nano/micro fillers has shown a considerable increase in the effective thermal conductivity of the nano/micro composites [3, 4], while the non-movable approach [5] based on fins, heat pipes and high porosity foam were found to provide further improvement in addition to structural advantages
Combined with PCM, carbon based high porosity foams was reported to be an effective thermal conductivity enhancer [34], with a conduction dominating cooling resulting in lower maximum temperatures and faster heating rates compared to aluminium foam at low power levels [35]
Summary
The movable approach based on nano/micro fillers has shown a considerable increase in the effective thermal conductivity of the nano/micro composites [3, 4], while the non-movable approach [5] based on fins, heat pipes and high porosity foam were found to provide further improvement in addition to structural advantages. Aluminium foam effective thermal conductivity was measured to reach 6 W m−1 K−1 at 90.98% porosity[11,12,13] and with heat fluxes as high as 68.8 · 104 W m−2 when used as a heat sink [14].
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