Hierarchical hybrid heat sink material for thermo-electric generators

Abstract

This short communication focuses on the impact of enhancing heat sink effectiveness of thermoelectric generators (TEG) by attaching covalently bonded carpet-like arrays of carbon nanotubes on prefabricated copper structures. Structural hierarchy of heat sinks are important for synergizing the thermal conductivity of materials with fin architectures tailored for active or passive electronic cooling components. We investigated strategic integration of carefully aligned carpets of carbon nanotubes (CNTs) on heat sink fins to simultaneously enhance conductive, convective, and radiative heat transfer pathways. Carbon nanotubes (CNT) combine ultra-high thermal conductivity along their axial directions with high surface area and radiative heat transfer coefficients. While CNTs are known to enhance nanofluidic coolants and thermal interface composites, their full potential can only be utilized if they are aligned normal to heat sink fins, and strongly anchored to retain the fin/radiator architecture in service conditions. This study focused on measuring the direct impact of CNT carpet on TEG performance under ambient passive cooling conditions without adding any noticeable weight or volume to the heat sink. It was seen that this single step of CNT attachment on the surface could increase the open circuit voltage of TEG modules by over 50% in the passive mode with respect to original untreated heat sink, and over 100% with respect to no heat sink. This improvement may be enhanced even further by introducing forced coolants. These results therefore show significant promise in using the surface nanocarpet approach for development of compact, lightweight, robust and reusable solid-state heat sinks in future.