Use of Functionalized Nanodiamond Additive for Enhancement of Thermal Convective Coefficients

In electrical infrastructure, transformer systems are a key link the power supply chain. The throughput capacity of these systems is largely limited by its core temperature, driven by resistive heating and mitigated by the thermal characteristics of the transformer's oil. If the transformer oil's thermal conductivity can be improved without significant sacrifice of other characteristics, then more heat can be wicked away for the same temperature gradients, naturally allowing for lowered core temperatures or increased throughput power capacity if core temperature is to be held as constant. Several additive approaches have been taken in course of this goal; however, this study focuses on use of nanoscale diamonds functionalized with oleic acid as a potential method of enhancement. Diamond structures are dielectric and have an exceptionally high thermal conductivity (~2,200 W/m•K), making them theoretically ideal as an additive in electronics thermal management. This study focuses on the thermal behavior of transformer oil with 0.2 wt% to 1.0 wt% functionalized nanodiamond additive. Tests occur within a controlled natural convection environment with a target hot surface temperature of 60 °C. Thermal convection coefficients are empirically calculated via energy balance and heat flux methods. Temperature differentials at steady-state are used as well as a measure of enhancement.