Experimental Evaluation of Dielectric Oil Functionalized Nanodiamond Suspension Under Laminar Flow Regime

Dielectric oils serve as the primary means of cooling in electric power utility operations. However, beyond the recent advancements in improving the electrically insulating properties, relatively little has been done to optimize the thermal properties of these fluids for their application. Nanoparticle-based fluid suspensions show interesting potential for innovation in enhancing the cooling abilities of dielectric oils. In this study, the convective heat transfer capabilities of a dielectric transformer oil modified with functionalized nanodiamond were studied in a horizontal tube heat exchanger. The behavior was studied in the laminar flow regime. The pressure drop along the same heated test section was also measured. The thermophysical properties of the fluid, such as thermal conductivity, viscosity, and specific heat capacity were studied extensively as a function of the temperature so that their contribution to the enhancement of the effective heat transfer coefficient could be accounted for. The expected values for the Nusselt number as a function of the Reynolds and Prandtl numbers are reported in comparison to the experimental results. Any anomalous convective heat transfer performance beyond the expected could point to other mechanisms in the enhancement process, such as kinematic modification of the flow field due to the presence of nanoparticles, which can direct the efforts of future studies.