Functionalization and exfoliation of graphite into mono layer graphene for improved heat dissipation

A novel synthesis procedure is presented for preparing single layer graphene (SGr) with high specific surface area (SSA). The SGr has been introduced as a promising additive for preparing super conductive nanofluids for high performance heat transfer applications. Owing to high SSA and unique degree of functionalization with hydrophilic groups, the SGr demonstrates an excellent colloidal stability and thermophysical properties as an additive in aqueous media. Using UV-vis spectrometer, a highest dispersion stability of 0.866-relative concentration was reached after 30 days from preparation. Water-based SGr nanofluids illustrated fairly Newtonian behavior. Nanofluid containing SGr sheets with SSA of 761 m2ig and weight concentration of 0.01% showed the largest increase in thermal conductivity, i.e., from 0.748 to 0.795 Wim K as the temperature increased from 20 to 50 degrees C. The average heat transfer coefficient ratio (h(nf)/h(bf))(ave) showed a downward trend with increasing of Reynolds number, decreasing from 233.5% at Re of 2000 to only 83.8% at Re of 16,000 at the constant weight concentration of 0.01%. Finally, the water based SGR nanofluids were shown to be dramatically more effective in the duct with a backward-facing step in terms of overall thermal performance e.g., performance index and pumping power, and rheological properties including effective viscosity in comparison to distilled water. (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.