Temperature dependent thermal conductivity increase of aqueous nanofluid with single walled carbon nanotube inclusion

We investigated the thermal and electrical conductivity of water seeded with single-walled carbon nanotubes (SWCNT) synthesized using the alcohol catalytic chemical vapour deposition method. Sodium deoxycholate was used as the surfactant to prepare stable nanofluids, which we then thoroughly characterized by microscopic and spectroscopic methods. Electrical conductivity measurements showed power law dependence with respect to SWCNT loading, while the thermal conductivity increase showed a linear dependence on loading. The effective thermal conductivity of the nanofluid was also found to increase with increasing temperature. Viscosity of the nanofluids showed a threefold increase compared to the thermal conductivity increase, which may play a crucial role in utilizing this fluid for practical applications. We compare experimental results with existing analytical models and discuss the critical role of thermal boundary resistance, which limits the improvement in thermal conductivity. Influence of SWCNT aggregation in the increase of effective thermal conductivity is also discussed. *Corresponding author. Tel: +81-3-5841-6421. Fax: +81-3-5800-6983. E-mail address: maruyama@photon.t.u-tokyo.ac.jp (S. Maruyama) 2