Industrial & Engineering Chemistry Research, Vol.49, No.4, 1900-1904, 2010
Effect of CuO Nanoparticles in Enhancing the Thermal Conductivities of Monoethylene Glycol and Paraffin Fluids
The effect of CuO nanoparticles on the thermal conductivities of paraffin and monoethylene glycol (MEG) was investigated. An enhancement in the effective thermal conductivity was found for both fluids. This enhancement was studied with regard to various factors: nanoparticle concentration, nanoparticle size, and base-fluid type. For both base fluids, an improvement in thermal conductivity was found as nanoparticle concentration increased; this was attributed to an increase in particle-to-particle interactions. It was also found that, as the particle size was reduced, there was also an improvement in the thermal conductivities of the fluids. A reduction in nanoparticle size leads to an increase in the Brownian motion of the particles, which also causes more particle-to-particle interactions. The role that the base fluid plays in the observed enhancement is complex. Lower fluid viscosities are believed to contribute to greater enhancement, but a second effect, the interaction of the fluid with the nanoparticle surface, can be even more important. Nanoparticle-liquid suspensions generate a shell of organized liquid molecules on the particle surface. These organized molecules more efficiently transmit energy, via phonons, to the bulk of the fluid. The efficient energy transmission results in enhanced thermal conductivity. The experimentally measured thermal conductivities of the suspensions were compared to a variety of models. None of the models were found to adequately predict the thermal conductivities of the nanoparticle suspensions.