Heat transfer enhancement in nano-fluids suspensions: Possible mechanisms and explanations

Nanoscale Ionic Materials

“…The relative viscosity of NIMS follows the same behavior as that observed in conventional colloidal suspensions, where the relative viscosity increases with increasing volume fraction (w) until eventually diverging at a critical volume fraction associated with the glass transition. [13][14] Not only do these systems show similar behavior, but standard models such as the Krieger-Dougherty equation [18] and the Thomas equation [19] fit the data reasonably well, indicating that theories used for colloidal suspensions may satisfactorily describe the general behavior of these materials at concentrations below the NIMS transition. It is apparent from the figure that for w < 0.25, both the Krieger formula and Thomas equation are in good accord with the experimental data, implying that at low concentrations these NIMS can be crudely modeled as suspensions, albeit with effective particle volume fractions larger than the volume fraction of the bare core.…”

“…They are therefore excellent candidate media for emerging applications in immersion photolithography. [9][10][11] Likewise, nanoparticle ionic fluids created from core particles with high electrical conductivity and mobile ionic species in the corona provide a new approach for creating stable, high-conductivity lubricating waxes and heattransfer fluids, [12][13][14] and liquid electrolytes for high-temperature electrochemical cells. [15] 2.…”

On the spatial behavior of solutions for non-linear type II heat conduction

“…Let us say that the heat conduction phenomena at very low temperatures seem to be well described by the theory of wave propagation at finite speed. For instance, Hwang et al [18], Maïga et al [28], Kim et al [25] or Vadasz et al [37] suggest that a mechanism for the increased heat transfer characteristics of a nanofluid may be through a hyperbolic equation for the temperature field.…”

Thermal Characterization of ZnO-DMSO (Dimethyl Sulfoxide) Colloidal Dispersions Using the Inverse Photopyroelectric Technique

“…5 Hyperbolic heat transfer might have been the cause of the anomalous heat transfer enhancement experimentally obtained by means of this method, as discussed by Vadasz and coworkers. 6 In the particular case of metallic nanoparticles (non-diamagnetic) colloidal dispersions, it is possible that magnetic fields induced by the flow of current across the heating wire and convection effects can cause the appearance of vortices in the fluid, among other undesirable effects. Furthermore, taking into account the facts that each nanofluid has unique characteristics, and that there is not an appropriate thermal conductivity model, one can conclude that the reliable experimental measurement of thermal conductivity is today an experimental target, along with the development of methods for the measurement of other physical properties that can help in the modeling of the involved heat transfer mechanisms.…”

“…9 (ii) The low amplitude temperature oscillations involved do not affect the thermal properties of the sample during the measurement. 10 This is the main advantage in comparison with the transient PT methods 11 and the hot wire technique, 6 where the above mentioned hyperbolic effects can be present. The interpretation of the experimental data using the hyperbolic heat diffusion equation is very complicated because it involves the relaxation times needed for the onset of a heat flux after a thermal gradient is imposed to the sample, 12,13 which are usually unknown.…”