Thermal Diffusivity and Viscosity of Suspensions of Disk-Shaped Nanoparticles

Abstract

In this work we conduct a transient heat conduction experiment with an aqueous suspension of nanoparticle disks of Laponite JS, a sol forming grade, using laser light interferometry. The image sequence in time is used to measure thermal diffusivity and thermal conductivity of the suspension. Imaging of the temperature distribution is facilitated by the dependence of refractive index of the suspension on temperature itself. We observe that with the addition of 4 volume % of nano-disks in water, thermal conductivity of the suspension increases by around 30%. A theoretical model for thermal conductivity of the suspension of anisotropic particles by Fricke as well as by Hamilton and Crosser explains the trend of data well. In turn, it estimates thermal conductivity of the Laponite nanoparticle itself, which is otherwise difficult to measure in a direct manner. We also measure viscosity of the nanoparticle suspension using a concentric cylinder rheometer. Measurements are seen to follow quite well, the theoretical relation for viscosity of suspensions of oblate particles that includes up to two particle interaction. This result rules out the presence of clusters of particles in the suspension. The effective viscosity and thermal diffusivity data show that the shape of the particle has a role in determining enhancement of thermophysical properties of the suspension.

Interface-inspired formulation and molecular-level perspectives on heat conduction and energy storage of nanofluids

“…In both cases the intrinsic viscosity {η} parameter is included, which is sensitive to the particle shape. Its theoretical expression, which can be found in literature 56 , is a function of the particle diameter-to-length ratio d np /L np . For the calculation of such a ratio, average diameter and length of SWCNT (available in the supplier data sheet) were considered.…”

Measurement of Mass Diffusivity Using Interferometry through Sensitivity Analysis

“…The errors originating from this effect are estimated to be less than 1% with reference to eq , for the experimental data considered in the present analysis. The details of this effect have been discussed elsewhere. , …”

“…The Mach–Zehnder interferometer setup of the present work is described in Figure . It is identical to that used by our group to experimentally determine the thermal diffusivity of an aqueous suspension of Laponite. , It uses a 35 mW He–Ne laser (Spectra Physics) of 632.8 nm wavelength and 150 mm diameter optics. Two beam splitters suitably coated to produce 50% reflectivity and 50% transmitivity are employed.…”

“…The use of the sensitivity coefficient for thermal diffusivity was demonstrated by our group in the context of heat conduction in recent publications. , However, owing to the following important differences between the heat and the mass transfer measurements, the analysis of the latter tends to be more cumbersome:…”

Intrinsic conductivity of carbon nanotubes and graphene sheets having a realistic geometry

“…We also note the successful application of Eq. (1) to describe the thermal conductivity of suspensions of multi–wall CNTs [37] and laponite suspensions [38], the nanoparticle types considered in the present work. Finally, Eq.…”