Recent Advances in Thermal Conductivity of Nanofluids

Abstract

This paper presents the most recent review of research articles and patents on thermal conductivity on nanofluids. Larger portion of literature accounts for experimental investigations, which is a sign of the preference for hands-on work by experimentalists. Metallic, non-metallic as well as ceramic nanoparticles of different sizes and shapes were suspended in common heat transfer liquids and their thermal conductivities were measured. In contrast to previous belief, it has now been proven that when the nanoparticle concentration is kept low the degree of enhancement falls reasonably within the boundaries predicted by the effective medium theories. There are strong evidences to suggest that the main mechanisms driving the thermal conductivity behavior are nanoparticle aggregation and the particle Brownian motion in suspension.

Thermal Wavelength Measurement of Nanofluid in an Optical-Fiber Thermal Wave Cavity Technique to Determine the Thermal Diffusivity

“…This was because the thermal diffusivity of nanofluid depended on some parameters, such as nanoparticles material, concentration of particles, size, base fluid, and surfactant. The thermal diffusivity of Ag nanofluid was improved by using Ag NPs with high thermal properties [ 25 ]. The resulting thermal diffusivity values of Ag nanofluids in different irradiation times were sorted in Table 1 .…”

Research progress on the effects of nanoparticles on gas hydrate formation

“…Water soluble surfactants have a signicant positive impact on the stability of nanouids that promote hydrate formation. [66][67][68] Cox et al 69 studied the effect of nanoparticles on the formation characteristics of CH 4 hydrate through the combination of MDS and experiments, and proved that nanoparticles can promote the formation of CH 4 hydrate in a way similar to the nucleation of heterogeneous ice for more hydrophilic or water-soluble guest molecules (such as THF or CO 2 ). Bai et al 70 studied the particle effect during the formation and decomposition of CO 2 hydrate, and found that the good ow characteristics in the initial stage of hydrate nucleus in the reactor are conducive to the continuous formation of hydrate; and once the hydrate ne particles coalesce, the uid uidity in the reactor will be reduced, which is not conducive to the continuous formation of hydrate.…”

An Analysis of Nanoparticle Settling Times in Liquids

“…Among these, the thermal conductivity is an important property that has been extensively investigated and debated over the past twenty years. Addition of traces of nanoparticles, often less than 1 vol% to a common heat transfer liquid, has enabled increasing the thermal conductivity of the same liquid by up to 40% or more [1][2][3]. However there are a few contradictory observations too.…”