Thermal conductivity of nanofluids based on hollow γ-Al2O3 nanoparticles, and the influence of interfacial thermal resistance

The current paper presents the results of theoretical and experimental studies of the thermal conductivity of nanofluids based on hollow nanoparticles. The thermal conductivity of nanofluids was studied experimentally using hollow Al2O3 nanoparticles in water, ethylene glycol, and isopropyl alcohol. The experiments were carried out at nanoparticle volume concentrations of 2.2%. Thermal conductivity was measured by the nonstationary hot wire method. It was found that the dependences of thermal conductivity obtained on volume concentration gave values below those obtained by the Maxwell theory for all nanofluids. The analysis showed that the presence of a cavity under the conditions of these experiments could not explain the observed results. The conclusion about the final value of Kapitza contact resistance at the nanoparticle-liquid interface was made based on the comparison of experimental data with the theory. The Kapitza contact resistances were estimated for the interfaces between nanoparticle material and basic fluids used.