A sensitivity analysis of factors influencing thermal conductivity of nanofluids

Numerical investigations are conducted to study the effect of particle clustering and interfacial layer thickness on thermal conductivity of nanofluids. The interplay between these two factors is examined through Kapitza radius, which hasn’t often been rigorously investigated in literature. Degree of enhancement is analysed for increasing aggregate size, particle concentration and interfacial resistance. The numerical work is validated with experimental data for water-based nanofluids of Alumina, CuO and Titania nanoparticles. Particle concentrations are varied up to 4vol%. Aspect ratio (radius of gyration of aggregate to radius of primary particle, Rg/a) varied between 2 to 60. It can be confirmed that the enhancement decreases with interfacial layer thickness. The rate of decrease takes a significant turn after a particular aggregate size. For a given interfacial resistance, enhancement ratio is mostly sensitive to vol%<4 and Rg/a <20. A good agreement is found between predicted and experimental data. In summary, the present work provides important information on the interval of aggregate sizes, particle concentrations and interfacial resistances that will be useful in manufacturing high thermal conductivity nanofluids. For future work, efforts are underway to refine the model by incorporating cluster evolution dynamics as a function of particle-scale properties.