Studies on Evaluation of the Thermal Conductivity of Alumina Titania Hybrid Suspension Nanofluids for Enhanced Heat Transfer Applications

Extensive investigations were made and empirical relationswereproposed for the thermal conductivity of mono-nanofluids. The effectof concentration, diameter, and thermal properties of participatingnanoparticles is missing in the majority of existing thermal conductivitymodels. An attempt is made to propose a model that considers the influenceof such missing parameters on the thermal conductivity of hybrid nanofluids.Al2O3-TiO2 hybrid nanofluidshave a 0.1% particle volume concentration prepared with distinct particlevolume ratios (k - 1:6 - k, k = 1 to 6) in DI water. The samples were characterized,and the size and shape of the nanoparticles were verified. Also, theinfluence of varying particle volume ratios and the fluid temperature(varying from 283 to 308 K) were examined. 2.4 and 2.1% enhancementswere observed in the thermal conductivity of alumina (5:0) and titania(0:5) nanofluids (having 0.1% volume concentration), respectively.Due to the low thermal conductivity of titania nanoparticles, theconductivity of the hybrid solution is above that of titania and belowthat of alumina nanofluids. An empirical relation for the thermalconductivity of hybrid nanofluids is established and validated consideringthe individual particle size, volume ratio, and thermal conductivityof particles.

Automated summary

Extensive investigations were conducted to explore the thermal conductivity of mono-nanofluids, but the effect of concentration, diameter, and thermal properties of nanoparticles was often overlooked. This study proposed a model that considers the influence of these parameters on the thermal conductivity of hybrid nanofluids. Experimental results showed 2.4% and 2.1% enhancements in thermal conductivity for alumina (5:0) and titania (0:5) nanofluids, respectively, with a 0.1% particle volume concentration.