A Comparative Analysis of Theoretical and Experimental Models Concerning Various Thermophysical Properties of Nanofluids

Abstract

The significance of nanofluids is increasingly acknowledged due to their application across various fields to enhance the properties of mixtures. A significant challenge lies in accurately calculating their thermophysical properties, as no theoretical formula currently exists that can estimate these with precision. This work critically reviews theoretical models used to calculate the thermophysical properties of nanofluids, focusing specifically on thermal conductivity and dynamic viscosity. A comparative study, based on experimental results for six types of nanofluids, was conducted to examine the validity ranges of several theoretical formulas for conductivity and viscosity. The impact of these formulas on heat transfer outcomes was also assessed in a horizontally heated square cavity. Findings show that for each nanofluid type, specific formulas yield optimal results. In contrast, others diverge significantly, with error margins ranging from 0.1% to 49% for conductivity and 0.1% to 77% for viscosity, depending on the mixture’s nanofluid type, volume fraction, and temperature. Additionally, it was observed that the choice of viscosity calculation model influences results, with the error margin between the model yielding the highest heat transfer and the one yielding the lowest, reaching up to 130% for the same nanofluid under identical conditions.