Numerical study of nanofluid heat transfer enhancement with mixing thermal conductivity models [Article]

Abstract

Nanofluids have shown the possibility of enhancing heat transfer performance above its base fluids. This work presents a numerical study that analyzes the nanofluid heat transfer enhancement using different theoretical models; i.e., the effective thermal conductivity and effective viscosity models. The Maxwell, Brownian motion, and Yu and Choi models were considered as the effective thermal conductivity models and these models were used and mixed alternately in the simulation domain, referred to as mixing models. The Al2O3-water nanofluid was chosen in this study and assumed to flow under a laminar, fully developed flow condition through a rectangular pipe such as in a circuit application. The governing equations, written in terms of the primitive variables, were solved through an in-house program using the finite-volume method and the semi-implicit method for pressure linked equations (SIMPLE) algorithm. From the study, the mixing models using Yu and Choi model coupled with Maxwell and Brownian models at the wall boundaries combined with the viscosity model from Maiga provided the numerical results closer to the experimental results from Zeinali Heris and co-workers at volume fractions of 0.01, 0.02, and 0.03%, as well as those of the base fluid. Therefore, by increasing the nanoparticle amounts, volume fraction, effective viscosity, and effective thermal conductivity at the wall region could be increased and enhancements of 0.01, 0.02, and 0.03% volume fractions were 21, 29, and 36% increasing from the base fluid, respectively. This work can strongly support the literature in which the volume fraction, effective viscosity, and effective thermal conductivity can enhance the heat transfer performance in nanofluid flows not only with the single-phase model considered but also with the mixing models examined.