NUMERICAL STUDY OF MIXING THERMAL CONDUCTIVITY MODELS FOR NANOFLUID HEAT TRANSFER ENHANCEMENT

Researchers have paid attention to nanofl uid applications, since nanofl uids have revealed their potentials as working fl uids in many thermal systems. Numerical studies of convective heat transfer in nanofl uids can be based on considering them as single- and two-phase fl uids. This work is focused on improving the single-phase nanofl uid model performance, since the employment of this model requires less calculation time and it is less complicated due to utilizing the mixing thermal conductivity model, which combines static and dynamic parts used in the simulation domain alternately. The in-house numerical program has been developed to analyze the effects of the grid nodes, effective viscosity model, boundary-layer thickness, and of the mixing thermal conductivity model on the nanofl uid heat transfer enhancement. CuO–water, Al₂O₃–water, and Cu–water nanofl uids are chosen, and their laminar fully developed fl ows through a rectangular channel are considered. The infl uence of the effective viscosity model on the nanofl uid heat transfer enhancement is estimated through the average differences between the numerical and experimental results for the nanofl uids mentioned. The nanofl uid heat transfer enhancement results show that the mixing thermal conductivity model consisting of the Maxwell model as the static part and the Yu and Choi model as the dynamic part, being applied to all three nanofl uids, brings the numerical results closer to the experimental ones. The average differences between those results for CuO–water, Al₂O₃–water, and CuO–water nanofl uid fl ows are 3.25, 2.74, and 3.02%, respectively. The mixing thermal conductivity model has been proved to increase the accuracy of the single-phase nanofl uid simulation and to reveal its potentials in the single-phase nanofl uid numerical studies
   
Author:  A. Pramuanjaroenkij, A. Tongkratoke, and S. Kakaç
Keywords:  nanofl uid, mixing thermal conductivity model, single phase, boundary layer
Page:  104