Effect of Real Viscosity on the Heat Transfer of Nanofluids Containing Carbon Nanotubes in a Two-Sided Lid-Driven Differentially Heated Square Cavity

The effects of real viscosity on the heat transfer behavior of nanofluids containing carbon nanotubes inside a two-sided lid-driven differentially heated square cavity is numerically investigated. The viscosity of the nanofluids is considered by two methods: (I)-the Brinkman viscosity relation which is usually applied for nanofluids and (II)-experimental correlation relation which is obtained by experimental investigation on the viscosity of the nanofluids. Some of the physical properties of the base fluid such as thermal conductivity and thermal expansion coefficient are assumed to be temperature dependent. Governing parameters such as Richardson number (0.02 < Ri < 100) and the volume fraction of the nanofluids (0 < phi < 1%) were considered but only a few results from the fluid flow and the heat transfer were presented due to space constraints. It was found that the real viscosity of the nanofluid at different Richardson numbers and the volume fractions of the nanofluids affected the fluid flow and the heat transfer of nanofluids. By using the real viscosity of the nanofluids, the numerically predicated results are in good agreement with the experimental results. Finally comparisons between the average Nusselt numbers at the left wall for the mentioned methods are presented.