Further Investigation on Laminar Forced Convection of Nanofluid Flows in a Uniformly Heated Pipe Using Direct Numerical Simulations

Abstract

Abstract:In the present paper, laminar forced convection nanofluid flows in a uniformly heated horizontal tube were revisited by direct numerical simulations. Single and two-phase models were employed with constant and temperature-dependent properties. Comparisons with experimental data showed that the mixture model performs better than the single-phase model in the all cases studied. Temperature-dependent fluid properties also resulted in a better prediction of the thermal field. Particular attention was paid to the grid arrangement. The two-phase model was used then confidently to investigate the influence of the nanoparticle size on the heat and fluid flow with a particular emphasis on the sedimentation process. Four nanoparticle diameters were considered: 10, 42, 100 and 200 nm for both copper-water and alumina/water nanofluids. For the largest diameter d np = 200 nm, the Cu nanoparticles were more sedimented by around 80%, while the Al 2 O 3 nanoparticles sedimented only by 2.5%. Besides, it was found that increasing the Reynolds number improved the heat transfer rate, while it decreased the friction factor allowing the nanoparticles to stay more dispersed in the base fluid. The effect of nanoparticle type on the heat transfer coefficient was also investigated for six different water-based nanofluids. Results showed that the Cu-water nanofluid achieved the highest heat transfer coefficient, followed by C, Al 2 O 3 , CuO, TiO 2 , and SiO 2 , respectively. All results were presented and discussed for four different values of the concentration in nanoparticles, namely ϕ = 0, 0.6%, 1% and 1.6%. Empirical correlations for the friction coefficient and the average Nusselt number were also provided summarizing all the presented results.

Ethylene- and Propylene-Glycol Based Nanofluids: A Litterature Review on Their Thermophysical Properties and Thermal Performances

“…Thus, the nanofluid specific heat can be defined from a thermal balance including the mixture rule. This equation has been widely used by [42][43][44] among other references.…”

Exergy Analysis of a Parallel-Plate Active Magnetic Regenerator with Nanofluids

“…For Al 2 O 3 -water-based nanofluids with a mean particle diameter of 47 nm, Equations (8) and (9) provided by Maïga et al [24] then used by Mintsa et al [25] have proven to be accurate in most configurations as shown by Sekrani et al [26] for laminar flows in an uniformly heated pipe. Equations for the dynamic viscosity µ and the thermal conductivity λ of the nanofluid write:…”

An Investigation on the Forced Convection of Al2O3-water Nanofluid Laminar Flow in a Microchannel Under Interval Uncertainties

“…It was shown that the increase of rib height and nanoparticle concentration were beneficial to the heat transfer performance. Sekrani et al [11] studied the flow and heat transfer of nanofluids in horizontal passages using direct numerical simulation. They found that, compared with the single-phase model, the two-phase model provided higher prediction accuracy.…”