Thermal characteristics analysis for convection heat transfer in turbulent flow of Al2O3-water nanofluid inside grooved tubes

Convection heat transfer of Al2O3-water nanofluid turbulent flow inside grooved tubes with different aspect ratios of grooves is numerically investigated. For grooved tube, the optimum geometric ratios are calculated so that entropy generation is minimized. The governing equations in steady state and axisymmetric form have been solved using finite volume approach (FVM) with the SIMPLE algorithm. A uniform heat flux is applied on the tube wall. A single-phase approach is employed to model the nanofluid flow.Nanoparticles size is 20 nm and nanoparticle volume fraction and Reynolds number are within the ranges of 0-5% and 10,000-35,000 respectively. Comparisons between the numerical results and available experimental data show that among different turbulence models, k-ε model with enhanced wall treatment gives better results. The results indicate that heat transfer increases with nanoparticles volume fraction and Reynolds number but it is accompanied by pressure drop augmentation. Correlations of heat transfer have been obtained for grooved tube in different aspect ratios using the numerical results. In evaluation of thermal performance and pressure drop, it is seen that thegrooved tubes with Al2O3-water nanofluid flow are thermodynamically advantageous. Finally the optimum geometric ratios for entropy generation minimization are obtained.

Keywords:

Nanofluid , Grooved tube , Turbulent flow , Forced convection , Entropy generation minimization