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Hydro-thermal behaviour determination and optimization of fully developed turbulent flow in horizontal concentric annulus with ethylene glycol and water mixture based Al2O3 nanofluids

2019    Ozdemir, Koray; Ogut, Elif

In this study, a comprehensive analysis of forced convection heat transfer and pressure drop through a concentric annulus heated from the inner wall and utilizing ethylene glycol (EG)-water based nanofluids for fully developed turbulent flow are conducted. In this context, effects of Reynolds number (10000-100,000), annulus radius ratio (0.1-0.9), EG concentration (0%-60%), nanoparticle volume fraction (0%- 1.5%) and nanofluid inlet temperature (0 degrees C - 50 degrees C) on Nusselt Number and pumping power have been analysed. To obtain nanofluids thermophysical properties, experimental data is implemented. To calculate the Nusselt number and friction factor, generalized formulations obtained from the direct numerical simulation are used. It is concluded that the Nusselt number increases with increasing Reynolds number and EG concentration while decreases with increasing radius ratio and inlet temperature in all conditions. In most cases, as nanoparticle volume fraction increases, Nusselt number increases while there are some opposite conditions. Besides, it is determined that the pumping power increases with increasing Reynolds number, EG concentration, nanoparticle volume fraction and radius ratio and decreases with increasing nanofluid inlet temperature. In addition, Response Surface Methodology and desirability function approach is implemented to determine the optimum operating conditions by maximizing Nusselt Number and minimizing pumping power for different scenarios.