Enhancing Heat Transfer Inside a Double Pipe Heat Exchanger Using Al2O3 Nanofluid, Experimental Investigation Under Turbulent Flow Conditions

The aim of the present research is to enhance the convective heat transfer coefficient inside the tube of the double pipe under turbulent flow conditions, this is carried out by mixing the water with aluminium oxide (Al2O3) nanoparticles. In this study, the effects
 of Al2O3 nanofluid with different volume concentrations of 0.05% to 0.4%, mass flow rates of nanofluid inside the tube, mass flow rates of the water flow through the annulus, and inlet temperature inside the tube on the Nusselt number were investigated. The analysis of
 experiential results revealed that use Al2O3 nanofluids leads to a significant enhancement of the convective heat transfer coefficient. The convective heat transfer coefficients reached maximum values at 0.1% of the volume concentrations of Al2O3
 nanoparticles and then decreased as the increase of the volume concentrations from 0.1 to 0.4%. The Nusselt number increases as the Reynolds numbers of both the flows inside the tube and through the annulus increase. The fiction factor increases as the volume concentrations of nanoparticles
 increases. Empirical correlations are presented describing the Nusslet number and friction factor of the Al2O3 nanofluid flow through the tube of the double pipe heat exchangers, and concealing the affecting parameters in such process.