A new correlation for convective heat transfer coefficient of water-alumina nanofluid in a square array subchannel under PWR condition

The computational fluid dynamic (CFD) simulation is performed to determine on the thermo- and hydrodynamic performance of the water-alumina (Al2O3) nanofluid in a square array subchannel featuring pitch-to-diameter ratios of 1.25 and 1.35. Two fundamental aspects of thermal hydraulics, viz. heat transfer and pressure drop, are assessed under typical pressurized water reactor (PWR) conditions at various flow rates (3 × 105 ⩽ Re ⩽ 6 × 105) using pure water and differing concentrations of water-alumina nanofluid (0.5-3.0 vol.%) as coolant. Numerical results are compared against predictions made by conventional single-phase convective heat transfer and pressure loss correlations for fully developed turbulent flow. It is observed that addition of tiny nanoparticles in PWR coolant can give rise to the convective heat transfer coefficient at the expense of larger pressure drop. Nevertheless, a modified correlation as a function of nanoparticle volume fraction is proposed to estimate nanofluid Nusselt number more precisely in square array subchannel.