Abstract
An experiment has been performed to study the pressure drop and friction factor of supercritical water in a 2 × 2 rod bundle. A fuel-assembly simulator with four heated tubes was installed inside a square channel with round corners. The outer diameter of each heated tube is 8 mm with a pitch-to-diameter ratio of 1.18. The full length between the inlet and outlet pressure measuring holes is 550 mm. Experimental parameter covered the pressures of 23–28 MPa, heat fluxes of 200–1000 kW/m2 and mass flux of 1000 kg/m2s. The variations of total pressure drop, frictional pressure drop, gravitational pressure drop and acceleration pressure drop with bulk enthalpy were studied. It was found that the pressure drop varies notably in the pseudo-critical and high-enthalpy regions due to the strong variations of the thermophysical properties. The friction factor exhibits a local valley as the bulk temperature approaches the pseudo-critical temperature. The effect of heat flux on the frictional pressure drop and friction factor is weak, while the effect of pressure is mainly restricted to the high-enthalpy region. It was found that the friction factor of the 2 × 2 rod bundle is slightly higher than that of a smooth tube, but is significantly lower than those of sub-channel or internally-ribbed tube. Eight correlations were assessed against the current set of experimental friction factor. It was observed that the Filonenko correlation is superior to other correlations. An improved correlation for predicting the friction factor was proposed in support of the hydrodynamic analysis of rod bundles at supercritical pressures.
Published Version
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