Pressure drop characteristics of vertically upward flow in inclined rod bundles

•A pressure drop test loop is established.•A new superposition model is proposed to predict single-phase pressure drops in inclined rod bundles.•Pressure drop characteristics of two-phase flow in an inclined rod bundle are analyzed.•New correlations are developed to obtain two-phase pressure drops in an inclined rod bundle.

An experimental and theoretical research has been carried out for vertically upward two-phase flow of air–water across staggered rod bundles having inclination angles of 0°, 45° and 90°. New correlations for single-phase pressure drops in rod bundles for various inclination angles were developed. The single-phase frictional resistance in the vertical flow was found to have a minimal effect on the total flow resistance in the inclined flow. Based on the single-phase pressure drop data, a new superposition model was proposed and verified to be successful in predicting both the present data and the experimental data in previous experiments of other researchers. The two-phase friction multiplier in the inclined rod bundle, which decreased with increasing mass velocity at a given value of Martinelli parameter, could be fit well in terms of Martinelli parameter and the defined dimensionless mass velocity. In addition, the two-phase friction multiplier first increased and then decreased with increasing Martinelli parameter at a given value of mass velocity for G < 200 kg m−2 s−1. The new correlations developed for two-phase friction multipliers were successful in predicting the two-phase pressure drop data in the inclined rod bundle.