Two-phase frictional pressure drop in small rectangular channels

This study presents single-phase and two-phase frictional pressure drop data in three rectangular channels with channel width of 3, 6 and 9 mm, and a fixed gap of 3 mm. Adiabatic flows of air–water mixtures are tested at mass flux of 100–700 kg/m2 s and gas quality ranging from 0.001 to 0.8. The single-phase friction factors agree satisfactorily with the predictions of laminar and turbulent flows. The two-phase frictional pressure drop data are compared to predictions of homogeneous and Chisholm method, Wambsganss and Ide–Fukano correlations. It is found that none of the existing methods or correlations can predict the two-phase pressure gradient in rectangular channels satisfactorily. A modified C factor of Chisholm method considering the effect of aspect ratio is proposed from the empirical fit with the data sets of Wambsganss et al., Ide–Fukano, and this study. The corresponding mean deviations of the proposed correlation against the datasets are 24.99%, 10.83% and 10.73%, respectively. This correlation is applicable in wide rages of mass flux (50 < G < 700 kg/m2 s), gas quality (0.001 < x < 0.95), Martinelli parameter (0.05 < X < 20) and aspect ratio (0.1 < A < 1.0).