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).