Two-phase pressure drop of water during flow boiling in a vertical narrow channel

Two-phase pressure drop during flow boiling of water in a vertical channel with cross-section 2 mm by 1 mm was investigated experimentally. The experiments were performed for the conditions of heat flux from 25 to 105 kW/m², mass flux from 57 to 211 kg/m²s and exit quality from 9% to 30%, including the influence of inlet compressibility. The two-phase pressure distribution along the channel was recorded at 200 Hz sampling frequency. The results were compared with four correlations. The Lockhart-Martinelli correlation for pressure drop in large tubes with modified C value has been shown to be still applicable with uncertainty of 35%. The homogeneous model had an uncertainty of 50%; the Tran and Chisholm methods over-estimated the experimental data by 100% and 300% respectively. It is shown that none of these correlations can predict published pressure drop data for water during flow boiling in a 50 by 70 micron channel.