Liquid-film thickness, flow pattern, and void fraction of hydrocarbons and their zeotropic mixtures during convective condensation

摘要: The present study concerns an experimental investigation of the liquid-film thickness, flow patterns, and void fraction during convective condensation of hydrocarbons and their zeotropic mixtures. Experiments were performed for R600a, R290, R1270, R600a/R290 (70/30 molar fraction) and R600a/R1270 (75/25 molar fraction) in a horizontal tube with an internal diameter of 9.43 mm. In the experiments, the saturation temperature was kept at 35°C, mass velocities ranged from 50 to 250 kg/m2s, vapor qualities from 0 to 1, and heat fluxes from 5 to 60 kW/m2. It was noticed that the transition from gravitational to shear-driven flow patterns can be quantitatively characterized by a peak in the newly defined base liquid-film thickness measured at the top region of the channel at a certain vapor quality. At mass velocities higher than 100 kg/m2s, shear-driven flow patterns were dominant, and noticed in a wider range of vapor …