Liquid-film thickness and disturbance-wave characterization in a vertical, upward, two-phase annular flow of saturated R245fa inside a rectangular channel

摘要: Abstract The liquid-film flow in a vertical, upward, two-phase annular of saturated R245fa is characterized experimentally under adiabatic conditions. experiments are conducted inside rectangular channel with cross section 11.6 × 36 mm2 for mass velocities ranging from 95 to 130 kg/m2s, vapor qualities 0.63 0.9 and saturation temperature 23 °C. Liquid-film thickness disturbance-wave velocity frequency measured optically. recorded at sampling 2000 Hz, while 20 Hz. A parametric study as function quality performed. Results show that the decreases linearly increasing quality. liquid films investigated very thin, thinner than critical below which momentum transport no longer driven by disturbance waves. Indeed, high quality, when film liquid-vapor interface becomes smoother waves slow down vanish. frictional pressure gradient increases until it reaches peak. suggest subsequent decrease closely linked disappearance For range studied operating conditions, remains constant within uncertainty measurements. Experimental data compared prediction methods literature. Although reasonable predictions were obtained thickness, none tested could predict accurately.