LIQUID-TO-WALL SHEAR-STRESS DISTRIBUTION IN STRATIFIED ATOMIZATION FLOW/

Experiments were conducted in a horizontal flow loop (24 mm i.d.), usi ng an electrochemical technique, for measuring liquid-to-wall shear st ress, at Various positions around the pipe circumference. Measurements of liquid film thickness, pressure drop as well as visual observation s were also made. These data complement similar information obtained b y Paras et al. (1994), in a horizontal 50.8 mm i.d. flow system. Mean values and other statistical information are obtained from the analysi s of the shear stress and film thickness data. Visual studies of the g as/liquid interface confirm that its profile is concave rather than fl at. The data show that the time-averaged shear stress tends to decreas e in the lateral direction (i.e. away from the pipe bottom, Theta = 0 degrees) along which the liquid film gradually becomes thinner. Only f or relatively low superficial gas velocities (e.g. U-G < 15 m/s), the mean shear stress is almost constant up to Theta = 45 degrees; i.e. in a flow region where there is a relatively thick liquid layer. An expr ession is proposed for predicting the shear stress circumferential dis tribution. By means of momentum balances (utilizing the new data), the average gas/liquid interfacial friction factor is determined with imp roved accuracy. Additionally an equivalent gas/liquid interface roughn ess is expressed in terms of wave characteristics, i.e. wave intermitt ency and amplitude. (C) 1997 Elsevier Science Ltd.