Characteristics of the Liquid Film and Pressure Drop in Horizontal, Annular, Two-phase Flow Through Round, Square and Triangular Tubes

A unique set of liquid film thickness and pressure drop data has been obtained for horizontal, annular flow of air and water through round, square and triangular tube using a noninvasive, optical liquid film thickness measurement system. In the square and triangular tubes, the liquid film was thinned in the corners, indicating an effect of turbulent secondary flows in these geometries. In addition, when the film thickness is nondimensionalized using a friction velocity based on the total pressure drop, it is found that virtually all the data lie below h+=35 and that dryout occurs at approximately h+=5. The two-phase friction factor for the annular flows examined in all the tubes can be correlated using the Lockhart–Martinelli parameter, Xtt, when adjustments are made for the hydraulic diameters of the nonround tubes.