Study on Annular Mist Flow in Pipe : 1st Report, Investigation of the Non-equilibrium Length and Changes of Some Factors in the Non-equilibrium Region

Abstract

An annular mist flow using air and water at room temperature has been studied experimentally in a vertical pipe with a nozzle along the axis of the pipe for supplying liquid. Observations were made of flow patterns of liquid on the inner surface of the pipe, and measurements were made of pressure losses in pipe, profiles of radial distribution of liquid droplets and total flow rates of the liquid droplets. Changes of these four factors along the pipe were measured in the non-equilibrium region. It was found that the non-equilibrium length should be decided by a position where any changes in the four factors mentioned above could not be recognized in the axial direction. For relatively high velocities of air, i.e., for apparent gaseous Reynolds number R_ego ≥9.4×10⁴, it was ascertained that the annular mist flow reached equilibrium at a distance of 170-190 diameters from the nozzle outlet when apparent liquid Reynolds number R_elo = 62.1-183.6.