ADIABATIC 2-PHASE PIPE-FLOW OF AIR WATER MIXTURES UNDER CRITICAL FLOW CONDITIONS

This investigation deals with the experimental determination of the mean velocity ratio of air and water in adiabatic two-phase pipe flows under steady-state critical conditions and with the analytical derivation of the mean velocity ratio, mean void fraction and critical mass flux based upon a radial modeling of the flow. An air-water loop was designed and constructed to determine the critical mass flux and the mean velocity ratio with an impulse measurement device as functions of tube diameter and length, pressure and flow quality. Measurements of the radial distribution of total pressure in critical flow at the exit cross-section of the test tube, combined with analytical considerations, yielded radial profiles of density, void fraction and velocity of the phases. These profiles reveal the occurrence of a locally homogeneous flow, whereas the mean velocity ratio of the flow exceeds the value of unity. Assuming that the local velocities, excepting those near the wall, are equal to the local homogeneous sonic velocity, a subsequent application of an integrational procedure permitted the computation of the mean velocity ratio and the critical mass flux. The results are in good agreement with the experimental data. A parameter variation study proved the applicability of the analytical procedure to the description of critical two-component two-phase flows. © 1990.