RELATIONSHIP BETWEEN VIBRATION BEHAVIOUR AND TWO-PHASE FLOW REGIME TRANSITIONS FOR PIPING WITH INTERNAL FLOW

Internal two-phase flow is common in piping components. Modeling such flow and in particular locating flow regime transition turns out to be a difficult task, due to the numerous parameters involved. Theoretical transition boundaries proposed by Taitel et al. (1980). for upward gas-liquid flow in vertical tubes seem to apply fairly well within a limited range of tube diameters. However, Anscutter et al. (2006) have shown, recently that this model does not adequately reflect transitions for high flow velocity. They have suggested a simple empirical boundary to describe transitions from bubbly flow to churn or slug flow. This transition boundary is based on homogeneous velocity, surface tension, gas and liquid densities. The present paper is intended to verify the new suggested transition model. Experiments are carried out on various vertical clamped-clamped PVC tubes. Tubes of 9.0 to 23.8 mm inside diameter are subjected to air-water two-phase flow. Homogeneous flow velocities are varied between 1 m/s and 5 m/s. Volumetric qualities are varied in 5% increments near transitions. Transitions are detected using both photographs and the "maximum, two-phase dam-ping method" (Anscutter et al., 2006). Results shows that even if two-phase damping and flow regime are correlated, the "maximum two-phase damping method" is not a precise way to etablish transition. Finally this paper proposes a correction on two-phase damping model for bubbly flow.