Q Qingzhi Hou

Experimental investigation on rapid filling of a large-scale pipeline

This study presents the results from detailed experiments of the two-phase pressurized flow behavior during the rapid filling of a large-scale pipeline. The physical scale of this experiment is close to the practical situation in many industrial plants. Pressure transducers, water-level meters, thermometers, void fraction meters, and flow meters were used to measure the two-phase unsteady flow dynamics. The main focus is on the water-air interface evolution during filling and the overall behavior of the lengthening water column. It is observed that the leading liquid front does not entirely fill the pipe cross section; flow stratification and mixing occurs. Although flow regime transition is a rather complex phenomenon, certain features of the observed transition pattern are explained qualitatively and quantitatively. The water flow during the entire filling behaves as a rigid column as the open empty pipe in front of the water column provides sufficient room for the water column to occupy without invoking air compressibility effects. As a preliminary evaluation of how these large-scale experiments can feed into improving mathematical modeling of rapid pipe filling, a comparison with a typical one-dimensional rigid-column model is made.

Analytical Expressions for Liquid-Column Velocities in Pipelines With Entrapped Gas

High pressures and high temperatures may arise in pipelines when a liquid column is suddenly accelerated into a gas pocket trapped at a closed end. A mass oscillation occurs that is described by nonlinear equations for both liquid and gas. Analytical expressions are derived for the uniform velocity of the liquid column, from which pressures and gas temperatures follow. The obtained results are validated against theoretical and experimental results published by fellow researchers.