Chill-down in LN2 Transfer Line Initially Filled with Air: A Transient Analysis

Abstract

Some of the crucial issues in cryogenics industries are handling, transporting, and storing cryogens. Chill-down is the first stage in the cryogen transportation process, and it involves multiphase flow. Before single-phase liquid can flow through the connecting transfer line, it must first be chilled down to cryogenic temperatures. The present study attempts to explore the transient three-phase flow characteristics during chill-down in a long circular pipeline carrying LN2 flow where the pipeline is initially filled by air. LN2 flows of various Reynolds no. (Re) values are considered at the inlet of the pipe. The FVM-based VOF model coupled with the Lee model of phase change is employed for the present transient numerical simulation. k-ω model is employed for turbulence modeling. The study focuses on exploring flow characteristics in terms of the spatial distribution at different time instants for the air volume fraction (VF), gaseous N2 VF, pressure, velocity magnitudes, etc. Time variations of area-weighted average (AWA) air VF, gaseous N2 VF, pressure, velocity magnitude, and temperature at different cross-sectional planes are also extracted to depict the results.