Hydrodynamic and Thermodynamic Behavior of Liquid Methane in a Vertical Feed Pipe

During the chill-down procedure for a space application system, a multiphase flow of extremely cold propellants will undoubtedly occur in the feed lines. Due to flow instability and varying cooling rates, this cooling technique produces dynamic changes that are challenging to control. Over the past few decades, research has extensively examined the multiphase behaviour of various cryogens, such as liquid nitrogen, liquid hydrogen, and liquid oxygen, while few studies focus on liquid methane. This study addresses this gap by investigating the hydrodynamic and thermodynamic characteristics of LCH₄-VCH₄ multiphase flow in a vertical cryogenic pipe using a well-validated, three-dimensional Volume of Fluid (VOF) model. Further, the current study employs an Eulerian flow scheme coupled with an energy equation to accurately capture the multiphase flow dynamics of liquid methane across various inlet velocities and temperatures. The volume fractions are used to investigate the flow pattern, and the interaction between the two phases and the two-phase flow structure is investigated using velocity profiles and phase distribution. Further, the bulk mean and near-wall temperature results were analysed to understand the temperature variation inside the pipe. Increased inlet temperatures at constant velocities enhance vapour volume fractions, while higher velocities reduce vapour generation, leading to decreased bulk mean temperature due to reduced heat transfer. However, a significant rise in vapour flow rates occurs at elevated temperatures with constant velocity. The volume fraction results show the formation of bubble, annular, and slug flow patterns in the flow regime.