A Direct Numerical Simulation of Axisymmetric Cryogenic Chill Down in a Pipe in Microgravity.

Cryogenic two-phase flow with phase change heat transfer, consisting of a saturated liquid slug translating in its own superheated vapor in a circular pipe, was numerically simulated. The cryogenic chill down process was simplified by assuming ideal inverted annular flow regime. The method used is based on a sharp interface concept and developed on an Eulerian Cartesian fixed-grid with a cut-cell scheme and marker points to track the moving interface. The unsteady, axisymmetric Navier-Stokes equations in both liquid and vapor phases are solved separately and used to compute the velocity, pressure, and temperature fields and the deformation of the liquid core very accurately. Three most common cryogenic fluids, viz. nitrogen, oxygen, and argon were included in the study. The influence of non-dimensional parameters like Reynolds number $$Re,$$ Weber number $$We$$ , and Jakob number $$Ja$$ on flow characteristics was studied by systematically varying only one at a time. $$Re$$ was found to affect the mass flow rates, but did not have a significant influence on the wall cooling or the Nusselt number. $$We$$ affected the interface shape at the leading edge of the liquid slug, also influencing the heat transfer and velocity field there. $$Ja$$ affects all three quantities of interest, i.e., mass flow rate, wall cooling, and the Nusselt number. [ABSTRACT FROM AUTHOR]