An experimental study on terrestrial cryogenic tube chilldown II. Effect of flow direction with respect to gravity and new correlation set

Abstract This is the second of a two-part series of papers which presents the experimental results of a parametric series of liquid nitrogen chilldown tests of a stainless steel tube. Whereas the first paper in this series focused on the effect of mass flux, inlet subcooling, equilibrium quality, pressure, and axial distance from the inlet on two-phase convection heat flux for vertical upward flow only, this paper focuses on the effect of flow direction with respect to gravity. Nine different flow directions were examined, including horizontal, 30° inclined and declined, 45° inclined and declined, 60° inclined and declined, and vertical upward and downward. The experimental data covers liquid Reynolds numbers ranging from 800 to 230,000 and local pressures ranging from 150 to 725 kPa. Analysis is presented on the effect of flow direction on the measured film, transition, and nucleate boiling heat transfer coefficients as well as the critical heat flux. Finally, new heat transfer correlations to predict the data are presented for film boiling, nucleate boiling, and transition boiling. These correlations can be used for numerical simulations of cryogenic chilldown to help predict the chilldown time and propellant consumption for different system variables.