Numerical Modelling of Transient Chill-Down Operation in Liquid Methane Transfer Line

An accurate chill-down model is essential for the efficient design of cool-down operation in the cryogenic transfer line, which is crucial for optimized propellant usage in space flights. Heat transfer constitutive relations play a vital role in the accuracy of the thermo-hydraulic code used for this purpose. Hence, the recently proposed correlations in the literature for various two-phase boiling regimes and their transition criteria are investigated for their applicability to LCH4 chill-down using a non-homogeneous two-phase model. Built-in correlations in SINDA/FLUINT (S/F), correlation sets based on LN2 and LH2 cryogens, correlations reported based on LOX and LAr data, and correlations employed in previous chill-down models are studied. Though available correlation could predict rewetting temperature within 11% MAE, higher deviations are noted in the film boiling regime, which persists for the significant duration of the LCH4 chill-down period. Nevertheless, S/F built-in correlations and the chill-down correlation set based on LN2 and LH2 cryogens gave a rough estimate for the wall thermal transients and a reasonably good prediction for the chill-down duration.