Investigation of quench flow boiling heat transfer correlations for liquid oxygen feed line chill-down with outlet contraction

Abstract

Cryogenic feed lines used for ground-based liquid transfer, thermal management in space flight, as well as the one with an injector at the outlet used for supplying propellants to the cryogenic engine combustion chamber, undergo an initial transient cool-down operation before vapor free liquid supply can be established through them. Accurate prediction of the thermal and hydraulic transients during this period has critical importance in the safe operation and efficient utilization of the cryogen. In the present work, a one-dimensional non-homogeneous two-phase model is used for simulating the chill-down operation in feed lines with and without outlet contraction. For transport feed lines without outlet constriction, the obtained transient wall temperature profiles indicate good prediction when the heat transfer correlations proposed based on recent chill-down experiments are employed as constitutive relations. Subsequently, the numerical model is applied for predicting the wall temperature transients during outlet contracted LOX feed line chill-down. It was noted that built-in heat transfer correlations in thermal–hydraulic code SINDA/FLUINT need revision, especially for rewetting point and heat transfer correlation during post rewetting regimes, for accurate thermal transient predictions during end constrained feed line chill-down. Hence, recent chill-down correlations reported in the literature and the correlations employed in previous chill-down numerical models are tested for their applicability. The recent cryogenic chill-down correlations reported in the literature performed well when applied within the correlation range. However, these correlations over predict the heat transfer at a very high mass flux (order of 3412 kg/m2 s). Hence, modified correlations are proposed for film and nucleate boiling heat transfer coefficients and rewetting temperature.