Development of constitutive relations for predicting film boiling crisis in bare and inner wall coated cryogenic tubes with a low-thermal conductive layer for heat transfer enhancement

Closure models for transient cryogenic quench flow boiling heat transfer prediction are finding significant attention to support the design of energy -efficient, cost-effective, and reliable cryogenic fluid management systems. In this regard, the characterization of the film boiling crisis, which indicates the beginning of transient wetting of the wall by liquid, is essential due to the significant heat transfer change past this stage. In the current work, a new rewetting database is developed from 112 chill -down experiments conducted using LCH4, LOX, LAr, and LN2 in feed lines having 0.11 m to 11 m length, 0.4 cm to 2.2 cm inner diameter, 0.5 mm to 5 mm wall thickness, and low -thermal conductive coating thickness up to 157 mu m, under several pipe orientations. Additionally, the dataset comprises a mass flux from 10.5 kg/m2s to 1805 kg/m2s, pressure from 109.8 kPa to 1153.8 kPa and gravitational acceleration from terrestrial condition to +/- 0.01 g. Subsequently, 30 existing seminal rewetting correlations are analyzed for their applicability to transient cryogenic rewetting prediction. Moreover, the importance of feed line and flow parameters in this phenomenon is also studied. Accordingly, a new correlation for rewetting temperature is proposed with 4.15% mean absolute percentage error (MAPE). Further, applying a low -thermal conductive coating to the feed line inner wall surface has already been proven to enhance the chill -down efficiency up to 80%. For modeling such feed systems, determining bulk wall rewetting point is necessary. Hence, a new apparent rewetting temperature correlation to characterize the film boiling crisis in cryogenic coated tubes is proposed for the first time with a MAPE of 4%. Finally, the paper presents the predictions from a non -homogeneous two-phase thermal -hydraulic code, employing the previously reported film boiling correlations and the rewetting correlations from the present work. The obtained model performance indicates considerable improvement in prediction while using the proposed closure models. This shows their potential to support optimization tasks to achieve higher chill -down efficiency.