Simulation of Chilldown Process with a Sub-Grid Boiling Model

The process of chilling propellant transfer lines, before ignition of liquid rocket engines is initiated is a critical step before launch. Similarly, establishing fuel depots in low earth orbit to replenish propellant supply of long-range exploration missions also places a greater reliance on the chilldown process in ensuring safe and efficient protocols for cryogenic propellant transfer. Over the past few decades, several experiments related to the quenching of heated tubes in a cryogenic environment have been carried out to understand the phase change process and the resulting complex two-phase regimes. These studies have established that the phase change process evolves through different stages of film, transition and nucleate boiling before the walls are quenched and single-phase convective heat transfer between the wall and the cryogenic liquid is restored. Efforts at developing empirical correlations of the heat transfer coefficient and porting it to thermal-fluid codes has resulted in large deviations between predictions and experimental observations of quenching time. The innovation in this proposal involves the development of a comprehensive high-fidelity multiscale simulation framework that accounts for all the boiling regimes related to the chilldown process by utilizing a sub-grid scale nucleate boiling model embedded within a multiphase CFD solver.

Cryogenic propellant storage and transfer is in the critical path of nearly all NASA’s future human exploration missions. The developed tools can result in efficient/reliable protocols for propellant transfer addressing important needs from launch to orbital refueling. Also impacted will be NASA’s Satellite Servicing Capabilities Office which has programs such as the Restore-L and the Robotic Refueling Mission 3 that involve robotically refueling in space to extend the lifespan of satellites through specialized propellant transfer subsystems.

The commercial launch operators can use our tools to estimate propellant quantities and transfer times at launch. Other important applications include the medical industry where applications vary from the preservation of tissues and organs to life-support systems. The technology proposed here can play a critical role in addressing important safety concerns in light water nuclear reactors.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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