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 and in-space propulsion. Similarly, reliable engine operations, require flow to be conditioned, devoid of two-phase content and pool/flow boiling considerations impact cryogenic tank propellant management. The chilling/quenching of propellant lines undergo complex flow patterns involving film boiling, transition boiling, nucleate boiling and single phase convective heat transfer. In Phase I, a mesoscopic boiling model was integrated into a high-fidelity multi-physics simulation framework and quenching of vertical tubes with cryogenic fluids under terrestrial and microgravity conditions were demonstrated. In Phase II, experiments providing data of important sub-model closures involving bubble departure diameter, frequency and nucleation site density for cryogenic fluids are planned. These measurements aided with machine learning algorithms will help in improving the accuracy of correlations and closure models. Furthermore, the boiling model will be enhanced involving additional physics related to surface wettability, bubble sliding effects, solid wall quenching etc along with substrate roughness that affects convective heat transfer and nucleation. Detailed validation studies are planned with hydrogen and nitrogen under normal gravity and microgravity conditions and boiling model framework will be ported to NASAs codes to support mission related activities. The process of chilling propellant transfer lines, and concepts of flow and pool boiling in microgravity are integral to providing reliable cryogenic fluid storage and transfer for use in propulsion and life support systems. The chilling/quenching of propellant lines undergo complex flow patterns involving film boiling, transition boiling, nucleate boiling and single phase convective heat transfer.  In this program, in collaboration with MIT, technology involving a mesoscopic boiling model is being integrated into a multi-physics simulation framework to carry out quenching studies of cryogenic propellant feedlines under terrestrial/microgravity conditions.  The technology will be able to predict cooling rates, two-phase flow quality, heat flux needed for tank-to-tank transfers, chilldown of feedlines in engine start-up protocols, and propellant storage boil-off.  Detailed validation studies and experiments are planned with cryogens under normal gravity and microgravity conditions and the boiling model framework will be ported to NASA’s codes to support mission related activities. The technical objectives revolve around improving chilldown predictions for cryogenic applications with experiments and software development. They involve: Enhancing the boiling model closures for key parameters involved in the boiling process such as bubble departure diameter, frequency and nucleation site density through the investigation of similarity criteria between water and cryogenic data; Carry out a series of pool boiling experiments with cryogens and use imaging techniques such as backlit shadowgraphy and total internal reflection to image the vapor and gas phases on the boiling surface. Consequently use measurements from the image processing to develop correlations of important parameters using machine learning;  Update the sophistication of the boiling model by including effects of wettability, nature of the substrate, microlayer dynamics and bubble sliding effects; Improve predictions due to effects stemming from convective heat transfer due to surface roughness and interaction of bubble dynamics with the bulk flow.  Proposed deliverables are a (i) multi-scale multi-physics simulation framework integrated with a mesoscopic boiling model from MIT. (ii) experimental data and machine-learning based correlations for use in NASA codes (iii) modules for NASA CFD codes  to support cryogenic flow management technology in exploration missions.

Cryogenic propellant storage and transfer are integral to nearly all NASA’s future human exploration missions. The tools developed here can result in efficient and reliable protocols for propellant transfer addressing important needs for such missions from launch, in-space engine start-up to orbital refueling. Furthermore, pool boiling and flow boiling impact several key elements of propellant tank cryogenic fluid management in microgravity. Since the chilling of transfer lines is an indispensable part of launch, the commercial launch operators can use our prediction tools to estimate propellant quantities and transfer times. Other important applications include the medical industry where applications vary from the preservation of tissues and organs to life-support systems.

This is early/mid-stage (TRL 4) — 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.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.