Efficient Models for Film Condensation in Cryogenic Tank Applications

To support NASA’s Cryogenic Fluid Management (CFM) design and operation initiatives subgrid computational fluid dynamics (CFD) models of cryogenic condensation/liquification are required to allow for efficient trade studies to be conducted on real systems over a range of conditions that may be prohibitive with laboratory testing. In the Phase I effort, a validated subgrid CFD model of cryogenic film condensation on a vertical flat wall will be developed which is capable of capturing the formation and growth of a cryogenic condensation layer and its movement along a wall boundary. A systematic test campaign will be undertaken to investigate the downflow film condensation of oxygen which is of relevance to CFM and In-Situ Resource Utilization (ISRU) initiatives. The Phase I test effort emphasizes experimental visualization of the onset of film condensation, understanding of relative importance of heat transfer processes, quantification of key film characteristics, including liquid film thickness, vapor thermal boundary layer, and condensation heat flux, and identification of governing parameters that influence cryogenic film formation and growth. The experimental data will be used for fundamental validation of a subgrid cryogenic film condensation CFD phase-change model, setting the stage for a Phase II validation program on prototype CFM geometries. The Phase II effort will extend the validation to tank geometries and incorporate the validated film condensation model into commercial CFD tools used by NASA. The validated predictive simulation tools will help in identifying better designs and protocols related to cryogenic propellant transfer and ISRU thereby mitigating risk in outer space hardware deployment and operational strategies.