Cryogenic propellants are going to be the cornerstone for effective future human
space exploration. These propellants need to be stored and maintained at really low
temperatures for a long duration. Accurate phase change modeling is necessary for
characterizing the thermal state of future cryogenic propellant tanks and for designing
systems to alleviate the self pressurization problem. Better understanding about
how to properly store and manage cryogenic propellants would help greatly with In-Situ Resource Utilization (ISRU) strategies for future missions to Mars and further.
Predicting the fluid flow, heat transfer, and phase change mass transfer in long term
cryogenic storage using CFD models is greatly affected by our understanding of the
accommodation coefficient. The kinetically limited phase change model governed
by the Hertz-Knudsen-Schrage equation is the model of choice for such calculations.
The value of the accommodation coefficient required for the model is unknown for
cryogenic propellants. Even in the case of water, the value of the accommodation
coefficient has been found to vary over three orders of magnitude based on 80 years
of measurements. Experiments specifically built to study accommodation coefficient
are needed to estimate the value of the accommodation coefficient and understand
some of the uncertainties surrounding these models. <div><br></div><div>Two phase change models, viz. the thermally limited and the kinetically limited
phase change model are implemented in OpenFOAM. Different approaches to implement the Hertz-Knudsen-Schrage equation in a sharp interface conjugate heat transfer
solver are studied. Evaporation and condensation calculations for a liquid hydrogen
meniscus inside an aluminum container are compared with experimental measurements. The effect of accommodation coefficient on phase change is then studied with
the kinetically limited model by comparing with the thermally limited model and
the experimental measurements. The uncertainties associated with the temperature
and pressure measurements in the experiment are quantified to show their effect on
computational predictions. Since cryogenic propellants are perfectly wetting fluids,
modeling the thin-film region close to the contact line leads to a multi-scale computational problem. However, the phase change contribution from the thin-film region is
approximated in these computations to show the importance of modeling the contact
line region accurately to adequately capture the small local thermodynamics in that
region.</div>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/11319977 |
| Date | 05 December 2019 |
| Creators | Praveen Srikanth (8082695) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/Innovations_in_Modeling_Cryogenic_Propellant_Phase_Change_for_Long_Duration_Spaceflight/11319977 |
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