Numerical modelling of heat transfer and evaporation characteristics of cryogenic liquid propellant

Abstract

Passive and active technologies have been used to control propellant boil-off, but the current state of understanding of cryogenic evaporation and condensation in microgravity is insufficient for designing large cryogenic depots critical to the long-term space exploration missions. One of the key factors limiting the ability to design such systems is the uncertainty in the accommodation coefficients (evaporation and condensation), which are inputs for kinetic modeling of phase change. A novel, combined experimental and computational approach is being used to determine the accommodation coefficients for liquid hydrogen. The experimental effort utilizes the Neutron Imaging Facility located at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland to image evaporation and condensation of propellants inside of metallic containers. CFD tools are utilized to infer the temperature distribution in the system and determine the appropriate thermal boundary conditions for the numerical solution of the evaporating and condensing liquid to be used in a kinetic phase change model. Using all three methods, there is the possibility of extracting the accommodation coefficients from the experimental observations.