A New Experiment for Determining Evaporation and Condensation Coefficients of Cryogenic Propellants
Kishan Bellur, E F. Medici, M Kulshreshtha, V Konduru, D Tyrewala, A Tamilarasan, J McQuillen, Juscelino Leao, Daniel S. Hussey, David L. Jacobson, Julia K. Scherschligt, J Hermanson, C Choi, J Allen
Passive and active technologies have been used to control propellant boil-o , but the current state of understanding of cryogenic evaporation and condensation in microgravity is insucient 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 coecients (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 coecients for liquid hydrogen and liquid methane. The experimental e ort utilizes the Neutron Imaging Facility located at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland to image evaporation and condensation of hydrogenated propellants inside of metallic containers. The computational e ort includes numerical solution of a model for phase change in the contact line and thin film regions as well as an computational modeling e ort for determining the appropriate thermal boundary conditions for the numerical solution of the evaporation liquid. Using all three methods, there is the possibility of extracting the accommodation coecients from the experimental observations. The experiments are the first known observation of a liquid hydrogen menisci condensing and evaporating inside aluminum and stainless steel cylinders. The experimental technique, complimentary computational thermal model and meniscus shape determination are reported. The computational thermal model has been shown to accurately track the transient thermal response of the test cells. The meniscus shape determination suggests the presence of a finite contact angle, albeit very small, between liquid hydrogen and aluminum oxide.