Data from cryo-neutron phase change experiments with LH2 and LCH4

This dataset describes both raw and analyzed results from liquid-vapor phase change experiments with cryogenic propellants. Evaporation/condensation experiments with hydrogen and methane were conducted at the National Institute of Standards and Technology (NIST) in Gaithersburg, MD at the NIST Center for Neutron Research (NCNR). Tests were conducted in cylindrical and conical containers of various sizes and materials. Neutron imaging was used as a non-destructive visualization tool to probe inside the opaque metallic containers. Phase change (evaporation/condensation) was induced through precise control of pressure and/or temperature. Saturation points between 80 - 230 kPa were tested. Evaporation/condensation rates were determined through image processing. The motivation behind the experiments were to determine the accommodation coefficient which are inputs to kinetic models of phase change that represent the ratio of molecules that cross the liquid vapor interface. The values of the coefficients are published elsewhere and the data (images, temperature and pressure) are provided here. To the authors' best knowledge, these are the first known neutron images of controlled cryogenic propellant phase change. The unique dataset contains a wealth of information on meniscus evaporation/condensation, phase change dynamics, thin film formation, capillary wicking, cryogenic heat transfer and neutron imaging statistics. The data could also be used as a benchmark for future experiments or as a dataset for model validation.