Prediction of liquid hydrogen flow boiling critical heat flux condition under microgravity based on the wall heat flux partition model

摘要

Critical heat flux (CHF) of liquid hydrogen (LH2) flow boiling under microgravity is vital for designing space cryogenic propellant conveying pipe since the excursion of wall temperature may cause system failure. In this study, a two-dimensional axisymmetric model based on the wall heat flux partition (WHFP) model was proposed to predict the CHF condition under microgravity including the wall temperature and the CHF location. The proposed numerical model was validated to demonstrate a good agreement between the simulated and experimentally reported results. Then, the wall temperature distribution and the CHF location under different gravity conditions were compared. In addition, the WHFP and vapor-liquid distribution along the wall under microgravity were predicted and its difference with terrestrial gravity condition was also analysed and reported. Finally, the effects of flow velocity and inlet sub-cooling on the wall temperature distributions were analysed under microgravity and terrestrial gravity conditions, respectively. The results indicate that the CHF location moves upstream about 5.25 m from 1g to 10(-4) g since the void fraction near the wall reaches the breakpoint of CHF condition much earlier under the microgravity condition. Furthermore, the increase of the velocity and decrease of the sub cooling have smaller effects on the CHF location during LH2 flow boiling under microgravity. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.