Cryogenic propellant rockets, designed to exploit the high energy densities of liquid hydrogen and liquid oxygen, are equipped with turbopumps that deliver liquid fuel to the engine at high pressure levels. Due to the very low saturation temperature of the cryogenic propellant, it is common during the transient operation to have portion of pump walls that achieve boiling conditions. The effect of boiling on the heat transfer between the solid and the fluid needs to be well characterized in order to correctly predict the pump metal temperature evolution and the necessary amount of propellant.This paper presents an investigation about the capabilities of currently available CFD models for boiling to reproduce correctly the phenomenon under various flow conditions. The analysis, conducted with Ansys Fluent CFD solver, focuses on the Eulerian multiphase approach coupled with the mechanistic nucleate boiling model and its extensions to consider the wall boiling regime transition from the nucleate boiling to critical heat flux (CHF).Several test cases are presented to cover the full range of boiling regimes and flow characteristics: first test focuses on nucleate boiling of sub-cooled water in an upward heated cylindrical pipe, second one deals with 3D boiling flows in a rectangular-sectioned duct, while the third one investigates the critical heat flux and post dryout in vertical pipes. Selected tests span over different operating conditions and consider alternative fluids in order to provide a preliminary validation propaedeutic for future investigation focused on more complex applications representative of cryogenic turbopumps.

Assessment of Cfd Models for Multiphase Heat Transfer in Different Boiling Regimes

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2021/volume/84898

Turbo Expo 2021

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