Low Thrust Cryogenic Propulsion (LTCP) systems [1] need a thermal energy storage acting as a heat accumulator, where a cryogenic flow of (LOx) propellant is gasified inside, under a fast transient evaporation process. The heat accumulator is heated by means of a secondary fluid (typically He or N2) which is exchanged from fuel cells. The heat exchanged or stored between both fluid flows is assured by means of a thermal energy storage tank filled of a Phase Change Material (PCM). A numerical model of the thermal and fluid-dynamic behavior of the two-phase flow inside ducts working under cryogenic conditions, coupled with the analysis of the PCM accumulator is proposed [2]. The numerical analysis is based on: i) a one-dimensional and transient integration of the governing equations (conservation of mass, momentum and energy) for the fluid flow of propellant, and ii) a multi-dimensional and transient integration of the conservative governing equations in the region occupied by the PCM, taking into account turbulence modeling for solving the convection phenomena involved. The solid elements are modeled considering a multidimensional and transient treatment of the thermal conduction equation. The numerical results are experimentally validated by means of a series of experimental tests [3] [4]. The comparative analysis shows the good agreement between both numerical results and experimental data. Different results under working conditions of the cryogenic flow and/or the PCM material, shows the possibility of this model for design optimization purposes.

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