The study of one of the components, the heat accumulator, of Low Thrust Cryogenic Propulsion systems (LTCP), is of scientific interest in the framework of ISP-1 project [1]. This device stores thermal energy from the fuel cell that provides electrical energy to the whole system. This thermal energy is employed for the pressurization of the propellant tanks. Two different types of heat accumulators are present in the LTCP system: the High Temperature Accumulator (HTA) and the Low Temperature Accumulator (LTA). A numerical model is being developed [2] in order to predict the thermal behavior of the LTA and having a tool for its design in the next future. Experimental results of ISP-1 partners of DLR are being used for the validation [3], [4].