Liquid Nitrogen Experiments and Simulations using a large-scale Aluminum Test Tank

A new 800 l aluminum test tank built by ArianeGroup for liquid nitrogen and liquid hydrogen experiments was established at the Cryo-Lab at DLR, Bremen. The purpose is to have a liquid hydrogen test tank of future upper stages to conduct cryogenic propellant management experiments. First liquid nitrogen filling, boil-off, and stratification experiments were performed to assess the thermal performance of the tank and investigate the liquid nitrogen behavior in the aluminum test tank. The current boil-off experiment with liquid nitrogen showed a heat flow of about 220 W into the tank. The stratification experiments were conducted at a system pressure of 0.4 MPa and evidenced that the top of the tank was only 23 K warmer than the liquid body, re-creating the unique thermal stratification conditions inside a cryogenic aluminum tank used for upper stages. Detailed transient temperature measurements of the liquid, vapor and tank wall temperature were performed. The stratification experiments were simulated using an in-house 1D tank flow solver. The computations show a good agreement with the temperature measurements with a maximum deviation of 1.8 %. Furthermore, stratification experiments with heating blankets with a power of 240 W were conducted which showed S-shaped temperature profiles consistend with turbulent natural thermal startification