Extension of a Standard Flow Solver for Simulating Phase Change in Cryogenic Tanks

Cryogenic-liquid-propelled rockets are equipped with tanks containing subcooled liquid propellants such as hydrogen and methane. The pressure evolution in such tanks is governed by the heat exchange of the vapor with the tank walls and liquid surface and the phase change at the liquid vapor interface. Because phase change is a major driver for the pressure evolution, the accurate prediction of the phase change rate is of crucial importance for the design of cryogenic liquid tanks and their pressurization systems. Therefore, in this study the commercial multiphase flow solver FLOW-3D (R) is extended with a customized phase change model based on the temperature gradients at the phase boundaries. The clear advantage of the temperature gradient model over, for example, kinetics-based models is that it contains no model constants. To validate the customized phase change model, liquid evaporation at a heated wall, liquid evaporation at a superheated liquid body at a wall, the bubble growth problem in superheated liquid, and meniscus evaporation in a heat pipe are considered. The numerical solutions of all computations show a good agreement with reference solutions. Furthermore, the phase change model is applied to the microgravity tank flow problem SOURCE-2, where HFE-7000 evaporates at a superheated wall. With the new phase change model, FLOW-3D is able to predict the pressure evolution with a maximum deviation of 0-20% compared with measurements.