Numerical experiment on the effect of a number of baffles on evaporation rate in a liquid hydrogen tank

In a liquid hydrogen tank, the sloshing phenomenon and the evaporation rate of liquid hydrogen are crucial for design. One way to suppress sloshing is by inserting baffles inside the tank. Various baffle designs have been developed to reduce sloshing pressure, and it is known that increasing the number of baffles can be beneficial. However, there is a lack of analysis on the impact of the number of baffles on evaporation rates in the cryogenic environment of a liquid hydrogen tank. This study explores the influence of the number of baffles on the evaporation rate within a liquid hydrogen tank by conducting numerical experiments. We conduct these numerical experiments by varying the number of baffles from 0 to 4 without applying heat flux to the baffle walls. A constant heat flux is imposed only on the tank wall. Both liquid hydrogen and gaseous hydrogen are assumed to be Newtonian, incompressible, immiscible, and non-isothermal fluids. The liquid hydrogen initially fills 50 % of the tank volume, and the tank is decelerated by 0.425 g, which corresponds to a tank moving at 60 km/h, coming to a stop in 4 seconds. For the case with four baffles, the maximum instantaneous evaporation rate is 0.0894 kg/s higher compared to the case with three baffles. Most of the evaporation occurs in the compartment opposite to the direction of the tank's movement. In this compartment, gaseous hydrogen, restricted from moving to the other partition by a baffle, is heated and simultaneously generates hot bubbles within the liquid hydrogen, leading to a higher evaporation rate. Despite the baffles reducing sloshing, an increase in their number could lead to a rise in evaporation. Considering the low density of hydrogen and the relatively low dynamic pressure from sloshing, fewer baffles than those used in conventional liquid fuel tanks may be necessary to minimize the evaporation rate.