Buoyant Jet Model to Predict a Vertical Thermal Stratification During Refueling of Gaseous Hydrogen Tanks in Horizontal Position with Axial Injection

Thermodynamic modeling of hydrogen tank refueling, i.e. 0 dimension (0D) model, considers the gas in the tank as a single homogeneous volume. Based on thermodynamic considerations, i.e. mass and energy balance equations, the gas temperature and pressure predicted at each time step are volume-averaged. These models cannot detect the onset of the thermal stratification, nor the maximum local temperature of the gas inside the tank.
For safety reasons, the temperature must be maintained below 85 °C in the composite tank. When thermal stratification occurs, the volume-averaged gas temperature predicted by 0D models can be below 85 °C while local temperature may significantly exceed 85 °C. Then, thermally stratified scenarios must be predicted to still employ 0D models safely.
Up to now, only computational fluid dynamics (CFD) approaches can predict the onset of the thermal stratification and estimate the amplitude of thermal gradients. However, CFD approaches require much larger computational resources and CPU time than 0D models. This makes it difficult to use CFD for parametric studies or a live-stream temperature prediction for embedded applications. Previous CFD studies revealed the phenomenon of jet deflection during horizontal refueling of hydrogen tanks. The cold hydrogen injected into the warm gas bulk forms a round jet sinking down towards the lower part of the tank due to buoyancy forces. The jet breaks the horizontal symmetry and dumps the cold gas towards the lower part of the tank.
The jet behavior is a key factor for the onset of the thermal stratification for horizontally filled tanks. Free round jets released in a homogeneous environment with a different density than the jet density were extensively investigated in the literature. A buoyant round jet modeling can be applied to predict the jet deflection in the tank. It requires initial conditions that can be provided by 0D refueling models. Therefore, 0D models coupled with a buoyant round jet modeling can be used to predict the onset of the thermal stratification without CFD simulation. This approach clarifies the validity domain of 0D models, and thus improves the safety of engineering applications