Simulation of hydrogen tank refueling
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Several simulations of hydrogen filling process for a type IV tank were completed usingopenFOAM Computational Fluid Dynamics (CFD) open-source code. CFD codes have beenproven to be a useful method for estimating temperature and pressure distribution developedinside the tank during refueling operations. All simulations were completed in a 2-D mesh andfor a simulated time of 20 seconds with varying initial tank pressures and mass flow rate at theinlet. The transient, compressible and heat transfer rhoCentralFoam solver was used along withthe k-ω SST turbulence model to reproduce the effects of compressibility of the gas during thefilling.The simulation cases were designated into two groups for comparing a 10 to 50 g/s mass flowrate, along with different initial tank pressures of 1, 5, 10, 20, 30 and 35 MPa. The gas inlettemperature was 273.15 K, with an initial tank and walls temperature of 298.15 K. Surroundingtemperature was selected as 298.15 K with a constant convective transfer coefficient of 10 W/m2K. The simulated wall thickness is 5 mm with a thermal conductivity of 0.4 W/m K forsimulating a polymer liner.Results for the temperature and pressure distribution within the tank are in agreement withprevious research papers’ findings for which larger initial pressures lead to minor increments intemperature during refueling. Larger initial pressures resulted in less gas velocities at the inlet.Temperature rise is heavily dependent of the inlet gas mass flow, as a higher flow will result inmore mass dispensed into the tank. The applicability of these findings suggests that at the start ofthe gas refueling process, a low mass flow rate can be dispensed, as the instant change intemperature is smaller, and once a higher pressure is developed within the tank, increase themass flow to achieve a faster fill.The convective heat transfer coefficient is influenced by the mass flow rate. For lower initialpressure simulations, higher values are achieved at the end region of the tank, far away from theinlet, due to gas compression. In some instances, negative coefficient values were developed, astank wall temperature went lower than initial temperature condition, leading to a negative heatflux into the tank.Higher initial pressure cases resulted in oscillations of the variables through the simulation.Finer mesh analysis is suggested to verify mesh dependency.