CFD analysis of hydrogen fast-filling process

The surge in hydrogen-fueled electric vehicles has increased the need for reliable, safe, and efficient refueling methods. During filling of high-pressure Type IV hydrogen tanks, the gas temperature rises significantly due to compression and turbulence, sometimes exceeding the safe limit of 358 Kelvin specified by fueling standards. Elevated temperatures can compromise the cylinder’s structural integrity and reduce the available volume during refuelling. Consequently, thermal management in hydrogen storage systems is crucial. This study employed Computational Fluid Dynamics using ANSYS Fluent to analyse thermal performance during rapid cylinder filling. The model was two-dimensional, axisymmetric, simulating a composite Type IV cylinder, and solved governing equations for mass, momentum, and energy. A realisable k - ε turbulence model and hydrogen’s real gas properties were used, based on established thermodynamic principles. The transient simulation reveals how temperature, pressure, and flow evolve over time during filling. High gas temperatures arise from thermal accumulation and limited convection time, occurring last in the cylinder. The peak temperature, reaching about 390-420 K, occurs early during filling and remains stable through the first stage. As heat transfers to the cylinder wall, the gas temperature drops slightly due to the time lag in heat transfer between injection and the wall. The study emphasises the importance of pre-cooling mechanisms in hydrogen refuelling systems. Without suitable pre-cooling, temperatures can exceed safe levels during fast filling, impairing efficiency and commercial viability. It recommends developing a B2B ecosystem incorporating chiller-based pre-cooling, optimised refuelling protocols, and hydrogen tank manufacturing integration. Such an ecosystem is essential for safe, cost-effective, large-scale adoption, especially in high-demand sectors like heavy-duty transport. Findings underline the necessity of pre-cooling strategies, including inlet pre-cooling and pressure ramp-up techniques, to prevent temperature surges and ensure safe, efficient hydrogen refilling.