“Abstract

The paper considers the concept of efficient liquid hydrogen (LH2) refuelling at hydrogen refuelling stations (HRS), presents modelling approach and 3D transient CFD simulation results. The concept is based on the advantages of transforming hydrogen from equilibrium to a non-equilibrium sub-cooled state (sLH2) during compression at pump. The modelling approach comprises a thermodynamic model of LH2 transfer from the HRS tank to the pump exit and a two-phase CFD model from the pump exit through the HRS equipment, i.e. pipes with bends, automatic valve, breakaway, nozzle, and manifold to onboard storage tanks. Due to the absence of published experimental data, the modelling approach and simulations are verified against conceptual LH2 refuelling process available in the literature. The CFD model reproduces key LH2 refuelling parameters: flow rate, pressure, temperature dynamics, including non-uniform temperature in onboard tanks and predicts pipe cooldown from 88K to allowable temperatures corridor of 23.9–26.5 K.”

 

Molkov V, Ebne-Abbasi H, Makarov D. Liquid hydrogen refuelling at HRS: Description of sLH2 concept, modelling approach and results of numerical simulations. International Journal of Hydrogen Energy 2024;93:285–96.

The full report is accessible via: https://doi.org/10.1016/j.ijhydene.2024.10.392

“Abstract

Hydrogen refuelling is imperative for the emerging market of hydrogen vehicles. The pressure control valve (PCV) at the hydrogen refuelling station (HRS) plays a major role in ensuring that hydrogen delivery to the vehicle follows the prescribed refuelling protocols. A three-dimensional CFD model with a detailed resolution of PCV motion affecting heat and mass transfer is developed. The PCV motion controlling the mass flow rate is simulated using dynamic mesh. The CFD model captures refuelling from high-pressure tanks through entire HRS equipment to onboard tanks, capturing pressure and temperature changes upstream and downstream of the PCV. The Joule-Thomson effect resulting in a hydrogen temperature increase at PCV is captured using the NIST real gas database. The model is validated against Test No.1 of NREL on refuelling through the entire equipment of HRS. The CFD model can be used to design HRS equipment parameters, including PCV, and develop efficient refuelling protocols.”

 

Ebne-Abbasi, H., Makarov, D.  and Molkov, V. (2024) ‘Modelling of refuelling through the entire equipment of HRS: use of dynamic mesh to simulate heat and mass transfer during throttling at PCV’, Hydrogen Safety, 1(1), pp. 12–32.

The full report is accessible via: https://doi.org/10.58895/hysafe.4

“Abstract

An accurate determination of minimum ignition energy (MIE) is essential for assessing electrostatic hazards and characterising potential for occurrence of combustion in flammable mixtures. This is of utmost importance for hydrogen-air mixtures characterised by a MIE equal to 0.017 mJ, whereas conventional flammable gases are characterised by MIE typically higher than 0.1 mJ. The study aims at developing and validating a CFD three-dimensional model capable to simulate complex unsteady physical and chemical phenomena underlying capacitive discharge spark. The model accounts for the experimental apparatus details, including the effect of electrodes’ gap and associated heat losses. The numerical approach accurately reproduced the experimental measurements of MIE for mixtures of hydrogen with air at initial temperature ranging from ambient (T = 288 K) to cryogenic (T = 123 K). Hydrogen concentration in air was included in the range 10–55% for tests at T = 288 K, and 20–60% for tests at T = 173 K and 123 K respectively. Simulations assess the impact of experimental characteristics and design, such as the electrodes’ dimension, and numerical features on process dynamics, growth of the flame kernel and MIE predictions.”

 

Cirrone, D. et al. (2024) ‘Numerical Study of the spark ignition of hydrogen-air mixtures at ambient and cryogenic temperature’, International Journal of Hydrogen Energy, 79, pp. 353–363. doi:10.1016/j.ijhydene.2024.06.362.

The full report is accessible via: https://doi.org/10.1016/j.ijhydene.2024.06.362

“Abstract

The paper describes the breakthrough microleaks-no-burst (μLNB) safety technology of explosion free in fire self-venting hydrogen tanks that do not require thermally-activate pressure relief devices (TPRD). The technology implies melting of the hydrogen-tight liner before hydrogen-leaky double-composite wall loses its load-bearing ability. Hydrogen then flows through the wall’s microchannels and either burns in microflames on its own or together with resin. The experimental validation of the technology is presented for 7 prototypes with the nominal working pressure of 70 MPa made of carbon-carbon or carbon-glass composites. The prototypes are fire tested at the specific heat release rate HRR/A = 1 MW/m² characteristic for gasoline/diesel spill fires. The μLNB technology eliminates catastrophic consequences of tank rupture in fire: blast waves, fireballs, and projectiles. The technology limits hydrogen accumulation in naturally ventilated enclosures. It reduces the risk of hydrogen-powered vehicles to an acceptable level below that for fossil fuel automobiles, including underground parking and tunnels. It provides an unprecedented level of life safety and property protection.”

Molkov V, Kashkarov S, Makarov D. Breakthrough safety technology of explosion free in fire self-venting (TPRD-less) tanks: The concept and validation of the microleaks-no-burst technology for carbon-carbon and carbon-glass double-composite wall hydrogen storage systems. International Journal of Hydrogen Energy, Volume 48, Issue 86, 22 October 2023, Pages 33774-33785.

The full publication is accessible via: https://www.sciencedirect.com/science/article/pii/S0360319923024448

“Abstract

This study compares four computational fluid dynamics (CFD) models, i.e. k-ε, RSM, SAS, and LES, to simulate temperature non-uniformity during hydrogen tank refuelling. Three grids with a total number of control volumes of 64k, 363k, and 2.9 M were used. The maximum dimensionless wall distances, y+, were 80, 5 and 2.5, respectively. The predictive capability of the models was assessed by recommended statistical indicators using ten thermocouple locations during 620 s of the experiment. The comparative analysis demonstrated a better predictive capability of temperature non-uniformity and stratification by the LES model and a shorter simulation time. It is concluded that meshes with y+ larger than 80 would overpredict the average hydrogen temperature while meshes with y+<5 provide a good simulation accuracy. The results underline the importance of the turbulence model choice and the numerical grid resolution for proper prediction of temperature non-uniformity during hydrogen tank refuelling.”

 

Xie, H. et al. (2024) ‘Comparative analysis of CFD models to simulate temperature non-uniformity during hydrogen tank refuelling’, International Journal of Hydrogen Energy, 70, pp. 715–728. doi:10.1016/j.ijhydene.2024.05.047.

The full report is accessible via: doi:10.1016/j.ijhydene.2024.05.047

“Abstract:

Liquid ammonia stored at elevated pressures undergoes phase change during tank venting. The paper describes a CFD model able to reproduce the INERIS experiment performed using 12 m3 volume tank when 300 kg of ammonia were vented during 460 s from the ullage through the pipe to the atmosphere. The model is based on the volume-of-fluid method combined with Lee’s model for mass transfer between phases. Extensive calibration trials were conducted to examine the impact of surrounding temperature conditions. It allowed to establish the range of time relaxation parameter values of Lee evaporation-condensation model specific for liquid ammonia tank venting. Simulations reproduced accurately the experimentally measured final pressure in the tank and the amount of ammonia released during venting. Liquid ammonia boiling is triggered by reduction of pressure and takes place throughout the liquid causing the pressure recovery phenomenon. Numerical simulations demonstrated that pressure recovery phenomenon is driven by the characteristic time delay associated with the rise of vapour bubbles generated by flash boiling and the subsequent release of evaporated ammonia into the tank ullage space. The developed CFD model can be used as a contemporary tool for safety engineering and development of tank management strategies for liquid ammonia storage.”

 

Sivaraman, S., Makarov, D. and Molkov, V. Flash boiling and pressure recovery phenomenon during venting from liquid ammonia tank ullage. Process Safety and Environmental Protection, 2024;182: 880-893. https://doi.org/10.1016/j.psep.2023.12.037

The full report is accessible via: https://doi.org/10.3390/su16041620