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Hydrogen has been widely recognized as an energy source to replace fossil fuel due to its environmental friendly element and renewable properties. However, it also has disadvantages such as a wide range of flammability (4 ~ 75%), low minimum ignition energy (0.2mJ), etc. So, there have been studies to prevent explosions by creating ventilation systems which focus on effectively releasing leaked hydrogen gas. Despite hours of ventilation, several experimental results show the concentration still being maintained higher than 4%. Therefore, it is necessary to consider the countermeasures to minimize damage when explosion actually occurs due to the incomplete effect of ventilation. In this study, the FLACS Computational Fluid Dynamics(CFD) program was used to verify the reduced damage when the Explosion Venting Panel(EVP), which discharges overpressure and unburned gas, is applied in comparison to the enclosed hydrogen facilities that can give the biggest damage. The model was designed based on the test bed created with the same specifications as the low-pressure hydrogen facilities built in Ulsan, Korea. Until now, existing EVP studies attempted to prove how well their models fit with the actual experiments. However, those studies did not show the level of damage caused by overpressure. So, this study aims to provide a concrete numerical value of the damage caused by the explosion and to express damaging levels this value can cause. First, the size, number, and location of the EVP are selected to find the optimal placement. Second, scenarios are chosen according to the Korea Occupational Safety and Health Agency(KOSHA) guide. They are then, simulated based on the first criterion. Lastly, the installation distance of the blast wall is suggested in consideration of the damage to the surrounding facilities. As a result, with the frequently occurring accident case, the measured overpressure in the EVP applied case was 35% lower than that of the enclosed hydrogen facilities. In addition, the pressure measured less than 0.069 barg, a safely considered measure in all methods applied in the first criterion, proving the installation of the EVP as an effective solution. However, in the worst case, even with the installation of the EVP, the overpressure over the 0.069 barg was measured up to a 5m radius to the low-pressure hydrogen facilities. Therefore, it was confirmed that installation of blast wall was necessary as a mitigation plan. In conclusion, with the occurrence of hydrogen explosion, EVP applied resulted in lower overpressure than that of the enclosed hydrogen facilities. This study provides concrete numerical values for both the overpressure and the damage distance caused by the explosion. It also suggests an alternative to minimizing the damage, which is expected to be important reference when applying EVP and building a blast wall in various hydrogen related facilities. |
