Numerical study on the performance of a forced ventilation system under hydrogen leakage in an underground hydrogen equipment room

This study aims to establish a foundation for developing a ventilation system to address potential hydrogen leakages in underground equipment. The dimensions of this space are 4.2 × 2.2 × 2.2 m³. It features main and auxiliary inflow vents and fan outflow vents. Using the commercial software ANSYS Fluent, a three-dimensional transient RANS is performed to analyze hydrogen diffusion phenomena during a leakage using mass, momentum, and species-conservation equations. The study obtains numerical analysis results by varying the number of fans, open/closed state of the main inflow vent, leakage nozzle diameter, and leakage flow rate. In addition, the study examines the spatial distribution of hydrogen concentration within the room and its temporal variations at various points. The ventilation performances for different scenarios are compared and an effective ventilation method is discussed. Additionally, this study proposes the simple model to predict the volume-averaged hydrogen concentration over time and evaluates it by comparing with numerical results. The simple model effectively predicts the trend of the volume-averaged hydrogen concentration, and reasonably predicts the time at which the volume-averaged hydrogen concentration attains 1 and 4 vol%.