Experimental investigation of hydrogen dispersion characteristics with liquid helium spills in moist air

As green energy, Liquid hydrogen promises to be widely used in the future. However, its security issue has become a great concern because liquid hydrogen will quickly form a low-temperature, flammable, and explosive vapor cloud when leaking or spilling occurs. In this work, liquid helium spilling experiments were designed and performed to predict the dispersion characteristics of liquid hydrogen in confined space with controlled and comparable boundary conditions. The concentration cloud and the infrared cloud images near the liquid helium pool were obtained at the same time. Results show that the air humidity has an impact on the vapor cloud temperature change, i.e., every 10% increase in air humidity will lead to a 5 ℃-temperature increase. The presence of high air humidity increases the vapor cloud buoyancy and promotes the cloud's dispersion in the vertical direction. The visible range of the helium vapor cloud is much smaller than the measured combustible concentration range with air humidity of 50–70%. The helium vapor concentration range at different vertical heights and horizontal distances also increases with the air humidity. The experimental data fits the cloud concentration decay curve under different ambient humidity satisfying the exponential function. The work is expected to provide a technical basis for safety studies of liquid hydrogen and liquid helium spilling. [Display omitted]