Mixing and Stratification Phenomena Under Natural Convection in the Multi-Openings Compartment

Abstract

The mixing and stratification of hydrogen-vapor-air in the compartment is extensively studied under inertia jets and turbulent buoyant jets. The characteristics of buoyancy-driven flows during fission and fusion reactor accidents need to be further studied to provide a benchmark for the validation of computational procedures. In this paper, a large-scale facility of a vessel with multiple openings is established to study the mixing and stratification of the mixture driven by buoyancy under natural convection. The test is carried out with well-controlled boundary conditions, in which, a mixture of helium and vapor with a volume fraction of 1:10 is injected in the compartment filled with air. As the injection begins, the gas mixture is driven by the injection source and the buoyancy of the light gas. The gas is released through the top and bottom openings with the flow velocity of 5 m/s and 7.5 m/s, respectively. When the injection is stopped at 4600s, the density gradient induces the natural convection, air enters the vessel through the bottom opening with a relatively low velocity, and the low-density mixture is discharged through the top opening at the same time. During this period, the velocity of the mixture at the opening decreases due to the reduction of the drive force of natural convection.