Vapor Explosions in a Stratified Geometry

Abstract

n experimental investigation of stratified vapor explosions and scaling is conducted by constructing test sections of two different sizes and using two different fluid pairs. The horizontal lengths of the interaction vessels are 20 and 50 cm (geometric scale ratio: 2:5). The two liquid pairs are water and liquid nitrogen, and water and Freon-12, with water being the hot liquid. The interactions are either triggered by an external trigger or allowed to occur spontaneously depending on the liquid pair and initial conditions. The major experimental variables are initial water temperature, liquid layer depths, and magnitude of the external trigger pressure. Interaction pressures, mechanical work release, and depth of intermixing are measured. The water/Freon-12 pair produces more violent interactions than the water/liquid nitrogen. In both cases, the explosion propagation speeds are supersonic, ranging from 40 to 250 m/s. The small depths (≤1 cm) of liquid-liquid mixing during the explosion propagation are observed in both liquid pairs. A simple model for the depth of intermixing is derived, and the result shows reasonable agreement with the experimental observations. The length of the liquid layer interface and the depth of the top liquid appear to be the key geometric parameters in stratified vapor explosions.