Boiling characteristics of dilute polymer solutions and implications for the suppression of vapor explosions

Abstract

Quenching experiments of hot solid spheres in dilute aqueous solutions of polyethylene oxide polymer and surfactant have been conducted for the purpose of investigating the physical mechanisms of the suppression of vapor explosions in this polymer solutions. Two spheres of 22.2 and 9.5 mm-diameter were tested in the polymer solutions of various concentrations and pool temperatures from 30°C to its boiling point. The minimum film boiling temperature in 30°C liquid rapidly decreased from over 700°C for pure water to about 150°C as the polymer concentration was increased up to 300 ppm for a 22.2 mm sphere, and it decreased to 350°C for a 9.5 mm sphere. This trend is observed consistently in the heated pool up to its boiling temperature, while the tests with surfactant solutions do not show an appreciable reduction in the minimum film boiling temperature. The ability of suppression of vapor explosions by dilute polyethylene oxide solutions against an external trigger pressure was tested by dropping molten tin into the polymer solutions at 25°C. It was observed that in 50 ppm solutions more mass fragmented than in pure water, but it produced weaker explosion pressures. The explosion was completely suppressed in 300 ppm solutions with the external trigger. The debris size distributions of fine fragments smaller than 0.7 mm were shown to be almost identical regardless of the polymer concentrations.