ON THE THERMODYNAMIC EFFICIENCY OF ENERGY-CONVERSION DURING THE EXPANSION OF A MIXTURE OF HOT PARTICLES, STEAM AND LIQUID WATER

When an amount of high-temperature molten material is suddenly and fin ely mixed with a body of liquid water, the ensuing mixture expands bec ause of the volumetric generation of steam. At the same time, the expa nding mixture is accelerated away from the surfaces with which it come s in contact. In this paper, we address the fundamental thermodynamic aspects of the energy-conversion process, with emphases on the energy- conversion efficiency and the impact of the intensity of the heat-tran sfer irreversibility on decreasing the efficiency. The expanding mixtu re is modeled as a conglomerate of spherical drops of molten material distributed uniformly throughout a body of water. At the elemental lev el, steam annuli develop around the spherical drops as time increases. At the mixture level, the density decreases while the pressure and ve locity increase. The energy-conversion process is simulated numericall y, and results are reported for the evolution of a mixture layer bound ed on one side by an impermeable plane wall. The energy conversion eff iciency is in the 10(-2)-10(-3) range. The effects of physical paramet ers such as droplet and water-layer sizes are discussed. (C) 1997 Else vier Science Ltd.