Some critical transitions in pool flash evaporation

To improve the fundamental understanding of the physics of the flash evaporation process, pool flash evaporation experiments were conducted in a 152 mm diameter chamber with initial water temperatures of 40-80 degrees C, and superheats of 2-7 degrees C. Several critical transition points were identified or discovered: (1) a critical time at which the rate of ebullition and evaporation diminishes abruptly, (2) an initial water temperature (T-i) at which the non-equilibrium temperature difference attains a minimum, (3) a critical initial water temperature at which the expected observed trend of decreasing non-equilibrium temperature difference (NETD) with decreasing depth reverses itself and (4) a critical initial pool depth at which partial derivative(2)(NETD)partial derivative T-i(2) changes sign from positive at smaller depths to negative at larger depths. (C) 1997 Elsevier Science Ltd. All rights reserved.