Fundamental Study of Characteristics of Flash Evaporation in a Steam Accumulator

An experimental study is carried out with a quantity of warm pool water exposed to a sudden pressure drop, to determine the performance characteristics of a steam accumulator. Ranges of experimental variables include : initial liquid temperatures of 40, 60 and 80 °C, liquid levels of 0.30 and 0.60 m, and superheats between 2 and 13K. From the experimental results, it is found that the nonequilibrium phenomenon of pool water is induced mainly by the boiling point elevation due to liquid level and, consequently, the amount of evaporation per unit mass of liquid decreases as the liquid level increases and as the liquid temperature decreases. It is also found that the evaporation efficiency based on the local superheat in liquid phase depends practically on the dimensionless depth of superheated zone, and an empirical equation is deduced for predicting the mass of evaporated liquid.