Flash evaporation is used intensively in distillation and steam generation processes, including water desalination, thermal storage steam accumulators/ generators, and ocean-thermal energy conversion. It is also of great importance in a wide variety of other applications, ranging from loss-of-coolant accidents in nuclear reactors to thin film coating under high vacuum. The flash evaporation phenomenon is typically very rapid and associated with violent disruption of the evaporating liquid, and is hence somewhat difficult to both model and measure. 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 degree C to 80 degree C, and superheats of 2 degree C to 7 degree 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 (Ti) 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 delta2.(NETD).delta.Ti2 changes sign from positive at smaller depths to negative at larger depth.
Some critical transitions in pool flash evaporation
Einige kritische Übergänge in der Pool-Entspannungsverdampfung
International Journal of Heat and Mass Transfer ; 40 , 10 ; 2363-2372
1997
10 Seiten, 10 Bilder, 15 Quellen
Aufsatz (Zeitschrift)
Englisch
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