When the superheated steam expands in the nozzle, the condensation will occur in the nozzle. Since the steam has more velocity, the condensation will not take place at the expected rate. So, the equilibrium between the liquid and vapor phase is delayed and the steam continues to expand in a dry state.
The Steam in such set of condition is said to be supersaturated or metastable flow.
EFFECTS OF SUPER SATURATION :
The following effects in a nozzle on steam in which supersaturation occur may be summarized as follows :
1. The dryness fraction of the steam is increased.
2. Entropy and specific volume of the steam are increased.
3. Exit Velocity of the steam is reduced.
4. Mass of steam discharged is increased.
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