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-Fundamentals: Thermodynamics

1.9 Dew point

The bubble point is the temperature at which a liquid mixture starts to boil while the dew point is the temperature at which the vapor mixture starts to condense.

At defined pressure and composition, the bubble point and the dew point are univocal determined.

B) Dew point calculation

The condensing temperature TDP is the one which fulfils the following system:

S xi = 1;
xi = yi / ki [TBP]

The here below procedure can be followed for the dew point calculation:

(1) estimate a value for the temperature TDP;

(2) calculate the ki [TDP, P, yi];

For this calculation, you need the constant of the
Antoine equation and the total pressure.

(3) verify S yi / ki = 1;

(4) iterate steps (1), (2), (3) until the step (3) is fulfilled