4 replies to this topic

[asade abiodun]

Hi All,

Is there a relationship between the bubble point of a fluid and its boiling point? what role do pressure play?

This is a thought that is running through my brain......
Thanks for your anticipated responses.

[sheiko]

Hi,
I use boiling point temperature for a pure component and bubble point temperature for a liquid mixture.

Edited by sheiko, 27 November 2012 - 06:58 AM.

[Art Montemayor]

Asade:

Sheiko is correct in explaining how the bubble point is employed.

The nature of a liquid mixture requires an identification of the state of evaporation (or when the liquid is converted into a vapor) because of the fact of what happens subsequent to that event: the bubble point (or “boiling point”) changes immediately due to the composition change in the remaining liquid. This is that part of Unit Operations called “differential distillation”. If left to continue and takes its course all the way to total exhaustion of the liquid, the operation becomes evaporation.

For a pure liquid substance, the boiling point is equal to the bubble point (which is constant, in this specific case).

[asade abiodun]

Thanks Art and Sheiko for the insight.

[markymaark]

Asade,

The bubble point is the same as the boiling point for a pure liquid.

But for a mixture, the bubble point occurs when enough energy is inputed for the mixture to first change phase (evaporate). However, the vapor that changed phase has a different composition than the liquid; thus the liquid mixture changes its composition which therefore changes the amount of energy to cause the current mixture to change phase. Each combination of components varies with how the bubble point changes. VLE (Vapor-Liquid Equilibrium) charts show this phenomena.

Commonly you will see the two words being used interchangably.

Mark