Vapor Liquid Equilibrium
At low to moderate P
 Raoult’s Law for Adults (RLA)
 Solve for 4 cases
 ______________(know T and xi)
 ______________ (know T and yi)
 _______________(know P and xi)
 _______________(know P and yi)
All Algorithms
 List out equations (unknowns=eqs)
 List out what you know and what you
don’t know
 Keep track of what you know, what
you don’t know, and WHAT YOU
HAVE A VALUE FOR
 Iterate until you converge
Bubble P Algorithm
 Assume binary initially
 What are my equations, what do
I know, and what do I don’t
know?
Bubble P algorithm
 3 equations, 3 unknowns
Dew P Algorithm
 Assume binary initially
 What are my equations, what do
I know, and what do I don’t
know?
Dew P algorithm
 3 equations, 3 unknowns, BUT
can’t solve analytically
 Must be iterative
 Let’s GUESS for activity
coefficient
Dew P algorithm
 Look at list, what do I know, what
do I not know, and what do I
have values for?
Dew P algorithm
 Similar to Bubble P
 3 ?’s (know/unknown/have?)
Bubble T Algorithm
 Assume binary initially
 What are my equations
 My 3 Variable equations
Bubble T algorithm
 3 equations, 3 unknowns, BUT
can’t solve analytically
 Must be iterative
 Same Reasoning as for Dew P
 Re-ask my 3 ?’s
 Let’s GUESS for T
 Antoine’s Eq
Bi
=
- Ci
Ai - ln P
Ti
sat
T
guess
= å xiTi
sat
Bubble T Algorithm
 Ask my 3 ?’s again
 __________________
 Use algebra after REASKING 3?’s
 SHOULD be 1, but is it?
 Use as a weighting factor
Bubble T Algorithm
 Weighting Factor
 Adjust a variable? (unknown, but have
value for)
 Want it to get to get an updated thing of
the FIRST thing I guessed (??)
Bubble T algorithm
 I have T, what is NEXT thing I got a
value for?
 _____________________
 What I am still missing though?
 What is the last thing to be “guessed”
 __________
Bubble T algorithm
 Similar to Dew P
Dew T Algorithm
 Assume binary initially
 What are my equations
 My 3 Variable equations
Bubble T algorithm
 3 equations, 3 unknowns, BUT
can’t solve analytically
 Re-ask my 3 ?’s
 Let’s GUESS for T
 Antoine’s Eq
Bi
=
- Ci
Ai - ln P
Ti
sat
T
guess
= å yiTi
sat
Dew T Algorithm
 Ask my 3 ?’s again
 Similar reasoning as Bubble T
 Use as a weighting factor
Dew T Algorithm
 Weighting Factor
 Now have T, what can I update
Dew T algorithm
 I have values for all, what did I
guess FIRST
 ________
 Start the cycle
Bubble T algorithm
 Similar to Dew P
Summary
 Decide what you know, what you
don’t know, and what you have
values for
 In terms of updating, update what you
have values for in order
 Equations
 RLA
 Summation of mole fraction = 1.0