chemical engineering thermodynamics ii dr. perla b. balbuena: jeb 240 web site: 20
DESCRIPTION
TEAMS Please group in teams of 4-5 students each Designate a team coordinator Team coordinator: Please send me an stating the names of all the students in your team (including yourself) no later than next Monday First HW is due January 26 thTRANSCRIPT
Chemical Engineering Thermodynamics II
• Dr. Perla B. Balbuena: JEB 240 [email protected]• Web site:
https://secure.che.tamu.edu/classes/balbuena/CHEN%20354-Thermo%20II-Spring%2012/CHEN%20354-Thermo%20II-Spring%2012.htmor:
• http://research.che.tamu.edu/groups/balbuena/courses.htm
(use VPN from home)CHEN 354-Spring 12
TA: Mian Huang; e-mail:[email protected]
TA office hours • Thursdays 1:30 to 2:30 pm; Rm 501
• Or by appointment, please e-mail to Mian Huang:[email protected]
TEAMS • Please group in teams of 4-5 students
each• Designate a team coordinator • Team coordinator: Please send me an
e-mail stating the names of all the students in your team (including yourself) no later than next Monday
• First HW is due January 26th
Introduction to phase equilibrium
Chapter 10 (but also revision from Chapter 6)
Equilibrium• Absence of change• Absence of a driving force for change• Example of driving forces
– Imbalance of mechanical forces => work (energy transfer)
– Temperature differences => heat transfer
– Differences in chemical potential => mass transfer
Energies• Internal energy, U
• Enthalpy H = U + PV
• Gibbs free energy G = H – TS
• Helmholtz free energy A = U - TS
Phase Diagram Pure Component
a
d
c
b
e
What happens from (a) to (f) as volume is compressed at constant T.
f
P-T for pure component
P-V diagrams pure component
Equilibrium condition for coexistence of two phases
(pure component)• Review Section 6.4
• At a phase transition, molar or specific values of extensive thermodynamic properties change abruptly.
• The exception is the molar Gibbs free energy, G, that for a pure species does not change at a phase transition
Equilibrium condition for coexistence of two phases
(pure component, closed system)
d(nG) = (nV) dP –(nS) dTPure liquid in equilibrium with its vapor, if a differential amount of
liquid evaporates at constant T and P, then
d(nG) = 0n = constant => ndG =0 => dG =0
Gl = GvEquality of the molar or specific Gibbs free energies (chemical
potentials) of each phase
Chemical potential in a mixture:
• Single-phase, open system:
i
inTPinPnT
dnnnGdT
TnGdP
PnGnGd
j,,,,
)()()()(
i :Chemical potential of component i in the mixture
Phase equilibrium: 2-phases and n components
• Two phases, a and b and n components:
Equilibrium conditions:
ia = i
b (for i = 1, 2, 3,….n)
Ta = Tb
Pa = Pb
A liquid at temperature T
The more energetic particles escape
A liquid at temperature T in a closed container
Vapor pressure
Fugacity of 1 = f1 Fugacity of 2 = f2
222̂ fxf id
111̂ fxf id
For a pure component =
iiii fRTTG ln)(
For a pure component, fugacity is a function of T and P
For a mixture of n components
i = i
for all i =1, 2, 3, …n
in a mixture:
iii fRTT ˆln)(
Fugacity is a function of composition,T and P
Lets recall Raoult’s law for a binary
lv
lv
ff
ff
22
11
ˆˆ
ˆˆ
We need models for the fugacity in the vapor phase and in the liquid phase
Raoult’s law
Raoult’s law• Model the vapor
phase as a mixture of ideal gases:
• Model the liquid phase as an ideal solution
ivi Pyf ˆ
isati
li xPf ˆ
VLE according to Raoult’s law:
222
111
xPPy
xPPysat
sat
Homework # 1
download from web site
Due Wednesday, January 25th, at the beginning of the class