I would, for simplicity, select the DECHEMA model (
http://cocosimulator.org/index_help.php ... gacity.htm):
fug_water_liquid = x_water * gamma_water * Psat_water(T)
fug_water_vap = y_water * P = P
At equilibrium, liquid and vapor fugacities are equal, also for water:
fug_water_liquid = fug_water_vap
or
x_water * gamma_water * Psat_water(T) = P
Back out the PSat relation for water (from temperature correlations in the TEA setup):
Psat_water = exp(A + B/T + C*ln(T) + D*T^E)
with
A = 98.5149993896
B = -8530.70019531
C = -10.984000206
D = 6.36630011286e-006
E = 2
results an expression in just x_water, T and P:
x_water * gamma_water * exp(A + B/T + C*ln(T) + D*T^E) = P
Now, at the dew points, you know all of these from the bottom streams.
This gives you several expressions for gamma_water.
Now, pick a model for activity coefficient, e.g. Margules.
ln(gamma_water) = [A_water_sucrose + 2 * (A_sucrose_water - A_water_sucrose) * x_water] * (1 - x_water)^2
(see
http://en.wikipedia.org/wiki/Margules_activity_model, or
http://cocosimulator.org/index_help.php ... tivity.htm)
You really don't care about the activity coefficient of sucrose (it will not appear in the vapor phase with the very high vapor pressure you selected), so each dew point condition gives you an equation in which merely A_sucrose_water and A_water_sucrose are unknown. Pick values that fit all your dew points best.