Constrain both Zs to be > 0.04 AND constrain BOTH f'(Z) functions to be > 0 (to make sure the two roots you find are the sat vap and sat liq roots and not the meaningless one). The easiest way to get Solver to go where you want it is to add FOUR constraints. This is something like the %RMS error for the 5 eqns. I minimized SQRT of the sum of these 5 error terms (divided by 5.
Right ? I used %error^2 for each equilibrium eqn and f(Z)^2 for the SRK eqns. You should also have 5 unks: Zvap, Zliq, P, x1 and x2. any suggestions." I replied: OK, you have 5 eqns: 3 of the them are yliq The remaining 2 eqns are SRK eqns: one for liquid and one for vapor. Date, 11 December, Source, Chemical Engineering Symposium. English: K-Values for systems of light hydrocarbons, high temperature range. I set a constraint for solver that Z is greater than B, but it won't listen. This Demonstration applies a DePriester chart, a set of nomograms, to find the vapor-liquid equilibrium ratio (the gas phase mole fraction divided by the liquid. I get num! I think this is because Zliq is below Bliq and the same for vapor. A student emailed me the following question: "I have all my 5 equations set up and am trying to simultaneously solve for the unknowns.