Efficient and robust stability analysis in the internal energy, volume, and moles (UVN) space

Rapid multi‐component phase‐split calculations using volume functions and reduction methods

“…Step 2, molar compositions of the liquid x i and vapor y i for (i = 1…n) are computed using Equation (15). Then m reduced parameters q k and mixture co-volume parameter b are obtained using Equations ( 19) and ( 4) for both phases.…”

“…However, utilizing mole numbers as the independent variables in the algorithm may still result in convergence problems for states that lie close to the phase boundaries. 14,15 In addition, the computational expense of the initial stability check and the calculation of initial values for the UV-flash can be significant, especially when there are many components in the mixture.…”

“…Smejkal and Mikyška 13 alleviated these convergence problems via a systematic approach for executing the stability analysis and providing better initial conditions for the flash calculations. However, utilizing mole numbers as the independent variables in the algorithm may still result in convergence problems for states that lie close to the phase boundaries 14,15 . In addition, the computational expense of the initial stability check and the calculation of initial values for the UV‐flash can be significant, especially when there are many components in the mixture.…”

Robustness and efficiency of phase stability testing at VTN and UVN conditions

“…These kinds of phase equilibrium calculations have received an increasing interest in the last decade. Even though a number of papers are treating the phase splitting problem at UVN conditions [5][6][7][8][9][10][11][12], UVN stability testing has received relatively little attention [6,8,9,13], despite its high importance in initialization of UVN flash calculations.…”

“…Smejkal and Mikyška [8,9] provided a comprehensive analysis of UVN stability testing; they used modified Newton iterations to maximize the TPD function. Bi et al [13] used a combined SSI-Newton method in VTN stability to find the stationary points of the TPD function in UVN stability.…”