Multiphase dynamic flash simulations using entropy maximization and application to compressible flow with phase change

Abstract

A isochoric‐isoenergetic flash solver using a direct entropy maximization principle for phase splitting and Gibbs free energy minimization for phase stability is developed. The solver searches for the global stable state in a rigorous and thermodynamically consistent way. The solver is demonstrated to be robust and efficient to handle multiphase flash, even in the vicinity of phase boundaries. Dynamic flash computations and gas dynamics simulations of shock waves are considered for pure ethylene and for binary ethylene‐nitrogen mixtures. The simulations show significantly different shock wave characteristics when phase separation is considered due to intensive energy exchange, compared to the frozen flow limiting single‐phase solution. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3013–3024, 2014

An investigation of thermodynamic states during high-pressure fuel injection using equilibrium thermodynamics

“…However, the equilibrium state must have the minimum Gibbs free energy, and a single-phase solution may not be able to satisfy this requirement. Thus, extra phases may need to be introduced to lower the Gibbs free energy [24][25][26][27]. Due to the small sizes of drops in high pressure fuel injection, spray models are generally subgrid-scale formulations, which assume that single, isolated drop correlations can be used to model vaporization and condensation processes.…”

Simulation of supercritical fuel injection with condensation

“…The phase equilibrium solver solves the set of nonlinear equations as described by Qiu et al [52]. A Newton-type second-order method [53] was applied to find the maximum entropy state.…”

An algorithm for gradient-based dynamic optimization of UV flash processes

“…Systems modeled by mass and energy balances and subject to vapor-liquid equilibrium constraints occur in a number of important process engineering applications, e.g. distillation (Biegler, 2010;Bisgaard et al, 2015Bisgaard et al, , 2017Diehl et al, 2002;Luyben, 1992;Stichlmair and Fair, 1998), cryogenic distillation (Laiglecia et al, 2012), and two-phase flow in pipelines (Hammer and Morin, 2014;Qiu et al, 2014). Vapor-liquid equilibrium constrained mass and energy conservation models also occur for a number of subsurface flow processes related to CO 2 sequestration (Stauffer et al, 2009), magmatic hydrothermal flow (Ingebritsen et al, 2010), and production of oil from an oil reservoir (Li and Johns, 2006;Lucia et al, 2012;Zaydullin et al, 2014).…”

“…Vapor-liquid equilibrium constrained mass and energy conservation models also occur for a number of subsurface flow processes related to CO 2 sequestration (Stauffer et al, 2009), magmatic hydrothermal flow (Ingebritsen et al, 2010), and production of oil from an oil reservoir (Li and Johns, 2006;Lucia et al, 2012;Zaydullin et al, 2014). The UV flash is a single stage vapor-liquid equilibrium process and is thus a key component in rigorous modeling of fluid vessels and flash drums (Arendsen and Versteeg, 2009;Castier, 2010;Lima et al, 2008), distillation columns (Flatby et al, 1994), two-phase computational fluid dynamical problems (Qiu et al, 2014), and thermal and compositional oil reservoir flow (Zaydullin et al, 2014). While advanced algorithms for robust simulation of the UV flash problem exist (Castier, 2009;Saha and Carroll, 1997), no algorithm for dynamic optimization of UV flash processes seems to exist in the open literature.…”