Method for predicting surface tension of (h2+n2)/h2o system based on linear gradient theory (lgt) and perkins-rammler (pr) state equation

A method for predicting surface tension of a (H2+N2)/H2O system based on a linear gradient theory (LGT) and a Perkins-Rammler (PR) state equation, comprising following steps:

• determining an energy parameter and a co-volume parameter of a pure gas based on the PR state equation, and determining a material parameter and a co-volume parameter of a mixed gas according to a Waals one-fluid mixing rule and a combination rule;
• determining a Helmholtz free energy density and an equilibrium density of the pure gas by using a Wertheim molecular association theory, and determining a Helmholtz free energy fmixture(ρ) and an equilibrium density ρb,mixture of a (H2+N2) mixed gas with different components according to a density mixing rule;
• determining an influence parameter κ of the pure gas by using a gradient theory, and determining an influence parameter of the mixed gas based on the influence parameter (κH2, κN2) of the pure gas and an interaction coefficient lmixture;
• simplifying a gradient theory model to obtain a simplified gradient theory model, namely an LGT model;
• and
• obtaining the surface tension of the (H2+N2)/H2O system at different temperatures by combining the LGT model and the PR state equation.