溴化锂水溶液汽液相平衡的分子模拟

Molecular simulation of the vapor-liquid equilibrium of an aqueous solution of lithium bromide

为了研究热泵工质溴化锂水溶液的相平衡性质,采用NPT-Gibbs系综蒙特卡罗方法,进行了LiBr/H2O二元体系热力学相平衡的分子模拟研究.模拟了在80℃、100℃下,以及不同压力下LiBr/H2O的汽液相平衡性质,得出了液相的平衡组成和密度;同时分析了溴化锂溶液的总构型能、范德华作用能、静电作用能随压力、浓度的变化规律;分析了100℃下,阴、阳离子和水的径向分布函数以及第一配位圈中的配位数随压力、浓度的变化规律;最后计算了80℃、100℃下,不同浓度的溴化锂溶液的恒压比热容.所有模拟值与已有研究结果比较,平均相对偏差5.65%～11.31%,表明了力场模型的可靠性.

Phase equilibrium properties of an aqueous solution of lithium bromide were studied as the working fluid of a heat pump.The molecular simulation of LiBr/H2O was carried out by NPT-Gibbs Ensemble Monte Carlo（GEMC）.The simulations were carried out at 80℃ and 100℃ under different pressures,and the corresponding composition and density data were obtained when the liquid phase and vapor phase were in equilibrium.Additionally,the variation of the total configurational energy,Lennard-Jones potential,and electrostatic potential of the liquid phase with different pressures at 80℃ and 100℃ were analyzed.The radial distribution function and coordination number of the first coordination sphere between ions and water were also studied at 100℃ under different concentrations and pressures.Finally,the constant pressure specific heat capacities of an aqueous solution of lithium bromide with various concentrations at 80℃and 100℃ were calculated.The simulation results were compared with referenced data and the relative average deviation is between 5.65% and 11.31%,which demonstrates the reliability of the force field models.