Model evaluation of lithium bromide aqueous solution and characteristics of water transport behaviors in liquid–vapor systems by molecular dynamics

Abstract

Understanding heat and mass transfer between LiBr aqueous solution and vapor is a crucial issue in absorption refrigeration and air dehumidification for the purpose of intensifying transfer and conversion. This is difficult to be realized by macro experiments due to failing to catch detailed information of water molecules. Molecular dynamics has been resorted to for exploring mechanisms of chemical processes but the used force field dominates the simulation accuracy. In order to discover suitable force fields to describe interactions in LiBr solution, three recent models developed based on infinite dilution were evaluated in terms of static and transport properties. Results show that all models could predict the density with high accuracy. The model of Koneshan et al. achieves most properties with satisfactory accuracy and is the best one to simulate the surface tension, which indicates good interfacial performance. Further, by selecting the model of Koneshan et al., the energy and mass transport phenomenon through liquid–vapor interface was simulated and analyzed. Four behaviors of water molecules including absorption, release, replacement and reflection were observed near the interface of LiBr solution. It is found that the replacement behavior only occurs under high liquid temperature conditions and the reflection behavior is characterized by a steep energy ravine. This research provides data reference for the force field selection, setting a solid foundation for studying heat and mass transfer between LiBr solution and vapor by molecular dynamics. This research could also disclose the molecular behaviors between aqueous solution and air.