溴化锂及离子液体水溶液密度、黏度和表面张力测定与计算

常压条件下，实验测定了不同温度（283.15~343.15 K）下吸收制冷/热泵工质对——溴化锂（LiBr）、1-乙基-3-甲基咪唑醋酸盐（EMIM]OAC]）和1-丁基-3-甲基咪唑硫氰酸盐（BMIM]SCN]）水溶液的密度、黏度和表面张力，借助线性方程和Vogel-Tammann-Fulcher（VTF）模型，分别成功关联了密度和黏度实验值。研究结果表明：在相同条件下，溴化锂水溶液的密度大于离子液体水溶液的密度，而前者的黏度小于后者；对表面张力，随着溴化锂含量增加，其水溶液的表面张力值增加，而少量离子液体可使水的表面张力快速下降。根据实验黏度和表面张力分别获得了能量势垒和表面熵/焓，表明各水溶液中分子或离子迁移难易程度遵循EMIM]OAC] > BMIM]SCN] > LiBr，表面有序性遵循BMIM]SCN] > EMIM]OAC] > LiBr。研究结果可为吸收制冷/热泵工质对及低温余热回收系统的设计和计算提供可靠的数据支撑。

Measurement and calculations of density,viscosity and surface tension for lithium bromide and ionic liquid aqueous solutions

The density, viscosity and surface tension of the working pairs of lithium bromide (LiBr), 1-ethyl-3-methylimidazolium acetate (EMIM]OAC]) and 1-butyl-3-methylimidazoliumthiocyanate (BMIM]SCN]) aqueous solution for absorption refrigeration and heat pump were determined within the temperature from 283.15 K to 343.15 K and at ambient pressure in this work. The experimental density and viscosity were satisfactorily described with the linear model and the Vogel-Tammann-Fulcher type equation, respectively. The results show that the density of LiBr aqueous solution is higher than that of ionic liquid solution, but the viscosity of the former is lower than that of the latter. For the surface tensions, the values increase with the increasing of lithium bromide concentration in LiBr aqueous solution, while a small amount of ionic liquids can make the surface tension of water decrease rapidly under the same conditions. According to the experimental viscosity and surface tension, the energy barrier and surface entropy/enthalpy were obtained, indicating that the mobility of molecular or ion migration in each aqueous solution follows EMIM]OAC] > BMIM] SCN] > LiBr and the surface orderings follow BMIM]SCN]>EMIM]OAC] > LiBr. The results of this work can provide reliable data support for the design and calculation of the absorption refrigeration or heat pump working pairs and low temperature waste heat recovery systems.