Vapor Pressure, Density, Viscosity, Specific Heat Capacity, Dissolution Enthalpy, and Specific Enthalpy of the LiCl–[BMIM]Cl/H ₂ O Working Pair

Imidazolium-based ionic liquids have been reported to enhance the performance of conventional absorption working pairs; however, the effect of 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) on the LiCl/H2O system remains unclear. In this study, a novel working pair, LiCl–[BMIM]Cl/H2O, was proposed, and the optimal mass ratio between LiCl and [BMIM]Cl was systematically investigated. Based on the optimal mass ratio, the vapor pressure, density, viscosity, specific heat capacity, enthalpy of dissolution, and specific enthalpy were measured and calculated over a temperature range of 303.15–373.15 K and a concentration range of 40–60%. Considering both crystallization temperature and application cost, the optimal LiCl-to-[BMIM]Cl mass ratio was determined to be 1:1. The measured data show good agreement with fitted data using the least-squares fitting method. The results of this study provide essential thermophysical property data for evaluating the feasibility of LiCl–[BMIM]Cl/H2O as a working pair in absorption heat pump systems.