Thermodynamic Properties of Ternary Lithium Bromide Solution Mixed with Ionic Liquid as Working Pairs for Absorption Heat Transformer

Absorption heat pumps are categorized into two main types: absorption heat pumps (AHPs) and absorption heat transformers (AHTs). AHT is defined as a system that upgrades medium-temperature heat to higher temperatures for industrial applications. So far, the majority of research on working pairs has been concentrated in the medium-to-low temperature range of AHPs, this research delves into the thermodynamic evaluation and performance metrics of ternary working pairs designed for high-temperature absorption heat transformers. The integration of ionic liquids (ILs) with conventional H₂O/LiBr mixtures aims to overcome the drawbacks of traditional working pairs, including issues like corrosion and toxicity. The corrosion rates of eight ternary IL working pairs were measured under high-temperature conditions. After a preliminary evaluation of short-term corrosion measurements, four working pairs with lower corrosiveness were selected for further thermodynamic analysis. The results indicate that the ternary working pairs containing [EPy][Br] and [BMIM][I] exhibited lower viscosity, but their specific heat capacities were notably lower compared to the working pair containing [EMIM][Ac]. Furthermore, the ternary working pair containing [EMIM][MeSO₃] showed significantly higher corrosiveness than the other three pairs. Based on this analysis, the ternary working pair formed by adding [EPy][Br] to the conventional LiBr solution demonstrates greater potential for application in high-temperature AHT systems.