Exergy analysis of an ionic-liquid absorption refrigeration system utilizing waste-heat from datacenters

• Absorption refrigeration system was investigated for datacenter thermal management and waste-heat recovery.
• Mixtures of refrigerant/ionic-liquid were studied as the working fluid pair for absorption refrigeration system.
• We carried out comprehensive theoretical first law and second law thermodynamic analysis.
• The essential factors of affecting the refrigerant/IL absorption system performance were identified.
• Water/[emim][BF4] showed the best performance of ECOP.

Ionic-liquid (IL) was introduced as an absorbent of an absorption refrigeration system designed for high power electronics cooling. IL is a salt in liquid-state, which is nonvolatile, thermally-stable, nonflammable, and environmentally-benign. It provides an alternative to the normally toxic working fluids, such as ammonia, also eliminates crystallization and metal-compatibility issues of the water/LiBr system. The performance of IL absorption refrigeration system was theoretically examined using exergy analysis. Various combinations of refrigerant and imidazolium-based ILs were chosen as working fluid pairs. The thermodynamic properties of ILs were evaluated using the correlations based on group contribution methods. A non-random two-liquid (NRTL) model was built and used to predict the solubility of the mixtures. Both the coefficient of performance (COP) and the exergetic coefficient of performance (ECOP) were evaluated. The effects of operating conditions on ECOP were explored. Also, the exergy destruction of each component was evaluated and discussed as a means to identify the critical component(s) of the system that would require optimization.