Thermodynamic properties assessment of working mixtures {water + alkylphosphonate based ionic liquids} as innovative alternatives working pairs for absorption heat transformers

• Published in: Applied thermal engineering 2020-11, Vol.181, p.115943, Article 115943
• Main Authors: Abumandour, El-Shaimaa, Mutelet, Fabrice, Alonso, Dominique
• Format: Article
• Language: English
• Subjects: Absorption; Absorption heat transformers; Binary systems; Coefficient of performance; Engineering Sciences; Enthalpy; Heat exchangers; Heat sinks; Heat transfer; Heat transformers; Ionic liquids; Liquid-vapor equilibrium; Lithium; Operating temperature; Performance evaluation; Phosphonates; Temperature; Thermodynamic properties; Thermodynamics; Transformers
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2020.115943

•Thermodynamic properties of binary systems {H2O + alkylphosphonate based ILs} are measured.•The performance of absorption heat transformers using mixtures containing alkylphosphonate based ILs and H2O is estimated.•The performance of {H2O + alkylphosphonate based ILs} is close to that of working pair {H2O + LiBr}. Based on a continuously developing portfolio of ionic liquids, the aim of this work is to evaluate the performance of new working pairs composed of {water + alkylphosphonate based IL} as alternative working pairs for absorption heat transformers. Therefore, thorough thermodynamic measurements were conducted for three alkyl phosphonate based ionic liquids and their aqueous binary systems. Experimental measurements of vapour-liquid equilibrium, heat capacity, density and excess enthalpy were measured and successfully represented using NRTL model and adequate equations. Thermal performances of single stage absorption heat transformer were numerically simulated. The influence of the temperature sources and sinks was studied. The best coefficient of performance was obtained with mixtures of water and 1-ethyl-3-methylimidazolium methylphosphonate. The typical coefficient of performance values for this mixture is found to be between 0.40 and 0.45 depending on the temperature conditions. This value is 10% lower than that observed with the classically used {water + lithium bromide} mixture. Nevertheless, {water + ionic liquid} mixture has a wider operating temperature range than conventional working pairs. The higher circulation ratio observed with the proposed mixtures may increase pumping cost.