Experimental study on the effect of an ionic liquid as anti-crystallization additive in a bi-adiabatic H2O-LiBr absorption chiller prototype

• Published in: Applied thermal engineering 2025-01, Vol.259, p.124756, Article 124756
• Main Authors: Tariq, Hussain A., Altamirano, Amín, Collignon, Romain, Stutz, Benoit, Coronas, Alberto
• Format: Article
• Language: English
• Subjects: [DMIM][Cl]; Absorption chiller; Additive; H2O-LiBr; Heat and mass transfer; Ionic liquid; Mechanics; Physics; Thermics
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2024.124756

•Characterization of the impact of the [DMIM][Cl] ionic liquid additive on the physical properties of LiBr-H2O working pair.•Characterization of the impact of the [DMIM][Cl] ionic liquid additive on the performance of LiBr-H2O absorption machine.•Demonstration of an innovative absorption machine including 3D printed adiabatic absorber and desorber.•The use of [DMIM][Cl] as an additive in H2O-LiBr for absorption chillers extend the temperature range of LiBr absorption machines.•Reduced performance of plate heat exchangers as low-pressure evaporators. Absorption chillers are attractive because they use natural refrigerants and can be powered by low-grade heat sources. Among the commercially available working fluids, the most common one, H2O-LiBr, has a critical drawback associated with the crystallization of the solution at low temperatures and high absorbent concentrations. This limitation restricts the operating range of these systems, especially when they are air-cooled or used as heat pumps. Additives can be used in H2O-LiBr to reduce the crystallization temperature by improving the solubility of LiBr in the solution. However, they often present disadvantages such as the requirement of a rectifier, and a negative impact on heat and mass transfer. Ionic Liquids (ILs) used as additives represent an alternative to overcome these drawbacks. In the present study, 6 % of [DMIM][Cl] by mass in absorbent (LiBr + [DMIM][Cl]) is added as an anti-crystallization additive to study its effect on the experimental behavior and crystallization limit of a H2O-LiBr single-effect bi-adiabatic absorption chiller prototype. Results of H2O-LiBr and H2O–(LiBr + [DMIM][Cl]) were compared for the individual heat transfer elements and the global system COP. The results show a decrease in the crystallization temperature using H2O–(LiBr + [DMIM][Cl]), which extended the operating range of the prototype. A decrease of 15 °C in crystallization temperature was found for H2O–(LiBr + [DMIM][Cl]) compared to H2O-LiBr at an absorbent mass of 65 %. Crystallization impeded the operation for H2O-LiBr at the highest driving temperature (100 °C) and lowest cold source inlet temperature (9 °C), whereas no crystallization was observed at same operating conditions for the (LiBr + [DMIM][Cl]) solution. Under the tested conditions, the addition of the IL as additive increased the chiller operating range without the requirement of a rectifier and with a negligible impact on the cooling capacity and