Effect of using an ionic liquid as additive in water/LiBr mixture in a horizontal falling film absorber

Abstract

Absorption Heat Pumps (AHPs) are attractive technology for space cooling from low grade energy resources. This technology is of special interest when water/LiBr is used as a working mixture, as water is a natural, non-toxic and cost-effective refrigerant without any contribution to global warming. Nonetheless, water/LiBr AHPs do come with certain inbuilt issues as LiBr tends to crystallize at higher concentrations, that hinder the technology from functioning as an air-cooled system and in a reversible mode for space heating. Addition of Ionic Liquids (ILs) as additive is therefore important which improves the solubility of LiBr in water/LiBr solution. The addition of IL as additive is 1,3-Dimethyl-1H-imidazolium chloride [DMIM][Cl] which is 6% of absorbent (LiBr+IL) by mass. This paper aims to compare the heat and mass transfer involved in water absorption process of water/LiBr and water/(LiBr+[DMIM][Cl]) mixtures in a horizontal tubes falling film absorber.