Performance evaluation of membrane-based absorbers employing H₂O/(LiBr + LiI + LiNO₃ + LiCl) and H₂O/(LiNO₃ + KNO₃ + NaNO₃) as working pairs in absorption cooling systems

In recent years, rigorous research has been carried out on the use of membrane contactors to design compact absorbers for absorption cooling systems and to extend their use in small scale applications. Moreover, the use of new working fluid mixtures has been suggested for the absorption cooling systems to cope with the limitations and problems associated with the conventional working fluid mixtures. In this study, water/(LiBr + LiI + LiNO₃ + LiCl) with mass compositions in salts of 60.16%, 9.55%, 18.54% and 11.75%, respectively, and water/(LiNO₃ + KNO₃ + NaNO₃) with mass compositions in salts of 53%, 28% and 19%, respectively, were investigated for air-cooled and multi-stage high temperature absorption cooling systems, respectively. Results show that a 25% increase in the absorption rate can be achieved by using water/(LiBr + Li + LiNO₃ + LiCl) when compared to water/LiBr at air-cooling thermal conditions. Furthermore, an absorption rate as high as 0.00523 kg/m² s is achieved when the water/(LiNO₃ + KNO₃ + NaNO₃) working fluid mixture is used in the membrane-based absorber of the third stage of a triple effect absorption cooling cycle. In addition, the pressure drop percentage in the case of water/(LiNO₃ + KNO₃ + NaNO₃) working fluid mixture is significantly lower than the water/LiBr and water/(LiBr + LiI + LiNO₃ + LiCl) working fluid mixtures because of the higher operating pressure.