Modeling and performance analysis of an absorption chiller with a microchannel membrane-based absorber using LiBr-H2O, LiCl-H2O, and LiNO3-NH3

Abstract

In order to develop compact absorption refrigeration cycles driven by low heat sources, the simulated performance of a microchannel absorber of 5-cm length and 9.5 cm3 in volume provided with a porous membrane is presented for 3 different solution-refrigerant pairs: LiBr-H2O, LiCl-H2O, and LiNO3-NH3. The high absorption rates calculated for the 3 solutions lead to large cooling effect to absorber volume ratios: 625 kW/m3 for the LiNO3-NH3, 552 kW/m3 for the LiBr-H2O, and 318 kW/m3 for the LiCl-H2O solutions given the studied geometry. The performance of a complete absorption system is also analyzed varying the solution concentration, condensation temperature, and desorption temperature. The LiNO3-NH3 and the LiBr-H2O solutions provide the largest cooling effects. The LiNO3-NH3 can work at a lower temperature of the heating source, in comparison with the one needed in a LiBr-H2O system. The lowest cooling effect and coefficient of performance are found for the LiCl-H2O solution, but this mixture allows the use of lower temperature heating sources (below 70°C). These results can be used for the selection of the most suitable solution for a given cooling duty, depending on the available heat source and condensation temperature.