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 9.5cm(3) 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: 625kW/m(3) for the LiNO3-NH3, 552kW/m(3) for the LiBr-H2O, and 318kW/m(3) 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 degrees 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.