Comprehensive performance analysis and optimization of 1,3-dimethylimidazolylium dimethylphosphate-water binary mixture for a single effect absorption refrigeration system

Abstract

The energy and exergy analyses of the absorption refrigeration system (ARS) using H2O-[mmim][DMP] mixture were investigated for a wide range of temperature. The equilibrium Dühring (P-T-XIL) and enthalpy (h-T-XIL) of mixture were assessed using the excess Gibbs free non-random two liquid (NRTL) model for a temperature range of 20°C to 140°C and XIL from 0.1 to 0.9. The performance validation of the ARS cycle showed a better coefficient of performance (COP) of 0.834 for H2O-[mmim][DMP] in comparison to NH3-H2O, H2O-LiBr, H2O-[emim][DMP], and H2O-[emim][BF4]. Further, ARS performances with various operating temperatures of the absorber (Ta), condenser (Tc), generator (Tg), and evaporator (Te) were simulated and optimized for a maximum COP and exergetic COP (ECOP). The effects of Tg from 50°C to 150°C and Ta and Tc from 30°C to 50°C on COP and ECOP, the Xa, Xg, and circulation ratio (CR) of the ARS were evaluated and optimized for Te from 5°C to 15°C. The optimization revealed that Tg needed to achieve a maximum COP which was more than that for a maximum ECOP. Therefore, this investigation provides criteria to select low grade heat source temperature. Most of the series flow of the cases of cooling water from the condenser to the absorber was found to be better than the absorber to the condenser.