Performance analysis of a double-effect absorption refrigeration cycle using a low-temperature ethanol solution as the working pair

In this paper, a double-effect absorption refrigeration system using a low-temperature working pair, lithium bromide (LiBr)+1-butyl-3-methylimidazolium bromide ([BMIM]Br)/ethanol (C2H5OH), was proposed to reduce the driving heat source temperature and enlarge the operation range to subzero temperatures. Based on the measured thermal properties, the thermodynamic performance of the double-effect absorption refrigeration cycle under different working conditions was calculated by Matlab and compared with that using LiBr/H2O working pair. Results showed that the generation temperature of the refrigeration system using LiBr-[BMIM]Br/C2H5OH was reduced by about 30 K in comparison to LiBr/H2O under the same operating condition. The temperature in the absorber with LiBr-[BMIM]Br/C2H5OH was 40 K higher than its crystallization temperature, whereas LiBr/H2O was only less than 20 K. Moreover, the system using LiBr-[BMIM]Br/C2H5OH was able to successfully work under 273.15 K without crystallization. At a typical operating condition, the COP of the double-effect absorption refrigeration cycle with LiBr-[BMIM]Br/C2H5OH reached 1.47, which was 0.10 higher than that using LiBr/H2O. As a low-temperature working pair, LiBr-[BMIM]Br/C2H5OH showed a great potential in utilizing solar energy and the low-temperature waste heat under severe operating conditions. Furthermore, compared with LiBr/H2O, the refrigeration system had a better economic performance with LiBr-[BMIM]Br/C2H5OH working pair.