An absorption refrigeration cycle using two working pairs was presented

taking LiBr solution with low saturated vapor pressure as the working pair for the low-pressure stage and LiCl solution with higher saturated vapor pressure for the high-pressure stage. The thermodynamic performance of the cycle was investigated and evaluated with variable operation conditions. It shows that the single stage absorption chiller with LiCl solution as the working fluid has a higher COP than LiBr solution when the driven heat temperature is low. The low grade solar energy driving the absorption chiller can be extended to 55—75℃ and the maximal COP can reach up to 0.47 owning to two working fluids. Consequently

the available operation time is increased and the efficiency of solar collector is improved. In particular

the intermediate pressure has a significant influence on the COP of the system

and there is an optimal intermediate pressure making the COP of the system maximum. The theoretical analyses reveal that the optimal intermediate pressure for the system lies from 2.5 kPa to 4.0 kPa.