Performance Analysis on the Absorption Refrigeration Cycle Using R1234ze(E)/Ionic Liquids as Working Pairs

Traditional refrigerant-absorbent pairs, such as H2O/LiBr or NH3/H2O used in the absorption refrigeration system, have some drawbacks, and some of the mixtures including ionic liquids are considered as promising alternative working pairs. The performance of the single-effect absorption refrigeration system using R1234ze(E)/[Bmim][PF6], R1234ze(E)/[Hmim][PF6], or R1234ze(E)/[Omim][PF6] as the working pair was investigated in the present work. Firstly, the NRTL activity coefficient model was used to correlate the experimental vapor-liquid equilibrium data, and the thermodynamic models of the absorption cycles were also established. In addition, the circulation ratio, mass concentration difference between strong and weak solutions, coefficient of performance and exergy coefficient of the cycle were analyzed at different generation temperatures, evaporation temperatures and condensation temperatures. At last, the performances of the refrigeration system based on R1234ze(E) with other ionic liquids (including [Hmim][Tf2N], [Omim][BF4], [Hmim][BF4] and [Emim][BF4]) reported in the literatures are compared with the results of this work. The results show that when the condensation temperature is 30℃, the maximum coefficient of performance and the maximum exergy coefficient of the cycle can be attained at the generation temperatures of 70℃ and 65℃, respectively. And at this condition, the R1234ze(E)/[Omim][PF6] pair has the highest coefficient of performance of 0.21, and the exergy coefficient is 0.089. The R1234ze(E)/[Hmim][Tf2N] pair has the highest performance, but that for R1234ze(E)/[Emim][BF4] is the lowest. This study may provide useful information for the application of new working pairs to the absorption refrigeration systems. © 2019, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.