Comparative study of the cascade absorption heat pump running optimal ternary ionic liquid working pair

Abstract

Novel working pairs are one of the significant measures to enhance the performance of the absorption heat pump. Ternary ionic liquid working pairs (Refrigerant-Salt-Ionic liquid) can alleviate the economic constraint of ionic liquids, but the influence of additional salt-absorbent on the performance of binary ionic liquid working pairs (Refrigerant-Ionic liquid) has not been evaluated. Furthermore, the number of candidates for ternary ionic liquid working fluids is still limited. To fill the above research gaps and advanced absorption technology, a novel ternary ionic liquid working pair is proposed in this work first, and its thermal properties are measured experimentally. Then taking the compression-absorption cascade heat pump as the subject, the differences in cooling performance between various ternary ionic liquid working pairs and binary reference fluids are simulated. The results show that the addition of salt-absorbent does not affect the applicable source temperature range of original ionic liquid working fluids, but it helps to improve the system efficiency and cooling capacity. In particular, the ternary ionic liquid working pair proposed in this work deserves priority recommendation, as it can achieve up to 12.59% higher maximum second law efficiency and 1.95% ∼ 87.87% higher cooling output than other candidates, as well as make cascade heat pump earlier freed from the assistance of compression sub-loop.