Comparisons of different ionic liquids combined with trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) as absorption working fluids

To overcome the shortcomings of conventional absorption working fluids, the novel trans-1,3,3,3-tetrafluoropropene (R1234ze(E)) and ionic liquid (IL) are studied. The R1234ze(E)/IL properties and different absorption cycles are modeled with verified accuracy. The energy and exergy performance are comparatively investigated for four different ILs, 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]), 1-hexyl-3-methylimidazolium tetrafluoroborate([hmim][BF4]), 1-octyl-3-methylimidazolium tetrafluoroborate([omim][BF4]) and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([hmim][Tf2N]). Under an evaporation temperature of 5 °C, the minimum generation temperature is 44 °C, and the maximum coefficient of performance (COP) is respectively 0.264, 0.390, 0.398 and 0.431 for different ILs. Under a generation temperature of 90 °C, the minimum evaporation temperature is −22 °C, with maximum COP of 0.438, 0.556, 0.580 and 0.606. [emim][BF4] always has the lowest COP and exergy COP, while [hmim][Tf2N] has the highest values under most conditions. The main objectives are contributing novel potential working pairs, improving the efficiency of R1234ze(E)/ILs, as well as selecting the best-performing R1234ze(E)/IL mixture and offering directions for future improvement.