Operation of an absorption heat transformer using water/ionic liquid as working fluid

This work presents the first experimental results obtained with a single stage absorption heat transformer (AHT), which was operated with the working fluid water/ionic liquid. The ionic liquid (IL) used in this work was 1-ethyl-3-methyl-imidazolium methanesulfonate (EMIM OMs). Several sets of experiments were conducted by varying the inlet temperatures of the external circuits and the internal flow rates. The coefficient of performance (COP) decreases with increasing high temperature and decreasing medium temperature. At higher internal flow rates, the COP increases due to the improved efficiency of the solution heat exchanger and higher heat flows in the apparatuses. The comparison of the experimental results with simulation results shows a good agreement at low temperature lifts. At higher temperature lifts and lower heat flows in the apparatuses, the influences of heat losses, pump duties and uncertainties let the experimental results diverge from the simulated ones. The highest experimental COP was 0.43 at a heat flow of 5.5 kW in the absorber and a temperature lift of 18.5 K. The highest temperature lift was 47 K. The corresponding COP was 0.27 and the heat flow in the absorber 1.7 kW.