Study On The Thermodynamics Of H₂O-[Mmim]Cl System By Calorimetry And Its Application As A Working Pair Of Absorption Cycle

Absorption cycle is an important energy saving and environmental protection technology which can be directly driven by low-grade heat and not use CFCs as working fluid. Working pair of cycle has crucial influence on operating conditions and energy conversion efficiency, which has always been paid great attention. This paper focus on two subjects: thermal properties of working pairs and performance analysis of the absorption cycle.This paper introduced H₂O and ionic liquids as a new working pair. The ionic liquids has several special characters, such as environmentally benign medium, excellent solubility, high boiling point and low vapor pressure.1, 3-dimethylimidazolium chloride ([Mmim]Cl) was synthesized by gas-liquid phase reaction, starting from N-methylimidazole and excess CH₃Cl. Then structural characterization and purity measurement have done to the refined sample.Heat capacities of [Emim]Br (aq) and [Mmim]Cl (aq) with different concentration, were measured from 298.15K to 358.15K by BT2.15 Calvet microcalorimeter. Then, a temperature and concentration dependence had been built respectively. Based on the experimental data, the excess molar heat capacity, the apparent molar heat capacity and partial molar heat capacity for the both systems were calculated.Then, integral heat of solutions of [Mmim]Cl with various molalities were determined at T=298.15K in water. The relationship between heat of solution and molality has also been fitted.Based on the relations of the thermodynamics, the enthalpy-concentration diagram at the pressure of 101.325kPa has been made.Set up the thermal property models of the ionic liquids and the calculation program of the absorption cycle based on the models. The performance of the cycle with the working pair H₂O-[Mmim]Cl was studied. Compared with the H₂O-LiBr cycle, the H₂O-[Mmim]Cl cycle has higher coefficient of performance. The influences of generation temperature, evaporation temperature, absorption temperature to the coefficient of performance, circular ratio and cooling capacity were also studied.