Researches On Fundamental Physicochemical Properties And Cycle Characteristics Of Novel Absorption Refrigeration Working Pairs Containing Ionic Liquid

With the energy shortage, environmental problems and globe warming becoming increasingly serious, absorption refrigeration technologies have attracted more and more attention from the energy researchers all over the world because of their advantages of environmental friendly and utilizing the low grade energy. The most widely-used working pairs are H2O/LiBr and NH3/H2O. Because of the inherent defects of crystallization, corrosion and toxicity, applications of traditional working pairs, H2O/LiBr and NH3/H2O, are largely limited. Ionic liquids possess distinctive properties of negligible vapor pressure, good thermal stability, no corrosion, no crystallization and favorable solvating properties, which make ionic liquids to be excellent alternatives for the traditional absorbent.Supported by the National High Technology Research and Development Program of China (863, No.51276180), ionic liquid working pairs of [mmim]DMP/CH3OH with great potential for commercial applications have been screened out and the vapor-liquid equilibrium of [mmim]DMP/CH30H has been investigated. On the basis of preliminary research results, further researches have been conducted.1. Based on the vapor pressure data of [mmim]DMP/CH30H, the UNIFAC model and the Wilson model, which are used to predict the vapor pressures and excess enthalpies of [mmim]DMP/CH3OH, respectively, were correlated. The investigation on the thermodynamic performances of [mmim]DMP/CH3OH absorption refrigeration were conducted.2. Thermal conductivities of [mmim]DMP/CH30H and [mmim]DMP/H20with different mole fractions of [mmimJDMP were measured by3ω method. The experimental data were correlated by the Random Mixing model.3. The dynamic modeling and simulation based on components for parallel type and series type double effect absorption refrigeration using [mmim]DMP/CH30H were conducted. The simulation results were compared with the experimental results in literature.From the above mentioned work, some conclusions were obtained. The COP of [mmim]DMP/CH30H cycle is lower than that of LiBr/H2O cycle, but generally higher than that of NH3/H2O cycle. The adding of [mmim]DMP into CH3OH can remarkably enhance its heat transfer performance, which is conducive to improve the thermal performances of [mmim]DMP/CH30H cycle. Through the comparison to the experimental results in literature, it is indicated that the dynamic model well describes the characteristics of the systems and can be used to the further parameter optimization and control designment.Generally speaking, the solubilities of refrigerant in the common ionic liquid are not very high, which is an obstacle to improvement of thermal performances. In order to improve the solubilities of refrigerant in ionic liquid, the working pairs with NH3as refrigerant and [bmim]Zn2Cl5as absorbent were proposed, which involve both physical adsorption and chemical absorption mechanisms. The research has been supported by the National Natural Science Foundation of China (No.51276180), and the related researches are listed as follows:1. The device of vapor pressure measurement for [bmim]Zn2Cl5/NH3was built, and pressures of [bmim]Zn2Cl5/NH3for T=(323.15-563.15) K were measured by a static method. The experimental data were correlated by a modified UNIFAC model.2. TG scan and DSC scan for [bmim]Zn2Cl5were conducted and heat capacity data were obtained. Mole excess enthalpy data of the binary systems [bmim]Zn2Cl5/NH3for T=(288.15-333.15) K were measured, which were correlated by the NRTL model.3. Based on the heat capacity of [bmim]Zn2Cl5, vapor pressure and excess enthalpy for [bmim]Zn2Cl5/NH3, the investigation and analysis on the thermodynamic performances of [bmim]Zn2Cl5/NH3absorption refrigeration were conducted, which were compared with that of NaSCN/NH3system.From the above mentioned work, we got some conclusions. The solubilities of ammonia in [bmim]Zn2Cl5are higher than that in other ionic liquids, the specific heat capacity of [bmim]Zn2Cl5is small, and the excess enthalpy data of [bmim]Zn2Cl5/NH3are also not very high. All the three parameters are conducive to the improvement of the thermodynamic performances. Through the investigation on the thermodynamic performances of [bmim]Zn2Cl5/NH3system, it is indicated that thermal performances of [bmim]Zn2Cl5/NH3system are better than that of NaSCN/NH3system. Even when the evaporating temperature is low or the condensing temperature and absorption temperature are high, the thermal performances of [bmim]Zn2Cl5/NH3system are still good and the circulation ratios of system are still acceptable. In a word, the working pairs of [bmim]Zn2Cl5/NH3possess great potential for industrial applications and good prospects for commercial development.