The Properties Research Of The New Working Pairs Containing Ionic Liquid For Absorption Heat Pump

Absorption heat pump can recover and utilize waster heat with lower temperature,it has important significance for energy comprehensive utilization,recovering industrial waste heat and environment protection.The working pair has important influence in the operational performance and operating costs.The conventional working pairs have the problems of corrosion,crystallization,high working pressure,toxicity.So many people have pay attention on the study of the working pairs of the heat pump.Ionic liquid(IL) were known as low temperature molten salts,which are solely composed of ions and have many unique attributes,e.g.good thermal and chemical stabilities,wide liquid-state range,negligible vapor pressure et al.Due to these features,it's possible that ionic liquids could be used as the novel working fluids in the absorption heat pump.In this paper, the binary solution containing ionic liquid were chosen as novel working fluids,the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate(EMISE),1-ehtyl-3-methylimidazolium diethylphosphate([EMIM]DEP)act as absorbent and water acts as refrigerant,we have prepared the ionic liquids,characterized the structure and measured the thermodynamic and physical properties,providing the basic information for the research of the thermodynamic model and establishing the foundation for calculating the performance of an absorption heat pump.The working fluid of the absorption heat pump should have a considerable negative deviation from Raoult's law in the aspect of the vapor-liquid equilibrium.Therefore,the saturated vapor pressure of the two binary solutions at the different temperature and the different IL-containing were measured,correlated by the nonelectrolyte activity coefficient model and predicted the vapor pressure of the two systems at the temperature of 323.15K. The results showed that the NRTL model could suitably predict the vapor-liquid equilibrium of the solution containing ionic liquid,the two systems had a considerable negative deviation from Raoult's law,so they could be chosen as potential working fluid.In this paper,the mixing enthalpy of the ionic liquid EMISE/[EMIM]DEP with water at the temperature of 298.15K and the heat capacity of the binary solution containing ionic liquid at the different temperatures and the different IL-containing were measured.The results showed that the ionic liquid EMISE/[EMIM]DEP has exothermic heat when they mixed with water and the releasing heat first increased and then decreased with the increasing of the IL molar fraction.The mixing heat of the[EMIM]DEP with water was much larger than that of the EMISE with water.The heat capacity of the two binary solutions showed a linear relationship with the temperature,and decreased with the increasing of the molar fraction of the ionic liquid EMISE/[EMIM]DEP.The heat capacities were correlated by the empirical formula,the results showed the calculated data had good agreement with the experimental data.The viscosity and the density of the binary solution EMISE/[EMIM]DEP with water at the different temperatures and the different IL-containing were respectively measured by the viscometer and specific gravity balance.The results showed that the viscosity of the ionic liquid EMISE/[EMIM]DEP were decreased with the addition of water.The viscosity were decreased with the molar fraction of the ionic liquid and tended to a limiting value.The densities also showed a linear relationship with the temperature,the values were decreased with the addition of water and the increasing of the temperature.The viscosity and the density were respectively correlated by the empirical formula which containing the temperature and the molar fraction of the IL,the experimental data showed good agreement with the caculated data.