The Study Of Vapor-liquid Equilibrium For New Working Fluids In Absorption Heat Pumps

The open absorption heat pump system(OAHP)is the development of the conventional absorption system.Compared with the latter system,the open absorption heat pump system has the advantage of using the partial pressure difference of vapor between the moist air and solutions,thus improving the thermal grade of the recycled waste heat.The open absorption heat pump system mostly uses conventional lithium bromide solution as working fluid.The lithium bromide solution has been widely used in absorption system for its large latent heat of evaporation and good hygroscopicity for quite a long time.However,affected by its connatural disadvantages of crystallization and corrosion,the further implementation of absorption systems was restricted.Therefore,it's absolutely essential to search for a new kind of working fluid with superior physical and thermodynamic properties and without disadvantages of lithium bromide solution mentioned above.In that context,researches on three kinds of potential working fluids in absorption heat pumps have been conducted in this work and are mainly on vapor-liquid equilibrium(VLE).The details are as follows:(1)The research progress of the open absorption heat pump is summarized in this work.Besides,literatures of researches on lithium bromide solution,the most widely used working fluid in absorption system,are also concluded in this work.Thus,a fundermantal work was made for further researches on additives of LiBr aqueous solutions.Two kinds of ionic liquids with superior properties and HCOOK aqueous solutions with high mass concentrations were selected.These new working fluids have great potential and are worth further researches.(2)The boiling point method is adopted in this work on the basis of abundant of literature research and fully comparison of present measurements of VLE.Moreover,a set of measuring system for the vapor-liquid equilibrium of solutions containing high boiling point solute is designed and set up.(3)The vapor-liquid equilibrium data of binary system of HCOOK/H2O and ternary systems of[Emim]Ac/LiBr/H2O and[Emim]Cl/LiBr/H2O were measured and regressed by the Antoine type equation and the CHEN-NRTL model.Three kinds of systems were all regressed by the Antoine type equation.Besides,the AARDs%between the experimental results and the calculated results were 0.34%,0.61%and 0.94,respectively.The binary system of HCOOK/H2O were also regressed by the CHEN-NRTL model and the AARD%between the experimrntal and calculated results was 2.85%,which prove that the results are in excellent accuracy and consistency,thus,providing reliable foundations of properties for the further study of these new promising working fluids in open absorption heat pump systems.