Experimental Studies On The Vapor Pressures Of Working Fluids HCOOK+H₂O And CaCl₂+H₂O For Absorption Heat Pumps

Heat transformers also known as the second type of absorption heat pumps,is one of the most convenient ways to lift the temperature and grade of thermal energy,which can make the effective use of the low-taste thermal energy.The research on the new working fluids for absorbent heat pumps has never stopped at home and abroad.This paper has chosen two kind of inorganic salt brine HCOOK+H₂O and CaCl₂+H₂O and discussed their possibility as working fluids for the absorption heat pumps.The main contents were as follows:?1?The static experimental system of vapor pressure measurement was designed and built,and the reliability of the experimental system was tested by pure water and25%mass concentration of sodium chloride aqueous solution.The results showed that the experimental system can be used for the reliable and accurate measurement of vapor pressures of HCOOK+H₂O and CaCl₂+H₂O solutions.?2?The vapor pressure data of HCOOK+H₂O and CaCl₂+H₂O were measured with this static experimental system,which included the 77 groups vapor pressure data of HCOOK+H₂O in the temperature range of 323.15K³73.15K and mass concentration range of 10%⁷0%,and the 55 groups vapor pressure data of CaCl₂+H₂O in the temperature of 323.15K³73.15K and mass concentration of 10%⁵0%.?3?The vapor pressure data of HCOOK+H₂O and CaCl₂+H₂O were fitted with the Antoine polynomial equation and the Pitzer expansion model.The results showed that the fitting effects of the two models were both good.The largest pressure relative deviations of two models for CaCl₂+H₂O was both at nearby 50%mass concentration and 323.15K temperature,it can be deduced that in the high concentrated and low temperature ranges the experimental pressure value was higher due to the proximity of crystallization concentration.?4?The extensibility of Antoine polynomial equation and Pitzer extension model was analyzed respectively with the vapor pressure data of HCOOK+H₂O and CaCl₂+H₂O.The results showed that in the aspect of temperature extensibility,the average pressure relative deviations of the two models in the low and medium concentration ranges were less than 1%,but the extrapolation error of the Pitzer expansion model increased in the high concentration zone.In the aspect of concentration interval extensibility,the extrapolation error of Antoine polynomial equation was larger,and the Pitzer expansion model has good extensibility in the low concentration zone.However,it cannot judge which model had better prediction accuracy in the high concentration range at present.