Determinación experimental y modelización de propiedades termodinámicas de mezclas de CO2 con absorbentes para refrigeración por compresión/resorción

Resumo

The present work has, in the first place, the purpose of expanding the existing database of thermodynamic properties of the CO2 / acetone mixture, relevant for the study of compression / resorption refrigeration systems, by means of the experimental determination of vapor pressure and density of CO2 / acetone mixtures in a wide range of composition and temperature. In addition, the thermodynamic properties of this mixture have been modeled with different equations of state and mixing rules, proposing the Peng-Robinson with the Van der Waals mixing rule and the Boston-Mathias alpha function for presenting less deviations with respect to the experimental data on liquid-vapor equilibrium, density, excess enthalpy and heat capacity. On the other hand, a study has been carried out on other CO2 absorbents, for a compression / resorption refrigeration system. After a literature review, two ionic liquids have been identified as potential absorbents for this application: 1-Ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide [emim] [NTf2] and 1-Ethylimidazolium nitrate [eim] [NO3]. Since the thermodynamic properties data are very scarce, it was decided to measure the vapor pressure in the range 283.15 K to 353.15 K and CO2 molar fractions lower than 80%. The density of [eim] [NO3] was also measured. Finally, to analyze the suitability of the mixtures studied for compression / resorption refrigeration applications, the Dühring diagrams are presented for illustrative purposes, which allow us to represent the thermodynamic cycles and to know the pressures, temperatures and compositions of the mixture in the cycle. . The results show that the CO2 / acetone mixture for refrigeration applications at -10ºC and heat dissipation at 35ºC, the high pressure is 50 bar, for a mixture with a CO2 mass fraction of 70%, while for the CO2 / [emim] [NTf2] the CO2 mass fraction of the mixture is 12% and 7% for CO2 / [eim] [NO3].