Study of the absorption process of ammonia in ionic liquids for absorption refrigeration systems
- Autores: Ronny Rives Sanz
- Directores de la Tesis: Alberto Coronas Salcedo (dir. tes.)
- Lectura: En la Universitat Rovira i Virgili ( España ) en 2021
- Idioma: español
- Tribunal Calificador de la Tesis: Benoit Stutz (presid.), Joan Manel Vallés Rasquera (secret.), María del Carmen Venegas Bernal (voc.)
- Programa de doctorado: Programa de Doctorado en Ingeniería Termodinámica de Fluidos por la Universidad de Burgos; la Universidad de Santiago de Compostela; la Universidad de Valladolid y la Universidad Rovira i Virgili
- Materias:
- Enlaces
- Tesis en acceso abierto en: TDX
- Resumen
Recently, ionic liquids have been proposed as alternative, adjustable absorbents for natural refrigerants in absorption refrigeration systems. However, the high viscosity, low mass diffusivity, and the lack of reliable information on the thermophysical properties of their mixtures with these refrigerants are important limitations for their effective implementation.
The main objective of this thesis is to study the absorption process of ammonia in ionic liquids to determine the time evolution of the absorption rate and the concentration profiles in the absorbent fluid. These types of experimental data are useful for selecting ionic liquids suitable as absorbent of ammonia in new absorption refrigeration and heat pump systems.
The ionic liquids studied are: ethylammonium nitrate (EAN); 1-ethyl-3-methylimidazolium-tetrafluoroborate ([emim][BF4]); and 1-butyl-3-methyl-imidazolium-tetrafluoroborate ([bmim][BF4]), with different ammonia solubilities and viscosities. The Pressure Drop Method was implemented to determine the time evolution of the absorption rate of ammonia in the ILs selected, throughout the absorption process. Absorption experiments were performed at infinite dilution of ammonia, at the temperatures of 293.15 K and 303.15 K, during more 15 hours. The determined absorption rate of ammonia in the ILs was more than 20 times lower than in water. To obtain the concentration profiles in the absorbent, it was implemented an Optical Digital Interferometry (ODI) method, that allows also to determine the mass diffusivity of ammonia in the ionic liquids selected.
The ammonia diffusivity ranges from (1.18 to 5.71) × 10-10 m2/s and follows the order: [EAN]>[emim][BF4]>[bmim][BF4]. These values are more than 10 times lower than those for water, conventional absorbent of ammonia.
This thesis provides new experimental absorption data on the mass diffusivity of natural refrigerants in ILs, essential information to proceed to the detailed study of the heat and mass transfer performance of these working pairs, and therefore, for the proper design of ILs-based absorption system.
