Daniel Salavera

Viscosity Mixing Rules for Binary Systems Containing One Ionic Liquid

In this work the applicability of four of the most commonly used viscosity mixing rules to [ionic liquid (IL)+molecular solvent (MS)] systems is assessed. More than one hundred (IL+MS) binary mixtures were selected from the literature to test the viscosity mixing rules proposed by 1) Hind (Hi), 2) Grunberg and Nissan (G-N), 3) Herric (He) and 4) Katti and Chaudhri (K-C). The analyses were performed by estimating the average (absolute or relative) deviations, AADs and ARDs, between the available experimental data and the predicted ideal mixture viscosity values obtained by means of each rule. The interaction terms corresponding to the adjustable parameters inherent to each rule were also calculated and their trends discussed.

Thermophysical Properties and Heat and Mass Transfer of New Working Fluids in Plate Heat Exchangers for Absorption Refrigeration Systems

Ammonia/lithium nitrate and ammonia/(lithium nitrate + water) have been proposed as suitable working pairs for absorption refrigeration systems driven by low-temperature heat sources. The use of water in the absorbent of the ternary mixture reduces the viscosity of the binary mixture and increases the affinity between the refrigerant (ammonia) and the absorbent, which should have a positive effect on the absorption process. In this paper, a brief review on the thermodynamic and transport properties available in the open literature for NH3/LiNO3 and NH3/(LiNO3 + H2O) mixtures is presented, and the most significant results of an experimental characterization of absorption and desorption processes taking place in plate heat exchangers are discussed.

A method based on near-infrared spectroscopy for the in-situ determination of the ammonia concentration in ammonia/water mixtures in an absorber test bench

This paper discusses the development and implementation of a method based on NIR spectroscopy for the in-situ determination of the ammonia mass fraction of ammonia/water mixtures in an absorber test bench. The calibration model was established using a static measuring system. A cell was designed and constructed to prepare and measure samples at the ammonia mass fractions (0.332-0.482), pressures (3.4-4.6), bar and temperatures (25.0-35.5) °C typical in absorption refrigeration systems. A quadratic model for absorbance at 1041nm was established and validated. The root-mean-square deviation (RMSD) of the results was 2.1%. To implement NIR spectroscopy in the absorber test bench, a new flow cell was designed. The calibration model was transferred and used in the conditions of the absorber test bench. In these experimental conditions, the model was statistically validated using density measurements as a reference method for measuring the ammonia mass fraction. The root-mean-square deviation between the ammonia mass fractions obtained using the two methods was 1.1%.

Implementing a method based on near infrared spectroscopy for the “in-situ” determination of ammonia/water composition in an absorber test bench

This study presents the first results of composition measurement in an ammonia/water mixture determined at real time using near-infrared (NIR) spectroscopy in an absorber test bench. Two cells were designed and constructed; a static cell for calibrating and a dynamic cell for measuring in the absorber test bench. The ammonia absorption band was not significantly affected by the solution flow rate and neither by small variations in the temperature and pressure. A linear regression model between the absorbance value at 1033 nm and the ammonia concentration was established. This model was used to estimate the concentration in an ammonia/water absorber test bench. The methodology was validated by density measurements of the samples. The value of the mean deviation was 0.0024.