title: Determining the composition of ammonia/water mixtures using short-wave near-infrared spectroscopy.
abstract: This paper proposes a methodology based on short-wave near-infrared spectroscopy to determine the ammonia content of ammonia/water mixtures with ammonia mass fraction in the range 0.35-0.65. Establishing this methodology meant modeling the relationship between the pressure bar (15-25)bar, temperature (20-50)°C and composition of the ammonia-water in the mixture (0.35-0.65 in ammonia mass fraction) with absorbance at 1033nm. The experiments were designed to optimize experimental work. A 2(3) factorial design+3 center points was used to establish and analyze the significance of the variables in the absorbance using analysis of variance (ANOVA). A linear model for absorbance was obtained using the least squares method. The trueness of the results versus the values obtained was assessed using a reference method; density measurement was chosen for this study. The accuracy of the results in terms of root-mean-square deviation (RMSD) was 3.7%. The methodology proposed represents a fast alternative for the "in-situ" measurement of the ammonia composition of ammonia-water mixtures in absorption refrigeration systems.
authors.affiliation: Group of Research in Applied Thermal Engineering - CREVER, Mechanical Engineering Department, Spain.
authors.forename: M Isabel
authors.initials: MI
authors.lastname: Barba
authors.affiliation: Group of Research in Applied Thermal Engineering - CREVER, Mechanical Engineering Department, Spain.
authors.forename: Daniel
authors.initials: D
authors.lastname: Salavera
authors.affiliation: Analytical and Organic Chemistry Department, Universitat Rovira i Virgili, Tarragona, Spain. Electronic address: mariasoledad.larrechi@urv.cat.
authors.forename: M Soledad
authors.initials: MS
authors.lastname: Larrechi
authors.affiliation: Group of Research in Applied Thermal Engineering - CREVER, Mechanical Engineering Department, Spain.
authors.forename: Alberto
authors.initials: A
authors.lastname: Coronas
keywords: Ammonia content determination; Ammonia/water mixture; Experimental design; Short-wave near-infrared spectroscopy