Chitosan is a biopolymer derived from chitin and the most abundant polysaccharide in nature after cellulose. This biopolymer has been applied in different areas due its biodegradability and biocompatibility properties. Modifications of chitosan structure by cross-linking chemical agents can alter its physical, chemical, and morphological characteristics. The present work aimed at studying the structural characteristics of chitosan/polyvinyl alcohol (PVA) spheres cross-linked with glutaraldehyde submitted to oven-drying and freeze-drying processes. The thermal-treated of spheres and chitosan (control sample) were analyzed by XRD, SEM and FTIR techniques. Multivariate statistical analysis, PCA, was applied to samples IR spectra. According to results, the freeze-dried spheres showed a smaller crystal size (6.032 nm), while the oven-dried spheres presented a smaller crystalline phase (3.49%). MEV images have encompassed the different surfaces of the manufactured spheres as a result of drying methods. Slight chemical changes were observed in the IR spectra from the cross-linked spheres. In addition, PCA has revealed different clusters referred to the structural modifications. Therefore, the increasing of openness and receptivity for chemical reactions, as well as the adsorption capacity, could enable different applications of the chitosan, mainly the adsorption properties to remove residues and for water treatment.

Abstract This paper presents a thermodynamic model developed for a prototype absorption chiller using NH3/LiNO3 with 10 kW of nominal capacity. The study was undertaken using thermodynamic modeling based on the mass and energy balance, takes the overall heat transfer coefficients into consideration and uses the characteristic equation method. First, the results obtained from the thermodynamic modeling developed were compared with those obtained from the characteristic equations of thermal power activation and the cooling capacity. These showed good agreement with the experimental data, there being maximum relative errors of around 5% for most of the operational conditions of the system. Secondly, a parametric analysis was made by altering the variables, such as temperature, mass flow rate, and configuring the heat dissipation that influences the overall performance of the prototype chiller.