Abderrahim Samaouali

In this study, thermodynamic properties such as water activity, osmotic coefficient, and saturation points of the aqueous mixture in the system D-Sucrose + Water + ammonium nitrate (AN) were determined at 298.15 K. The measurements were carried out on the mixtures of concentrations of NH₄NO₃ (ranging from 0.1 to 6 mol·kg⁻¹) and D-sucrose (from 0.1 to 4 mol·kg⁻¹) using our hygrometric method. Powder X-ray diffraction (XRD) and attenuated total reflection–Fourier transform infrared (ATR-FTIR) spectroscopy were used to characterize the solid phases crystallized during the supersaturation of the solution. Other thermodynamic quantities such as the solute activity coefficients, excess Gibbs energies, transfer energies, and solute solubilities were calculated using the Pitzer–Simonson–Clegg (PSC) model. The results obtained indicate that at an AN concentration lower than 1 mol·kg⁻¹, the system exhibits increasingly negative deviations from ideality, and that NH₄NO₃ promotes the salting-out effect of sucrose.

The NH₄NO₃ (ammonium nitrate) and sucrose (sugar) solution hold significant importance in various domains. Ammonium nitrate is commonly used as a fertilizer in agriculture, providing essential nutrients for plant growth. It can also be used as an explosive under controlled conditions. As a chemical reagent, it is involved in the production of other chemical compounds. On the other hand, sucrose is widely used as a sweetener in food, providing energy and enhancing the flavor of food and beverages. It is also employed in food preservation methods to inhibit bacterial growth. Overall, the NH₄NO₃ and sucrose solution play a crucial role in agriculture, the chemical industry, and the food sector. We are interested in studying the influence of an electrolyte and a non-electrolyte, such as NH₄NO₃-Sucrose-H₂O, on the properties of a solution. The hygrometric technique was employed to acquire new thermodynamic data related to water activity in saturated aqueous mixtures of the water/D-sucrose/ammonium nitrate (AN) system. This study spans a wide range of NH₄NO₃ molalities, from 0.1 to 6 mol·kg⁻¹, and includes various D-sucrose concentrations between 0.1 and 4 mol·kg⁻¹. The experimental results were then compared with predictions from three modeling approaches: the Dinane model (ECA), the Lin et al. equation, and the Leitzke–Stoughton (LS II) model. Powder X-ray diffraction (XRD) and attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy were employed to investigate the solid-phase characteristics of the system. The experimental osmotic coefficient data, derived from water activity measurements, were interpreted using the Pitzer–Simonson–Clegg (PSC) model, which provided a satisfactory correlation across the studied concentration range. At AN concentrations below 1 mol·kg⁻¹, the system exhibited increasing negative deviations from ideality. The calculated activity coefficients of D-sucrose and AN, as well as the Gibbs free energy associated with the transfer of AN from pure water to the binary D-sucrose/water medium, suggest that both solutes significantly contribute to salting-out effects in the aqueous phase.

This review provides an analysis of advancements in the design and performance assessment of Darrieus wind turbines over the past decade, with a focus on the contributions of computational fluid dynamics (CFD) to this field. The primary objective is to present insights from studies conducted between 2014 and 2024, emphasizing the enhancement of Darrieus wind turbine performance through various technological innovations. The research methodology employed for this review includes a critical analysis of published articles related to Darrieus turbines. The focus on the period from 2014 to 2024 was considered to highlight recent parametric CFD studies on Darrieus turbines, avoiding overlap with previously published reviews and maintaining originality relative to existing review works in the literature. By synthesizing a collection of articles, the review discusses a wide range of recent investigations utilizing CFD modeling techniques, including both 2D and 3D simulations. These studies predominantly utilize the “Ansys-Fluent” V12.0 and “STAR CCM+” V9.02 solvers to evaluate the aerodynamic performance of Darrieus rotors. Technological advancements focus on modifying the geometry of Darrieus, including alterations to blade profiles, chord length, rotor diameter, number of blades, turbine height, rotor solidity, and the integration of multiple rotors in various configurations. Additionally, the incorporation of flow deflectors, the use of advanced blade shapes, such as V-shaped or twisted blades, and the application of an opening ratio on the blades are explored to enhance rotor efficiency. The review highlights the significant impact of these geometric modifications on key performance metrics, particularly the moment and power coefficients. A dedicated section presents CFD-derived visualizations, including vorticity fields, turbulence contours illustrated through the Q-criterion, velocity vectors, and dynamic pressure contours. These visualizations provide a description of the flow structures around the modified Darrieus rotors. Moreover, the review includes an analysis of the dynamic performance curves of Darrieus, which show improvements resulting from the modifications of the baseline design. This analysis covers the evolution of pressure coefficients, moment coefficients, and the increased power output of Darrieus.

The aim of this study was to measure the thermophysical properties (thermal conductivity, volumetric thermal capacity, thermal diffusivity, and thermal effusivity) of red earth stabilized with cement and substituted with waste glass powder. Several samples (red earth) were stabilized with 6% and 12% cement and incorporated with different percentages of waste glass powder, which varied from 10% to 30%. The bulk density of the 12 samples was measured in the dry state and at room temperature. All samples were analyzed by a scanning electron microscope (SEM). The thermal conductivity and specific heat of the composite materials were measured experimentally with a thermal conductivity device (CT meter) in the dry state and at ambient temperature. The experimental results showed a decrease in the thermophysical parameters of stabilized red earth containing 12% cement and substituted by 30% glass powder. The following results were obtained: 53.97% for thermal conductivity, 45.42% for volumetric specific heat, 15.66% for thermal diffusivity, and 49.88% for thermal effusivity. The bulk density of the red earth also decreased by 13.66% in the dry state at ambient temperature. Stabilization with 6% and 12% cement played an important role in the compactness of the material and, consequently, improved its thermophysical performance. The composition of this new ternary material significantly affected the thermophysical properties of the red earth.