An Investigation of Error Sources in Computational Fluid Dynamics Modelling of a Co-current Spray Dryer

The paper is focused on identifying error sources in computational fluid dynamics(CFD) predictions of a spray drying process. Seven groups of drying and atomisation parameters were selected for analysis and 13 simulation trials were performed. The theoretical results were compared with experimental data and sensitivity of the simulation results to the analysed factors was determined. The following parameters affecting the accuracy of CFD spray modelling were found: gas turbulence model, particle dispersion, atomising air, initial parameters of atomisation and heat losses to the environment. A major difference in the errors committed during modelling of spray drying process for fine and coarse sprays was observed.     

Ionic liquids as electrolytes

Salts having a low melting point are liquid at room temperature, or even below, and form a new class of liquids usually called room temperature ionic liquids (RTIL). Information about RTILs can be found in the literature with such key words as: room temperature molten salt, low-temperature molten salt, ambient-temperature molten salt, liquid organic salt or simply ionic liquid. Their physicochemical properties are the same as high temperature ionic liquids, but the practical aspects of their maintenance or handling are different enough to merit a distinction. The class of ionic liquids, based on tetraalkylammonium cation and chloroaluminate anion, has been extensively studied since late 1970s of the XX century, following the works of Osteryoung. Systematic research on the application of chloroaluminate ionic liquids as solvents was performed in 1980s. However, ionic liquids based on aluminium halides are moisture sensitive. During the last decade an increasing number of new ionic liquids have been prepared and used as solvents. The general aim of this paper was to review the physical and chemical properties of RTILs from the point of view of their possible application as electrolytes in electrochemical processes and devices. The following points are discussed: melting and freezing, conductivity, viscosity, temperature dependence of conductivity, transport and transference numbers, electrochemical stability, possible application in aluminium electroplating, lithium batteries and in electrochemical capacitors.     

Aboveground nitrogen in relation to estimated total plant uptake in maize and bean

The main objective of this field study was to estimate the total plant uptake of soil mineral N in maize (Zea mays L.) and common bean (Phaseolus vulgaris L.) grown in crop rotations under different N content in Nicaragua. Secondary objectives were to estimate the fraction of the measured soil mineral N content taken up in this way, and to determine how the measured N in plant aboveground parts was related to the total mineral N uptake. A large variation in N content was obtained by using data from fertilisation experiments. Plant total N uptake was estimated as the residual N in a mass balance calculation of soil mineral N. Mineral N content in the top 0–0.3 m soil layer in the field cultivations and in tubes isolated from root uptake, and N content in aboveground plant parts were measured every 30 days. Estimated plant total uptake of soil mineral N varied considerably (2.5–14 g N m⁻² 30 day⁻¹) over periods and N treatments. The range of variation was similar for maize and bean. The fraction of the soil mineral N that was taken up by the plant daily varied more in maize (about 0.03–0.12 day⁻¹) than in bean (about 0.05–0.08 day⁻¹). Our results suggest that monthly changes in N in aboveground plant parts were linearly related to plant total N uptake during the same period. Aboveground plant N constituted between about 55% and 80% of total uptake of soil mineral N in maize depending on period within season, whereas for bean it was more constant and smaller (about 40%).     

Persistent problems and practices in information systems development: a study of mobile applications development and distribution

The widespread uptake of mobile technologies has witnessed a re‐structuring of the mobile market with major shifts in the predominance of particular firms and the emergence of new business models. These sociotechnical trends are significant in the ways that they are influencing and shaping the working lives of software professionals. Building on prior research investigating the persistent problems and practices of systems development, this paper examines mobile applications development and distribution. A qualitative study of 60 developers based in Sweden, the UK and the USA was analysed around the interrelated problems of diversity, knowledge and structure. The analysis revealed how platform‐based development in an evolving mobile market represents significant changes at the business environment level. These changes ripple through and accentuate ongoing trends and developments, intensifying the persistent problems and challenges facing software developers.     

Carbon materials and catalytic wet air oxidation of organic pollutants in wastewater

The use of carbon materials as catalytic support or direct catalyst in catalytic wet air oxidation (WAO) of organic pollutants is reviewed. The discussion covers important engineering aspects including the characterisation, activity and stability of carbon catalysts, process performance, reaction kinetics and reactor modelling. Recommendations for further research in catalytic WAO are outlined.     

Oxidative dehydrogenation of ethane on Pt–Sn impregnated monoliths

The oxidative dehydrogenation of ethane was studied over Pt–Sn impregnated monoliths at 1 bar, 600–900 °C and with different contents of oxygen, hydrogen and steam in the feed gas. As expected a decrease in oxygen in the feed led to a decrease in the conversion of ethane due to lower temperatures in the reactor. Adding steam to the feed showed no effect on the ethane conversion or the ethene selectivity. When the hydrogen/ethane ratio in the feed was varied from 0 to 0.5 at 700 and 850 °C, it resulted in a significant increase in the selectivity to ethene while the ethane conversion remained relatively unchanged. At 700 °C the selectivity increased from about 50% to 93% (carbon basis) with only a small decrease in the conversion of ethane. The results clearly show that both Pt and Sn have a catalytic effect. Pt caused the ethane conversion to rise and addition of Sn resulted in much better ethene selectivity. However, even though Sn alone showed some catalytic effect at lower temperatures, it cannot explain the great difference between the Pt and Pt–Sn catalysts. A reasonable assumption is therefore that there exist interactions between Pt and Sn that gives the Pt–Sn catalysts excellent properties for oxidative dehydrogenation of ethane, in particular upon addition of hydrogen.     

Einige fragen der tunneltheorie der wasserstoffüberspannung—II. Die temperaturabhängigkeit der stromdichte und die beträge der quanteneffekte

The dimensions of the potential barrier involved in hydrogen and deuterium evolution on mercury are computed from the experimental values of the effective activation energies on the assumption that the barrier has a parabolic shape. The ratio of the pre-exponential factors and the isotopic separation factor obtained theoretically in this manner are in good agreement with experimental data. The calculation shows that the tunnel effect plays a substantial but still moderate role in the case under study. Comparison with the results of an earlier derivation based on Eckart's potential function allows the determination of the most probable shape of the true barrier. The usually assumed dimensions are shown to be incorrect.

Résumé

On calcule les dimensions de la barrière de potentiel pour le dégagement d'hydrogène et de deutérium sur le mercure en partant des valeurs expérimentales de l'énergie d'activation et en supposant que la barrière a une forme parabolique. Le rapport des facteurs préexponentiels et le facteur de séparation isotopique ainsi obtenus théoriquement sont en accord avec les données expérimentales. Le calcul montre que l'effet tunnel ne peut être négligé mais qu'il ne joue cependant qu'un rôle moyen dans le cas étudié. La comparaison avec les résultats d'une dérivation précédente partant de la fonction de potentiel d'Eckart permet de déterminer la forme la plus probable de la barrière de potentiel. Il est montré que les valeurs habituellement admises pour les dimensions de cette barrière ne sont pas correctes.