The generalized Lévêque equation and its practical use for the prediction of heat and mass transfer rates from pressure drop

Based on the generalized Lévêque equation (GLE) a new type of analogy between pressure drop and heat transfer has been discovered, that may be used in the cross corrugated channels of chevron type plate heat exchangers, in packed beds, in tube bundles, in crossed rod matrices or in many other spacewise periodic arrangements.Experimental data on heat transfer in tube bundles in crossflow, both inline, and staggered arrangements, had been recently tested in greater detail. Using an empirical correlation for pressure drop in these arrangements from the literature that has been successfully tested against a large number of experimental pressure drop data, heat transfer data collected earlier could be very well represented from the pressure drop correlation and the GLE. The data for staggered bundles have been shown to be in better agreement with this new method, than with the existing empirical heat and mass transfer correlations. Somewhat larger deviations for inline tube bundles had been found at lower Reynolds numbers. Here a simple and physically reasonable correction function of Re is presented, which leads to a better agreement for the inline bundles, too.Additionally, it can be shown for a number of literature data on tube bundles and on crossed rod matrices that the agreement with the GLE prediction is even better if original pressure drop data from the same sources are available in place of a pressure drop correlation.The method results in reasonable heat or mass transfer predictions from frictional pressure drop, which may be widely used in chemical engineering applications.     

Surface Supported Gold–Organic Hybrids: On‐Surface Synthesis and Surface Directed Orientation

The surface‐assisted synthesis of gold–organic hybrids on Au (111) and Au (100) surfaces is repotred by thermally initiated dehalogenation of chloro‐substituted perylene‐3,4,9,10‐tetracarboxylic acid bisimides (PBIs). Structures and surface‐directed alignment of the Au–PBI chains are investigated by scanning tunnelling microscopy in ultra high vacuum conditions. Using dichloro‐PBI as a model system, the mechanism for the formation of Au–PBI dimer is revealed with scanning tunnelling microscopy studies and density functional theory calculations. A PBI radical generated from the homolytic C‐Cl bond dissociation can covalently bind a surface gold atom and partially pull it out of the surface to form stable PBI‐Au hybrid species, which also gives rise to the surface‐directed alignment of the Au–PBI chains on reconstructed Au (100) surfaces.     

Schmelzmetallurgische Beurteilung von nichteisen- metallh?ltigen Schlacken

The behaviour of different materials at increasing temperatures, especially the melting, is determinable by various methods. The information from technical literature, thermodynamical calculations by FactSage and practical measurements by a heating microscope are compared for the system Cr₂O₃?CFeO_x?CZnO, which is essential for EAF dusts. The results display that the technical literature provides only restricted information for inconvenient systems. The practical measurements are otherwise device-related limited by the maximum tolerable operating temperature (1700 °C). However, the obtained data exhibit the best reference to the industrial praxis. Finally, thermodynamical calculations are possible for any temperature. However, there are often no optimised thermodynamical data bases available for rather complex systems so that simplifications and assumptions are required. This possibly leads to increasing inaccuracy of the obtained results.     

Carbon‐Based Anodes for Lithium Sulfur Full Cells with High Cycle Stability

The lithium sulfur battery system has been studied since the late 1970s and has seen renewed interest in recent years. However, even after three decades of intensive research, prolonged cycling can only be achieved when a large excess of electrolyte and lithium is used. Here, for the first time, a balanced and stable lithium sulfur full cell is demonstrated with silicon–carbon as well as all‐carbon anodes. More than 1000 cycles, a specific capacity up to 1470 mAh g^?1 _sulfur (720 mAh g^?1 _cathode), and a high coulombic efficiency of over 99% even with a low amount of electrolyte are achieved. The alternative anodes do not suffer from electrolyte depletion, which is found to be the main cause of cell failure when using metallic lithium anodes.     

Aromatic amino acids as latent,bio-based curing agents and toughening agents for epoxy resins

In the realm of bio-based curing agents, recent investigations have focused on amino acids owing to their distinctive attributes. Nevertheless, the suitability of thermosets cured with aromatic amino acids as latent matrix materials for fiber-reinforced composites remains to be empirically established. Consequently, this study is oriented toward assessing the mechanical properties of diglycidyl ether of bisphenol A when cured with either L-tryptophan or L-tyrosine, in the presence of a latent, urea-based accelerator. The investigated properties include glass transition temperatures, tensile, flexural, compression, and fracture toughness properties. The predominant variations in the mechanical characteristics of these thermosets are confined to their Young's moduli and fracture toughness properties. This divergence is attributed to the greater presence of crystals in the L-tyrosine-cured thermoset, resulting in enhanced reinforcement and toughening effects compared to the L-tryptophan-cured thermoset.