C/C-SiC component for metallic phase change materials

Thanks to their high energy density and thermal conductivity, metallic Phase Change Materials (mPCM) have shown great potential to improve the performance of thermal energy storage systems. However, the commercial application of mPCM is still limited due to their corrosion behavior with conventional container materials. This work first addresses on a fundamental level, whether carbon-based composite-ceramics are suitable for corrosion critical components in a thermal storage system. The compatibility between the mPCM AlSi₁₂ and the Liquid Silicon Infiltration (LSI)-based carbon fiber reinforced silicon carbide (C/C-SiC) composite is then investigated via contact angle measurements, microstructure analysis, and mechanical testing after exposure. The results reveal that the C/C-SiC composite maintains its mechanical properties and microstructure after exposure in the strongly corrosive mPCM. Based on these results, efforts were made to design and manufacture a container out of C/C-SiC for the housing of mPCM in vehicle application. The stability of the component filled with mPCM was proven nondestructively via computer tomography (CT). Successful thermal input- and output as well as thermal storage ability were demonstrated using a system calorimeter under conditions similar to the application. The investigated C/C-SiC composite has significant application potential as a structural material for thermal energy storage systems with mPCM.     

Heat/mass transfer from a neutrally buoyant sphere by mixed natural and forced convection in a simple shear flow

Building on the work of Yang et al. in 2011, the finite difference method and the Boussinesq approximation were applied to solve the time‐dependent Navier‐Stokes, convection diffusion and continuity equations in spherical coordinates. An idealized condition, the mass transfer from a neutrally buoyant sphere in a horizontal simple shear flow with natural convection was numerically simulated for the first time in this work. In the hybrid transfer case, the outwardly spiraling streamlines enhanced the transfer process, but the counter‐gravity spiraling streamlines near the sphere hindered the natural convection and the spatial dilution action weakened the natural convection transfer process. These competing effects led to nonmonotonic behavior of the Nusselt number with Reynolds number. Results from these previously undocumented cases were summarized into correlations for predicting Nusselt numbers at finite Reynolds numbers for various Grashof and Prandtl numbers. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2816–2827, 2018     

Determining profits for solar energy with remote sensing data

The objects of the article are to determine the profits for solar energy integrating remote sensing data: the optimal locations of photovoltaic and the base price of electricity resulting from solar energy. An illustrated experiment with five European countries data sets is taken. Results indicate that Germany is the only optimal region to set up photovoltaic so as to satisfy the electricity demand of the five considered. Results also show that solar energy is a promising energy source since the highest base price of electricity resulting from solar energy is only 0.35 $/kWh. The base electricity price for Germany is the lowest whereas the base electricity price for Italy is the highest. Moreover, the results further indicate that the photovoltaic module price plays a key role in determining the best appropriate region(s) to install photovoltaic and the base electricity price.     

Spatial distributions of O2, CO2 and SO2 in a pilot-scale fluidized bed combustor operated with different coals

Axial concentration profiles of O₂, CO₂ and SO₂ have been measured at different radial positions in a coal-fired fluidized bed combustor. The profiles show some spatial inhomogeneity in the bed, the degree of which depends on fluidizing velocity and amount of excess air. Comparison of SO₂- with CO₂-concentration profiles reveals that SO₂ is formed in proportion to CO₂ only with anthracite as fuel. With bituminous coals, SO₂ is preferentially formed near the coal feed point. These results are discussed with regard to characteristic times of mixing and chemical reaction in fluidized beds, and SO₂-formation characteristics of the employed coals obtained in a thermobalance.     

MgAl2O4-Spinel Synthesized by High-Energy Ball Milling and Reaction Sintering

A new way to prepare magnesia-alumina-spinel was investigated making use of a mixed powder system of MgO and metallic Al-3 wt% Mg. Intensive ball milling was applied which provides the formation of new powder particles as composite of both components in intimate contact. The new configuration of the particles had a significant impact on the reaction sintering behavior leading to single phase spinel microstructures at moderate temperatures below 1400°C. Optimized milling of the powder mixture was therefore required providing reduced crystallite sizes and strongly enlarged interfacial area shared by the reacting components. The optimal milling time was identified by the complete reaction of the starting powders to spinel during sintering. Shorter milling times led to incomplete reactions and longer milling times contaminated the milling product by debris from the milling tools. The amount of interfaces generated by the intimate mixing dominated the sintering reaction kinetics whereas the specific surfaces area was of secondary importance.     

Hygienic significance of patulin in food. 2. Occurrence of patulin in fruit and vegetables]

The analyses of more than 200 samples of various foods of plant origin showed that patulin was contained in 36% of the fresh and canned fruits infested with mould, and in 7% of the vegetables. Besides apples, pears, plums, peaches and tomatoes contained also patulin. In organoleptically impeccable fruit juices, the contamination rates were 40% (for apple juice) and 16% (for the other juices, such as sour cherry, currant, sea buckthorn juices). The patulin content varied from 20 to 200 microgram/l, the mean value being 80 microgram/l. It ranged from 0.1 to 5 microgram/g in apples and sterile apple preserves. The authors discuss the hygienic-toxicologic significance of these findings, and suggest to include patulin in the examination of foods for mycotoxins, stipulating a permissible value.     

New Industrial Products from Starch

The industrial (non-food) use of starch and starch-based products as renewable raw materials is discussed together with examples, in the following application areas:

• –Starch as auxiliary raw material: binder, adhesive, thickener, protective colloid.
• –Starch as raw material for new products in chemical or biotechnical processes: polyols, acids, polysaccharides, enzymes.
• –Starch as filler with specific functionality for synthetic polymers to improve application properties in e. g. polyethylene, polypropylene, polystyrene, polyurethane-foams, styrene/butadiene copolymers, polyvinylchloride.
• –Starch as reactive component to be incorporated during production of synthetic polymers leading to synergistic effects: urea/formaldehyde resins, phenolic resins, alkyd- and melamine resins.
• –Starch-based active materials which either exhibit direct functionality themselves, (e. g. as surfactants, sequestrants and bleaching boosters) or which represent building blocks for the synthesis of chiral compounds for the pharmaceutical or the agro-industries.

     

New Carbohydrate Derivatives from Biotechnical and Chemical Processes

Starch, its derivatives and hydrolysis products are well established as industrial products for the food and technical industries. More advanced products, based on starch, are available today, manufactured by biotechnical and chemical processes. They comprise a variety of monomeric compounds like polyols, hydroxycarboxylic acids, glycosides and their derivatives obtained by esterification, etherification and amination. In addition, interesting oligomeric and polymeric products are accessible, based on starch and its derivatives. Selected examples of these products are described as well as their respective production methods. For some products the chemicals synthesis will be compared with the fermentation route, analysing the relative advantages and disadvantages of both. The wide application potential of these “new” products is illustrated with reference to their use in different industries, e. g. in the manufacturing and processing of resins, polymers, detergents, cosmetics, pharmaceuticals and processed foods. Special emphasis will be given to the structural peculiarities of these carbohydrate derivatives, for example chirality, which enables them to act as unique intermediates in the production of biologically active products.     

Multisensor approach to determine changes of wetland characteristics in semiarid environments (central Spain)

Saline wetlands in the semiarid environment of Central Spain are fragile and highly dynamic ecosystems that are affected by degradation processes as a result of anthropological influences. An increase in agricultural production has led to the development of large-scale irrigation schemes with overexploitation of groundwater, and with consequent effects on the complex hydrology and associated land use. In this work, data from field, hyperspectral airborne, and multispectral satellite sensors are used in order to determine changes of wetland characteristics over time. The spectra of surface components (soil, vegetation, and salt crusts) were selected from the hyperspectral data and identified as endmembers using a site-specific spectral library. The spectral information contained in these endmembers was extrapolated to a temporal series of broadband multispectral imagery on which spectral unmixing analysis was performed in order to detect changes in the wetland over time. Results showed that the selected wetland components have undergone important changes in both their total area as well as their spatial distribution. These changes are mainly associated with the anthropogenic impact; however, natural influences due to seasonal fluctuations may coincide with the overall changes, although this in general is difficult to determine. Water regulation and agricultural practices directly influence the salinity of the soils and therefore the nature of the hygrophytic vegetation.