INFLUENCE OF DRYING CONDITIONS ON THE FRAGILITY OF CORN KERNELS

A dynamic rcsring dnim war built to study the effects of air temperature, moisture content and grain shape on fragility of the air dried kernels. For drying rares under 0.05 kglkg min. the fragility of kernels could br described empirically as a function of the three experimental parameters.     

STEAM DRYING TECHNOLOGIES: JAPANESE R&D

This report reviews some fundamental and practical aspects of steam drying technologies based mainly on studies published in Japan. Steam drying kinetics, and some industrial technologies particularly for drying of foods, textiles and sludges are reviewed with focus on quality of dried material, drying time, dryer selection and energy recovery from steam dryer exhaust. For energy recovery, heat pump technologies are outlined along with characteristics of different types of steam compressors. A new process is proposed for steam drying; it combines a direct-indirect dryer followed by a direct steam dryer for internal moisture removal.     

Comparison and Identification of Static Electrical Terminal Fuel Cell Models

Six steady-state fuel cell electrical terminal models are compared using experimental data from an Avista Laboratories SR-12 500 W proton exchange membrane (PEM) fuel cell. The paper begins by reviewing the physical effects in a fuel cell. The proposed electrical terminal models are introduced in terms of these physical effects, parameterized for identification and compared using the measured data.     

Moisture Distribution and Dewatering Efficiency for Wet Materials

This review paper summarizes current research efforts toward a comprehensive view of wet material dewatering, considering the binding energy as the strength to hold water, and rupture energy given to remove moisture from materials.     

Hardness and Fracture Toughness of SiC-Particle-Reinforced MoSi2 Composites

The indentation technique has been used to evaluate the hardness and fracture toughness of SiC-reinforced MoSi₂ composites made by hot-pressing. It is seen that the toughness increases with increasing indentation crack length (under increasing load) and a probable mechanism responsible for this behavior is described. It is also observed that there is an optimum volume fraction of SiC particles for which the maximum fracture toughness of the composite can be achieved.     

The effect of yttrium and thorium on the oxidation behavior of Ni-Cr-Al alloys

The effect of quaternary additions of 0.5% Y and 0.5 and 1.0% Th to a base alloy of Ni-10Cr-5Al on the oxidation behavior and mechanism was studied during oxidation in air over the range of 1000–1200°C. The presence of yttrium decreased the oxidation kinetics slightly, whereas the addition of thorium caused a slight increase. Oxide scale adherence was markedly improved by the addition of the quaternary elements. Although a number of oxides formed on yttrium-containing alloys, quantitative x-ray diffraction clearly showed that the rate-controlling step was the diffusion of oxygen through short-circuit paths in a thin layer of alumina that formed parabolically with time. Mixed oxides containing both aluminum and yttrium formed by the reaction of Y₂O₃ to form YAlOP₃ initially, and Y₃Al₅O₁₂ (YAG) after longer times. Although the scale adherence of the yttrium-containing alloy was considerably better than the base alloys, spalling did occur that was attributed to the formation of the voluminous YAG particles that grew in a mushroom-like manner, lifting the protective scale off the substrate locally. The YAG particles formed primarily at grain boundaries in the substrate in which the yttrium originally existed as YNi₉. This intermetallic compound reacted to form Y₂O₃, liberating metallic nickel that subsequently reacted to form NiO or NiAl₂O₄ spinel or both. The Y₂O₃ reacted with aluminum to ultimately form the YAG mushrooms. Thorium did not form any mixed oxides; the only oxide involving thorium was ThO₂, which existed as small particles at the oxide-metal interface. A highly beneficial effect of the thoria particles in reducing film spalling was observed. Scale spalling in the base alloy was attributed to void formation at the oxide-metal interface, the voids forming by condensation of excess vacancies from the Kirkendall effect associated with fast back-diffusion, of nickel into the substrate as aluminum was preferentially oxidized and diffused slowly outward. The mechanism of improved scale adherence in the quaternary alloys was the elimination of voids by annihilation of the Kirkendall vacancies at vacancy sinks introduced by the noncoherent interfaces between yttrium and thorium-containing intermetallics or oxides or both.This work is based on a portion of the dissertation of Arun Kumar in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Engineering, University of California, Los Angeles.Supported by NASA-Ames under grant No. NGR 05-007-352.