Metal hydrides have garnered much interest in scientific and engineering communities since their discovery in 1866 because of the wide range of applications they offer [1, 2]. A comprehensive review of selected applications involving metal hydrides in engineering systems, processes and devices has been presented in this paper. The applications of metal hydrides can be broadly classified into seven distinct categories, which are: 1) thermal systems, 2) energy systems, 3) actuation and sensing, 4) processing, 5) semiconductors, 6) biomimetic and biomedical systems, and 7) nuclear applications in addition to hydrogen storage. There have been several brilliant reviews published on hydrogen storage in metal hydrides [118,. The focus of this review is on non-storage metal hydride applications. The fundamentals and working principles of engineering systems, processes, and devices based on metal hydrides have been concisely provided. Besides hydrogen storage, metal hydrides have been proposed and demonstrated for applications in hydrogen compressors, refrigerators, and actuators. Optical and electrical properties of hydrides can be exploited in the design of sensors and energy efficient windows. The hydriding and dehydriding processes are effective in preparing implants for osseointegration in addition to being economic. Certain hydride materials are more effective neutron moderators compared to the conventional ones in nuclear power plants. All such applications involving metal hydrides are revised and briefly discussed along with their working principles in this article.
a b s t r a c tIn recent years, advances in coating manufacturing processes have allowed wetting characteristics of a surface to be tuned with micro/nano morphologies. Today, complex surface geometries can be created with various surface treatment methods. These advances can be implemented in phase-change heattransfer applications, such as condensation, which relies on droplet behavior on a surface. Therefore, it is important to gain a fundamental understanding of wetting characteristics of textured surfaces having different geometrical configurations. This can be accomplished by studying the behavior of a single droplet on a given surface. Drop shapes and behaviors are affected by surface energies of different interfacial surfaces and surface morphologies. Contact angle hysteresis (CAH) -which is the difference between advancing and receding angles -can be estimated by utilizing concepts of surface-energy minimization. This is essential in heat transfer applications, as parameters such as drop size and distribution in condensation heat transfer are determined by CAH. In this study, a mathematical model has been developed to estimate CAH on different surface geometries and degrees of wetting. Modeling results suggest that CAH increases with increasing degree of wetting. Further, CAH remains low at both high and low droplet contact angles, whether the surface is hydrophilic or hydrophobic.
Nanocolloids (nanoparticle + solvent mixtures) and nanocolloid + non-adsorbing polymer mixtures arise in fields as diverse as pharmaceutics, hydrocarbon production, and environmental science. While there are many parallels with the phase behavior of molecular fluids, the driving forces for phase behavior, modeling approaches, and terminologies used to describe them differ markedly, reflecting historical examples and applications that underlie the development and understanding of phase diagrams in these fields. Here, for example, we link the concept of theta and non-theta solvent, in colloid phase diagrams, to upper critical end points arising in polymer + solvent binary mixtures in simple fluids by integrating concepts from both fields. We show that the phase behavior of silica nanoparticles (7 nm diameter) + polystyrene (237 kg/mol) + cyclohexane is qualitatively similar to the phase behavior of chemically separated Athabasca pentane asphaltenes and physically separated Athabasca retentate (comprising 43.1 wt % pentane asphaltenes) + atactic polystyrene (400 kg/mol) + toluene. All three mixtures exhibit two-phase regions, where one phase is enriched with polymer and the other phase is enriched with nanoparticles. The phase boundaries are reversible and include critical points, underscoring the overlap in particulate states in both phases. The experimental methods, phase boundaries, and fluid–fluid critical points are presented and discussed. X-ray transmission was found to be more robust than acoustic transmission for the identification of two-phase to one-phase boundaries and critical points for these mixtures. The outcomes of this work add to our understanding of the phase behavior of solvent + non-adsorbing polymer + nanoparticle mixtures for cases where dispersive energies are weak. More specifically, they improve our understanding of asphaltene and asphaltene-rich fluid behaviors in reservoirs and production, transport, and refining processes. We broaden the conceptual understanding of asphaltene behavior and underscore the importance of a colloidal approach for modeling asphaltene stability.
In the present work, a combination of silica sand and metallic sheets as a fixed bed media was used for carbon dioxide hydrate formation studies. Two metallic sheets, aluminum and brass, were incorporated into the fixed bed of silica sand to enhance heat transfer properties of the bed. The results obtained from this arrangement of metal sheets were compared with those obtained with a pure silica sand system. Both brass and aluminum systems were found to be good candidates to enhance gas hydrate formation kinetics compared to simply a sand system. Production of fuel gas from coal often contains a toxic gas, hydrogen sulfide (H 2 S). For the first time, the effect of H 2 S on the formation kinetics of CO 2 + H 2 + H 2 S hydrates has been studied. It was observed that the presence of H 2 S does not affect the hydrate formation kinetics and total gas uptake in the presence of H 2 S is either as good as CO 2 + H 2 hydrate or better. However, H 2 S impurity in the fuel gas mixture shows a corrosive effect on silica sand media.
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