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In this paper, the minimum fluidisation velocity ( u m f ) of activated carbon particles in a gas–solid fluidised bed was experimentally determined using dry air as the fluidising medium. The effect of particle size and temperature on the minimum fluidisation velocity of the fluidised activated carbon particles was analysed. The particle sizes 212, 425, and 710 µm and bed temperatures of 30°C, 100°C, 200°C, and 300°C were studied. From the experimental results, it was found that the u m f decreased with a decrease in particle size of the activated carbon particles and decreased with an increase in the temperature. Based on the experimental results, a new correlation was developed to predict u m f at higher temperatures, since at higher temperatures, the deviation of experimental u m f values was higher when compared with the values estimated using previously published correlations. The present study will be useful for the design of an experimental system to study the continuous adsorption and desorption of organic vapours at higher temperatures in the fluidised bed of activated carbon particles. The details of the experimental study and analysis of results are discussed in this paper. [ABSTRACT FROM AUTHOR]

To design passive air-cooled heat exchangers, an experimental study on natural convection in a square or rectangular duct was felt necessary, as literature on this subject is not available. In the present study, experiments were carried out using a square duct of size 500 × 500 × 800 mm height fabricated with 3.0 mm thick aluminium sheet and a brass cylinder of diameter 25 mm and height 200 mm was used as internal heat source. The heated duct was cooled by natural circulation of air. A 3D Computational Fluid Dynamics (CFD) model for natural convection with variable properties of air and no-slip condition was developed. Laminar simulations of cooling of a vertical cylinder in a rectangular duct was obtained by solving the governing equations using Fluent 6.2.16 along with Gambit v4.6.0 as pre-processor for grid generation. Grid generation resulted in 23,800 cells with 24,185 nodes. Segregated solver solution methodology has been used for simulation with implicit linearization of the Equations (10–14). Finite volume or control volume discretization technique has been used with iterative solution techniques. Residual of the order offor momentum equation, laminar model andfor energy equation was used for convergence and stability check. The solver used was based on SIMPLE algorithm. Variation of density and viscosity of air with temperature were accounted for in the simulation. The model was validated by using experimental data. Average heat transfer coefficients were estimated. It was found that the theoretically calculated average heat transfer coefficients were in good agreement with the modelled values. [ABSTRACT FROM PUBLISHER]

Lithium-doped dysprosium oxide (LiDyO2) is a potential material for high-temperature applications of solid-state batteries. Experiments were conducted to synthesize LiDyO2by the solid-state reaction of lithium carbonate (Li2CO3) and dysprosium oxide (Dy2O3). The XRD pattern of the synthesized powder confirmed the formation of single-phase LiDyO2. From the TG-DTA study it was observed that the decomposition of Li2CO3starts at 740.9°C and the reaction between Li2CO3and Dy2O3starts at 750°C. The XRD analysis confirmed that mass loss observed in the TG-DTA study for the mixture of Li2CO3and Dy2O3at 750°C is due to the formation of LiDyO2. From the kinetic study it was found that the reaction of Li2CO3and Dy2O3follows nucleation mechanism. It was found that the best fitted model for reaction is the power law P4 nucleation model. Ozawa–Flynn–Wall method is the best suited method for fitting of the solid-state reaction model for reaction of Li2CO3and Dy2O3. The activation energy and pre-exponential factor for reaction of Li2CO3and Dy2O3were determined as 561–631 kJ/mol and 15.34–26.90 min−1, respectively. [ABSTRACT FROM PUBLISHER]

The fusion of deuterium and tritium is being considered for the energy source from fusion reactions, and on reaction each nuclei will produce one helium nuclei, one neutron and thermal energy. Deuterium is naturally available and the technologies to separate it from the compounds of hydrogen are well developed. Tritium can be produced by nuclear reaction of Li6isotope with thermal neutrons, and natural lithium contains about 7.5% Li6. Lithium has a low melting point and readily reacts with oxygen, nitrogen and moisture present in air. So, lithium-containing ceramics, namely lithium orthosilicate and lithium titanate enriched in Li6isotope, are being considered for tritium production by nuclear reaction with neutron. It was found that like lithium titanate, lithium orthosilicate can also be synthesised and pebbles can be fabricated by solid-state reaction process by using silica and lithium carbonate as raw materials. The advantage of this process is that the synthesis can be carried out at 800°C and fabricated pebbles can be sintered at 900°C to achieve the desired properties of the pebbles. Both these temperatures for synthesis and sintering are lower than that of the molten spray method. The experimental details and results are discussed in this paper. [ABSTRACT FROM PUBLISHER]

Lithium titanate (Li2TiO3) and lithium orthosilicate (Li4SiO4) are the promising solid breeder materials for the fusion reactors. Packed bed of Li2TiO3or Li4SiO4pebbles is considered in the fusion reactor blanket for in situ production of tritium and for this a good effective thermal conductivity of the pebble bed is necessary. In recent past, Mandalet al.[26] studied the hydrodynamics and heat transfer properties of bed of lithium titanate pebbles at different operating conditions viz., gas flow rates, pebble sizes, bed wall temperatures, etc. In the present study laminar,k – εand low Reynoldsk – εmodel have been used to simulate the hydrodynamics and heat transfer data of Li2TiO3pebble bed. The computational fluid dynamics (CFD)-simulated hydrodynamics results have been compared with hydrodynamics and heat transfer results of bed of Li2TiO3pebbles reported by Mandal et al. [26] and others. It was found thatk – εand low Reynolds numberk – εmodel shows better agreement with experimental results. The CFD study were carried out using low Reynoldsk – εmodel for pebble bed of different materials viz. Li2TiO3, Li4SiO4and alumina (Al2O3). The effect of flow rate, pebble size, wall temperature, solid properties viz. thermal conductivity and specific heat on effective thermal conductivity and overall heat transfer coefficient has been discussed in this paper. [ABSTRACT FROM AUTHOR]