Spatio-Temporal Evolution Model of the Hydraulic Transport Characteristics of Particulate Solids

The hydraulic transport of solid materials is widely used in various industrial fields owing to its high efficiency, low cost, and environmental friendliness, and it has received extensive attention. However, the violent interaction between the liquid and solid phases during transportation makes the slurry flow strongly unsteady and heterogeneous, and it is difficult to use the existing mathematical models describing the motion characteristics in the hydraulic transport of slurry because of the limitations of a single theory or experimental data basis. In this study, considering the randomness and uncertainty in the transportation of solids, a spatio-temporal evolution model of the hydraulic transport characteristics of particulate solids was established. This model is suitable for hydraulic transport in pressure pipelines and open channels, and it can be used to analyze the influence of changes in the motion and property parameters of the liquid–solid phase on the characteristics of the temporal-spatial evolution of the slurry velocity and concentration distributions. The rationality of the model was verified through laboratory experiments. Through an interaction analysis of slurry components, this work explores the influence of the transport of solids on the slurry motion and property parameters, fills the gap in the evolution mechanism of the slurry velocity and concentration distributions in existing models, and overcomes the limitation that layer-based models can only be used in pressure pipelines. Therefore, it has important guiding significance for the engineering design of particulate solid hydraulic transport.

Comparative Study of Physical Models for Particle Sedimentation Using Simmer Code

In the context of improved safety requirements for Generation IV Sodium-cooled Fast Reactors (SFR), an innovative severe accident mitigation scenario is being investigated. In the French frame of SFR research, the mitigation strategy consists of transfer tubes and a core catcher. The transfer tubes are dedicated to discharge molten fissile materials from the core center region and to guide them towards the core catcher where long-term cooling and sub-critical state may be assured. The physical phenomena occurring during the discharge process are introduced in this paper. The current demonstration of the mitigation strategy uses best-estimate calculations with the reference computer code SIMMER. Previous analyses showed that the material discharge through the transfer tubes might be efficient however, uncertainties of SIMMER approach are identified on the molten material mobility during the relocation process. It is related to a blockage formation due to particulate solid debris accumulation inside the transfer tube, in case of low energy accumulation in the degraded fuel, is believed to originate from the solid particle treatment in the code. As the performance of mitigation strategy strongly depends on the mobility of the relocating mixture, the most predictive behavior of particle flows is of great importance to SFR safety. Therefore, the SIMMER modelling of such flows is analyzed in this work. The first verification and validation test cases regarding the gravitational settling of particle clouds at different volume fractions are presented. Recommendations for reactor calculations and first orientations for future research and development are highlighted.

Type and concentration effects of particulate solid lubricants on the microstructure, friction, and wear of electrodeposited Ni composite coatings

Nickel–MoS2 composite coatings were obtained by electrodeposition from a nickel electrolyte containing suspended MoS2 particles. The coating composition, morphology, crystalline structure, microhardness, and frictional behavior were studied as a function of MoS2 concentration. The results obtained in this study revealed that the codeposited lubricant particles strongly influenced the composite nickel coating properties. It was found that increasing codeposited MoS2 decreases the average grain size of nickel crystallites and leads to the formation of clusters which, in turn, lead to rough coatings with a high and variable thickness. The results of tribological response indicated that the reduction of friction coefficient and the improvement of wear resistance were performed until an optimal value of MoS2 concentration, which provided the best condition that promoted the tribo-layer stability and maintained the matrix integrity. A comparison of tribological and micromechanical properties between the coating containing the optimal fraction of MoS2 particles and the coating containing nearly the same fraction of graphite particles has been undertaken. Unlike the case of the addition of graphite particles, the microhardness of composite coating has been enhanced with the incorporation of MoS2 particles. However, the incorporation of graphite particles in the coating induced more effective lubrication and wear resistance.

Mechanical and thermal segregation of milli-beads during contact heating in a rotary drum. DEM modeling and simulation.

The flow mechanics and heat transfer phenomena within a bed of milli-metric size spherical beads rotated and heated by contact in a horizontal drum were simulated by means of commercial discrete element software EDEM. Mono-dispersed and bi-dispersed beds (two particle sizes or two particle densities) were considered. The mechanical segregation index (standard deviation of local bed compositions) and the thermal segregation index (standard deviation of beads temperatures) were calculated for the different types of bed and same operating conditions. The thermal segregation was found to be enhanced by mechanical segregation and was much stronger for bi-dispersed beds than for monodispersed one. Keywords: rotating drum; particulate solid; segregation; contact heat transfer; DEM simulation.

Particulate photocathode composed of (ZnSe)0.85(CuIn0.7Ga0.3Se2)0.15 synthesized with Na2S for enhanced sunlight-driven hydrogen evolution

A particulate solid solution, (ZnSe)0.85(CuIn0.7Ga0.3Se2)0.15, was synthesized by the flux method using various amounts of a Cu precursor (to make Cu-deficient, stoichiometric, or Cu-excess specimens) and/or a Na2S additive, to assess the effects of synthesis conditions on photoelectrochemical (PEC) properties.

Propiedades físicas de naranja agria cocristalizada: efecto del pH, sólidos solubles y zumo adicionado

The aim of this study was to evaluate the conditions of co-crystallization of bitter orange juice with sucrose on the physicochemical properties of the product. Bitter orange juice was obtained with a mechanical juicer and concentrated on a rotary evaporator. Sucrose syrup 70 oBrix was subjected to heating and stirring of 1000 rpm, until a white color (118 °C) was observed. Bitter orange juice was added to the syrup, and the mixture was subjected to constant stirring of 600 rpm, to observe the formation of a particulate solid material. The co-crystals were dried, grinded and sieved. A dry co-crystal was determined: moisture, bulk density, solubility, water activity and repose angle. High proportion of bitter orange juice added (20%) and low content of soluble solids (50 °Brix) produced co-crystals with low moisture content (2.59%), water activity (0.52) and solubility time (69.4 s). High pH (4.5) of bitter orange juice concentrate produced co-crystals with low moisture contents (1.96%). The co-crystals of bitter orange juice showed good reconstitution characteristics (high solubility); however, these had high humidity (2.5 to 4.5%) and water activity (0.508 to 0.798).