A Study of Particle Rebounding Characteristics of a Gas–Particle Flow over a Curved Wall Surface

The particle rebounding characteristics of a gas–particle flow over a cylindrical body is investigated. With the aid of both computational and experimental approaches, the mean particle flow patterns, comprising both incident and rebound particles resulting from the impact of particles on a curved wall surface, are examined. In the experimental investigation, a two-dimensional Laser Doppler Anemometry (LDA) technique is used in the immediate vicinity of the body surface to measure the instantaneous incident and rebound particle velocities. The Reynolds-Averaging Navier-Stokes equations are solved for the continuum gas phase, and the results are used in conjunction with a Lagrangian trajectory model to predict the particle-rebound behavior in the immediate vicinity of the cylindrical wall. The computational observations, also confirmed through experiments, reveal a particle rebound zone where the mean particle flow pattern is significantly modified due to the contribution of the rebound particles during the process of particle–wall impact interaction. This particle rebound zone is found to be a function of mainly the Stokes number (particle inertia), and to a lesser extent on the fluid Reynolds number (gas flow condition), except for high gas flow velocities and restitution coefficients (particle-wall impact characteristics). Analysis of the effect of the above-mentioned parameters on the rebounding particle flow characteristics and their interrelationship has provided a better understanding of the behavior of particle flow impinging on a solid wall body. The beneficial contributions of the experimental and computational approaches in their ability to better quantify the particle–wall impact interaction phenomena present additional foundational investigations that could be further undertaken to better comprehend the particle behavior in curved wall surfaces. Such invaluable information has direct applications to industrial devices such as commercial heat exchangers and inertial impactors.     

Application of incomplete similarity theory for estimating maximum shear layer thickness of granular flows in rotating drums

Granular flow in a rotating drum provides a convenient system for investigating mixing, segregation and general properties of granular materials. This study is concerned with the maximum thickness of the flowing surface layer observed at the rolling regime. A scaling relation is first derived with the consideration of incomplete similarity associated with the drum-particle size ratio and the Froude number. Calibration is then carried out with published laboratory data, which were collected for the case of rotating drums half-filled with glass beads. The scaling relation is also compared with other kinds of datasets, showing good agreement and possibilities of the proposed approach to be further extended to more complex cases.     

A green catalyst for biodiesel production from jatropha oil: Optimization study

In this study, a simple and solvent-free method was used to prepare sulfated zirconia-alumina (SZA) catalyst. Its catalytic activity was subsequently investigated for the transesterification of Jatropha curcas L. oil to fatty acid methyl ester (FAME). The effects of catalyst preparation parameters on the yield of FAME were investigated using Design of Experiment (DOE). Results revealed that calcination temperature has a quadratic effect while calcination duration has a linear effect on the yield of FAME. Apart from that, interaction between both variables was also found to significantly affect the yield of FAME. At optimum condition; calcination temperature and calcination duration at 490 °C and 4 h, respectively, an optimum FAME yield of 78.2 wt% was obtained. Characterization with XRD, IR and BET were then used to verify the characteristic of SZA catalyst with those prepared using well established method and also to describe the catalyst characteristic with its activity.     

Heterogeneous catalysts for production of chemicals using carbon dioxide as raw material: A review

The utilization of CO₂ for the production of useful chemicals using heterogeneous catalysts is one of the ways to reduce the anthropogenic greenhouse gases in the atmosphere. In many cases, the CO₂ conversion and products yield are still considered very low and need to be operated at high pressure and temperature. The critical point in CO₂ conversion is to activate the CO₂ molecules either by adding a co-reactant or by using effective catalysts. This paper presents the current development on the effect of several precursors like metals, metal oxides, ionic liquids, and acid–base loaded on a suitable support in creating magical properties of catalysts on the performance of CO₂ conversion. Cu/ZnO-based catalysts, ionic liquid-based catalysts, and metal oxides-based catalysts are reported to be the most effective catalysts in the formation of methanol, cyclic carbonates and dimethyl carbonate. This review also focuses on various strategies and developments in altering heterogeneous catalysts, followed by critical factors of CO₂ molecule activation, and the optimization of the catalytic activity or catalysts reusability.     

Experimental Study on the Effect of Stabilization on Flow Boiling Heat Transfer in Microchannels

The effect of flow instabilities on flow boiling heat transfer in microchannels is investigated using water as the working fluid. The experimental test section has six parallel rectangular microchannels, each having a cross-sectional area of 1054 × 197 microns. Flow restrictors are introduced at the inlet of each microchannel to stabilize the flow boiling process and avoid the backflow phenomena. The mass flow rate, inlet temperature of water, and the electric current supplied to the resistive cartridge heater are controlled to provide quantitative heat transfer information. The results are compared with the unrestricted flow configuration.     

Characterization of different forms of vulcanized natural rubbers as elastomer spacer and toughening agent in two-matrix filled epoxy/natural rubber/graphene nano-platelets system

This paper compares the effects of different forms of vulcanized natural rubbers on the physical, mechanical, thermal, and electrical performances of filled epoxy systems. In this study, natural rubber (NR), liquid natural rubber (LNR), and recycled natural rubber (rNR) were introduced into filled epoxy systems. The results show that flexural strength, modulus, and toughness properties of filled epoxy system were enhanced with NR phases, as compared to those with LNR and rNR. Scanning electron micrograph revealed that the particle sizes of NR phases dispersed within epoxy matrix were smaller and more uniform, as compared to those with LNR and rNR phases. Incorporation of NR phases has improved the thermal stability of filled system, followed by LNR and rNR. This is attributed to more heat energy needed to overcome good interfacial bonding between epoxy matrix and small NR phases. X-ray diffraction analysis result showed that filled epoxy/NR/GNP system has higher 2θ values, indicated that d-spacing in between GNP nano-fillers has the closer distance. Electrical bulk conductivity values of filled epoxy/NR/GNP system were the highest. Small NR phases acted as elastomer spacers, which provided better “GNP packing efficiency” and realigned the GNP nano-fillers to form more effective conductive pathways for electrons hopping. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47188.     

Preparation and Characterization of CaO/CaSO4/Coal Fly Ash Sorbent for Sulfur Dioxide (SO2) Removal: Part I

A 2 level full factorial design of experiment was used to evaluate the significance of four sorbent preparation variables towards the structural properties of sorbent prepared from coal fly ash, calcium oxide (CaO) and calcium sulfate (CaSO₄) for flue gas desulfurization. The structural properties studied were BET specific surface area and average pore size of the sorbent while the experimental sorbent preparation variables studied were hydration period (x ₁), ratio of CaO to fly ash (x ₂), amount of CaSO₄ (x ₃), and drying temperature (x ₄). The surface area and average pore diameter of the sorbent obtained in this work range from 12.9 to 92.7 m²/g and 48.4 to 159.5 nm, respectively. The results revealed that there were significant influence of all the variables studied on the average pore diameter of the sorbent while only variables x ₁, x ₂, and x ₃ had significant influence on the surface area of the sorbent. X-ray diffraction (XRD) analysis revealed that the main phases detected in the sorbent was calcium alumino silicate hydrate compound. Scanning electron microscope (SEM) analysis showed that the sorbent consists of irregular shape particles that have a high structural porosity.     

Online Ensemble Modeling for Real Time Water Level Forecasts

Accurate and reliable flood forecasting is essential to mitigate the threats brought by floods. Ensemble approaches have been used in limited studies to improve the forecasts of component models. In this paper an ensemble model based on neural-fuzzy inference system (NFIS) and three real time updating approaches were used to synthesize the water level forecasts from a Adaptive-Network-based Fuzzy Inference System (ANFIS) model and the Unified River Basin Simulator (URBS) model for three stations in Lower Mekong. The NFIS ensemble model results are compared with the simple average model (SAM) which is adopted as a benchmark ensemble model. The ensemble model of offline learning without real time updating (EN-OFF), ensemble model with real time updating using offline learning (EN-RTOFF), ensemble model with real time updating using online learning (EN-RTON1) and ensemble model with real time updating using online learning and sub-models (EN-RTON2) were studied in this paper. Statistical analysis of the models for all the three stations indicated the superiority of the EN-RTON2 model over EN-RTOFF, EN-RTON1 models, SAM and the EN-OFF model. Not only the spikes in the URBS model were eliminated, but also the time shift problems in the ANFIS model results were decreased.