A computational fluid dynamic model for evaluating the performance of crude oil gasification

Gasification is a clean technology which converts the liquid or solid fuels into a high caloric value syngas for power generation. In this research work, we developed a computational fluid dynamic model of crude oil gasification for hydrogen production; the accuracy of the model was approved in our previous work. Effects of some important factors such as residence time, steam/fuel ratio and equivalence ratio on hydrogen yield, and char conversion were explored. Results showed that the residence time and steam/fuel ratio play a major role in the process. It was also found that the equivalence ratio has a negative effect on the hydrogen yield and a positive effect on the char conversion.     

Detailed modeling study of low-velocity combustion of crude oil at different moisture content

The authors developed a kinetic model of crude oil combustion in different moisture contents and operating conditions by considering the reaction rates and fuel properties. To model the diffusion of gaseous products under high-temperature conditions, the authors used a binary diffusion equation that depends on the physical properties of fuel used and the reaction temperature. Results showed that the combustion of crude oil at higher moisture is not more favorable because of a considerable increase in greenhouse gas emissions, although an optimum condition for output temperature is obvious. It also found that the char conversion is higher for the high residence times. Model validated against the experimental data available in the literature, which showed fully good agreement.     

Design of a micro glass cell apparatus for pure gas‐nonvolatile liquid phase behaviour study

A micro syringe is used as a constant volume cell for gas–liquid equilibrium (GLE) study. The cell is made of glass and has a volume of <100 µL. It can operate at pressures up to 13 MPa and temperatures up to 115°C. Two different experimental procedures are presented for systems with nonvolatile low and high viscosity liquids. A micro magnetic stir bar is used to mix the gas–liquid mixtures inside the cell. Since the internal volume of the cell is small, a short mixing time is sufficient for the gas–liquid mixtures to reach equilibrium. The solubility values are measured by using the pressure decay method. The experimental procedures are validated by measuring the carbon dioxide (CO₂) solubility in water and highly viscous bitumen. The experimental results are in good agreement with the available literature data which shows that the technique works well. © 2011 Canadian Society for Chemical Engineering     

Numerical Simulation of Surfactant Flooding in Darcy Scale Flow

One of the methods that is used nowadays in enhanced oil recovery is surfactant flooding. The main mechanisms of surfactant flooding in reservoir consist of reduction of interfacial tension between water and oil and modification of rock wettability. In this study, the authors simulate the surfactant injection process in Darcy scale and in one-dimensional, multicomponent, multiphase state, and effects of physical phenomena such as adsorption, dispersion, convection, and exchange between fluids and solids are considered. Wettability alteration of reservoir rock due to presence of surfactant in injected fluid is detected in relative permeability and capillary pressure curves. First, the authors express the governing flow equations in the system and then discretize them. The variables consist of water and oil saturations, surfactant concentration in water phase, water and oil pressures, and velocities in each block. Second, the discretized equations are solved by IMPES method and pressure and saturation variables are calculated and after that, the concentration of surfactant in water phase is calculated. Finally, results of simulation are shown.     

Fluidized bed catalytic chemical vapor deposition synthesis of carbon nanotubes—A review

Carbon nanotubes (CNTs) are pure carbon in nanostructures with unique physico-chemical properties. They have brought significant breakthroughs in different fields such as materials, electronic devices, energy storage, separation, sensors, etc. If the CNTs are ever to fulfill their promise as an engineering material, commercial production will be required. Catalytic chemical vapor deposition (CCVD) technique coupled with a suitable reactor is considered as a scalable and relatively low-cost process enabling to produce high yield CNTs. Recent advances on CCVD of CNTs have shown that fluidized-bed reactors have a great potential for commercial production of this valuable material. However, the dominating process parameters which impact upon the CNT nucleation and growth need to be understood to control product morphology, optimize process productivity and scale up the process. This paper discusses a general overview of the key parameters in the CVD formation of CNT. The focus will be then shifted to the fluidized bed reactors as an alternative for commercial production of CNTs.     

Experimental Characterization of an Electrohydrodynamic Micropump for Cryogenic Spot Cooling Applications

This article presents a study on the characterization of a planar, multistage, electrohydrodynamic (EHD) ion-drag micropump for pumping of liquid nitrogen. Two designs of the pump, consisting of different emitter configurations (flat and saw-tooth), similar emitter-collector spacing (50 microns), and similar gaps between successive electrode pairs (100 microns), were tested at DC voltages ranging from 0 to 2.5 kV. The electric currents they generated and the corresponding static pressure heads were measured to characterize the pumping performance. Pressure and current onset voltages as well as pressure-voltage (P-V) and pressure-current (P-I) relationships were investigated. The highest pressure head (30 Pa at 1700 V) was generated with the saw-tooth design. After collecting and processing the data for various prototypes, it was evident that incorporating saw-tooth electrodes can significantly improve the performance of the micropump.     

Associative activation during interrupted task performance: a mixed methods approach to understanding the overall quality effects of interruptions

The objectives of this research were to (1) explore whether goal-activation models of procedurally based interrupted task performance can be applied to content production, and if not, (2) develop a new theoretical account, and (3) provide support for that theory. Experiment 1 found that interruptions during planning resulted in less developed plans, and that available theoretical models could not account for performance. Experiment 2 leveraged Verbal Protocol Analysis to explore the cognitive mechanisms underlying interrupted task performance on a content production task. We found support for a combination of processes: (1) cues and environmental context, and (2) task activation levels. These results suggested a spreading activation account of interrupted task performance. Experiment 3 provided further support for spreading activation by comparing short and long interruptions. These results have broad implications for moving our understanding of interrupted task performance forward by expanding our understanding to non-procedural task performance.     

Soft,Flexible Freestanding Neural Stimulation and Recording Electrodes Fabricated from Reduced Graphene Oxide

There is an urgent need for conductive neural interfacing materials that exhibit mechanically compliant properties, while also retaining high strength and durability under physiological conditions. Currently, implantable electrode systems designed to stimulate and record neural activity are composed of rigid materials such as crystalline silicon and noble metals. While these materials are strong and chemically stable, their intrinsic stiffness and density induce glial scarring and eventual loss of electrode function in vivo. Conductive composites, such as polymers and hydrogels, have excellent electrochemical and mechanical properties, but are electrodeposited onto rigid and dense metallic substrates. In the work described here, strong and conductive microfibers (40–50 μm diameter) wet‐spun from liquid crystalline dispersions of graphene oxide are fabricated into freestanding neural stimulation electrodes. The fibers are insulated with parylene‐C and laser‐treated, forming “brush” electrodes with diameters over 3.5 times that of the fiber shank. The fabrication method is fast, repeatable, and scalable for high‐density 3D array structures and does not require additional welding or attachment of larger electrodes to wires. The electrodes are characterized electrochemically and used to stimulate live retina in vitro. Additionally, the electrodes are coated in a water‐soluble sugar microneedle for implantation into, and subsequent recording from, visual cortex.