Annular Column Research Articles

Experimental and numerical investigation on the collapse of annular columns of dry granular matter

The collapse of a granular column confined in a vertical annulus is investigated through both experiments and DEM. During the collapse of column, an outward-moving avalanche and a unique shape of final deposit are commonly observed. In contrast, the present problem involves an inward granular avalanche towards the center of the annulus along with an outward avalanche. The final deposit profile has been categorized into four different cases involving single or double peaks and valley in between based on the aspect ratio. Apart from the mild effect of the coefficient of friction, no other particle properties influence the shape of the deposit. Removal speed of the confining walls strongly affects the speed of the avalanche but not the deposit shape. Scaling analyses show a power law dependence of runout distance on aspect ratio and a linear dependence of event duration on the free fall time of a grain.

Experimental and DEM simulations of the mechanical properties of rock under freeze–thaw cycles

The investigation of the physical-mechanical properties of rock after freeze–thaw (F-T) cycles has important theoretical significance for understanding freeze–thaw disaster mechanisms, disaster prediction, and tunnel protection system design in cold regions. Physical-mechanical tests are carried out to quantify the deterioration of the physical-mechanical properties of sandstone subjected to long-term F-T cycles. The damage mechanism of sandstone subject to F-T cycles is discussed based on scanning electron microscopy (SEM) results. A new three-dimensional discrete element method (DEM) model for simulating freeze–thaw damage of water-saturated rocks is established based on the volume expansion theory. In the new method, a one-dimensional thermal conduction equation is introduced to realistically simulate the distribution of the temperature field in a cylindrical sample during thermal conduction, and the evolution equation of ice volume expansion is introduced to control the volume expansion of ice particles in the sample as the freeze point. The crack development mechanism during the F-T cycle and the correlation between the cracks generated by the F-T cycle and subsequent loading are also analyzed. The results show that approximately 80% of the frost-heave cracks are distributed in the annular column area 10–25 mm from the axis of the sample. In the radial direction, there is a significant correlation between the formatting of cracks during F-T cycles and loading. In the axial direction, due to the relatively uniform distribution of F-T cracks, the formation of cracks under subsequent loading is mainly controlled by stress concentration.

Microalgae as an aquaculture feed produced in a short light-path annular column photobioreactor

In this work, four microalgae species (Chlorella vulgaris, Trachydiscus minutus, Monodopsis sp., and Monoraphidium sp.) were selected and grown in a novel, 30 L short-light path annular-column photobioreactor (AC-PBR). The aim was to test the microalgae growth on a pilot scale and evaluate the potential use as an alternative fish feed in hatcheries based on the content and composition of fatty acids. All microalgae species reached a high biomass density between 3.65 and 5.32 g DW L−1 during a 14-day trial. The highest growth rate of 0.25 ± 0.05 d−1 was calculated for Trachydiscus culture. The highest total content of fatty acids (TFA) was determined for Monodopsis and Trachydiscus biomass as the concentration reached 74.5 ± 6.3 and 72.4 ± 7.6 mg g−1 DW, respectively. These two species contained mostly eicosapentaenoic acid (EPA; C20:5n3), the crucial FA for carnivorous fish whose concentration reached the value of 25.3 ± 0.9% and 31.9 ± 2.0% of TFA for Monodopsis and Trachydiscus, respectively. A high amount of linoleic acid (LA; C18:2n6), another important FA for freshwater aquafeed, was found in Chlorella biomass up to the concentration of 21.9 ± 1.5% of TFA. The present results suggest the feasibility of in-house cultivation of selected microalgae species as a quality live feed source for fish hatcheries.

Wideband Polarization Agile Dielectric Resonator Antenna With Reconfigurable Broadside and Conical Beams

A new broadside and conical beam reconfigurable dielectric resonator antenna (DRA) with three orthogonal linear polarizations (LPs) and two orthogonal circular polarizations (CPs) agility is presented. It consists of a quad-strip-fed DRA element and a reconfigurable feeding network. First, the DRA element is designed to make unidirectional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm{HEM}}_{11 \delta }$ </tex-math></inline-formula> mode and omnidirectional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm{TM}}_{01 \delta }$ </tex-math></inline-formula> mode operate in the same wide band by tactfully removing a concentric annular column from its interior. Furthermore, a center-loaded metal post helps to improve the impedance matching of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mathrm{TM}}_{01 \delta }$ </tex-math></inline-formula> resonance significantly. Afterward, the switchable feed network is designed to implement diverse phase distributions of four output ports, i.e., providing the quad-port in-phase excitation, dual-port differential excitations, and quad-port sequentially rotated phase excitation strategies for a vertical LP, ±45° slant horizontal LPs, and two CPs, respectively. Finally, a fully functional prototype is designed, fabricated, and measured to validate the design. The measured results show that the overlapping impedance bandwidth of 36.8% for all the states and the axial-ratio bandwidth of 33.8% for the CPs are obtained.

Improved Method for Testing Integrity Loss of Wells with Sustained Casing Pressure

The pressure bleed-down/build-up (B/B) testing is enforced by the Bureau of Safty and Environmental Enforcement (BSEE) regulations in the US for gas-leaking wells with recurrent casing head annular pressure dubbed “Sustained Casing Pressure” (SCP). The bleed down test involves bleeding the pressure with a needle valve. Once the pressure reached to zero or stabilized, the valve is closedand a 24-h pressure monitoring starts. Analysis of the tests mandated by regulations involves merely a qualitative assessment of the low or high level of environmental risk measured by leak size. A quantitative analysis—based on mathematical models—has been already proposed and used for sizing cement leaks but the models give ambiguous results due to oversimplifying assumptions of the cement leak system and disregard for the testing procedure. This work addresses shortcomings of the current B/B testing and analysis methods by approaching the testing procedure as a source of useful information about the system of annular well leakage. We demonstrate that using a mathematical model for globally matching all stages of the B/B test data would prioritize the pressure bleed-down stage over the buildup stage thus making the latter stage mostly irrelevant in providing information on the whole gas migration system. We verify the hypothesis that a stage-wise analysis would improve the results by separately considering three stages of the B/B test: pressure bleed down, constant flow (steady-state), and pressure buildup, and, then, comparatively reconciling values of the system parameters. The stage-by-stage approach is feasible because—as shown by the sensitivity analysis—each stage is controlled mostly by a single parameter. Also presented is the development of an improved procedure for performing the B-B test. The study shows that the operational parameters controlled by the test operator—duration and size of the needle valve opening, and pressure recording time step, might significantly change values of the test output—the minimum bleed down, and the maximum 24-h buildup pressures. It is also found that the zero bleed-down pressure does not necessarily indicate that the leak is small as it also depends upon the length and properties of the annular fluid column above the cement top.

An annular porous column (5) aromatics as anode material for lithium-ion batteries

An annular porous column (5) aromatics as anode material for lithium-ion batteries

Energy efficient design through structural variations of complex heat-integrated azeotropic distillation of acetone-chloroform-water system

This study presents enhanced energy savings through structural variations of a heat-integrated distillation column for the separation of ternary azeotropic mixture. The conventional sequence has a decanter followed by pressure-swing distillation (PSD) columns for separating acetone-chloroform-water azeotropic mixture. Based on a significant temperature gradient of the PSD, a double annular column was proposed in order that the heat from hot fluid to cold fluid passed through the shared column wall. The heat transferred to the stages near the reboiler could replace the use of external utility, thereby reducing the total energy consumption of the process. For accurate calculations of heat transfer rate, the trays with the double annular structure were simulated by computational fluid dynamics. However, the energy saving was not effective since the structure could not afford to utilize all the heat transferred and additional energy was required to recover. The newly proposed (partial double annular) structure transferred heat from a high-pressure column to two low-pressure columns. It demonstrated 7,807.78 kW of the theoretical energy saving which was almost double of the heat transfer amount. Consequently, the total utility consumption and total annual cost was reduced by 21.79% and 11.32%, respectively, compared to the conventional sequence.

Efficient microalgae feed production for fish hatcheries using an annular column photobioreactor characterized by a short light path and central LED illumination

Efficient microalgae feed production for fish hatcheries using an annular column photobioreactor characterized by a short light path and central LED illumination

CFD-aided design of internally heat-integrated pressure-swing distillation for ternary azeotropic separation constrained by pinch pressure

• Novel HIPSD for separating an azeotropic ternary mixture is proposed. • An extended pinch-based method to determine the pressure of HIPSD is introduced. • HIPSD alternatives are generated for the given initial feed composition. • Practical heat transfer rates in HIPSD are determined by the CFD method. • Significant energy savings in HIPSD are achieved for ternary azeotropic separation. This study addresses computational fluid dynamics (CFD) for designing internally heat-integrated pressure-swing distillation (HIPSD) with improved energy efficiency in azeotropic distillation. An extended concept of pinch pressure is applied to determine the operating pressure of the HIPSD in a double annular column configuration for the circumvention of a distillation boundary and adequate heat transfer. For the separation of a highly azeotropic ternary mixture of butyl acetate, butanol, and water, the combination of a single unit of HIPSD and a decanter is employed. This azeotropic mixture is separated in different design alternatives for the given initial feed compositions. In each sequence, the heat transfer rate inside the HIPSD was calculated by the CFD method, and the total utility consumption accordingly decreased by 9.72% and 15.44%. The reboiler and condenser duty in the HIPSD were reduced by up to 48.65%. The separation efficiency in the condenser of the high-pressure column was improved enough to reach a zero reflux by the internal heat integration.

Computational Fluid Dynamics Applied to Study Coolant Loss Regimes in Very High Temperature Reactors

The nuclear energy is a good alternative to meet the continuous increase in world energy demand. In this pers-pective, VHTRs (Very High Temperature Reactors) are serious candidates for energy generation due to its inherently safe performance, low power density and high conversion efficiency. However, the viability of these reactors depends on an efficient safety system in the operation of nuclear plants. The HTR (High Temperature Reactor)-10 model, an experimental reactor of the pebble bed type, is used as a case study in this work to perform the thermohydraulic simulation. Due to the complex patterns flow that appear in the pebble bed reactor core CFD (Computational Fluid Dynamics) techniques are used to simulate these reactors. A realistic approach is adopted to simulate the central annular column of the reactor core. As geometrical model of the fuel elements was selected the BCC (Body Centered Cubic) arrangement. Parameters considered for reactor design are available in the technical report of benchmark issues by IAEA (TECDOC-1694). We obtain the temperature profile distribution in the core for regimes where the coolant flow rate is smaller than recommended in a normal operation. In general, the temperature distributions calculated are consistent with phenomenological behavior. Even without considering the reactivity changes to reduce the reactor power or other safety mechanisms, the maximum temperatures do not exceed the recommended limits for TRISO fuel elements.

Energy-Efficient Design of a Novel Double Annular Separation Column Using Pinch Pressure

This study introduces a pinch-based method to design an internally heat-integrated pressure swing distillation (HIPSD) with a double annular column. In the configuration, the annular stripping sect...

Improving the Bonding Strength of Nb–C/C Composite Brazed Structures by Preoxidation

Preoxidation treatment is used to modify the surface of C/C composite. An annular column gap is formed encasing the carbon fiber, which promotes the infiltration of C/C composite by liquid brazing alloy during brazing. Based on the optimized preoxidation condition of 800 °C/5 min, the effects of brazing temperature (860–940 °C) and holding time (5–20 min) on the microstructure and mechanical properties of Nb and C/C joints brazed with an AgCuTi alloy are systematically investigated. The shear strength of the brazed structure at 880 °C for 10 min reaches a maximum of 57 MPa, which is increased by 28 MPa compared with that of the structure without preoxidation. The infiltration depth, reaction layer thickness, Ti–Cu compound amount, and brazing seam width are characterized to reveal the synergistic effect of preoxidation and brazing parameters on the bonding strength of structures. The selection of an appropriate brazing parameter is conducive to maximizing the positive effects of preoxidation.

Erosion characteristics and stochastic nature of bed shear stress in underwater mine tailings

The erosion of mine tailings was investigated by examining the physical processes during the initiation of motion of the tailings. Erosion experiments were conducted on mine tailings samples and natural soils in a Plexiglas laboratory annular column under 50 cm water cover. Resuspension was introduced with a Teflon stirrer and the bed shear stress was estimated from the measured near-bed velocity field and the pressure change in the boundary layer. Two modes of initiation of motion of cohesive mine tailings that showed cohesive behaviour was noticed: pitting erosion and line erosion and the modes of initiation of motion changed mainly with percentage of fines. At incipient motion of the tailings that showed cohesive behaviour, the pore water pressure distribution showed a relative sudden peak and a decline when the aggregated tailings burst. A four order of magnitude difference was observed between the undrained shear strength and critical shear stress for surface erosion of the tailings. The stochastic nature of the bed shear stress was explained by the Rayleigh distribution that provides an approach for correcting the critical shear stress estimated from the near-bed velocity. This correction is necessary to achieve a conservative estimate of the critical shear stress for design purposes.

Nusselt correlation to predict heat transfer from an oscillated vertical annular fluid column through a porous domain

Experimental evaluation of the heat transfer in oscillating flow under the constant heat flux and constant amplitude fluid displacement conditions is presented for a vertical annular flow through a stainless steel wool porous media. The analysis is carried out for two different heat fluxes and for five different frequencies. The data is acquired from the measurements both in the initial transient period and in the pseudo-steady (cyclic) period by the system. The physical and mathematical behavior of the resulting Nusselt numbers are analyzed, according to data acquired from the experiments and in accordance with the results of the Buckingham Pi theorem. A cycle and space averaged Nusselt number correlation is suggested as a function of kinetic Reynolds number for oscillating flows. The suggested correlation is useful in predicting heat transfer from oscillating flows through highly porous and permeable solid media at low actuation frequencies and at low heat fluxes applied in the wall. The validity of the Nusselt numbers acquired by correlation is discussed using experimental Nusselt numbers for the selected kinetic Reynolds number interval. The present investigation has possible applications in moderate sized wicked heat pipes, solid matrix compact heat exchangers compromising of metallic foams, filtration equipment, and steam generators.

Annular Column Loaded Cylindrical Dielectric Resonator Antenna for Wideband Conical Radiation

A wideband cylindrical dielectric resonator antenna (CDRA)-loaded with an annular column, namely the LCDRA, is proposed and analyzed. The antenna comprises two components—an inner cylindrical dielectric and a loaded concentric column dielectric. The proposed antenna is centrally fed by a coaxial probe, and has a low profile of $0.175\;{\lambda _0}$ ( ${\lambda _0}$ is the wavelength of the center frequency). Four conical radiation pattern modes ( ${\text{TM}_{01\delta }},{\text{TM}_{02\delta }},{\text{TM}_{03\delta }},\;\text{and}\;{\text{TM}_{04\delta }}$ modes) are excited and merged, providing an impedance bandwidth of 56% (3.14–5.56 GHz). A prototype of the proposed antenna is built and tested. Good agreement between the simulated and measured results, including the reflection coefficient and radiation patterns, is achieved.

Experimental Investigation of Inverted Annular Film Boiling in a Rod Bundle during Reflood Transient

Heat transfer results for subcooled and saturated inverted annular film boiling (IAFB) obtained from a 7×7 rod bundle during transient reflood are presented in this paper. The test section consists of heater rods of 9.5-mm diameter and 12.6-mm pitch arranged in a square array. Flooding rates considered are 0.076 and 0.152 m/s, pressure varied from 138 to 414 kPa, and inlet subcooling up to 83 K. Evaluation of the data includes estimation of the local void fraction and Nusselt number during IAFB as well as in the inverted slug film boiling (ISFB) regime, which occurs when the inverted annular liquid column disintegrates. Experimental heat transfer results are compared with several film boiling models, and a new correlation for the Nusselt number is proposed for the IAFB and ISFB regimes. Predicted Nusselt numbers using the new correlation deviate from the experimental data by an average error of 15% and root-mean-square error of ∼30%.

Photocatalytic Degradation of p‐Nitrophenol in an Annular Column Photoreactor and the Intermediates

The photocatalytic degradation of p-nitrophenol using a titanium dioxide suspension was studied in an annular column photoreactor operating in batch recycle mode with an aerated reservoir tank. The dependency of the process efficiency on the initial PNP concentration was quantitatively defined using an exponential function. The degradation rate was highest at pH 7-7.2. The appearance of p-benzoquinone, p-hydroquinone, and phenol during the degradation process was confirmed by high-performance liquid chromatography analysis. The formation of similar intermediates during the microbial degradation of PNP has been reported previously. The formation of hydroxyl. radicals is predominant in the PNP photodegradation route, and fluctuations of the chemical oxygen demand may be indicative of the appearance of unidentified and probably nonbiodegradable intermediates formed during photocatalysis. These compounds likely contribute to the COD variations. Herein, the results of PNP removal via photocatalytic degradative reactions are discussed, and the intermediates are compared to those observed in enzymatic reactions.

Effect of Rotary Partition DPF Structure on its Regeneration Characteristics with Microwave

The energy that traditional diesel particulate filter (DPF) regeneration with microwave requires in regeneration process often exceeds the capacity of the vehicle's battery, a rotary partition regenerative DPF with microwave is proposed recently, which was a annular column consisting of the fan-shaped filter units. A filtration unit microwave heating regeneration model was established aiming at this DPF, to study the regenerative properties of the filtration unit and to get influence that its shape structure plays on reproduction characteristics. The results show that: the central angle, length to diameter ratio, the ratio of inner and outer diameter of the DPF all have larger impact on the regeneration. The results can provide theoretical basis and reference for practical development of the new DPF.

Fiber-Optic Sucrose Sensor Based on Mode-Filtered Light Detection

A mode-filtered light fiber-optic sucrose sensor was constructed from an annular column consisting of a bare optical fiber inserted into a capillary tube. A series of standard solutions with different concentrations of sucrose were measured by the sensor. The response range of the sucrose solution is 0%–60% (w/w). A linear relationship was found between the strength of the mode-filtered light and the sucrose concentration, with a correlation coefficient of 0.9994. The sensor exhibits good reproducibility and reversibility, as well as good standardized recovery for real samples. Thus, a real-time, fast, and sensitive determination method for sucrose concentration has been established.

Safe Drillpipe Connections During Managed-Pressure-Drilling Operations

This article, written by Senior Technology Editor Dennis Denney, contains highlights of paper SPE 147278, ’Field Demonstration of a New Method for Making Drillpipe Connections During Managed-Pressure-Drilling Operations,’ by Rachel Johnson, Halliburton; Julio Montilva, SPE, Shell; Mohamed Sati, Jeff Grable, and Saad Saeed, SPE, Halliburton; and Richard Billa and William Derise, Shell, prepared for the 2011 SPE Annual Technical Conference and Exhibition, Denver, 30 October- 2 November. The paper has not been peer reviewed. Managed-pressure drilling (MPD) is effective for controlling equivalent circulating density (ECD). However, making a drillpipe connection with MPD is more challenging than with conventional drilling. A method was developed for smoothly diverting rig-pump flow during connections from the standpipe to the MPD pressure-control equipment at the annulus by use of a valve manifold with an onboard choke. This method can improve pressure control and increase the operating range of MPD to provide higher pressures during connections and greater drilling flow rates. Introduction The use of MPD enables accurate, precise, and dynamic bottomhole-pressure (BHP) control. Current MPD technology incorporates automated-choke (auto-choke) systems coupled with real-time hydraulics models to provide engineered control within set limits. However, there is a common misperception that current MPD systems can provide the same consistent level of accuracy and precision in all phases of drilling. The most-accurate control usually is attained only in limited technical windows, such as the on-bottom drilling phase in which steady-state conditions enable more-accurate evaluation and prediction. All MPD systems have struggled with periods in a drilling operation that usually involve a variety of transient (startup/shutdown) behaviors. The most significant is the drillpipe-connection phase. Because of the regular frequency and highly dynamic nature of making connections, effects on the BHP can be significant, and if not managed effectively, they can negate the benefits achieved by MPD. In the worst case, they can lead to unintentional induced kicks. The rig-pump diverter (RPD) addresses this problem directly and provides an improved level of control and efficiency on connections. Background The BHP (downhole pressure at a datum) consists primarily of hydrostatic pressure of the annular mud column; frictional pressure loss (or dynamic pressure) that may be affected by flow rates, fluid rheologies, pipe movements, or geometric restrictions; and applied surface pressure (backpressure) at the annulus returns line. Automated MPD technology actively manipulates the applied surface pressure by means of the autochoke to control the BHP within a desired range. This control relies on a continuous stable pressure source. While drilling, this source is the rig pumps and it is throttled by the autochokes to apply the desired surface pressure. The challenge arises when the rig pumps are switched off, as in the case of connections. During this scenario, the loss of rig pumps equates to loss of frictional (or dynamic) pressure, which in turn causes a reduction of BHP (if not managed properly). The aim of MPD technology is to maintain a constant BHP by increasing the surface pressure proportionally, accounting for the lost dynamic pressure. Without a pressure source, increased surface pressure can be achieved only by pressure-trapping techniques. Several alternative schemes have been used to remedy this problem, with the most popular providing an alternative pressure source (on the annulus) that is used to drive the autochoke (in the absence of rig flow rate) and, in turn, apply the required surface pressure.