Cavity Zone Research Articles

Analysis of droplet motion in cavity zone of rotating packed bed

Droplet motion in outer cavity zone of rotating packed bed is a complex phenomenon that requires analysis of liquid and gas flow to clarify influences of factors such as rotation speed, liquid flow rate, or gas flow rate. In this study, hydrodynamics is described using laser Doppler velocimetry and high-resolution visualization for droplet motion characterization. The results reveal that droplet motion initially depends on the peripheral velocity of the packing, while further from the packing, it loses kinetic energy mainly due to the drag force caused by the surrounding gas. Two-way coupling is investigated as both phases interact with each other. Rankine vortex theory is applied to simulate gas flow in the outer cavity zone. A model, based on Newton’s second law, is developed to predict droplet dynamics, including impingement velocity, trajectory length, and total residence time. Validation of the model shows that it can predict the liquid velocity in the outer cavity zone accurately. Upon impingement of droplets on the casing, part of the liquid rebounds as secondary droplets into the cavity, where they circulate with the gas flow. Overall, this study provides insights into droplet dynamics in the rotating packed bed and offers a basis for optimizing process efficiency and design in various applications, including chemical processing and environmental engineering.

EVALUATION OF SURFACE DETERIORATION RESULTING FROM THERMAL FATIGUE IN THE OPERATIONAL STATE OF AN H13 PRESSURE DIE CASTING DIE

The failure rate of pressure die casting dies is increasing due to cracks on the die surfaces, leading to thermal fatigue and fracture. This paper aims to investigate the thermal fatigue failure of H13 die-casting die in running conditions by measuring the surface crack dimensions at core and cavity zones of the die during regular intervals of the die-casting process. The effect of length and width of the cracks on the die surface concerning coolant channel positions was analyzed. Transient thermal analysis was performed to investigate the temperature distribution, principal stress and total deformation of the die concerning to the coolant channel position using ANSYS. The maximum deformation of core insert was 0.0094 mm. Zone C of the core insert, which was 223.52 mm from the coolant channel location and corresponding to 139,237 cycles, had the longest crack, measuring 18.98 mm. Owing to greater temperature gradients, Zone Z of the cavity insert, which is situated 76.25 mm from the coolant channel, had the largest crack width, measuring 0.29 mm. The durability of the die casting die obtained from the numerical model (2.8×105 cycles) was in agreement with experimental studies (2.89×105 cycles).

Reliability aspects in repulsive steric hindrance approach: Selectivity and sensitivity investigations

Dual metal regulated bottom gate top contact structured Organic Thin Film Transistor based biosensor (Bio-OTFT) for recognition of breast cancer cell lines along with the non-tumorigenic epithelial cell line is presented here. A feasible fabrication scheme for Bio-OTFT has been demonstrated. Repulsive steric hindrance (RSH) consideration inside the cavity zone directs more practical and realistic sensing mechanisms. The insightful electrostatic analysis regarding electric field, energy band diagram, transfer characteristics (IDS-VGS), and transconductance (gm) has been described. Alteration of the dielectric constant (k) of these cancerous and healthy cell lines stated the recognition scheme in this reported Bio-OTFT. The efficiency of the recommended model has been assessed thoroughly with the reported OTFT literatures. The sensitivity is examined respecting drain current (IDS) in (A/μm), gm in (μS/μm), threshold voltage (VTH) in Voltage and sub-threshold swing (SS) in (mV/dec) and reaches to the maximum value of 2.3 × 108, 1.85 × 1010, 0.68, and 0.08 for T-47D cell line at VGS = −1.25 V. The recommended model thus suggests an enormous reliability and possibility for biosensing purposes.

Study on the strain response of slopes containing cavities under the effect of strong earthquakes

AbstractThe weak points in a slope often control its deformation and failure mode. Under the action of earthquakes, the complex influence of seismic waves on slopes with cavities is rarely considered. By studying the strain response of this kind of slope, the triggering mechanism of the slope under a strong earthquake can be further discussed. On the basis of the existing research, a shaking table test of a slope model with a cavity structure is carried out. The following conclusions were made: (1) Under the condition of a strong earthquake, the initial crack of the slope with cavities mainly occurs around the cavities, the top of the slope, and the boundary of the slope. (2) During the vibration process, the peak air pressure in a cavity has a good correlation with the peak strain in the surrounding material. The peak strain appears just after the peak air pressure, indicating that the sudden change in the air pressure in the cavity will lead to significant tensile damage to the cavity wall. Repeated air pressure changes in the cavity cause progressive damage to the slope near the cavity structure, accelerating fracture expansion and leading to the fracture penetrating the slope boundary. (3) The overall failure of the slope is somewhat related to the development of cracks around the cavity structure, but failure does not necessarily occur along the cavity zone. The failure site is closely related to the free surface condition and the upper slope structure.

A porous medium approach to the 3D modelling of an entire rotating packed bed for post-combustion carbon capture

Rotating packed bed (RPB) technology shows great potential for post-combustion capture. However, the capture process inside the full RPB is difficult to simulate, due to the complexity of the process and the neglect of the CO2 capture in the outer cavity zone. In this paper, a full 3D CFD model, including the packing and the inner and outer cavity zones, has been established employing the Eulerian porous medium method coupled with various sub-models. The CO2 capture performance in the packing and outer cavity zones has been quantitatively analyzed under different operating conditions. The simulation results show good agreement with the experimental data, and the contribution of the outer cavity zone to the CO2 capture of the RPB is in the range of 28 %∼42 %. This work provides a new approach to efficiently simulate the mass transfer process in the RPB.

POSSIBILITIES OF MINIMALLY INVASIVE METHODS OF DIAGNOSIS AND TREATMENT FOR CLOSED ABDOMINAL INJURIES

In this article, the study of the diagnostic effectiveness of ultrasound examination (ultrasound) in identifying signs of damage to the abdominal organs and a detailed description of the ultrasound semiotics of closed abdominal trauma (CAT). Purpose. The study of the diagnostic effectiveness of sonography in identifying signs of damage to the abdominal cavity organs and a detailed description of the ultrasound semiotics of BAT. Material and methods. Ultrasound was performed in 160 patients with blunt abdominal trauma as an initial method for diagnosing intra-abdominal injuries and was performed in the emergency department immediately upon admission to the clinic. Conclusin. Among the diverse sonographic semiotics of intraperitoneal injuries in CAT, the presence of various volumes of free fluid in the abdominal cavity is the most constant ultrasound signs. The developed method of ultrasound assessment of the volume of free fluid in the abdominal cavity, based on taking into account the thickness of the fluid layer and its prevalence in the abdominal cavity zones, does not complicate or lengthen the FAST protocol procedure, allows to determine the critical volumes of hemoperitoneum, which are crucial in choosing the tactics of surgical treatment of CAT

Numerical analysis of heat transfer characteristics in a flywheel energy storage system using jet cooling

A flywheel energy storage system (FESS), with its high efficiency, long life, and transient response characteristics, has a variety of applications, including for uninterrupted power supplies and renewable energy grids. The heat produced by the system as a result of power loss has a significant negative impact on the long-term stability in a vacuum environment. This paper proposes an impingement jet cooling structure with rotating axis to facilitate the heat dissipation of FESS. The implications of the cooling medium, nozzle length, cavity zone diameter, and nozzle diameter of the impingement jet cooling structure on flow and heat transfer performance are studied by field synergy theory. Additionally, the structural parameters are optimized using the response surface method. The Nusselt number, friction coefficient, field synergy angle, comprehensive coefficient of heat transfer, and temperature field are analyzed. Heat transfer can be improved by decreasing the diameter of the cavity zone, lengthening the nozzle, and increasing the nozzle diameter. The pressure drop of the optimized structure is at least 62.48% less than that of the unmodified structure, while the temperature increase of the cooling medium is nearly 3.5 times higher.

Influence of diamond parameters on microstructure and properties of copper-based diamond composites manufactured by Fused Deposition Modeling and Sintering (FDMS)

As an additive manufacturing technology, Fused Deposition Modeling and Sintering (FDMS) technology can give diamond tools some creative structures to be applied in more fields. To explore the influence of diamond parameters on diamond tools manufactured by FDMS, copper-tin-diamond composite samples with different diamond concentrations and particle size were prepared by FDMS technology in this paper. During the study, the morphological characteristics of diamond particles inside the samples during the debinding and sintering process are summarized and the influence of diamond parameters on the mechanical properties and structure of the samples was further explored. These influence laws were also verified by cutting experiments. The results show that most diamond particles are in an incomplete coating state because of the volatilization of the binder. Meanwhile, a higher concentration of diamond will lead to more pores and cavities in the samples; and the cavities can be connected to form a large area of cavity zone by the print layer, thereby resulting in a serious loss in the performance of the samples. On the other hand, a small diamond particle size can lead to agglomeration of particles. Subsequently, this will result in void generation and regional weakening of the holding ability. However, agglomeration and some pores or cavities will increase the wear of the matrix, expose more diamond particles, and finally improve the cutting efficiency of the dicing blades when cutting sapphire crystal. Excessive wear may reduce the life of the diamond tool, but improved of sharpness can be better applied in the field of precision machining.

Integration of Geophysical Methods for Doline Hazard Assessment: A Case Study from Northern Oman

Subsurface formations with low compaction, often, due to the presence of underlying cavities, are potential sources of hazards. Thus, understanding the occurrence, properties, and extension of these weak zones poses a major concern in engineering geophysics. In this study, we examine the ability of geophysical methods to map weak areas over carbonates in Northern Oman. The weak zones are known to cause surface depression in many areas. The geophysical methods examined involve Ground-Penetrating Radar (GPR), Seismic Refraction Tomography (SRT), and Electrical Resistivity Tomography (ERT). This integrated geophysical survey was conducted near the Bimmah sinkhole, in the Quriya area, Northern Oman. The survey covers both an area with ground truth (low compaction sediments overlaying a cave) and a part with unknown subsurface properties. GPR velocity analysis using selected diffraction’s fitting helped to identify high-velocity anomalies that were attributed to the cavity. The GPR interpretation was calibrated with SRT and ERT. The former showed a clear drop in P-wave velocity and low ray coverage at the cavity zone, while the latter demonstrated high resistivity anomalies caused by the air filling the cavity. The scope was to examine the geophysical methods response, especially the GPR, and utilize the results of this preliminary approach for a wider exploration investigation in the area. The results from the study indicated that the GPR is capable to serve as a pioneer method in detecting the cavities. Hence, the GPR will cover large area in the site and the other two methods will be used as complementary for the final subsurface conditions’ evaluation.

Detection of a Weak Structural Stratum and Stability Analysis of the Slope in an Intensely Weathered Open-pit Mine

Within the mining boundary of an open-pit mine located in southern China, due to the intense weathering of the slope rock stratum, the quaternary loose soil layer and soft rock stratum, karst cavity and water-bearing weathered-fracture zone and other weak structural strata have posed a great threat to the side slope stability of open-pit mining. Using the Flashres64 Multichannel Ultra-High-Density Electrometer to conduct on-site detection of the slope, based on the spatial distribution of the low-resistance layer and the drilling geological data, this study interpreted the stratum lithology of the slope and conducted effective identification of the weak structural stratum. Furthermore, according to the Hoek–Brown Failure Criterion, the Flashres64 reduced the strength of the mechanical parameters of the rock-soil and weak structural stratum of the slope, and imported the relevant data into the SLIDE software for slope stability analysis. The results showed that this method could make advanced macro–predictions of the weak structural stratum occurring in intensely weathered slopes. The slope stability analysis results considering the adverse effects of the weak structural stratum were also highly consistent with the actual engineering situation, for which the application is worth promoting in related fields.

Numerical investigation of a new type tube for shell-and-tube moving packed bed heat exchanger

An elliptical-like combined tube (ELCT) is proposed for the shell-and-tube moving packed bed heat exchanger. The heat transfer of particle flow around the ELCT is numerical studied. The kinetic energy ratio, contact number, contact time and heat transfer coefficient are analyzed. It is found that, the heat transfer performance of the ELCT is similar to that of the elliptical tube (ET) and better than the circular tube (CT). Compared with the CT, the ELCT significantly reduces the stagnation zone and the cavity zone, and improves the heat transfer at the top and the bottom of the tube (average increase of 42% and 53%). Furthermore, compared with the ET and the CT, the ELCT has better inside-tube heat transfer performance (average increase of 5% and 29%), various inside-tube heat transfer enhancement techniques (same with the CT) and better flexural capacity (average increase of 8% and 36% under same mass).

Numerical simulation and wind tunnel experiments on the effect of a cubic building on the flow and pollutant diffusion under stable stratification

The renormalization group k-ε turbulence model was adopted to simulate the effect of a cubic building on the flow structure and pollutant dispersion at different bulk Richardson numbers (Rib). The simulation results were compared with the corresponding results of wind tunnel experiments. The computational fluid dynamics numerical simulation results are in good agreement with the wind tunnel test results; as Rib increases, the stationary point on the windward side of the building gradually moves upward, and the top recirculation zone gradually moves towards the leeward edge of the building. The length of the windward cavity zone of the building changes little when Rib increases from 0.057 to 0.21; when Rib increases from 0.21 to 0.52, the length of the windward cavity zone of the building increases slightly; and when Rib is increased to 1.13, the length of the windward cavity zone of the building decreases greatly. Near Rib = 0.21, the flow field structure is transformed from the dominant turbulent convection field structure to similar laminar flow, where mean advection plays a more important role than does turbulent diffusion because of the very weak turbulence. The effects of different stable stratification on the diffusion of pollutants in the near field of the building are different. As Rib increases, the vertical distribution range of the plume gradually decreases, the maximum value of the concentration gradually increases, and the maximum concentration range near the emission source gradually moves from upwind to downwind of the emission source.

Protection of electricity transmission infrastructure from sinkhole hazard based on electrical resistivity tomography

Sinkhole formation induced by limestone quarrying has the potential to cause severe environmental problems that impact agricultural activities and damage property. Moreover, sinkholes present a stability hazard to critical infrastructure such as power transmission towers. Field investigations in northeast Thailand found surface expressions of potentially dangerous sinkholes adjacent to a limestone quarry. 2D electrical resistivity tomography (ERT) profiles were deployed across previously mapped fractures that are located near power lines in order to detect the presence of subsurface structures and cavities in the carbonate bedrock. A 3D ERT survey was conducted near the base of power transmission tower T1 to precisely determine variations in subsurface material and structures. The ERT results were combined to delineate possibly hazardous cavities and continuous fractures. The surficial collapse features were generally observed to be in alignment with interpreted subsurface cavities and fractures. Water-table declines, quarry dewatering, and quarry blasting are possible triggers for the formation of the sinkholes. Additional sinkhole collapses could intensify along specific air-filled cavity zones in the near surface. Professional evaluations and regulatory action may be necessary to limit further quarry dewatering activities and prevent additional sinkhole collapses and further risk to the power infrastructure.

Thermal performance analysis of naturally ventilated and perforated sheet based double skin facade system for hot summer conditions

A new skin of perforated sheets in the cavity of double skin facades (DSF) system is introduced for efficient heat removal from the cavity in hot summer conditions. In this paper, the analytical solution is developed to estimate the thermal performance of the double-skin façade system with and without perforated sheet operating under natural ventilation mode. This analytical model is designed to predict the solar heat gain coefficient (SHGC) for hot summer conditions. An experimental investigation has also been conducted to validate the proposed analytical model. Results showed good agreement between the measured and calculated value of SHGC for DSF system with and without perforated sheet. It is observed that the addition of a perforated sheet reduces the SHGC by nearly 51.5% as compared to DSF system. Perforated sheets enable a better stack effect within the air cavity zone and thereby improve heat transfer characteristics. Therefore, the benefit of the perforated sheet within the air cavity of DSF system is profound over conventional DSF system.

Features of the architectonics of the structures of the nasal cavity and choanal zone in children with congenital malformations of the eyes

The article provides data on the embryogenesis of the eyeball, nasolacrimal canal and nasal cavity. A frequent combination of congenital choanal atresia and anomalies in the development of the eyes was noted, most likely associated with the temporal and topographic parallelism of the intrauterine development of these anatomical areas. In order to assess the condition of the nasal cavity and choanal region in congenital eye pathology, 43 children with ophthalmological malformations were examined. In 32 (74.4%) children, according to endoscopic examination, changes in the anatomy of the choanal region with a change in its size in the form of incomplete atresia were revealed. The results obtained allow the authors to recommend that all children with congenital ophthalmological malformations be examined and monitored by an otolaryngologist with an endoscopic examination of the nasal cavity and nasopharynx.

STABILITY ANALYSIS FOR EMBANKMENTS WITH GEOELECTRICITY

Abstract The collapse of the embankment is a problem that needs attention to find the right solution, so that the risk can be minimized. The condition of the embankment is influenced by the strength of the soil layer of the embankment, groundwater flow in the embankment, the condition of the water level of the embankment and human activities around the embankment. Changes in the quality of soil density in the embankment can form cavity zones within the embankment which cause changes in groundwater flow patterns in the embankment. The degradation of the soil layer of the embankment can cause piping, overtopping which is the cause of erosion of the embankment body and disturbs the stability of the embankment. Therefore, to determine the condition of the embankment soil layer, research on the stability of the embankment has been carried out using the geoelectric method at the location of the embankment in the Cipancuh and Penjalin reservoirs, so that an image of the embankment soil layer is obtained to determine the cavity zones in the embankment, the flow pattern in the embankment soil layer. Keywords: cavity zones, flow patterns, geoelectric methods, the stability of the embankment.

Geoelectrical and geotechnical investigation of foundation failure in and around Oroke high school, Akungba- Akoko, southwestern Nigeria

Engineering structures are designed and constructed with an air of lifelong expectancy. Moreover, building foundation may experience failure due to presence of concealed geologic features such as cavity and shear zones which can lead to subsurface subsidence. Hence, it is imperative, prior to building construction, to investigate the physical properties of foundation soils and determine its suitability for design and construction of building structures. In the light of this, a geoelectric survey, involving three (3) electrical dipole - dipole array and geotechnical analysis methods were carried out around a distressed building at Oroke High School, opposite Adekunle Ajasin University, Akungba Akoko to establish the cause of failure for the structures foundation via delineating the subsurface structural features. The field electrical data were plotted on log –log graph sheets and the resulting curves were interpreted qualitatively by visual inspection, and quantitatively via partial curve matching and computer iteration techniques. For the geotechnical analysis, a total of twelve (12) soil samples were taken from different locations of about 30 meters intervals, at the depth of 1.5 meters. The pseudo – section and electrical sections indicate that the subsurface is heterogeneous in geological composition. The 2D dipole- dipole resistivity and pseudo – section delineated zones having resistivity values ranging from 200 to 700ohm meter, and those approaching infinity all within a depth of 0-5 m, the resistivity values of 27 to 139ohm meter suggest the presence of clay. The geoelectric section identified three subsurface geologic layers comprising clay /sandy, clay top soil / sub grade soil, clay / sandy clay and sand weathered layer and the basement (fresh) beneath the failed segment. Additionally, prominent fractures were discovered within some areas on the pseudo-sections. The results of the laboratory tests also included those of natural moisture content, specific gravity, grain size distribution curves, Atterberg limit, compaction test and California Bearing Ratio (CBR). In conclusion, electrical resistivity method was found to be an effective measure or tool in the site characterization. The soil/rock in these zones may require reinforcement in order to enhance its bearing capacity and increase the life span of the engineering foundation. Â

Experimental investigation of thermally activated glass fibre reinforced gypsum roof

Switch to energy-efficient air conditioning systems and the use of eco-friendly building materials would result in significant energy savings and reductions in CO2 emissions. Thermally activated building system (TABS) is a promising low-energy cooling technology, which provides better thermal comfort than the conventional air conditioning system. In TABS, cooled water circulated in the tubes embedded in one or any combination of roof, floor slab and walls, not only reduces the heat ingress but also cools the building. Integrating TABS with eco-friendly building materials like glass fibre reinforced gypsum (GFRG) could be an intertwining solution. A hybrid system that integrates TABS with GFRG roof is investigated in this study. The thermal behavior of this thermally activated glass fibre reinforced gypsum (TAGFRG) roof is analysed experimentally in terms of diurnal temperature gradients, thermal images of the interior and exterior roof surfaces, decrement factor and water temperature variations. The reinforcement zone of the TAGFRG roof handled a higher cooling load compared to that of air cavity zones. The diurnal temperature fluctuation of interior roof surface at the air cavity and reinforcement zones is reduced by 5.1 and 6.7 °C respectively by TAGFRG roof cooling.

Numerical Study of Heat Transfer in Gravity-Driven Particle Flow around Tubes with Different Shapes

In the present paper, the heat transfer of gravity-driven dense particle flow around five different shapes of tubes is numerically studied using discrete element method (DEM). The velocity vector, particle contact number, particle contact time and heat transfer coefficient of particle flow at different particle zones around the tube are carefully analyzed. The results show that the effect of tube shape on the particle flow at both upstream and downstream regions of different tubes are remarkable. A particle stagnation zone and particle cavity zone are formed at the upstream and downstream regions of all the tubes. Both the stagnation and cavity zones for the circular tube are the largest, and they are the smallest for the elliptical tube. As the particle outlet velocity (vout) changes from 0.5 mm/s to 8 mm/s at dp = 1.72 mm/s, when compared with the circular tube, the heat transfer coefficient of particle flow for the elliptical tube and flat elliptical tube can increase by 20.3% and 15.0% on average, respectively. The proper design of the downstream shape of the tube can improve the overall heat transfer performance more efficiently. The heat transfer coefficient will increase as particle diameter decreases.

Liquid nitrogen freezing method for exploring the mixing characteristics of liquid/liquid heterogeneous in outer packing cavity of Impinging Stream-Rotating Packed Bed

Impinging Stream-Rotating Packed Bed (IS-RPB) is a reactor developed to strengthen the mass and heat transfer in liquid-liquid mixing processes. The impingement, packing and packing edge cavity zones are crucial features in which mass transfer is highly relevant. In a heterogeneous system composed of an oleic and an aqueous phase, understanding the droplet diameter distribution in the packing edge cavity of an IS-RPB is a key to modeling and evaluating its mass transfer performance. However, such pattern is still unclear. In this work, the flow pattern of the oleic and aqueous phases, including the transitions of fluid ligament flow and droplet flow, and the oil droplet in mixing of oleic and aqueous phases in the packing cavity were studied under different experimental conditions by using a liquid nitrogen freezing method and studied by Optical microscopy. The results showed that droplet determined by this method has good reproducibility with a deviation within 8.4 %, and with a detection limit below 1 μm.