Three-dimensional Full-scale Model Research Articles

Three-dimensional gas–liquid flow simulation of a rotating packed bed using Eulerian porous media models

The rotating packed bed (RPB) is a typical equipment in chemical process intensification technology due to its excellent mass transfer performance. In this paper, a three-dimensional full-scale model was established based on the Eulerian two-fluid method to study the gas–liquid two-phase flow in RPBs. Three different single-phase wire screen packing pressure drop models coupled with the interfacial area model were used to construct resistance calculation methods for porous media, respectively. The results show that simulation deviations of the liquid holdup and the pressure drop of the m-K model range from 0.92 % to 27.61 % and 1.63 % to 34.59 %, respectively. In addition, the simulation accuracy of the liquid holdup of three models was obviously influenced by the rotational speed (N). The m-K model has the highest prediction accuracy at N = 500 ∼ 1500 rpm. At N = 2000 ∼ 2500 rpm, the B model has the highest prediction accuracy. Characteristics of gas–liquid flow under different conditions and nozzle designs were obtained. In particular, the impact of different nozzle designs on liquid distribution has been investigated using a new method based on user-defined functions (UDFs). A more homogeneous distribution of liquid within the packing can be achieved by increasing nozzle height, decreasing nozzle size, and increasing the number of nozzles.

Structure optimization of helium-cooled blanket for fusion reactor based on three-dimensional full-scale thermal-hydraulic analysis

Fusion energy is widely considered as the most promising method to solve the energy crisis, while the blanket is of vital importance in the fusion device due to its main function of thermal extraction and energy conversion. The high heat flux from plasma and the internal nuclear heat deposition are imposed on fusion blanket. Slice model or two-dimensional model is usually adopted for traditional design of fusion blanket, in which most side effects are neglected, introducing relatively large uncertainty for thermal removal capability of the blanket. In this study, the integral three-dimensional full-scale model is established based on the split-zone method for mesh generation. Based on the validated numerical method, the preliminary thermal-hydraulic analysis of the full-scale model shows that inadequate heat transfer and significant flow distribution difference are encountered for the initial blanket design, in which the full-scale effect is not considered. After that, the specific structure modifications are proposed for different blanket components to solve the abovementioned problems. The maximum temperature of first wall is reduced from 671°C to 639°C, which is under the material temperature limit of 650°C; the inverse V-shaped flow distribution in the cap is modified as more even flow in cap channels; the maximum temperature of the function zone in blanket is reduced from 999°C to 759°C, which is an important structure modification for the blanket. The integral three-dimensional full-scale thermal-hydraulic analysis is performed after the local structure modification. The results show that the function zone is cooled down obviously by the coolant in the side wall. Compared to the temperature limit of 900°C for lithium orthosilicate, there is a more rigorous limit for the beryllium material, since they share the common cooling capability layer by layer while the temperature limit for the latter is only 650°C. The three-dimensional full-scale thermal-hydraulic analysis in our research is valuable to evaluate the integral reliability of the fusion blanket.

A three-dimensional full-scale model for predicting the performance of deep-buried ground heat exchanger considering groundwater flow

It is critical to precisely determine the performance of deep-buried ground heat exchangers involving different geological layers in engineering projects of the geothermal energy utilization. Compared to the existing approaches solving only conduction between the ground heat exchanger and the surrounding ground based on the two-dimensional model, this paper established a three-dimensional full-scale coaxial ground heat exchanger model containing both aquifer and aquifuge layers involving groundwater effect. The convective heat transfer in pipes was calculated using the empirical correlation of Nusselt number to improve the computation efficiency. The groundwater velocity in the energy governing equation was assumed to be constant and along with the horizontal direction to further simplify the computation. The developed method was applied to a 2800 m and 2600 m depth ground heat exchangers with different geological conditions, and was validated by the field test and published data. The relative errors are less than 6.9%. The thermal influence ranges of the aquifer layer and the aquifuge layer close to aquifer are asymmetric about the circumferential direction. The results demonstrated that the three-dimensional full-scale model is necessary for accurately evaluating the performance of ground heat exchangers when there is groundwater migration.

Numerical simulation of fracture behavior for the pipeline with girth weld under axial load

The failure accidents of the pipeline caused by girth weld problems occur frequently in recent years. However, the fracture mechanism and behavior of girth weld in pipeline are not clear at present. Accordingly, based on Gurson-Tvergaard-Needleman (GTN) damage model, a three-dimensional full-scale model of the X80 pipeline with girth weld was established in this paper, in which the differences of material properties in base, weld, and heat-affected zone (HAZ) were considered. Subsequently, the fracture process of the pipeline with girth weld under uniaxial tensile load was obtained. On this basis, the fracture behavior and the causes of failure of the pipeline were analyzed. The elongation and fracture strain were respectively defined to quantitatively describe the fracture toughness of the pipeline. The results showed that the crack initiated at the junction of the weld and HAZ in the inner wall of the pipeline due to material softening of HAZ, and then the crack propagated from the inner wall to the outer wall until forming a penetrated crack. Lastly, the crack grew rapidly along the circumferential direction, resulting in the overall failure of the pipe. Compared to the pipeline without weld, there was a smaller value of the elongation and fracture strain in the pipeline with girth weld. The elongation and fracture strain of the pipeline without weld was 26.49% and 0.78, and that of the pipeline with girth weld was 4.73% and 0.18, which was reduced by 82% and 77% respectively.

Assessment of radiation damage of the first wall of a fusion neutron source DEMO-FNS with a blanket for the transmutation of minor actinides

The design of the demonstration fusion neutron source (DEMO-FNS) demonstration fusion–fission hybrid facility is carried out at the National Research Center ‘Kurchatov Institute’ in Russia. For the implementation of the DEMO-FNS project, it is important to assess the effect of the fast neutron spectrum on radiation-induced damage to the device materials, primarily the materials of the first wall, which is the most problematic unit of the device. Due to the lack of real hybrid fusion devices, the study can only be carried out using computer simulations of the experiment. A computer simulation using the Monte Carlo method was carried out to calculate the developed three-dimensional full-scale model of the DEMO-FNS reactor with a blanket for the transmutation of minor actinides. The MCNP-4 code was used with cross-sections from the FENDL-2.1 and ENDF/B-6 files, as well as with cross sections for calculating radiation displacements. The neutron spectrum in the first wall of DEMO-FNS was determined at the power of a volumetric deuterium–tritium neutron of 1.42 × 1019 n s−1. It was found that beryllium as a plasma-facing material has too short lifetime under the neutron load on the first wall and divertor plates of DEMO-FNS. The replacement beryllium to tungsten is problematic and requires special study. Copper alloys have sufficient resistance to the effects of neutron radiation of DEMO-FNS for one full power year, but will require several replacements when operating the device for more than 10 years. The steels used in fast reactors can meet the operational requirements of the first wall of DEMO-FNS. To solve the problem of choosing materials for the first wall of DEMO-FNS, new experimental researches on changes in the physical properties of these materials in the fast neutron spectrum are needed.

Three-dimensional computational model of a blood oxygenator reconstructed from micro-CT scans

Cardiopulmonary bypass procedures are one of the most common operations and blood oxygenators are the centre piece for the heart-lung machines. Blood oxygenators have been tested as entire devices but intricate details on the flow field inside the oxygenators remain unknown. In this study, a novel method is presented to analyse the flow field inside oxygenators based on micro Computed Tomography (μCT) scans. Two Hollow Fibre Membrane (HFM) oxygenator prototypes were scanned and three-dimensional full scale models that capture the device-specific fibre distributions are set up for computational fluid dynamics analysis. The blood flow through the oxygenator is modelled as a non-Newtonian fluid. The results were compared against the flow solution through an ideal fibre distribution and show the importance of a uniform distribution of fibres and that the oxygenators analysed are not susceptible to flow directionality as mass flow versus area remain the same. However the pressure drop across the oxygenator is dependent on flow rate and direction. By comparing residence time of blood against the time frame to fully saturate blood with oxygen we highlight the potential of this method as design optimisation tool.In conclusion, image-based reconstruction is found to be a feasible route to assess oxygenator performance through flow modelling. It offers the possibility to review a product as manufactured rather than as designed, which is a valuable insight as a precursor to the approval processes. Finally, the flow analysis presented may be extended, at computational cost, to include species transport in further studies.

Pre-operative planning for a periprosthetic femoral fracture using three-dimensional full-scale model; a case report

Pre-operative planning for a periprosthetic femoral fracture using three-dimensional full-scale model; a case report

Influential parameters on ultrafine particle concentration downwind at waste-to-energy plants

A numerical investigation on the parameters influencing the ultrafine particle concentrations downwind an incinerator plant has been carried out on a three-dimensional full scale model. The simulation was based on a modified version of the k–ε turbulence model in order to take into account the thermal buoyancy effect of the plume, and reproducing a stable and neutral atmospheric boundary layer by setting appropriate values of velocity, turbulent kinetic energy and turbulent dissipation rate. The ability of the model to reproduce and maintain a stable atmospheric boundary layer was evaluated by analyzing the turbulent characteristics of the flow along the domain. A parametric analysis made on the basis of different plant operational, environmental, and flue gas treatment parameters was carried out in order to evaluate the impact of incinerator plants on the background concentration of ultrafine particles. The evaluation was made at 5km downwind the chimney in a breathable area, showing that the most significant impact is due to the flue gas treatment section, with a variation on the background concentration up to 370% for a plant hypothetically working without controls on ultrafine particles emission. Operational and environmental parameters determine variations of the concentrations ranging from 1.62% to 4.48% for the lowest and highest chimney, from 1.41% to 4.52% for the lowest and highest wind speed and from 2.48% to 4.5% for the lowest and highest flue gas velocity, respectively. In addition, plume rise evaluation was carried out as a function of wind speed and flue gas velocity from the chimney.

Usefulness of Three-dimensional Full-scale Models for Simulating and Facilitating Corrective Osteotomy of Malunited Forearm Bones: Level 4 Evidence

Usefulness of Three-dimensional Full-scale Models for Simulating and Facilitating Corrective Osteotomy of Malunited Forearm Bones: Level 4 Evidence

Surgical simulation of circumferential osteotomy and correction of cervico-thoracic kyphoscoliosis for an irreducible old C6–C7 fracture dislocation

Many different surgical procedures have been employed in the treatment of fracture dislocation at the middle to lower cervical spine. However, consistent protocols and procedures have not been fully established for the surgical correction of an irreducible old cervical fracture dislocation associated with spinal deformity. We report a case of irreducible cervical fracture dislocation and kyphoscoliosis, in which surgical simulation using a three-dimensional full-scale model was useful for circumferential corrective osteotomy at the C6-C7 level. A 56-year-old man was diagnosed with an irreducible fracture dislocation at the C6-C7 level 2 months after a motor vehicle accident. He showed torticollis, and complained of severe pain in his neck and left upper arm. Radiographic examinations revealed that the C6 vertebra was translated anteriorly and laterally to the C7 vertebra. A bony union had progressed at the fracture site, showing rigid cervico-thoracic kyphoscoliosis. To assist in the preoperative planning, we created a three-dimensional, full-scale model from the patient's computed tomography data. Using the model, we performed a simulation of the planned circumferential corrective osteotomy at the C6-C7 level. Through the simulation, we could evaluate the deformed bony structures around the vertebral arteries at the C6-C7 level accurately. At the time of the actual surgery, corrective osteotomy combined with spinal fusion (C5-T2) with a pedicle screw-rod system was accomplished successfully without any neurovascular complications. After surgery, the patient experienced relief from pain, and his neck posture became normal. Surgical simulation using a three-dimensional, full-scale model was useful for improving the accuracy and safety of circumferential corrective osteotomy of the cervical spine.

Sleep Hygiene and Melatonin Treatment for Children and Adolescents With ADHD and Initial Insomnia

Case report of a child with a congenital skeletal anomaly who underwent instrumented surgery at the craniovertebral junction (CVJ).To describe the utility of surgical simulation using three-dimensional full-scale models for preoperative planning.Instrumented fusion of cervical spine with pedicle screws has several advantages compared with conventional sublaminar wiring, such as stronger fixation and reduction of malalignment. However, studies have reported a risk of injury to the vertebral artery (VA) from the insertion of screws. Especially in pediatric patients, the safety of pedicle screw insertion has not been fully established.A 7-year-old girl with a congenital skeletal anomaly presented with gait disturbance and clumsiness of her right hand. Radiographs showed dysplasia of the C1 posterior arch, leading to compression of the spinal cord posteriorly. Data from three-dimensional computed tomography (CT) angiography showed that the right VA was dominant and was shifted medially at the C2 pedicle. A surgical procedure was scheduled to resect the C1 posterior arch and perform an instrumented occiput-C2 fusion with a system of rod and screws. To evaluate the adaptation of the system to the small and deformed anatomic structure of her CVJ, we produced a three-dimensional full-scale model from CT data and performed a simulation of the scheduled surgery.Simulation of the surgery on the model showed acceptable adaptation of the system. However, the right C2 pedicle screw penetrated the medial wall of the VA foramen. In response to these results, we altered the surgical procedure and performed occiput-C3 fixation with a system of contoured loop and wiring. Although the patient had to use a halo-vest for 2 months, no complication occurred during surgery, and she experienced relief of her myelopathy after surgery.The three-dimensional full-scale model was useful for determining the safety of instrumented posterior occipitocervical fusion for a pediatric patient with a skeletal anomaly.

Pre-operative planning for atlanto-axial fixation in rheumatoid patients using three-dimensional full-scale model

Pre-operative planning for atlanto-axial fixation in rheumatoid patients using three-dimensional full-scale model