Comsol Multiphysics Simulation

The success, safety and stability of treatment methods of bottomhole formation zone depend on adequate bottomhole pressure. The latter is not directly controllable, but it can be changed by adjusting injection pressure. Using the Paccaloni method for any given measured injection rate, the downhole injection pressure can be estimated. In this paper, the Paccaloni method was developed, and the pressure drop changes in the skin zone for horizontal and vertical wells were estimated for planning acid treatment of the bottomhole formation zones in vertical, deviated and horizontal wells. To model pressure and velocity distributions in the bottomhole zone for the case of water injection in a vertical and horizontal wells COMSOL Mathphysics modules were used.

The electric field distribution in high voltage capacitor and surge arrester bushings is principally dependent on the geometry dimension and types of the materials used. The main target is to achieve a bushing design which has a good electric field stress control. In this paper, two-dimensional (2D) axial symmetrical model geometries of high voltage capacitor and surge arrester bushings have been developed using finite element analysis (FEA) method, which is COMSOL Multiphysics software. These models have been used to obtain the electric field distribution in capacitor and surge arrester bushing models. The effects of the bushing permittivity and electrical conductivity, the width and length and the metallic interface on the electric field distribution in bushing structure were analysed. From this study, an understanding of electric field distribution in bushing geometry may be attained, which may help in designing high voltage bushing stress control.

This paper reports preliminary results concerning thermal effects induced by urban/industrial air pollutants deposited on a limestone rock when heated by pulsed laser in the cleaning process. The process of laser cleaning treatment of the crust is simulated using COMSOL Multiphysics 4.4, finite element analysis software. Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy and Laser Induced Breakdown Spectroscopy techniques have been used to analyze the chemical composition of the samples. Two elements found as being present into the dust and in the crust, such as iron and magnesium particles are used for simulation in COMSOL. Therefore, the profiles heat evolutions on the crust surface and inside limestone are obtained as thermal interactions between the three components (iron, magnesium and limestone), simulating the non-homogeneous materials. It has been observed that iron impurities caused by the dust deposition may damage the limestone through a process of overheating, as a consequence of a high thermal conduction phenomenon, recorded for the region with iron impurities and sizes of micrometric order are localized. The thermal contact between the three components results in plots that reflect their thermal interactions.

In the field of optomechanics, radiation forces have provided a particularly high level of control over the frequency and dissipation of mechanical elements. Here we propose a class of optomechanical systems in which light exerts a similarly profound influence over two other fundamental parameters: geometry and mass. By applying an optical trap to one lattice site of an extended phononic crystal, we show it is possible to create a tunable, localized mechanical mode. Owing to light's simultaneous and constructive coupling with the structure's continuum of modes, we estimate that a trap power at the level of a single intracavity photon should be capable of producing a significant effect within a realistic, chip-scale device.

Floating photovoltaic systems deployable on ponds, lakes and water bodies are an attractive solution in photovoltaic cell technology with several advantages with respect to land-based installations, including a reduced expensive land investment required, reduced water evaporation, and suppression of algae growth. Moreover, the water body can be exploited as a heat sink for the thermal management of the photovoltaic cells, thereby decreasing the operating temperature and increasing efficiency. High operating temperatures are in fact one of the major problems in photovoltaic cells, which can degrade photovoltaic panels' electrical efficiency and service life. Recent research has demonstrated the potential of natural convection cooling loops for the thermal management of floating photovoltaic systems. Using numerical simulations combined with experiments, we show how sensitive is the performance of the natural convection cooling loop to the height of the coolant reservoir, which can then be used as a design parameter to maximise the cooling effectiveness of the photovoltaic module, with a consequent increase in electrical efficiency of 17.84% with respect to the base design without cooling.

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In many practical engineering situations, a source of vibrations may excite a large and flexible structure such as a ship's deck, an aeroplane fuselage, a satellite antenna, a wall panel. To avoid transmission of the vibration and structure-borne sound, radial or polar periodicity may be used. In these cases, numerical approaches to study free and forced wave propagation close to the excitation source in polar coordinates are desirable. This is the paper's aim, where a numerical method based on Floquet-theory and the FE discretision of a finite slice of the radial periodic structure is presented and verified. Only a small slice of the structure is analysed, which is approximated using piecewise Cartesian segments. Wave characteristics in each segment are obtained by the theory of wave propagation in periodic Cartesian structures and Finite Element analysis, while wave amplitude change due to the changes in the geometry of the slice is accommodated in the model assuming that the energy flow through the segments is the same. Forced response of the structure is then evaluated in the wave domain. Results are verified for an infinite isotropic thin plate excited by a point harmonic force. A plate with a periodic radial change of thickness is then studied. Free waves propagation are shown, and the forced response in the nearfield is evaluated, showing the validity of the method and the computational advantage compared to FE harmonic analysis for infinite structures.

This report provides a detailed analysis, simulation, and optimization of a modular laser-plasma confinement reactor. The reactor incorporates advanced technologies, including Kekulé-patterned graphene toroids, ultraintense ultra-short laser pulses, and zirconia-stabilized yttria (YSZ) confinement capsules with gold-doped silica aerogel coatings. It explores the feasibility of achieving energy gains through quasi-fusion processes enabled by Alfvén magnetosonic waves and magnetic asymmetries. Comparative analysis against experimental systems such as the SMART TOKAMAK highlights the reactor's superior efficiency and cost-effectiveness.

Simulation of criticality accident transients offers the ability to confirm understanding of critical configurations, bound accident scenarios and aid comprehensive emergency planning. Computational ability to recreate excursion power histories in fissile solution is sought due to the predominance of fissile solutions in process criticality accidents [1]. Applicable solution transient physics methodologies are developed for neutron kinetics, heat transfer, and radiolytic gas transport. This work is the first step in validating the use of COMSOL [2] as a flexible and powerful computational tool to simulate criticality excursions. Previously, characterization of excursion power history profiles has been limited to hand-calculations and simulation tools with 1D/0-D physics treatments for specific geometries [3, 4, 5, 6]. This work demonstrates COMSOL’s capability for an accurate, generalized approach to excursion simulations for nuclear safety applications.

A well-known challenge in using an Electrical Capacitance Tomography (ECT) system to obtain cross-section image of pipelines is the system’s non-uniform sensitivity distribution where the system is less sensitive at the pipe’s centre compared to the pipe’s wall proximity. A method to overcome this issue is by using two The aim of this work is to analyse the sensitivity map distribution by using two excitation potentials technique (1) to observe the changes of the inter-electrode capacitance and the permittivity of the dielectric material, (2) to investigate the distribution of electrical potential at the centre of the pipe, also (3) to investigate the feasibility of two excitation potentials technique to improve the sensitivity map in ECT system. The COMSOL Multiphysics software is used to simulate an ECT system to obtained results by generated phantoms, measured values such capacitance value and electrical potential, also for the sensitivity map distribution in the pipe model. By u...

Worldwide, most PILC MV underground cables in use are approaching the end of their design life; hence, failures are likely to increase. This paper studies the electric field and potential distributions within the PILC insulted cable containing common void-defect. The finite element model of the performance of the belted PILC MV underground cable is presented. The variation of the electric field stress within the cable using the Finite Element Method (FEM) is concentrated. The effects of the void-defect within the insulation are given. Outcomes will lead to deeper understanding of the modeling of Paper Insulated Lead Covered (PILC) and electric field response of belted PILC insulted cable containing void defect.

Direct and indirect approaches can be employed for estimating the heat flow through components in different application fields. In the building sector, the thermometric method is often applied by professionals for thermal transmittance evaluations. However, miscalculations can derive from inaccurate total heat transfer coefficients, and a consensus regarding the appropriate value to employ remains to be determined. Here, an apparatus was realized for laboratory tests and heat flux measurements were performed following direct and indirect approaches. Data acquired through a common heat flow sensor were compared with those computed through a post-processing based on radiative and convective estimations. The results were affected by the specific correlation adopted for computing the convective coefficients, with the percentage differences ranging from −9.8% to −0.4%. New measurement systems could be designed for automatically computing heat fluxes through indirect approaches, thus providing alternative solutions in the panorama of non-destructive tests for building energy diagnosis.

Absorption and mass transfer mechanism of CO2 in a uniformly distributed porous media was analyzed using simulation as well as experimental results. The study was performed in a closed PVT cell containing pressurized CO2 gas above a water saturated porous media. Pressure decay curves obtained from the simulation and the experiments were used to calculate early and late time diffusivity in accordance with analytical model. Mixing regime was visualized over time to comprehend the contribution of natural convection in mass transfer process. Early time diffusion coefficients were two orders of magnitude higher than late time diffusion coefficients in both simulation and experimental results. Density-driven natural convection had a significant impact at early stages giving rise to enhanced mass transfer and hence the disparity in diffusivity. The diffusivity at late stages were close to literature value. Pressure decay observed from large duration simulation results showed that equilibri...

This study investigates nanocarriers (NCs) for drug delivery targeting carotid artery atherosclerosis. This targeted drug delivery mechanism is based on ligand-receptor bindings facilitated by coating NCs with P-selectin aptamers, which exhibit high affinities for P-selectin plaque receptors. Recognizing the significant advantages of metal-organic frameworks (MOFs), such as their high drug-loading percentages, we chose them as nanocarriers for this research. Our evaluation considers critical factors: NC surface density (the number of attached nanocarriers per unit of plaque area), toxicity (percentage of NCs missing the target), and efficient drug transfer to plaque tissue. Employing molecular dynamics (MD) for drug loading calculations via van der Waals interactions and computational fluid dynamics (CFD) for toxicity, surface density, and drug transfer assessments, we achieve a comprehensive analysis. A cardiac cycle-based metric guides optimal MOF release conditions, establishing an ideal dosage of 600 NCs per cycle. MOF-801 exhibits outstanding drug delivery performance, particularly in plaque targeting. While a magnetic field enhances NC adhesion, its impact on drug transfer is limited, emphasizing the need for further optimization in magnetic targeting for NC-based therapies. This study provides crucial insights into NC drug delivery performance in carotid artery atherosclerosis, advancing the field of targeted drug delivery for atherosclerosis treatment. Atherosclerosis is one of the most crucial factors in vascular diseases that cause heart attacks and strokes 1. Improper blood cholesterol levels, which result in a decrease in high-density lipoprotein and an increase in low-density lipoprotein, lead to lipid plaque production with large necrotic nuclei and thin fibrous caps in the walls of blood vessels. These plaques are prone to rupture and can injure the inner layers of the artery walls. In this situation, the accumulation of platelets causes blood clots, arterial lumen narrowing, artery occlusion, and even death 2. According to reports, about 7.6 million Americans over the age of 20 have suffered a stroke, and it is predicted that more than 3.4 million American adults will experience a stroke by 2030 3. Since atherosclerosis is a complex disease with slow progress and the symptoms can be identified after the disease develops, a CT scan, MRI, and cardiac and brain angiography should be taken for diagnosis. Furthermore, one conventional treatment method is stents and balloon angioplasty, or coronary artery transplantation 4,5. With the development of nanotechnology in the future, it will be possible to replace invasive surgical methods with advanced molecular imaging technology to identify atherosclerotic plaques and evaluate the effectiveness of drugs and treatments. In addition, carrying nanoparticles to atherosclerosis plaques helps suppress the process of macrophages and healing the inflammation of the artery walls and accelerates the treatment of the disease 2,6. Continuous nanoscale particle modeling coupled with computational fluid dynamics (CFD) methods allows for the prediction of the movement and targeted adhesion of drug-carrying nanoparticles inside the bloodstream. This method discusses treatment strategies instead of the usual methods, with less time and cost to optimize, develop, and design unique drug carriers 7. Alishiri et al. 8 have studied targeted drug delivery on the carotid

This paper is an effort to analyze the performance and also increase the efficiency of InGaN/GaN solar cell. InGaN/GaN solar cell contains p and n-type layer of GaN and intrinsic layer of InGaN. The proposed structure of solar cell also contains front TCO, back TCO and back reflector. Performance of the designed solar cell was checked based on electric field, current density and electric potential generated in the designed cell. J-V curve is the most important factor to analyze the performance of the solar cell. Power conversion efficiency and fill factors have been calculated from this graph. According to the analysis of the simulation results efficiency of the designed solar cell was 12.91%. At the end, this thesis is about designing successfully with an efficient InGaN/GaN solar cell for further use in solar applications.

Summary In order to build a sustainable future for nuclear energy production, the international community assembled within GEN-IV has identified six classes of innovative systems deemed worth a thorough investigation with a view to a future implementation. ...

This study investigates nanocarriers (NCs) for drug delivery targeting carotid artery atherosclerosis. This targeted drug delivery mechanism is based on ligand-receptor bindings facilitated by coating NCs with P-selectin aptamers, which exhibit high affinities for P-selectin plaque receptors. Recognizing the significant advantages of metal-organic frameworks (MOFs), such as their high drug-loading percentages, we chose them as nanocarriers for this research. Our evaluation considers critical factors: NC surface density (the number of attached nanocarriers per unit of plaque area), toxicity (percentage of NCs missing the target), and efficient drug transfer to plaque tissue. Employing molecular dynamics (MD) for drug loading calculations via van der Waals interactions and computational fluid dynamics (CFD) for toxicity, surface density, and drug transfer assessments, we achieve a comprehensive analysis. A cardiac cycle-based metric guides optimal MOF release conditions, establishing an ideal dosage of 600 NCs per cycle. MOF-801 exhibits outstanding drug delivery performance, particularly in plaque targeting. While a magnetic field enhances NC adhesion, its impact on drug transfer is limited, emphasizing the need for further optimization in magnetic targeting for NC-based therapies. This study provides crucial insights into NC drug delivery performance in carotid artery atherosclerosis, advancing the field of targeted drug delivery for atherosclerosis treatment. Atherosclerosis is one of the most crucial factors in vascular diseases that cause heart attacks and strokes 1 . Improper blood cholesterol levels, which result in a decrease in high-density lipoprotein and an increase in low-density lipoprotein, lead to lipid plaque production with large necrotic nuclei and thin fibrous caps in the walls of blood vessels. These plaques are prone to rupture and can injure the inner layers of the artery walls. In this situation, the accumulation of platelets causes blood clots, arterial lumen narrowing, artery occlusion, and even death 2 . According to reports, about 7.6 million Americans over the age of 20 have suffered a stroke, and it is predicted that more than 3.4 million American adults will experience a stroke by 2030 3 . Since atherosclerosis is a complex disease with slow progress and the symptoms can be identified after the disease develops, a CT scan, MRI, and cardiac and brain angiography should be taken for diagnosis. Furthermore, one conventional treatment method is stents and balloon angioplasty, or coronary artery transplantation . With the development of nanotechnology in the future, it will be possible to replace invasive surgical methods with advanced molecular imaging technology to identify atherosclerotic plaques and evaluate the effectiveness of drugs and treatments. In addition, carrying nanoparticles to atherosclerosis plaques helps suppress the process of macrophages and healing the inflammation of the artery walls and accelerates the treatment of the disease 2,6 . Continuous nanoscale particle modeling coupled with computational fluid dynamics (CFD) methods allows for the prediction of the movement and targeted adhesion of drug-carrying nanoparticles inside the bloodstream. This method discusses treatment strategies instead of the usual methods, with less time and cost to optimize, develop, and design unique drug carriers 7 . Alishiri et al. have studied targeted drug delivery on the carotid

In this paper, thin films behavior obtained by Pulsed Laser Deposition (PLD) have been analyzed by means COMSOL Multiphysics, taking into account various experimental parameters: laser fluence, laser pulse width, laser wavelength, the temperature achieved during ablation, the target material type, the temperature of the support, the distance between target and support, etc. The obtained results are in very good agreement with the experimental. Moreover, the current model may be easily furthermore applied to any other film deposition technique by changing parameters values as needed in the experiments

Increasing environmental concerns with climate change have led many people around the world to demand urgent action, forcing
national governments to seek alternatives to carbon-based fuels. In the light of all this, it is of critical importance for our
civilization that carbon-based energy sources are rapidly replaced by renewable and sustainable sources without carbon
emissions. For this reason, the use of these clean energy sources and the efficiency of the processes in their production is a very
important issue. In this study, 3-dimensional, two-phase (hydrogen and water) computational fluid dynamics (CFD) analysis was
performed in a polymer electrolysis membrane cell (PEM). Analysis took place for 30 seconds. The water flow rate was kept
constant at 260 ml/min. As a result of the analysis, pressure, gas volume fraction and velocity data in the manifolds and in the
electrolysis channels where the electrolysis process takes place were interpreted. While the pressure change in the cell was quite
high in the range of 0-1.8 seconds from the beginning of the flow, it was observed that a balance was formed in the pressure
distribution after 1.8 seconds. It is understood that the number of channels in the model is a factor for the pressure inside the
manifold and the cell. However, it was observed that the unit gas production amount in the cell also changed along the channels.

A surface acoustic wave (SAW) gas sensor allows propagation of the wave through its surface piezoelectric materials. SAW devices are now frequently utilized. In a variety of fields due to their benefits characteristics such as a simple design, low cost, and superb performance, they may also be used in challenging environmental circumstances. The aim of this paper is to create a mass-sensitive transducer that works with metal oxide semiconductors to be integrated. An examination of the SAW gas sensor's materials, architecture design, and analysis of the SAW gas sensor are proposed in this paper. SAW devices were fabricated in commercial MEMS processes using piezoelectrical material such as Zinc oxide (ZnO), Tin Oxide (SnO2), and Barium titanate (BaTiO3) in the form of polycrystalline material. This paper represents a comparative study of a SAW gas sensor with two different designs of interdigitated transducers (IDT) using different piezoelectric materials as a substrate with a sensing layer based on COMSOL Multiphysics 5.5 software to maximize its output. The first design has the shape rectangular (IDT) while the second design has the shape of an ellipse.

An important challenge in membrane technology for gas separation is to simultaneously improve their permeability and selectivity. Often, the increase in one performance leads to the decline of the other. This study presents a solution to that problem by utilizing electrical field coupling to improve CO 2 permeation through a nitrile-containing poly (arylene-ether-ketone) (PEK-C(CN)) carbon molecular sieve membrane. Density functional based tight binding simulations of CO2 , CH4 , and N2 adsorption on PEK-C(CN) monolayer were conducted without and with electric field. The findings revealed that the electric field strength and orientation affected the molecules bond lengths, atomic charges, and bond angles. Investigation of their adsorption energy dominantly favored CO2 adsorption. Analysis of the partial density of states confirmed that adsorption interactions with the membrane were due to CO2 responses to the applied electric field. It additionally proved the electrical stability of PEK-C(CN) membrane. Computational fluid dynamics simulations of gas permeation through PEK-C(CN) membrane were performed without and with electric field. Results indicated an average pore distribution around 0.5 nm. The velocity flow distribution aided locate the interconnected pores, bringing to the fore the dominant transportation paths of gas molecules. It was uncovered that although the application of an electric field significantly improved the membrane gas permeability, it was not necessarily beneficial to its selectivity. − 5 V was determined to be the optimum potential for an improvement of CO2 permeability from 57.32 Barrer (no field) to 15924.91 Barrer, while also enhancing the selectivity. This work demonstrates the benefits of the electric field and its promising application in gas separation processes.

A simulated study of oil and water in 90 degree bend was carried on COMSOL 5.1 to characterize flow pattern and analyze the secondary flow. The Euler-Euler k-e Reynolds Averaged Navier-Stokes model was used to represent the fluid motion. Changes in the Reynolds number, curvature ratio and direction of gravity were made to evaluate the effects in the intensity of the secondary flow. In the end, it was possible to see that the bend direction does not affect the formation of secondary flow for Reynolds above 100,000. It appears that the fluid behavior on the pipe bend is strongly related to gravitational and centrifugal force ratio.

This paper reports preliminary results concerning thermal effects induced by urban/industrial air pollutants deposited on a limestone rock when heated by pulsed laser in the cleaning process. The process of laser cleaning treatment of the crust is simulated using COMSOL Multiphysics 4.4, finite element analysis software. Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy and Laser Induced Breakdown Spectroscopy techniques have been used to analyze the chemical composition of the samples. Two elements found as being present into the dust and in the crust, such as iron and magnesium particles are used for simulation in COMSOL. Therefore, the profiles heat evolutions on the crust surface and inside limestone are obtained as thermal interactions between the three components (iron, magnesium and limestone), simulating the non-homogeneous materials. It has been observed that iron impurities caused by the dust deposition may damage the limestone through a process of overheating, as a consequence of a high thermal conduction phenomenon, recorded for the region with iron impurities and sizes of micrometric order are localized. The thermal contact between the three components results in plots that reflect their thermal interactions.

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The tsunami generated by the 1995 Nuweiba Mw 7.2 earthquake in the Gulf of Elat-Aqaba (GOE) surprised the local people who were not aware of seismogenic sea waves in their neighborhood, far away from the open sea. Furthermore, the tsunami was triggered by strike slip rupture along the main segment of the Dead Sea Transform system. Eyewitness reports and field observations that were collected after the event, as well as recorded mareogram, showed unequivocally that there was a tsunami and that tsunami hazard in the GOE needs focused examination. In order to investigate the event we adopted the GeoClaw package (LeVeque, 2006, Clawpack software) and simulated selected models of the 1995 Nuweiba earthquake. We then compared the calculated tsunami scenarios with the actual evidences and discuss the outcomes.

Amorphous silicon thin-film photovoltaic modules have been developed as potential alternatives to crystalline-based due to their relatively less cost of production. This study incorporated both field measurements and software-based solutions to develop current-voltage characteristics of a SF100 a-Si thin film module as well as the mathematical functions of its electrical quantities with four environmental variables: irradiance, front panel temperature, back panel temperature, and ambient temperature. Results include twenty current-voltage curves based on the two-term exponential model with R2 scores greater than 90%, and equations for maximum power, fill factor, and efficiency obtained from factor analysis. The maximum power equation illustrates that the module’s output power is heavily influenced by the backside temperature, front/surface temperature, and irradiance, as compared to ambient temperature.

(Ac) and dimethyl methylphosphonate (DMMP) for Security A the electrodes of the system. Ions are modeled using literature values for their main parameters: K 0 , 2 and 4. By modeling, optimum voltages for achieving the proper sensitivity have been obtained.

A micro Planar Ion Mobility Spectrometer (P-FAIMS) has been simulated using FEM Multiphysics software. In P-FAIMS target ions are discriminated by the application of the proper separation voltages to the electrodes of the system. Modelling of vapour phase ions of two compounds have been studied for different values of electric field amplitude to gas number density (E/N) ratio: a health risky volatile acetone Ac 2 H + ion, and a chemical warfare agent simulant DMMPH + ion that emulates gas sarin. Results shows that simulations of ions behaviour in a P-FAIMS are possible with COMSOL Multiphysics software and that the time and intensity at which ions are detected are in good agreement with experimental data found in the literature.

The transient forced convection in tubulent channel flow with a step change in inlet temperature is solved by using a hybrid scheme, namely, by combining the generalized integral transform technique with a second-order accurate finite-differences. Stability and convergence of the scheme are examined. Numerical results are presented for the fluid bulk temperature and local Nusselt number as a function of position along the channel at different times, and the propagation of the thermal wave front during temperature transients is examined.

The effect of temperature on the electron and hole mobilities in silicon is studied using MATLAB. A theoretical study has been used for the electrons mobility and holes in silicon. The resulting data allows one to obtain the electron mobility and the hole mobility as a function of doping concentration and continuous temperature range between (200-550 Ko).

The reference MSFR (Molten Salt Fast Reactor) is a 3000 MWth molten salt reactor. In most molten salt reactors, such as the MSFR, the fissile and fertile materials are dissolved in a circulating salt that acts both as fuel and as coolant. The physical state of the fuel permits to consider draining as a way to mitigate hypothetical accidents. Moreover, a large-scale compaction cannot occur in such a core because, contrary to the solid fuel in a Fast Neutron Reactor, the fuel is nearly in its most compact geometry. This concept can be operated in the Th/U cycle and a fluoride salt or in the U/Pu cycle and a chloride salt. The goal of this work is to study the MSFR behaviour in case of a postulated reactivity insertion. In order to study the consequences of extreme reactivity insertions, the first objective is to study slow reactivity insertions to verify the efficiency of the draining of the liquid core. Then, in the case of extreme reactivity insertion, at the beginning of the transient, the salt cannot freely expand and the neutronic feedback is reduced. When the temperature of the salt rises, some vapor could be formed in the fuel, the vaporization of the salt could then lead to a quick expansion of the vaporized fluid. To perform these studies, we developed two independent codes. The first one, described in the present paper together with some associated studies and results, is being developed to study slow reactivity insertion. The second code, still under development, aims at calculating pressure and vaporization transient. The calculation tool seems to correctly represent the evolution of the calculated physical quantities and the mesh convergence is easily reached. This is encouraging for the continuation of this work to achieve the chaining with the fast phase calculation tool.

The reactor core, moderator and reflectors of a thermal spectrum advanced molten salt reactor will constitute multi-tons of graphite. Porous reactor-grade graphite, if unprotected, can be permeated by molten salt depending on the infiltrating pressure differential and entrance diameters of accessible graphite pores. Salt and gas permeation of graphite can affect microstructural properties and radiation behavior but also facilitate diffusion, deposition and retention of fission products and tritium. Because of the significant void volume of nuclear graphite, fission products and tritium retention due to salt permeation necessitates seal coatings or pore impregnation to reduce open porosity. Alternatively, very fine-grained graphite grades with low Xe permeability are being developed. Here, we survey the current technologies for mitigating salt and gas transport into graphite.

Recuperator is one of the key components in high temperature gas cooled reactors. Although cross-corrugated plates have been used to increase the thermal performance of the recuperators, the fundamental mechanisms of fluid flow and heat transfer are generally not clear. Fluid dynamics simulations and experiments are hence carried out to study the performance of the recuperators. A periodic cell is employed as the control volume. The flow field and heat transfer in sine-wave crossed-corrugated channels are investigated based on the Navier–Stokes and energy equations in the laminar flow regime between Re = 84 and 1168. The numerical results of the heat transfer factors and friction factors in different operating conditions show a fairly good agreement with the experimental measurements. The influence factors on the heat transfer and the hydraulic performance are also discussed in the paper. It is found that the heat transfer factor j and friction factor f decrease with the increase of...

The new control policy based on fuzzy approach for control of extraction process when taking into account criticality conditions was developed and verified. The example flowsheet suspected to exceed nuclear emergency conditions chosen for calculations was the 16-stage mixer-settler unit for uranium and plutonium recovery. The structure of the fuzzy controller is derived from earlier assessment of nuclear reactivity of the system. The results obtained confirm the usefulness of the fuzzy approach when the system's behaviour cannot be described ana1:,!tically and estimated accurately during process operati.on.

This study reports on investigations aiming to determine by numerical simulation the effect of space charges on the electrical and electromechanical constraints in microcavities contained in high-voltage cables insulation. The simulation is based on the numerical resolution of the Poisson equation by the finite element method. The authors calculate the electric field and they determine the electrostatical pressure for various space-charge density values. The elongation of microcavities is calculated for appreciating the effect of the electrostatical pressure on the walls of the cavity. The role of homocharges and heterocharges on constrains is studied and results of the simulation are in agreement with published technical literature.

This paper studies the electrical constraints within an XLPE insulated cable containing micro-cavities. The purpose of this work is to determine by simulation the distortions caused by micro-cavities on the electric field distribution in the insulating layer of cable. The computation method used to determine the electric field is based on numerical resolution of Laplace equation using the finite element method. The threshold of partial discharges ignition in gaseous cavities contained in XLPE insulation of 30 kV cable is studied. The computation of the critical field by approached formula of Paschen permits us to elucidate the harmfulness caused by a cavity according to its size and its position.

We present a wrapper that allows Abaqus user material subroutines (UMAT s) to be used as an External Material library in the software COMSOL Multiphysics. The wrapper, written in C language, transforms COMSOL's external material subroutine inputs and outputs into Fortran-coded Abaqus UMAT inputs and outputs, by means of a consistent variable transformation. This significantly facilitates conducting coupled, multi-physics studies employing the advanced material models that the solid mechanics community has developed over the past decades. We exemplify the potential of our new framework, UMAT4COMSOL, by conducting numerical experiments in the areas of elastoplasticity, hyperelasticity and crystal plasticity. The source code, detailed documentation and example tutorials are made freely available to download at www.empaneda.com/codes.

High temperature thermal storage technologies that can be easily integrated into future concentrated solar power plants are a key factor for increasing the market potential of solar power production. Storing thermal energy by reversible ga.i-solid reactions has the potential of achieving high storage densities while being adjustable to various plant configurations. In this paper the Ca(OH)2lCaO reaction system is investigated theoretically. It can achieve storage den.'iities above 300 kWhlm^ while operating in a temperature range between 400 and 600° C. Reactor concepts with indirect and direct heat transfer are being evaluated. The low thermal conductivity of the fixed bed of solid reactants turned out to considerably limit the performance of a storage tank with indirect heat input through the reactor walls. A one-dimensional model for the storage reactor is established and solved with the Finite Element Method. The reactor concept with direct heat transfer by flowing the gaseous reactant plus additional inert gas through the solid reactants did not show any limitation due to heat transfer. If reaction kinetics are fast enough, the reactor performance in case of the Ca(OH)2lCaO reaction system is limited by the thermal capacity of the gaseous stream to take-up heat of reaction. However, to limit pressure drop and the according losses for compression of the gas stream, the size of the storage system is restricted in a fixed bed configuration.

The reasons to use wireless sensor network (WSN) technology are convenience to nature, reliability, flexibility, low cost, selforganization, energy balance inside the network and easy establishment. In this study, an air contamination measurement and visualization system by the use of WSN is developed. Sensors which are capable of quantifying the density of Methane, carbon monoxide, isobutane, ethanol and hydrogen gases are programmed, and the density of carbon monoxide gas in each related region has been measured and processed to determine air pollution. Data measured by sensors is transferred to the visualization interface to transform the data into meaningful information. Changes in air pollution are shown instantly on a map given in the web interface. Lastly, the obtained results are compared by the results provided by Ministry of Environment and City Planning and the accuracy and the efficiency of the system is discussed. Keywords— Air pollution monitoring; air quality; wireles...

Microreaction technology has experienced almost exponential growth in the last decades due to significant practical benefits when compared with conventional reactors. However, the predominantly laminar flow impedes the required mixing in some processes. A novel design inspired by differential growth organic shapes in nature for improving mass transfer in microreactors is proposed. Firstly, this geometry allowed an area utilization of 16,1% and 27,2% higher than conventional serpentine and spiral channels, with the same hydraulic diameter, which can be useful for surface contact processes as in electrochemical reactions. Secondly, the performance of the microreactor was analyzed in terms of fluid flow and residence time distribution (RTD) for Reynolds in a range from 1-100. The continuous bending in the differential growth shape geometry leads to the formation of secondary vortices while approaching to the plug flow regime for the studied flow rates. These results were obtained by numerical analysis executed with the software COMSOL Multiphysics by solving threedimensional Navier-Stokes equations with a convection-diffusion model for the species concentration. The validation of the RTD numerical model was conducted in a one-body 3D-printed microreactor by injecting a pulse of rhodamine B in water and measuring the response with colorimetric techniques. These organic shapes open a window to further research in microfluidics, as its parametric design can be adapted to a wide variety of reaction conditions.

A method to linearize partial differential equations (PDEs) of heat diffusion and its initial with boundary conditions in a wide interval of temperature is presented. Thus, an analytical solution of the heat conduction problem was achieved in a virtual experiment performed in a lead wall with an ideally established configuration. For other arrangements where an analytical solution is not possible, simple standard programs can be used as an alternative to solve the linearized partial differential equations obtained with the proposed method. A sophisticated computer program as the standard gold method of COMSOL Multiphysics® was used for the evaluation of error of procedure. It was validated that the relative error of the analytical solution, in comparison to the digital simulation with COMSOL Multiphysics, can be found without the need to own and use the COMSOL Multiphysics program. For our configuration, the error is 1.16 % and focuses on the initial part of the process.

This paper discusses the mechanical and electrical effects on 3C-SiC and Si thin film as a diaphragm for MEMS capacitive pressure sensor operating for extreme temperature which is 1000 K. This work compares the design of a diaphragm based MEMS capacitive pressure sensor employing 3C-SiC and Si thin films. A 3C-SiC diaphragm was bonded with a thickness of 380 μm Si substrate, and a cavity gap of 2.2 μm is formed between the wafers. The MEMS capacitive pressure sensor designs were simulated using COMSOL ver 4.3 software to compare the diaphragm deflection, capacitive performance analysis, von Mises stress, and total electrical energy performance. Both materials are designed with the same layout dimensional with different thicknesses of the diaphragm which are 1.0 μm, 1.6 μm, and 2.2 μm. It is observed that the 3C-SiC thin film is far superior materials to Si thin film mechanically in withstanding higher applied pressures and temperatures. For 3C-SiC and Si, the maximum von Mises stres...

In a free-surface spillway, the upstream flow is non-aerated and the flow becomes a strong air-water mix downstream of the onset location of air entrapment. Field observations were conducted over a steep spillway chute, and detailed quantitative measurements were undertaken in real-world high-speed flows with strong turbulence and very high Reynolds numbers within the range 10 7 to 10 8. The data showed that the onset of air entrapment is a complicated transient three-dimensional process in high-speed strongly-turbulent flows. A robust optical flow (OF) technique was applied and provided physically-meaningful surface velocities in the nonaerated flow region. The streamwise velocities were reasonably close to ideal fluid flow calculations, with large streamwise surface velocity fluctuations, in the non-aerated flow region. Overall, the study demonstrated the application of optical techniques to prototype spillway flows, provided that some careful validation was undertaken.

Measures that heat up exhaust aftertreatment systems fast lead in general to lower fuel economy. A chemical heat storage (CHS) represents a new concept to exceed light-off temperatures fast. As a part of an FVV research project, potential storage materials were researched and analysed at Leuphana University Lüneburg. Their potential was then examined at the TU Braunschweig and prototype tests were carried out.

Certainly, here is the corrected version with spelling and grammar errors addressed:

"A numerical simulation of heat transfer and pressure loss analysis is presented for variously shaped turbulators inserted into a rectangular channel. A constant heat flux is applied to the external side of the channel. Numerical simulations were conducted using COMSOL Multiphysics. The shapes of the turbulators vary, and the effects of turbulator height are studied.

The obtained numerical results clearly show that the dynamic and thermal performances depend on the dimensions and shape of the turbulators. The development of swirling structures behind the turbulators is observed, which seems to be responsible for the increase in heat transfer. Pressure drops are primarily attributed to the flow blockage caused by these elements."

Molten Salt Fast Reactor (MSFR) is a conceptual design by European Union that contains a draining tank located underneath the reactor. In case of a planned reactor shut down or in emergency situations or in case of accidents leading to an excessive increase of the temperature in the core, the liquid fuel will be passively drained into the draining tank by gravity force. Ni-based alloy is considered to be resistant against damage at temperatures in the range of 1250°C-1350°C. According to the previous calculation in the EVOL project, this damage temperature could be reached in approximately 20 minutes in the worst case, if the liquid fuel stays in the core. Based on the core geometry of MSFR in the EVOL project, times for draining fuel from the core region are analytically evaluated through variation of draining tube diameter, draining tube length and variation of damage degree of freeze plug. A preliminary evaluation of some orders of magnitude of draining time periods is presented ...

Şekil 1.3: 2.ci Koşullar Seti için MC hibrit yöntem (DERZSİ, 2009) ile karşılaştırma (= 40 Pa, = 441 V, = 3 cm, = 0.033). (a) elektron ile iyon yoğunlukların, (b) elektrik alanın, (c) iyonlaşma kaynak teriminin, ve (d) elektron sıcaklığının uzamsal dağılımları.

This article contains the free convective flow in a rectangular cavity having partially heated vertical wall. Further it is assumed that flow and thermal profiles are influenced by Lorentz forces applied in the perpendicular direction to the flow distribution. This physical setup is translated in mathematical form, which is expressed as differential equation. Finite element method is adopted to get the solution of these partial differential equations, the results against various flow controlling variables are presented in contour plots and line graphs. Results depict that at various heated length streamlines distribution gets stronger due to stronger buoyancy effects. Higher values of Rayleigh number correspond to maximum Nusselt number and temperature profile. Moreover, the streamlines pattern is reduced by increasing Hartman number and resulting the conduction mode of heat transportation.

This article contains the free convective flow in a rectangular cavity having partially heated vertical wall. Further it is assumed that flow and thermal profiles are influenced by Lorentz forces applied in the perpendicular direction to the flow distribution. This physical setup is translated in mathematical form, which is expressed as differential equation. Finite element method is adopted to get the solution of these partial differential equations, the results against various flow controlling variables are presented in contour plots and line graphs. Results depict that at various heated length streamlines distribution gets stronger due to stronger buoyancy effects. Higher values of Rayleigh number correspond to maximum Nusselt number and temperature profile. Moreover, the streamlines pattern is reduced by increasing Hartman number and resulting the conduction mode of heat transportation.