COMSOL Multiphysics Platform Research Articles

Investigation on the impacts of thickness on thermal stress on Thermoelectric materials MoSi2 and Mo5SiB2

Thermoelectric cooler employs Peltier effect for dissipating heat in an electronic casing structure. It shows exceptional rewards over conservative cooling skill via quiet process, extended life span, and effortless integration. Nevertheless, Joule heating results in the accumulation of internal heat thereby exposes thermoelectric cooler towards the risk of thermo-mechanical breakdown all through continuous operations in pragmatic thermal surroundings. A relative analysis of the effect of thickness size on thermal stress on MoSi2 and Mo5SiB2 by the COMSOL-Multiphysics platform is offered. Mo5SiB2 in comparison to MoSi2 has lower anisotropic single crystal elastic moduli, along with lower shear modulus. Mo5SiB2 has a slightly higher bulk, shear and Young’s than MoSi2. RT Vickers hardness of Mo5SiB2 is much larger than those of MoSi2. Fracture toughness is comparable to those of MoSi2. In this paper, a 3D module of thermoelectric materials MoSi2 and Mo5SiB2 is designed on the way to examine the effect of thermal stress with increasing thickness of the material taking into consideration the temperature reliant TE material traits. One side of the module is kept at 300K with fixed constraints while the other side is kept at 1200K. It has been observed that the thermal stress induced in MoSi2 and Mo5SiB2 decrease exponentially with increase in thickness of the material. Beyond thickness of 500 nm, the incremental difference in thermal stress is not large although a slight rise in stress level is observed at thickness 700 nm. It was found that the induced thermal stress for a particular thickness in Mo5SiB2 is lower than MoSi2. For MoSi2, the voltage swings across the length is from -2.42mV to 1.09 mV whereas for Mo5SiB2, the voltage swings across the length is from -1.87 mV to 1.64 mV. It was found that excessive elevated levels of thermal strain may source the dislocations as well as cracks in the layers of the material.

Finite element-based analysis of composite serpentine flow channel 3D modeling of vanadium redox flow battery

ABSTRACT The flow channel design significantly affects the operating performance of the vanadium redox flow battery (VRB). Serpentine flow channels enable uniform distribution of electrolyte concentration, which are widely used in flow channel design. However, this design leads to high electrolyte pressure drop and increased pump losses, thus reducing operating efficiency. To solve this problem, this paper proposes a novel composite serpentine channel design. The flow channel can significantly reduce the problem of excessively high electrolyte pressure drop inside the cell. In this paper, based on conservation laws of momentum, mass, charge and reaction kinetics, a three-dimensional model of a composite serpentine flow channel vanadium redox flow battery is developed to analyze the electrolyte behavior the COMSOL Multiphysics platform. The simulation results show that the pressure drop of the composite serpentine flow channel is largely reduced compared with that of the serpentine flow channel. The novel design can effectively reduce the pressure drop, and thus reduce the pump loss, which provides a guidance for VRB flow channel design.

Penetration Grouting Mechanism of Time-Dependent Power-Law Fluid for Reinforcing Loose Gravel Soil

The time-dependent behavior of power-law fluid has a significant influence on the grouting effects of reinforcing loose gravel soil. In this paper, based on basic rheological equations and the time-dependent behavior of rheological parameters (consistency coefficient and rheological index), rheological equations and penetration equations of time-dependent power-law fluid are proposed. Its penetration grouting diffusion mechanism for reinforcing loose gravel soil was then theoretically induced. A set of indoor experimental devices for simulating penetration grouting was designed to simulate the penetration grouting of power-law fluid with different time-dependent behaviors for reinforcing loose gravel soil. Then, relying on the COMSOL Multiphysics platform and Darcy’s law, three-dimensional numerical calculation programs for this mechanism were obtained using secondary-development programming technology. Thus, the numerical simulations of the penetration grouting process of power-law fluid with different time-dependent behaviors for reinforcing loose gravel soil were carried out. This theoretical mechanism was validated by comparing results from theoretical analyses, indoor experiments, and numerical simulations. Research results show that the three-dimensional numerical calculation programs can successfully simulate the penetration diffusion patterns of a time-dependent power-law fluid in loose gravel soil. The theoretical calculation values and numerical simulation values of the diffusion radius obtained from this mechanism are closer to indoor experimental values than those obtained from the penetration grouting diffusion theory of power-law fluid without considering time-dependent behavior. This mechanism can better reflect the penetration grouting diffusion laws of a power-law fluid in loose gravel soil than the theory, which can provide theoretical support and guidance for practical grouting construction.

Study of hydraulic resistance of tangential swirlers

This article presents the results of experimental research and simulation of the hydraulic drag of tangential swirlers. Three types of swirler devices made with straight, profiled, and circular channel walls were studied within a wide range of design and process parameters. Simulation modelling on the Comsol Multiphysics platform was used to calculate hydraulic drag and determine the velocity and pressure fields. This allowed obtaining a dependence of the hydraulic drag coefficient of the investigated swirlers and identifying parameters affecting their hydraulic drag.

Multi-field simulation and optimization of SiNx:H thin-film deposition by large-size tubular LF-PECVD

In this paper, a coupled multi-physics field model based on the COMSOL Multiphysics platform is developed to simulate the deposition of SiNx:H thin films by LF-PECVD. The deposition process is simulated by combined analysis for the flow field, thermal field, chemical reaction field, and plasma field. The results have indicated that the temperature has the most significant effect on the deposition rate, the pressure and temperature are the major process parameter on the film uniformity. Through optimizing process parameters, the optimization range of the corresponding parameters is obtained. Compared with the original process, the coating rate of SiNx:H can be increased by 11.6%, and the uniformity performance can be controlled above 97%. By further optimizing the gas transport structure, the uniformity can be improved to 98.1%, the deposition rate can be increased by 1.44%. This paper provides a reference for solving the problems of low deposition rate and poor uniformity due to the increased size of tubular LF-PECVD equipment, which is conducive to improving the equipment capacity and the film quality, thus reducing the production cost and improving the performance of photovoltaic cells.

Coupled effects of surface interaction and damping on electromechanical stability of functionally graded nanotubes reinforced torsional micromirror actuator

This paper demonstrated the coupled surface effects of thermal Casimir force and squeeze film damping (SFD) on size-dependent electromechanical stability and bifurcation of torsion micromirror actuator. The governing equations of micromirror system are derived, and the pull-in voltage and critical tilting angle are obtained. Also, the twisting deformation of torsion nanobeam can be tuned by functionally graded carbon nanotubes reinforced composites (FG-CNTRC). A finite element analysis (FEA) model is established on the COMSOL Multiphysics platform, and the simulation of the effect of thermal Casimir force on pull-in instability is utilized to verify the present analytical model. The results indicate that the numerical results well agree with the theoretical results in this work and experimental data in the literature. Further, the influences of volume fraction and geometrical distribution of CNTs, thermal Casimir force, nonlocal parameter, and squeeze film damping on electrically actuated instability and free-standing behavior are detailedly discussed. Besides, the evolution of equilibrium states of micromirror system is investigated, and bifurcation diagrams and phase portraits including the periodic, homoclinic, and heteroclinic orbits are described as well. The results demonstrated that the amplitude of the tilting angle for FGX-CNTRC type micromirror attenuates slower than for FGO-CNTRC type, and the increment of CNTs volume ratio slows down the attenuation due to the stiffening effect. When considering squeeze film damping, the stable center point evolves into one focus point with homoclinic orbits, and the dynamic system maintains two unstable saddle points with the heteroclinic orbits due to the effect of thermal Casimir force.

Comparative analysis of thermoelectric behavior of molybdenum silicide (MoSi2) and bismuth telluride (Bi2Te3)

A comparative analysis of the thermoelectric behavior of Molybdenum Silicide and Bismuth Telluride using the COMSOL-Multiphysics platform is presented. Parameters like temperature distribution, potential distribution, figure of merit all the way through the length of the model and isothermal contours for these materials are reported. The outcomes of the modeling and simulation have revealed the potential use of Bismuth Telluride in thermoelectric applications at low temperature applications whereas Molybdenum Silicide is utilized as thermoelectric materials at high temperatures applications.

Lead-Cooled Fast Reactor Annular UN Fuel Design and Development of Performance Analysis Program

A kind of annular uranium nitride (UN) fuel suitable for lead-cooled fast reactor applications has been designed in this study. The design is directly targeting two main issues of UN fuel: severe swelling and thermal decomposition of UN fuel at high temperatures. A performance analysis program based on FORTRAN programming language has been developed for UN fuel in fast reactors. The program contains heat transfer, fuel stress-strain analysis, cladding stress-strain analysis, fission gas release and fuel-cladding mechanical interaction (FCMI) modules, etc. Extensive code verification has been performed by comparing simulation results obtained with the code and those obtained via the COMSOL Multiphysics platform. Preliminary code validation has been conducted as well by comparing code simulation results with experimental data. The results showed that this program could predict the fuel temperature, stress-strain, and displacement of UN fuel during reactor operation with a reasonable accuracy.

Flow Mechanism Characterization of Porous Oil-Containing Material Base on Micro-Scale Pore Modeling.

The self-lubricating effect of the porous oil-containing cage is realized by storing and releasing lubricants through its internal micro-scale pore structure. The internal flow and heat transfer process in the micron-submicron pore structure is crucial to the self-lubricating mechanism of the porous oil-containing cage. To this end, a new modeling method of porous cage was proposed based on random seeds theory, and the local two-dimensional models of porous cage with different micro-scale pore structure were established. The multiphysics coupling simulation analysis of lubricating oil inside the porous cage with the effect of centrifugal force and thermal expansion was carried out based on the COMSOL Multiphysics platform. In order to characterize the micro-scale pore structure, new structural parameter indicators, such as relative surface perimeter, effective porosity, tortuosity and fluid properties related to the internal flow process, were all extracted from the above models. Combing with the Hagen–Poiseuille equation, a flow resistance model of oil flow inside the porous oil-containing cage was obtained. Finally, comparison of simulation results and analytical solutions of the micro-scale resistance model was carried out to verify the correctness of the micro-scale resistance model. The work provides a new direction for the study of the lubrication mechanism of the porous oil-containing cage.

Optimization of process parameters and numerical modeling of heat and mass transfer during simulated solar drying of paddy

Present study aims to optimize the process parameters and to develop a 3-dimensional, multi-layered finite element model for predicting moisture and temperature profile during simulated solar drying of paddy. Drying of paddy was conducted in an in-house designed photovoltaic integrated hybrid solar dryer. Design expert software was employed for optimization of drying process parameters (power level, air velocity and moisture content). Analysis of variance (ANOVA) was performed at significance level (P < 0.05) for the linear and interaction effects of the variables on various quality parameters. The simulation studies were performed using COMSOL Multiphysics platform. Optimum parameters for drying paddy were found at 700 W, 3.5 m/s and 12% moisture with optimal temperature, milling yield and drying time of 46 °C, 71.48% and 90 min, respectively, having the desirability factor of 0.92. Milling yield was observed to vary linearly with moisture content. Furthermore, the three dimensional model was successfully developed for paddy loaded in bulk as well as, accounting husk, bran and endosperm layers. Diffusion coefficient of endosperm, bran and husk was found to be 2.95 × 10−11, 8.66 × 10−12 and 6.00 × 10−12 m2/s, respectively. The optimized parameters can be successfully used to dry paddy to ensure maximum throughput and uniform quality of products in every drying batch. Additionally, the developed model was validated and can be employed for monitoring the drying parameters to standardize the hybrid solar drying process.

Laboratory observations for two-dimensional solute transport in an aquifer-aquitard system.

Low-permeability media such as clay appear in nearly all hydrogeological systems. To date, although significant efforts have been put forward by hydrologists, transport mechanism is still not well understood in such media, especially in an aquifer-aquitard system. In this study, two-dimensional experiments of groundwater flow and solute transport were conducted in a clay-sand two-layer system to investigate the characteristics of flow and transport in such a system. Sodium chloride (NaCl) (a conservative tracer) from a tank was injected after passing by the pre-inlet reservoir where the mixing effect and flow transiency were analyzed. A new numerical model considering the mixing effect and flow transiency was developed to interpret the experimental data based on the finite-element COMSOL Multiphysics platform. Transport parameters were assessed by best fitting the observed breakthrough curves (BTCs). Several important results were obtained. Firstly, aquitard advection was found to be non-negligible and should be considered in a proper mathematical model for describing the transport process. Secondly, advective velocities were temporally variable and showed decreasing trends in the sand and clay layers, mainly due to the impacts of physical and biological clogging. Thirdly, the mixing effect in the pre-inlet reservoir led to a lower tracer concentration in the sand layer at early times. Finally, the observed BTCs exhibited early arrivals in the clay layer, possibly resulting from preferential flow pathways. These findings can provide hints for contamination remediation works in aquifer-aquitard systems.

Fast simulation of avalanche and streamer in GEM detector using hydrodynamic approach

A fast, hydrodynamic numerical model has been developed on the COMSOL Multiphysics platform to simulate the evolution and dynamics of charged particles in gaseous ionization detectors based on the Gaseous Electron Multipliers (GEM). Effects of using two-dimensional (2D), 2D axisymmetric and three-dimensional (3D) models of the detectors have been analyzed to choose the optimum configuration. The chosen model has been used to follow the entire operating regime of single, double and triple GEM detectors, including avalanche and streamer mode operations. The accumulation of space charge, its contribution towards the distortion of the applied electric field and production of streamers have been investigated in fair detail using the optimized model.

Modeling, fabrication, and structural characterization of thin film ZnO based film bulk acoustic resonator

This work reports the finite element modeling, fabrication and structural characterization a film bulk acoustic resonator (FBAR) devices using shadow mask technique. For the performance analysis of the FBAR device, simulations were performed on COMSOL Multiphysics platform. RF sputtering technique is used to deposit c-axis oriented zinc oxide (ZnO) thin film on Aluminum electrodes. The Aluminum electrodes were deposited using e-beam evaporation technique. The X-ray diffraction (XRD), atomic force microscopy (AFM), and scanning electron microscopy (SEM) techniques were used to examine the surface morphologies of the deposited piezoelectric film (ZnO). The quality of the deposited piezoelectric material film was measured with the help of XRD spectra and AFM is used to measure surface roughness of the deposited ZnO film and its measured value is 6.94 nm. The resonant characteristics of fabricated FBAR device are evaluated with the help of COMSOL Multiphysics simulations and the obtained values of effective electromechanical coupling constant (k2eff), quality factors (Qs and Qp) and Figure of merit are 3.0025%, 1811.3, 1711.4 and 54 (approximately), respectively.

Performance Enhancement and Applications Review of Nano Light Emitting Device (LED)

A nano light emitting device (LED) has been developed and is presented. This new LED, entitled LENS (Light Emitting Nano-pixel Structure), is a new nano-pixel structure designed to enable high-resolution display. It serves as the building block of a more complex structure called LENA (Light Emitting Nano-pixel Array), dedicated to nano-display applications, such as augmented and virtual reality (AVR). Previously designed and studied with a platform for ray tracing optimization, a complementary simulations study was performed using the Comsol Multi-Physics Platform in order to check for opto-electronics performance and physical nanoscale investigations. In addition to the physical complementary analysis, several studies have focused on optimizations: optimal geometry for a pixel (cylindrical or conical shape), and wavelength adaptation (optical communication). In addition to numerical simulation results, an analytical model has been developed. This new device holds the potential to enhance the light efficiency for military, professional and consumer applications, and can serve as a game changer in the world of nano-displays with high resolution.

Thermal analysis of loop mediated isothermal DNA amplification (LAMP) based point-of-care diagnostic device

Loop-Mediated Isothermal Amplification reaction or LAMP has been identified as a feasible DNA amplification process. Paper-based LAMP diagnostic devices offer several advantages for point-of-care (POC) applications. LAMP occurs at a constant temperature of higher limits, which remains a major challenge on-site. This calls for an efficient thermal design which is beneficial in maintaining a constant high temperature at POC locations. The present study reports thermal design and energy consumption analysis of a paper-based LAMP POC device for the first time using CFD analysis. The POC design consists of a rectangular porous membrane embedded on a rectangular solid material, heated from the side walls. Isothermal and discrete heating with different horizontal and vertical clearance configurations are used as a design parameter. CFD analysis of different thermal configurations is carried out in COMSOL Multiphysics platform to solve the energy and convection–diffusion-reaction equation in porous media. The thermal analysis demonstrated that two discrete heating configurations with high horizontal clearance are effective in reducing energy consumption. It was inferred that two portable AA batteries are sufficient for the POC device operation. Overall, the current work successfully demonstrates the energy optimization and speed of operation of the POC medical device by detailed thermal analysis.

All printed wide range humidity sensor array combining MoSe2 and PVOH in series

Single transducer-based sensors have limitations of sensitivity and detection range. To enhance the sensitivity and range of detection here, a multi-transducer-based sensing array is designed for humidity sensing applications. Two-dimensional (2D) transition metal dichalcogenide (TMDC) namely MoSe2 nano-flakes and an organic semiconducting polymer polyvinyl alcohol (PVOH) are employed as active layers for two different sensors on a single polyethylene terephthalate (PET) substrate. Here, MoSe2 nano-flakes are highly responsive towards the low relative humidity (RH) region below 50% RH, while the PVOH is responsive to high humidity levels above 50% RH. The two sensors are combined in series as sensor array, which are capable to detect linear humidity response from all range of RH. Screen-printing and spin coating techniques are utilized for fabrication of inter digital electrodes (IDEs) and active layers, respectively. The impedance responses of individual as well as sensor array are recorded at 1 kHz frequency to analyze the fabricated sensor, and COMSOL Multiphysics platform is used for designing and verification of experimental results. The fabricated sensor is capable to detect a wide range from 0 to 100% RH, with a response time (Tres) of 0.6 s and recovery time (Trec) of 0.9 s with a very high sensitivity of 50 kΩ/RH. This approach can resolve the limitations of sensitivity, detection range, and response time faced in single transducer-based sensors.

Performance evaluation of a direct evaporative cooling system with hollow fiber-based heat exchanger

Direct evaporative cooling systems usually involve the process of spraying water, which may form the drift of water droplets. In addition, the use of circulating water can also lead to the growth of bacteria and molding on the surface of the packing material, affecting the indoor air quality. To address these issues, this paper intends to propose an evaporative cooling method incorporated with hollow fiber membranes. The selective permeation membrane technology allows the membrane module to isolate air from water, which selectively allows only water vapor to pass through, preventing the droplets from entraining bacteria into the air. A mathematical model has been developed to theoretically investigate the heat and moisture transfer between water and air in a hollow fiber membrane-based evaporative cooling module. The governing equations for the pre-cooling IEHX were established and then solved by employing the COMSOL Multiphysics platform. This study validated the model by comparing its outlet air dry bulb temperature and relative humidity against experimental data acquired from literature sources. The numerical model showed good agreement with the experimental findings with maximum discrepancy of 7.0%. The validated model was employed to investigate the influences of the inlet air velocity, inlet air dry-bulb temperature, inlet air relative humidity and geometric parameters on the cooling effect of the evaporative cooling module. Simulation results indicated that the outlet air temperature is greatly affected by the relative humidity of the inlet air under constant inlet air temperature conditions. A higher inlet air relative humidity will result in a higher outlet air dry bulb temperature. In addition, the cooling effectiveness was reduced for a higher inlet air velocity. The design of the hollow fiber membrane-based evaporative cooling module was optimized based on the simulation study.

Effects of coupling in piezoelectric multi-beam structure

MEMS-based piezoelectric energy harvesters utilize the principle of piezoelectricity for harvesting energy from the ambient vibrations of the environment. These energy harvesters are popular because of their small size. Most of these energy harvesters are constructed using a cantilever beam or plate structure comprising of single or multiple beam or plates. This paper presents the idea of coupling effect present in the piezoelectric multiple-plate cantilever structures. In these multi-plate structures, the fixed ends of plates are connected by a metal layer. We observe that the vibrations of one plate tend to affect the vibrations and output of the neighboring plate. In this paper, we present a qualitative explanation of this coupling effect among the neighboring plates in terms of their electrical and mechanical interaction. Then we present a Finite Element Method Analysis of these multi-plate cantilever structures on COMSOL Multiphysics platform to verify our proposed hypothesis of coupling effect occurring in these structures.

Production performance of oil shale in-situ conversion with multilateral wells

A novel method using multilateral wells to perform oil shale in-situ conversion process is proposed in this paper. This method constructs radial branches in upper and lower oil shale formation as injection and production wells. Hot fluids are injected from the injection wells, and pyrolyzed oil and gas are extracted by production wells. In this study, a 3D transient model coupling fluid flow, heat transfer and chemical process is established and implemented on COMSOL Multiphysics platform to investigate the oil shale in-situ conversion process. The temperature field, production characteristics and energy performance are characterized. Sensitivity of oil shale properties and operational parameters are analyzed. Influences of multilateral-well arrangements are studied. The simulation results indicate that the products are strongly dependent to oil shale temperature. The specific heat capacity, injection fluid temperature and injection mass flow rate can significantly influence production performance, while thermal conductivity has negligible effect. Multilateral wells with 5 branches, 60° branch angle and 40 m branch length show the best production performance among the computational cases. This study provides comprehensive insights and suggestions for the application of multilateral wells in oil shale in-situ conversion process.

Experimental and Simulated Studies of Oil/Water Fully Dispersed Flow in a Horizontal Pipe

The flow of oil/water mixtures in a pipe can occur under different flow patterns. Additionally, being able to predict adequately pressure drop in such systems is of relevant importance to adequately design the conveying system. In this work, an experimental and numerical study of the fully dispersed flow regime of an oil/water mixture (liquid paraffin and water) in a horizontal pipe, with concentrations of the oil of 0.01, 0.13, and 0.22 v/v were developed. Experimentally, the values of pressure drop, flow photographs, and radial volumetric concentrations of the oil in the vertical diameter of the pipe cross section were collected. In addition, normalized conductivity values were obtained, in this case, for a cross section of the pipe where an electrical impedance tomography (EIT) ring was installed. Numerical studies were carried out in the comsolmultiphysics platform, using the Euler–Euler approach, coupled with the k–ε turbulence model. In the simulations, two equations for the calculation of the drag coefficient, Schiller–Neumann and Haider–Levenspiel, and three equations for mixture viscosity, Guth and Simba (1936), Brinkman (1952), and Pal (2000), were studied. The simulated data were validated with the experimental results of the pressure drop, good results having been obtained. The best fit occurred for the simulations that used the Schiller–Neumann equation for the calculation of the drag coefficient and the Pal (2000) equation for the mixture viscosity.