Records with Subject: Modelling and Simulations
Showing records 1 to 25 of 217. [First] Page: 1 2 3 4 5 Last
A Computational Fluid Dynamics Approach for the Modeling of Gas Separation in Membrane Modules
Salman Qadir, Arshad Hussain, Muhammad Ahsan
September 13, 2019 (v1)
Keywords: Computational Fluid Dynamics, concentration polarization, gas separation, membrane module
Natural gas demand has increased rapidly across the globe in the last decade, and it is set to play an important role in meeting future energy requirements. Natural gas is mainly produced from fossil fuel and is a side product of crude oil produced beneath the earth’s crust. Materials hazardous to the environment, like CO2, H2S, and C2H4, are present in raw natural gas. Therefore, purification of the gaseous mixture is required for use in different industrial applications. A comprehensive computational fluid dynamics (CFD) model was proposed to perform the separation of natural gas from other gases using membrane modules. The CFD technique was utilized to estimate gas flow variations in membrane modules for gas separation. CFD was applied to different membrane modules to study gas transport through the membrane and flux, and to separate the binary gas mixtures. The different parameters of membrane modules, like feed and permeate pressure, module length, and membrane thickness, have bee... [more]
Numerical Study of Pressure Fluctuation and Unsteady Flow in a Centrifugal Pump
Ling Bai, Ling Zhou, Chen Han, Yong Zhu, Weidong Shi
August 8, 2019 (v1)
Keywords: centrifugal pump, numerical simulation, pressure fluctuation, unsteady flow
A pump is one of the most important machines in the processes and flow systems. The operation of multistage centrifugal pumps could generate pressure fluctuations and instabilities that may be detrimental to the performance and integrity of the pump. In this paper, a numerical study of the influence of pressure fluctuations and unsteady flow patterns was undertaken in the pump flow channel of three configurations with different diffuser vane numbers. It was found that the amplitude of pressure fluctuation in the diffuser was increased gradually with the increase in number of diffuser vanes. The lower number of diffuser vanes was beneficial to obtain a weaker pressure fluctuation intensity. With the static pressure gradually increasing, the effects of impeller blade passing frequency attenuated gradually, and the effect of diffuser vanes was increased gradually.
Transient Modeling of Grain Structure and Macrosegregation during Direct Chill Casting of Al-Cu Alloy
Qipeng Chen, Hongxiang Li, Houfa Shen
August 7, 2019 (v1)
Keywords: cellular automaton, direct chill casting, finite element, grain structure, macrosegregation, solidification
Grain structure and macrosegregation are two important aspects to assess the quality of direct chill (DC) cast billets, and the phenomena responsible for their formation are strongly interacted. Transient modeling of grain structure and macrosegregation during DC casting is achieved with a cellular automaton (CA)−finite element (FE) model, by which the macroscopic transport is coupled with microscopic relations for grain growth. In the CAFE model, a two-dimensional (2D) axisymmetric description is used for cylindrical geometry, and a Lagrangian representation is employed for both FE and CA calculations. This model is applied to the DC casting of two industrial scale Al-6.0 wt % Cu round billets with and without grain refiner. The grain structure and macrosegregation under thermal and solutal convection are studied. It is shown that the grain structure is fully equiaxed in the grain-refined billet, while a fine columnar grain region and a coarse columnar grain region are formed in the n... [more]
Numerical Study on the Gas-Water Two-Phase Flow in the Self-Priming Process of Self-Priming Centrifugal Pump
Chuan Wang, Bo Hu, Yong Zhu, Xiuli Wang, Can Luo, Li Cheng
August 7, 2019 (v1)
Keywords: Computational Fluid Dynamics, gas-water two-phase flow, self-priming pump
A self-priming centrifugal pump can be used in various areas such as agricultural irrigation, urban greening, and building water-supply. In order to simulate the gas-water two-phase flow in the self-priming process of a self-priming centrifugal pump, the unsteady numerical calculation of a typical self-priming centrifugal pump was performed using the ANSYS Computational Fluid X (ANSYS CFX) software. It was found that the whole self-priming process of a self-priming pump can be divided into three stages: the initial self-priming stage, the middle self-priming stage, and the final self-priming stage. Moreover, the self-priming time of the initial and final self-priming stages accounts for a small percentage of the whole self-priming process, while the middle self-priming stage is the main stage in the self-priming process and further determines the length of the self-priming time.
Wave Characteristics of Coagulation Bath in Dry-Jet Wet-Spinning Process for Polyacrylonitrile Fiber Production Using Computational Fluid Dynamics
Son Ich Ngo, Young-Il Lim, Soo-Chan Kim
July 31, 2019 (v1)
Keywords: coagulation bath, Computational Fluid Dynamics, dry-jet wet spinning process, maximum wave amplitude, polyacrylonitrile-based carbon fiber, wave resonance
In this work, a three-dimensional volume-of-fluid computational fluid dynamics (VOF-CFD) model was developed for a coagulation bath of the dry-jet wet spinning (DJWS) process for the production of polyacrylonitrile (PAN)-based carbon fiber under long-term operating conditions. The PAN-fiber was assumed to be a deformable porous zone with variations in moving speed, porosity, and permeability. The Froude number, interpreted as the wave-making resistance on the liquid surface, was analyzed according to the PAN-fiber wind-up speed ( v P A N ). The effect of the PAN speed on the reflection and wake flow formed by drag between a moving object and fluid is presented. A method for tracking the wave amplitude with time is proposed based on the iso-surface of the liquid volume fraction of 0.95. The wave signal for 30 min was divided into the initial and resonance states that were distinguished at 8 min. The maximum wave amplitude was less than 0.5 mm around the PAN-fiber inlet nozzle... [more]
Comparison of Riser-Simplified, Riser-Only, and Full-Loop Simulations for a Circulating Fluidized Bed
Min Wang, Yingya Wu, Xiaogang Shi, Xingying Lan, Chengxiu Wang, Jinsen Gao
July 31, 2019 (v1)
Keywords: circulating-fluidized bed, Computational Fluid Dynamics, full-loop simulation, gas–solids flow, hydrodynamics, riser
With the development of computing power, the simulation of circulating fluidized bed (CFB) has developed from riser-simplified simulation to riser-only simulation, then to full-loop simulation. This paper compared these three methods based on pilot-scale CFB experiment data to find the scope of application of each method. All these simulations, using the Eulerian−Eulerian two-fluid model with the kinetic theory of granular theory, were conducted to simulate a pilot-scale CFB. The hydrodynamics, such as pressure balance, solids holdup distribution, solids velocity distribution, and instantaneous mass flow rates in the riser or CFB system, were investigated in different simulations. By comparing the results from different methods, it was found that riser-simplified simulation is not sufficient to obtain accurate hydrodynamics, especially in higher solids circulating rates. The riser-only simulation is able to make a reasonable prediction of time-averaged behaviors of gas−solids in most p... [more]
Distinct and Quantitative Validation Method for Predictive Process Modeling with Examples of Liquid-Liquid Extraction Processes of Complex Feed Mixtures
Axel Schmidt, Jochen Strube
July 31, 2019 (v1)
Keywords: atpe, biologics, design-of-experiments, liquid-liquid extraction, Modelling, monte-carlo, quality-by-design, Simulation, validation, verification
As of today, industrial process development for liquid-liquid extraction and scale-up of extraction columns is based on an experimental procedure that requires tests in pilot-scale. This methodology consumes large amounts of material and time and the utilized scale-up equations are crude estimates including considerable safety margins. This approach is practical for well-known systems or low-value products coupled with high production scale, where such a scale-up methodology has less impact on the overall profitability. However, for new high-value products in biologics manufacturing, a process development based on process understanding and the use of validated process models is imperative. Therefore, a distinct and quantitative validation workflow for liquid-liquid extraction modeling is presented on the example of two complex feed mixtures. Monte-Carlo simulations based on the presented model parameter determination concept result for both examples in prediction accuracy comparable to... [more]
Parametric Methodology to Optimize the Sizing of Solar Collector Fields in Series-Parallel Arrays
Eduardo Venegas-Reyes, Naghelli Ortega-Avila, Norma A. Rodríguez-Muñoz, Mario Nájera-Trejo, Ignacio R. Martín-Domínguez, Jonathan Ibarra-Bahena
July 31, 2019 (v1)
Keywords: heat recovery, solar heat for industrial processes (SHIP), solar thermal systems design, TRNSYS
The analysis of solar thermal systems through numerical simulation is of great importance, since it allows predicting the performance of many configurations in any location and under different climatic conditions. Most of the simulation tools are commercial and require different degrees of training; therefore, it is important to develop simple and reliable methodologies to obtain similar results. This study presents a parametric methodology to size stationary solar collector fields, with operating temperatures up to 150 °C. The costs of the collector loop piping and the pumping power of different series−parallel arrays is considered. The proposed tool was validated with experimental data and through simulations using commercial software. The tool allows establishing series−parallel arrays and calculates the volume of the storage tank according to the thermal load. The calculation is based on the system energy balance, where the mass flow and the heat losses in the interconnections of t... [more]
Calibration of Discrete-Element-Method Parameters for Cohesive Materials Using Dynamic-Yield-Strength and Shear-Cell Experiments
Subhodh Karkala, Nathan Davis, Carl Wassgren, Yanxiang Shi, Xue Liu, Christian Riemann, Gary Yacobian, Rohit Ramachandran
July 30, 2019 (v1)
Keywords: calibration, cohesion, discrete-element method, dynamic yield strength, JKR model, shear cell
This study tested the effectiveness of using dynamic yield strength (DYS) and shear-cell experiments to calibrate the following discrete-element-method (DEM) parameters: surface energy, and the coefficients of sliding and rolling friction. These experiments were carried out on cohesive granules, and DEM models were developed for these experiment setups using the JKR cohesion contact model. Parameter-sensitivity analysis on the DYS model showed that the DYS results in the simulations were highly sensitive to surface energy and were also impacted by the values of the two friction coefficients. These results indicated that the DYS model could be used to calibrate the surface energy parameter once the friction coefficients were fixed. Shear-cell sensitivity analysis study found that the influence of surface energy on the critical-state shear value cannot be neglected. It was inferred that the shear-cell model has to be used together with the DYS model to identify the right set of friction... [more]
Experimental Data of Fluid Phase Equilibria- Correlation and Prediction Models: A Review
Urszula Domańska
July 30, 2019 (v1)
Keywords: (vapor, correlation GE models, COSMO-RS), Extraction, HE, infragrance materials, ionic liquids, limiting activity coefficients, NRHB, or liquid/liquid) phase equilibria, or solid, PC-SAFT, pharmaceuticals, prediction (Mod. UNIFAC
The examples of phase equilibria in binary systems, solid/liquid (SLE), liquid/liquid (LLE), vapor/liquid (VLE), as well as liquid/liquid equilibria in ternary systems mainly containing ionic liquids (ILs), or the infragrance materials, or pharmaceuticals with molecular organic solvents, such as an alcohol, or water, or hydrocarbons, are presented. The most popular correlation methods of the experimental phase equilibrium data are presented, related to the excess Gibbs free energy models such as Wilson, universal-quasichemical, UNIQUAC and non-random two-liquid model, NRTL as well as several popular theories for the modeling of the phase equilibria and excess molar enthalpy, HE in binary or ternary mixtures are presented: the group contribution method (Mod. UNIFAC) and modified UNIFAC model for pharmaceuticals and lattice theory based on non-random hydrogen bonding (NRHB). The SLE, LLE, or VLE and HE of these systems may be described by the Perturbed-Chain Polar Statistical Associating... [more]
Thermodynamic vs. Kinetic Basis for Polymorph Selection
Benjamin K. Hodnett, Vivek Verma
July 30, 2019 (v1)
Keywords: classical nucleation theory, interfacial energy, metastable zone width, polymorphs, solubility, supersaturation
Ratios of equilibrium solubilities rarely exceed two-fold for polymorph pairs. A model has been developed based on two intrinsic properties of polymorph pairs, namely the ratio of equilibrium solubilities of the individual pairs (C*me/C*st) and the ratio of interfacial energies (γst/γme) and one applied experimental condition, namely the supersaturation identifies which one of a pair of polymorphs nucleates first. A domain diagram has been developed, which identifies the point where the critical free energy of nucleation for the polymorph pair are identical. Essentially, for a system supersaturated with respect to both polymorphs, the model identifies that low supersaturation with respect to the stable polymorph (Sst) leads to an extremely small supersaturation with respect to the metastable polymorph (Sme), radically driving up the critical free energy with respect to the metastable polymorph. Generally, high supersaturations sometimes much higher than the upper limit of the metastabl... [more]
A Mathematical Modeling of the Reverse Osmosis Concentration Process of a Glucose Solution
Chenghan Chen, Han Qin
July 30, 2019 (v1)
Keywords: concentration polarization, mass transfer process, mathematical model, reverse osmosis
A mathematical modeling of glucose−water separation through a reverse osmosis (RO) membrane was developed to research the membrane’s performance during the mass transfer process. The model was developed by coupling the concentration−polarization (CP) model, which uses one-dimensional flow assumption, with the irreversible thermodynamic Spiegler−Kedem model. A nonlinear parameter estimation technique was used to determine the model parameters Lp (hydraulic permeability constant), σ (reflection coefficient), and Bs (solute transport coefficient). Experimental data were obtained from the treatment of a pre-treated glucose solution using a laboratory-scale RO system, and studies on the validation of the model using experimental results are presented. The calculated results are consistent with the experimental data. The proposed model describes the RO membrane concentration process and deduces the expression of k (mass transfer coefficient in the CP layer). The verification shows that the e... [more]
Modeling of Load Bearing Characteristics of Jacket Foundation Piles for Offshore Wind Turbines in Taiwan
Cheng-Yu Ku, Lien-Kwei Chien
July 29, 2019 (v1)
Keywords: dynamic analysis, jacket foundation, offshore wind farm, pore pressure, seabed soils
This paper presents a pioneering study on numerical modeling of load bearing characteristics of the jacket foundation pile for offshore wind turbines on the west coast of Taiwan. Because Taiwan is located in an earthquake prone area, there is significant interest in improving the prediction of the behavior of wind turbine jacket foundations subjected to seismic loading. Investigation of the bearing capacity of the jacket foundation pile for the offshore wind farm using effective stress analysis, with consideration of pore pressure generation and soil/liquid coupled analysis, was conducted. A new procedure to evaluate the design of offshore wind turbine foundation piles in the sand and clay inter-layered soil was also proposed. Static and dynamic analyses of bearing capacity of the jacket foundation pile were conducted. Results obtained demonstrate that the design process for the jacket foundation pile proposed in this study can properly reflect the interaction behavior of the foundatio... [more]
A Composite Evaluation Model of Sustainable Manufacturing in Machining Process for Typical Machine Tools
Lishu Lv, Zhaohui Deng, Tao Liu, Linlin Wan, Wenliang Huang, Hui Yin, Tao Zhao
July 29, 2019 (v1)
Keywords: carbon efficiency, energy conservation and emission reduction, Energy Efficiency, green degree, typical machine tools
Machine tool is the basic manufacturing equipment in today’s mechanical manufacturing industry. A considerable amount of energy and carbon emission are consumed in machining processes, the realization of sustainable manufacturing of machine tools have become an urgent problem to be solved in the field of industry and academia. Therefore, five types of machine tools were selected for the typical machining processes (turning, milling, planning, grinding and drilling). Then the model of the energy efficiency, carbon efficiency and green degree model were established in this paper which considers the theory and experiment with the resource, energy and emission modeling method. The head frame spindle and head frame box were selected to verify the feasibility and practicability of the proposed model, based on the orthogonal experiment case of the key machining process. In addition, the influence rules of machining parameters were explored and the energy efficiency and green degree of the mac... [more]
Investigation of the Flow Characteristics of Methane Hydrate Slurries with Low Flow Rates
Cuiping Tang, Xiangyong Zhao, Dongliang Li, Yong He, Xiaodong Shen, Deqing Liang
July 26, 2019 (v1)
Keywords: flow assurance, flow characteristics, hydrate, Natural Gas, sludge, slurry
Gas hydrate blockage in pipelines during offshore production becomes a major problem with increasing water depth. In this work, a series of experiments on gas hydrate formation in a flow loop was performed with low flow rates of 0.33, 0.66, and 0.88 m/s; the effects of the initial subcooling, flow rate, pressure, and morphology were investigated for methane hydrate formation in the flow loop. The results indicate that the differential pressure drop (ΔP) across two ends of the horizontal straight pipe increases with increasing hydrate concentration at the early stage of gas hydrate formation. When the flow rates of hydrate fluid are low, the higher the subcooling is, the faster the transition of the hydrates macrostructures. Gas hydrates can agglomerate, and sludge hydrates appear at subcoolings of 6.5 and 8.5 °C. The difference between the ΔP values at different flow rates is small, and there is no obvious influence of the flow rates on ΔP. Three hydrate macrostructures were observed:... [more]
Possibilities and Limitations of CFD Simulation for Flashing Flow Scenarios in Nuclear Applications
Yixiang Liao, Dirk Lucas
July 26, 2019 (v1)
Keywords: computational fluid dynamics (CFD) simulation, flashing, mono-disperse, poly-disperse, two-fluid-model
The flashing phenomenon is relevant to nuclear safety analysis, for example by a loss of coolant accident and safety release scenarios. It has been studied intensively by means of experiments and simulations with system codes, but computational fluid dynamics (CFD) simulation is still at the embryonic stage. Rapid increasing computer speed makes it possible to apply the CFD technology in such complex flow situations. Nevertheless, a thorough evaluation on the limitations and restrictions is still missing, which is however indispensable for reliable application, as well as further development. In the present work, the commonly-used two-fluid model with different mono-disperse assumptions is used to simulate various flashing scenarios. With the help of available experimental data, the results are evaluated, and the limitations are discussed. A poly-disperse method is found necessary for a reliable prediction of mean bubble size and phase distribution. The first attempts to trace the evol... [more]
Estimation of Hourly, Daily and Monthly Global Solar Radiation on Inclined Surfaces: Models Re-Visited
Seyed Abbas Mousavi Maleki, H. Hizam, Chandima Gomes
July 26, 2019 (v1)
Keywords: hourly estimation, isotropic and anisotropic, solar energy, solar radiation model, tilt angle
Global solar radiation is generally measured on a horizontal surface, whereas the maximum amount of incident solar radiation is measured on an inclined surface. Over the last decade, a number of models were proposed for predicting solar radiation on inclined surfaces. These models have various scopes; applicability to specific surfaces, the requirement for special measuring equipment, or limitations in scope. To find the most suitable model for a given location the hourly outputs predicted by available models are compared with the field measurements of the given location. The main objective of this study is to review on the estimation of the most accurate model or models for estimating solar radiation components for a selected location, by testing various models available in the literature. To increase the amount of incident solar radiation on photovoltaic (PV) panels, the PV panels are mounted on tilted surfaces. This article also provides an up-to-date status of different optimum til... [more]
Thermal Simulation of the Fresh Food Compartment in a Domestic Refrigerator
Juan M. Belman-Flores, Sergio Ledesma, Armando Gallegos-Muñoz, Donato Hernandez
July 26, 2019 (v1)
Keywords: computer simulation, domestic refrigerator, interpolation, shelf position, thermal behavior
In the field of domestic refrigeration, it is important to look for methods that can be used to simulate, and, thus, improve the thermal behavior of the fresh food compartment. In this sense, this study proposes some methods to model the thermal behavior of this compartment when the shelves’ positions are changed. Temperature measurements at specific locations in this compartment were obtained. Several shelf position combinations were performed to use three 2D interpolation methods in order to simulate the temperature mean and the temperature variance. The methods used were: Lagrange’s interpolation, cubic spline interpolation and bilinear interpolation. Two validation points were chosen to verify the proposed methods. By comparing the experimental results with the computer simulations, it was possible to conclude that the method of Lagrange’s interpolation provided values that were not close to the real measured values. On the other hand, it was observed that the method of bilinear in... [more]
Numerical Analysis of the Effects of Rotating Wind Turbine Blades on the Aerodynamic Forces Acting on Tower
Takaaki Kono, Satoshi Nebucho, Tetsuya Kogaki, Takahiro Kiwata, Shigeo Kimura, Nobuyoshi Komatsu
July 26, 2019 (v1)
Keywords: aerodynamic force, blade-tower interaction (BTI), computational fluid dynamics (CFD), detached-eddy simulation (DES), horizontal-axis wind turbine (HAWT), tower
We have investigated the effects of the rotating blades of an upwind-type three-blade horizontal-axis wind turbine (HAWT) on the basic characteristics of aerodynamic forces acting on its tower by conducting improved delayed detached-eddy simulations (DESs). Three tip-speed ratios were considered for the operating conditions of the HAWT: λ = 3 (low), λ = 6 (optimum), and λ = 10 (high). The diversion of the flow approaching the tower by the rotating blades and the low-pressure region that formed downwind of the blades significantly affected the aerodynamic forces acting on the tower. For example, the azimuth angle around the tower at which the pressure reached a maximum at each height shifted significantly in the direction of the movement of the blade passing the tower because of the diversion of the flow by the blades. Fluctuations in the lift force of the tower were significantly larger than those in its drag force because of the low-pressure region downwind of the blades.
Mixed Lubrication Effects in the Lateral Lubricating Interfaces of External Gear Machines: Modelling and Experimental Validation
Divya Thiagarajan, Andrea Vacca
July 26, 2019 (v1)
Keywords: fluid power, gear pumps, hydraulics, mixed lubrication, thermoelastohydrodynamic (TEHD)
This article presents a novel mixed-thermoelastohydrodynamic (TEHD) model for the lateral lubricating interfaces which exist between floating lateral bushings and gears in external gear machines (EGMs). The proposed model integrates the influence of surface asperities along with the fluid structure and thermal interaction in the interface, especially in the regions of very low film thicknesses by following a stochastic approach in modelling the mixed lubrication regime. Furthermore, the current work includes validation of the predictions of the mixed-TEHD model against experimentally measured leakages from the lateral gap and compares the performance of this model with a previously developed full film TEHD model for the lateral gaps in EGMs.
A Performance Prediction Method for Pumps as Turbines (PAT) Using a Computational Fluid Dynamics (CFD) Modeling Approach
Emma Frosina, Dario Buono, Adolfo Senatore
July 26, 2019 (v1)
Keywords: energy saving, numerical modeling, PAT, urban hydraulic network
Small and micro hydropower systems represent an attractive solution for generating electricity at low cost and with low environmental impact. The pump-as-turbine (PAT) approach has promise in this application due to its low purchase and maintenance costs. In this paper, a new method to predict the inverse characteristic of industrial centrifugal pumps is presented. This method is based on results of simulations performed with commercial three-dimensional Computational Fluid Dynamics (CFD) software. Model results have been first validated in pumping mode using data supplied by pump manufacturers. Then, the results have been compared to experimental data for a pump running in reverse. Experimentation has been performed on a dedicated test bench installed in the Department of Civil Construction and Environmental Engineering of the University of Naples Federico II. Three different pumps, with different specific speeds, have been analyzed. Using the model results, the inverse characteristic... [more]
Pressure Fluctuations in the S-Shaped Region of a Reversible Pump-Turbine
Zijie Wang, Baoshan Zhu, Xuhe Wang, Daqing Qin
July 26, 2019 (v1)
Keywords: pressure fluctuation, pump-turbine, rotating stall, S-shaped region, vortex rope
Numerical simulations were performed to investigate pressure fluctuations in the S-shaped region of a pump-turbine model. Analyses focused on pressure fluctuations in the draft tube and in the gap between the guide vanes and runner. Calculations were made under six different operating conditions with a constant guide vane opening, and the best efficiency point, runaway point, and low-discharge point in the turbine brake zone were determined. The simulated results were compared with experimental measurements. In the draft tube, a twin vortex rope was observed. In the gap between the guide vanes and runner, a low frequency component was captured at both the runaway and low-discharge points in the turbine brake zone, which rotated at 65% of the runner frequency. This low frequency component was induced by the rotating stall phenomenon. At the runaway point, a single stall cell was found in the gap between the guide vanes and runner, while at the low-discharge point, four stall cells were... [more]
Integrated Equivalent Circuit and Thermal Model for Simulation of Temperature-Dependent LiFePO₄ Battery in Actual Embedded Application
Zuchang Gao, Cheng Siong Chin, Wai Lok Woo, Junbo Jia
July 26, 2019 (v1)
Keywords: battery management system, cell model, convective thermal model, lithium-ion battery, state-of-charge
A computational efficient battery pack model with thermal consideration is essential for simulation prototyping before real-time embedded implementation. The proposed model provides a coupled equivalent circuit and convective thermal model to determine the state-of-charge (SOC) and temperature of the LiFePO₄ battery working in a real environment. A cell balancing strategy applied to the proposed temperature-dependent battery model balanced the SOC of each cell to increase the lifespan of the battery. The simulation outputs are validated by a set of independent experimental data at a different temperature to ensure the model validity and reliability. The results show a root mean square (RMS) error of 1.5609 × 10−5 for the terminal voltage and the comparison between the simulation and experiment at various temperatures (from 5 °C to 45 °C) shows a maximum RMS error of 7.2078 × 10−5.
Field Synergy Analysis and Optimization of the Thermal Behavior of Lithium Ion Battery Packs
Hongwen He, Hui Jia, Weiwei Huo, Fengchun Sun
July 26, 2019 (v1)
Keywords: battery pack, electric vehicle, field synergy principle, temperature uniformity
In this study, a three dimensional (3D) modeling has been built for a lithium ion battery pack using the field synergy principle to obtain a better thermal distribution. In the model, the thermal behavior of the battery pack was studied by reducing the maximum temperature, improving the temperature uniformity and considering the difference between the maximum and maximum temperature of the battery pack. The method is further verified by simulation results based on different environmental temperatures and discharge rates. The thermal behavior model demonstrates that the design and cooling policy of the battery pack is crucial for optimizing the air-outlet patterns of electric vehicle power cabins.
Theoretical Analysis of Shrouded Horizontal Axis Wind Turbines
Tariq Abdulsalam Khamlaj, Markus Peer Rumpfkeil
July 26, 2019 (v1)
Keywords: Betz limit, momentum theory, nozzle diffuser augmented, wind lens, wind turbine
Numerous analytical studies for power augmentation systems can be found in the literature with the goal to improve the performance of wind turbines by increasing the energy density of the air at the rotor. All methods to date are only concerned with the effects of a diffuser as the power augmentation, and this work extends the semi-empirical shrouded wind turbine model introduced first by Foreman to incorporate a converging-diverging nozzle into the system. The analysis is based on assumptions and approximations of the conservation laws to calculate optimal power coefficients and power extraction, as well as augmentation ratios. It is revealed that the power enhancement is proportional to the mass stream rise produced by the nozzle diffuser-augmented wind turbine (NDAWT). Such mass flow rise can only be accomplished through two essential principles: the increase in the area ratios and/or by reducing the negative back pressure at the exit. The thrust coefficient for optimal power produc... [more]
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