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Records with Subject: Modelling and Simulations
Showing records 613 to 637 of 5392. [First] Page: 1 22 23 24 25 26 27 28 29 30 Last
Liquified Petroleum Gas-Fuelled Vehicle CO2 Emission Modelling Based on Portable Emission Measurement System, On-Board Diagnostics Data, and Gradient-Boosting Machine Learning
Maksymilian Mądziel
April 18, 2023 (v1)
Keywords: Artificial Intelligence, Carbon Dioxide, emission modelling, LPG, Machine Learning, portable emission measurement system, vehicle emission
One method to reduce CO2 emissions from vehicle exhaust is the use of liquified petroleum gas (LPG) fuel. The global use of this fuel is high in European countries such as Poland, Romania, and Italy. There are a small number of computational models for the purpose of estimating the emissions of LPG vehicles. This work is one of the first to present a methodology for developing microscale CO2 emission models for LPG vehicles. The developed model is based on data from road tests using the portable emission measurement system (PEMS) and on-board diagnostic (OBDII) interface. This model was created from a previous exploratory data analysis while using gradient-boosting machine learning methods. Vehicle velocity and engine RPM were chosen as the explanatory variables for CO2 prediction. The validation of the model indicates its good precision, while its use is possible for the analysis of continuous CO2 emissions and the creation of emission maps for environmental analyses in urban areas. T... [more]
The Use of Evolutionary Algorithms in the Modelling of Diffuse Radiation in Terms of Simulating the Energy Efficiency of Photovoltaic Systems
Wiktor Olchowik, Jędrzej Gajek, Andrzej Michalski
April 18, 2023 (v1)
Keywords: diffuse solar radiation, evolutionary algorithms, mathematical model, photovoltaic micro-grids
In light of the rapidly growing number of photovoltaic micro-grids, the modelling of their short-term power yields based on meteorological measurements is increasing in significance. This requires the knowledge of total and diffuse instantaneous solar radiation; however, most meteorological stations conduct actinometric measurements only with regard to total solar radiation, especially on a minute scale. This paper contains an analysis of the currently used PV cell mathematical model and suggests its modification aimed at calculating PV cell power with satisfactory accuracy, without the knowledge of diffuse solar radiation. Three function families were proposed to approximate the relationship between diffuse irradiance and the total and theoretical total irradiance variance for a cloudless sky. A program has been implemented to identify functions from the aforementioned function families. It leverages an evolution strategy algorithm and a fitness function based on the least-squares poi... [more]
Component-Oriented Modeling Method for Real-Time Simulation of Power Systems
Zhao Jin, Jie Zhang, Shuyuan Wang, Bingda Zhang
April 18, 2023 (v1)
Keywords: component-oriented, node elimination strategy, real-time simulation, reconstruction technology, simulation modeling
This paper proposes a component-oriented modeling method for power system simulation, which optimizes the modeling process of the FPGA-based real-time digital simulator (FRTDS) to enhance its computational efficiency. In this paper, a component modeling method for various types of elements in the power system is presented, which makes the modeling process in FRTDS more user-friendly and highly scalable. By applying the concepts of combination and reconstruction of components to electrical components, the component-oriented modeling method becomes better suited for combined elements with fixed connection modes and elements that require online model replacement in the power system. Utilizing the characteristics of component-oriented modeling, the variable declaration structure and node elimination strategy in the simulation script are optimized, enabling the simulation script to fit better with the hardware structure of FRTDS. Additionally, a substation is simulated in FRTDS with a simul... [more]
Simulation of Triple-Cation Perovskite Solar Cells: Key Design Factors for Efficiency Promotion
Tarek I. Alanazi, Omer I. Eid
April 18, 2023 (v1)
Keywords: electron transport layer, hole transport layer, interface defects, perovskite solar cells, SCAPS-1D, triple cation
Compositional engineering is considered one of the recent interesting techniques used in the field of perovskite solar cells (PSCs). In this method, more than one material was used in a specific cation in the perovskite structure. This work aims to simulate the cesium-containing triple-cation perovskite (TCP) via the SCAPS-1D simulation program with a device structure of ITO/SnO2/TCP/Spiro-OMeTAD/Au. First, we studied the effect of interface defects on the PCSs with respect to experimental results and found that when no interface defects occur, the power conversion efficiency (PCE) reaches a value of 22.16% which is higher than the reported PCE, implying that the fabricated cell suffers from the interface defects as a main effect on cell degradation. Incorporating interface defects into the simulation results in a very good match between the experimental and simulated data with a PCE of 17.92%. Further, to provide possible routes to enhance the performance of the solar cell under inves... [more]
Numerical and Parametric Study on Open-Type Ceiling Radiant Cooling Panel with Curved and Segmented Structure
Minzhi Ye, Ahmed A. Serageldin, Katsunori Nagano
April 18, 2023 (v1)
Keywords: ceiling radiant cooling panel, CFD simulation, cooling capacity, parametric analysis
A suspended open-type ceiling radiant cooling panel (CRCP) has been proposed recently. The main challenge is improving its cooling performance to overcome limitations for extensive use. Therefore, this study aims to optimize the design of CRCPs with curved and segmented structure to enhance heat transfer. A three-dimensional CFD model was developed to investigate the cooling capacity and heat transfer coefficient of the CRCPs installed inside a single enclosed room. Panel structure was determined based on four dependent parameters: the panel curvature width (L, m), the panel curvature radius (r, m), the void distance (d, m) between each panel or panel segment, and the panel coverage area (Ac, m2). The panel surface area (As, m2) and the ratio of panel curvature width to radius (L/r) were also examined. A total of 35 designs were compared under 7 different cooling load conditions, and 245 cases were carried out. The results show that the nominal cooling capacity and heat transfer coeffi... [more]
Techno-Economic Analysis of the Modernization Options of a Gas Turbine Power Plant Using Aspen HYSYS
Dias Raybekovich Umyshev, Eduard Vladislavovich Osipov, Andrey Anatolievich Kibarin, Maxim Sergeyevich Korobkov, Tatyana Viktorovna Khodanova, Zhansaya Serikkyzy Duisenbek
April 18, 2023 (v1)
Keywords: Aspen HYSYS, Carbon Dioxide, CHP, gas turbine, HRSG, NOx
Currently, 90% of Kazakhstan’s oil is situated in 15 oil and gas fields where simple cycle gas turbines are utilized for electricity generation. The need for developing techniques to enhance the efficiency and eco-friendliness of fuel consumption in Kazakhstan’s oil fields is imperative. In this article, methods for improving the energy efficiency of a simple gas turbine power plant functioning in an oil field are discussed, with consideration given to the impact of ambient temperature and specific environmental constraints, such as water scarcity and high temperatures. Two schemes to increase efficiency are evaluated: the first involves the utilization of a waste heat boiler for steam production intended for technological purposes, while the second involves electricity generation through a combination of a waste heat boiler and a steam turbine. Models based on Aspen HYSYS were formulated, with actual gas turbine power plant operation taken into account. Analysis indicated that a waste... [more]
Simulation of Internal Manifold-Type Molten Carbonate Fuel Cells (MCFCs) with Different Operating Conditions
Kyu-Seok Jung, Kai Zhang, Chang-Whan Lee
April 18, 2023 (v1)
Keywords: computational fluid dynamics (CFD), flow direction, gas utilization, internal manifold, molten carbonate fuel cells (MCFCs), operating temperature, reforming area, S/C ratio
Molten carbonate fuel cells (MCFCs) use molten carbonate as an electrolyte. MCFCs operate at high temperatures and have the advantage of using methane as a fuel because they can use nickel-based catalysts. We analyzed the performance of an internal manifold-type MCFC, according to operating conditions, using computational fluid dynamics. Different conditions were used for the external and internal reforming-type MCFCs. Flow directions, gas utilization, and operating temperatures were used as the conditions for the external reforming-type MCFCs. The S/C ratio and reforming area were used as the conditions for internal reforming-type MCFCs. A simulation model was developed, considering gas transfer, reforming reaction, and heat transfer. The simulation results of external reforming-type MCFCs showed similar pressure drops in all flow directions. As the gas utilization decreased, the temperature decreased, but the performance increased. The performance improved with increasing operating t... [more]
Methodology for Modeling Multiple Non-Homogeneous Thermal Zones Using Lumped Parameters Technique and Graph Theory
Frank Florez, Jesús Alejandro Alzate-Grisales, Pedro Fernández de Córdoba, John Alexander Taborda-Giraldo
April 18, 2023 (v1)
Keywords: buildings, contact matrix, experimental test, graph theory, lumped parameters, mathematical model, scale-reduced model, thermal zones
Asymmetric thermal zones or even non-rectangular structures are common in residential buildings. These types of structures are not easy to model with specialized programs, and it is difficult to know the heat flows and the relationships between the different variables. This paper presents a methodology for modeling structures with multiple thermal zones using the graph theory arrangement. The methodology allows for generating a mathematical model using all the walls of each thermal zone. The modeling method uses the lumped parameter technique with a structure of two resistors and two capacitors for each thermal zone. The walls and internal surfaces of each zone define the thermal resistances, and the elements for the network structure are created by reducing resistances. The structure selected as a case study is similar to a residential apartment, which demonstrates the possibility of modeling complex and non-traditional structures. The accuracy of the generated mathematical model is v... [more]
Thermal Impact of 5G Antenna Systems in Sandwich Walls
Tao Lu, Lauri Vähä-Savo, Xiaoshu Lü, Katsuyuki Haneda
April 18, 2023 (v1)
Keywords: 5G antenna walls, 5G passive antenna system, ISO 6946 combined method, isothermal planes method, numerical modeling, parallel path method, sandwich wall, thermal transmittance
The 5th generation (5G) cellular networks offer high speeds, low latency, and greater capacity, but they face greater penetration loss through buildings than 4G due to their higher frequency bands. To reduce this loss in energy-efficient buildings, a passive antenna system was developed and integrated into sandwich walls. However, the thermal effects of this system, which includes highly thermally conductive metals, require further study. In this research, three-dimensional heat transfer simulations were performed using COMSOL Multiphysics to determine the thermal transmittances (U-values) of 5G antenna walls. The results revealed that, using stainless steel as the connector material (current design), the U-value rose from 0.1496 (for the wall without antenna) to 0.156 W/m2K, leading to an additional heating loss per year of only 0.545 KWh/m2 in Helsinki. In contrast, with the previous design that used copper as the connector material, the U-value increased dramatically to 0.3 W/m2K, e... [more]
Comparative Analysis of Isochoric and Isobaric Adiabatic Compressed Air Energy Storage
Daniel Pottie, Bruno Cardenas, Seamus Garvey, James Rouse, Edward Hough, Audrius Bagdanavicius, Edward Barbour
April 18, 2023 (v1)
Keywords: ACAES, isobaric CAES, thermodynamic analysis, thermomechanical energy storage
Adiabatic Compressed Air Energy Storage (ACAES) is regarded as a promising, grid scale, medium-to-long duration energy storage technology. In ACAES, the air storage may be isochoric (constant volume) or isobaric (constant pressure). Isochoric storage, wherein the internal pressure cycles between an upper and lower limit as the system charges and discharges is mechanically simpler, however, it leads to undesirable thermodynamic consequences which are detrimental to the ACAES overall performance. Isobaric storage can be a valuable alternative: the storage volume varies to offset the pressure and temperature changes that would otherwise occur as air mass enters or leaves the high-pressure storage. In this paper we develop a thermodynamic model based on expected ACAES and existing CAES system features to compare the effects of isochoric and isobaric storage. Importantly, off-design compressor performance due to the sliding storage pressure is included by using a second degree polynomial fi... [more]
Methodology for the Development of Virtual Representations within the Process Development Framework of Energy Plants: From Digital Model to Digital Predictive Twin—A Review
Martin Hammerschmid, Daniel Cenk Rosenfeld, Alexander Bartik, Florian Benedikt, Josef Fuchs, Stefan Müller
April 18, 2023 (v1)
Keywords: digital twin, process development, process simulation, Renewable and Sustainable Energy, virtual representation
Digital reflections of physical energy plants can help support and optimize energy technologies within their lifecycle. So far, no framework for the evolution of virtual representations throughout the process development lifecycle exists. Based on various concepts of virtual representations in different industries, this review paper focuses on developing a novel virtual representation framework for the process development environment within the energy sector. The proposed methodology enables the continuous evolution of virtual representations along the process development lifecycle. A novel definition for virtual representations in the process development environment is developed. Additionally, the most important virtual representation challenges, properties, and applications for developing a widely applicable framework are summarized. The essential sustainability indicators for the energy sector are listed to standardize the process evaluation throughout the process development lifecy... [more]
Numerical Modelling of Steam Superheaters in Supercritical Boilers
Katarzyna Węglarz, Dawid Taler, Jan Taler, Mateusz Marcinkowski
April 18, 2023 (v1)
Keywords: live steam superheater, mathematical model, pressure distribution, supercritical steam boiler, wall temperature distribution
This paper presents a numerical model of a four-pass supercritical steam superheater with a complex flow system. The specific heat of steam is a function of temperature and pressure, and the specific heat of flue gas is a function of temperature. Pressure and temperature changes along the length of the tubes were also determined. The modified Churchill equation was used to calculate the steam-side friction factor of Darcy−Weisbach. The flue gas temperature variations behind the individual superheater tube rows were calculated. The steam and wall temperature distributions were determined in each tube row along its length. Knowing the temperature of the tube walls and the steam along the flow direction enables the selection of the correct steel grade for the tubes. Thanks to this advantage of the proposed method, the investment can be reduced in superheater construction without the danger of overheating the tube material. The results of the superheater simulation were compared with the r... [more]
A Tensile Rotary Airborne Wind Energy System—Modelling, Analysis and Improved Design
Oliver Tulloch, Hong Yue, Abbas Mehrad Kazemi Amiri, Roderick Read
April 18, 2023 (v1)
Keywords: airborne wind energy (AWE), multi-spring dynamic model, optimisation design, rotary kite turbine, spring-disc dynamic model, steady-state TRPT model, system analysis, tensile rotary power transmission (TRPT), tether drag model
A unique rotary kite turbine designed with tensile rotary power transmission (TRPT) is introduced in this work. Power extraction, power transmission and the ground station are modelled in a modular framework. The TRPT system is the key component of power transmission, for which three models with different levels of complexity are proposed. The first representation is based on the stationary state of the system, in which the external and internal torques of a TRPT section are in equilibrium, referred to as the steady-state TRPT model. The second representation is a simplified spring-disc model for dynamic TRPT, and the third one is a multi-spring model with higher degrees of freedom and more flexibility in describing TRPT dynamics. To assess the torque loss on TRPT, a simple tether drag model is written for the steady-state TRPT, followed by an improved tether drag model for the dynamic TRPT. This modular framework allows for multiple versions of the rotor, tether aerodynamics and TRPT... [more]
An Aero-Structural Model for Ram-Air Kite Simulations
Paul Thedens, Roland Schmehl
April 18, 2023 (v1)
Keywords: airborne wind energy, dynamic relaxation, fluid-structure interaction, ram-air kite, SkySails Power, virtual wind tunnel
Similar to parafoils, ram-air kites are flexible membrane wings inflated by the apparent wind and supported by a bridle line system. A major challenge in estimating the performance of these wings using a computer model is the strong coupling between the airflow around the wing and the deformation of the membrane structure. In this paper, we introduce a staggered coupling scheme combining a structural finite element solver using a dynamic relaxation technique with a potential flow solver. The developed method proved numerically stable for determining the equilibrium shape of the wing under aerodynamic load and is thus suitable for performance measurement and load estimation. The method was validated with flight data provided by SkySails Power. Measured forces on the tether and steering belt of the robotic kite control pod showed good resemblance with the simulation results. As expected for a potential flow solver, the kite’s glide ratio was overestimated by 10−15%, and the measured teth... [more]
Comprehensive Thermodynamic Evaluation of the Natural Gas-Fired Allam Cycle at Full Load
Lorenzo Colleoni, Alessio Sindoni, Silvia Ravelli
April 18, 2023 (v1)
Keywords: Allam cycle, decarbonization, net electric efficiency, thermodynamic modeling
In this study, thermodynamic modeling and simulations were used to optimize the design point performance of the Allam cycle. The topic fits perfectly with the strategies for power sector decarbonization toward net zero emission. In fact, it offers an environmentally friendlier alternative to natural gas combined cycle (NGCC) plants. The focus is on oxyfuel combustion that, combined with supercritical CO2 (sCO2) stream as working fluid, produces high-purity CO2, electricity, and water by means of a highly recuperated Brayton cycle. The former is ready for sequestration, pipeline injection, or other applications, such as enhanced oil recovery or industrial processes. Being designed within the last decade, large-scale plants are poorly documented in the published literature and not yet ready for operation. Accordingly, a thermodynamic model was developed for a net power (Pn) output of 300 MW. After validation against the little data available from academic studies, simulation sets were co... [more]
Cooperative Game-Based Collaborative Optimal Regulation-Assisted Digital Twins for Wide-Area Distributed Energy
Pengcheng Ni, Zhiyuan Ye, Can Cao, Zhimin Guo, Jian Zhao, Xing He
April 18, 2023 (v1)
Keywords: collaborative optimal control, cooperative game, digital twins, wide-area distributed energy
With the wide use of renewable energy sources and the requirement for energy storage technology, the field of power systems is facing the need for further technological innovation. This paper proposes a wide-area distributed energy model based on digital twins. This model was constructed to more fully optimize the coordination of wide-area distributed energy in order to rationally deploy and utilize new energy units. Moreover, the minimization of the power deviation between the dispatch command and the actual power regulation output was also taken into account. In contrast to previous dispatch research, the cooperative game co-optimization algorithm was applied to this model, enabling a distributed approach that can quickly obtain a high-quality power command scheduling scheme. Finally, the simulation and comparison experiments using this algorithm with the wide-area distributed energy (WDE) model showed that it had the advantages of significantly reducing the tracking error, average e... [more]
Comparative Study of the Transmission Capacity of Grid-Forming Converters and Grid-Following Converters
Bojun Kong, Jian Zhu, Shengbo Wang, Xingmin Xu, Xiaokuan Jin, Junjie Yin, Jianhua Wang
April 18, 2023 (v1)
Keywords: grid-following converter, grid-forming converter, power coupling, short circuit ratio, static power transmission limit
The development trend of high shares of renewables and power electronics has increased the demand for new energy converters in the power system, but there is a lack of systematic research on the stability of different types of converters when transmitting power, which is worth exploring in depth. In this study, the power transfer capabilities of grid-forming and grid-following converters are investigated separately through an equivalent circuit diagram and phasor diagram when connected to the grid, and a quantitative relationship between converters’ power transmission limit and short circuit ratio under static stability conditions is obtained, leading to the conclusion that, in terms of power transmission, grid-forming converters are more suitable for weak grids with high damping and low inertia, whereas grid-following converters are more suitable for strong grids with high inertia. The conclusions are further verified by constructing the converter grid-connected models for different g... [more]
Demonstration of Pronghorn’s Subchannel Code Modeling of Liquid-Metal Reactors and Validation in Normal Operation Conditions and Blockage Scenarios
Vasileios Kyriakopoulos, Mauricio E. Tano, Aydin Karahan
April 18, 2023 (v1)
Keywords: blockage, LMFR, MOOSE, Pronghorn, SFR, subchannel, validation
Pronghorn-SC is a subchannel code within the Multiphysics Object-Oriented Simulation Environment (MOOSE). Initially designed to simulate flows in water-cooled, square lattice, subchannel assemblies, Pronghorn-SC has been expanded to simulate liquid-metal-cooled flows in triangular lattices, hexagonal subchannel assemblies. For this purpose, the algorithm of Pronghorn-SC was adapted to solve the subchannel equations as they are applicable to a hexagonal wire-wrapped sodium-cooled fast reactor. Cheng−Todreas models for pressure drop and cross-flow models were adopted and a coolant heat conduction term was added. To solve these equations, an improved implicit algorithm was developed robust enough to deal with the numerical issues, associated with low flow and recirculation phenomena. To confirm the prediction capability of Pronghorn-SC, calculations and comparisons with available experimental data of 19- and 37-pin assemblies were performed, as well as other subchannel codes. Finally, a f... [more]
A Direct Numerical Simulation Assessment of Turbulent Burning Velocity Parametrizations for Non-Unity Lewis Numbers
Vishnu Mohan, Marco Herbert, Markus Klein, Nilanjan Chakraborty
April 18, 2023 (v1)
Keywords: direct numerical simulations, flame surface area, Lewis number, turbulent burning velocity, turbulent premixed Bunsen flame
The predictions of turbulent burning velocity parameterizations for non-unity Lewis number flames have been assessed based on a single-step chemistry Direct Numerical Simulation (DNS) database of premixed Bunsen flames for different values of characteristic Lewis numbers ranging from 0.34 to 1.2. It has been found that the definition of the turbulent burning velocity is strongly dependent on the choice of projected flame brush area in the Bunsen burner configuration. The highest values of normalized turbulent burning velocity are obtained when the projected flame brush area is evaluated using the area of the isosurface of the Reynolds averaged reaction progress variable of 0.1 out of different options, namely the Favre averaged and Reynolds averaged isosurfaces of reaction progress variable of 0.5 and integral of the gradient of Favre and Reynolds averaged reaction progress variable. Because of the axisymmetric nature of the mean flame brush, the normalized turbulent burning velocity h... [more]
The Induction Motor MRAS-Based Speed Estimator Capable of Modelling the Slip Frequency Dependent Variability of the Rotor Impedance
Grzegorz Utrata, Jaroslaw Rolek
April 18, 2023 (v1)
Keywords: deep-bar effect, equivalent circuit, induction motors, MRAS, speed estimation
Speed feedback is indispensable not only for closed-loop controlled induction motors (IM) but also for the state monitoring systems of open-loop controlled IMs. Replacing speed sensors with speed estimations has many advantages including, e.g., hardware complexity reduction, sensor cabling elimination, and reduction of IM drive costs. From the various methods for IM speed estimation proposed in the literature, the model reference adaptive system (MRAS)-based speed estimator stands out because of its straightforward synthesis technique and lower computational complexity. On the other hand, this estimator is inherently sensitive to mismatching of IM equivalent circuit parameters. During transients, when the slip frequency cannot be temporarily controlled over the assumed operating point, rotor impedance varies with the slip frequency changes. This phenomenon is even more significant for open-loop controlled high-slip IMs (NEMA design D IMs), which operate under the cycling load like in,... [more]
Analysis of Improved In-Cylinder Combustion Characteristics with Chamber Modifications of the Diesel Engine
Arun Teja Doppalapudi, Abul Kalam Azad, Mohammad Masud Kamal Khan
April 18, 2023 (v1)
Keywords: CFD analysis, combustion chamber modification, combustion simulation, cylinder temperature, heat release rate
This study numerically analyses the effects of chamber modifications to investigate the improvement of in-cylinder combustion characteristics of the diesel engine using a computational fluid dynamics (CFD) approach. Five different modified chambers, namely, the double swirl combustion chamber (DSCC), bathtub combustion chamber (BTCC), double toroidal re-entrant combustion chamber (DTRCC), shallow depth combustion chamber (SCC), and stepped bowl combustion chamber (SBCC) were developed and compared with a reference flat combustion chamber (FCC). The effects of chamber modifications on temperature formation, velocity distribution, injection profiles, and in-cylinder turbulent motions (swirl and tumble ratio) were investigated. During the compression stroke, near top dead centre, the SCC showed a peak temperature of 970 K, followed by the FCC (968 K), SBCC (967 K), and DTRCC (748 K to 815 K). The DSCC and the SCC showed a high swirl ratio above 0.6, whereas the DTRCC and the BTCC showed a... [more]
Machine Learning Algorithms for Lithofacies Classification of the Gulong Shale from the Songliao Basin, China
Mingqiu Hou, Yuxiang Xiao, Zhengdong Lei, Zhi Yang, Yihuai Lou, Yuming Liu
April 18, 2023 (v1)
Keywords: ensemble methods, Gulong sag, machine learning models, random forest, shale lithofacies, Songliao basin, well log, XGBoost
Lithofacies identification and classification are critical for characterizing the hydrocarbon potential of unconventional resources. Although extensive applications of machine learning models in predicting lithofacies have been applied to conventional reservoir systems, the effectiveness of machine learning models in predicting clay-rich, lacustrine shale lithofacies has yet to be tackled. Here, we apply machine learning models to conventional well log data to automatically identify the shale lithofacies of Gulong Shale in the Songliao Basin. The shale lithofacies were classified into six types based on total organic carbon and mineral composition data from core analysis and geochemical logs. We compared the accuracy of Multilayer Perceptron (MLP), Support Vector Machine (SVM), Extreme Gradient Boosting (XGBoost), and Random Forest models. We mitigated the bias of imbalanced data by applying oversampling algorithms. Our results show that ensemble methods (XGBoost and Random Forest) hav... [more]
A Literature Review on Methods and Metrics for the Analysis of Outdoor Air Displacement Conditions in the Urban Environment
Ritesh Wankhade, Giovanni Pernigotto, Michele Larcher
April 18, 2023 (v1)
Keywords: Computational Fluid Dynamics, natural ventilation, street canyon, turbulence models, urban building design, urban ventilation, urban ventilation metrics, wind tunnel
The ongoing pandemic has driven the attention of both policy makers and professionals of the building sector towards the need for proper ventilation of the indoor environment. Despite accurate ventilation control only being available with mechanical ventilation systems, in several countries worldwide the renovation of indoor air relies mainly on natural solutions. In this context, in the design of new or renovated buildings, conventional natural ventilation rates are typically assumed to be in agreement with available technical standards, sometimes regardless of the actual external conditions. For instance, local wind speed and direction, as well as buoyancy-driven air displacements, are not considered, even if they can significantly affect the ventilation efficacy for the designed buildings. Moreover, the local outdoor temperature and the presence of pollutants are rarely accounted for, even though they can represent interesting inputs not only for naturally ventilated buildings but a... [more]
Analysis of Surrogate Models for Vapour Transport and Distribution in a Hollow Fibre Membrane Humidifier
Markus Pollak, Philipp Bekemeyer, Nicholas Lemke, Wilhelm Tegethoff, Juergen Koehler
April 18, 2023 (v1)
Keywords: Computational Fluid Dynamics, experiment, mass transfer, membrane humidifier, POD, Surrogate Model
To achieve high efficiency and low degradation of a polymer electrolyte fuel cell (PEMFC), it is necessary to maintain an appropriate level of humidification in the fuel cell membrane. Thus, membrane humidifiers are typically used in PEMFC systems. Parameter studies are important to evaluate membrane humidifiers under various operating conditions to reduce the amount of physical tests. However, simulative studies are computationally expensive when using detailed models. To reduce the computational cost, surrogate models are set up. In our study, a 3D computational fluid dynamics (CFD) model of a hollow fibre membrane humidifier is presented and validated using measurement data. Based on the results of the validated CFD model, a surrogate model of the humidifier is constructed using proper orthogonal decomposition (POD) in combination with different interpolation methods. To evaluate the surrogate models, their results are compared against reference solutions from the CFD model. Our res... [more]
Study of Electromagnetic Characteristics of Brushless Reverse Claw-Pole Electrically Excited Generators for Automobiles
Yufeng Zhang, Mingling Gao, Lei Wang, Xueyi Zhang, Mingjun Xu, Wenjing Hu, Luyao Wang
April 18, 2023 (v1)
Keywords: electric generators, induced electric potential, reverse claw pole, vehicle
A new type of brushless reverse claw-pole electrically excited generator is proposed for the problems of the low sine degree of the induced electromotive force waveform and the high harmonic content of the output voltage of the conventional electrically excited claw-pole generator. The design uses the equivalent magnetic network method to establish the equivalent magnetic circuit model of the motor and determines the equation for calculating the magnetoresistance of the isosceles trapezoidal variable section claw-pole structure. It derives the mathematical model of the no-load induced electric potential of the generator and completes to optimize the motor parameters with the no-load induced electric potential as the target. This study shows that the brushless reverse claw-pole electrically excited generator has the advantages of uniform magnetic field distribution, high harmonic fundamental amplitude of induced electromotive force and low harmonic content. It can better meet the applic... [more]
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