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computational modeling of an Earth-Air Heat Exchanger Integrated with Phase Change Materials: A Case Study Performed for the Viamão City, Rio Grande do Sul State, Brazil

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Defect and Diffusion Forum 2023年 427卷 85-94页

作者： Vielma Vivas, Giovanni Antonio Rodrigues, Michel Kepes Alberto, Luiz Rocha, Oliveira Dos Santos, Elizaldo Domingues Silva Brum, Ruth da Isoldi, Liércio André Graduate Program in Computational Modeling Federal University of Rio Grande RS Rio Grande Brazil Graduate Program in Mathematical Modeling Federal University of Pelotas RS Pelotas Brazil

The earth-air heat exchanger (EAHE) is a sustainable option that allows the electrical energy consumption reduction in buildings. The objective of this study is to evaluate the influence of the incorporation of the thermal energy storage principle based on phase change materials (PCM) into the EAHE on its thermal potential. For this, a three-dimensional numerical model of the PCM coupled to the EAHE (EAHE-PCM) was developed based on the effective heat capacity method and adapted to the climatic conditions and soil characteristics of the Viamão city, Rio Grande do Sul State, Brazil. It was found that for a duct diameter and length of 0.11 m and 25.77 m, the incorporation of PCM to EAHE improved by 8.90% and 3.97% in the average annual thermal potential of heating and cooling, respectively. In addition, the average monthly thermal potential increased 19.70% (heating) and 8.48% (cooling), for the months of May and December, respectively, when the PCM was integrated into the system. © 2023 Trans Tech Publications Ltd, Switzerland.

关键词： Phase change materials

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Numerical Analysis of Phase Change Material Parameters on the Behavior of a Ground-Air Heat Exchanger

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Defect and Diffusion Forum 2024年 436卷 103-115页

作者： Vivas, Giovanni Antonio Vielma Rodrigues, Michel Kepes Rocha, Luiz Alberto Oliveira Dos Santos, Elizaldo Domingues Brum, Ruth da Silva Isoldi, Liércio André Graduate Program in Computational Modeling Federal University of Rio Grande RS Rio Grande Brazil Graduate Program in Mathematical Modeling Federal University of Pelotas RS Pelotas Brazil

The ground-air heat exchanger (GAHE) represents an eco-friendly solution for improving temperature conditions and, consequently, lowering the power demand in facilities. The aim of this research is to numerically analyze how the length and position of the phase change material (PCM) affect the behavior of the GAHE. To achieve this, a 3D computational simulation of the PCM integrated with the GAHE was employed, utilizing the equivalent heat capacity approach and tailored to the climate and ground properties of southern Brazil. This GAHE-PCM numerical model was created employing the finite volume method through the ANSYS Fluent program. From the obtained results, it was found that for a PCM length of 20.61 m, the incorporation of this material placed from the duct inlet offered an improvement of 13.37% in the average heating energy performance indicator (EPI) in the month of May, in contrast to the EPI value of 18.04% achieved when the PCM was added from the duct outlet. © 2024 Trans Tech Publications Ltd, All Rights Reserved.

关键词： Ducts

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Drivetrain simulation using variational autoencoders

arXiv

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arXiv 2025年

作者： Sharma, Pallavi Urrea-Quintero, Jorge-Humberto Bogdan, Bogdan Ciotec, Adrian-Dumitru Vasilie, Laura Wessels, Henning Skull, Matteo Porsche Engineering Etzelstraße 1 Bietigheim-Bissingen74321 Germany Graduate Program Computational Sciences in Engineering Technische Universität Braunschweig Braunschweig Germany Fraunhofer Institute for Energy Economics and Energy System Technology Joseph-Beuys-Straße 8 Kassel34117 Germany Institute of Applied Mechanics Division Data-Driven Modeling of Mechanical Systems Technische Universität Braunschweig Pockelsstraße 3 Braunschweig38106 Germany

This work proposes variational autoencoders (VAEs) to predict a vehicle’s jerk from a given torque demand, addressing the limitations of sparse real-world datasets. Specifically, we implement unconditional and conditional VAEs to generate jerk signals that integrate features from different drivetrain scenarios. The VAEs are trained on experimental data collected from two variants of a fully electric SUV, which differ in maximum torque delivery and drivetrain configuration. New meaningful jerk signals are generated within an engineering context through the interpretation of the VAE’s latent space. A performance comparison with baseline physics-based and hybrid models confirms the effectiveness of the VAEs. We show that VAEs bypass the need for exhaustive manual system parametrization while maintaining physical plausibility by conditioning data generation on specific inputs. © 2025, CC BY.

关键词： Signal encoding

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A strategy for parametrization refinement in the solution of a geometric inverse problem

A strategy for parametrization refinement in the solution of...

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Southern Conference on computational modeling

作者： Peters, Franciane Conceição Barra, Luis Paulo Da Silva Graduate Program on Computational Modeling Federal University of Juiz de Fora Juiz de Fora Brazil

ISBN: (纸本)9780769539768

This paper treats the problem of identifying a single inclusion in a conductor domain based on the knowledge of measured electrical potentials on the external boundary of the conductor body due to known injected electrical currents. The inclusion boundary is approximated by an Extended X-Spline, that allows identify inclusions with smooth or sharp boundary. In this work, the forward problem is solved by an implementation of the direct formulation of the Boundary Element Method (BEM) and the inverse one is solved by Levenberg-Marquardt method, which requires the evaluation of the objective function derivatives, here approximated by finite differences. This work presents a methodology to increase the number of optimization variables during the solution of the inverse problem in order to improve the quality of the results. © 2009 IEEE.

关键词： Boundary element method

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Some numerical results on the influence of measurement strategies and load patterns in the EIT inverse problem

Some numerical results on the influence of measurement strat...

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14th International Conference on Electrical Bioimpedance, Held in Conjunction with the 11th Conference on Biomedical Applications of EIT, ICEBI and EIT 2010

作者： Peters, Franciane C. Barra, Luis Paulo S. Federal University of Juiz de Fora Graduate Program on Computational Modeling CEP 36036-330 Minas Gerais Brazil

It is well known that the Electrical Impedance Tomography reconstructed images are very sensitive to noise in the electrical potential measures at the external boundary of the domain. Furthermore, there are a variety of strategies to inject current and measure these values. Thus, the aim of this work is to verify how much some of these strategies affect the quality of the reconstructed image and the sensitivity of each strategy to the existence of noise in the measured data. For a known position and shape of a single homogeneous inclusion inside a conductor domain, measured data is numerically simulated by the forward problem solution via Boundary Element Method (BEM). Sixteen electrodes placed at the outer boundary of the domain are used with different load patterns and measurement strategies to obtain the exact data for the numerical experiments. In order to simulate noisy data, Additive White Gaussian Noise proportional to the exact measured value is used on each potential measure. The inverse problem is treated as a data fitting problem solved via Levenberg-Marquardt method, that minimizes the difference between measures data and computed potential values. The coordinates of the control points of a spline function that defines the boundary of the inclusion are used as minimization parameters. In each step of this procedure, the computed potential values are obtained via BEM. The identification of inclusions of different sizes, shapes and positions is presented allowing some conclusions about the influence of the studied parameters. © 2010 IOP Publishing Ltd.

关键词： Boundary element method

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Performance Evaluation of Two Load Balancing Algorithms for Hybrid Clusters 13th

Performance Evaluation of Two Load Balancing Algorithms for ...

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13th International Conference on High Performance Computing in computational Science, VECPAR 2018

作者： do Nascimento, Tiago Marques dos Santos, Rodrigo Weber Lobosco, Marcelo Graduate Program on Computational Modeling UFJF Campus Universitário Juiz de ForaMG36036-900 Brazil

ISBN: (纸本)9783030159955

The use of hybrid environments, composed by CPUs and accelerators, imposes new challenges to the programmer that wants to use all the processing power available on the hardware. Although standards such as OpenCL and OpenACC can help in the task of writing parallel code for hybrid platforms, some issues remain open. In particular, multiprocessors and accelerators are different architectures and for this reason present distinct performances. As a result, data parallel applications have to find a data division that distributes the same amount of work to all devices, i.e, they have to finish their work in approximately the same time. This work uses a simulator of the Human Immune System (HIS) to evaluate two load balancing algorithms, a static and a dynamic ones, that can be used for this purpose. The results have shown that the dynamic load balancing algorithm outperforms the static one by a factor of upÂ to 1.07. © 2019, Springer Nature Switzerland AG.

关键词： Clustering algorithms

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Numerical Simulation of Vertical Helical Earth-Air Heat Exchangers: Multiobjective Performance Assessment

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Defect and Diffusion Forum 2024年 435卷 77-89页

作者： Razera, Andre Luis Vaz, Igor Silva Kepes Rodrigues, Michel Domingues Dos Santos, Elizaldo Oliveira Rocha, Luiz Alberto Isoldi, Liércio Andre School of Engineering Universidade Federal do Rio Grande Rio Grande RS Brazil Graduate Program in Computational Modeling Universidade Federal do Rio Grande Rio Grande RS Brazil

In the present study, a numerical evaluation of the thermal behavior of Vertical Helical Earth-Air Heat Exchangers (EAHE-VH) installations was conducted under representative climate and soil conditions of the city of Rio Grande, in southern Brazil. The Rectilinear Horizontal Earth-Air Heat Exchanger (EAHE-HR), traditionally employed, was used as a reference. The evaluated geometric variable was the pitch between the helicoids (Ph), and the performance was quantified bythe thermal potential of the system, allowing for quantitative comparisons between the different EAHEs through statistical indicators. Comparisons were also made with the Vertical Earth-Air Heat Exchanger with 3 U-shaped ducts (EAHE-V3U). As a result, the option of EAHE-VH with a pitch of 100 mm achieved superior performance of up to 20% compared to the other helical geometries studied. Additionally, it reached the result closest to the EAHE-HR considered as a reference. When compared to the EAHE-V3U, it showed lower results related to the annual thermal potential. However, it stood out for the need for a smaller volume of soil for its installation, with a reduction of 51.5% compared to the EAHE-V3U and 79.1% compared to the EAHE-HR. The multi objective analysis showed the ability of the EAHE-VH to simultaneously meet the objectives related to thermal potential and required volume for installation, making it the most viable option among the evaluated EAHE construction models when both purposes are equally important. © 2024 Trans Tech Publications Ltd, All Rights Reserved.

关键词： Air preheaters

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Four-phase Buck Converter Design and Thermal modeling Using FEA Simulation 14

Four-phase Buck Converter Design and Thermal Modeling Using ...

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14th Seminar on Power Electronics and Control, SEPOC 2022

作者： Eckhardt, Gustavo Lenz, Joao Manoel An Electrical Engineering Undergrad with A Scientific Initiation Scholarship at Unijuí Brazil Unijúi Brazil Mathematical and Computational Modeling Graduate Program Unijúi Brazil Brazil

ISBN: (数字)9781665470896

ISBN: (纸本)9781665470896

Equipment with high efficiency, high power density, reduced size and low cost are in demand in the automotive industry. This work presents a method to design and model a high power-density four-phase DC-DC Buck converter for an automotive application and using the components operating temperature as a design criteria. A parameter sweep is done to select the operating point of the DC-DC converter combined with an iterative method to select part numbers, where preference is given to components that are AEC-Qxxx qualified. The converter is modeled and power losses are computed in SPICE considering the parasitic elements present in the PCB and the dynamic characteristics and non-idealities of the electronic components;thermal modeling is performed using Ansys Icepak. The results indicate that the design meets all electrical and thermal requirements for an automotive application. An efficiency of 95.97% is obtained in a four-phase DC-DC Buck converter that supplies a total of 800 W to 4 loads, in a space of 43.77 cm3, that is, an estimated power density of 18.28 W/cm3. © 2022 IEEE.

关键词： Buck converter

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Performance analysis of stehfest and power series expansion methods for solution to diffusive and advective transport problems

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Defect and Diffusion Forum 2019年第1期396卷 99-108页

作者： Pilatti, Cristiana Do Amaral Rodriguez, Bárbara Denicol Filho, João Francisco Prolo Graduate Program in Computational Modeling Federal University of Rio Grande Rio Grande Rio Grande do Sul Brazil Institute of Mathematics Statistics and Physics Federal University of Rio Grande Rio Grande Rio Grande do Sul Brazil

This paper presents results of the test of methods for numerical inversion of the Laplace Transform for solving the one-dimensional advection-diffusion equation, which describes solute transport processes, focusing on the contaminant transport in a porous medium. The performance of Stehfest and Power Series Expansion methods is analyzed, for diffusion-dominated and advectiondominated transport problems under linear flow condition. Numerical results are compared to the analytical solution by means of the absolute error. Based on these results, we concluded that both methods, Stehfest and Power Series Expansion, are recommended only for diffusion-dominated cases. © 2019 Trans Tech Publications Ltd, Switzerland.

关键词： Laplace transforms

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Geometrical evaluation of a pair of elliptical tubes subjected to a flow with forced convection heat transfer

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Defect and Diffusion Forum 2019年第1期396卷 155-163页

作者： Del Aghenese, Ana Paula Heinemann, Eliander Manke De Avila Barreto, Gabriel Teixeira, Filipe Branco Isoldi, Liércio André Rocha, Luiz Alberto Oliveira Dos Santos, Elizaldo Domingues Graduate Program in Computational Modeling Universidade Federal Do Rio Grande Rio Grande RS Brazil School of Engineering Universidade Federal Do Rio Grande Rio Grande RS Brazil Graduate Program of Mechanical Engineering Federal University of Rio Grande Do sul Porto Alegre RS Brazil Graduate Program of Mechanical Engineering Universidade Do Vale Do Rio Dos Sinos São Leopoldo RS Brazil

In the present work it is performed a study on the geometric evaluation of a pair of elliptical tubes subjected to external flow with forced convection by means of numerical approach. The objectives are the maximization of Nusselt number (NuD) and the minimization of drag coefficient (CD). The degrees of freedom for the pair of tubes arrangement are: The ratio between the transverse pitch and characteristic length of tubes (ST/D), where D = (A)1/2, the ratio of the main and secondary axes of the elliptical tube (a/b) and the angle of incidence of the flow on the pair of tubes (α). The simulations were carried out considering two-dimensional forced convective flows, in the laminar regime and incompressible conditions. For all configurations, Reynolds and Prandtl numbers are constant, ReD = 100 and Pr = 0.71. The Finite Volume Method (FVM) is used to solve conservation equations of mass, momentum and energy. The software Gmsh is used for creation of the geometries and generation of the meshes. Results showed that the degrees of freedom affected the fluid dynamic and thermal performance of the forced convective flow. According to the objectives outlined in this study, the best performance for the maximization of heat transfer was obtained when α = 0°, a/b = 1/2 and ST/D = 3.5. In the case of the fluid dynamics study, the optimal result for CD minimization occurred when α = 0°, a/b = 2.0 and ST/D = 4.0. Thus, the optimal geometry will depend on the indicator performance where the problem is evaluated. © 2019 Trans Tech Publications Ltd, Switzerland.

关键词： Forced convection

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