Carlos Lemos Antunes

Transient heating and cooling analysis in an electromagnetic device

This paper is concerned with the finite element formulation of the transient heating and cooling problem in an electromagnetic device. The formulation presented is illustrated with the temperature distribution produced in a large 3-phase induction motor with a closed-air-circuit ventilation scheme under different load and coolant velocity conditions. The eddy currents and the hysteresis losses contributions due to the temperature-rise were taken into account, as well as the linear dependency of the electric resistivity with temperature. The numeric results obtained were compared with the experimental values available, showing a very close agreement. >

Saline‐enhanced RF ablation on a cholangiocarcinoma: a numerical simulation

Purpose – Cholangiocarcinoma is an adenocarcinoma of the bile ducts which drain bile from the liver into the small intestine. Unfortunately, most patients are diagnosed at an advanced stage of the disease with almost no chances for surgery, the only potentially curative treatment. As nitinol stents can be used to reduce stricture problems of the bile duct, these can be also considered as potential electrodes for hyperthermia treatments. Previous works show that, in fact, these metallic stents might be used as part of a feasible solution for delivering radiofrequency (RF) energy into a tumor located in a hollow organ to destroy the tumor tissue. However, the tissue lesion induced is not completely uniform due to convective heat transfer associated to the blood flow in the nearby vessels. The purpose of this paper is to study the use of saline solution for modifying the electrical conductivity of the tissue in order to obtain a more uniform lesion.Design/methodology/approach – A numerical analysis using fin...

Influence of the neutral in the thermal performance of a three‐phase induction motor under unbalanced power supply using the finite element approach

In this paper the influence of the neutral in the thermal performance of a three‐phase squirrel cage induction motor fed by asymmetrical supply voltages is studied and analysed. A 2D finite element formulation was used to solve the steady‐state heat transfer problem. The eddy currents in the rotor bars were evaluated using a combined 3D finite element approach with analytical expressions. The numerical solutions are compared with measured experimental results obtained in laboratory tests for two load conditions and two unbalanced power supply situations with and without the neutral wire connected.

Using a tubular electrode for radiofrequency ablation: Numerical and experimental analysis

Purpose – Due to its good mechanical and biocompatibility characteristics, nitinol SEMS is a popular endoprothesis used for relieving stricture problems in hollow organs due to carcinomas. Besides its mechanical application, SEMS can be regarded as well as potential electrode for performing RF ablation therapy on the tumor. The purpose of this work is to perform numerical and experimental analyses in order to characterize the lesion volume induced in biological tissue using this kind of tubular electrode. Design/methodology/approach – Data concerning electrical conductivity and dimension of the damaged tissue after RF ablation procedure were obtained from ex vivo samples. Next, numerical models using 3D finite element method were obtained reassembling the conditions considered at experimentation setup and results were compared. Findings – Numerical and experimental results show that a regular volume of damaged tissue can be obtained considering this type of electrode. Also, results obtained from numerical simulation are close to those obtained by experimentation. Originality/value – SEMSs, commonly used as devices to minimize obstruction problems due to the growth of tumors, may still be considered as an active electrode for RF ablation procedures. A method considering this observation is presented in this paper. Also, numerical simulation can be regarded in this case as a tool for determining the lesion volume.In the last two decades radiofrequency ablation (RFA) has been considered a promising medical procedure for the treatment of primary and secondary malignancies. However, the needle-based electrodes so far developed for this kind of treatment are not suitable for the thermal ablation of tumors located in hollow organs like esophagus, colon or bile duct. In this work a tubular electrode solution is presented. Numerical and experimental analyses were performed to characterize the volume of the lesion induced. Results show that this kind of electrode is a feasible solution and numerical simulation might provide a tool for planning RFA procedure with some accuracy.

Thermal ablation in biological tissue using tubular electrode

In the last decade, the study of methodologies for heating biological tissue has been an area of most interest in biology and medicine. As a result, the number of electrode solutions has grown in the past years. In this work, we study the capability of using a tubular electrode for heating biological tissue. To test this possibility, liver samples ex-vivo were used and numerical simulations were made. The final results were compared and revealed satisfactory and promising use of tubular electrodes for this kind of application.

LMAT_SIMEL – The Electric Field Numerical Calculator of the Package LMAT_SIMX for Very High Voltage Power Lines

In this paper it is presented the software tool LMAT_SIMEL, the Electric Field numerical calculator for the package LMAT_SIMEX that allows the calculation and simulation of ELF electric and magnetic fields emanated from very high voltage power lines.

Effects of the geometry of a tubular electrode on the temperature distribution in biologial tissue

Tubular electrodes provide a practicable way for heating biological tissues, suitable for medical and biological applications. This kind electrode is made from interlaced nitinol wires, forming a flexible tube that can be easily folded. This paper presents a study concerning the impact of the mesh density on tissue heating.

EasyMAG – magnetic field toolbox calculator for electrical installation project

Purpose – This paper aims to present a software application, called EasyMAG, for simulating and calculating the magnetic field during the design of domestic/industrial electrical installations.Design/methodology/approach – From a CAD software 3D representation of the model, including the electric wiring and considering the current in the electrical circuits, the software evaluates the magnetic field intensity for power‐line frequencies at different heights.Findings – Two application examples are presented consisting of a cabling layout in a lab room with three phase illumination and power socket circuits and a computer room above a power transformer room. The results were compared with measured values showing a good agreement between them.Originality/value – Shows that with this software it is possible to anticipate areas where magnetic field values might reach abnormally high values and to analyze alternative wiring layouts in order to keep the magnetic field values as low as possible.

Chart and Expressions for Eddy Current Losses Calculation in Steel Laminations Derived from Finite Element Numerical Results in 2D

A chart and a set of expressions obtain ed from 2D Finite Element solutions are presented. These allow the 2D eddy current losses calculation for any steel lamination considering skin effect, thickness and width, in the linear zone of the magnetization curve. A comparison between the numerical results and the obtained by the proposed expressions shows a very good agreement.