Viorel Ionescu

Ovidius University

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Co-Authors

J. Kern

University of Fribourg

Anişoara-Arleziana Neagu

Ovidius University

S. Drissi

University of Fribourg

Ioan Stamatin

University of Bucharest

Nicolae Buzbuchi

Constanta Maritime University

A. Bruder

University of Fribourg

Valentin Girleanu

University of Bucharest

A. Andronie

Politecnico di Milano

Eugeniu Vasile

Universitatea Națională de Știință și Tehnologie Politehnica București

M. Grecescu

Institute of Radiation Physics

Cooperative Institutions

University of Fribourg

University of Bucharest

Institute for Nuclear Research Pitesti

Universitatea Națională de Știință și Tehnologie Politehnica București

Institutul de Fizică Atomică

University of Pitesti

Institut National de Physique Nucléaire et de Physique des Particules

Centre National de la Recherche Scientifique

Université Joseph Fourier

National Institute for Laser Plasma and Radiation Physics

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Numerical Investigation of a MEMS Thermal Actuator Performance by Modifying its Geometric Dimensions

Procedia Manufacturing (2019)

Viorel Ionescu

Mechanical displacement and thermal stress investigation of a two hot arm thermal microactuator (polysilicon type) with different structural and geometrical parameters was investigated in this paper with Comsol Multiphysics software, starting from a validation model based on the real dimensions of a two hot arm thermal microactuator, experimentally tested at different actuation voltages. Variation at different actuation voltages (between 1 and 9 V) for the radiative energy received by the cold arm from the short hot arm and the ratio between the resistive heat energy and radiative energy at different cold arm widths dw with gap between arms g = 2 µm, and respectively at different gap widths g with dw = 15 µm was numerically computed here. Total displacement versus actuation voltages for the actuator models was also evaluated, along with von Mises stress and temperature distributions for identification of maximum bending stress along the inner (short) hot arm of the actuator.

Microactuator

Multiphysics

Resistive touchscreen

Bowing

10.1016/j.promfg.2019.02.290

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Citations (10)

Investigation of the Energy Conversion Efficiency for a Thermoelectric Generator System with Forced Convection Cooling

Viorel Ionescu Anişoara-Arleziana Neagu

This study experimentally evaluates thermal and electrical characteristics of a thermoelectric generator (TEG) based energy system. TEG module will convert a part of the thermal energy generated by a heating element into electrical power when a temperature gradient $\Delta\mathrm{T}$ is established between its cold and hot plates. This energy conversion system also contains a finned plate heatsink with a cooling fan and one 12V DC/120oC aluminum PTC heating element used here to simulate the thermal behavior of a microprocessor unit with fast temperature increasing under load. Some critical parameters of this thermoelectric system, like the hot and cold TEG temperatures, the output current and voltage, TEG output power and energy conversion efficiency, were analyzed in detail. The control variable considered was the load resistance, modified at values between 1 $\Omega$ and 40 $\Omega$ .

Thermoelectric generator

Thermal energy

10.1109/emes58375.2023.10171737

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Thermal-hydraulic analysis of a louver fin-and-tube radiator for a liquid–cooled PEMFC stack system

Analele Universităţii "Ovidius" Constanţa. Seria Chimie/"Ovidius" University Annals of Chemistry (2024)

Viorel Ionescu

Abstract The present study aimed to develop a parametric analysis from the perspective of heat transfer and dimensionless pressure drop for a cross-flow heat exchanger with louvered fins and flat tubes. Four different radiator core models were considered here, with specific values of geometrical parameters as selected from the manufacturer’s datasheets. Effectiveness – the NTU (Number of Transfer Units) method was used to evaluate the total heat flux transferred between the cold and hot sides of the radiator. A possible application of the designed louvered fin radiator can be as a part of a liquid–cooling system for an automotive Proton Exchange Membrane Fuel Cell (PEMFC) stack with coolant flow rates of 1 l/min and 2 l/min, frontal air velocities up to 14 m/s and inlet temperatures for the coolant and air side of 343 K and 298 K, respectively. One of the radiator models investigated, having the lowest louver pitch to fin pitch ratio, highest fin length to fin pitch ratio and lowest louver length, showed the best thermo–hydraulic performance, with the highest surface goodness factor values along the entire Reynolds number domain.

Louver

Radiator (engine cooling)

Fin

Thermal hydraulics

10.2478/auoc-2024-0015

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A Study of the Influence of Gas Channel Parameters on HT-PEM Fuel Cell Performance Using FEM Analysis

MATEC Web of Conferences (2016)

Viorel Ionescu Nicolae Buzbuchi

Proton Exchange Membrane Fuel Cells (PEMFC) are highly efficient power generators, achieving up to 50–60% conversion efficiency, even in sizes of a few kilowatts. Comsol Multiphysics, a commercial solver based on the Finite Element Method (FEM) was used for developing a three dimensional model of a high temperature PEMFC that can deal with both anode and cathode flow field for examining the micro flow channel with electrochemical reaction. Cathode gas flow velocity influence on the cell performance was investigated at first. Polarization curves for three different channel widths (0.8, 1.6 and 2.4 mm) and three different channel depths (1, 2 and 3 mm) were computed at a cathode inlet flow velocity of 0.06 m/s. Oxygen molar concentration at cathode catalyst layer-GDL channel interface and local current density variation along the cell length were also studied for specific gas channel geometries.

Multiphysics

Concentration polarization

10.1051/matecconf/20167712001

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Optimal design of mushroom-like EBG structures for antenna mutual coupling reduction in 2.4 GHz ISM band

2022 E-Health and Bioengineering Conference (EHB) (2015)

Viorel Ionescu Mihaela Hnatiuc Adrian Topala

A double element 900 bent monopole antenna system with mushroom-like electromagnetic band-gap (EBG) structures introduced between elements has been studied in this paper using a Finite Element Method (FEM) in order to demonstrate the concept of EBG mutual decoupling. The EBG structures were designed to have a band gap centered around the bandstop frequency of 2.45 GHz. The mutual coupling coefficient s21 was simulated over a range of frequencies around the band gap for some specific designs and electric field distribution on XY plane for optimal EBG design was also computed. Inserting a number of five EBG unit cells with patch sizes of 8 mm, gap between patches of 4 mm and vias cross sectional area of 3.515 mm2, the mutual coupling between antennas improved from -24 dB to -37.4 dB at bandstop resonance frequency of 2.45 GHz.

Decoupling (probability)

10.1109/ehb.2015.7391559

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Citations (8)

Injection of a sheet relativistic electron beam into a plasma

Revue roumaine de physique (1978)

Viorel Ionescu

Relativistic electron beam

Fact sheet

Plasma sheet

Relativistic plasma

Source

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Performance analysis of thermoelectric power-generation system with natural convection cooling

Energy Reports (2023)

Viorel Ionescu

Nowadays, high-performance electronic devices release large amounts of heat throughout their operation. Thermoelectric passive cooling systems can offer a cost-efficient and straightforward solution for the thermal management of such devices based on a passive heatsink and a thermoelectric generator (TEG). TEG can transform a part of the heat generated by the electronic chip into electricity for the power supply of microelectronic systems. The thermoelectric system investigated here contains a 12 W Positive Temperature Coefficient (PTC) heating element placed on a 4 × 4 cm2 aluminium plate, a commercial SP1848-27145 TEG device and a finned plate heatsink recycled from a desktop PC. Two types of tests were performed here. An energy efficiency test was initiated at different load resistance values RL between 1 and 40 Ω by directly connecting TEG output to a direct current (DC) electronic load. The second test was developed for electrical power generation at 3.3 V–5 V by integrating a DC–DC boost converter between the TEG output and the electronic load set at RL of 600–900 Ω. It was registered a maximum energy conversion efficiency of 1.17 % for RL=2Ω, close to the internal resistance value of the TEG module. The second test revealed the generation of output electrical powers with minimum values of 15–17.5 mW at a temperature difference between TEG plates of about 20 K.

Thermoelectric generator

Thermoelectric cooling

Internal resistance

10.1016/j.egyr.2022.12.105

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Citations (6)

PEMFC Two-dimensional FEM Model to Study the Effects of Gas Flow Channels Geometry on Reactant Species Transport

Energy Procedia (2017)

Viorel Ionescu Nicolae Buzbuchi

A proton exchange membrane (PEM) fuel cell has many distinctive features, like quick start-up, high power density, zero emissions and system robustness, which makes it an attractive alternative clean energy source. Comsol Multiphysics, a commercial solver based on the Finite Element Method (FEM) was used here for developing a two dimensional cross-the-channel (CTC) and through-the-membrane (TTM) model of a low temperature Proton Exchange Membrane Fuel cell (LT-PEMFC), based on the agglomerate model for cathode catalyst layer. The transport of all three types of reacting species (electrons, ions and chemical species) participating in the electrochemical reaction within the catalyst layer was considered in this model. The effect of bipolar plate geometry (channel land/rib ratio) has been investigated here since the pathway for electron transport is affected by the land area in contact with the Gas Diffusion Layer(GDL) as a macro-scale fuel cell feature.

Multiphysics

Agglomerate

10.1016/j.egypro.2017.03.1085

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Citations (7)

Simulating the Effect of Gas Channel Geometry on PEM Fuel Cell Performance by Finite Element Method

Procedia Technology (2016)

Viorel Ionescu

Proton exchange membrane fuel cells (PEMFC) become in the last years an attractive alternative clean energy source and the main researches are oriented in order to understand how different cell parameters affects the performance of the fuel cell in real operating conditions and subsequently reduce the cost involved in prototype development. Comsol Multiphysics, a commercial solver based on the Finite Element Method (FEM) was used for developing a three dimensional model of PEMFC working at a high temperature of 150 ̊C. Cathode gas flow velocity influence on the cell performance was investigated at first. The effect of channel width and channel height on the current density at a cell voltage of 0.5 V was established, at various cathode gas flow velocities between 0.04 and 0.42 m/s. Local current density variation for cell geometries with three different channel widths (0.8, 1.2 and 1.6 mm) at three different channel heights (1, 2 and 3 mm) were computed at a cathode inlet flow velocity of 0.1 m/s and cell voltage of 0.3 V. Oxygen and water molar concentrations at cathode catalyst layer-GDL channel interface were also studied for specific gas channel geometries.

Multiphysics

10.1016/j.protcy.2016.01.147

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Citations (3)

A simple one-dimensional model for analysis of a bipolar membrane used in electrodialysis desalination

Viorel Ionescu

This study developed a one-dimensional model for a bipolar membrane unit used in desalination stacks with the finite– element method (FEM) based Comsol Multiphysics software. The numerical model took into account the stationary transport of K⁺, Cl^-, H⁺ and OH^- ions inside a desalination channel unit using Nernst – Planck – Poisson equations and the Onsager theory of the Second Wien Effect for water dissociation under externally applied electrical fields. Electrochemical behaviour for the unit cell model was validated through the experimental current-voltage curve of a bipolar membrane, as it was reported in the literature. Influence of the anion–exchange layer (AEL) and cation–exchange layer (CEL) thickness variation and fixed charge concentration ratio in CEL/AEL regions upon specific desalination performance parameters, like co–ion leakage current, water dissociation turn-on voltage and water dissociation resistance were investigated here. Evolution of K⁺, Cl^-, H⁺ and OH^- ion concentration through specific compartments on the unit cell (electrolyte, AEL, CEL) at different potential drops across the membrane helped to understand the contribution of specific ionic fluxes at the total current through the system.

Limiting current

Multiphysics

10.1117/12.2643277

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