Cegep de lOutaouais

Gatineau, Canada

Cegep de lOutaouais

Gatineau, Canada
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Amaral C.,Federal University of Uberlandia | Brandao C.,Carleton University | Sempels E.V.,Ecole Polytechnique de Montréal | Lesage F.J.,Cegep de lOutaouais | Lesage F.J.,McMaster University
Applied Thermal Engineering | Year: 2014

Due to an abundance of low cost waste-heat in the industrial and residential sector, many studies in recent years have focused on applications of low grade heat for local energy needs. These include heat reutilization, thermal conversion to mechanical energy and thermal conversion to electricity. The thermoelectric effect presents a promising potential for effective conversion of low grade waste-heat yet is currently limited in application due to a conversion efficiency that is not cost effective. The present work focuses on mechanical methods to improve the thermal tension driving the electromotive force responsible for thermoelectric power production. More specifically, flow impeding geometries are inserted into the flow channels of a liquid-to-liquid thermoelectric generator thereby enhancing the heat transfer near its embedded thermoelectric modules. Consequentially, the thermal dipole across the modules is increased improving the overall power output. Care is taken to measure the adverse pressure drop caused by the use of the flow impeding geometries in order to evaluate the net power output. This net thermoelectric power output is measured, reported and discussed for a fixed inlet temperature difference, a fixed electrical load, varying flow rates and varying insert geometries. © 2014 Elsevier B.V. All rights reserved.


Lachance M.,Cegep de l'Outaouais | Lachance M.,University of Strasbourg | Longtin A.,University of Strasbourg | Morris C.E.,Ottawa Hospital Research Institute | And 2 more authors.
Journal of Computational Neuroscience | Year: 2014

Neural tissue injuries render voltage-gated Na+channels (Nav) leaky, thereby altering excitability, disrupting propagation and causing neuropathic pain related ectopic activity. In both recombinant systems and native excitable membranes, membrane damage causes the kinetically-coupled activation and inactivation processes of Nav channels to undergo hyperpolarizing shifts. This damage-intensity dependent change, called coupled left-shift (CLS), yields a persistent or “subthreshold” Nav window conductance. Nodes of Ranvier simulations involving various degrees of mild CLS showed that, as the system’s channel/pump fluxes attempt to re-establish ion homeostasis, the CLS elicits hyperexcitability, subthreshold oscillations and neuropathic type action potential (AP) bursts. CLS-induced intermittent propagation failure was studied in simulations of stimulated axons, but pump contributions were ignored, leaving open an important question: does mild-injury (small CLS values, pumps functioning well) render propagation-competent but still quiescent axons vulnerable to further impairments as the system attempts to cope with its normal excitatory inputs? We probe this incipient diffuse axonal injury scenario using a 10-node myelinated axon model. Fully restabilized nodes with mild damage can, we show, become ectopic signal generators (“ectopic nodes”) because incoming APs stress Na+/K+gradients, thereby altering spike thresholds. Comparable changes could contribute to acquired sodium channelopathies as diverse as epileptic phenomena and to the neuropathic amplification of normally benign sensory inputs. Input spike patterns, we found, propagate with good fidelity through an ectopically firing site only when their frequencies exceed the ectopic frequency. This “propagation window” is a robust phenomenon, occurring despite Gaussian noise, large jitter and the presence of several consecutive ectopic nodes. © 2014, The Author(s).


Trinh A.-K.,McGill University | Gonzalez I.,University of Quintana Roo | Fournier L.,Cegep de lOutaouais | Pelletier R.,Cegep de lOutaouais | And 3 more authors.
Applied Thermal Engineering | Year: 2014

The conversion of solar energy to electricity currently relies primarily on the photovoltaic effect in which photon bombardment of photovoltaic cells drives an electromotive force within the material. Alternatively, recent studies have investigated the potential of converting solar radiation to electricity by way of the Seebeck effect in which charge carrier mobility is generated by an asymmetric thermal differential. The present study builds upon these latest advancements in the state-of-the-art of thermoelectric system management by combining solar evacuated tube technology with commercially available Bismuth Telluride semiconductor modules. The target heat source is solar radiation and the target heat sink is thermal convection into the ambient air relying on wind aided forced convection. These sources of energy are reproduced in a laboratory controlled environment in order to maintain a thermal dipole across a thermoelectric module. The apparatus is then tested in a natural environment. The novelty of the present work lies in a net thermoelectric power gain for ambient environment applications and an experimental validation of theoretical electrical characteristics relative to a varying electrical load. © 2014 Elsevier Ltd. All rights reserved.


Lesage F.J.,Cegep de lOutaouais | Lesage F.J.,McMaster University | Cotton J.S.,McMaster University | Robinson A.J.,McMaster University | Robinson A.J.,Trinity College Dublin
Chemical Engineering Science | Year: 2013

In an effort to lessen the computational expense of bubble growth simulations without compromising its fundamental shape characteristics, an analytical model is developed. It is substantiated using validated numerical results simulating quasi-static adiabatic bubble growth for Bond numbers less than 0.07 in which its characteristic length is the radius of the cavity from which the bubble is issuing. The model's ability to predict shape and size evolution for bubble formations is shown to predict the growth and detachment volume to be in the range from 0.05% for a 0.00137 Bond number to 3% for a 0.06032 Bond number.The model builds upon a recent numerical study which showed that the shape evolution of a quasi-static bubble formation may be idealised as a spherical segment atop a cylindrical neck for low Bond number applications. By incorporating this geometry, the present work's proposed model accounts for bubble shape transformation throughout the bubble growth cycle by including a necking phenomenon in which the bulk of the bubble rises due to an elongating base as it prepares to detach. This is accomplished by introducing: (1) a volume condition which geometrically relates the neck height with the bubble's spherical segment at detachment; (2) a force instability criterion signalling the onset of detachment which relates the size of the bubble to its Bond number and cavity radius; and (3) a neck evolution growth curve. The analytical model ties these relations together with the use of the characteristics of the proposed geometry generating a full description of quasi-static adiabatic bubble growth and detachment for low Bond number formations. The resulting predicted bubble growth characteristics, such as profile, volume, centre of gravity, truncated sphericity and aspect ratio, are presented and discussed with respect to a validated numerical treatment of the problem. •Geometric model for low Bond number applications is presented. © 2013 Elsevier Ltd.


Lesage F.J.,Cegep de lOutaouais | Page-Potvin N.,École de Technologie Supérieure of Montreal
Energy Conversion and Management | Year: 2013

Recent progress in thermoelectric power production using Bismuth Telluride Bi2Te3 semiconductor modules has revealed the potential to effectively convert large volumes of low temperature industrial waste-heat to electricity. In order to render the process more cost effective, greater understanding of the effects of external influences on the module's power output is necessary. Such an understanding would facilitate the design of thermoelectric generators which serve to exploit available waste-heat. To this end, an experimental study is performed on the most adjustable operating parameter on a thermoelectric liquid-to-liquid generator, the electrical load resistance. A test stand apparatus is built applying a temperature gradient on commercially available Bi2Te3 thermoelectric modules by means of an injection and a rejection of heat brought upon by counter current hot and cold liquids. The thermoelectric power production relative to an increasing electrical load is investigated by means of an analysis of experimentally measured results in which the thermal input conditions are varied. The results detail the thermoelectric characteristics of a liquid-to-liquid generator under an increasing electrical load resistance by identifying the optimal electrical load resistance for peak thermoelectric production. A correlation between peak thermoelectric power and thermal input conditions is presented as well as an investigation into the validity of electrical load matching. © 2012 Elsevier Ltd. All rights reserved.


Lesage F.J.,Cegep de lOutaouais | Lesage F.J.,McMaster University | Sempels E.V.,Ecole Polytechnique de Montréal | Lalande-Bertrand N.,École de Technologie Supérieure of Montreal
Energy Conversion and Management | Year: 2013

Thermoelectric power production has many potential applications that range from microelectronics heat management to large scale industrial waste-heat recovery. A low thermoelectric conversion efficiency of the current state of the art prevents wide spread use of thermoelectric modules. The difficulties lie in material conversion efficiency, module design, and thermal system management. The present study investigates thermoelectric power improvement due to heat transfer enhancement at the channel walls of a liquid-to-liquid thermoelectric generator brought upon by flow turbulating inserts. Care is taken to measure the adverse pressure drop due to the presence of flow impeding obstacles in order to measure the net thermoelectric power enhancement relative to an absence of inserts. The results illustrate the power enhancement performance of three different geometric forms fitted into the channels of a thermoelectric generator. Spiral inserts are shown to offer a minimal improvement in thermoelectric power production whereas inserts with protruding panels are shown to be the most effective. Measurements of the thermal enhancement factor which represents the ratio of heat flux into heat flux out of a channel and numerical simulations of the internal flow velocity field attribute the thermal enhancement resulting in the thermoelectric power improvement to thermal and velocity field synergy. © 2013 Elsevier Ltd. All rights reserved.


Amaral C.,Federal University of Uberlandia | Brandao C.,Federal University of Paraiba | Sempels E.V.,Ecole Polytechnique de Montréal | Lesage F.J.,Cegep de lOutaouais | Lesage F.J.,University of Québec
Journal of Power Sources | Year: 2014

Liquid-to-liquid thermoelectric generators are now being considered for the purpose of converting low cost heat to electricity for local energy uses. The importance in investigating their system efficiency lies in the fact that the generator's purpose is to maintain a heat source and a heat sink for its embedded thermoelectric modules. Of particular importance is the generator's ability to maintain an asymmetric thermal field across its embedded modules since this mechanism partially dictates the devices' thermal to electric conversion efficiency. Indeed, since the modules' semiconductor materials' ability to generate an electromotive force is dependent on the quality of the thermal dipole across the material, gains in thermoelectric generator energy conversion efficiency are made possible with thermal system management. In an effort to improve the system conversion efficiency of a liquid-to-liquid thermoelectric generator (TEG), the present work builds upon recent advancements in TEG inner pipe flow optimisation by investigating the thermoelectric power enhancement brought upon by flow impeding panel inserts in a thermoelectric generator's flow channels for fixed thermal input conditions and with respect to varying insert panel densities. The pumping penalty associated with the flow impedance is measured in order to present and to discuss the net thermoelectric power enhancement. © 2014 Elsevier B.V. All rights reserved.


Lesage F.J.,Cegep de lOutaouais | Lesage F.J.,McMaster University | Marois F.,Université de Sherbrooke
International Journal of Heat and Mass Transfer | Year: 2013

When investigating the physical mechanisms responsible for pool boiling heat transfer, individual bubbles are commonly assumed to be spherical. This is done in order to ease the computational expense when solving the Navier-Stokes equations. However, bubbles are observed to deviate from spherical depending on fluid properties, cavity sizes and gravitational field strengths. Since it is bubble detachment volume that dictates ebullition frequency, improvements in detachment size and shape predictions would improve nucleate pool boiling heat and mass transfer models. Recent studies have shown that a numerical treatment of the capillary equation's detachment criterion - which is a result of an interfacial pressure balance analysis - generates profiles corresponding to axis-symmetric quasi-static bubbles for adiabatic conditions. In the present work, this criterion is validated for heat induced bubbles providing the basis for a full analysis of size and shape characteristics of a detaching vapour bubble. A volume detachment correlation is validated for heat induced vapour bubbles and detachment correlations for other size and shape characteristics such as bubble height, width, apex principal radius of curvature, contact angle, and degree of sphericity are developed. Furthermore, a local stress analysis reveals detachment regimes and bubble profile regions. © 2013 Elsevier Ltd. All rights reserved.


Lesage F.J.,Cegep de lOutaouais | Lesage F.J.,McMaster University | Pelletier R.,Cegep de lOutaouais | Fournier L.,Cegep de lOutaouais | Sempels E.V.,Ecole Polytechnique de Montréal
Energy Conversion and Management | Year: 2013

This paper builds upon the recent progress made in the field of thermoelectric energy conversion when using Bismuth Telluride Bi 2Te3 semiconductor modules. These commercially available modules have been the subject of many recent studies in which the common goal is to better understand their thermoelectric behavior when converting a low cost heat source to electricity. The present experimental work investigates the thermopower properties of a single module relative to the electrical load resistance with the use of two experimental apparatuses. The first test stand is built with a precision control of the injection and rejection of heat to and from the module; the second test stand is a novel demonstration of the module's application to thermoelectric solar energy conversion. The thermopower characteristics of the module are measured over a wide range of thermal input conditions. The results highlight the importance in calibrating to an optimal electrical load for peak power output. A normalized thermopower theoretical evolution curve relative to load resistance is presented. Furthermore, a method of thermoelectric recovery of solar radiation is demonstrated using laboratory controlled working conditions. © 2013 Elsevier Ltd. All rights reserved.


PubMed | Cegep de lOutaouais
Type: Journal Article | Journal: Journal of computational neuroscience | Year: 2014

Neural tissue injuries render voltage-gated Na+ channels (Nav) leaky, thereby altering excitability, disrupting propagation and causing neuropathic pain related ectopic activity. In both recombinant systems and native excitable membranes, membrane damage causes the kinetically-coupled activation and inactivation processes of Nav channels to undergo hyperpolarizing shifts. This damage-intensity dependent change, called coupled left-shift (CLS), yields a persistent or subthreshold Nav window conductance. Nodes of Ranvier simulations involving various degrees of mild CLS showed that, as the systems channel/pump fluxes attempt to re-establish ion homeostasis, the CLS elicits hyperexcitability, subthreshold oscillations and neuropathic type action potential (AP) bursts. CLS-induced intermittent propagation failure was studied in simulations of stimulated axons, but pump contributions were ignored, leaving open an important question: does mild-injury (small CLS values, pumps functioning well) render propagation-competent but still quiescent axons vulnerable to further impairments as the system attempts to cope with its normal excitatory inputs? We probe this incipient diffuse axonal injury scenario using a 10-node myelinated axon model. Fully restabilized nodes with mild damage can, we show, become ectopic signal generators (ectopic nodes) because incoming APs stress Na+ / K+ gradients, thereby altering spike thresholds. Comparable changes could contribute to acquired sodium channelopathies as diverse as epileptic phenomena and to the neuropathic amplification of normally benign sensory inputs. Input spike patterns, we found, propagate with good fidelity through an ectopically firing site only when their frequencies exceed the ectopic frequency. This propagation window is a robust phenomenon, occurring despite Gaussian noise, large jitter and the presence of several consecutive ectopic nodes.

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