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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. Source

Amaral C.,Federal University of Uberlandia | Brandao C.,Carleton University | Sempels E.V.,Ecole Polytechnique de Montreal | 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. Source

Dallan B.S.,Carleton University | Dallan B.S.,Federal Technological University of Parana | Schumann J.,Carleton University | Schumann J.,Federal University of Itajuba | And 2 more authors.
Solar Energy | Year: 2015

The current state-of-the art in photovoltaic technology observes that the photoelectric conversion efficiency decreases with increasing material temperature. A proposed solution is to use the thermoelectric effect as a heat pump to manage the excess thermal energy of a photovoltaic cell. Previous investigations into photoelectric-thermoelectric hybrid systems have been either limited to theoretical analyses or experimental set-ups in which external refrigeration pumps are employed or an external heat source - other than photoelectric waste-heat - is used to drive the thermoelectric effect. The present work experimental investigates the viability of converting photoelectric waste-heat into electricity by way of the thermoelectric effect in an effort to better manage a photovoltaic module's conversion efficiency. To this end, the electrical performance of a photovoltaic module and a thermoelectric module which are thermally in series is reported and discussed. © 2015 Elsevier Ltd. Source

Lesage F.J.,Cegep de lOutaouais | Page-Potvin N.,Ecole de Technologie Superieure 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. Source

Lesage F.J.,Cegep de lOutaouais | Lesage F.J.,McMaster University | Sempels E.V.,Ecole Polytechnique de Montreal | Lalande-Bertrand N.,Ecole de Technologie Superieure 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. Source

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