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- DAWODY, JAZAER, 1959, et al.
(author)
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E4-Mistra, a research program for the development of an energy efficient low emission exhaust aftertreatment system for heavy duty vehicles
- 2012
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In: World Renewable Energy Forum, WREF 2012, Including World Renewable Energy Congress XII and Colorado Renewable Energy Society (CRES) Annual Conference. - : American Solar Energy Society. - 9781622760923 ; , s. 4530-4536
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Conference paper (peer-reviewed)abstract
- This paper presents a unique system approach applied in a joint academic - industrial research program, E4 Mistra, to reach the goals of energy efficiency and low emissions exhaust aftertreatment system for heavy duty vehicles. The high energy efficiency is achieved by heat recuperation, on-board hydrogen production for use in both an auxiliary power unit and for NOx reduction and by finding new solutions for making the after-treatment system active at low exhaust temperatures. To reach low particulate emissions a mechanical filter using a sintered metal filter is developed. Low NOx emissions are achieved by an efficient NOx reduction catalyst. The system is based on four technological advances: Thermoelectric material s for heat recuperation, catalytic reduction of NOx over innovative catalyst substrates using hydrocarbons from the fuel and H2 from a high efficiency fuel reformer, and particulate filtration over a porous metal filter.
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| 2. |
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| 3. |
- DAWODY, JAZAER, 1959, et al.
(author)
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An integrated system for energy-efficient exhaust aftertreatment for heavy-duty vehicles
- 2015
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In: Renewable Energy in the Service of Mankind. - Cham : Springer International Publishing. - 9783319177779 - 9783319177762 ; 1, s. 133-143
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Book chapter (other academic/artistic)abstract
- © Springer International Publishing Switzerland 2015. This chapter presents a unique system approach applied in a joint academic- industrial research programme, E4 Mistra, to attain the goals of high energy efficiency and low emissions in an exhaust aftertreatment system for heavy-duty vehicles. The high energy efficiency is achieved by heat recuperation, onboard hydrogen production for NOx reduction, and by finding new solutions for making the aftertreatment system active at low exhaust temperatures. To reach low particulate emissions, a mechanical filter using a sintered metal powder is developed and coated with catalytic material to improve the soot oxidation efficiency. Low NOx emissions are achieved by an efficient NOx reduction catalyst. The integrated E4 Mistra system comprises four technological advances: thermoelectric (TE) materials for heat recuperation, catalytic reduction of NOx over innovative catalyst substrates using either the onboard diesel or biodiesel, H2 from a high-efficiency fuel reformer, and particulate filtration over a porous metal filter. The TE materials are used in a TE generator (TEG) which converts thermal energy into electricity. The TEG is used to recuperate heat from the exhaust-gas recirculation (EGR) circuit of heavy-duty trucks and is expected to generate ~1 kW electric power from 20 kW heat in the exhaust gas. The TEG is integrated in a plate heat exchanger (HEX) designed particularly for this application. Apart from the knowledge and experiences in TEG and heat exchange technologies, a thorough fluid dynamics and TE analysis are performed in this project to understand the governing processes and optimize the system accordingly. The components of the E4 Mistra system are explained in the chapter in addition to test results, which show the system's capacity for H2 production, NOx conversion, particulate matter filtration and soot oxidation, and finally electric power generation via heat recuperation from the exhaust gas using the developed TEG-HEX system.
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| 4. |
- Andersson, Ronnie, 1975, et al.
(author)
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Simulation of thermoelectric generators
- 2013
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In: Energimyndighetens konferens:Energirelaterad fordonsforskning.
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Conference paper (other academic/artistic)
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| 5. |
- Högblom, Olle, 1983, et al.
(author)
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A simulation framework for prediction of thermoelectric generator system performance
- 2016
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In: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 180, s. 472-482
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Journal article (peer-reviewed)abstract
- This paper presents a novel framework for characterization and simulation of thermoelectric generator systems that allows accurate and efficient prediction of electric and thermal performance at steady state conditions. The simulation framework relies on regression analysis of single thermoelectric modules including voltage, current, temperatures and heat flow. A physical description of the main phenomena is included in models and enables accurate prediction of module performance over large ranges in temperature and current. Moreover it allows a system of modules electrically connected to be analyzed and used together with fluid dynamics simulations. When used in conjunction with CFD analysis it allows efficient modeling of electrical and thermal performance by simultaneous solution of the coupled equations for energy transport and thermoelectric power generation. This efficiency comes from the fact the modeling does not require full resolution as first principle simulations does. Therefore it solves the scale separation problem and allows multiphysics simulation with just a minor increase in computational power. Experimental validation on a system consisting of electrically connected modules shows excellent prediction of heat flow as well as current and voltage. Validation confirms the simulation framework allows extrapolation outside the measured operating range used when developing the models. Even under highly non-ideal conditions with reversed current, i.e. when modules operate as Peltier coolers rather than generators, very reliable predictions are obtained. Results show the simulation framework captures the main physics and allows efficient and reliable predictions. The models allow physial separation of heat conduction, Peltier, Joule and Seebeck effects and the different phenomena are studied and discussed in detail for various thermal loads and electrical configurations.
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| 6. |
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| 7. |
- Högblom, Olle, 1983, et al.
(author)
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Analysis of Thermoelectric Generator Performance by Use of Simulations and Experiments
- 2014
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In: Journal of Electronic Materials. - : Springer Science and Business Media LLC. - 1543-186X .- 0361-5235. ; 43:6, s. 2247-2254
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Journal article (peer-reviewed)abstract
- A method that enables accurate determination of contact resistances in thermoelectric generators and which gives detailed insight into how these reduce module performance is presented in this paper. To understand the importance taking thermal and electrical contact resistances into account in analysis of thermoelectric generators, full-scale modules were studied. Contact resistances were determined by means of non-linear regression analysis on the basis of results from 3D finite element simulations and experiments in a setup in which heat flow, voltage, and current were measured. Statistical evaluation showed that the model and the identified contact resistances enabled excellent prediction of performance over the entire range of operating conditions. It was shown that if contact resistances were not included in the analysis the simulations significantly over-predicted both heat flow and electric power output, and it was concluded that contact resistance should always be included in module simulations. The method presented in this paper gives detailed insight into how thermoelectric modules perform in general, and also enables prediction of potential improvement in module performance by reduction of contact resistances.
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| 8. |
- Högblom, Olle, 1983, et al.
(author)
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CFD Modeling of Thermoelectric Generators in Automotive EGR-coolers
- 2012
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In: AIP Conference Proceedings. - : AIP. - 1551-7616 .- 0094-243X. ; 1449, s. 497-500
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Conference paper (peer-reviewed)abstract
- A large amount of the waste heat in the exhaust gases from diesel engines is removed in the exhaust gas recirculation (EGR) cooler. Introducing a thermoelectric generator (TEG) in an EGR cooler requires a completely new design of the heat exchanger. To accomplish that a model of the TEG-EGR system is required. In this work, a transient 3D CFD model for simulation of gas flow, heat transfer and power generation has been developed. This model allows critical design parameters in the TEG-EGR to be identified and design requirements for the systems to be specified. Besides the prediction of Seebeck, Peltier, Thomson and Joule effects, the simulations also give detailed insight to the temperature gradients in the gas-phase and inside the thermoelectric (TE) elements. The model is a very valuable tool to identify bottlenecks, improve design, select optimal TE materials and operating conditions. The results show that the greatest heat transfer resistance is located in the gas phase and it is critical to reduce this in order to achieve a large temperature difference over the thermoelectric elements without compromising on the maximum allowable pressure drop in the system. Further results from an investigation of the thermoelectric performance during a vehicle test cycle is presented.
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| 9. |
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| 10. |
- Högblom, Olle, 1983
(author)
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Design of Thermoelectric Generators for Automotive EGR Applications
- 2014
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Licentiate thesis (other academic/artistic)abstract
- Rising energy prices and greater environmental awareness along with stringent emissions legislation in the automotive industry make it possible to introduce techniques in the aftertreatment system that have previously been unprofitable. One such technique, studied in this work, is heat recovery in the exhaust gas recirculation (EGR) cooler using thermoelectric generators (TEG). CFD and thermoelectric simulations are supported with measurements in order to build models that describe the phenomena in a correct manner.Models describing thermoelectric effects, i.e., the Seebeck, Peltier and Thomson effects, together with Joule heating and Fourier conduction, are well known and describe the phenomena satisfactorily when using temperature-dependent material data. A thermoelectric module contains interfaces between different materials and these are never in perfect contact. Consequently, at material junctions, non-ideal contacts will lower the thermoelectric performance. How large these thermal and electrical contact resistances are is not possible to determine analytically since they depend on several parameters that are dependent on the different materials and process parameters, as well as on contact pressure over the junctions. A method for determining contact resistances that combines measurements of commercial modules and simulations is developed and is shown to predict resistances with excellent results, even for geometrically different modules. Furthermore, measurements and simulations on different levels are performed, from detailed studies of a single thermocouple to a full scale study of a thermoelectric heat exchanger prototype. It is shown that the greatest heat transfer resistance is located on the gas side, and it is of great importance to improve the heat transfer in the gas to achieve good overall efficiency. At the same time, it is also of great importance to maintain a low pressure drop in the exhaust gas flow. Consequently, when integrating TEG in EGR coolers, for heat recuperation, it is also important to focus on the design of the heat exchanger to achieve high efficiency, and not only focus on developing new thermoelectric materials and reducing contact resistances. It is concluded that thermoelectric simulations combined with CFD allow fast and inexpensive concept evaluations, and different potential TEG designs can be evaluated and compared with high accuracy.
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