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Currently, in the typical internal combustion engine, approximately one third of fossil fuel combustion by-product is wasted heat. In the continued effort to improve fuel economy, one area that is being researched today is the harvesting of wasted energy to increase vehicle efficiency. This paper will address how heat emitted by exhaust systems can be captured and used to increase vehicle efficiency. Overall we will compare energy content in the exhaust manifold and exhaust underfloor mid-vehicle position, where potential exhaust heat exchanger concepts can reside. These heat exchanger concepts are designed primarily to capture heat from these locations and transfer the energy for increased passenger heating and comfort during cold conditions and/or supplement other improvements in power train efficiencies. An analysis of the energy exchange to the heated fluid is compared in the exhaust manifold and underfloor position respectively.

Moving the catalytic converter closer to the engine reduces its light-off time. However, temperature and pulsating flow have a stronger impact on a close-coupled catalytic converter than an under-floor. For close-coupled architecture, manifold design may play a major role by affecting flow distribution. Consequently, emission performance and durability of thin-wall substrates can be affected. The study being carried out aims at highlighting the impact of manifold design on flow distribution focusing on different manifold configurations. Flow distribution results in hot wire probe measurements. Temperature measurements support the results. Experiments are finally confronted with CFD predictions. The results obtained give trends to design both close-coupled catalytic converter and manifold for better emission performance and resistance to erosion.