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The performance of an organic Rankine cycle (ORC) that recovers heat from the exhaust of a heavy-duty diesel engine was simulated. The work was an extension of a prior study that simulated the performance of an experimental ORC system developed and tested at Oak Ridge National laboratory (ORNL). The experimental data were used to set model parameters and validate the results of that simulation. For the current study the model was adapted to consider a 15 liter turbocharged engine versus the original 1.9 liter light-duty automotive turbodiesel studied by ORNL. Exhaust flow rate and temperature data for the heavy-duty engine were obtained from Southwest Research Institute (SwRI) for a range of steady-state engine speeds and loads without EGR. Because of the considerably higher exhaust gas flow rates of the heavy-duty engine, relative to the engine tested by ORNL, a different heat exchanger type was considered in order to keep exhaust pressure drop within practical bounds.

Approximately one-third of the fuel energy consumed by an internal combustion engine flows out the tailpipe as waste heat. Thermoelectric devices are being considered as a means of utilizing some of this waste heat to generate electric power on vehicles. A 1.1-liter volume flat plate heat exchanger was fabricated to study the heat transfer characteristics of a conceptual design for thermoelectric waste heat recovery from diesel exhaust, and used to validate a heat exchanger model. The heat exchanger consisted of an exhaust channel and two coolant channels all having rectangular cross-sections. The experimentally measured heat transfer rates were compared with a finite element heat transfer model to be used both for heat exchanger development and modeling thermoelectric device performance. In both the model and the experiment, alumina paper was used as a surrogate for the thermoelectric materials.