**5. Conclusions**

Experimental exhaust data obtained for most common light-duty diesel engines was used to construct a 3D model. A complete methodology to build 3D CFD exhaust models is presented, including how to estimate main parameters needed and numerical approaches. A 2D axi-symmetrical complementary model was shown to be useful to overcome the necessity of chemical parameters fitted to a specific model of catalytic converter.

A computational model incorporating these findings will lead to accurate and faster numerical calculations of analysis of recoverable energy in exhaust systems. This will allow more designs to be explored in a given time.

It has been pointed out that the particular nature of the exhaust flow leaving catalytic converters has to be taken into account for energy-harvesting calculations, since the end of after-treatment systems is the indicated position to place energy recovery devices.

Furthermore, temperature losses caused by placing the recovery device distant from the DOC were evaluated. This information can be used in the evaluation process of the position of a recovery device in an automotive exhaust system. Since temperature falls promptly, it is advised to place the device as close as possible.

In works regarding simulations of recovery devices, if not enough experimental information is available, it is encouraged to include upstream elements of the exhaust that could alter the flow significantly in order to better predict their performance when installed in vehicles.

**Acknowledgments:** Authors wish to thank the financial support provided by the Spanish Ministry of Economy and Competitiveness to the project POWER Ref. ENE2014-57043-R and Universidad de Castilla—la Mancha for the pre-doctoral funding [2015/4062]. Authors also wish to thank the technical support provided by NISSAN Iberica Co. and CMT-Motores Térmicos Institute at Universitat Politécnica de Valencia.

**Author Contributions:** Pablo Fernández-Yáñez developed the model; Octavio Armas directed and supervised all the work done; Arántzazu Gómez assisted with the experimental work; Antonio Gil assisted with the development of the model.

**Conflicts of Interest:** There is no conflicts of interest.
