@ARTICLE{10.21494/ISTE.OP.2020.0518, TITLE={Models and irreversibilities of the energy conversion systems}, AUTHOR={Ali Fellah, }, JOURNAL={Entropy: Thermodynamics – Energy – Environment – Economy }, VOLUME={1}, NUMBER={Issue 2}, YEAR={2020}, URL={http://openscience.fr/Models-and-irreversibilities-of-the-energy-conversion-systems}, DOI={10.21494/ISTE.OP.2020.0518}, ISSN={2634-1476}, ABSTRACT={This paper looks at the models used in the studies of energy conversion systems performances. These models are defined in respect of whether or not internal or/and external irreversibility is present. There are four types: the reversible (Carnot), the endoreversible, the exoreversible and the irreversible. This collection presents the characteristics of each model and its possible applications. Particular attention is paid to the endoreversible model which, linked to the system’s hierarchical decomposition method, may well yield very satisfactory results in conceptual and operational studies with easy computation. The irreversible model is always an approached model since not all irreversibility can be modeled in the same formulation; this has forced researchers to provide empirical relationships for this type of model. This collection, along with the examples covered, will be a basis for researchers in which they can have grouped ideas on models for investigating the performance of energy and environmental systems.}}