{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,23]],"date-time":"2025-10-23T11:06:47Z","timestamp":1761217607890,"version":"build-2065373602"},"reference-count":34,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2013,2,1]],"date-time":"2013-02-01T00:00:00Z","timestamp":1359676800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/3.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Entropy"],"abstract":"<jats:p>In a recent review an optimal thermodynamics and associated new upper bounds have been proposed, but it was only relative to power delivered by engines. In fact, it appears that for systems and processes with more than one utility (mainly mechanical or electrical power), energy conservation (First Law) is limited for representing their efficiency. Consequently, exergy analysis combining the First and Second Law seems essential for optimization of systems or processes situated in their environment. For thermomechanical systems recent papers report on comparisons between energy and exergy analysis and corresponding optimization, but the proposed models mainly use heat transfer conductance modelling, except for internal combustion engine. Here we propose to reconsider direct and inverse configurations of Carnot machines, with two examples. The first example is concerned with \u201cthermofrigo-pump\u201d where the two utilities are hot and cold thermal exergies due to the difference in the temperature level compared to the ambient one. The second one is relative to a \u201ccombined heat and power\u201d (CHP) system. In the two cases, the model is developed based on the Carnot approach, and use of the efficiency-NTU method to characterize the heat exchangers. Obtained results are original thermodynamics optima, that represent exergy upper bounds for these two cases. Extension of the proposed method to other systems and processes is examined, with added technical constraints or not.<\/jats:p>","DOI":"10.3390\/e15020544","type":"journal-article","created":{"date-parts":[[2013,2,1]],"date-time":"2013-02-01T13:27:25Z","timestamp":1359725245000},"page":"544-558","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":7,"title":["Two Examples of Exergy Optimization Regarding the \u201cThermo-Frigopump\u201d and Combined Heat and Power Systems"],"prefix":"10.3390","volume":"15","author":[{"given":"Michel","family":"Feidt","sequence":"first","affiliation":[{"name":"Laboratoire d'Energ\u00e9tique et de M\u00e9canique Th\u00e9orique et Appliqu\u00e9e (LEMTA), Universit\u00e9 de Lorraine, 2 avenue de la For\u00eat de Haye, 54518 Vandoeuvre, France"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2013,2,1]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"3816","DOI":"10.1016\/j.energy.2010.09.025","article-title":"Optimal sizing of residential gas engine cogeneration system for power interchange operation from energy-saving viewpoint","volume":"36","author":"Wakui","year":"2011","journal-title":"Energy"},{"key":"ref_2","unstructured":"Radulescu, M. 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